Merge new upstream LTS 20230802.0

author: Benjamin Barenblat <bbaren@google.com> 2023-09-07 13:16:09 -0400
committer: Benjamin Barenblat <bbaren@google.com> 2023-09-07 13:16:09 -0400
commit: 6fdbff8bbce2a1debdc060df381f39e3dcfb65af (patch)
tree: 71f1ef38477a65d5cce472fc042c90087c2bb351
parent: 8d4a80fe37176b1170d7dce0772dea9584ec3e32 (diff)
parent: 29bf8085f3bf17b84d30e34b3d7ff8248fda404e (diff)
388 files changed, 12262 insertions, 6944 deletions
diff --git a/.github/PULL_REQUEST_TEMPLATE.md b/.github/PULL_REQUEST_TEMPLATE.md
new file mode 100644
index 00000000..ff55e352
--- /dev/null
+++ b/.github/PULL_REQUEST_TEMPLATE.md
@@ -0,0 +1,8 @@
+Thank you for your contribution to Abseil!
+
+Before submitting this PR, please be sure to read our [contributing
+guidelines](https://github.com/abseil/abseil-cpp/blob/master/CONTRIBUTING.md).
+
+If you are a Googler, please also note that it is required that you send us a
+Piper CL instead of using the GitHub pull-request process. The code propagation
+process will deliver the change to GitHub.
diff --git a/CMake/AbseilDll.cmake b/CMake/AbseilDll.cmake
index c4a41e6d..f0d984ae 100644
--- a/CMake/AbseilDll.cmake
+++ b/CMake/AbseilDll.cmake
@@ -26,8 +26,10 @@ set(ABSL_INTERNAL_DLL_FILES
   "base/internal/low_level_alloc.cc"
   "base/internal/low_level_alloc.h"
   "base/internal/low_level_scheduling.h"
+  "base/internal/nullability_impl.h"
   "base/internal/per_thread_tls.h"
   "base/internal/prefetch.h"
+  "base/prefetch.h"
   "base/internal/pretty_function.h"
   "base/internal/raw_logging.cc"
   "base/internal/raw_logging.h"
@@ -55,6 +57,7 @@ set(ABSL_INTERNAL_DLL_FILES
   "base/log_severity.cc"
   "base/log_severity.h"
   "base/macros.h"
+  "base/nullability.h"
   "base/optimization.h"
   "base/options.h"
   "base/policy_checks.h"
@@ -361,14 +364,26 @@ set(ABSL_INTERNAL_DLL_FILES
   "synchronization/internal/create_thread_identity.cc"
   "synchronization/internal/create_thread_identity.h"
   "synchronization/internal/futex.h"
+  "synchronization/internal/futex_waiter.h"
+  "synchronization/internal/futex_waiter.cc"
   "synchronization/internal/graphcycles.cc"
   "synchronization/internal/graphcycles.h"
   "synchronization/internal/kernel_timeout.h"
+  "synchronization/internal/kernel_timeout.cc"
   "synchronization/internal/per_thread_sem.cc"
   "synchronization/internal/per_thread_sem.h"
+  "synchronization/internal/pthread_waiter.h"
+  "synchronization/internal/pthread_waiter.cc"
+  "synchronization/internal/sem_waiter.h"
+  "synchronization/internal/sem_waiter.cc"
+  "synchronization/internal/stdcpp_waiter.h"
+  "synchronization/internal/stdcpp_waiter.cc"
   "synchronization/internal/thread_pool.h"
-  "synchronization/internal/waiter.cc"
   "synchronization/internal/waiter.h"
+  "synchronization/internal/waiter_base.h"
+  "synchronization/internal/waiter_base.cc"
+  "synchronization/internal/win32_waiter.h"
+  "synchronization/internal/win32_waiter.cc"
   "time/civil_time.cc"
   "time/civil_time.h"
   "time/clock.cc"
@@ -417,6 +432,7 @@ set(ABSL_INTERNAL_DLL_FILES
   "types/span.h"
   "types/internal/span.h"
   "types/variant.h"
+  "utility/internal/if_constexpr.h"
   "utility/utility.h"
   "debugging/leak_check.cc"
 )
@@ -448,8 +464,14 @@ set(ABSL_INTERNAL_DLL_TARGETS
   "container_common"
   "container_memory"
   "cord"
+  "cord_internal"
+  "cordz_functions"
+  "cordz_handle"
+  "cordz_info"
+  "cordz_sample_token"
   "core_headers"
   "counting_allocator"
+  "crc_cord_state"
   "crc_cpu_detect"
   "crc_internal"
   "crc32c"
@@ -504,6 +526,7 @@ set(ABSL_INTERNAL_DLL_TARGETS
   "log_internal_structured"
   "log_severity"
   "log_structured"
+  "low_level_hash"
   "malloc_internal"
   "memory"
   "meta"
@@ -555,8 +578,10 @@ set(ABSL_INTERNAL_DLL_TARGETS
   "stack_consumption"
   "stacktrace"
   "status"
+  "statusor"
   "str_format"
   "str_format_internal"
+  "strerror"
   "strings"
   "strings_internal"
   "symbolize"
@@ -575,6 +600,10 @@ set(ABSL_INTERNAL_TEST_DLL_FILES
   "hash/hash_testing.h"
   "log/scoped_mock_log.cc"
   "log/scoped_mock_log.h"
+  "random/internal/chi_square.cc"
+  "random/internal/chi_square.h"
+  "random/internal/distribution_test_util.cc"
+  "random/internal/distribution_test_util.h"
   "random/internal/mock_helpers.h"
   "random/internal/mock_overload_set.h"
   "random/mocking_bit_gen.h"
@@ -588,18 +617,11 @@ set(ABSL_INTERNAL_TEST_DLL_TARGETS
   "cordz_test_helpers"
   "hash_testing"
   "random_mocking_bit_gen"
+  "random_internal_distribution_test_util"
   "random_internal_mock_overload_set"
   "scoped_mock_log"
 )
 
-function(_absl_target_compile_features_if_available TARGET TYPE FEATURE)
-  if(FEATURE IN_LIST CMAKE_CXX_COMPILE_FEATURES)
-    target_compile_features(${TARGET} ${TYPE} ${FEATURE})
-  else()
-    message(WARNING "Feature ${FEATURE} is unknown for the CXX compiler")
-  endif()
-endfunction()
-
 include(CheckCXXSourceCompiles)
 
 check_cxx_source_compiles(
@@ -766,7 +788,7 @@ Name: ${_dll}\n\
 Description: Abseil DLL library\n\
 URL: https://abseil.io/\n\
 Version: ${absl_VERSION}\n\
-Libs: -L\${libdir} ${PC_LINKOPTS} $<$<NOT:$<BOOL:${ABSL_CC_LIB_IS_INTERFACE}>>:-l${_dll}>\n\
+Libs: -L\${libdir} $<$<NOT:$<BOOL:${ABSL_CC_LIB_IS_INTERFACE}>>:-l${_dll}> ${PC_LINKOPTS}\n\
 Cflags: -I\${includedir}${PC_CFLAGS}\n")
   INSTALL(FILES "${CMAKE_BINARY_DIR}/lib/pkgconfig/${_dll}.pc"
     DESTINATION "${CMAKE_INSTALL_LIBDIR}/pkgconfig")
@@ -787,18 +809,7 @@ Cflags: -I\${includedir}${PC_CFLAGS}\n")
     # Abseil libraries require C++14 as the current minimum standard. When
     # compiled with C++17 (either because it is the compiler's default or
     # explicitly requested), then Abseil requires C++17.
-    _absl_target_compile_features_if_available(${_NAME} PUBLIC ${ABSL_INTERNAL_CXX_STD_FEATURE})
-  else()
-    # Note: This is legacy (before CMake 3.8) behavior. Setting the
-    # target-level CXX_STANDARD property to ABSL_CXX_STANDARD (which is
-    # initialized by CMAKE_CXX_STANDARD) should have no real effect, since
-    # that is the default value anyway.
-    #
-    # CXX_STANDARD_REQUIRED does guard against the top-level CMake project
-    # not having enabled CMAKE_CXX_STANDARD_REQUIRED (which prevents
-    # "decaying" to an older standard if the requested one isn't available).
-    set_property(TARGET ${_NAME} PROPERTY CXX_STANDARD ${ABSL_CXX_STANDARD})
-    set_property(TARGET ${_NAME} PROPERTY CXX_STANDARD_REQUIRED ON)
+    target_compile_features(${_dll} PUBLIC ${ABSL_INTERNAL_CXX_STD_FEATURE})
   endif()
 
   install(TARGETS ${_dll} EXPORT ${PROJECT_NAME}Targets
@@ -806,4 +817,6 @@ Cflags: -I\${includedir}${PC_CFLAGS}\n")
         LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
         ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR}
   )
+
+  add_library(absl::${_dll} ALIAS ${_dll})
 endfunction()
diff --git a/CMake/AbseilHelpers.cmake b/CMake/AbseilHelpers.cmake
index f452a676..3bd33ce8 100644
--- a/CMake/AbseilHelpers.cmake
+++ b/CMake/AbseilHelpers.cmake
@@ -211,7 +211,7 @@ Description: Abseil ${_NAME} library\n\
 URL: https://abseil.io/\n\
 Version: ${PC_VERSION}\n\
 Requires:${PC_DEPS}\n\
-Libs: -L\${libdir} ${PC_LINKOPTS} $<$<NOT:$<BOOL:${ABSL_CC_LIB_IS_INTERFACE}>>:${LNK_LIB}>\n\
+Libs: -L\${libdir} $<$<NOT:$<BOOL:${ABSL_CC_LIB_IS_INTERFACE}>>:${LNK_LIB}> ${PC_LINKOPTS}\n\
 Cflags: -I\${includedir}${PC_CFLAGS}\n")
     INSTALL(FILES "${CMAKE_BINARY_DIR}/lib/pkgconfig/absl_${_NAME}.pc"
             DESTINATION "${CMAKE_INSTALL_LIBDIR}/pkgconfig")
@@ -289,18 +289,7 @@ Cflags: -I\${includedir}${PC_CFLAGS}\n")
       # Abseil libraries require C++14 as the current minimum standard. When
       # compiled with C++17 (either because it is the compiler's default or
       # explicitly requested), then Abseil requires C++17.
-      _absl_target_compile_features_if_available(${_NAME} PUBLIC ${ABSL_INTERNAL_CXX_STD_FEATURE})
-    else()
-      # Note: This is legacy (before CMake 3.8) behavior. Setting the
-      # target-level CXX_STANDARD property to ABSL_CXX_STANDARD (which is
-      # initialized by CMAKE_CXX_STANDARD) should have no real effect, since
-      # that is the default value anyway.
-      #
-      # CXX_STANDARD_REQUIRED does guard against the top-level CMake project
-      # not having enabled CMAKE_CXX_STANDARD_REQUIRED (which prevents
-      # "decaying" to an older standard if the requested one isn't available).
-      set_property(TARGET ${_NAME} PROPERTY CXX_STANDARD ${ABSL_CXX_STANDARD})
-      set_property(TARGET ${_NAME} PROPERTY CXX_STANDARD_REQUIRED ON)
+      target_compile_features(${_NAME} PUBLIC ${ABSL_INTERNAL_CXX_STD_FEATURE})
     endif()
 
     # When being installed, we lose the absl_ prefix.  We want to put it back
@@ -309,7 +298,7 @@ Cflags: -I\${includedir}${PC_CFLAGS}\n")
     if(ABSL_ENABLE_INSTALL)
       set_target_properties(${_NAME} PROPERTIES
         OUTPUT_NAME "absl_${_NAME}"
-        SOVERSION "2301.0.0"
+        SOVERSION "2308.0.0"
       )
     endif()
   else()
@@ -337,10 +326,7 @@ Cflags: -I\${includedir}${PC_CFLAGS}\n")
       # Abseil libraries require C++14 as the current minimum standard.
       # Top-level application CMake projects should ensure a consistent C++
       # standard for all compiled sources by setting CMAKE_CXX_STANDARD.
-      _absl_target_compile_features_if_available(${_NAME} INTERFACE ${ABSL_INTERNAL_CXX_STD_FEATURE})
-
-      # (INTERFACE libraries can't have the CXX_STANDARD property set, so there
-      # is no legacy behavior else case).
+      target_compile_features(${_NAME} INTERFACE ${ABSL_INTERNAL_CXX_STD_FEATURE})
     endif()
   endif()
 
@@ -427,6 +413,10 @@ function(absl_cc_test)
       DEPS ${ABSL_CC_TEST_DEPS}
       OUTPUT ABSL_CC_TEST_DEPS
     )
+    absl_internal_dll_targets(
+      DEPS ${ABSL_CC_TEST_LINKOPTS}
+      OUTPUT ABSL_CC_TEST_LINKOPTS
+    )
   else()
     target_compile_definitions(${_NAME}
       PUBLIC
@@ -448,18 +438,7 @@ function(absl_cc_test)
     # Abseil libraries require C++14 as the current minimum standard.
     # Top-level application CMake projects should ensure a consistent C++
     # standard for all compiled sources by setting CMAKE_CXX_STANDARD.
-    _absl_target_compile_features_if_available(${_NAME} PUBLIC ${ABSL_INTERNAL_CXX_STD_FEATURE})
-  else()
-    # Note: This is legacy (before CMake 3.8) behavior. Setting the
-    # target-level CXX_STANDARD property to ABSL_CXX_STANDARD (which is
-    # initialized by CMAKE_CXX_STANDARD) should have no real effect, since
-    # that is the default value anyway.
-    #
-    # CXX_STANDARD_REQUIRED does guard against the top-level CMake project
-    # not having enabled CMAKE_CXX_STANDARD_REQUIRED (which prevents
-    # "decaying" to an older standard if the requested one isn't available).
-    set_property(TARGET ${_NAME} PROPERTY CXX_STANDARD ${ABSL_CXX_STANDARD})
-    set_property(TARGET ${_NAME} PROPERTY CXX_STANDARD_REQUIRED ON)
+    target_compile_features(${_NAME} PUBLIC ${ABSL_INTERNAL_CXX_STD_FEATURE})
   endif()
 
   add_test(NAME ${_NAME} COMMAND ${_NAME})
diff --git a/CMake/README.md b/CMake/README.md
index 19fb327c..c7ddee64 100644
--- a/CMake/README.md
+++ b/CMake/README.md
@@ -170,7 +170,7 @@ And finally install:
 cmake --build /temporary/build/abseil-cpp --target install
 ```
 
-# CMake Option Synposis
+# CMake Option Synopsis
 
 ## Enable Standard CMake Installation
 
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 3a9e521f..eef66267 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -48,7 +48,12 @@ if (POLICY CMP0067)
   cmake_policy(SET CMP0067 NEW)
 endif (POLICY CMP0067)
 
-project(absl LANGUAGES CXX VERSION 20230125)
+# Allow the user to specify the CMAKE_MSVC_DEBUG_INFORMATION_FORMAT
+if (POLICY CMP0141)
+  cmake_policy(SET CMP0141 NEW)
+endif (POLICY CMP0141)
+
+project(absl LANGUAGES CXX VERSION 20230802)
 include(CTest)
 
 # Output directory is correct by default for most build setups. However, when
@@ -68,7 +73,7 @@ endif()
 option(ABSL_PROPAGATE_CXX_STD
   "Use CMake C++ standard meta features (e.g. cxx_std_14) that propagate to targets that link to Abseil"
   OFF)  # TODO: Default to ON for CMake 3.8 and greater.
-if((${CMAKE_VERSION} VERSION_GREATER_EQUAL 3.8) AND (NOT ABSL_PROPAGATE_CXX_STD))
+if(NOT ABSL_PROPAGATE_CXX_STD)
   message(WARNING "A future Abseil release will default ABSL_PROPAGATE_CXX_STD to ON for CMake 3.8 and up. We recommend enabling this option to ensure your project still builds correctly.")
 endif()
 
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 9dadae93..a87254c5 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -75,9 +75,9 @@ will be expected to conform to the style outlined
 
 ## Guidelines for Pull Requests
 
-*   If you are a Googler, it is preferable to first create an internal CL and
-    have it reviewed and submitted. The code propagation process will deliver
-    the change to GitHub.
+*   If you are a Googler, it is required that you send us a Piper CL instead of
+    using the GitHub pull-request process. The code propagation process will
+    deliver the change to GitHub.
 
 *   Create **small PRs** that are narrowly focused on **addressing a single
     concern**. We often receive PRs that are trying to fix several things at a
diff --git a/README.md b/README.md
index 0816692e..f834fcde 100644
--- a/README.md
+++ b/README.md
@@ -91,9 +91,6 @@ Abseil contains the following C++ library components:
 * [`hash`](absl/hash/)
   <br /> The `hash` library contains the hashing framework and default hash
   functor implementations for hashable types in Abseil.
-* [`iterator`](absl/iterator/)
-  <br /> The `iterator` library contains utilities for augmenting ranges in
-  range-based for loops.
 * [`log`](absl/log/)
   <br /> The `log` library contains `LOG` and `CHECK` macros and facilities
   for writing logged messages out to disk, `stderr`, or user-extensible
diff --git a/UPGRADES.md b/UPGRADES.md
index 35599d08..3cac141d 100644
--- a/UPGRADES.md
+++ b/UPGRADES.md
@@ -1,6 +1,6 @@
 # C++ Upgrade Tools
 
-Abseil may occassionally release API-breaking changes. As noted in our
+Abseil may occasionally release API-breaking changes. As noted in our
 [Compatibility Guidelines][compatibility-guide], we will aim to provide a tool
 to do the work of effecting such API-breaking changes, when absolutely
 necessary.
diff --git a/WORKSPACE b/WORKSPACE
index 4069ecc7..fdb615f3 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -20,43 +20,41 @@ load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
 
 # GoogleTest/GoogleMock framework. Used by most unit-tests.
 http_archive(
-    name = "com_google_googletest",  # 2023-01-05T19:15:29Z
-    sha256 = "ffa17fbc5953900994e2deec164bb8949879ea09b411e07f215bfbb1f87f4632",
-    strip_prefix = "googletest-1.13.0",
+    name = "com_google_googletest",  # 2023-08-02T16:45:10Z
+    sha256 = "1f357c27ca988c3f7c6b4bf68a9395005ac6761f034046e9dde0896e3aba00e4",
+    strip_prefix = "googletest-1.14.0",
     # Keep this URL in sync with ABSL_GOOGLETEST_COMMIT in ci/cmake_common.sh.
-    urls = ["https://github.com/google/googletest/archive/refs/tags/v1.13.0.zip"],
+    urls = ["https://github.com/google/googletest/archive/refs/tags/v1.14.0.zip"],
 )
 
 # RE2 (the regular expression library used by GoogleTest)
-# Note this must use a commit from the `abseil` branch of the RE2 project.
-# https://github.com/google/re2/tree/abseil
 http_archive(
-    name = "com_googlesource_code_re2",
-    sha256 = "0a890c2aa0bb05b2ce906a15efb520d0f5ad4c7d37b8db959c43772802991887",
-    strip_prefix = "re2-a427f10b9fb4622dd6d8643032600aa1b50fbd12",
-    urls = ["https://github.com/google/re2/archive/a427f10b9fb4622dd6d8643032600aa1b50fbd12.zip"],  # 2022-06-09
+    name = "com_googlesource_code_re2",  # 2023-03-17T11:36:51Z
+    sha256 = "cb8b5312a65f2598954545a76e8bce913f35fbb3a21a5c88797a4448e9f9b9d9",
+    strip_prefix = "re2-578843a516fd1da7084ae46209a75f3613b6065e",
+    urls = ["https://github.com/google/re2/archive/578843a516fd1da7084ae46209a75f3613b6065e.zip"],
 )
 
 # Google benchmark.
 http_archive(
-    name = "com_github_google_benchmark",  # 2023-01-10T16:48:17Z
-    sha256 = "ede6830512f21490eeea1f238f083702eb178890820c14451c1c3d69fd375b19",
-    strip_prefix = "benchmark-a3235d7b69c84e8c9ff8722a22b8ac5e1bc716a6",
-    urls = ["https://github.com/google/benchmark/archive/a3235d7b69c84e8c9ff8722a22b8ac5e1bc716a6.zip"],
+    name = "com_github_google_benchmark",  # 2023-08-01T07:47:09Z
+    sha256 = "db1e39ee71dc38aa7e57ed007f2c8b3bb59e13656435974781a9dc0617d75cc9",
+    strip_prefix = "benchmark-02a354f3f323ae8256948e1dc77ddcb1dfc297da",
+    urls = ["https://github.com/google/benchmark/archive/02a354f3f323ae8256948e1dc77ddcb1dfc297da.zip"],
 )
 
 # Bazel Skylib.
 http_archive(
-    name = "bazel_skylib",  # 2022-11-16T18:29:32Z
-    sha256 = "a22290c26d29d3ecca286466f7f295ac6cbe32c0a9da3a91176a90e0725e3649",
-    strip_prefix = "bazel-skylib-5bfcb1a684550626ce138fe0fe8f5f702b3764c3",
-    urls = ["https://github.com/bazelbuild/bazel-skylib/archive/5bfcb1a684550626ce138fe0fe8f5f702b3764c3.zip"],
+    name = "bazel_skylib",  # 2023-05-31T19:24:07Z
+    sha256 = "08c0386f45821ce246bbbf77503c973246ed6ee5c3463e41efc197fa9bc3a7f4",
+    strip_prefix = "bazel-skylib-288731ef9f7f688932bd50e704a91a45ec185f9b",
+    urls = ["https://github.com/bazelbuild/bazel-skylib/archive/288731ef9f7f688932bd50e704a91a45ec185f9b.zip"],
 )
 
 # Bazel platform rules.
 http_archive(
-    name = "platforms",  # 2022-11-09T19:18:22Z
-    sha256 = "b4a3b45dc4202e2b3e34e3bc49d2b5b37295fc23ea58d88fb9e01f3642ad9b55",
-    strip_prefix = "platforms-3fbc687756043fb58a407c2ea8c944bc2fe1d922",
-    urls = ["https://github.com/bazelbuild/platforms/archive/3fbc687756043fb58a407c2ea8c944bc2fe1d922.zip"],
+    name = "platforms",  # 2023-07-28T19:44:27Z
+    sha256 = "40eb313613ff00a5c03eed20aba58890046f4d38dec7344f00bb9a8867853526",
+    strip_prefix = "platforms-4ad40ef271da8176d4fc0194d2089b8a76e19d7b",
+    urls = ["https://github.com/bazelbuild/platforms/archive/4ad40ef271da8176d4fc0194d2089b8a76e19d7b.zip"],
 )
diff --git a/absl/BUILD.bazel b/absl/BUILD.bazel
index 29963ccc..253c0aef 100644
--- a/absl/BUILD.bazel
+++ b/absl/BUILD.bazel
@@ -12,6 +12,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+#
 
 load("@bazel_skylib//lib:selects.bzl", "selects")
 
@@ -36,6 +37,22 @@ config_setting(
 )
 
 config_setting(
+    name = "mingw_unspecified_compiler",
+    flag_values = {
+        "@bazel_tools//tools/cpp:compiler": "mingw",
+    },
+    visibility = [":__subpackages__"],
+)
+
+config_setting(
+    name = "mingw-gcc_compiler",
+    flag_values = {
+        "@bazel_tools//tools/cpp:compiler": "mingw-gcc",
+    },
+    visibility = [":__subpackages__"],
+)
+
+config_setting(
     name = "msvc_compiler",
     flag_values = {
         "@bazel_tools//tools/cpp:compiler": "msvc-cl",
@@ -123,3 +140,12 @@ config_setting(
     },
     visibility = [":__subpackages__"],
 )
+
+selects.config_setting_group(
+    name = "mingw_compiler",
+    match_any = [
+        ":mingw_unspecified_compiler",
+        ":mingw-gcc_compiler",
+    ],
+    visibility = [":__subpackages__"],
+)
diff --git a/absl/algorithm/container.h b/absl/algorithm/container.h
index c7782d4f..679e0267 100644
--- a/absl/algorithm/container.h
+++ b/absl/algorithm/container.h
@@ -1131,7 +1131,7 @@ c_equal_range(Sequence& sequence, const T& value, LessThan&& comp) {
 // to test if any element in the sorted container contains a value equivalent to
 // 'value'.
 template <typename Sequence, typename T>
-bool c_binary_search(Sequence&& sequence, const T& value) {
+bool c_binary_search(const Sequence& sequence, const T& value) {
   return std::binary_search(container_algorithm_internal::c_begin(sequence),
                             container_algorithm_internal::c_end(sequence),
                             value);
@@ -1140,7 +1140,8 @@ bool c_binary_search(Sequence&& sequence, const T& value) {
 // Overload of c_binary_search() for performing a `comp` comparison other than
 // the default `operator<`.
 template <typename Sequence, typename T, typename LessThan>
-bool c_binary_search(Sequence&& sequence, const T& value, LessThan&& comp) {
+bool c_binary_search(const Sequence& sequence, const T& value,
+                     LessThan&& comp) {
   return std::binary_search(container_algorithm_internal::c_begin(sequence),
                             container_algorithm_internal::c_end(sequence),
                             value, std::forward<LessThan>(comp));
diff --git a/absl/base/BUILD.bazel b/absl/base/BUILD.bazel
index ded26d6a..fb008db3 100644
--- a/absl/base/BUILD.bazel
+++ b/absl/base/BUILD.bazel
@@ -63,6 +63,18 @@ cc_library(
 )
 
 cc_library(
+    name = "nullability",
+    srcs = ["internal/nullability_impl.h"],
+    hdrs = ["nullability.h"],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":core_headers",
+        "//absl/meta:type_traits",
+    ],
+)
+
+cc_library(
     name = "raw_logging_internal",
     srcs = ["internal/raw_logging.cc"],
     hdrs = ["internal/raw_logging.h"],
@@ -246,6 +258,10 @@ cc_library(
         "//absl:clang-cl_compiler": [
             "-DEFAULTLIB:advapi32.lib",
         ],
+        "//absl:mingw_compiler": [
+            "-DEFAULTLIB:advapi32.lib",
+            "-ladvapi32",
+        ],
         "//absl:wasm": [],
         "//conditions:default": ["-pthread"],
     }) + ABSL_DEFAULT_LINKOPTS,
@@ -549,6 +565,16 @@ cc_test(
 )
 
 cc_test(
+    name = "nullability_test",
+    srcs = ["nullability_test.cc"],
+    deps = [
+        ":core_headers",
+        ":nullability",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_test(
     name = "raw_logging_test",
     srcs = ["raw_logging_test.cc"],
     copts = ABSL_TEST_COPTS,
@@ -732,21 +758,25 @@ cc_test(
 
 cc_library(
     name = "prefetch",
-    hdrs = ["internal/prefetch.h"],
+    hdrs = [
+        "internal/prefetch.h",
+        "prefetch.h",
+    ],
     copts = ABSL_DEFAULT_COPTS,
     linkopts = ABSL_DEFAULT_LINKOPTS,
-    visibility = [
-        "//absl:__subpackages__",
-    ],
     deps = [
         ":config",
+        ":core_headers",  # TODO(b/265984188): remove
     ],
 )
 
 cc_test(
     name = "prefetch_test",
     size = "small",
-    srcs = ["internal/prefetch_test.cc"],
+    srcs = [
+        "internal/prefetch_test.cc",
+        "prefetch_test.cc",
+    ],
     copts = ABSL_TEST_COPTS,
     linkopts = ABSL_DEFAULT_LINKOPTS,
     deps = [
diff --git a/absl/base/CMakeLists.txt b/absl/base/CMakeLists.txt
index 26e2b48a..76c4ff1d 100644
--- a/absl/base/CMakeLists.txt
+++ b/absl/base/CMakeLists.txt
@@ -54,6 +54,33 @@ absl_cc_library(
     ${ABSL_DEFAULT_COPTS}
 )
 
+absl_cc_library(
+  NAME
+    nullability
+  HDRS
+    "nullability.h"
+  SRCS
+    "internal/nullability_impl.h"
+  DEPS
+    absl::core_headers
+    absl::type_traits
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+)
+
+absl_cc_test(
+  NAME
+    nullability_test
+  SRCS
+    "nullability_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  DEPS
+    absl::core_headers
+    absl::nullability
+    GTest::gtest_main
+)
+
 # Internal-only target, do not depend on directly.
 absl_cc_library(
   NAME
@@ -645,11 +672,11 @@ absl_cc_test(
     GTest::gtest_main
 )
 
-# Internal-only target, do not depend on directly.
 absl_cc_library(
   NAME
     prefetch
   HDRS
+    "prefetch.h"
     "internal/prefetch.h"
   COPTS
     ${ABSL_DEFAULT_COPTS}
@@ -657,12 +684,14 @@ absl_cc_library(
     ${ABSL_DEFAULT_LINKOPTS}
   DEPS
     absl::config
+    absl::core_headers  # TODO(b/265984188): remove
 )
 
 absl_cc_test(
   NAME
     prefetch_test
   SRCS
+    "prefetch_test.cc"
     "internal/prefetch_test.cc"
   COPTS
     ${ABSL_TEST_COPTS}
diff --git a/absl/base/attributes.h b/absl/base/attributes.h
index b7826e77..a7f279a0 100644
--- a/absl/base/attributes.h
+++ b/absl/base/attributes.h
@@ -211,11 +211,20 @@
 // out of bounds or does other scary things with memory.
 // NOTE: GCC supports AddressSanitizer(asan) since 4.8.
 // https://gcc.gnu.org/gcc-4.8/changes.html
-#if ABSL_HAVE_ATTRIBUTE(no_sanitize_address)
+#if defined(ABSL_HAVE_ADDRESS_SANITIZER) && \
+    ABSL_HAVE_ATTRIBUTE(no_sanitize_address)
 #define ABSL_ATTRIBUTE_NO_SANITIZE_ADDRESS __attribute__((no_sanitize_address))
-#elif defined(_MSC_VER) && _MSC_VER >= 1928
+#elif defined(ABSL_HAVE_ADDRESS_SANITIZER) && defined(_MSC_VER) && \
+    _MSC_VER >= 1928
 // https://docs.microsoft.com/en-us/cpp/cpp/no-sanitize-address
 #define ABSL_ATTRIBUTE_NO_SANITIZE_ADDRESS __declspec(no_sanitize_address)
+#elif defined(ABSL_HAVE_HWADDRESS_SANITIZER) && ABSL_HAVE_ATTRIBUTE(no_sanitize)
+// HWAddressSanitizer is a sanitizer similar to AddressSanitizer, which uses CPU
+// features to detect similar bugs with less CPU and memory overhead.
+// NOTE: GCC supports HWAddressSanitizer(hwasan) since 11.
+// https://gcc.gnu.org/gcc-11/changes.html
+#define ABSL_ATTRIBUTE_NO_SANITIZE_ADDRESS \
+  __attribute__((no_sanitize("hwaddress")))
 #else
 #define ABSL_ATTRIBUTE_NO_SANITIZE_ADDRESS
 #endif
@@ -265,7 +274,7 @@
 //
 // Tells the ControlFlowIntegrity sanitizer to not instrument a given function.
 // See https://clang.llvm.org/docs/ControlFlowIntegrity.html for details.
-#if ABSL_HAVE_ATTRIBUTE(no_sanitize)
+#if ABSL_HAVE_ATTRIBUTE(no_sanitize) && defined(__llvm__)
 #define ABSL_ATTRIBUTE_NO_SANITIZE_CFI __attribute__((no_sanitize("cfi")))
 #else
 #define ABSL_ATTRIBUTE_NO_SANITIZE_CFI
@@ -322,8 +331,8 @@
 // This functionality is supported by GNU linker.
 #ifndef ABSL_ATTRIBUTE_SECTION_VARIABLE
 #ifdef _AIX
-// __attribute__((section(#name))) on AIX is achived by using the `.csect` psudo
-// op which includes an additional integer as part of its syntax indcating
+// __attribute__((section(#name))) on AIX is achieved by using the `.csect`
+// psudo op which includes an additional integer as part of its syntax indcating
 // alignment. If data fall under different alignments then you might get a
 // compilation error indicating a `Section type conflict`.
 #define ABSL_ATTRIBUTE_SECTION_VARIABLE(name)
@@ -676,6 +685,28 @@
 #define ABSL_DEPRECATED(message)
 #endif
 
+// When deprecating Abseil code, it is sometimes necessary to turn off the
+// warning within Abseil, until the deprecated code is actually removed. The
+// deprecated code can be surrounded with these directives to acheive that
+// result.
+//
+// class ABSL_DEPRECATED("Use Bar instead") Foo;
+//
+// ABSL_INTERNAL_DISABLE_DEPRECATED_DECLARATION_WARNING
+// Baz ComputeBazFromFoo(Foo f);
+// ABSL_INTERNAL_RESTORE_DEPRECATED_DECLARATION_WARNING
+#if defined(__GNUC__) || defined(__clang__)
+// Clang also supports these GCC pragmas.
+#define ABSL_INTERNAL_DISABLE_DEPRECATED_DECLARATION_WARNING \
+  _Pragma("GCC diagnostic push")             \
+  _Pragma("GCC diagnostic ignored \"-Wdeprecated-declarations\"")
+#define ABSL_INTERNAL_RESTORE_DEPRECATED_DECLARATION_WARNING \
+  _Pragma("GCC diagnostic pop")
+#else
+#define ABSL_INTERNAL_DISABLE_DEPRECATED_DECLARATION_WARNING
+#define ABSL_INTERNAL_RESTORE_DEPRECATED_DECLARATION_WARNING
+#endif  // defined(__GNUC__) || defined(__clang__)
+
 // ABSL_CONST_INIT
 //
 // A variable declaration annotated with the `ABSL_CONST_INIT` attribute will
@@ -779,4 +810,26 @@
 #define ABSL_ATTRIBUTE_TRIVIAL_ABI
 #endif
 
+// ABSL_ATTRIBUTE_NO_UNIQUE_ADDRESS
+//
+// Indicates a data member can be optimized to occupy no space (if it is empty)
+// and/or its tail padding can be used for other members.
+//
+// For code that is assured to only build with C++20 or later, prefer using
+// the standard attribute `[[no_unique_address]]` directly instead of this
+// macro.
+//
+// https://devblogs.microsoft.com/cppblog/msvc-cpp20-and-the-std-cpp20-switch/#c20-no_unique_address
+// Current versions of MSVC have disabled `[[no_unique_address]]` since it
+// breaks ABI compatibility, but offers `[[msvc::no_unique_address]]` for
+// situations when it can be assured that it is desired. Since Abseil does not
+// claim ABI compatibility in mixed builds, we can offer it unconditionally.
+#if defined(_MSC_VER) && _MSC_VER >= 1929
+#define ABSL_ATTRIBUTE_NO_UNIQUE_ADDRESS [[msvc::no_unique_address]]
+#elif ABSL_HAVE_CPP_ATTRIBUTE(no_unique_address)
+#define ABSL_ATTRIBUTE_NO_UNIQUE_ADDRESS [[no_unique_address]]
+#else
+#define ABSL_ATTRIBUTE_NO_UNIQUE_ADDRESS
+#endif
+
 #endif  // ABSL_BASE_ATTRIBUTES_H_
diff --git a/absl/base/call_once.h b/absl/base/call_once.h
index 96109f53..08436bac 100644
--- a/absl/base/call_once.h
+++ b/absl/base/call_once.h
@@ -123,7 +123,7 @@ class SchedulingHelper {
 
  private:
   base_internal::SchedulingMode mode_;
-  bool guard_result_;
+  bool guard_result_ = false;
 };
 
 // Bit patterns for call_once state machine values.  Internal implementation
diff --git a/absl/base/casts.h b/absl/base/casts.h
index b99adb06..d1958885 100644
--- a/absl/base/casts.h
+++ b/absl/base/casts.h
@@ -149,16 +149,16 @@ using std::bit_cast;
 
 #else  // defined(__cpp_lib_bit_cast) && __cpp_lib_bit_cast >= 201806L
 
-template <typename Dest, typename Source,
-          typename std::enable_if<
-              sizeof(Dest) == sizeof(Source) &&
-                  type_traits_internal::is_trivially_copyable<Source>::value &&
-                  type_traits_internal::is_trivially_copyable<Dest>::value
+template <
+    typename Dest, typename Source,
+    typename std::enable_if<sizeof(Dest) == sizeof(Source) &&
+                                std::is_trivially_copyable<Source>::value &&
+                                std::is_trivially_copyable<Dest>::value
 #if !ABSL_HAVE_BUILTIN(__builtin_bit_cast)
-                  && std::is_default_constructible<Dest>::value
+                                && std::is_default_constructible<Dest>::value
 #endif  // !ABSL_HAVE_BUILTIN(__builtin_bit_cast)
-              ,
-              int>::type = 0>
+                            ,
+                            int>::type = 0>
 #if ABSL_HAVE_BUILTIN(__builtin_bit_cast)
 inline constexpr Dest bit_cast(const Source& source) {
   return __builtin_bit_cast(Dest, source);
diff --git a/absl/base/config.h b/absl/base/config.h
index 05d960b6..1de79930 100644
--- a/absl/base/config.h
+++ b/absl/base/config.h
@@ -111,8 +111,8 @@
 //
 // LTS releases can be obtained from
 // https://github.com/abseil/abseil-cpp/releases.
-#define ABSL_LTS_RELEASE_VERSION 20230125
-#define ABSL_LTS_RELEASE_PATCH_LEVEL 3
+#define ABSL_LTS_RELEASE_VERSION 20230802
+#define ABSL_LTS_RELEASE_PATCH_LEVEL 0
 
 // Helper macro to convert a CPP variable to a string literal.
 #define ABSL_INTERNAL_DO_TOKEN_STR(x) #x
@@ -237,15 +237,8 @@ static_assert(ABSL_INTERNAL_INLINE_NAMESPACE_STR[0] != 'h' ||
 // ABSL_HAVE_STD_IS_TRIVIALLY_DESTRUCTIBLE
 //
 // Checks whether `std::is_trivially_destructible<T>` is supported.
-//
-// Notes: All supported compilers using libc++ support this feature, as does
-// gcc >= 4.8.1 using libstdc++, and Visual Studio.
 #ifdef ABSL_HAVE_STD_IS_TRIVIALLY_DESTRUCTIBLE
 #error ABSL_HAVE_STD_IS_TRIVIALLY_DESTRUCTIBLE cannot be directly set
-#elif defined(_LIBCPP_VERSION) || defined(_MSC_VER) || \
-    (defined(__clang__) && __clang_major__ >= 15) ||   \
-    (!defined(__clang__) && defined(__GLIBCXX__) &&    \
-     ABSL_INTERNAL_HAVE_MIN_GNUC_VERSION(4, 8))
 #define ABSL_HAVE_STD_IS_TRIVIALLY_DESTRUCTIBLE 1
 #endif
 
@@ -253,36 +246,26 @@ static_assert(ABSL_INTERNAL_INLINE_NAMESPACE_STR[0] != 'h' ||
 //
 // Checks whether `std::is_trivially_default_constructible<T>` and
 // `std::is_trivially_copy_constructible<T>` are supported.
+#ifdef ABSL_HAVE_STD_IS_TRIVIALLY_CONSTRUCTIBLE
+#error ABSL_HAVE_STD_IS_TRIVIALLY_CONSTRUCTIBLE cannot be directly set
+#else
+#define ABSL_HAVE_STD_IS_TRIVIALLY_CONSTRUCTIBLE 1
+#endif
 
 // ABSL_HAVE_STD_IS_TRIVIALLY_ASSIGNABLE
 //
 // Checks whether `std::is_trivially_copy_assignable<T>` is supported.
-
-// Notes: Clang with libc++ supports these features, as does gcc >= 7.4 with
-// libstdc++, or gcc >= 8.2 with libc++, and Visual Studio (but not NVCC).
-#if defined(ABSL_HAVE_STD_IS_TRIVIALLY_CONSTRUCTIBLE)
-#error ABSL_HAVE_STD_IS_TRIVIALLY_CONSTRUCTIBLE cannot be directly set
-#elif defined(ABSL_HAVE_STD_IS_TRIVIALLY_ASSIGNABLE)
-#error ABSL_HAVE_STD_IS_TRIVIALLY_ASSIGNABLE cannot directly set
-#elif (defined(__clang__) && defined(_LIBCPP_VERSION)) ||                    \
-    (defined(__clang__) && __clang_major__ >= 15) ||                         \
-    (!defined(__clang__) &&                                                  \
-     ((ABSL_INTERNAL_HAVE_MIN_GNUC_VERSION(7, 4) && defined(__GLIBCXX__)) || \
-      (ABSL_INTERNAL_HAVE_MIN_GNUC_VERSION(8, 2) &&                          \
-       defined(_LIBCPP_VERSION)))) ||                                        \
-    (defined(_MSC_VER) && !defined(__NVCC__) && !defined(__clang__))
-#define ABSL_HAVE_STD_IS_TRIVIALLY_CONSTRUCTIBLE 1
+#ifdef ABSL_HAVE_STD_IS_TRIVIALLY_ASSIGNABLE
+#error ABSL_HAVE_STD_IS_TRIVIALLY_ASSIGNABLE cannot be directly set
+#else
 #define ABSL_HAVE_STD_IS_TRIVIALLY_ASSIGNABLE 1
 #endif
 
 // ABSL_HAVE_STD_IS_TRIVIALLY_COPYABLE
 //
 // Checks whether `std::is_trivially_copyable<T>` is supported.
-//
-// Notes: Clang 15+ with libc++ supports these features, GCC hasn't been tested.
-#if defined(ABSL_HAVE_STD_IS_TRIVIALLY_COPYABLE)
+#ifdef ABSL_HAVE_STD_IS_TRIVIALLY_COPYABLE
 #error ABSL_HAVE_STD_IS_TRIVIALLY_COPYABLE cannot be directly set
-#elif defined(__clang__) && (__clang_major__ >= 15)
 #define ABSL_HAVE_STD_IS_TRIVIALLY_COPYABLE 1
 #endif
 
@@ -429,7 +412,7 @@ static_assert(ABSL_INTERNAL_INLINE_NAMESPACE_STR[0] != 'h' ||
     defined(__asmjs__) || defined(__wasm__) || defined(__Fuchsia__) ||    \
     defined(__sun) || defined(__ASYLO__) || defined(__myriad2__) ||       \
     defined(__HAIKU__) || defined(__OpenBSD__) || defined(__NetBSD__) ||  \
-    defined(__QNX__)
+    defined(__QNX__) || defined(__VXWORKS__) || defined(__hexagon__)
 #define ABSL_HAVE_MMAP 1
 #endif
 
@@ -441,7 +424,7 @@ static_assert(ABSL_INTERNAL_INLINE_NAMESPACE_STR[0] != 'h' ||
 #error ABSL_HAVE_PTHREAD_GETSCHEDPARAM cannot be directly set
 #elif defined(__linux__) || defined(__APPLE__) || defined(__FreeBSD__) || \
     defined(_AIX) || defined(__ros__) || defined(__OpenBSD__) ||          \
-    defined(__NetBSD__)
+    defined(__NetBSD__) || defined(__VXWORKS__)
 #define ABSL_HAVE_PTHREAD_GETSCHEDPARAM 1
 #endif
 
@@ -460,7 +443,8 @@ static_assert(ABSL_INTERNAL_INLINE_NAMESPACE_STR[0] != 'h' ||
 // POSIX.1-2001.
 #ifdef ABSL_HAVE_SCHED_YIELD
 #error ABSL_HAVE_SCHED_YIELD cannot be directly set
-#elif defined(__linux__) || defined(__ros__) || defined(__native_client__)
+#elif defined(__linux__) || defined(__ros__) || defined(__native_client__) || \
+    defined(__VXWORKS__)
 #define ABSL_HAVE_SCHED_YIELD 1
 #endif
 
@@ -475,7 +459,7 @@ static_assert(ABSL_INTERNAL_INLINE_NAMESPACE_STR[0] != 'h' ||
 // platforms.
 #ifdef ABSL_HAVE_SEMAPHORE_H
 #error ABSL_HAVE_SEMAPHORE_H cannot be directly set
-#elif defined(__linux__) || defined(__ros__)
+#elif defined(__linux__) || defined(__ros__) || defined(__VXWORKS__)
 #define ABSL_HAVE_SEMAPHORE_H 1
 #endif
 
@@ -503,6 +487,8 @@ static_assert(ABSL_INTERNAL_INLINE_NAMESPACE_STR[0] != 'h' ||
 #elif defined(__Fuchsia__)
 // Signals don't exist on fuchsia.
 #elif defined(__native_client__)
+// Signals don't exist on hexagon/QuRT
+#elif defined(__hexagon__)
 #else
 // other standard libraries
 #define ABSL_HAVE_ALARM 1
@@ -536,41 +522,29 @@ static_assert(ABSL_INTERNAL_INLINE_NAMESPACE_STR[0] != 'h' ||
 #error "absl endian detection needs to be set up for your compiler"
 #endif
 
-// macOS < 10.13 and iOS < 11 don't let you use <any>, <optional>, or <variant>
-// even though the headers exist and are publicly noted to work, because the
-// libc++ shared library shipped on the system doesn't have the requisite
-// exported symbols.  See https://github.com/abseil/abseil-cpp/issues/207 and
+// macOS < 10.13 and iOS < 12 don't support <any>, <optional>, or <variant>
+// because the libc++ shared library shipped on the system doesn't have the
+// requisite exported symbols.  See
+// https://github.com/abseil/abseil-cpp/issues/207 and
 // https://developer.apple.com/documentation/xcode_release_notes/xcode_10_release_notes
 //
 // libc++ spells out the availability requirements in the file
 // llvm-project/libcxx/include/__config via the #define
-// _LIBCPP_AVAILABILITY_BAD_OPTIONAL_ACCESS.
-//
-// Unfortunately, Apple initially mis-stated the requirements as macOS < 10.14
-// and iOS < 12 in the libc++ headers. This was corrected by
+// _LIBCPP_AVAILABILITY_BAD_OPTIONAL_ACCESS. The set of versions has been
+// modified a few times, via
 // https://github.com/llvm/llvm-project/commit/7fb40e1569dd66292b647f4501b85517e9247953
-// which subsequently made it into the XCode 12.5 release. We need to match the
-// old (incorrect) conditions when built with old XCode, but can use the
-// corrected earlier versions with new XCode.
-#if defined(__APPLE__) && defined(_LIBCPP_VERSION) &&               \
-    ((_LIBCPP_VERSION >= 11000 && /* XCode 12.5 or later: */        \
-      ((defined(__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__) &&   \
-        __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__ < 101300) ||  \
-       (defined(__ENVIRONMENT_IPHONE_OS_VERSION_MIN_REQUIRED__) &&  \
-        __ENVIRONMENT_IPHONE_OS_VERSION_MIN_REQUIRED__ < 110000) || \
-       (defined(__ENVIRONMENT_WATCH_OS_VERSION_MIN_REQUIRED__) &&   \
-        __ENVIRONMENT_WATCH_OS_VERSION_MIN_REQUIRED__ < 40000) ||   \
-       (defined(__ENVIRONMENT_TV_OS_VERSION_MIN_REQUIRED__) &&      \
-        __ENVIRONMENT_TV_OS_VERSION_MIN_REQUIRED__ < 110000))) ||   \
-     (_LIBCPP_VERSION < 11000 && /* Pre-XCode 12.5: */              \
-      ((defined(__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__) &&   \
-        __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__ < 101400) ||  \
-       (defined(__ENVIRONMENT_IPHONE_OS_VERSION_MIN_REQUIRED__) &&  \
-        __ENVIRONMENT_IPHONE_OS_VERSION_MIN_REQUIRED__ < 120000) || \
-       (defined(__ENVIRONMENT_WATCH_OS_VERSION_MIN_REQUIRED__) &&   \
-        __ENVIRONMENT_WATCH_OS_VERSION_MIN_REQUIRED__ < 50000) ||   \
-       (defined(__ENVIRONMENT_TV_OS_VERSION_MIN_REQUIRED__) &&      \
-        __ENVIRONMENT_TV_OS_VERSION_MIN_REQUIRED__ < 120000))))
+// and
+// https://github.com/llvm/llvm-project/commit/0bc451e7e137c4ccadcd3377250874f641ca514a
+// The second has the actually correct versions, thus, is what we copy here.
+#if defined(__APPLE__) &&                                           \
+    ((defined(__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__) &&     \
+      __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__ < 101300) ||    \
+     (defined(__ENVIRONMENT_IPHONE_OS_VERSION_MIN_REQUIRED__) &&    \
+      __ENVIRONMENT_IPHONE_OS_VERSION_MIN_REQUIRED__ < 120000) ||   \
+     (defined(__ENVIRONMENT_WATCH_OS_VERSION_MIN_REQUIRED__) &&     \
+      __ENVIRONMENT_WATCH_OS_VERSION_MIN_REQUIRED__ < 50000) ||     \
+     (defined(__ENVIRONMENT_TV_OS_VERSION_MIN_REQUIRED__) &&        \
+      __ENVIRONMENT_TV_OS_VERSION_MIN_REQUIRED__ < 120000))
 #define ABSL_INTERNAL_APPLE_CXX17_TYPES_UNAVAILABLE 1
 #else
 #define ABSL_INTERNAL_APPLE_CXX17_TYPES_UNAVAILABLE 0
@@ -578,73 +552,44 @@ static_assert(ABSL_INTERNAL_INLINE_NAMESPACE_STR[0] != 'h' ||
 
 // ABSL_HAVE_STD_ANY
 //
-// Checks whether C++17 std::any is available by checking whether <any> exists.
+// Checks whether C++17 std::any is available.
 #ifdef ABSL_HAVE_STD_ANY
 #error "ABSL_HAVE_STD_ANY cannot be directly set."
-#endif
-
-#ifdef __has_include
-#if __has_include(<any>) && defined(__cplusplus) && __cplusplus >= 201703L && \
+#elif defined(ABSL_INTERNAL_CPLUSPLUS_LANG) && \
+    ABSL_INTERNAL_CPLUSPLUS_LANG >= 201703L && \
     !ABSL_INTERNAL_APPLE_CXX17_TYPES_UNAVAILABLE
 #define ABSL_HAVE_STD_ANY 1
 #endif
-#endif
 
 // ABSL_HAVE_STD_OPTIONAL
 //
 // Checks whether C++17 std::optional is available.
 #ifdef ABSL_HAVE_STD_OPTIONAL
 #error "ABSL_HAVE_STD_OPTIONAL cannot be directly set."
-#endif
-
-#ifdef __has_include
-#if __has_include(<optional>) && defined(__cplusplus) && \
-    __cplusplus >= 201703L && !ABSL_INTERNAL_APPLE_CXX17_TYPES_UNAVAILABLE
+#elif defined(ABSL_INTERNAL_CPLUSPLUS_LANG) &&  \
+    ABSL_INTERNAL_CPLUSPLUS_LANG >= 201703L && \
+    !ABSL_INTERNAL_APPLE_CXX17_TYPES_UNAVAILABLE
 #define ABSL_HAVE_STD_OPTIONAL 1
 #endif
-#endif
 
 // ABSL_HAVE_STD_VARIANT
 //
 // Checks whether C++17 std::variant is available.
 #ifdef ABSL_HAVE_STD_VARIANT
 #error "ABSL_HAVE_STD_VARIANT cannot be directly set."
-#endif
-
-#ifdef __has_include
-#if __has_include(<variant>) && defined(__cplusplus) && \
-    __cplusplus >= 201703L && !ABSL_INTERNAL_APPLE_CXX17_TYPES_UNAVAILABLE
+#elif defined(ABSL_INTERNAL_CPLUSPLUS_LANG) && \
+    ABSL_INTERNAL_CPLUSPLUS_LANG >= 201703L && \
+    !ABSL_INTERNAL_APPLE_CXX17_TYPES_UNAVAILABLE
 #define ABSL_HAVE_STD_VARIANT 1
 #endif
-#endif
 
 // ABSL_HAVE_STD_STRING_VIEW
 //
 // Checks whether C++17 std::string_view is available.
 #ifdef ABSL_HAVE_STD_STRING_VIEW
 #error "ABSL_HAVE_STD_STRING_VIEW cannot be directly set."
-#endif
-
-#ifdef __has_include
-#if __has_include(<string_view>) && defined(__cplusplus) && \
-    __cplusplus >= 201703L
-#define ABSL_HAVE_STD_STRING_VIEW 1
-#endif
-#endif
-
-// For MSVC, `__has_include` is supported in VS 2017 15.3, which is later than
-// the support for <optional>, <any>, <string_view>, <variant>. So we use
-// _MSC_VER to check whether we have VS 2017 RTM (when <optional>, <any>,
-// <string_view>, <variant> is implemented) or higher. Also, `__cplusplus` is
-// not correctly set by MSVC, so we use `_MSVC_LANG` to check the language
-// version.
-// TODO(zhangxy): fix tests before enabling aliasing for `std::any`.
-#if defined(_MSC_VER) && _MSC_VER >= 1910 &&         \
-    ((defined(_MSVC_LANG) && _MSVC_LANG > 201402) || \
-     (defined(__cplusplus) && __cplusplus > 201402))
-// #define ABSL_HAVE_STD_ANY 1
-#define ABSL_HAVE_STD_OPTIONAL 1
-#define ABSL_HAVE_STD_VARIANT 1
+#elif defined(ABSL_INTERNAL_CPLUSPLUS_LANG) && \
+    ABSL_INTERNAL_CPLUSPLUS_LANG >= 201703L
 #define ABSL_HAVE_STD_STRING_VIEW 1
 #endif
 
@@ -816,6 +761,20 @@ static_assert(ABSL_INTERNAL_INLINE_NAMESPACE_STR[0] != 'h' ||
 #define ABSL_HAVE_HWADDRESS_SANITIZER 1
 #endif
 
+// ABSL_HAVE_DATAFLOW_SANITIZER
+//
+// Dataflow Sanitizer (or DFSAN) is a generalised dynamic data flow analysis.
+#ifdef ABSL_HAVE_DATAFLOW_SANITIZER
+#error "ABSL_HAVE_DATAFLOW_SANITIZER cannot be directly set."
+#elif defined(DATAFLOW_SANITIZER)
+// GCC provides no method for detecting the presence of the standalone
+// DataFlowSanitizer (-fsanitize=dataflow), so GCC users of -fsanitize=dataflow
+// should also use -DDATAFLOW_SANITIZER.
+#define ABSL_HAVE_DATAFLOW_SANITIZER 1
+#elif ABSL_HAVE_FEATURE(dataflow_sanitizer)
+#define ABSL_HAVE_DATAFLOW_SANITIZER 1
+#endif
+
 // ABSL_HAVE_LEAK_SANITIZER
 //
 // LeakSanitizer (or lsan) is a detector of memory leaks.
@@ -830,7 +789,7 @@ static_assert(ABSL_INTERNAL_INLINE_NAMESPACE_STR[0] != 'h' ||
 #ifdef ABSL_HAVE_LEAK_SANITIZER
 #error "ABSL_HAVE_LEAK_SANITIZER cannot be directly set."
 #elif defined(LEAK_SANITIZER)
-// GCC provides no method for detecting the presense of the standalone
+// GCC provides no method for detecting the presence of the standalone
 // LeakSanitizer (-fsanitize=leak), so GCC users of -fsanitize=leak should also
 // use -DLEAK_SANITIZER.
 #define ABSL_HAVE_LEAK_SANITIZER 1
@@ -878,7 +837,9 @@ static_assert(ABSL_INTERNAL_INLINE_NAMESPACE_STR[0] != 'h' ||
 // RTTI support.
 #ifdef ABSL_INTERNAL_HAS_RTTI
 #error ABSL_INTERNAL_HAS_RTTI cannot be directly set
-#elif !defined(__GNUC__) || defined(__GXX_RTTI)
+#elif (defined(__GNUC__) && defined(__GXX_RTTI)) || \
+    (defined(_MSC_VER) && defined(_CPPRTTI)) ||     \
+    (!defined(__GNUC__) && !defined(_MSC_VER))
 #define ABSL_INTERNAL_HAS_RTTI 1
 #endif  // !defined(__GNUC__) || defined(__GXX_RTTI)
 
@@ -889,7 +850,8 @@ static_assert(ABSL_INTERNAL_INLINE_NAMESPACE_STR[0] != 'h' ||
 #error ABSL_INTERNAL_HAVE_SSE cannot be directly set
 #elif defined(__SSE__)
 #define ABSL_INTERNAL_HAVE_SSE 1
-#elif defined(_M_X64) || (defined(_M_IX86_FP) && _M_IX86_FP >= 1)
+#elif (defined(_M_X64) || (defined(_M_IX86_FP) && _M_IX86_FP >= 1)) && \
+    !defined(_M_ARM64EC)
 // MSVC only defines _M_IX86_FP for x86 32-bit code, and _M_IX86_FP >= 1
 // indicates that at least SSE was targeted with the /arch:SSE option.
 // All x86-64 processors support SSE, so support can be assumed.
@@ -904,7 +866,8 @@ static_assert(ABSL_INTERNAL_INLINE_NAMESPACE_STR[0] != 'h' ||
 #error ABSL_INTERNAL_HAVE_SSE2 cannot be directly set
 #elif defined(__SSE2__)
 #define ABSL_INTERNAL_HAVE_SSE2 1
-#elif defined(_M_X64) || (defined(_M_IX86_FP) && _M_IX86_FP >= 2)
+#elif (defined(_M_X64) || (defined(_M_IX86_FP) && _M_IX86_FP >= 2)) && \
+    !defined(_M_ARM64EC)
 // MSVC only defines _M_IX86_FP for x86 32-bit code, and _M_IX86_FP >= 2
 // indicates that at least SSE2 was targeted with the /arch:SSE2 option.
 // All x86-64 processors support SSE2, so support can be assumed.
@@ -951,4 +914,24 @@ static_assert(ABSL_INTERNAL_INLINE_NAMESPACE_STR[0] != 'h' ||
 #define ABSL_HAVE_CONSTANT_EVALUATED 1
 #endif
 
+// ABSL_INTERNAL_EMSCRIPTEN_VERSION combines Emscripten's three version macros
+// into an integer that can be compared against.
+#ifdef ABSL_INTERNAL_EMSCRIPTEN_VERSION
+#error ABSL_INTERNAL_EMSCRIPTEN_VERSION cannot be directly set
+#endif
+#ifdef __EMSCRIPTEN__
+#include <emscripten/version.h>
+#ifdef __EMSCRIPTEN_major__
+#if __EMSCRIPTEN_minor__ >= 1000
+#error __EMSCRIPTEN_minor__ is too big to fit in ABSL_INTERNAL_EMSCRIPTEN_VERSION
+#endif
+#if __EMSCRIPTEN_tiny__ >= 1000
+#error __EMSCRIPTEN_tiny__ is too big to fit in ABSL_INTERNAL_EMSCRIPTEN_VERSION
+#endif
+#define ABSL_INTERNAL_EMSCRIPTEN_VERSION                          \
+  ((__EMSCRIPTEN_major__)*1000000 + (__EMSCRIPTEN_minor__)*1000 + \
+   (__EMSCRIPTEN_tiny__))
+#endif
+#endif
+
 #endif  // ABSL_BASE_CONFIG_H_
diff --git a/absl/base/dynamic_annotations.h b/absl/base/dynamic_annotations.h
index 3ea7c156..7ba8912e 100644
--- a/absl/base/dynamic_annotations.h
+++ b/absl/base/dynamic_annotations.h
@@ -46,6 +46,7 @@
 #define ABSL_BASE_DYNAMIC_ANNOTATIONS_H_
 
 #include <stddef.h>
+#include <stdint.h>
 
 #include "absl/base/attributes.h"
 #include "absl/base/config.h"
@@ -53,6 +54,10 @@
 #include "absl/base/macros.h"
 #endif
 
+#ifdef ABSL_HAVE_HWADDRESS_SANITIZER
+#include <sanitizer/hwasan_interface.h>
+#endif
+
 // TODO(rogeeff): Remove after the backward compatibility period.
 #include "absl/base/internal/dynamic_annotations.h"  // IWYU pragma: export
 
@@ -111,7 +116,7 @@
 
 #if ABSL_INTERNAL_RACE_ANNOTATIONS_ENABLED == 1
 // Some of the symbols used in this section (e.g. AnnotateBenignRaceSized) are
-// defined by the compiler-based santizer implementation, not by the Abseil
+// defined by the compiler-based sanitizer implementation, not by the Abseil
 // library. Therefore they do not use ABSL_INTERNAL_C_SYMBOL.
 
 // -------------------------------------------------------------
@@ -457,6 +462,26 @@ ABSL_NAMESPACE_END
 #endif  // ABSL_HAVE_ADDRESS_SANITIZER
 
 // -------------------------------------------------------------------------
+// HWAddress sanitizer annotations
+
+#ifdef __cplusplus
+namespace absl {
+#ifdef ABSL_HAVE_HWADDRESS_SANITIZER
+// Under HWASAN changes the tag of the pointer.
+template <typename T>
+T* HwasanTagPointer(T* ptr, uintptr_t tag) {
+  return reinterpret_cast<T*>(__hwasan_tag_pointer(ptr, tag));
+}
+#else
+template <typename T>
+T* HwasanTagPointer(T* ptr, uintptr_t) {
+  return ptr;
+}
+#endif
+}  // namespace absl
+#endif
+
+// -------------------------------------------------------------------------
 // Undefine the macros intended only for this file.
 
 #undef ABSL_INTERNAL_RACE_ANNOTATIONS_ENABLED
diff --git a/absl/base/exception_safety_testing_test.cc b/absl/base/exception_safety_testing_test.cc
index a87fd6a9..bf5aa7cf 100644
--- a/absl/base/exception_safety_testing_test.cc
+++ b/absl/base/exception_safety_testing_test.cc
@@ -148,7 +148,7 @@ TEST(ThrowingValueTest, ThrowingBitwiseOps) {
   ThrowingValue<> bomb1, bomb2;
 
   TestOp([&bomb1]() { ~bomb1; });
-  TestOp([&]() { bomb1& bomb2; });
+  TestOp([&]() { bomb1 & bomb2; });
   TestOp([&]() { bomb1 | bomb2; });
   TestOp([&]() { bomb1 ^ bomb2; });
 }
@@ -332,13 +332,16 @@ TEST(ThrowingValueTest, NonThrowingPlacementDelete) {
   constexpr int kArrayLen = 2;
   // We intentionally create extra space to store the tag allocated by placement
   // new[].
-  constexpr int kStorageLen = 4;
+  constexpr size_t kExtraSpaceLen = sizeof(size_t) * 2;
 
   alignas(ThrowingValue<>) unsigned char buf[sizeof(ThrowingValue<>)];
   alignas(ThrowingValue<>) unsigned char
-      array_buf[sizeof(ThrowingValue<>[kStorageLen])];
+      array_buf[kExtraSpaceLen + sizeof(ThrowingValue<>[kArrayLen])];
   auto* placed = new (&buf) ThrowingValue<>(1);
   auto placed_array = new (&array_buf) ThrowingValue<>[kArrayLen];
+  auto* placed_array_end = reinterpret_cast<unsigned char*>(placed_array) +
+                           sizeof(ThrowingValue<>[kArrayLen]);
+  EXPECT_LE(placed_array_end, array_buf + sizeof(array_buf));
 
   SetCountdown();
   ExpectNoThrow([placed, &buf]() {
diff --git a/absl/base/internal/direct_mmap.h b/absl/base/internal/direct_mmap.h
index 815b8d23..1beb2ee4 100644
--- a/absl/base/internal/direct_mmap.h
+++ b/absl/base/internal/direct_mmap.h
@@ -72,7 +72,7 @@ namespace base_internal {
 // Platform specific logic extracted from
 // https://chromium.googlesource.com/linux-syscall-support/+/master/linux_syscall_support.h
 inline void* DirectMmap(void* start, size_t length, int prot, int flags, int fd,
-                        off64_t offset) noexcept {
+                        off_t offset) noexcept {
 #if defined(__i386__) || defined(__ARM_ARCH_3__) || defined(__ARM_EABI__) || \
     defined(__m68k__) || defined(__sh__) ||                                  \
     (defined(__hppa__) && !defined(__LP64__)) ||                             \
@@ -102,7 +102,7 @@ inline void* DirectMmap(void* start, size_t length, int prot, int flags, int fd,
 #else
   return reinterpret_cast<void*>(
       syscall(SYS_mmap2, start, length, prot, flags, fd,
-              static_cast<off_t>(offset / pagesize)));
+              static_cast<unsigned long>(offset / pagesize)));  // NOLINT
 #endif
 #elif defined(__s390x__)
   // On s390x, mmap() arguments are passed in memory.
diff --git a/absl/base/internal/exception_safety_testing.h b/absl/base/internal/exception_safety_testing.h
index 77a5aec6..c1061544 100644
--- a/absl/base/internal/exception_safety_testing.h
+++ b/absl/base/internal/exception_safety_testing.h
@@ -946,7 +946,7 @@ class ExceptionSafetyTest {
  *   `std::unique_ptr<T> operator()() const` where T is the type being tested.
  *   It is used for reliably creating identical T instances to test on.
  *
- * - Operation: The operation object (passsed in via tester.WithOperation(...)
+ * - Operation: The operation object (passed in via tester.WithOperation(...)
  *   or tester.Test(...)) must be invocable with the signature
  *   `void operator()(T*) const` where T is the type being tested. It is used
  *   for performing steps on a T instance that may throw and that need to be
diff --git a/absl/base/internal/low_level_alloc.cc b/absl/base/internal/low_level_alloc.cc
index 662167b0..6d2cfeac 100644
--- a/absl/base/internal/low_level_alloc.cc
+++ b/absl/base/internal/low_level_alloc.cc
@@ -42,25 +42,25 @@
 #include <windows.h>
 #endif
 
+#ifdef __linux__
+#include <sys/prctl.h>
+#endif
+
 #include <string.h>
+
 #include <algorithm>
 #include <atomic>
 #include <cerrno>
 #include <cstddef>
-#include <new>                   // for placement-new
+#include <new>  // for placement-new
 
 #include "absl/base/dynamic_annotations.h"
 #include "absl/base/internal/raw_logging.h"
 #include "absl/base/internal/spinlock.h"
 
-// MAP_ANONYMOUS
-#if defined(__APPLE__)
-// For mmap, Linux defines both MAP_ANONYMOUS and MAP_ANON and says MAP_ANON is
-// deprecated. In Darwin, MAP_ANON is all there is.
-#if !defined MAP_ANONYMOUS
+#if defined(MAP_ANON) && !defined(MAP_ANONYMOUS)
 #define MAP_ANONYMOUS MAP_ANON
-#endif  // !MAP_ANONYMOUS
-#endif  // __APPLE__
+#endif
 
 namespace absl {
 ABSL_NAMESPACE_BEGIN
@@ -122,7 +122,7 @@ static int IntLog2(size_t size, size_t base) {
 static int Random(uint32_t *state) {
   uint32_t r = *state;
   int result = 1;
-  while ((((r = r*1103515245 + 12345) >> 30) & 1) == 0) {
+  while ((((r = r * 1103515245 + 12345) >> 30) & 1) == 0) {
     result++;
   }
   *state = r;
@@ -144,7 +144,7 @@ static int LLA_SkiplistLevels(size_t size, size_t base, uint32_t *random) {
   size_t max_fit = (size - offsetof(AllocList, next)) / sizeof(AllocList *);
   int level = IntLog2(size, base) + (random != nullptr ? Random(random) : 1);
   if (static_cast<size_t>(level) > max_fit) level = static_cast<int>(max_fit);
-  if (level > kMaxLevel-1) level = kMaxLevel - 1;
+  if (level > kMaxLevel - 1) level = kMaxLevel - 1;
   ABSL_RAW_CHECK(level >= 1, "block not big enough for even one level");
   return level;
 }
@@ -153,8 +153,8 @@ static int LLA_SkiplistLevels(size_t size, size_t base, uint32_t *random) {
 // For 0 <= i < head->levels, set prev[i] to "no_greater", where no_greater
 // points to the last element at level i in the AllocList less than *e, or is
 // head if no such element exists.
-static AllocList *LLA_SkiplistSearch(AllocList *head,
-                                     AllocList *e, AllocList **prev) {
+static AllocList *LLA_SkiplistSearch(AllocList *head, AllocList *e,
+                                     AllocList **prev) {
   AllocList *p = head;
   for (int level = head->levels - 1; level >= 0; level--) {
     for (AllocList *n; (n = p->next[level]) != nullptr && n < e; p = n) {
@@ -190,7 +190,7 @@ static void LLA_SkiplistDelete(AllocList *head, AllocList *e,
     prev[i]->next[i] = e->next[i];
   }
   while (head->levels > 0 && head->next[head->levels - 1] == nullptr) {
-    head->levels--;   // reduce head->levels if level unused
+    head->levels--;  // reduce head->levels if level unused
   }
 }
 
@@ -249,9 +249,9 @@ void CreateGlobalArenas() {
 
 // Returns a global arena that does not call into hooks.  Used by NewArena()
 // when kCallMallocHook is not set.
-LowLevelAlloc::Arena* UnhookedArena() {
+LowLevelAlloc::Arena *UnhookedArena() {
   base_internal::LowLevelCallOnce(&create_globals_once, CreateGlobalArenas);
-  return reinterpret_cast<LowLevelAlloc::Arena*>(&unhooked_arena_storage);
+  return reinterpret_cast<LowLevelAlloc::Arena *>(&unhooked_arena_storage);
 }
 
 #ifndef ABSL_LOW_LEVEL_ALLOC_ASYNC_SIGNAL_SAFE_MISSING
@@ -269,7 +269,7 @@ LowLevelAlloc::Arena *UnhookedAsyncSigSafeArena() {
 // Returns the default arena, as used by LowLevelAlloc::Alloc() and friends.
 LowLevelAlloc::Arena *LowLevelAlloc::DefaultArena() {
   base_internal::LowLevelCallOnce(&create_globals_once, CreateGlobalArenas);
-  return reinterpret_cast<LowLevelAlloc::Arena*>(&default_arena_storage);
+  return reinterpret_cast<LowLevelAlloc::Arena *>(&default_arena_storage);
 }
 
 // magic numbers to identify allocated and unallocated blocks
@@ -356,8 +356,7 @@ LowLevelAlloc::Arena::Arena(uint32_t flags_value)
       min_size(2 * round_up),
       random(0) {
   freelist.header.size = 0;
-  freelist.header.magic =
-      Magic(kMagicUnallocated, &freelist.header);
+  freelist.header.magic = Magic(kMagicUnallocated, &freelist.header);
   freelist.header.arena = this;
   freelist.levels = 0;
   memset(freelist.next, 0, sizeof(freelist.next));
@@ -375,7 +374,7 @@ LowLevelAlloc::Arena *LowLevelAlloc::NewArena(uint32_t flags) {
     meta_data_arena = UnhookedArena();
   }
   Arena *result =
-    new (AllocWithArena(sizeof (*result), meta_data_arena)) Arena(flags);
+      new (AllocWithArena(sizeof(*result), meta_data_arena)) Arena(flags);
   return result;
 }
 
@@ -480,8 +479,8 @@ static void Coalesce(AllocList *a) {
     AllocList *prev[kMaxLevel];
     LLA_SkiplistDelete(&arena->freelist, n, prev);
     LLA_SkiplistDelete(&arena->freelist, a, prev);
-    a->levels = LLA_SkiplistLevels(a->header.size, arena->min_size,
-                                   &arena->random);
+    a->levels =
+        LLA_SkiplistLevels(a->header.size, arena->min_size, &arena->random);
     LLA_SkiplistInsert(&arena->freelist, a, prev);
   }
 }
@@ -489,27 +488,27 @@ static void Coalesce(AllocList *a) {
 // Adds block at location "v" to the free list
 // L >= arena->mu
 static void AddToFreelist(void *v, LowLevelAlloc::Arena *arena) {
-  AllocList *f = reinterpret_cast<AllocList *>(
-                        reinterpret_cast<char *>(v) - sizeof (f->header));
+  AllocList *f = reinterpret_cast<AllocList *>(reinterpret_cast<char *>(v) -
+                                               sizeof(f->header));
   ABSL_RAW_CHECK(f->header.magic == Magic(kMagicAllocated, &f->header),
                  "bad magic number in AddToFreelist()");
   ABSL_RAW_CHECK(f->header.arena == arena,
                  "bad arena pointer in AddToFreelist()");
-  f->levels = LLA_SkiplistLevels(f->header.size, arena->min_size,
-                                 &arena->random);
+  f->levels =
+      LLA_SkiplistLevels(f->header.size, arena->min_size, &arena->random);
   AllocList *prev[kMaxLevel];
   LLA_SkiplistInsert(&arena->freelist, f, prev);
   f->header.magic = Magic(kMagicUnallocated, &f->header);
-  Coalesce(f);                  // maybe coalesce with successor
-  Coalesce(prev[0]);            // maybe coalesce with predecessor
+  Coalesce(f);        // maybe coalesce with successor
+  Coalesce(prev[0]);  // maybe coalesce with predecessor
 }
 
 // Frees storage allocated by LowLevelAlloc::Alloc().
 // L < arena->mu
 void LowLevelAlloc::Free(void *v) {
   if (v != nullptr) {
-    AllocList *f = reinterpret_cast<AllocList *>(
-                        reinterpret_cast<char *>(v) - sizeof (f->header));
+    AllocList *f = reinterpret_cast<AllocList *>(reinterpret_cast<char *>(v) -
+                                                 sizeof(f->header));
     LowLevelAlloc::Arena *arena = f->header.arena;
     ArenaLock section(arena);
     AddToFreelist(v, arena);
@@ -524,21 +523,21 @@ void LowLevelAlloc::Free(void *v) {
 static void *DoAllocWithArena(size_t request, LowLevelAlloc::Arena *arena) {
   void *result = nullptr;
   if (request != 0) {
-    AllocList *s;       // will point to region that satisfies request
+    AllocList *s;  // will point to region that satisfies request
     ArenaLock section(arena);
     // round up with header
-    size_t req_rnd = RoundUp(CheckedAdd(request, sizeof (s->header)),
-                             arena->round_up);
-    for (;;) {      // loop until we find a suitable region
+    size_t req_rnd =
+        RoundUp(CheckedAdd(request, sizeof(s->header)), arena->round_up);
+    for (;;) {  // loop until we find a suitable region
       // find the minimum levels that a block of this size must have
       int i = LLA_SkiplistLevels(req_rnd, arena->min_size, nullptr) - 1;
-      if (i < arena->freelist.levels) {   // potential blocks exist
+      if (i < arena->freelist.levels) {        // potential blocks exist
         AllocList *before = &arena->freelist;  // predecessor of s
         while ((s = Next(i, before, arena)) != nullptr &&
                s->header.size < req_rnd) {
           before = s;
         }
-        if (s != nullptr) {       // we found a region
+        if (s != nullptr) {  // we found a region
           break;
         }
       }
@@ -550,7 +549,7 @@ static void *DoAllocWithArena(size_t request, LowLevelAlloc::Arena *arena) {
       size_t new_pages_size = RoundUp(req_rnd, arena->pagesize * 16);
       void *new_pages;
 #ifdef _WIN32
-      new_pages = VirtualAlloc(0, new_pages_size,
+      new_pages = VirtualAlloc(nullptr, new_pages_size,
                                MEM_RESERVE | MEM_COMMIT, PAGE_READWRITE);
       ABSL_RAW_CHECK(new_pages != nullptr, "VirtualAlloc failed");
 #else
@@ -570,6 +569,18 @@ static void *DoAllocWithArena(size_t request, LowLevelAlloc::Arena *arena) {
         ABSL_RAW_LOG(FATAL, "mmap error: %d", errno);
       }
 
+#ifdef __linux__
+#if defined(PR_SET_VMA) && defined(PR_SET_VMA_ANON_NAME)
+      // Attempt to name the allocated address range in /proc/$PID/smaps on
+      // Linux.
+      //
+      // This invocation of prctl() may fail if the Linux kernel was not
+      // configured with the CONFIG_ANON_VMA_NAME option.  This is OK since
+      // the naming of arenas is primarily a debugging aid.
+      prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, new_pages, new_pages_size,
+            "absl");
+#endif
+#endif  // __linux__
 #endif  // _WIN32
       arena->mu.Lock();
       s = reinterpret_cast<AllocList *>(new_pages);
@@ -580,12 +591,12 @@ static void *DoAllocWithArena(size_t request, LowLevelAlloc::Arena *arena) {
       AddToFreelist(&s->levels, arena);  // insert new region into free list
     }
     AllocList *prev[kMaxLevel];
-    LLA_SkiplistDelete(&arena->freelist, s, prev);    // remove from free list
+    LLA_SkiplistDelete(&arena->freelist, s, prev);  // remove from free list
     // s points to the first free region that's big enough
     if (CheckedAdd(req_rnd, arena->min_size) <= s->header.size) {
       // big enough to split
-      AllocList *n = reinterpret_cast<AllocList *>
-                        (req_rnd + reinterpret_cast<char *>(s));
+      AllocList *n =
+          reinterpret_cast<AllocList *>(req_rnd + reinterpret_cast<char *>(s));
       n->header.size = s->header.size - req_rnd;
       n->header.magic = Magic(kMagicAllocated, &n->header);
       n->header.arena = arena;
diff --git a/absl/base/internal/low_level_alloc.h b/absl/base/internal/low_level_alloc.h
index eabb14a9..c2f1f25d 100644
--- a/absl/base/internal/low_level_alloc.h
+++ b/absl/base/internal/low_level_alloc.h
@@ -46,7 +46,8 @@
 // for more information.
 #ifdef ABSL_LOW_LEVEL_ALLOC_ASYNC_SIGNAL_SAFE_MISSING
 #error ABSL_LOW_LEVEL_ALLOC_ASYNC_SIGNAL_SAFE_MISSING cannot be directly set
-#elif defined(_WIN32) || defined(__asmjs__) || defined(__wasm__)
+#elif defined(_WIN32) || defined(__asmjs__) || defined(__wasm__) || \
+    defined(__hexagon__)
 #define ABSL_LOW_LEVEL_ALLOC_ASYNC_SIGNAL_SAFE_MISSING 1
 #endif
 
diff --git a/absl/base/internal/nullability_impl.h b/absl/base/internal/nullability_impl.h
new file mode 100644
index 00000000..36e1b33d
--- /dev/null
+++ b/absl/base/internal/nullability_impl.h
@@ -0,0 +1,106 @@
+// Copyright 2023 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_BASE_INTERNAL_NULLABILITY_IMPL_H_
+#define ABSL_BASE_INTERNAL_NULLABILITY_IMPL_H_
+
+#include <memory>
+#include <type_traits>
+
+#include "absl/base/attributes.h"
+#include "absl/meta/type_traits.h"
+
+namespace absl {
+
+namespace nullability_internal {
+
+// `IsNullabilityCompatible` checks whether its first argument is a class
+// explicitly tagged as supporting nullability annotations. The tag is the type
+// declaration `absl_nullability_compatible`.
+template <typename, typename = void>
+struct IsNullabilityCompatible : std::false_type {};
+
+template <typename T>
+struct IsNullabilityCompatible<
+    T, absl::void_t<typename T::absl_nullability_compatible>> : std::true_type {
+};
+
+template <typename T>
+constexpr bool IsSupportedType = IsNullabilityCompatible<T>::value;
+
+template <typename T>
+constexpr bool IsSupportedType<T*> = true;
+
+template <typename T, typename U>
+constexpr bool IsSupportedType<T U::*> = true;
+
+template <typename T, typename... Deleter>
+constexpr bool IsSupportedType<std::unique_ptr<T, Deleter...>> = true;
+
+template <typename T>
+constexpr bool IsSupportedType<std::shared_ptr<T>> = true;
+
+template <typename T>
+struct EnableNullable {
+  static_assert(nullability_internal::IsSupportedType<std::remove_cv_t<T>>,
+                "Template argument must be a raw or supported smart pointer "
+                "type. See absl/base/nullability.h.");
+  using type = T;
+};
+
+template <typename T>
+struct EnableNonnull {
+  static_assert(nullability_internal::IsSupportedType<std::remove_cv_t<T>>,
+                "Template argument must be a raw or supported smart pointer "
+                "type. See absl/base/nullability.h.");
+  using type = T;
+};
+
+template <typename T>
+struct EnableNullabilityUnknown {
+  static_assert(nullability_internal::IsSupportedType<std::remove_cv_t<T>>,
+                "Template argument must be a raw or supported smart pointer "
+                "type. See absl/base/nullability.h.");
+  using type = T;
+};
+
+// Note: we do not apply Clang nullability attributes (e.g. _Nullable).  These
+// only support raw pointers, and conditionally enabling them only for raw
+// pointers inhibits template arg deduction.  Ideally, they would support all
+// pointer-like types.
+template <typename T, typename = typename EnableNullable<T>::type>
+using NullableImpl
+#if ABSL_HAVE_CPP_ATTRIBUTE(clang::annotate)
+    [[clang::annotate("Nullable")]]
+#endif
+    = T;
+
+template <typename T, typename = typename EnableNonnull<T>::type>
+using NonnullImpl
+#if ABSL_HAVE_CPP_ATTRIBUTE(clang::annotate)
+    [[clang::annotate("Nonnull")]]
+#endif
+    = T;
+
+template <typename T, typename = typename EnableNullabilityUnknown<T>::type>
+using NullabilityUnknownImpl
+#if ABSL_HAVE_CPP_ATTRIBUTE(clang::annotate)
+    [[clang::annotate("Nullability_Unspecified")]]
+#endif
+    = T;
+
+}  // namespace nullability_internal
+}  // namespace absl
+
+#endif  // ABSL_BASE_INTERNAL_NULLABILITY_IMPL_H_
diff --git a/absl/base/internal/prefetch.h b/absl/base/internal/prefetch.h
index 06419283..aecfd877 100644
--- a/absl/base/internal/prefetch.h
+++ b/absl/base/internal/prefetch.h
@@ -12,10 +12,14 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// TODO(b/265984188): remove all uses and delete this header.
+
 #ifndef ABSL_BASE_INTERNAL_PREFETCH_H_
 #define ABSL_BASE_INTERNAL_PREFETCH_H_
 
+#include "absl/base/attributes.h"
 #include "absl/base/config.h"
+#include "absl/base/prefetch.h"
 
 #ifdef __SSE__
 #include <xmmintrin.h>
@@ -72,10 +76,21 @@ namespace absl {
 ABSL_NAMESPACE_BEGIN
 namespace base_internal {
 
-void PrefetchT0(const void* addr);
+ABSL_DEPRECATED("Use absl::PrefetchToLocalCache() instead")
+inline void PrefetchT0(const void* address) {
+  absl::PrefetchToLocalCache(address);
+}
+
+ABSL_DEPRECATED("Use absl::PrefetchToLocalCache() instead")
+inline void PrefetchNta(const void* address) {
+  absl::PrefetchToLocalCacheNta(address);
+}
+
+ABSL_DEPRECATED("Use __builtin_prefetch() for advanced prefetch logic instead")
 void PrefetchT1(const void* addr);
+
+ABSL_DEPRECATED("Use __builtin_prefetch() for advanced prefetch logic instead")
 void PrefetchT2(const void* addr);
-void PrefetchNta(const void* addr);
 
 // Implementation details follow.
 
@@ -90,10 +105,6 @@ void PrefetchNta(const void* addr);
 // safe for all currently supported platforms. However, prefetch for
 // store may have problems depending on the target platform.
 //
-inline void PrefetchT0(const void* addr) {
-  // Note: this uses prefetcht0 on Intel.
-  __builtin_prefetch(addr, 0, 3);
-}
 inline void PrefetchT1(const void* addr) {
   // Note: this uses prefetcht1 on Intel.
   __builtin_prefetch(addr, 0, 2);
@@ -102,33 +113,21 @@ inline void PrefetchT2(const void* addr) {
   // Note: this uses prefetcht2 on Intel.
   __builtin_prefetch(addr, 0, 1);
 }
-inline void PrefetchNta(const void* addr) {
-  // Note: this uses prefetchtnta on Intel.
-  __builtin_prefetch(addr, 0, 0);
-}
 
 #elif defined(ABSL_INTERNAL_HAVE_SSE)
 
 #define ABSL_INTERNAL_HAVE_PREFETCH 1
 
-inline void PrefetchT0(const void* addr) {
-  _mm_prefetch(reinterpret_cast<const char*>(addr), _MM_HINT_T0);
-}
 inline void PrefetchT1(const void* addr) {
   _mm_prefetch(reinterpret_cast<const char*>(addr), _MM_HINT_T1);
 }
 inline void PrefetchT2(const void* addr) {
   _mm_prefetch(reinterpret_cast<const char*>(addr), _MM_HINT_T2);
 }
-inline void PrefetchNta(const void* addr) {
-  _mm_prefetch(reinterpret_cast<const char*>(addr), _MM_HINT_NTA);
-}
 
 #else
-inline void PrefetchT0(const void*) {}
 inline void PrefetchT1(const void*) {}
 inline void PrefetchT2(const void*) {}
-inline void PrefetchNta(const void*) {}
 #endif
 
 }  // namespace base_internal
diff --git a/absl/base/internal/raw_logging.cc b/absl/base/internal/raw_logging.cc
index 6273e847..4c922ccf 100644
--- a/absl/base/internal/raw_logging.cc
+++ b/absl/base/internal/raw_logging.cc
@@ -21,6 +21,10 @@
 #include <cstring>
 #include <string>
 
+#ifdef __EMSCRIPTEN__
+#include <emscripten/console.h>
+#endif
+
 #include "absl/base/attributes.h"
 #include "absl/base/config.h"
 #include "absl/base/internal/atomic_hook.h"
@@ -173,7 +177,7 @@ void RawLogVA(absl::LogSeverity severity, const char* file, int line,
     } else {
       DoRawLog(&buf, &size, "%s", kTruncated);
     }
-    AsyncSignalSafeWriteToStderr(buffer, strlen(buffer));
+    AsyncSignalSafeWriteError(buffer, strlen(buffer));
   }
 #else
   static_cast<void>(format);
@@ -201,9 +205,34 @@ void DefaultInternalLog(absl::LogSeverity severity, const char* file, int line,
 
 }  // namespace
 
-void AsyncSignalSafeWriteToStderr(const char* s, size_t len) {
+void AsyncSignalSafeWriteError(const char* s, size_t len) {
+  if (!len) return;
   absl::base_internal::ErrnoSaver errno_saver;
-#if defined(ABSL_HAVE_SYSCALL_WRITE)
+#if defined(__EMSCRIPTEN__)
+  // In WebAssembly, bypass filesystem emulation via fwrite.
+  if (s[len - 1] == '\n') {
+    // Skip a trailing newline character as emscripten_errn adds one itself.
+    len--;
+  }
+  // emscripten_errn was introduced in 3.1.41 but broken in standalone mode
+  // until 3.1.43.
+#if ABSL_INTERNAL_EMSCRIPTEN_VERSION >= 3001043
+  emscripten_errn(s, len);
+#else
+  char buf[kLogBufSize];
+  if (len >= kLogBufSize) {
+    len = kLogBufSize - 1;
+    constexpr size_t trunc_len = sizeof(kTruncated) - 2;
+    memcpy(buf + len - trunc_len, kTruncated, trunc_len);
+    buf[len] = '\0';
+    len -= trunc_len;
+  } else {
+    buf[len] = '\0';
+  }
+  memcpy(buf, s, len);
+  _emscripten_err(buf);
+#endif
+#elif defined(ABSL_HAVE_SYSCALL_WRITE)
   // We prefer calling write via `syscall` to minimize the risk of libc doing
   // something "helpful".
   syscall(SYS_write, STDERR_FILENO, s, len);
diff --git a/absl/base/internal/raw_logging.h b/absl/base/internal/raw_logging.h
index c7b889cd..b79550b2 100644
--- a/absl/base/internal/raw_logging.h
+++ b/absl/base/internal/raw_logging.h
@@ -48,6 +48,7 @@
     ::absl::raw_log_internal::RawLog(ABSL_RAW_LOG_INTERNAL_##severity,         \
                                      absl_raw_log_internal_basename, __LINE__, \
                                      __VA_ARGS__);                             \
+    ABSL_RAW_LOG_INTERNAL_MAYBE_UNREACHABLE_##severity;                        \
   } while (0)
 
 // Similar to CHECK(condition) << message, but for low-level modules:
@@ -77,8 +78,7 @@
     ::absl::raw_log_internal::internal_log_function(                      \
         ABSL_RAW_LOG_INTERNAL_##severity, absl_raw_log_internal_filename, \
         __LINE__, message);                                               \
-    if (ABSL_RAW_LOG_INTERNAL_##severity == ::absl::LogSeverity::kFatal)  \
-      ABSL_UNREACHABLE();                                                 \
+    ABSL_RAW_LOG_INTERNAL_MAYBE_UNREACHABLE_##severity;                   \
   } while (0)
 
 #define ABSL_INTERNAL_CHECK(condition, message)                    \
@@ -90,6 +90,20 @@
     }                                                              \
   } while (0)
 
+#ifndef NDEBUG
+
+#define ABSL_RAW_DLOG(severity, ...) ABSL_RAW_LOG(severity, __VA_ARGS__)
+#define ABSL_RAW_DCHECK(condition, message) ABSL_RAW_CHECK(condition, message)
+
+#else  // NDEBUG
+
+#define ABSL_RAW_DLOG(severity, ...)                   \
+  while (false) ABSL_RAW_LOG(severity, __VA_ARGS__)
+#define ABSL_RAW_DCHECK(condition, message) \
+  while (false) ABSL_RAW_CHECK(condition, message)
+
+#endif  // NDEBUG
+
 #define ABSL_RAW_LOG_INTERNAL_INFO ::absl::LogSeverity::kInfo
 #define ABSL_RAW_LOG_INTERNAL_WARNING ::absl::LogSeverity::kWarning
 #define ABSL_RAW_LOG_INTERNAL_ERROR ::absl::LogSeverity::kError
@@ -97,6 +111,12 @@
 #define ABSL_RAW_LOG_INTERNAL_LEVEL(severity) \
   ::absl::NormalizeLogSeverity(severity)
 
+#define ABSL_RAW_LOG_INTERNAL_MAYBE_UNREACHABLE_INFO
+#define ABSL_RAW_LOG_INTERNAL_MAYBE_UNREACHABLE_WARNING
+#define ABSL_RAW_LOG_INTERNAL_MAYBE_UNREACHABLE_ERROR
+#define ABSL_RAW_LOG_INTERNAL_MAYBE_UNREACHABLE_FATAL ABSL_UNREACHABLE()
+#define ABSL_RAW_LOG_INTERNAL_MAYBE_UNREACHABLE_LEVEL(severity)
+
 namespace absl {
 ABSL_NAMESPACE_BEGIN
 namespace raw_log_internal {
@@ -109,8 +129,8 @@ void RawLog(absl::LogSeverity severity, const char* file, int line,
             const char* format, ...) ABSL_PRINTF_ATTRIBUTE(4, 5);
 
 // Writes the provided buffer directly to stderr, in a signal-safe, low-level
-// manner.
-void AsyncSignalSafeWriteToStderr(const char* s, size_t len);
+// manner.  Preserves errno.
+void AsyncSignalSafeWriteError(const char* s, size_t len);
 
 // compile-time function to get the "base" filename, that is, the part of
 // a filename after the last "/" or "\" path separator.  The search starts at
diff --git a/absl/base/internal/sysinfo.cc b/absl/base/internal/sysinfo.cc
index da499d3a..8bcc4faf 100644
--- a/absl/base/internal/sysinfo.cc
+++ b/absl/base/internal/sysinfo.cc
@@ -41,6 +41,7 @@
 #include <string.h>
 
 #include <cassert>
+#include <cerrno>
 #include <cstdint>
 #include <cstdio>
 #include <cstdlib>
@@ -159,7 +160,7 @@ static double GetNominalCPUFrequency() {
     DWORD type = 0;
     DWORD data = 0;
     DWORD data_size = sizeof(data);
-    auto result = RegQueryValueExA(key, "~MHz", 0, &type,
+    auto result = RegQueryValueExA(key, "~MHz", nullptr, &type,
                                    reinterpret_cast<LPBYTE>(&data), &data_size);
     RegCloseKey(key);
     if (result == ERROR_SUCCESS && type == REG_DWORD &&
@@ -189,7 +190,13 @@ static double GetNominalCPUFrequency() {
 // and the memory location pointed to by value is set to the value read.
 static bool ReadLongFromFile(const char *file, long *value) {
   bool ret = false;
-  int fd = open(file, O_RDONLY | O_CLOEXEC);
+#if defined(_POSIX_C_SOURCE)
+  const int file_mode = (O_RDONLY | O_CLOEXEC);
+#else
+  const int file_mode = O_RDONLY;
+#endif
+
+  int fd = open(file, file_mode);
   if (fd != -1) {
     char line[1024];
     char *err;
@@ -225,8 +232,8 @@ static int64_t ReadMonotonicClockNanos() {
   int rc = clock_gettime(CLOCK_MONOTONIC, &t);
 #endif
   if (rc != 0) {
-    perror("clock_gettime() failed");
-    abort();
+    ABSL_INTERNAL_LOG(
+        FATAL, "clock_gettime() failed: (" + std::to_string(errno) + ")");
   }
   return int64_t{t.tv_sec} * 1000000000 + t.tv_nsec;
 }
@@ -414,82 +421,33 @@ pid_t GetTID() {
   return tid;
 }
 
-#else
+#elif defined(__APPLE__)
 
-// Fallback implementation of GetTID using pthread_getspecific.
-ABSL_CONST_INIT static once_flag tid_once;
-ABSL_CONST_INIT static pthread_key_t tid_key;
-ABSL_CONST_INIT static absl::base_internal::SpinLock tid_lock(
-    absl::kConstInit, base_internal::SCHEDULE_KERNEL_ONLY);
-
-// We set a bit per thread in this array to indicate that an ID is in
-// use. ID 0 is unused because it is the default value returned by
-// pthread_getspecific().
-ABSL_CONST_INIT static std::vector<uint32_t> *tid_array
-    ABSL_GUARDED_BY(tid_lock) = nullptr;
-static constexpr int kBitsPerWord = 32;  // tid_array is uint32_t.
-
-// Returns the TID to tid_array.
-static void FreeTID(void *v) {
-  intptr_t tid = reinterpret_cast<intptr_t>(v);
-  intptr_t word = tid / kBitsPerWord;
-  uint32_t mask = ~(1u << (tid % kBitsPerWord));
-  absl::base_internal::SpinLockHolder lock(&tid_lock);
-  assert(0 <= word && static_cast<size_t>(word) < tid_array->size());
-  (*tid_array)[static_cast<size_t>(word)] &= mask;
+pid_t GetTID() {
+  uint64_t tid;
+  // `nullptr` here implies this thread.  This only fails if the specified
+  // thread is invalid or the pointer-to-tid is null, so we needn't worry about
+  // it.
+  pthread_threadid_np(nullptr, &tid);
+  return static_cast<pid_t>(tid);
 }
 
-static void InitGetTID() {
-  if (pthread_key_create(&tid_key, FreeTID) != 0) {
-    // The logging system calls GetTID() so it can't be used here.
-    perror("pthread_key_create failed");
-    abort();
-  }
-
-  // Initialize tid_array.
-  absl::base_internal::SpinLockHolder lock(&tid_lock);
-  tid_array = new std::vector<uint32_t>(1);
-  (*tid_array)[0] = 1;  // ID 0 is never-allocated.
-}
+#elif defined(__native_client__)
 
-// Return a per-thread small integer ID from pthread's thread-specific data.
 pid_t GetTID() {
-  absl::call_once(tid_once, InitGetTID);
-
-  intptr_t tid = reinterpret_cast<intptr_t>(pthread_getspecific(tid_key));
-  if (tid != 0) {
-    return static_cast<pid_t>(tid);
-  }
-
-  int bit;  // tid_array[word] = 1u << bit;
-  size_t word;
-  {
-    // Search for the first unused ID.
-    absl::base_internal::SpinLockHolder lock(&tid_lock);
-    // First search for a word in the array that is not all ones.
-    word = 0;
-    while (word < tid_array->size() && ~(*tid_array)[word] == 0) {
-      ++word;
-    }
-    if (word == tid_array->size()) {
-      tid_array->push_back(0);  // No space left, add kBitsPerWord more IDs.
-    }
-    // Search for a zero bit in the word.
-    bit = 0;
-    while (bit < kBitsPerWord && (((*tid_array)[word] >> bit) & 1) != 0) {
-      ++bit;
-    }
-    tid =
-        static_cast<intptr_t>((word * kBitsPerWord) + static_cast<size_t>(bit));
-    (*tid_array)[word] |= 1u << bit;  // Mark the TID as allocated.
-  }
+  auto* thread = pthread_self();
+  static_assert(sizeof(pid_t) == sizeof(thread),
+                "In NaCL int expected to be the same size as a pointer");
+  return reinterpret_cast<pid_t>(thread);
+}
 
-  if (pthread_setspecific(tid_key, reinterpret_cast<void *>(tid)) != 0) {
-    perror("pthread_setspecific failed");
-    abort();
-  }
+#else
 
-  return static_cast<pid_t>(tid);
+// Fallback implementation of `GetTID` using `pthread_self`.
+pid_t GetTID() {
+  // `pthread_t` need not be arithmetic per POSIX; platforms where it isn't
+  // should be handled above.
+  return static_cast<pid_t>(pthread_self());
 }
 
 #endif
diff --git a/absl/base/internal/thread_identity.cc b/absl/base/internal/thread_identity.cc
index 79853f09..252443eb 100644
--- a/absl/base/internal/thread_identity.cc
+++ b/absl/base/internal/thread_identity.cc
@@ -58,18 +58,19 @@ void AllocateThreadIdentityKey(ThreadIdentityReclaimerFunction reclaimer) {
 // that protected visibility is unsupported.
 ABSL_CONST_INIT  // Must come before __attribute__((visibility("protected")))
 #if ABSL_HAVE_ATTRIBUTE(visibility) && !defined(__APPLE__)
-__attribute__((visibility("protected")))
+    __attribute__((visibility("protected")))
 #endif  // ABSL_HAVE_ATTRIBUTE(visibility) && !defined(__APPLE__)
 #if ABSL_PER_THREAD_TLS
-// Prefer __thread to thread_local as benchmarks indicate it is a bit faster.
-ABSL_PER_THREAD_TLS_KEYWORD ThreadIdentity* thread_identity_ptr = nullptr;
+    // Prefer __thread to thread_local as benchmarks indicate it is a bit
+    // faster.
+    ABSL_PER_THREAD_TLS_KEYWORD ThreadIdentity* thread_identity_ptr = nullptr;
 #elif defined(ABSL_HAVE_THREAD_LOCAL)
-thread_local ThreadIdentity* thread_identity_ptr = nullptr;
+    thread_local ThreadIdentity* thread_identity_ptr = nullptr;
 #endif  // ABSL_PER_THREAD_TLS
 #endif  // TLS or CPP11
 
-void SetCurrentThreadIdentity(
-    ThreadIdentity* identity, ThreadIdentityReclaimerFunction reclaimer) {
+void SetCurrentThreadIdentity(ThreadIdentity* identity,
+                              ThreadIdentityReclaimerFunction reclaimer) {
   assert(CurrentThreadIdentityIfPresent() == nullptr);
   // Associate our destructor.
   // NOTE: This call to pthread_setspecific is currently the only immovable
@@ -79,7 +80,7 @@ void SetCurrentThreadIdentity(
   absl::call_once(init_thread_identity_key_once, AllocateThreadIdentityKey,
                   reclaimer);
 
-#if defined(__EMSCRIPTEN__) || defined(__MINGW32__)
+#if defined(__EMSCRIPTEN__) || defined(__MINGW32__) || defined(__hexagon__)
   // Emscripten and MinGW pthread implementations does not support signals.
   // See https://kripken.github.io/emscripten-site/docs/porting/pthreads.html
   // for more information.
@@ -134,7 +135,7 @@ void ClearCurrentThreadIdentity() {
     ABSL_THREAD_IDENTITY_MODE == ABSL_THREAD_IDENTITY_MODE_USE_CPP11
   thread_identity_ptr = nullptr;
 #elif ABSL_THREAD_IDENTITY_MODE == \
-      ABSL_THREAD_IDENTITY_MODE_USE_POSIX_SETSPECIFIC
+    ABSL_THREAD_IDENTITY_MODE_USE_POSIX_SETSPECIFIC
   // pthread_setspecific expected to clear value on destruction
   assert(CurrentThreadIdentityIfPresent() == nullptr);
 #endif
diff --git a/absl/base/internal/thread_identity.h b/absl/base/internal/thread_identity.h
index 463acbc7..b6e917ce 100644
--- a/absl/base/internal/thread_identity.h
+++ b/absl/base/internal/thread_identity.h
@@ -62,8 +62,8 @@ struct PerThreadSynch {
     return reinterpret_cast<ThreadIdentity*>(this);
   }
 
-  PerThreadSynch *next;  // Circular waiter queue; initialized to 0.
-  PerThreadSynch *skip;  // If non-zero, all entries in Mutex queue
+  PerThreadSynch* next;  // Circular waiter queue; initialized to 0.
+  PerThreadSynch* skip;  // If non-zero, all entries in Mutex queue
                          // up to and including "skip" have same
                          // condition as this, and will be woken later
   bool may_skip;         // if false while on mutex queue, a mutex unlocker
@@ -104,10 +104,7 @@ struct PerThreadSynch {
   //
   // Transitions from kAvailable to kQueued require no barrier, they
   // are externally ordered by the Mutex.
-  enum State {
-    kAvailable,
-    kQueued
-  };
+  enum State { kAvailable, kQueued };
   std::atomic<State> state;
 
   // The wait parameters of the current wait.  waitp is null if the
@@ -122,14 +119,14 @@ struct PerThreadSynch {
   // pointer unchanged.
   SynchWaitParams* waitp;
 
-  intptr_t readers;     // Number of readers in mutex.
+  intptr_t readers;  // Number of readers in mutex.
 
   // When priority will next be read (cycles).
   int64_t next_priority_read_cycles;
 
   // Locks held; used during deadlock detection.
   // Allocated in Synch_GetAllLocks() and freed in ReclaimThreadIdentity().
-  SynchLocksHeld *all_locks;
+  SynchLocksHeld* all_locks;
 };
 
 // The instances of this class are allocated in NewThreadIdentity() with an
@@ -147,7 +144,7 @@ struct ThreadIdentity {
 
   // Private: Reserved for absl::synchronization_internal::Waiter.
   struct WaiterState {
-    alignas(void*) char data[128];
+    alignas(void*) char data[256];
   } waiter_state;
 
   // Used by PerThreadSem::{Get,Set}ThreadBlockedCounter().
@@ -170,7 +167,10 @@ struct ThreadIdentity {
 //
 // Does not malloc(*), and is async-signal safe.
 // [*] Technically pthread_setspecific() does malloc on first use; however this
-// is handled internally within tcmalloc's initialization already.
+// is handled internally within tcmalloc's initialization already. Note that
+// darwin does *not* use tcmalloc, so this can catch you if using MallocHooks
+// on Apple platforms. Whatever function is calling your MallocHooks will need
+// to watch for recursion on Apple platforms.
 //
 // New ThreadIdentity objects can be constructed and associated with a thread
 // by calling GetOrCreateCurrentThreadIdentity() in per-thread-sem.h.
@@ -217,7 +217,7 @@ void ClearCurrentThreadIdentity();
 #define ABSL_THREAD_IDENTITY_MODE ABSL_THREAD_IDENTITY_MODE_USE_CPP11
 #elif defined(__APPLE__) && defined(ABSL_HAVE_THREAD_LOCAL)
 #define ABSL_THREAD_IDENTITY_MODE ABSL_THREAD_IDENTITY_MODE_USE_CPP11
-#elif ABSL_PER_THREAD_TLS && defined(__GOOGLE_GRTE_VERSION__) &&        \
+#elif ABSL_PER_THREAD_TLS && defined(__GOOGLE_GRTE_VERSION__) && \
     (__GOOGLE_GRTE_VERSION__ >= 20140228L)
 // Support for async-safe TLS was specifically added in GRTEv4.  It's not
 // present in the upstream eglibc.
diff --git a/absl/base/internal/thread_identity_test.cc b/absl/base/internal/thread_identity_test.cc
index 46a6f743..5f17553e 100644
--- a/absl/base/internal/thread_identity_test.cc
+++ b/absl/base/internal/thread_identity_test.cc
@@ -95,7 +95,7 @@ TEST(ThreadIdentityTest, BasicIdentityWorksThreaded) {
 }
 
 TEST(ThreadIdentityTest, ReusedThreadIdentityMutexTest) {
-  // This test repeatly creates and joins a series of threads, each of
+  // This test repeatedly creates and joins a series of threads, each of
   // which acquires and releases shared Mutex locks. This verifies
   // Mutex operations work correctly under a reused
   // ThreadIdentity. Note that the most likely failure mode of this
diff --git a/absl/base/internal/throw_delegate.cc b/absl/base/internal/throw_delegate.cc
index c260ff1e..337e870c 100644
--- a/absl/base/internal/throw_delegate.cc
+++ b/absl/base/internal/throw_delegate.cc
@@ -26,22 +26,13 @@ namespace absl {
 ABSL_NAMESPACE_BEGIN
 namespace base_internal {
 
-// NOTE: The various STL exception throwing functions are placed within the
-// #ifdef blocks so the symbols aren't exposed on platforms that don't support
-// them, such as the Android NDK. For example, ANGLE fails to link when building
-// within AOSP without them, since the STL functions don't exist.
-namespace {
-#ifdef ABSL_HAVE_EXCEPTIONS
-template <typename T>
-[[noreturn]] void Throw(const T& error) {
-  throw error;
-}
-#endif
-}  // namespace
+// NOTE: The exception types, like `std::logic_error`, do not exist on all
+// platforms. (For example, the Android NDK does not have them.)
+// Therefore, their use must be guarded by `#ifdef` or equivalent.
 
 void ThrowStdLogicError(const std::string& what_arg) {
 #ifdef ABSL_HAVE_EXCEPTIONS
-  Throw(std::logic_error(what_arg));
+  throw std::logic_error(what_arg);
 #else
   ABSL_RAW_LOG(FATAL, "%s", what_arg.c_str());
   std::abort();
@@ -49,7 +40,7 @@ void ThrowStdLogicError(const std::string& what_arg) {
 }
 void ThrowStdLogicError(const char* what_arg) {
 #ifdef ABSL_HAVE_EXCEPTIONS
-  Throw(std::logic_error(what_arg));
+  throw std::logic_error(what_arg);
 #else
   ABSL_RAW_LOG(FATAL, "%s", what_arg);
   std::abort();
@@ -57,7 +48,7 @@ void ThrowStdLogicError(const char* what_arg) {
 }
 void ThrowStdInvalidArgument(const std::string& what_arg) {
 #ifdef ABSL_HAVE_EXCEPTIONS
-  Throw(std::invalid_argument(what_arg));
+  throw std::invalid_argument(what_arg);
 #else
   ABSL_RAW_LOG(FATAL, "%s", what_arg.c_str());
   std::abort();
@@ -65,7 +56,7 @@ void ThrowStdInvalidArgument(const std::string& what_arg) {
 }
 void ThrowStdInvalidArgument(const char* what_arg) {
 #ifdef ABSL_HAVE_EXCEPTIONS
-  Throw(std::invalid_argument(what_arg));
+  throw std::invalid_argument(what_arg);
 #else
   ABSL_RAW_LOG(FATAL, "%s", what_arg);
   std::abort();
@@ -74,7 +65,7 @@ void ThrowStdInvalidArgument(const char* what_arg) {
 
 void ThrowStdDomainError(const std::string& what_arg) {
 #ifdef ABSL_HAVE_EXCEPTIONS
-  Throw(std::domain_error(what_arg));
+  throw std::domain_error(what_arg);
 #else
   ABSL_RAW_LOG(FATAL, "%s", what_arg.c_str());
   std::abort();
@@ -82,7 +73,7 @@ void ThrowStdDomainError(const std::string& what_arg) {
 }
 void ThrowStdDomainError(const char* what_arg) {
 #ifdef ABSL_HAVE_EXCEPTIONS
-  Throw(std::domain_error(what_arg));
+  throw std::domain_error(what_arg);
 #else
   ABSL_RAW_LOG(FATAL, "%s", what_arg);
   std::abort();
@@ -91,7 +82,7 @@ void ThrowStdDomainError(const char* what_arg) {
 
 void ThrowStdLengthError(const std::string& what_arg) {
 #ifdef ABSL_HAVE_EXCEPTIONS
-  Throw(std::length_error(what_arg));
+  throw std::length_error(what_arg);
 #else
   ABSL_RAW_LOG(FATAL, "%s", what_arg.c_str());
   std::abort();
@@ -99,7 +90,7 @@ void ThrowStdLengthError(const std::string& what_arg) {
 }
 void ThrowStdLengthError(const char* what_arg) {
 #ifdef ABSL_HAVE_EXCEPTIONS
-  Throw(std::length_error(what_arg));
+  throw std::length_error(what_arg);
 #else
   ABSL_RAW_LOG(FATAL, "%s", what_arg);
   std::abort();
@@ -108,7 +99,7 @@ void ThrowStdLengthError(const char* what_arg) {
 
 void ThrowStdOutOfRange(const std::string& what_arg) {
 #ifdef ABSL_HAVE_EXCEPTIONS
-  Throw(std::out_of_range(what_arg));
+  throw std::out_of_range(what_arg);
 #else
   ABSL_RAW_LOG(FATAL, "%s", what_arg.c_str());
   std::abort();
@@ -116,7 +107,7 @@ void ThrowStdOutOfRange(const std::string& what_arg) {
 }
 void ThrowStdOutOfRange(const char* what_arg) {
 #ifdef ABSL_HAVE_EXCEPTIONS
-  Throw(std::out_of_range(what_arg));
+  throw std::out_of_range(what_arg);
 #else
   ABSL_RAW_LOG(FATAL, "%s", what_arg);
   std::abort();
@@ -125,7 +116,7 @@ void ThrowStdOutOfRange(const char* what_arg) {
 
 void ThrowStdRuntimeError(const std::string& what_arg) {
 #ifdef ABSL_HAVE_EXCEPTIONS
-  Throw(std::runtime_error(what_arg));
+  throw std::runtime_error(what_arg);
 #else
   ABSL_RAW_LOG(FATAL, "%s", what_arg.c_str());
   std::abort();
@@ -133,7 +124,7 @@ void ThrowStdRuntimeError(const std::string& what_arg) {
 }
 void ThrowStdRuntimeError(const char* what_arg) {
 #ifdef ABSL_HAVE_EXCEPTIONS
-  Throw(std::runtime_error(what_arg));
+  throw std::runtime_error(what_arg);
 #else
   ABSL_RAW_LOG(FATAL, "%s", what_arg);
   std::abort();
@@ -142,7 +133,7 @@ void ThrowStdRuntimeError(const char* what_arg) {
 
 void ThrowStdRangeError(const std::string& what_arg) {
 #ifdef ABSL_HAVE_EXCEPTIONS
-  Throw(std::range_error(what_arg));
+  throw std::range_error(what_arg);
 #else
   ABSL_RAW_LOG(FATAL, "%s", what_arg.c_str());
   std::abort();
@@ -150,7 +141,7 @@ void ThrowStdRangeError(const std::string& what_arg) {
 }
 void ThrowStdRangeError(const char* what_arg) {
 #ifdef ABSL_HAVE_EXCEPTIONS
-  Throw(std::range_error(what_arg));
+  throw std::range_error(what_arg);
 #else
   ABSL_RAW_LOG(FATAL, "%s", what_arg);
   std::abort();
@@ -159,7 +150,7 @@ void ThrowStdRangeError(const char* what_arg) {
 
 void ThrowStdOverflowError(const std::string& what_arg) {
 #ifdef ABSL_HAVE_EXCEPTIONS
-  Throw(std::overflow_error(what_arg));
+  throw std::overflow_error(what_arg);
 #else
   ABSL_RAW_LOG(FATAL, "%s", what_arg.c_str());
   std::abort();
@@ -167,7 +158,7 @@ void ThrowStdOverflowError(const std::string& what_arg) {
 }
 void ThrowStdOverflowError(const char* what_arg) {
 #ifdef ABSL_HAVE_EXCEPTIONS
-  Throw(std::overflow_error(what_arg));
+  throw std::overflow_error(what_arg);
 #else
   ABSL_RAW_LOG(FATAL, "%s", what_arg);
   std::abort();
@@ -176,7 +167,7 @@ void ThrowStdOverflowError(const char* what_arg) {
 
 void ThrowStdUnderflowError(const std::string& what_arg) {
 #ifdef ABSL_HAVE_EXCEPTIONS
-  Throw(std::underflow_error(what_arg));
+  throw std::underflow_error(what_arg);
 #else
   ABSL_RAW_LOG(FATAL, "%s", what_arg.c_str());
   std::abort();
@@ -184,7 +175,7 @@ void ThrowStdUnderflowError(const std::string& what_arg) {
 }
 void ThrowStdUnderflowError(const char* what_arg) {
 #ifdef ABSL_HAVE_EXCEPTIONS
-  Throw(std::underflow_error(what_arg));
+  throw std::underflow_error(what_arg);
 #else
   ABSL_RAW_LOG(FATAL, "%s", what_arg);
   std::abort();
@@ -193,7 +184,7 @@ void ThrowStdUnderflowError(const char* what_arg) {
 
 void ThrowStdBadFunctionCall() {
 #ifdef ABSL_HAVE_EXCEPTIONS
-  Throw(std::bad_function_call());
+  throw std::bad_function_call();
 #else
   std::abort();
 #endif
@@ -201,7 +192,7 @@ void ThrowStdBadFunctionCall() {
 
 void ThrowStdBadAlloc() {
 #ifdef ABSL_HAVE_EXCEPTIONS
-  Throw(std::bad_alloc());
+  throw std::bad_alloc();
 #else
   std::abort();
 #endif
diff --git a/absl/base/internal/unscaledcycleclock.cc b/absl/base/internal/unscaledcycleclock.cc
index b1c396c6..05e0e7ba 100644
--- a/absl/base/internal/unscaledcycleclock.cc
+++ b/absl/base/internal/unscaledcycleclock.cc
@@ -71,13 +71,12 @@ int64_t UnscaledCycleClock::Now() {
 #else
   int32_t tbu, tbl, tmp;
   asm volatile(
-      "0:\n"
       "mftbu %[hi32]\n"
       "mftb %[lo32]\n"
       "mftbu %[tmp]\n"
       "cmpw %[tmp],%[hi32]\n"
-      "bne 0b\n"
-      : [ hi32 ] "=r"(tbu), [ lo32 ] "=r"(tbl), [ tmp ] "=r"(tmp));
+      "bne $-16\n"  // Retry on failure.
+      : [hi32] "=r"(tbu), [lo32] "=r"(tbl), [tmp] "=r"(tmp));
   return (static_cast<int64_t>(tbu) << 32) | tbl;
 #endif
 #endif
diff --git a/absl/base/nullability.h b/absl/base/nullability.h
new file mode 100644
index 00000000..6f49b6f5
--- /dev/null
+++ b/absl/base/nullability.h
@@ -0,0 +1,224 @@
+// Copyright 2023 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// -----------------------------------------------------------------------------
+// File: nullability.h
+// -----------------------------------------------------------------------------
+//
+// This header file defines a set of "templated annotations" for designating the
+// expected nullability of pointers. These annotations allow you to designate
+// pointers in one of three classification states:
+//
+//  * "Non-null" (for pointers annotated `Nonnull<T>`), indicating that it is
+//    invalid for the given pointer to ever be null.
+//  * "Nullable" (for pointers annotated `Nullable<T>`), indicating that it is
+//    valid for the given pointer to be null.
+//  * "Unknown" (for pointers annotated `NullabilityUnknown<T>`), indicating
+//    that the given pointer has not been yet classified as either nullable or
+//    non-null. This is the default state of unannotated pointers.
+//
+// NOTE: unannotated pointers implicitly bear the annotation
+// `NullabilityUnknown<T>`; you should rarely, if ever, see this annotation used
+// in the codebase explicitly.
+//
+// -----------------------------------------------------------------------------
+// Nullability and Contracts
+// -----------------------------------------------------------------------------
+//
+// These nullability annotations allow you to more clearly specify contracts on
+// software components by narrowing the *preconditions*, *postconditions*, and
+// *invariants* of pointer state(s) in any given interface. It then depends on
+// context who is responsible for fulfilling the annotation's requirements.
+//
+// For example, a function may receive a pointer argument. Designating that
+// pointer argument as "non-null" tightens the precondition of the contract of
+// that function. It is then the responsibility of anyone calling such a
+// function to ensure that the passed pointer is not null.
+//
+// Similarly, a function may have a pointer as a return value. Designating that
+// return value as "non-null" tightens the postcondition of the contract of that
+// function. In this case, however, it is the responsibility of the function
+// itself to ensure that the returned pointer is not null.
+//
+// Clearly defining these contracts allows providers (and consumers) of such
+// pointers to have more confidence in their null state. If a function declares
+// a return value as "non-null", for example, the caller should not need to
+// check whether the returned value is `nullptr`; it can simply assume the
+// pointer is valid.
+//
+// Of course most interfaces already have expectations on the nullability state
+// of pointers, and these expectations are, in effect, a contract; often,
+// however, those contracts are either poorly or partially specified, assumed,
+// or misunderstood. These nullability annotations are designed to allow you to
+// formalize those contracts within the codebase.
+//
+// -----------------------------------------------------------------------------
+// Using Nullability Annotations
+// -----------------------------------------------------------------------------
+//
+// It is important to note that these annotations are not distinct strong
+// *types*. They are alias templates defined to be equal to the underlying
+// pointer type. A pointer annotated `Nonnull<T*>`, for example, is simply a
+// pointer of type `T*`. Each annotation acts as a form of documentation about
+// the contract for the given pointer. Each annotation requires providers or
+// consumers of these pointers across API boundaries to take appropriate steps
+// when setting or using these pointers:
+//
+// * "Non-null" pointers should never be null. It is the responsibility of the
+//   provider of this pointer to ensure that the pointer may never be set to
+//   null. Consumers of such pointers can treat such pointers as non-null.
+// * "Nullable" pointers may or may not be null. Consumers of such pointers
+//   should precede any usage of that pointer (e.g. a dereference operation)
+//   with a a `nullptr` check.
+// * "Unknown" pointers may be either "non-null" or "nullable" but have not been
+//   definitively determined to be in either classification state. Providers of
+//   such pointers across API boundaries should determine --  over time -- to
+//   annotate the pointer in either of the above two states. Consumers of such
+//   pointers across an API boundary should continue to treat such pointers as
+//   they currently do.
+//
+// Example:
+//
+// // PaySalary() requires the passed pointer to an `Employee` to be non-null.
+// void PaySalary(absl::Nonnull<Employee *> e) {
+//   pay(e->salary);  // OK to dereference
+// }
+//
+// // CompleteTransaction() guarantees the returned pointer to an `Account` to
+// // be non-null.
+// absl::Nonnull<Account *> balance CompleteTransaction(double fee) {
+// ...
+// }
+//
+// // Note that specifying a nullability annotation does not prevent someone
+// // from violating the contract:
+//
+// Nullable<Employee *> find(Map& employees, std::string_view name);
+//
+// void g(Map& employees) {
+//   Employee *e = find(employees, "Pat");
+//   // `e` can now be null.
+//   PaySalary(e); // Violates contract, but compiles!
+// }
+//
+// Nullability annotations, in other words, are useful for defining and
+// narrowing contracts; *enforcement* of those contracts depends on use and any
+// additional (static or dynamic analysis) tooling.
+//
+// NOTE: The "unknown" annotation state indicates that a pointer's contract has
+// not yet been positively identified. The unknown state therefore acts as a
+// form of documentation of your technical debt, and a codebase that adopts
+// nullability annotations should aspire to annotate every pointer as either
+// "non-null" or "nullable".
+//
+// -----------------------------------------------------------------------------
+// Applicability of Nullability Annotations
+// -----------------------------------------------------------------------------
+//
+// By default, nullability annotations are applicable to raw and smart
+// pointers. User-defined types can indicate compatibility with nullability
+// annotations by providing an `absl_nullability_compatible` nested type. The
+// actual definition of this inner type is not relevant as it is used merely as
+// a marker. It is common to use a using declaration of
+// `absl_nullability_compatible` set to void.
+//
+// // Example:
+// struct MyPtr {
+//   using absl_nullability_compatible = void;
+//   ...
+// };
+//
+// DISCLAIMER:
+// ===========================================================================
+// These nullability annotations are primarily a human readable signal about the
+// intended contract of the pointer. They are not *types* and do not currently
+// provide any correctness guarantees. For example, a pointer annotated as
+// `Nonnull<T*>` is *not guaranteed* to be non-null, and the compiler won't
+// alert or prevent assignment of a `Nullable<T*>` to a `Nonnull<T*>`.
+// ===========================================================================
+#ifndef ABSL_BASE_NULLABILITY_H_
+#define ABSL_BASE_NULLABILITY_H_
+
+#include "absl/base/internal/nullability_impl.h"
+
+namespace absl {
+
+// absl::Nonnull
+//
+// The indicated pointer is never null. It is the responsibility of the provider
+// of this pointer across an API boundary to ensure that the pointer is never be
+// set to null. Consumers of this pointer across an API boundary may safely
+// dereference the pointer.
+//
+// Example:
+//
+// // `employee` is designated as not null.
+// void PaySalary(absl::Nonnull<Employee *> employee) {
+//   pay(*employee);  // OK to dereference
+// }
+template <typename T>
+using Nonnull = nullability_internal::NonnullImpl<T>;
+
+// absl::Nullable
+//
+// The indicated pointer may, by design, be either null or non-null. Consumers
+// of this pointer across an API boundary should perform a `nullptr` check
+// before performing any operation using the pointer.
+//
+// Example:
+//
+// // `employee` may  be null.
+// void PaySalary(absl::Nullable<Employee *> employee) {
+//   if (employee != nullptr) {
+//     Pay(*employee);  // OK to dereference
+//   }
+// }
+template <typename T>
+using Nullable = nullability_internal::NullableImpl<T>;
+
+// absl::NullabilityUnknown (default)
+//
+// The indicated pointer has not yet been determined to be definitively
+// "non-null" or "nullable." Providers of such pointers across API boundaries
+// should, over time, annotate such pointers as either "non-null" or "nullable."
+// Consumers of these pointers across an API boundary should treat such pointers
+// with the same caution they treat currently unannotated pointers. Most
+// existing code will have "unknown"  pointers, which should eventually be
+// migrated into one of the above two nullability states: `Nonnull<T>` or
+//  `Nullable<T>`.
+//
+// NOTE: Because this annotation is the global default state, pointers without
+// any annotation are assumed to have "unknown" semantics. This assumption is
+// designed to minimize churn and reduce clutter within the codebase.
+//
+// Example:
+//
+// // `employee`s nullability state is unknown.
+// void PaySalary(absl::NullabilityUnknown<Employee *> employee) {
+//   Pay(*employee); // Potentially dangerous. API provider should investigate.
+// }
+//
+// Note that a pointer without an annotation, by default, is assumed to have the
+// annotation `NullabilityUnknown`.
+//
+// // `employee`s nullability state is unknown.
+// void PaySalary(Employee* employee) {
+//   Pay(*employee); // Potentially dangerous. API provider should investigate.
+// }
+template <typename T>
+using NullabilityUnknown = nullability_internal::NullabilityUnknownImpl<T>;
+
+}  // namespace absl
+
+#endif  // ABSL_BASE_NULLABILITY_H_
diff --git a/absl/base/nullability_test.cc b/absl/base/nullability_test.cc
new file mode 100644
index 00000000..028ea6ca
--- /dev/null
+++ b/absl/base/nullability_test.cc
@@ -0,0 +1,129 @@
+// Copyright 2023 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/base/nullability.h"
+
+#include <cassert>
+#include <memory>
+#include <utility>
+
+#include "gtest/gtest.h"
+#include "absl/base/attributes.h"
+
+namespace {
+using ::absl::Nonnull;
+using ::absl::NullabilityUnknown;
+using ::absl::Nullable;
+
+void funcWithNonnullArg(Nonnull<int*> /*arg*/) {}
+template <typename T>
+void funcWithDeducedNonnullArg(Nonnull<T*> /*arg*/) {}
+
+TEST(NonnullTest, NonnullArgument) {
+  int var = 0;
+  funcWithNonnullArg(&var);
+  funcWithDeducedNonnullArg(&var);
+}
+
+Nonnull<int*> funcWithNonnullReturn() {
+  static int var = 0;
+  return &var;
+}
+
+TEST(NonnullTest, NonnullReturn) {
+  auto var = funcWithNonnullReturn();
+  (void)var;
+}
+
+TEST(PassThroughTest, PassesThroughRawPointerToInt) {
+  EXPECT_TRUE((std::is_same<Nonnull<int*>, int*>::value));
+  EXPECT_TRUE((std::is_same<Nullable<int*>, int*>::value));
+  EXPECT_TRUE((std::is_same<NullabilityUnknown<int*>, int*>::value));
+}
+
+TEST(PassThroughTest, PassesThroughRawPointerToVoid) {
+  EXPECT_TRUE((std::is_same<Nonnull<void*>, void*>::value));
+  EXPECT_TRUE((std::is_same<Nullable<void*>, void*>::value));
+  EXPECT_TRUE((std::is_same<NullabilityUnknown<void*>, void*>::value));
+}
+
+TEST(PassThroughTest, PassesThroughUniquePointerToInt) {
+  using T = std::unique_ptr<int>;
+  EXPECT_TRUE((std::is_same<Nonnull<T>, T>::value));
+  EXPECT_TRUE((std::is_same<Nullable<T>, T>::value));
+  EXPECT_TRUE((std::is_same<NullabilityUnknown<T>, T>::value));
+}
+
+TEST(PassThroughTest, PassesThroughSharedPointerToInt) {
+  using T = std::shared_ptr<int>;
+  EXPECT_TRUE((std::is_same<Nonnull<T>, T>::value));
+  EXPECT_TRUE((std::is_same<Nullable<T>, T>::value));
+  EXPECT_TRUE((std::is_same<NullabilityUnknown<T>, T>::value));
+}
+
+TEST(PassThroughTest, PassesThroughSharedPointerToVoid) {
+  using T = std::shared_ptr<void>;
+  EXPECT_TRUE((std::is_same<Nonnull<T>, T>::value));
+  EXPECT_TRUE((std::is_same<Nullable<T>, T>::value));
+  EXPECT_TRUE((std::is_same<NullabilityUnknown<T>, T>::value));
+}
+
+TEST(PassThroughTest, PassesThroughPointerToMemberObject) {
+  using T = decltype(&std::pair<int, int>::first);
+  EXPECT_TRUE((std::is_same<Nonnull<T>, T>::value));
+  EXPECT_TRUE((std::is_same<Nullable<T>, T>::value));
+  EXPECT_TRUE((std::is_same<NullabilityUnknown<T>, T>::value));
+}
+
+TEST(PassThroughTest, PassesThroughPointerToMemberFunction) {
+  using T = decltype(&std::unique_ptr<int>::reset);
+  EXPECT_TRUE((std::is_same<Nonnull<T>, T>::value));
+  EXPECT_TRUE((std::is_same<Nullable<T>, T>::value));
+  EXPECT_TRUE((std::is_same<NullabilityUnknown<T>, T>::value));
+}
+
+}  // namespace
+
+// Nullable ADL lookup test
+namespace util {
+// Helper for NullableAdlTest.  Returns true, denoting that argument-dependent
+// lookup found this implementation of DidAdlWin.  Must be in namespace
+// util itself, not a nested anonymous namespace.
+template <typename T>
+bool DidAdlWin(T*) {
+  return true;
+}
+
+// Because this type is defined in namespace util, an unqualified call to
+// DidAdlWin with a pointer to MakeAdlWin will find the above implementation.
+struct MakeAdlWin {};
+}  // namespace util
+
+namespace {
+// Returns false, denoting that ADL did not inspect namespace util.  If it
+// had, the better match (T*) above would have won out over the (...) here.
+bool DidAdlWin(...) { return false; }
+
+TEST(NullableAdlTest, NullableAddsNothingToArgumentDependentLookup) {
+  // Treatment: util::Nullable<int*> contributes nothing to ADL because
+  // int* itself doesn't.
+  EXPECT_FALSE(DidAdlWin((int*)nullptr));
+  EXPECT_FALSE(DidAdlWin((Nullable<int*>)nullptr));
+
+  // Control: Argument-dependent lookup does find the implementation in
+  // namespace util when the underlying pointee type resides there.
+  EXPECT_TRUE(DidAdlWin((util::MakeAdlWin*)nullptr));
+  EXPECT_TRUE(DidAdlWin((Nullable<util::MakeAdlWin*>)nullptr));
+}
+}  // namespace
diff --git a/absl/base/options.h b/absl/base/options.h
index b6de636d..f308e1bf 100644
--- a/absl/base/options.h
+++ b/absl/base/options.h
@@ -200,7 +200,7 @@
 // allowed.
 
 #define ABSL_OPTION_USE_INLINE_NAMESPACE 1
-#define ABSL_OPTION_INLINE_NAMESPACE_NAME lts_20230125
+#define ABSL_OPTION_INLINE_NAMESPACE_NAME lts_20230802
 
 // ABSL_OPTION_HARDENED
 //
diff --git a/absl/base/policy_checks.h b/absl/base/policy_checks.h
index b8cd4c94..372e848d 100644
--- a/absl/base/policy_checks.h
+++ b/absl/base/policy_checks.h
@@ -44,10 +44,10 @@
 // Toolchain Check
 // -----------------------------------------------------------------------------
 
-// We support Visual Studio 2017 (MSVC++ 15.0) and later.
+// We support Visual Studio 2019 (MSVC++ 16.0) and later.
 // This minimum will go up.
-#if defined(_MSC_VER) && _MSC_VER < 1910 && !defined(__clang__)
-#error "This package requires Visual Studio 2017 (MSVC++ 15.0) or higher."
+#if defined(_MSC_VER) && _MSC_VER < 1920 && !defined(__clang__)
+#error "This package requires Visual Studio 2019 (MSVC++ 16.0) or higher."
 #endif
 
 // We support GCC 7 and later.
diff --git a/absl/base/prefetch.h b/absl/base/prefetch.h
new file mode 100644
index 00000000..de7a180d
--- /dev/null
+++ b/absl/base/prefetch.h
@@ -0,0 +1,198 @@
+// Copyright 2023 The Abseil Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// -----------------------------------------------------------------------------
+// File: prefetch.h
+// -----------------------------------------------------------------------------
+//
+// This header file defines prefetch functions to prefetch memory contents
+// into the first level cache (L1) for the current CPU. The prefetch logic
+// offered in this header is limited to prefetching first level cachelines
+// only, and is aimed at relatively 'simple' prefetching logic.
+//
+#ifndef ABSL_BASE_PREFETCH_H_
+#define ABSL_BASE_PREFETCH_H_
+
+#include "absl/base/config.h"
+
+#if defined(ABSL_INTERNAL_HAVE_SSE)
+#include <xmmintrin.h>
+#endif
+
+#if defined(_MSC_VER) && _MSC_VER >= 1900 && \
+    (defined(_M_X64) || defined(_M_IX86))
+#include <intrin.h>
+#pragma intrinsic(_mm_prefetch)
+#endif
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+// Moves data into the L1 cache before it is read, or "prefetches" it.
+//
+// The value of `addr` is the address of the memory to prefetch. If
+// the target and compiler support it, data prefetch instructions are
+// generated. If the prefetch is done some time before the memory is
+// read, it may be in the cache by the time the read occurs.
+//
+// This method prefetches data with the highest degree of temporal locality;
+// data is prefetched where possible into all levels of the cache.
+//
+// Incorrect or gratuitous use of this function can degrade performance.
+// Use this function only when representative benchmarks show an improvement.
+//
+// Example:
+//
+//  // Computes incremental checksum for `data`.
+//  int ComputeChecksum(int sum, absl::string_view data);
+//
+//  // Computes cumulative checksum for all values in `data`
+//  int ComputeChecksum(absl::Span<const std::string> data) {
+//    int sum = 0;
+//    auto it = data.begin();
+//    auto pit = data.begin();
+//    auto end = data.end();
+//    for (int dist = 8; dist > 0 && pit != data.end(); --dist, ++pit) {
+//      absl::PrefetchToLocalCache(pit->data());
+//    }
+//    for (; pit != end; ++pit, ++it) {
+//      sum = ComputeChecksum(sum, *it);
+//      absl::PrefetchToLocalCache(pit->data());
+//    }
+//    for (; it != end; ++it) {
+//      sum = ComputeChecksum(sum, *it);
+//    }
+//    return sum;
+//  }
+//
+void PrefetchToLocalCache(const void* addr);
+
+// Moves data into the L1 cache before it is read, or "prefetches" it.
+//
+// This function is identical to `PrefetchToLocalCache()` except that it has
+// non-temporal locality: the fetched data should not be left in any of the
+// cache tiers. This is useful for cases where the data is used only once /
+// short term, for example, invoking a destructor on an object.
+//
+// Incorrect or gratuitous use of this function can degrade performance.
+// Use this function only when representative benchmarks show an improvement.
+//
+// Example:
+//
+//  template <typename Iterator>
+//  void DestroyPointers(Iterator begin, Iterator end) {
+//    size_t distance = std::min(8U, bars.size());
+//
+//    int dist = 8;
+//    auto prefetch_it = begin;
+//    while (prefetch_it != end && --dist;) {
+//      absl::PrefetchToLocalCacheNta(*prefetch_it++);
+//    }
+//    while (prefetch_it != end) {
+//      delete *begin++;
+//      absl::PrefetchToLocalCacheNta(*prefetch_it++);
+//    }
+//    while (begin != end) {
+//      delete *begin++;
+//    }
+//  }
+//
+void PrefetchToLocalCacheNta(const void* addr);
+
+// Moves data into the L1 cache with the intent to modify it.
+//
+// This function is similar to `PrefetchToLocalCache()` except that it
+// prefetches cachelines with an 'intent to modify' This typically includes
+// invalidating cache entries for this address in all other cache tiers, and an
+// exclusive access intent.
+//
+// Incorrect or gratuitous use of this function can degrade performance. As this
+// function can invalidate cached cachelines on other caches and computer cores,
+// incorrect usage of this function can have an even greater negative impact
+// than incorrect regular prefetches.
+// Use this function only when representative benchmarks show an improvement.
+//
+// Example:
+//
+//  void* Arena::Allocate(size_t size) {
+//    void* ptr = AllocateBlock(size);
+//    absl::PrefetchToLocalCacheForWrite(p);
+//    return ptr;
+//  }
+//
+void PrefetchToLocalCacheForWrite(const void* addr);
+
+#if ABSL_HAVE_BUILTIN(__builtin_prefetch) || defined(__GNUC__)
+
+#define ABSL_HAVE_PREFETCH 1
+
+// See __builtin_prefetch:
+// https://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html.
+//
+inline void PrefetchToLocalCache(const void* addr) {
+  __builtin_prefetch(addr, 0, 3);
+}
+
+inline void PrefetchToLocalCacheNta(const void* addr) {
+  __builtin_prefetch(addr, 0, 0);
+}
+
+inline void PrefetchToLocalCacheForWrite(const void* addr) {
+  // [x86] gcc/clang don't generate PREFETCHW for __builtin_prefetch(.., 1)
+  // unless -march=broadwell or newer; this is not generally the default, so we
+  // manually emit prefetchw. PREFETCHW is recognized as a no-op on older Intel
+  // processors and has been present on AMD processors since the K6-2.
+#if defined(__x86_64__)
+  asm("prefetchw (%0)" : : "r"(addr));
+#else
+  __builtin_prefetch(addr, 1, 3);
+#endif
+}
+
+#elif defined(ABSL_INTERNAL_HAVE_SSE)
+
+#define ABSL_HAVE_PREFETCH 1
+
+inline void PrefetchToLocalCache(const void* addr) {
+  _mm_prefetch(reinterpret_cast<const char*>(addr), _MM_HINT_T0);
+}
+
+inline void PrefetchToLocalCacheNta(const void* addr) {
+  _mm_prefetch(reinterpret_cast<const char*>(addr), _MM_HINT_NTA);
+}
+
+inline void PrefetchToLocalCacheForWrite(const void* addr) {
+#if defined(_MM_HINT_ET0)
+  _mm_prefetch(reinterpret_cast<const char*>(addr), _MM_HINT_ET0);
+#elif !defined(_MSC_VER) && defined(__x86_64__)
+  // _MM_HINT_ET0 is not universally supported. As we commented further
+  // up, PREFETCHW is recognized as a no-op on older Intel processors
+  // and has been present on AMD processors since the K6-2. We have this
+  // disabled for MSVC compilers as this miscompiles on older MSVC compilers.
+  asm("prefetchw (%0)" : : "r"(addr));
+#endif
+}
+
+#else
+
+inline void PrefetchToLocalCache(const void* addr) {}
+inline void PrefetchToLocalCacheNta(const void* addr) {}
+inline void PrefetchToLocalCacheForWrite(const void* addr) {}
+
+#endif
+
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_BASE_PREFETCH_H_
diff --git a/absl/base/prefetch_test.cc b/absl/base/prefetch_test.cc
new file mode 100644
index 00000000..ee219897
--- /dev/null
+++ b/absl/base/prefetch_test.cc
@@ -0,0 +1,64 @@
+// Copyright 2023 The Abseil Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/base/prefetch.h"
+
+#include <memory>
+
+#include "gtest/gtest.h"
+
+namespace {
+
+// Below tests exercise the functions only to guarantee they compile and execute
+// correctly. We make no attempt at verifying any prefetch instructions being
+// generated and executed: we assume the various implementation in terms of
+// __builtin_prefetch() or x86 intrinsics to be correct and well tested.
+
+TEST(PrefetchTest, PrefetchToLocalCache_StackA) {
+  char buf[100] = {};
+  absl::PrefetchToLocalCache(buf);
+  absl::PrefetchToLocalCacheNta(buf);
+  absl::PrefetchToLocalCacheForWrite(buf);
+}
+
+TEST(PrefetchTest, PrefetchToLocalCache_Heap) {
+  auto memory = std::make_unique<char[]>(200 << 10);
+  memset(memory.get(), 0, 200 << 10);
+  absl::PrefetchToLocalCache(memory.get());
+  absl::PrefetchToLocalCacheNta(memory.get());
+  absl::PrefetchToLocalCacheForWrite(memory.get());
+  absl::PrefetchToLocalCache(memory.get() + (50 << 10));
+  absl::PrefetchToLocalCacheNta(memory.get() + (50 << 10));
+  absl::PrefetchToLocalCacheForWrite(memory.get() + (50 << 10));
+  absl::PrefetchToLocalCache(memory.get() + (100 << 10));
+  absl::PrefetchToLocalCacheNta(memory.get() + (100 << 10));
+  absl::PrefetchToLocalCacheForWrite(memory.get() + (100 << 10));
+  absl::PrefetchToLocalCache(memory.get() + (150 << 10));
+  absl::PrefetchToLocalCacheNta(memory.get() + (150 << 10));
+  absl::PrefetchToLocalCacheForWrite(memory.get() + (150 << 10));
+}
+
+TEST(PrefetchTest, PrefetchToLocalCache_Nullptr) {
+  absl::PrefetchToLocalCache(nullptr);
+  absl::PrefetchToLocalCacheNta(nullptr);
+  absl::PrefetchToLocalCacheForWrite(nullptr);
+}
+
+TEST(PrefetchTest, PrefetchToLocalCache_InvalidPtr) {
+  absl::PrefetchToLocalCache(reinterpret_cast<const void*>(0x785326532L));
+  absl::PrefetchToLocalCacheNta(reinterpret_cast<const void*>(0x785326532L));
+  absl::PrefetchToLocalCacheForWrite(reinterpret_cast<const void*>(0x78532L));
+}
+
+}  // namespace
diff --git a/absl/container/BUILD.bazel b/absl/container/BUILD.bazel
index 7a966d63..f22da59a 100644
--- a/absl/container/BUILD.bazel
+++ b/absl/container/BUILD.bazel
@@ -160,8 +160,8 @@ cc_test(
         "//absl/base:config",
         "//absl/base:core_headers",
         "//absl/base:exception_testing",
-        "//absl/base:raw_logging_internal",
         "//absl/hash:hash_testing",
+        "//absl/log:check",
         "//absl/memory",
         "//absl/strings",
         "@com_google_googletest//:gtest_main",
@@ -255,7 +255,7 @@ cc_test(
         ":unordered_map_lookup_test",
         ":unordered_map_members_test",
         ":unordered_map_modifiers_test",
-        "//absl/base:raw_logging_internal",
+        "//absl/log:check",
         "//absl/types:any",
         "@com_google_googletest//:gtest_main",
     ],
@@ -289,7 +289,7 @@ cc_test(
         ":unordered_set_lookup_test",
         ":unordered_set_members_test",
         ":unordered_set_modifiers_test",
-        "//absl/base:raw_logging_internal",
+        "//absl/log:check",
         "//absl/memory",
         "//absl/strings",
         "@com_google_googletest//:gtest_main",
@@ -534,11 +534,13 @@ cc_library(
         "//absl/base",
         "//absl/base:config",
         "//absl/base:core_headers",
+        "//absl/base:raw_logging_internal",
         "//absl/debugging:stacktrace",
         "//absl/memory",
         "//absl/profiling:exponential_biased",
         "//absl/profiling:sample_recorder",
         "//absl/synchronization",
+        "//absl/time",
         "//absl/utility",
     ],
 )
@@ -620,9 +622,11 @@ cc_library(
         ":hashtablez_sampler",
         "//absl/base:config",
         "//absl/base:core_headers",
+        "//absl/base:dynamic_annotations",
         "//absl/base:endian",
         "//absl/base:prefetch",
         "//absl/base:raw_logging_internal",
+        "//absl/hash",
         "//absl/memory",
         "//absl/meta:type_traits",
         "//absl/numeric:bits",
@@ -652,7 +656,6 @@ cc_test(
         "//absl/base:config",
         "//absl/base:core_headers",
         "//absl/base:prefetch",
-        "//absl/base:raw_logging_internal",
         "//absl/log",
         "//absl/strings",
         "@com_google_googletest//:gtest_main",
@@ -739,7 +742,7 @@ cc_test(
         ":layout",
         "//absl/base:config",
         "//absl/base:core_headers",
-        "//absl/base:raw_logging_internal",
+        "//absl/log:check",
         "//absl/types:span",
         "@com_google_googletest//:gtest_main",
     ],
@@ -997,6 +1000,7 @@ cc_test(
         "//absl/random",
         "//absl/strings",
         "//absl/types:compare",
+        "//absl/types:optional",
         "@com_google_googletest//:gtest_main",
     ],
 )
diff --git a/absl/container/CMakeLists.txt b/absl/container/CMakeLists.txt
index 416e3e38..39d95e02 100644
--- a/absl/container/CMakeLists.txt
+++ b/absl/container/CMakeLists.txt
@@ -80,6 +80,7 @@ absl_cc_test(
     absl::counting_allocator
     absl::flags
     absl::hash_testing
+    absl::optional
     absl::random_random
     absl::raw_logging_internal
     absl::strings
@@ -220,16 +221,16 @@ absl_cc_test(
   COPTS
     ${ABSL_TEST_COPTS}
   DEPS
-    absl::counting_allocator
-    absl::inlined_vector
-    absl::test_instance_tracker
+    absl::check
     absl::config
     absl::core_headers
+    absl::counting_allocator
     absl::exception_testing
     absl::hash_testing
+    absl::inlined_vector
     absl::memory
-    absl::raw_logging_internal
     absl::strings
+    absl::test_instance_tracker
     GTest::gmock_main
 )
 
@@ -299,14 +300,14 @@ absl_cc_test(
   COPTS
     ${ABSL_TEST_COPTS}
   DEPS
+    absl::any
+    absl::check
     absl::flat_hash_map
     absl::hash_generator_testing
     absl::unordered_map_constructor_test
     absl::unordered_map_lookup_test
     absl::unordered_map_members_test
     absl::unordered_map_modifiers_test
-    absl::any
-    absl::raw_logging_internal
     GTest::gmock_main
 )
 
@@ -336,15 +337,15 @@ absl_cc_test(
     ${ABSL_TEST_COPTS}
     "-DUNORDERED_SET_CXX17"
   DEPS
+    absl::check
     absl::flat_hash_set
     absl::hash_generator_testing
+    absl::memory
+    absl::strings
     absl::unordered_set_constructor_test
     absl::unordered_set_lookup_test
     absl::unordered_set_members_test
     absl::unordered_set_modifiers_test
-    absl::memory
-    absl::raw_logging_internal
-    absl::strings
     GTest::gmock_main
 )
 
@@ -592,8 +593,10 @@ absl_cc_library(
     absl::base
     absl::config
     absl::exponential_biased
+    absl::raw_logging_internal
     absl::sample_recorder
     absl::synchronization
+    absl::time
 )
 
 absl_cc_test(
@@ -704,7 +707,9 @@ absl_cc_library(
     absl::container_common
     absl::container_memory
     absl::core_headers
+    absl::dynamic_annotations
     absl::endian
+    absl::hash
     absl::hash_policy_traits
     absl::hashtable_debug_hooks
     absl::hashtablez_sampler
@@ -737,7 +742,6 @@ absl_cc_test(
     absl::log
     absl::prefetch
     absl::raw_hash_set
-    absl::raw_logging_internal
     absl::strings
     GTest::gmock_main
 )
@@ -783,9 +787,9 @@ absl_cc_test(
     ${ABSL_TEST_COPTS}
   DEPS
     absl::layout
+    absl::check
     absl::config
     absl::core_headers
-    absl::raw_logging_internal
     absl::span
     GTest::gmock_main
 )
diff --git a/absl/container/btree_test.cc b/absl/container/btree_test.cc
index cc763b29..72f446b2 100644
--- a/absl/container/btree_test.cc
+++ b/absl/container/btree_test.cc
@@ -18,6 +18,7 @@
 #include <array>
 #include <cstdint>
 #include <functional>
+#include <iostream>
 #include <iterator>
 #include <limits>
 #include <map>
@@ -46,6 +47,7 @@
 #include "absl/strings/str_split.h"
 #include "absl/strings/string_view.h"
 #include "absl/types/compare.h"
+#include "absl/types/optional.h"
 
 ABSL_FLAG(int, test_values, 10000, "The number of values to use for tests");
 
@@ -1231,8 +1233,10 @@ class BtreeNodePeer {
   }
 
   template <typename Btree>
-  constexpr static bool UsesGenerations() {
-    return Btree::params_type::kEnableGenerations;
+  constexpr static bool FieldTypeEqualsSlotType() {
+    return std::is_same<
+        typename btree_node<typename Btree::params_type>::field_type,
+        typename btree_node<typename Btree::params_type>::slot_type>::value;
   }
 };
 
@@ -1461,7 +1465,7 @@ class SizedBtreeSet
   using Base = typename SizedBtreeSet::btree_set_container;
 
  public:
-  SizedBtreeSet() {}
+  SizedBtreeSet() = default;
   using Base::Base;
 };
 
@@ -1479,9 +1483,17 @@ void ExpectOperationCounts(const int expected_moves,
   tracker->ResetCopiesMovesSwaps();
 }
 
+#ifdef ABSL_HAVE_ADDRESS_SANITIZER
+constexpr bool kAsan = true;
+#else
+constexpr bool kAsan = false;
+#endif
+
 // Note: when the values in this test change, it is expected to have an impact
 // on performance.
 TEST(Btree, MovesComparisonsCopiesSwapsTracking) {
+  if (kAsan) GTEST_SKIP() << "We do extra operations in ASan mode.";
+
   InstanceTracker tracker;
   // Note: this is minimum number of values per node.
   SizedBtreeSet<MovableOnlyInstance, /*TargetValuesPerNode=*/4> set4;
@@ -1499,10 +1511,9 @@ TEST(Btree, MovesComparisonsCopiesSwapsTracking) {
   EXPECT_EQ(BtreeNodePeer::GetNumSlotsPerNode<decltype(set61)>(), 61);
   EXPECT_EQ(BtreeNodePeer::GetNumSlotsPerNode<decltype(set100)>(), 100);
   if (sizeof(void *) == 8) {
-    EXPECT_EQ(
-        BtreeNodePeer::GetNumSlotsPerNode<absl::btree_set<int32_t>>(),
-        // When we have generations, there is one fewer slot.
-        BtreeNodePeer::UsesGenerations<absl::btree_set<int32_t>>() ? 60 : 61);
+    EXPECT_EQ(BtreeNodePeer::GetNumSlotsPerNode<absl::btree_set<int32_t>>(),
+              // When we have generations, there is one fewer slot.
+              BtreeGenerationsEnabled() ? 60 : 61);
   }
 
   // Test key insertion/deletion in random order.
@@ -1533,6 +1544,8 @@ struct MovableOnlyInstanceThreeWayCompare {
 // Note: when the values in this test change, it is expected to have an impact
 // on performance.
 TEST(Btree, MovesComparisonsCopiesSwapsTrackingThreeWayCompare) {
+  if (kAsan) GTEST_SKIP() << "We do extra operations in ASan mode.";
+
   InstanceTracker tracker;
   // Note: this is minimum number of values per node.
   SizedBtreeSet<MovableOnlyInstance, /*TargetValuesPerNode=*/4,
@@ -1556,10 +1569,9 @@ TEST(Btree, MovesComparisonsCopiesSwapsTrackingThreeWayCompare) {
   EXPECT_EQ(BtreeNodePeer::GetNumSlotsPerNode<decltype(set61)>(), 61);
   EXPECT_EQ(BtreeNodePeer::GetNumSlotsPerNode<decltype(set100)>(), 100);
   if (sizeof(void *) == 8) {
-    EXPECT_EQ(
-        BtreeNodePeer::GetNumSlotsPerNode<absl::btree_set<int32_t>>(),
-        // When we have generations, there is one fewer slot.
-        BtreeNodePeer::UsesGenerations<absl::btree_set<int32_t>>() ? 60 : 61);
+    EXPECT_EQ(BtreeNodePeer::GetNumSlotsPerNode<absl::btree_set<int32_t>>(),
+              // When we have generations, there is one fewer slot.
+              BtreeGenerationsEnabled() ? 60 : 61);
   }
 
   // Test key insertion/deletion in random order.
@@ -3137,27 +3149,104 @@ TEST(Btree, InvalidComparatorsCaught) {
     absl::btree_set<int, ThreeWaySumGreaterZeroCmp> set;
     EXPECT_DEATH(set.insert({0, 1, 2}), "lhs_comp_rhs < 0 -> rhs_comp_lhs > 0");
   }
+  // Verify that we detect cases of comparators that violate transitivity.
+  // When the comparators below check for the presence of an optional field,
+  // they violate transitivity because instances that have the optional field
+  // compare differently with each other from how they compare with instances
+  // that don't have the optional field.
+  struct ClockTime {
+    absl::optional<int> hour;
+    int minute;
+  };
+  // `comp(a,b) && comp(b,c) && !comp(a,c)` violates transitivity.
+  ClockTime a = {absl::nullopt, 1};
+  ClockTime b = {2, 5};
+  ClockTime c = {6, 0};
+  {
+    struct NonTransitiveTimeCmp {
+      bool operator()(ClockTime lhs, ClockTime rhs) const {
+        if (lhs.hour.has_value() && rhs.hour.has_value() &&
+            *lhs.hour != *rhs.hour) {
+          return *lhs.hour < *rhs.hour;
+        }
+        return lhs.minute < rhs.minute;
+      }
+    };
+    NonTransitiveTimeCmp cmp;
+    ASSERT_TRUE(cmp(a, b) && cmp(b, c) && !cmp(a, c));
+    absl::btree_set<ClockTime, NonTransitiveTimeCmp> set;
+    EXPECT_DEATH(set.insert({a, b, c}), "is_ordered_correctly");
+    absl::btree_multiset<ClockTime, NonTransitiveTimeCmp> mset;
+    EXPECT_DEATH(mset.insert({a, a, b, b, c, c}), "is_ordered_correctly");
+  }
+  {
+    struct ThreeWayNonTransitiveTimeCmp {
+      absl::weak_ordering operator()(ClockTime lhs, ClockTime rhs) const {
+        if (lhs.hour.has_value() && rhs.hour.has_value() &&
+            *lhs.hour != *rhs.hour) {
+          return *lhs.hour < *rhs.hour ? absl::weak_ordering::less
+                                       : absl::weak_ordering::greater;
+        }
+        return lhs.minute < rhs.minute    ? absl::weak_ordering::less
+               : lhs.minute == rhs.minute ? absl::weak_ordering::equivalent
+                                          : absl::weak_ordering::greater;
+      }
+    };
+    ThreeWayNonTransitiveTimeCmp cmp;
+    ASSERT_TRUE(cmp(a, b) < 0 && cmp(b, c) < 0 && cmp(a, c) > 0);
+    absl::btree_set<ClockTime, ThreeWayNonTransitiveTimeCmp> set;
+    EXPECT_DEATH(set.insert({a, b, c}), "is_ordered_correctly");
+    absl::btree_multiset<ClockTime, ThreeWayNonTransitiveTimeCmp> mset;
+    EXPECT_DEATH(mset.insert({a, a, b, b, c, c}), "is_ordered_correctly");
+  }
+}
+
+TEST(Btree, MutatedKeysCaught) {
+  if (!IsAssertEnabled()) GTEST_SKIP() << "Assertions not enabled.";
+
+  struct IntPtrCmp {
+    bool operator()(int *lhs, int *rhs) const { return *lhs < *rhs; }
+  };
+  {
+    absl::btree_set<int *, IntPtrCmp> set;
+    int arr[] = {0, 1, 2};
+    set.insert({&arr[0], &arr[1], &arr[2]});
+    arr[0] = 100;
+    EXPECT_DEATH(set.insert(&arr[0]), "is_ordered_correctly");
+  }
+  {
+    absl::btree_multiset<int *, IntPtrCmp> set;
+    int arr[] = {0, 1, 2};
+    set.insert({&arr[0], &arr[0], &arr[1], &arr[1], &arr[2], &arr[2]});
+    arr[0] = 100;
+    EXPECT_DEATH(set.insert(&arr[0]), "is_ordered_correctly");
+  }
 }
 
 #ifndef _MSC_VER
 // This test crashes on MSVC.
 TEST(Btree, InvalidIteratorUse) {
-  if (!BtreeNodePeer::UsesGenerations<absl::btree_set<int>>())
+  if (!BtreeGenerationsEnabled())
     GTEST_SKIP() << "Generation validation for iterators is disabled.";
 
+  // Invalid memory use can trigger heap-use-after-free in ASan or invalidated
+  // iterator assertions.
+  constexpr const char *kInvalidMemoryDeathMessage =
+      "heap-use-after-free|invalidated iterator";
+
   {
     absl::btree_set<int> set;
     for (int i = 0; i < 10; ++i) set.insert(i);
     auto it = set.begin();
     set.erase(it++);
-    EXPECT_DEATH(set.erase(it++), "invalidated iterator");
+    EXPECT_DEATH(set.erase(it++), kInvalidMemoryDeathMessage);
   }
   {
     absl::btree_set<int> set;
     for (int i = 0; i < 10; ++i) set.insert(i);
     auto it = set.insert(20).first;
     set.insert(30);
-    EXPECT_DEATH(*it, "invalidated iterator");
+    EXPECT_DEATH(*it, kInvalidMemoryDeathMessage);
   }
   {
     absl::btree_set<int> set;
@@ -3165,15 +3254,15 @@ TEST(Btree, InvalidIteratorUse) {
     auto it = set.find(5000);
     ASSERT_NE(it, set.end());
     set.erase(1);
-    EXPECT_DEATH(*it, "invalidated iterator");
+    EXPECT_DEATH(*it, kInvalidMemoryDeathMessage);
   }
   {
     absl::btree_set<int> set;
     for (int i = 0; i < 10; ++i) set.insert(i);
     auto it = set.insert(20).first;
     set.insert(30);
-    EXPECT_DEATH(void(it == set.begin()), "invalidated iterator");
-    EXPECT_DEATH(void(set.begin() == it), "invalidated iterator");
+    EXPECT_DEATH(void(it == set.begin()), kInvalidMemoryDeathMessage);
+    EXPECT_DEATH(void(set.begin() == it), kInvalidMemoryDeathMessage);
   }
 }
 #endif
@@ -3464,6 +3553,57 @@ TEST(Btree, InvalidIteratorComparison) {
   EXPECT_DEATH(void(iter2 == iter1), kDifferentContainerDeathMessage);
 }
 
+TEST(Btree, InvalidPointerUse) {
+  if (!kAsan)
+    GTEST_SKIP() << "We only detect invalid pointer use in ASan mode.";
+
+  absl::btree_set<int> set;
+  set.insert(0);
+  const int *ptr = &*set.begin();
+  set.insert(1);
+  EXPECT_DEATH(std::cout << *ptr, "heap-use-after-free");
+  size_t slots_per_node = BtreeNodePeer::GetNumSlotsPerNode<decltype(set)>();
+  for (int i = 2; i < slots_per_node - 1; ++i) set.insert(i);
+  ptr = &*set.begin();
+  set.insert(static_cast<int>(slots_per_node));
+  EXPECT_DEATH(std::cout << *ptr, "heap-use-after-free");
+}
+
+template<typename Set>
+void TestBasicFunctionality(Set set) {
+  using value_type = typename Set::value_type;
+  for (int i = 0; i < 100; ++i) { set.insert(value_type(i)); }
+  for (int i = 50; i < 100; ++i) { set.erase(value_type(i)); }
+  auto it = set.begin();
+  for (int i = 0; i < 50; ++i, ++it) {
+    ASSERT_EQ(set.find(value_type(i)), it) << i;
+  }
+}
+
+template<size_t align>
+struct alignas(align) OveralignedKey {
+  explicit OveralignedKey(int i) : key(i) {}
+  bool operator<(const OveralignedKey &other) const { return key < other.key; }
+  int key = 0;
+};
+
+TEST(Btree, OveralignedKey) {
+  // Test basic functionality with both even and odd numbers of slots per node.
+  // The goal here is to detect cases where alignment may be incorrect.
+  TestBasicFunctionality(
+      SizedBtreeSet<OveralignedKey<16>, /*TargetValuesPerNode=*/8>());
+  TestBasicFunctionality(
+      SizedBtreeSet<OveralignedKey<16>, /*TargetValuesPerNode=*/9>());
+}
+
+TEST(Btree, FieldTypeEqualsSlotType) {
+  // This breaks if we try to do layout_type::Pointer<slot_type> because
+  // slot_type is the same as field_type.
+  using set_type = absl::btree_set<uint8_t>;
+  static_assert(BtreeNodePeer::FieldTypeEqualsSlotType<set_type>(), "");
+  TestBasicFunctionality(set_type());
+}
+
 }  // namespace
 }  // namespace container_internal
 ABSL_NAMESPACE_END
diff --git a/absl/container/fixed_array.h b/absl/container/fixed_array.h
index b67379cf..9f1c813d 100644
--- a/absl/container/fixed_array.h
+++ b/absl/container/fixed_array.h
@@ -117,14 +117,20 @@ class FixedArray {
       (N == kFixedArrayUseDefault ? kInlineBytesDefault / sizeof(value_type)
                                   : static_cast<size_type>(N));
 
-  FixedArray(
-      const FixedArray& other,
-      const allocator_type& a = allocator_type()) noexcept(NoexceptCopyable())
+  FixedArray(const FixedArray& other) noexcept(NoexceptCopyable())
+      : FixedArray(other,
+                   AllocatorTraits::select_on_container_copy_construction(
+                       other.storage_.alloc())) {}
+
+  FixedArray(const FixedArray& other,
+             const allocator_type& a) noexcept(NoexceptCopyable())
       : FixedArray(other.begin(), other.end(), a) {}
 
-  FixedArray(
-      FixedArray&& other,
-      const allocator_type& a = allocator_type()) noexcept(NoexceptMovable())
+  FixedArray(FixedArray&& other) noexcept(NoexceptMovable())
+      : FixedArray(std::move(other), other.storage_.alloc()) {}
+
+  FixedArray(FixedArray&& other,
+             const allocator_type& a) noexcept(NoexceptMovable())
       : FixedArray(std::make_move_iterator(other.begin()),
                    std::make_move_iterator(other.end()), a) {}
 
@@ -200,18 +206,22 @@ class FixedArray {
   //
   // Returns a const T* pointer to elements of the `FixedArray`. This pointer
   // can be used to access (but not modify) the contained elements.
-  const_pointer data() const { return AsValueType(storage_.begin()); }
+  const_pointer data() const ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return AsValueType(storage_.begin());
+  }
 
   // Overload of FixedArray::data() to return a T* pointer to elements of the
   // fixed array. This pointer can be used to access and modify the contained
   // elements.
-  pointer data() { return AsValueType(storage_.begin()); }
+  pointer data() ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return AsValueType(storage_.begin());
+  }
 
   // FixedArray::operator[]
   //
   // Returns a reference the ith element of the fixed array.
   // REQUIRES: 0 <= i < size()
-  reference operator[](size_type i) {
+  reference operator[](size_type i) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     ABSL_HARDENING_ASSERT(i < size());
     return data()[i];
   }
@@ -219,7 +229,7 @@ class FixedArray {
   // Overload of FixedArray::operator()[] to return a const reference to the
   // ith element of the fixed array.
   // REQUIRES: 0 <= i < size()
-  const_reference operator[](size_type i) const {
+  const_reference operator[](size_type i) const ABSL_ATTRIBUTE_LIFETIME_BOUND {
     ABSL_HARDENING_ASSERT(i < size());
     return data()[i];
   }
@@ -228,7 +238,7 @@ class FixedArray {
   //
   // Bounds-checked access.  Returns a reference to the ith element of the fixed
   // array, or throws std::out_of_range
-  reference at(size_type i) {
+  reference at(size_type i) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     if (ABSL_PREDICT_FALSE(i >= size())) {
       base_internal::ThrowStdOutOfRange("FixedArray::at failed bounds check");
     }
@@ -237,7 +247,7 @@ class FixedArray {
 
   // Overload of FixedArray::at() to return a const reference to the ith element
   // of the fixed array.
-  const_reference at(size_type i) const {
+  const_reference at(size_type i) const ABSL_ATTRIBUTE_LIFETIME_BOUND {
     if (ABSL_PREDICT_FALSE(i >= size())) {
       base_internal::ThrowStdOutOfRange("FixedArray::at failed bounds check");
     }
@@ -247,14 +257,14 @@ class FixedArray {
   // FixedArray::front()
   //
   // Returns a reference to the first element of the fixed array.
-  reference front() {
+  reference front() ABSL_ATTRIBUTE_LIFETIME_BOUND {
     ABSL_HARDENING_ASSERT(!empty());
     return data()[0];
   }
 
   // Overload of FixedArray::front() to return a reference to the first element
   // of a fixed array of const values.
-  const_reference front() const {
+  const_reference front() const ABSL_ATTRIBUTE_LIFETIME_BOUND {
     ABSL_HARDENING_ASSERT(!empty());
     return data()[0];
   }
@@ -262,14 +272,14 @@ class FixedArray {
   // FixedArray::back()
   //
   // Returns a reference to the last element of the fixed array.
-  reference back() {
+  reference back() ABSL_ATTRIBUTE_LIFETIME_BOUND {
     ABSL_HARDENING_ASSERT(!empty());
     return data()[size() - 1];
   }
 
   // Overload of FixedArray::back() to return a reference to the last element
   // of a fixed array of const values.
-  const_reference back() const {
+  const_reference back() const ABSL_ATTRIBUTE_LIFETIME_BOUND {
     ABSL_HARDENING_ASSERT(!empty());
     return data()[size() - 1];
   }
@@ -277,62 +287,74 @@ class FixedArray {
   // FixedArray::begin()
   //
   // Returns an iterator to the beginning of the fixed array.
-  iterator begin() { return data(); }
+  iterator begin() ABSL_ATTRIBUTE_LIFETIME_BOUND { return data(); }
 
   // Overload of FixedArray::begin() to return a const iterator to the
   // beginning of the fixed array.
-  const_iterator begin() const { return data(); }
+  const_iterator begin() const ABSL_ATTRIBUTE_LIFETIME_BOUND { return data(); }
 
   // FixedArray::cbegin()
   //
   // Returns a const iterator to the beginning of the fixed array.
-  const_iterator cbegin() const { return begin(); }
+  const_iterator cbegin() const ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return begin();
+  }
 
   // FixedArray::end()
   //
   // Returns an iterator to the end of the fixed array.
-  iterator end() { return data() + size(); }
+  iterator end() ABSL_ATTRIBUTE_LIFETIME_BOUND { return data() + size(); }
 
   // Overload of FixedArray::end() to return a const iterator to the end of the
   // fixed array.
-  const_iterator end() const { return data() + size(); }
+  const_iterator end() const ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return data() + size();
+  }
 
   // FixedArray::cend()
   //
   // Returns a const iterator to the end of the fixed array.
-  const_iterator cend() const { return end(); }
+  const_iterator cend() const ABSL_ATTRIBUTE_LIFETIME_BOUND { return end(); }
 
   // FixedArray::rbegin()
   //
   // Returns a reverse iterator from the end of the fixed array.
-  reverse_iterator rbegin() { return reverse_iterator(end()); }
+  reverse_iterator rbegin() ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return reverse_iterator(end());
+  }
 
   // Overload of FixedArray::rbegin() to return a const reverse iterator from
   // the end of the fixed array.
-  const_reverse_iterator rbegin() const {
+  const_reverse_iterator rbegin() const ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return const_reverse_iterator(end());
   }
 
   // FixedArray::crbegin()
   //
   // Returns a const reverse iterator from the end of the fixed array.
-  const_reverse_iterator crbegin() const { return rbegin(); }
+  const_reverse_iterator crbegin() const ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return rbegin();
+  }
 
   // FixedArray::rend()
   //
   // Returns a reverse iterator from the beginning of the fixed array.
-  reverse_iterator rend() { return reverse_iterator(begin()); }
+  reverse_iterator rend() ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return reverse_iterator(begin());
+  }
 
   // Overload of FixedArray::rend() for returning a const reverse iterator
   // from the beginning of the fixed array.
-  const_reverse_iterator rend() const {
+  const_reverse_iterator rend() const ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return const_reverse_iterator(begin());
   }
 
   // FixedArray::crend()
   //
   // Returns a reverse iterator from the beginning of the fixed array.
-  const_reverse_iterator crend() const { return rend(); }
+  const_reverse_iterator crend() const ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return rend();
+  }
 
   // FixedArray::fill()
   //
@@ -342,7 +364,7 @@ class FixedArray {
   // Relational operators. Equality operators are elementwise using
   // `operator==`, while order operators order FixedArrays lexicographically.
   friend bool operator==(const FixedArray& lhs, const FixedArray& rhs) {
-    return absl::equal(lhs.begin(), lhs.end(), rhs.begin(), rhs.end());
+    return std::equal(lhs.begin(), lhs.end(), rhs.begin(), rhs.end());
   }
 
   friend bool operator!=(const FixedArray& lhs, const FixedArray& rhs) {
@@ -464,6 +486,9 @@ class FixedArray {
     StorageElement* begin() const { return data_; }
     StorageElement* end() const { return begin() + size(); }
     allocator_type& alloc() { return size_alloc_.template get<1>(); }
+    const allocator_type& alloc() const {
+      return size_alloc_.template get<1>();
+    }
 
    private:
     static bool UsingInlinedStorage(size_type n) {
diff --git a/absl/container/fixed_array_test.cc b/absl/container/fixed_array_test.cc
index 49598e7a..9dbf2a84 100644
--- a/absl/container/fixed_array_test.cc
+++ b/absl/container/fixed_array_test.cc
@@ -768,6 +768,22 @@ TEST(AllocatorSupportTest, SizeValAllocConstructor) {
   }
 }
 
+TEST(AllocatorSupportTest, PropagatesStatefulAllocator) {
+  constexpr size_t inlined_size = 4;
+  using Alloc = absl::container_internal::CountingAllocator<int>;
+  using AllocFxdArr = absl::FixedArray<int, inlined_size, Alloc>;
+
+  auto len = inlined_size * 2;
+  auto val = 0;
+  int64_t allocated = 0;
+  AllocFxdArr arr(len, val, Alloc(&allocated));
+
+  EXPECT_EQ(allocated, len * sizeof(int));
+
+  AllocFxdArr copy = arr;
+  EXPECT_EQ(allocated, len * sizeof(int) * 2);
+}
+
 #ifdef ABSL_HAVE_ADDRESS_SANITIZER
 TEST(FixedArrayTest, AddressSanitizerAnnotations1) {
   absl::FixedArray<int, 32> a(10);
diff --git a/absl/container/flat_hash_map.h b/absl/container/flat_hash_map.h
index e6bdbd9e..8f4d9939 100644
--- a/absl/container/flat_hash_map.h
+++ b/absl/container/flat_hash_map.h
@@ -235,7 +235,11 @@ class flat_hash_map : public absl::container_internal::raw_hash_map<
   // iterator erase(const_iterator first, const_iterator last):
   //
   //   Erases the elements in the open interval [`first`, `last`), returning an
-  //   iterator pointing to `last`.
+  //   iterator pointing to `last`. The special case of calling
+  //   `erase(begin(), end())` resets the reserved growth such that if
+  //   `reserve(N)` has previously been called and there has been no intervening
+  //   call to `clear()`, then after calling `erase(begin(), end())`, it is safe
+  //   to assume that inserting N elements will not cause a rehash.
   //
   // size_type erase(const key_type& key):
   //
diff --git a/absl/container/flat_hash_map_test.cc b/absl/container/flat_hash_map_test.cc
index 03171f6d..e6acbea2 100644
--- a/absl/container/flat_hash_map_test.cc
+++ b/absl/container/flat_hash_map_test.cc
@@ -16,12 +16,12 @@
 
 #include <memory>
 
-#include "absl/base/internal/raw_logging.h"
 #include "absl/container/internal/hash_generator_testing.h"
 #include "absl/container/internal/unordered_map_constructor_test.h"
 #include "absl/container/internal/unordered_map_lookup_test.h"
 #include "absl/container/internal/unordered_map_members_test.h"
 #include "absl/container/internal/unordered_map_modifiers_test.h"
+#include "absl/log/check.h"
 #include "absl/types/any.h"
 
 namespace absl {
@@ -40,10 +40,10 @@ struct BeforeMain {
   BeforeMain() {
     absl::flat_hash_map<int, int> x;
     x.insert({1, 1});
-    ABSL_RAW_CHECK(x.find(0) == x.end(), "x should not contain 0");
+    CHECK(x.find(0) == x.end()) << "x should not contain 0";
     auto it = x.find(1);
-    ABSL_RAW_CHECK(it != x.end(), "x should contain 1");
-    ABSL_RAW_CHECK(it->second, "1 should map to 1");
+    CHECK(it != x.end()) << "x should contain 1";
+    CHECK(it->second) << "1 should map to 1";
   }
 };
 const BeforeMain before_main;
diff --git a/absl/container/flat_hash_set.h b/absl/container/flat_hash_set.h
index f5376f99..c789c7ef 100644
--- a/absl/container/flat_hash_set.h
+++ b/absl/container/flat_hash_set.h
@@ -227,7 +227,11 @@ class flat_hash_set
   // iterator erase(const_iterator first, const_iterator last):
   //
   //   Erases the elements in the open interval [`first`, `last`), returning an
-  //   iterator pointing to `last`.
+  //   iterator pointing to `last`. The special case of calling
+  //   `erase(begin(), end())` resets the reserved growth such that if
+  //   `reserve(N)` has previously been called and there has been no intervening
+  //   call to `clear()`, then after calling `erase(begin(), end())`, it is safe
+  //   to assume that inserting N elements will not cause a rehash.
   //
   // size_type erase(const key_type& key):
   //
@@ -343,7 +347,7 @@ class flat_hash_set
   // for the past-the-end iterator, which is invalidated.
   //
   // `swap()` requires that the flat hash set's hashing and key equivalence
-  // functions be Swappable, and are exchaged using unqualified calls to
+  // functions be Swappable, and are exchanged using unqualified calls to
   // non-member `swap()`. If the set's allocator has
   // `std::allocator_traits<allocator_type>::propagate_on_container_swap::value`
   // set to `true`, the allocators are also exchanged using an unqualified call
diff --git a/absl/container/flat_hash_set_test.cc b/absl/container/flat_hash_set_test.cc
index b6a72a20..20130f91 100644
--- a/absl/container/flat_hash_set_test.cc
+++ b/absl/container/flat_hash_set_test.cc
@@ -16,12 +16,12 @@
 
 #include <vector>
 
-#include "absl/base/internal/raw_logging.h"
 #include "absl/container/internal/hash_generator_testing.h"
 #include "absl/container/internal/unordered_set_constructor_test.h"
 #include "absl/container/internal/unordered_set_lookup_test.h"
 #include "absl/container/internal/unordered_set_members_test.h"
 #include "absl/container/internal/unordered_set_modifiers_test.h"
+#include "absl/log/check.h"
 #include "absl/memory/memory.h"
 #include "absl/strings/string_view.h"
 
@@ -42,8 +42,8 @@ struct BeforeMain {
   BeforeMain() {
     absl::flat_hash_set<int> x;
     x.insert(1);
-    ABSL_RAW_CHECK(!x.contains(0), "x should not contain 0");
-    ABSL_RAW_CHECK(x.contains(1), "x should contain 1");
+    CHECK(!x.contains(0)) << "x should not contain 0";
+    CHECK(x.contains(1)) << "x should contain 1";
   }
 };
 const BeforeMain before_main;
diff --git a/absl/container/inlined_vector.h b/absl/container/inlined_vector.h
index 7058f375..04e2c385 100644
--- a/absl/container/inlined_vector.h
+++ b/absl/container/inlined_vector.h
@@ -77,8 +77,6 @@ class InlinedVector {
   template <typename TheA>
   using MoveIterator = inlined_vector_internal::MoveIterator<TheA>;
   template <typename TheA>
-  using IsMemcpyOk = inlined_vector_internal::IsMemcpyOk<TheA>;
-  template <typename TheA>
   using IsMoveAssignOk = inlined_vector_internal::IsMoveAssignOk<TheA>;
 
   template <typename TheA, typename Iterator>
@@ -182,14 +180,23 @@ class InlinedVector {
   // provided `allocator`.
   InlinedVector(const InlinedVector& other, const allocator_type& allocator)
       : storage_(allocator) {
+    // Fast path: if the other vector is empty, there's nothing for us to do.
     if (other.empty()) {
-      // Empty; nothing to do.
-    } else if (IsMemcpyOk<A>::value && !other.storage_.GetIsAllocated()) {
-      // Memcpy-able and do not need allocation.
+      return;
+    }
+
+    // Fast path: if the value type is trivially copy constructible, we know the
+    // allocator doesn't do anything fancy, and there is nothing on the heap
+    // then we know it is legal for us to simply memcpy the other vector's
+    // inlined bytes to form our copy of its elements.
+    if (absl::is_trivially_copy_constructible<value_type>::value &&
+        std::is_same<A, std::allocator<value_type>>::value &&
+        !other.storage_.GetIsAllocated()) {
       storage_.MemcpyFrom(other.storage_);
-    } else {
-      storage_.InitFrom(other.storage_);
+      return;
     }
+
+    storage_.InitFrom(other.storage_);
   }
 
   // Creates an inlined vector by moving in the contents of `other` without
@@ -210,26 +217,38 @@ class InlinedVector {
       absl::allocator_is_nothrow<allocator_type>::value ||
       std::is_nothrow_move_constructible<value_type>::value)
       : storage_(other.storage_.GetAllocator()) {
-    if (IsMemcpyOk<A>::value) {
+    // Fast path: if the value type can be trivially relocated (i.e. moved from
+    // and destroyed), and we know the allocator doesn't do anything fancy, then
+    // it's safe for us to simply adopt the contents of the storage for `other`
+    // and remove its own reference to them. It's as if we had individually
+    // move-constructed each value and then destroyed the original.
+    if (absl::is_trivially_relocatable<value_type>::value &&
+        std::is_same<A, std::allocator<value_type>>::value) {
       storage_.MemcpyFrom(other.storage_);
-
       other.storage_.SetInlinedSize(0);
-    } else if (other.storage_.GetIsAllocated()) {
+      return;
+    }
+
+    // Fast path: if the other vector is on the heap, we can simply take over
+    // its allocation.
+    if (other.storage_.GetIsAllocated()) {
       storage_.SetAllocation({other.storage_.GetAllocatedData(),
                               other.storage_.GetAllocatedCapacity()});
       storage_.SetAllocatedSize(other.storage_.GetSize());
 
       other.storage_.SetInlinedSize(0);
-    } else {
-      IteratorValueAdapter<A, MoveIterator<A>> other_values(
-          MoveIterator<A>(other.storage_.GetInlinedData()));
+      return;
+    }
 
-      inlined_vector_internal::ConstructElements<A>(
-          storage_.GetAllocator(), storage_.GetInlinedData(), other_values,
-          other.storage_.GetSize());
+    // Otherwise we must move each element individually.
+    IteratorValueAdapter<A, MoveIterator<A>> other_values(
+        MoveIterator<A>(other.storage_.GetInlinedData()));
 
-      storage_.SetInlinedSize(other.storage_.GetSize());
-    }
+    inlined_vector_internal::ConstructElements<A>(
+        storage_.GetAllocator(), storage_.GetInlinedData(), other_values,
+        other.storage_.GetSize());
+
+    storage_.SetInlinedSize(other.storage_.GetSize());
   }
 
   // Creates an inlined vector by moving in the contents of `other` with a copy
@@ -244,22 +263,34 @@ class InlinedVector {
       const allocator_type&
           allocator) noexcept(absl::allocator_is_nothrow<allocator_type>::value)
       : storage_(allocator) {
-    if (IsMemcpyOk<A>::value) {
+    // Fast path: if the value type can be trivially relocated (i.e. moved from
+    // and destroyed), and we know the allocator doesn't do anything fancy, then
+    // it's safe for us to simply adopt the contents of the storage for `other`
+    // and remove its own reference to them. It's as if we had individually
+    // move-constructed each value and then destroyed the original.
+    if (absl::is_trivially_relocatable<value_type>::value &&
+        std::is_same<A, std::allocator<value_type>>::value) {
       storage_.MemcpyFrom(other.storage_);
-
       other.storage_.SetInlinedSize(0);
-    } else if ((storage_.GetAllocator() == other.storage_.GetAllocator()) &&
-               other.storage_.GetIsAllocated()) {
+      return;
+    }
+
+    // Fast path: if the other vector is on the heap and shared the same
+    // allocator, we can simply take over its allocation.
+    if ((storage_.GetAllocator() == other.storage_.GetAllocator()) &&
+        other.storage_.GetIsAllocated()) {
       storage_.SetAllocation({other.storage_.GetAllocatedData(),
                               other.storage_.GetAllocatedCapacity()});
       storage_.SetAllocatedSize(other.storage_.GetSize());
 
       other.storage_.SetInlinedSize(0);
-    } else {
-      storage_.Initialize(IteratorValueAdapter<A, MoveIterator<A>>(
-                              MoveIterator<A>(other.data())),
-                          other.size());
+      return;
     }
+
+    // Otherwise we must move each element individually.
+    storage_.Initialize(
+        IteratorValueAdapter<A, MoveIterator<A>>(MoveIterator<A>(other.data())),
+        other.size());
   }
 
   ~InlinedVector() {}
@@ -310,7 +341,7 @@ class InlinedVector {
   // can be used to access and modify the contained elements.
   //
   // NOTE: only elements within [`data()`, `data() + size()`) are valid.
-  pointer data() noexcept {
+  pointer data() noexcept ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return storage_.GetIsAllocated() ? storage_.GetAllocatedData()
                                      : storage_.GetInlinedData();
   }
@@ -320,7 +351,7 @@ class InlinedVector {
   // modify the contained elements.
   //
   // NOTE: only elements within [`data()`, `data() + size()`) are valid.
-  const_pointer data() const noexcept {
+  const_pointer data() const noexcept ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return storage_.GetIsAllocated() ? storage_.GetAllocatedData()
                                      : storage_.GetInlinedData();
   }
@@ -328,14 +359,14 @@ class InlinedVector {
   // `InlinedVector::operator[](...)`
   //
   // Returns a `reference` to the `i`th element of the inlined vector.
-  reference operator[](size_type i) {
+  reference operator[](size_type i) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     ABSL_HARDENING_ASSERT(i < size());
     return data()[i];
   }
 
   // Overload of `InlinedVector::operator[](...)` that returns a
   // `const_reference` to the `i`th element of the inlined vector.
-  const_reference operator[](size_type i) const {
+  const_reference operator[](size_type i) const ABSL_ATTRIBUTE_LIFETIME_BOUND {
     ABSL_HARDENING_ASSERT(i < size());
     return data()[i];
   }
@@ -346,7 +377,7 @@ class InlinedVector {
   //
   // NOTE: if `i` is not within the required range of `InlinedVector::at(...)`,
   // in both debug and non-debug builds, `std::out_of_range` will be thrown.
-  reference at(size_type i) {
+  reference at(size_type i) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     if (ABSL_PREDICT_FALSE(i >= size())) {
       base_internal::ThrowStdOutOfRange(
           "`InlinedVector::at(size_type)` failed bounds check");
@@ -359,7 +390,7 @@ class InlinedVector {
   //
   // NOTE: if `i` is not within the required range of `InlinedVector::at(...)`,
   // in both debug and non-debug builds, `std::out_of_range` will be thrown.
-  const_reference at(size_type i) const {
+  const_reference at(size_type i) const ABSL_ATTRIBUTE_LIFETIME_BOUND {
     if (ABSL_PREDICT_FALSE(i >= size())) {
       base_internal::ThrowStdOutOfRange(
           "`InlinedVector::at(size_type) const` failed bounds check");
@@ -370,14 +401,14 @@ class InlinedVector {
   // `InlinedVector::front()`
   //
   // Returns a `reference` to the first element of the inlined vector.
-  reference front() {
+  reference front() ABSL_ATTRIBUTE_LIFETIME_BOUND {
     ABSL_HARDENING_ASSERT(!empty());
     return data()[0];
   }
 
   // Overload of `InlinedVector::front()` that returns a `const_reference` to
   // the first element of the inlined vector.
-  const_reference front() const {
+  const_reference front() const ABSL_ATTRIBUTE_LIFETIME_BOUND {
     ABSL_HARDENING_ASSERT(!empty());
     return data()[0];
   }
@@ -385,14 +416,14 @@ class InlinedVector {
   // `InlinedVector::back()`
   //
   // Returns a `reference` to the last element of the inlined vector.
-  reference back() {
+  reference back() ABSL_ATTRIBUTE_LIFETIME_BOUND {
     ABSL_HARDENING_ASSERT(!empty());
     return data()[size() - 1];
   }
 
   // Overload of `InlinedVector::back()` that returns a `const_reference` to the
   // last element of the inlined vector.
-  const_reference back() const {
+  const_reference back() const ABSL_ATTRIBUTE_LIFETIME_BOUND {
     ABSL_HARDENING_ASSERT(!empty());
     return data()[size() - 1];
   }
@@ -400,63 +431,82 @@ class InlinedVector {
   // `InlinedVector::begin()`
   //
   // Returns an `iterator` to the beginning of the inlined vector.
-  iterator begin() noexcept { return data(); }
+  iterator begin() noexcept ABSL_ATTRIBUTE_LIFETIME_BOUND { return data(); }
 
   // Overload of `InlinedVector::begin()` that returns a `const_iterator` to
   // the beginning of the inlined vector.
-  const_iterator begin() const noexcept { return data(); }
+  const_iterator begin() const noexcept ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return data();
+  }
 
   // `InlinedVector::end()`
   //
   // Returns an `iterator` to the end of the inlined vector.
-  iterator end() noexcept { return data() + size(); }
+  iterator end() noexcept ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return data() + size();
+  }
 
   // Overload of `InlinedVector::end()` that returns a `const_iterator` to the
   // end of the inlined vector.
-  const_iterator end() const noexcept { return data() + size(); }
+  const_iterator end() const noexcept ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return data() + size();
+  }
 
   // `InlinedVector::cbegin()`
   //
   // Returns a `const_iterator` to the beginning of the inlined vector.
-  const_iterator cbegin() const noexcept { return begin(); }
+  const_iterator cbegin() const noexcept ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return begin();
+  }
 
   // `InlinedVector::cend()`
   //
   // Returns a `const_iterator` to the end of the inlined vector.
-  const_iterator cend() const noexcept { return end(); }
+  const_iterator cend() const noexcept ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return end();
+  }
 
   // `InlinedVector::rbegin()`
   //
   // Returns a `reverse_iterator` from the end of the inlined vector.
-  reverse_iterator rbegin() noexcept { return reverse_iterator(end()); }
+  reverse_iterator rbegin() noexcept ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return reverse_iterator(end());
+  }
 
   // Overload of `InlinedVector::rbegin()` that returns a
   // `const_reverse_iterator` from the end of the inlined vector.
-  const_reverse_iterator rbegin() const noexcept {
+  const_reverse_iterator rbegin() const noexcept ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return const_reverse_iterator(end());
   }
 
   // `InlinedVector::rend()`
   //
   // Returns a `reverse_iterator` from the beginning of the inlined vector.
-  reverse_iterator rend() noexcept { return reverse_iterator(begin()); }
+  reverse_iterator rend() noexcept ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return reverse_iterator(begin());
+  }
 
   // Overload of `InlinedVector::rend()` that returns a `const_reverse_iterator`
   // from the beginning of the inlined vector.
-  const_reverse_iterator rend() const noexcept {
+  const_reverse_iterator rend() const noexcept ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return const_reverse_iterator(begin());
   }
 
   // `InlinedVector::crbegin()`
   //
   // Returns a `const_reverse_iterator` from the end of the inlined vector.
-  const_reverse_iterator crbegin() const noexcept { return rbegin(); }
+  const_reverse_iterator crbegin() const noexcept
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return rbegin();
+  }
 
   // `InlinedVector::crend()`
   //
   // Returns a `const_reverse_iterator` from the beginning of the inlined
   // vector.
-  const_reverse_iterator crend() const noexcept { return rend(); }
+  const_reverse_iterator crend() const noexcept ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return rend();
+  }
 
   // `InlinedVector::get_allocator()`
   //
@@ -566,20 +616,23 @@ class InlinedVector {
   //
   // Inserts a copy of `v` at `pos`, returning an `iterator` to the newly
   // inserted element.
-  iterator insert(const_iterator pos, const_reference v) {
+  iterator insert(const_iterator pos,
+                  const_reference v) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return emplace(pos, v);
   }
 
   // Overload of `InlinedVector::insert(...)` that inserts `v` at `pos` using
   // move semantics, returning an `iterator` to the newly inserted element.
-  iterator insert(const_iterator pos, value_type&& v) {
+  iterator insert(const_iterator pos,
+                  value_type&& v) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return emplace(pos, std::move(v));
   }
 
   // Overload of `InlinedVector::insert(...)` that inserts `n` contiguous copies
   // of `v` starting at `pos`, returning an `iterator` pointing to the first of
   // the newly inserted elements.
-  iterator insert(const_iterator pos, size_type n, const_reference v) {
+  iterator insert(const_iterator pos, size_type n,
+                  const_reference v) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     ABSL_HARDENING_ASSERT(pos >= begin());
     ABSL_HARDENING_ASSERT(pos <= end());
 
@@ -607,7 +660,8 @@ class InlinedVector {
   // Overload of `InlinedVector::insert(...)` that inserts copies of the
   // elements of `list` starting at `pos`, returning an `iterator` pointing to
   // the first of the newly inserted elements.
-  iterator insert(const_iterator pos, std::initializer_list<value_type> list) {
+  iterator insert(const_iterator pos, std::initializer_list<value_type> list)
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return insert(pos, list.begin(), list.end());
   }
 
@@ -619,7 +673,7 @@ class InlinedVector {
   template <typename ForwardIterator,
             EnableIfAtLeastForwardIterator<ForwardIterator> = 0>
   iterator insert(const_iterator pos, ForwardIterator first,
-                  ForwardIterator last) {
+                  ForwardIterator last) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     ABSL_HARDENING_ASSERT(pos >= begin());
     ABSL_HARDENING_ASSERT(pos <= end());
 
@@ -639,7 +693,8 @@ class InlinedVector {
   // NOTE: this overload is for iterators that are "input" category.
   template <typename InputIterator,
             DisableIfAtLeastForwardIterator<InputIterator> = 0>
-  iterator insert(const_iterator pos, InputIterator first, InputIterator last) {
+  iterator insert(const_iterator pos, InputIterator first,
+                  InputIterator last) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     ABSL_HARDENING_ASSERT(pos >= begin());
     ABSL_HARDENING_ASSERT(pos <= end());
 
@@ -656,7 +711,8 @@ class InlinedVector {
   // Constructs and inserts an element using `args...` in the inlined vector at
   // `pos`, returning an `iterator` pointing to the newly emplaced element.
   template <typename... Args>
-  iterator emplace(const_iterator pos, Args&&... args) {
+  iterator emplace(const_iterator pos,
+                   Args&&... args) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     ABSL_HARDENING_ASSERT(pos >= begin());
     ABSL_HARDENING_ASSERT(pos <= end());
 
@@ -684,7 +740,7 @@ class InlinedVector {
   // Constructs and inserts an element using `args...` in the inlined vector at
   // `end()`, returning a `reference` to the newly emplaced element.
   template <typename... Args>
-  reference emplace_back(Args&&... args) {
+  reference emplace_back(Args&&... args) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return storage_.EmplaceBack(std::forward<Args>(args)...);
   }
 
@@ -714,8 +770,8 @@ class InlinedVector {
   // Erases the element at `pos`, returning an `iterator` pointing to where the
   // erased element was located.
   //
-  // NOTE: may return `end()`, which is not dereferencable.
-  iterator erase(const_iterator pos) {
+  // NOTE: may return `end()`, which is not dereferenceable.
+  iterator erase(const_iterator pos) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     ABSL_HARDENING_ASSERT(pos >= begin());
     ABSL_HARDENING_ASSERT(pos < end());
 
@@ -726,8 +782,9 @@ class InlinedVector {
   // range [`from`, `to`), returning an `iterator` pointing to where the first
   // erased element was located.
   //
-  // NOTE: may return `end()`, which is not dereferencable.
-  iterator erase(const_iterator from, const_iterator to) {
+  // NOTE: may return `end()`, which is not dereferenceable.
+  iterator erase(const_iterator from,
+                 const_iterator to) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     ABSL_HARDENING_ASSERT(from >= begin());
     ABSL_HARDENING_ASSERT(from <= to);
     ABSL_HARDENING_ASSERT(to <= end());
@@ -784,39 +841,70 @@ class InlinedVector {
   friend H AbslHashValue(H h, const absl::InlinedVector<TheT, TheN, TheA>& a);
 
   void MoveAssignment(MemcpyPolicy, InlinedVector&& other) {
+    // Assumption check: we shouldn't be told to use memcpy to implement move
+    // assignment unless we have trivially destructible elements and an
+    // allocator that does nothing fancy.
+    static_assert(absl::is_trivially_destructible<value_type>::value, "");
+    static_assert(std::is_same<A, std::allocator<value_type>>::value, "");
+
+    // Throw away our existing heap allocation, if any. There is no need to
+    // destroy the existing elements one by one because we know they are
+    // trivially destructible.
+    storage_.DeallocateIfAllocated();
+
+    // Adopt the other vector's inline elements or heap allocation.
+    storage_.MemcpyFrom(other.storage_);
+    other.storage_.SetInlinedSize(0);
+  }
+
+  // Destroy our existing elements, if any, and adopt the heap-allocated
+  // elements of the other vector.
+  //
+  // REQUIRES: other.storage_.GetIsAllocated()
+  void DestroyExistingAndAdopt(InlinedVector&& other) {
+    ABSL_HARDENING_ASSERT(other.storage_.GetIsAllocated());
+
     inlined_vector_internal::DestroyAdapter<A>::DestroyElements(
         storage_.GetAllocator(), data(), size());
     storage_.DeallocateIfAllocated();
-    storage_.MemcpyFrom(other.storage_);
 
+    storage_.MemcpyFrom(other.storage_);
     other.storage_.SetInlinedSize(0);
   }
 
   void MoveAssignment(ElementwiseAssignPolicy, InlinedVector&& other) {
+    // Fast path: if the other vector is on the heap then we don't worry about
+    // actually move-assigning each element. Instead we only throw away our own
+    // existing elements and adopt the heap allocation of the other vector.
     if (other.storage_.GetIsAllocated()) {
-      MoveAssignment(MemcpyPolicy{}, std::move(other));
-    } else {
-      storage_.Assign(IteratorValueAdapter<A, MoveIterator<A>>(
-                          MoveIterator<A>(other.storage_.GetInlinedData())),
-                      other.size());
+      DestroyExistingAndAdopt(std::move(other));
+      return;
     }
+
+    storage_.Assign(IteratorValueAdapter<A, MoveIterator<A>>(
+                        MoveIterator<A>(other.storage_.GetInlinedData())),
+                    other.size());
   }
 
   void MoveAssignment(ElementwiseConstructPolicy, InlinedVector&& other) {
+    // Fast path: if the other vector is on the heap then we don't worry about
+    // actually move-assigning each element. Instead we only throw away our own
+    // existing elements and adopt the heap allocation of the other vector.
     if (other.storage_.GetIsAllocated()) {
-      MoveAssignment(MemcpyPolicy{}, std::move(other));
-    } else {
-      inlined_vector_internal::DestroyAdapter<A>::DestroyElements(
-          storage_.GetAllocator(), data(), size());
-      storage_.DeallocateIfAllocated();
-
-      IteratorValueAdapter<A, MoveIterator<A>> other_values(
-          MoveIterator<A>(other.storage_.GetInlinedData()));
-      inlined_vector_internal::ConstructElements<A>(
-          storage_.GetAllocator(), storage_.GetInlinedData(), other_values,
-          other.storage_.GetSize());
-      storage_.SetInlinedSize(other.storage_.GetSize());
+      DestroyExistingAndAdopt(std::move(other));
+      return;
     }
+
+    inlined_vector_internal::DestroyAdapter<A>::DestroyElements(
+        storage_.GetAllocator(), data(), size());
+    storage_.DeallocateIfAllocated();
+
+    IteratorValueAdapter<A, MoveIterator<A>> other_values(
+        MoveIterator<A>(other.storage_.GetInlinedData()));
+    inlined_vector_internal::ConstructElements<A>(
+        storage_.GetAllocator(), storage_.GetInlinedData(), other_values,
+        other.storage_.GetSize());
+    storage_.SetInlinedSize(other.storage_.GetSize());
   }
 
   Storage storage_;
@@ -843,7 +931,7 @@ bool operator==(const absl::InlinedVector<T, N, A>& a,
                 const absl::InlinedVector<T, N, A>& b) {
   auto a_data = a.data();
   auto b_data = b.data();
-  return absl::equal(a_data, a_data + a.size(), b_data, b_data + b.size());
+  return std::equal(a_data, a_data + a.size(), b_data, b_data + b.size());
 }
 
 // `operator!=(...)`
diff --git a/absl/container/inlined_vector_benchmark.cc b/absl/container/inlined_vector_benchmark.cc
index 56a6bfd2..5a04277c 100644
--- a/absl/container/inlined_vector_benchmark.cc
+++ b/absl/container/inlined_vector_benchmark.cc
@@ -66,7 +66,7 @@ void BM_StdVectorFill(benchmark::State& state) {
 BENCHMARK(BM_StdVectorFill)->Range(1, 256);
 
 // The purpose of the next two benchmarks is to verify that
-// absl::InlinedVector is efficient when moving is more efficent than
+// absl::InlinedVector is efficient when moving is more efficient than
 // copying. To do so, we use strings that are larger than the short
 // string optimization.
 bool StringRepresentedInline(std::string s) {
diff --git a/absl/container/inlined_vector_test.cc b/absl/container/inlined_vector_test.cc
index 898b40db..b9a79f5b 100644
--- a/absl/container/inlined_vector_test.cc
+++ b/absl/container/inlined_vector_test.cc
@@ -15,6 +15,7 @@
 #include "absl/container/inlined_vector.h"
 
 #include <algorithm>
+#include <cstddef>
 #include <forward_list>
 #include <iterator>
 #include <list>
@@ -30,12 +31,12 @@
 #include "gtest/gtest.h"
 #include "absl/base/attributes.h"
 #include "absl/base/internal/exception_testing.h"
-#include "absl/base/internal/raw_logging.h"
 #include "absl/base/macros.h"
 #include "absl/base/options.h"
 #include "absl/container/internal/counting_allocator.h"
 #include "absl/container/internal/test_instance_tracker.h"
 #include "absl/hash/hash_testing.h"
+#include "absl/log/check.h"
 #include "absl/memory/memory.h"
 #include "absl/strings/str_cat.h"
 
@@ -51,15 +52,13 @@ using testing::ElementsAre;
 using testing::ElementsAreArray;
 using testing::Eq;
 using testing::Gt;
+using testing::Pointee;
 using testing::Pointwise;
 using testing::PrintToString;
+using testing::SizeIs;
 
 using IntVec = absl::InlinedVector<int, 8>;
 
-MATCHER_P(SizeIs, n, "") {
-  return testing::ExplainMatchResult(n, arg.size(), result_listener);
-}
-
 MATCHER_P(CapacityIs, n, "") {
   return testing::ExplainMatchResult(n, arg.capacity(), result_listener);
 }
@@ -104,13 +103,13 @@ class RefCounted {
   }
 
   void Ref() const {
-    ABSL_RAW_CHECK(count_ != nullptr, "");
+    CHECK_NE(count_, nullptr);
     ++(*count_);
   }
 
   void Unref() const {
     --(*count_);
-    ABSL_RAW_CHECK(*count_ >= 0, "");
+    CHECK_GE(*count_, 0);
   }
 
   int value_;
@@ -262,6 +261,49 @@ TEST(IntVec, Hardened) {
 #endif
 }
 
+// Move construction of a container of unique pointers should work fine, with no
+// leaks, despite the fact that unique pointers are trivially relocatable but
+// not trivially destructible.
+TEST(UniquePtr, MoveConstruct) {
+  for (size_t size = 0; size < 16; ++size) {
+    SCOPED_TRACE(size);
+
+    absl::InlinedVector<std::unique_ptr<size_t>, 2> a;
+    for (size_t i = 0; i < size; ++i) {
+      a.push_back(std::make_unique<size_t>(i));
+    }
+
+    absl::InlinedVector<std::unique_ptr<size_t>, 2> b(std::move(a));
+
+    ASSERT_THAT(b, SizeIs(size));
+    for (size_t i = 0; i < size; ++i) {
+      ASSERT_THAT(b[i], Pointee(i));
+    }
+  }
+}
+
+// Move assignment of a container of unique pointers should work fine, with no
+// leaks, despite the fact that unique pointers are trivially relocatable but
+// not trivially destructible.
+TEST(UniquePtr, MoveAssign) {
+  for (size_t size = 0; size < 16; ++size) {
+    SCOPED_TRACE(size);
+
+    absl::InlinedVector<std::unique_ptr<size_t>, 2> a;
+    for (size_t i = 0; i < size; ++i) {
+      a.push_back(std::make_unique<size_t>(i));
+    }
+
+    absl::InlinedVector<std::unique_ptr<size_t>, 2> b;
+    b = std::move(a);
+
+    ASSERT_THAT(b, SizeIs(size));
+    for (size_t i = 0; i < size; ++i) {
+      ASSERT_THAT(b[i], Pointee(i));
+    }
+  }
+}
+
 // At the end of this test loop, the elements between [erase_begin, erase_end)
 // should have reference counts == 0, and all others elements should have
 // reference counts == 1.
@@ -1579,6 +1621,30 @@ TEST(DynamicVec, DynamicVecCompiles) {
   (void)v;
 }
 
+TEST(DynamicVec, CreateNonEmptyDynamicVec) {
+  DynamicVec v(1);
+  EXPECT_EQ(v.size(), 1u);
+}
+
+TEST(DynamicVec, EmplaceBack) {
+  DynamicVec v;
+  v.emplace_back(Dynamic{});
+  EXPECT_EQ(v.size(), 1u);
+}
+
+TEST(DynamicVec, EmplaceBackAfterHeapAllocation) {
+  DynamicVec v;
+  v.reserve(10);
+  v.emplace_back(Dynamic{});
+  EXPECT_EQ(v.size(), 1u);
+}
+
+TEST(DynamicVec, EmptyIteratorComparison) {
+  DynamicVec v;
+  EXPECT_EQ(v.begin(), v.end());
+  EXPECT_EQ(v.cbegin(), v.cend());
+}
+
 TEST(AllocatorSupportTest, Constructors) {
   using MyAlloc = CountingAllocator<int>;
   using AllocVec = absl::InlinedVector<int, 4, MyAlloc>;
diff --git a/absl/container/internal/btree.h b/absl/container/internal/btree.h
index d734676a..569faa07 100644
--- a/absl/container/internal/btree.h
+++ b/absl/container/internal/btree.h
@@ -86,6 +86,12 @@ namespace container_internal {
 #define ABSL_BTREE_ENABLE_GENERATIONS
 #endif
 
+#ifdef ABSL_BTREE_ENABLE_GENERATIONS
+constexpr bool BtreeGenerationsEnabled() { return true; }
+#else
+constexpr bool BtreeGenerationsEnabled() { return false; }
+#endif
+
 template <typename Compare, typename T, typename U>
 using compare_result_t = absl::result_of_t<const Compare(const T &, const U &)>;
 
@@ -378,12 +384,6 @@ struct common_params : common_policy_traits<SlotPolicy> {
       std::is_same<key_compare, StringBtreeDefaultGreater>::value;
   static constexpr bool kIsKeyCompareTransparent =
       IsTransparent<original_key_compare>::value || kIsKeyCompareStringAdapted;
-  static constexpr bool kEnableGenerations =
-#ifdef ABSL_BTREE_ENABLE_GENERATIONS
-      true;
-#else
-      false;
-#endif
 
   // A type which indicates if we have a key-compare-to functor or a plain old
   // key-compare functor.
@@ -589,7 +589,7 @@ class btree_node {
   constexpr static size_type SizeWithNSlots(size_type n) {
     return layout_type(
                /*parent*/ 1,
-               /*generation*/ params_type::kEnableGenerations ? 1 : 0,
+               /*generation*/ BtreeGenerationsEnabled() ? 1 : 0,
                /*position, start, finish, max_count*/ 4,
                /*slots*/ n,
                /*children*/ 0)
@@ -629,23 +629,22 @@ class btree_node {
   // has this value.
   constexpr static field_type kInternalNodeMaxCount = 0;
 
-  // Leaves can have less than kNodeSlots values.
-  constexpr static layout_type LeafLayout(
-      const size_type slot_count = kNodeSlots) {
+  constexpr static layout_type Layout(const size_type slot_count,
+                                      const size_type child_count) {
     return layout_type(
         /*parent*/ 1,
-        /*generation*/ params_type::kEnableGenerations ? 1 : 0,
+        /*generation*/ BtreeGenerationsEnabled() ? 1 : 0,
         /*position, start, finish, max_count*/ 4,
         /*slots*/ slot_count,
-        /*children*/ 0);
+        /*children*/ child_count);
+  }
+  // Leaves can have less than kNodeSlots values.
+  constexpr static layout_type LeafLayout(
+      const size_type slot_count = kNodeSlots) {
+    return Layout(slot_count, 0);
   }
   constexpr static layout_type InternalLayout() {
-    return layout_type(
-        /*parent*/ 1,
-        /*generation*/ params_type::kEnableGenerations ? 1 : 0,
-        /*position, start, finish, max_count*/ 4,
-        /*slots*/ kNodeSlots,
-        /*children*/ kNodeSlots + 1);
+    return Layout(kNodeSlots, kNodeSlots + 1);
   }
   constexpr static size_type LeafSize(const size_type slot_count = kNodeSlots) {
     return LeafLayout(slot_count).AllocSize();
@@ -729,7 +728,7 @@ class btree_node {
 
   // Gets the root node's generation integer, which is the one used by the tree.
   uint32_t *get_root_generation() const {
-    assert(params_type::kEnableGenerations);
+    assert(BtreeGenerationsEnabled());
     const btree_node *curr = this;
     for (; !curr->is_root(); curr = curr->parent()) continue;
     return const_cast<uint32_t *>(&curr->GetField<1>()[0]);
@@ -737,16 +736,16 @@ class btree_node {
 
   // Returns the generation for iterator validation.
   uint32_t generation() const {
-    return params_type::kEnableGenerations ? *get_root_generation() : 0;
+    return BtreeGenerationsEnabled() ? *get_root_generation() : 0;
   }
   // Updates generation. Should only be called on a root node or during node
   // initialization.
   void set_generation(uint32_t generation) {
-    if (params_type::kEnableGenerations) GetField<1>()[0] = generation;
+    if (BtreeGenerationsEnabled()) GetField<1>()[0] = generation;
   }
   // Updates the generation. We do this whenever the node is mutated.
   void next_generation() {
-    if (params_type::kEnableGenerations) ++*get_root_generation();
+    if (BtreeGenerationsEnabled()) ++*get_root_generation();
   }
 
   // Getters for the key/value at position i in the node.
@@ -763,9 +762,12 @@ class btree_node {
   void clear_child(field_type i) {
     absl::container_internal::SanitizerPoisonObject(&mutable_child(i));
   }
-  void set_child(field_type i, btree_node *c) {
+  void set_child_noupdate_position(field_type i, btree_node *c) {
     absl::container_internal::SanitizerUnpoisonObject(&mutable_child(i));
     mutable_child(i) = c;
+  }
+  void set_child(field_type i, btree_node *c) {
+    set_child_noupdate_position(i, c);
     c->set_position(i);
   }
   void init_child(field_type i, btree_node *c) {
@@ -892,6 +894,38 @@ class btree_node {
     }
   }
 
+  // Returns whether key i is ordered correctly with respect to the other keys
+  // in the node. The motivation here is to detect comparators that violate
+  // transitivity. Note: we only do comparisons of keys on this node rather than
+  // the whole tree so that this is constant time.
+  template <typename Compare>
+  bool is_ordered_correctly(field_type i, const Compare &comp) const {
+    if (std::is_base_of<BtreeTestOnlyCheckedCompareOptOutBase,
+                        Compare>::value ||
+        params_type::kIsKeyCompareStringAdapted) {
+      return true;
+    }
+
+    const auto compare = [&](field_type a, field_type b) {
+      const absl::weak_ordering cmp =
+          compare_internal::do_three_way_comparison(comp, key(a), key(b));
+      return cmp < 0 ? -1 : cmp > 0 ? 1 : 0;
+    };
+    int cmp = -1;
+    constexpr bool kCanHaveEquivKeys =
+        params_type::template can_have_multiple_equivalent_keys<key_type>();
+    for (field_type j = start(); j < finish(); ++j) {
+      if (j == i) {
+        if (cmp > 0) return false;
+        continue;
+      }
+      int new_cmp = compare(j, i);
+      if (new_cmp < cmp || (!kCanHaveEquivKeys && new_cmp == 0)) return false;
+      cmp = new_cmp;
+    }
+    return true;
+  }
+
   // Emplaces a value at position i, shifting all existing values and
   // children at positions >= i to the right by 1.
   template <typename... Args>
@@ -916,18 +950,19 @@ class btree_node {
   void merge(btree_node *src, allocator_type *alloc);
 
   // Node allocation/deletion routines.
-  void init_leaf(field_type max_count, btree_node *parent) {
+  void init_leaf(field_type position, field_type max_count,
+                 btree_node *parent) {
     set_generation(0);
     set_parent(parent);
-    set_position(0);
+    set_position(position);
     set_start(0);
     set_finish(0);
     set_max_count(max_count);
     absl::container_internal::SanitizerPoisonMemoryRegion(
         start_slot(), max_count * sizeof(slot_type));
   }
-  void init_internal(btree_node *parent) {
-    init_leaf(kNodeSlots, parent);
+  void init_internal(field_type position, btree_node *parent) {
+    init_leaf(position, kNodeSlots, parent);
     // Set `max_count` to a sentinel value to indicate that this node is
     // internal.
     set_max_count(kInternalNodeMaxCount);
@@ -1059,9 +1094,9 @@ class btree_iterator_generation_info_enabled {
 class btree_iterator_generation_info_disabled {
  public:
   explicit btree_iterator_generation_info_disabled(uint32_t) {}
-  void update_generation(const void *) {}
-  uint32_t generation() const { return 0; }
-  void assert_valid_generation(const void *) const {}
+  static void update_generation(const void *) {}
+  static uint32_t generation() { return 0; }
+  static void assert_valid_generation(const void *) {}
 };
 
 #ifdef ABSL_BTREE_ENABLE_GENERATIONS
@@ -1507,7 +1542,8 @@ class btree {
 
   // Insert a range of values into the btree.
   template <typename InputIterator>
-  void insert_iterator_multi(InputIterator b, InputIterator e);
+  void insert_iterator_multi(InputIterator b,
+                             InputIterator e);
 
   // Erase the specified iterator from the btree. The iterator must be valid
   // (i.e. not equal to end()).  Return an iterator pointing to the node after
@@ -1663,19 +1699,19 @@ class btree {
   }
 
   // Node creation/deletion routines.
-  node_type *new_internal_node(node_type *parent) {
+  node_type *new_internal_node(field_type position, node_type *parent) {
     node_type *n = allocate(node_type::InternalSize());
-    n->init_internal(parent);
+    n->init_internal(position, parent);
     return n;
   }
-  node_type *new_leaf_node(node_type *parent) {
+  node_type *new_leaf_node(field_type position, node_type *parent) {
     node_type *n = allocate(node_type::LeafSize());
-    n->init_leaf(kNodeSlots, parent);
+    n->init_leaf(position, kNodeSlots, parent);
     return n;
   }
   node_type *new_leaf_root_node(field_type max_count) {
     node_type *n = allocate(node_type::LeafSize(max_count));
-    n->init_leaf(max_count, /*parent=*/n);
+    n->init_leaf(/*position=*/0, max_count, /*parent=*/n);
     return n;
   }
 
@@ -1914,6 +1950,8 @@ void btree_node<P>::split(const int insert_position, btree_node *dest,
                           allocator_type *alloc) {
   assert(dest->count() == 0);
   assert(max_count() == kNodeSlots);
+  assert(position() + 1 == dest->position());
+  assert(parent() == dest->parent());
 
   // We bias the split based on the position being inserted. If we're
   // inserting at the beginning of the left node then bias the split to put
@@ -1936,7 +1974,7 @@ void btree_node<P>::split(const int insert_position, btree_node *dest,
   --mutable_finish();
   parent()->emplace_value(position(), alloc, finish_slot());
   value_destroy(finish(), alloc);
-  parent()->init_child(position() + 1, dest);
+  parent()->set_child_noupdate_position(position() + 1, dest);
 
   if (is_internal()) {
     for (field_type i = dest->start(), j = finish() + 1; i <= dest->finish();
@@ -2180,7 +2218,7 @@ constexpr bool btree<P>::static_assert_validation() {
                 "Key comparison must be nothrow copy constructible");
   static_assert(std::is_nothrow_copy_constructible<allocator_type>::value,
                 "Allocator must be nothrow copy constructible");
-  static_assert(type_traits_internal::is_trivially_copyable<iterator>::value,
+  static_assert(std::is_trivially_copyable<iterator>::value,
                 "iterator not trivially copyable.");
 
   // Note: We assert that kTargetValues, which is computed from
@@ -2653,16 +2691,17 @@ void btree<P>::rebalance_or_split(iterator *iter) {
     // value.
     assert(parent->max_count() == kNodeSlots);
     if (parent->count() == kNodeSlots) {
-      iterator parent_iter(node->parent(), node->position());
+      iterator parent_iter(parent, node->position());
       rebalance_or_split(&parent_iter);
+      parent = node->parent();
     }
   } else {
     // Rebalancing not possible because this is the root node.
     // Create a new root node and set the current root node as the child of the
     // new root.
-    parent = new_internal_node(parent);
+    parent = new_internal_node(/*position=*/0, parent);
     parent->set_generation(root()->generation());
-    parent->init_child(parent->start(), root());
+    parent->init_child(parent->start(), node);
     mutable_root() = parent;
     // If the former root was a leaf node, then it's now the rightmost node.
     assert(parent->start_child()->is_internal() ||
@@ -2672,11 +2711,11 @@ void btree<P>::rebalance_or_split(iterator *iter) {
   // Split the node.
   node_type *split_node;
   if (node->is_leaf()) {
-    split_node = new_leaf_node(parent);
+    split_node = new_leaf_node(node->position() + 1, parent);
     node->split(insert_position, split_node, mutable_allocator());
     if (rightmost() == node) mutable_rightmost() = split_node;
   } else {
-    split_node = new_internal_node(parent);
+    split_node = new_internal_node(node->position() + 1, parent);
     node->split(insert_position, split_node, mutable_allocator());
   }
 
@@ -2792,30 +2831,67 @@ inline auto btree<P>::internal_emplace(iterator iter, Args &&...args)
   }
   const field_type max_count = iter.node_->max_count();
   allocator_type *alloc = mutable_allocator();
+
+  const auto transfer_and_delete = [&](node_type *old_node,
+                                       node_type *new_node) {
+    new_node->transfer_n(old_node->count(), new_node->start(),
+                         old_node->start(), old_node, alloc);
+    new_node->set_finish(old_node->finish());
+    old_node->set_finish(old_node->start());
+    new_node->set_generation(old_node->generation());
+    node_type::clear_and_delete(old_node, alloc);
+  };
+  const auto replace_leaf_root_node = [&](field_type new_node_size) {
+    assert(iter.node_ == root());
+    node_type *old_root = iter.node_;
+    node_type *new_root = iter.node_ = new_leaf_root_node(new_node_size);
+    transfer_and_delete(old_root, new_root);
+    mutable_root() = mutable_rightmost() = new_root;
+  };
+
+  bool replaced_node = false;
   if (iter.node_->count() == max_count) {
     // Make room in the leaf for the new item.
     if (max_count < kNodeSlots) {
       // Insertion into the root where the root is smaller than the full node
       // size. Simply grow the size of the root node.
-      assert(iter.node_ == root());
-      iter.node_ = new_leaf_root_node(static_cast<field_type>(
+      replace_leaf_root_node(static_cast<field_type>(
           (std::min)(static_cast<int>(kNodeSlots), 2 * max_count)));
-      // Transfer the values from the old root to the new root.
-      node_type *old_root = root();
-      node_type *new_root = iter.node_;
-      new_root->transfer_n(old_root->count(), new_root->start(),
-                           old_root->start(), old_root, alloc);
-      new_root->set_finish(old_root->finish());
-      old_root->set_finish(old_root->start());
-      new_root->set_generation(old_root->generation());
-      node_type::clear_and_delete(old_root, alloc);
-      mutable_root() = mutable_rightmost() = new_root;
+      replaced_node = true;
     } else {
       rebalance_or_split(&iter);
     }
   }
+  (void)replaced_node;
+#ifdef ABSL_HAVE_ADDRESS_SANITIZER
+  if (!replaced_node) {
+    assert(iter.node_->is_leaf());
+    if (iter.node_->is_root()) {
+      replace_leaf_root_node(max_count);
+    } else {
+      node_type *old_node = iter.node_;
+      const bool was_rightmost = rightmost() == old_node;
+      const bool was_leftmost = leftmost() == old_node;
+      node_type *parent = old_node->parent();
+      const field_type position = old_node->position();
+      node_type *new_node = iter.node_ = new_leaf_node(position, parent);
+      parent->set_child_noupdate_position(position, new_node);
+      transfer_and_delete(old_node, new_node);
+      if (was_rightmost) mutable_rightmost() = new_node;
+      // The leftmost node is stored as the parent of the root node.
+      if (was_leftmost) root()->set_parent(new_node);
+    }
+  }
+#endif
   iter.node_->emplace_value(static_cast<field_type>(iter.position_), alloc,
                             std::forward<Args>(args)...);
+  assert(
+      iter.node_->is_ordered_correctly(static_cast<field_type>(iter.position_),
+                                       original_key_compare(key_comp())) &&
+      "If this assert fails, then either (1) the comparator may violate "
+      "transitivity, i.e. comp(a,b) && comp(b,c) -> comp(a,c) (see "
+      "https://en.cppreference.com/w/cpp/named_req/Compare), or (2) a "
+      "key may have been mutated after it was inserted into the tree.");
   ++size_;
   iter.update_generation();
   return iter;
diff --git a/absl/container/internal/btree_container.h b/absl/container/internal/btree_container.h
index 2bff11db..a68ce445 100644
--- a/absl/container/internal/btree_container.h
+++ b/absl/container/internal/btree_container.h
@@ -95,18 +95,36 @@ class btree_container {
       std::is_nothrow_move_assignable<Tree>::value) = default;
 
   // Iterator routines.
-  iterator begin() { return tree_.begin(); }
-  const_iterator begin() const { return tree_.begin(); }
-  const_iterator cbegin() const { return tree_.begin(); }
-  iterator end() { return tree_.end(); }
-  const_iterator end() const { return tree_.end(); }
-  const_iterator cend() const { return tree_.end(); }
-  reverse_iterator rbegin() { return tree_.rbegin(); }
-  const_reverse_iterator rbegin() const { return tree_.rbegin(); }
-  const_reverse_iterator crbegin() const { return tree_.rbegin(); }
-  reverse_iterator rend() { return tree_.rend(); }
-  const_reverse_iterator rend() const { return tree_.rend(); }
-  const_reverse_iterator crend() const { return tree_.rend(); }
+  iterator begin() ABSL_ATTRIBUTE_LIFETIME_BOUND { return tree_.begin(); }
+  const_iterator begin() const ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return tree_.begin();
+  }
+  const_iterator cbegin() const ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return tree_.begin();
+  }
+  iterator end() ABSL_ATTRIBUTE_LIFETIME_BOUND { return tree_.end(); }
+  const_iterator end() const ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return tree_.end();
+  }
+  const_iterator cend() const ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return tree_.end();
+  }
+  reverse_iterator rbegin() ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return tree_.rbegin();
+  }
+  const_reverse_iterator rbegin() const ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return tree_.rbegin();
+  }
+  const_reverse_iterator crbegin() const ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return tree_.rbegin();
+  }
+  reverse_iterator rend() ABSL_ATTRIBUTE_LIFETIME_BOUND { return tree_.rend(); }
+  const_reverse_iterator rend() const ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return tree_.rend();
+  }
+  const_reverse_iterator crend() const ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return tree_.rend();
+  }
 
   // Lookup routines.
   template <typename K = key_type>
@@ -115,11 +133,12 @@ class btree_container {
     return equal_range.second - equal_range.first;
   }
   template <typename K = key_type>
-  iterator find(const key_arg<K> &key) {
+  iterator find(const key_arg<K> &key) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return tree_.find(key);
   }
   template <typename K = key_type>
-  const_iterator find(const key_arg<K> &key) const {
+  const_iterator find(const key_arg<K> &key) const
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return tree_.find(key);
   }
   template <typename K = key_type>
@@ -127,28 +146,31 @@ class btree_container {
     return find(key) != end();
   }
   template <typename K = key_type>
-  iterator lower_bound(const key_arg<K> &key) {
+  iterator lower_bound(const key_arg<K> &key) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return tree_.lower_bound(key);
   }
   template <typename K = key_type>
-  const_iterator lower_bound(const key_arg<K> &key) const {
+  const_iterator lower_bound(const key_arg<K> &key) const
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return tree_.lower_bound(key);
   }
   template <typename K = key_type>
-  iterator upper_bound(const key_arg<K> &key) {
+  iterator upper_bound(const key_arg<K> &key) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return tree_.upper_bound(key);
   }
   template <typename K = key_type>
-  const_iterator upper_bound(const key_arg<K> &key) const {
+  const_iterator upper_bound(const key_arg<K> &key) const
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return tree_.upper_bound(key);
   }
   template <typename K = key_type>
-  std::pair<iterator, iterator> equal_range(const key_arg<K> &key) {
+  std::pair<iterator, iterator> equal_range(const key_arg<K> &key)
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return tree_.equal_range(key);
   }
   template <typename K = key_type>
   std::pair<const_iterator, const_iterator> equal_range(
-      const key_arg<K> &key) const {
+      const key_arg<K> &key) const ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return tree_.equal_range(key);
   }
 
@@ -158,9 +180,14 @@ class btree_container {
   // Erase the specified iterator from the btree. The iterator must be valid
   // (i.e. not equal to end()).  Return an iterator pointing to the node after
   // the one that was erased (or end() if none exists).
-  iterator erase(const_iterator iter) { return tree_.erase(iterator(iter)); }
-  iterator erase(iterator iter) { return tree_.erase(iter); }
-  iterator erase(const_iterator first, const_iterator last) {
+  iterator erase(const_iterator iter) ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return tree_.erase(iterator(iter));
+  }
+  iterator erase(iterator iter) ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return tree_.erase(iter);
+  }
+  iterator erase(const_iterator first,
+                 const_iterator last) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return tree_.erase_range(iterator(first), iterator(last)).second;
   }
   template <typename K = key_type>
@@ -170,8 +197,8 @@ class btree_container {
   }
 
   // Extract routines.
-  extract_and_get_next_return_type extract_and_get_next(
-      const_iterator position) {
+  extract_and_get_next_return_type extract_and_get_next(const_iterator position)
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
     // Use Construct instead of Transfer because the rebalancing code will
     // destroy the slot later.
     // Note: we rely on erase() taking place after Construct().
@@ -298,32 +325,38 @@ class btree_set_container : public btree_container<Tree> {
       : btree_set_container(init.begin(), init.end(), alloc) {}
 
   // Insertion routines.
-  std::pair<iterator, bool> insert(const value_type &v) {
+  std::pair<iterator, bool> insert(const value_type &v)
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return this->tree_.insert_unique(params_type::key(v), v);
   }
-  std::pair<iterator, bool> insert(value_type &&v) {
+  std::pair<iterator, bool> insert(value_type &&v)
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return this->tree_.insert_unique(params_type::key(v), std::move(v));
   }
   template <typename... Args>
-  std::pair<iterator, bool> emplace(Args &&... args) {
+  std::pair<iterator, bool> emplace(Args &&...args)
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
     // Use a node handle to manage a temp slot.
     auto node = CommonAccess::Construct<node_type>(this->get_allocator(),
                                                    std::forward<Args>(args)...);
     auto *slot = CommonAccess::GetSlot(node);
     return this->tree_.insert_unique(params_type::key(slot), slot);
   }
-  iterator insert(const_iterator hint, const value_type &v) {
+  iterator insert(const_iterator hint,
+                  const value_type &v) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return this->tree_
         .insert_hint_unique(iterator(hint), params_type::key(v), v)
         .first;
   }
-  iterator insert(const_iterator hint, value_type &&v) {
+  iterator insert(const_iterator hint,
+                  value_type &&v) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return this->tree_
         .insert_hint_unique(iterator(hint), params_type::key(v), std::move(v))
         .first;
   }
   template <typename... Args>
-  iterator emplace_hint(const_iterator hint, Args &&... args) {
+  iterator emplace_hint(const_iterator hint,
+                        Args &&...args) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     // Use a node handle to manage a temp slot.
     auto node = CommonAccess::Construct<node_type>(this->get_allocator(),
                                                    std::forward<Args>(args)...);
@@ -339,7 +372,7 @@ class btree_set_container : public btree_container<Tree> {
   void insert(std::initializer_list<init_type> init) {
     this->tree_.insert_iterator_unique(init.begin(), init.end(), 0);
   }
-  insert_return_type insert(node_type &&node) {
+  insert_return_type insert(node_type &&node) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     if (!node) return {this->end(), false, node_type()};
     std::pair<iterator, bool> res =
         this->tree_.insert_unique(params_type::key(CommonAccess::GetSlot(node)),
@@ -351,7 +384,8 @@ class btree_set_container : public btree_container<Tree> {
       return {res.first, false, std::move(node)};
     }
   }
-  iterator insert(const_iterator hint, node_type &&node) {
+  iterator insert(const_iterator hint,
+                  node_type &&node) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     if (!node) return this->end();
     std::pair<iterator, bool> res = this->tree_.insert_hint_unique(
         iterator(hint), params_type::key(CommonAccess::GetSlot(node)),
@@ -434,37 +468,43 @@ class btree_map_container : public btree_set_container<Tree> {
   // Note: the nullptr template arguments and extra `const M&` overloads allow
   // for supporting bitfield arguments.
   template <typename K = key_type, class M>
-  std::pair<iterator, bool> insert_or_assign(const key_arg<K> &k,
-                                             const M &obj) {
+  std::pair<iterator, bool> insert_or_assign(const key_arg<K> &k, const M &obj)
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return insert_or_assign_impl(k, obj);
   }
   template <typename K = key_type, class M, K * = nullptr>
-  std::pair<iterator, bool> insert_or_assign(key_arg<K> &&k, const M &obj) {
+  std::pair<iterator, bool> insert_or_assign(key_arg<K> &&k, const M &obj)
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return insert_or_assign_impl(std::forward<K>(k), obj);
   }
   template <typename K = key_type, class M, M * = nullptr>
-  std::pair<iterator, bool> insert_or_assign(const key_arg<K> &k, M &&obj) {
+  std::pair<iterator, bool> insert_or_assign(const key_arg<K> &k, M &&obj)
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return insert_or_assign_impl(k, std::forward<M>(obj));
   }
   template <typename K = key_type, class M, K * = nullptr, M * = nullptr>
-  std::pair<iterator, bool> insert_or_assign(key_arg<K> &&k, M &&obj) {
+  std::pair<iterator, bool> insert_or_assign(key_arg<K> &&k, M &&obj)
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return insert_or_assign_impl(std::forward<K>(k), std::forward<M>(obj));
   }
   template <typename K = key_type, class M>
   iterator insert_or_assign(const_iterator hint, const key_arg<K> &k,
-                            const M &obj) {
+                            const M &obj) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return insert_or_assign_hint_impl(hint, k, obj);
   }
   template <typename K = key_type, class M, K * = nullptr>
-  iterator insert_or_assign(const_iterator hint, key_arg<K> &&k, const M &obj) {
+  iterator insert_or_assign(const_iterator hint, key_arg<K> &&k,
+                            const M &obj) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return insert_or_assign_hint_impl(hint, std::forward<K>(k), obj);
   }
   template <typename K = key_type, class M, M * = nullptr>
-  iterator insert_or_assign(const_iterator hint, const key_arg<K> &k, M &&obj) {
+  iterator insert_or_assign(const_iterator hint, const key_arg<K> &k,
+                            M &&obj) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return insert_or_assign_hint_impl(hint, k, std::forward<M>(obj));
   }
   template <typename K = key_type, class M, K * = nullptr, M * = nullptr>
-  iterator insert_or_assign(const_iterator hint, key_arg<K> &&k, M &&obj) {
+  iterator insert_or_assign(const_iterator hint, key_arg<K> &&k,
+                            M &&obj) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return insert_or_assign_hint_impl(hint, std::forward<K>(k),
                                       std::forward<M>(obj));
   }
@@ -472,44 +512,48 @@ class btree_map_container : public btree_set_container<Tree> {
   template <typename K = key_type, typename... Args,
             typename absl::enable_if_t<
                 !std::is_convertible<K, const_iterator>::value, int> = 0>
-  std::pair<iterator, bool> try_emplace(const key_arg<K> &k, Args &&... args) {
+  std::pair<iterator, bool> try_emplace(const key_arg<K> &k, Args &&...args)
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return try_emplace_impl(k, std::forward<Args>(args)...);
   }
   template <typename K = key_type, typename... Args,
             typename absl::enable_if_t<
                 !std::is_convertible<K, const_iterator>::value, int> = 0>
-  std::pair<iterator, bool> try_emplace(key_arg<K> &&k, Args &&... args) {
+  std::pair<iterator, bool> try_emplace(key_arg<K> &&k, Args &&...args)
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return try_emplace_impl(std::forward<K>(k), std::forward<Args>(args)...);
   }
   template <typename K = key_type, typename... Args>
   iterator try_emplace(const_iterator hint, const key_arg<K> &k,
-                       Args &&... args) {
+                       Args &&...args) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return try_emplace_hint_impl(hint, k, std::forward<Args>(args)...);
   }
   template <typename K = key_type, typename... Args>
-  iterator try_emplace(const_iterator hint, key_arg<K> &&k, Args &&... args) {
+  iterator try_emplace(const_iterator hint, key_arg<K> &&k,
+                       Args &&...args) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return try_emplace_hint_impl(hint, std::forward<K>(k),
                                  std::forward<Args>(args)...);
   }
 
   template <typename K = key_type>
-  mapped_type &operator[](const key_arg<K> &k) {
+  mapped_type &operator[](const key_arg<K> &k) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return try_emplace(k).first->second;
   }
   template <typename K = key_type>
-  mapped_type &operator[](key_arg<K> &&k) {
+  mapped_type &operator[](key_arg<K> &&k) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return try_emplace(std::forward<K>(k)).first->second;
   }
 
   template <typename K = key_type>
-  mapped_type &at(const key_arg<K> &key) {
+  mapped_type &at(const key_arg<K> &key) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     auto it = this->find(key);
     if (it == this->end())
       base_internal::ThrowStdOutOfRange("absl::btree_map::at");
     return it->second;
   }
   template <typename K = key_type>
-  const mapped_type &at(const key_arg<K> &key) const {
+  const mapped_type &at(const key_arg<K> &key) const
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
     auto it = this->find(key);
     if (it == this->end())
       base_internal::ThrowStdOutOfRange("absl::btree_map::at");
@@ -600,14 +644,18 @@ class btree_multiset_container : public btree_container<Tree> {
       : btree_multiset_container(init.begin(), init.end(), alloc) {}
 
   // Insertion routines.
-  iterator insert(const value_type &v) { return this->tree_.insert_multi(v); }
-  iterator insert(value_type &&v) {
+  iterator insert(const value_type &v) ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return this->tree_.insert_multi(v);
+  }
+  iterator insert(value_type &&v) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return this->tree_.insert_multi(std::move(v));
   }
-  iterator insert(const_iterator hint, const value_type &v) {
+  iterator insert(const_iterator hint,
+                  const value_type &v) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return this->tree_.insert_hint_multi(iterator(hint), v);
   }
-  iterator insert(const_iterator hint, value_type &&v) {
+  iterator insert(const_iterator hint,
+                  value_type &&v) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return this->tree_.insert_hint_multi(iterator(hint), std::move(v));
   }
   template <typename InputIterator>
@@ -618,21 +666,22 @@ class btree_multiset_container : public btree_container<Tree> {
     this->tree_.insert_iterator_multi(init.begin(), init.end());
   }
   template <typename... Args>
-  iterator emplace(Args &&... args) {
+  iterator emplace(Args &&...args) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     // Use a node handle to manage a temp slot.
     auto node = CommonAccess::Construct<node_type>(this->get_allocator(),
                                                    std::forward<Args>(args)...);
     return this->tree_.insert_multi(CommonAccess::GetSlot(node));
   }
   template <typename... Args>
-  iterator emplace_hint(const_iterator hint, Args &&... args) {
+  iterator emplace_hint(const_iterator hint,
+                        Args &&...args) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     // Use a node handle to manage a temp slot.
     auto node = CommonAccess::Construct<node_type>(this->get_allocator(),
                                                    std::forward<Args>(args)...);
     return this->tree_.insert_hint_multi(iterator(hint),
                                          CommonAccess::GetSlot(node));
   }
-  iterator insert(node_type &&node) {
+  iterator insert(node_type &&node) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     if (!node) return this->end();
     iterator res =
         this->tree_.insert_multi(params_type::key(CommonAccess::GetSlot(node)),
@@ -640,7 +689,8 @@ class btree_multiset_container : public btree_container<Tree> {
     CommonAccess::Destroy(&node);
     return res;
   }
-  iterator insert(const_iterator hint, node_type &&node) {
+  iterator insert(const_iterator hint,
+                  node_type &&node) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     if (!node) return this->end();
     iterator res = this->tree_.insert_hint_multi(
         iterator(hint),
diff --git a/absl/container/internal/common_policy_traits.h b/absl/container/internal/common_policy_traits.h
index b42c9a48..3558a543 100644
--- a/absl/container/internal/common_policy_traits.h
+++ b/absl/container/internal/common_policy_traits.h
@@ -87,7 +87,7 @@ struct common_policy_traits {
   }
 
  private:
-  // To rank the overloads below for overload resoltion. Rank0 is preferred.
+  // To rank the overloads below for overload resolution. Rank0 is preferred.
   struct Rank2 {};
   struct Rank1 : Rank2 {};
   struct Rank0 : Rank1 {};
diff --git a/absl/container/internal/compressed_tuple.h b/absl/container/internal/compressed_tuple.h
index 5ebe1649..59e70eb2 100644
--- a/absl/container/internal/compressed_tuple.h
+++ b/absl/container/internal/compressed_tuple.h
@@ -64,19 +64,6 @@ struct Elem<CompressedTuple<B...>, I>
 template <typename D, size_t I>
 using ElemT = typename Elem<D, I>::type;
 
-// Use the __is_final intrinsic if available. Where it's not available, classes
-// declared with the 'final' specifier cannot be used as CompressedTuple
-// elements.
-// TODO(sbenza): Replace this with std::is_final in C++14.
-template <typename T>
-constexpr bool IsFinal() {
-#if defined(__clang__) || defined(__GNUC__)
-  return __is_final(T);
-#else
-  return false;
-#endif
-}
-
 // We can't use EBCO on other CompressedTuples because that would mean that we
 // derive from multiple Storage<> instantiations with the same I parameter,
 // and potentially from multiple identical Storage<> instantiations.  So anytime
@@ -86,20 +73,15 @@ struct uses_inheritance {};
 
 template <typename T>
 constexpr bool ShouldUseBase() {
-  return std::is_class<T>::value && std::is_empty<T>::value && !IsFinal<T>() &&
+  return std::is_class<T>::value && std::is_empty<T>::value &&
+         !std::is_final<T>::value &&
          !std::is_base_of<uses_inheritance, T>::value;
 }
 
 // The storage class provides two specializations:
 //  - For empty classes, it stores T as a base class.
 //  - For everything else, it stores T as a member.
-template <typename T, size_t I,
-#if defined(_MSC_VER)
-          bool UseBase =
-              ShouldUseBase<typename std::enable_if<true, T>::type>()>
-#else
-          bool UseBase = ShouldUseBase<T>()>
-#endif
+template <typename T, size_t I, bool UseBase = ShouldUseBase<T>()>
 struct Storage {
   T value;
   constexpr Storage() = default;
diff --git a/absl/container/internal/container_memory.h b/absl/container/internal/container_memory.h
index bfa4ff93..f59ca4ee 100644
--- a/absl/container/internal/container_memory.h
+++ b/absl/container/internal/container_memory.h
@@ -165,7 +165,7 @@ decltype(std::declval<F>()(std::declval<T>())) WithConstructed(
       std::forward<F>(f));
 }
 
-// Given arguments of an std::pair's consructor, PairArgs() returns a pair of
+// Given arguments of an std::pair's constructor, PairArgs() returns a pair of
 // tuples with references to the passed arguments. The tuples contain
 // constructor arguments for the first and the second elements of the pair.
 //
diff --git a/absl/container/internal/hash_function_defaults.h b/absl/container/internal/hash_function_defaults.h
index 250e662c..a3613b4b 100644
--- a/absl/container/internal/hash_function_defaults.h
+++ b/absl/container/internal/hash_function_defaults.h
@@ -56,6 +56,10 @@
 #include "absl/strings/cord.h"
 #include "absl/strings/string_view.h"
 
+#ifdef ABSL_HAVE_STD_STRING_VIEW
+#include <string_view>
+#endif
+
 namespace absl {
 ABSL_NAMESPACE_BEGIN
 namespace container_internal {
@@ -107,6 +111,48 @@ struct HashEq<absl::string_view> : StringHashEq {};
 template <>
 struct HashEq<absl::Cord> : StringHashEq {};
 
+#ifdef ABSL_HAVE_STD_STRING_VIEW
+
+template <typename TChar>
+struct BasicStringHash {
+  using is_transparent = void;
+
+  size_t operator()(std::basic_string_view<TChar> v) const {
+    return absl::Hash<std::basic_string_view<TChar>>{}(v);
+  }
+};
+
+template <typename TChar>
+struct BasicStringEq {
+  using is_transparent = void;
+  bool operator()(std::basic_string_view<TChar> lhs,
+                  std::basic_string_view<TChar> rhs) const {
+    return lhs == rhs;
+  }
+};
+
+// Supports heterogeneous lookup for w/u16/u32 string + string_view + char*.
+template <typename TChar>
+struct BasicStringHashEq {
+  using Hash = BasicStringHash<TChar>;
+  using Eq = BasicStringEq<TChar>;
+};
+
+template <>
+struct HashEq<std::wstring> : BasicStringHashEq<wchar_t> {};
+template <>
+struct HashEq<std::wstring_view> : BasicStringHashEq<wchar_t> {};
+template <>
+struct HashEq<std::u16string> : BasicStringHashEq<char16_t> {};
+template <>
+struct HashEq<std::u16string_view> : BasicStringHashEq<char16_t> {};
+template <>
+struct HashEq<std::u32string> : BasicStringHashEq<char32_t> {};
+template <>
+struct HashEq<std::u32string_view> : BasicStringHashEq<char32_t> {};
+
+#endif  // ABSL_HAVE_STD_STRING_VIEW
+
 // Supports heterogeneous lookup for pointers and smart pointers.
 template <class T>
 struct HashEq<T*> {
diff --git a/absl/container/internal/hash_function_defaults_test.cc b/absl/container/internal/hash_function_defaults_test.cc
index 9f0a4c72..c31af3be 100644
--- a/absl/container/internal/hash_function_defaults_test.cc
+++ b/absl/container/internal/hash_function_defaults_test.cc
@@ -24,6 +24,10 @@
 #include "absl/strings/cord_test_helpers.h"
 #include "absl/strings/string_view.h"
 
+#ifdef ABSL_HAVE_STD_STRING_VIEW
+#include <string_view>
+#endif
+
 namespace absl {
 ABSL_NAMESPACE_BEGIN
 namespace container_internal {
@@ -109,6 +113,168 @@ TYPED_TEST(HashString, Works) {
   EXPECT_NE(h, hash(std::string("b")));
 }
 
+TEST(BasicStringViewTest, WStringEqWorks) {
+#ifndef ABSL_HAVE_STD_STRING_VIEW
+  GTEST_SKIP();
+#else
+  hash_default_eq<std::wstring> eq;
+  EXPECT_TRUE(eq(L"a", L"a"));
+  EXPECT_TRUE(eq(L"a", std::wstring_view(L"a")));
+  EXPECT_TRUE(eq(L"a", std::wstring(L"a")));
+  EXPECT_FALSE(eq(L"a", L"b"));
+  EXPECT_FALSE(eq(L"a", std::wstring_view(L"b")));
+  EXPECT_FALSE(eq(L"a", std::wstring(L"b")));
+#endif
+}
+
+TEST(BasicStringViewTest, WStringViewEqWorks) {
+#ifndef ABSL_HAVE_STD_STRING_VIEW
+  GTEST_SKIP();
+#else
+  hash_default_eq<std::wstring_view> eq;
+  EXPECT_TRUE(eq(L"a", L"a"));
+  EXPECT_TRUE(eq(L"a", std::wstring_view(L"a")));
+  EXPECT_TRUE(eq(L"a", std::wstring(L"a")));
+  EXPECT_FALSE(eq(L"a", L"b"));
+  EXPECT_FALSE(eq(L"a", std::wstring_view(L"b")));
+  EXPECT_FALSE(eq(L"a", std::wstring(L"b")));
+#endif
+}
+
+TEST(BasicStringViewTest, U16StringEqWorks) {
+#ifndef ABSL_HAVE_STD_STRING_VIEW
+  GTEST_SKIP();
+#else
+  hash_default_eq<std::u16string> eq;
+  EXPECT_TRUE(eq(u"a", u"a"));
+  EXPECT_TRUE(eq(u"a", std::u16string_view(u"a")));
+  EXPECT_TRUE(eq(u"a", std::u16string(u"a")));
+  EXPECT_FALSE(eq(u"a", u"b"));
+  EXPECT_FALSE(eq(u"a", std::u16string_view(u"b")));
+  EXPECT_FALSE(eq(u"a", std::u16string(u"b")));
+#endif
+}
+
+TEST(BasicStringViewTest, U16StringViewEqWorks) {
+#ifndef ABSL_HAVE_STD_STRING_VIEW
+  GTEST_SKIP();
+#else
+  hash_default_eq<std::u16string_view> eq;
+  EXPECT_TRUE(eq(u"a", u"a"));
+  EXPECT_TRUE(eq(u"a", std::u16string_view(u"a")));
+  EXPECT_TRUE(eq(u"a", std::u16string(u"a")));
+  EXPECT_FALSE(eq(u"a", u"b"));
+  EXPECT_FALSE(eq(u"a", std::u16string_view(u"b")));
+  EXPECT_FALSE(eq(u"a", std::u16string(u"b")));
+#endif
+}
+
+TEST(BasicStringViewTest, U32StringEqWorks) {
+#ifndef ABSL_HAVE_STD_STRING_VIEW
+  GTEST_SKIP();
+#else
+  hash_default_eq<std::u32string> eq;
+  EXPECT_TRUE(eq(U"a", U"a"));
+  EXPECT_TRUE(eq(U"a", std::u32string_view(U"a")));
+  EXPECT_TRUE(eq(U"a", std::u32string(U"a")));
+  EXPECT_FALSE(eq(U"a", U"b"));
+  EXPECT_FALSE(eq(U"a", std::u32string_view(U"b")));
+  EXPECT_FALSE(eq(U"a", std::u32string(U"b")));
+#endif
+}
+
+TEST(BasicStringViewTest, U32StringViewEqWorks) {
+#ifndef ABSL_HAVE_STD_STRING_VIEW
+  GTEST_SKIP();
+#else
+  hash_default_eq<std::u32string_view> eq;
+  EXPECT_TRUE(eq(U"a", U"a"));
+  EXPECT_TRUE(eq(U"a", std::u32string_view(U"a")));
+  EXPECT_TRUE(eq(U"a", std::u32string(U"a")));
+  EXPECT_FALSE(eq(U"a", U"b"));
+  EXPECT_FALSE(eq(U"a", std::u32string_view(U"b")));
+  EXPECT_FALSE(eq(U"a", std::u32string(U"b")));
+#endif
+}
+
+TEST(BasicStringViewTest, WStringHashWorks) {
+#ifndef ABSL_HAVE_STD_STRING_VIEW
+  GTEST_SKIP();
+#else
+  hash_default_hash<std::wstring> hash;
+  auto h = hash(L"a");
+  EXPECT_EQ(h, hash(std::wstring_view(L"a")));
+  EXPECT_EQ(h, hash(std::wstring(L"a")));
+  EXPECT_NE(h, hash(std::wstring_view(L"b")));
+  EXPECT_NE(h, hash(std::wstring(L"b")));
+#endif
+}
+
+TEST(BasicStringViewTest, WStringViewHashWorks) {
+#ifndef ABSL_HAVE_STD_STRING_VIEW
+  GTEST_SKIP();
+#else
+  hash_default_hash<std::wstring_view> hash;
+  auto h = hash(L"a");
+  EXPECT_EQ(h, hash(std::wstring_view(L"a")));
+  EXPECT_EQ(h, hash(std::wstring(L"a")));
+  EXPECT_NE(h, hash(std::wstring_view(L"b")));
+  EXPECT_NE(h, hash(std::wstring(L"b")));
+#endif
+}
+
+TEST(BasicStringViewTest, U16StringHashWorks) {
+#ifndef ABSL_HAVE_STD_STRING_VIEW
+  GTEST_SKIP();
+#else
+  hash_default_hash<std::u16string> hash;
+  auto h = hash(u"a");
+  EXPECT_EQ(h, hash(std::u16string_view(u"a")));
+  EXPECT_EQ(h, hash(std::u16string(u"a")));
+  EXPECT_NE(h, hash(std::u16string_view(u"b")));
+  EXPECT_NE(h, hash(std::u16string(u"b")));
+#endif
+}
+
+TEST(BasicStringViewTest, U16StringViewHashWorks) {
+#ifndef ABSL_HAVE_STD_STRING_VIEW
+  GTEST_SKIP();
+#else
+  hash_default_hash<std::u16string_view> hash;
+  auto h = hash(u"a");
+  EXPECT_EQ(h, hash(std::u16string_view(u"a")));
+  EXPECT_EQ(h, hash(std::u16string(u"a")));
+  EXPECT_NE(h, hash(std::u16string_view(u"b")));
+  EXPECT_NE(h, hash(std::u16string(u"b")));
+#endif
+}
+
+TEST(BasicStringViewTest, U32StringHashWorks) {
+#ifndef ABSL_HAVE_STD_STRING_VIEW
+  GTEST_SKIP();
+#else
+  hash_default_hash<std::u32string> hash;
+  auto h = hash(U"a");
+  EXPECT_EQ(h, hash(std::u32string_view(U"a")));
+  EXPECT_EQ(h, hash(std::u32string(U"a")));
+  EXPECT_NE(h, hash(std::u32string_view(U"b")));
+  EXPECT_NE(h, hash(std::u32string(U"b")));
+#endif
+}
+
+TEST(BasicStringViewTest, U32StringViewHashWorks) {
+#ifndef ABSL_HAVE_STD_STRING_VIEW
+  GTEST_SKIP();
+#else
+  hash_default_hash<std::u32string_view> hash;
+  auto h = hash(U"a");
+  EXPECT_EQ(h, hash(std::u32string_view(U"a")));
+  EXPECT_EQ(h, hash(std::u32string(U"a")));
+  EXPECT_NE(h, hash(std::u32string_view(U"b")));
+  EXPECT_NE(h, hash(std::u32string(U"b")));
+#endif
+}
+
 struct NoDeleter {
   template <class T>
   void operator()(const T* ptr) const {}
diff --git a/absl/container/internal/hashtablez_sampler.cc b/absl/container/internal/hashtablez_sampler.cc
index 6b6d3491..79a0973a 100644
--- a/absl/container/internal/hashtablez_sampler.cc
+++ b/absl/container/internal/hashtablez_sampler.cc
@@ -23,11 +23,13 @@
 
 #include "absl/base/attributes.h"
 #include "absl/base/config.h"
+#include "absl/base/internal/raw_logging.h"
 #include "absl/debugging/stacktrace.h"
 #include "absl/memory/memory.h"
 #include "absl/profiling/internal/exponential_biased.h"
 #include "absl/profiling/internal/sample_recorder.h"
 #include "absl/synchronization/mutex.h"
+#include "absl/time/clock.h"
 #include "absl/utility/utility.h"
 
 namespace absl {
diff --git a/absl/container/internal/inlined_vector.h b/absl/container/internal/inlined_vector.h
index 0398f530..b2a602db 100644
--- a/absl/container/internal/inlined_vector.h
+++ b/absl/container/internal/inlined_vector.h
@@ -77,13 +77,6 @@ using IsAtLeastForwardIterator = std::is_convertible<
     std::forward_iterator_tag>;
 
 template <typename A>
-using IsMemcpyOk =
-    absl::conjunction<std::is_same<A, std::allocator<ValueType<A>>>,
-                      absl::is_trivially_copy_constructible<ValueType<A>>,
-                      absl::is_trivially_copy_assignable<ValueType<A>>,
-                      absl::is_trivially_destructible<ValueType<A>>>;
-
-template <typename A>
 using IsMoveAssignOk = std::is_move_assignable<ValueType<A>>;
 template <typename A>
 using IsSwapOk = absl::type_traits_internal::IsSwappable<ValueType<A>>;
@@ -308,11 +301,36 @@ class Storage {
   struct ElementwiseConstructPolicy {};
 
   using MoveAssignmentPolicy = absl::conditional_t<
-      IsMemcpyOk<A>::value, MemcpyPolicy,
+      // Fast path: if the value type can be trivially move assigned and
+      // destroyed, and we know the allocator doesn't do anything fancy, then
+      // it's safe for us to simply adopt the contents of the storage for
+      // `other` and remove its own reference to them. It's as if we had
+      // individually move-assigned each value and then destroyed the original.
+      absl::conjunction<absl::is_trivially_move_assignable<ValueType<A>>,
+                        absl::is_trivially_destructible<ValueType<A>>,
+                        std::is_same<A, std::allocator<ValueType<A>>>>::value,
+      MemcpyPolicy,
+      // Otherwise we use move assignment if possible. If not, we simulate
+      // move assignment using move construction.
+      //
+      // Note that this is in contrast to e.g. std::vector and std::optional,
+      // which are themselves not move-assignable when their contained type is
+      // not.
       absl::conditional_t<IsMoveAssignOk<A>::value, ElementwiseAssignPolicy,
                           ElementwiseConstructPolicy>>;
-  using SwapPolicy = absl::conditional_t<
-      IsMemcpyOk<A>::value, MemcpyPolicy,
+
+  // The policy to be used specifically when swapping inlined elements.
+  using SwapInlinedElementsPolicy = absl::conditional_t<
+      // Fast path: if the value type can be trivially move constructed/assigned
+      // and destroyed, and we know the allocator doesn't do anything fancy,
+      // then it's safe for us to simply swap the bytes in the inline storage.
+      // It's as if we had move-constructed a temporary vector, move-assigned
+      // one to the other, then move-assigned the first from the temporary.
+      absl::conjunction<absl::is_trivially_move_constructible<ValueType<A>>,
+                        absl::is_trivially_move_assignable<ValueType<A>>,
+                        absl::is_trivially_destructible<ValueType<A>>,
+                        std::is_same<A, std::allocator<ValueType<A>>>>::value,
+      MemcpyPolicy,
       absl::conditional_t<IsSwapOk<A>::value, ElementwiseSwapPolicy,
                           ElementwiseConstructPolicy>>;
 
@@ -335,14 +353,21 @@ class Storage {
       : metadata_(allocator, /* size and is_allocated */ 0u) {}
 
   ~Storage() {
+    // Fast path: if we are empty and not allocated, there's nothing to do.
     if (GetSizeAndIsAllocated() == 0) {
-      // Empty and not allocated; nothing to do.
-    } else if (IsMemcpyOk<A>::value) {
-      // No destructors need to be run; just deallocate if necessary.
+      return;
+    }
+
+    // Fast path: if no destructors need to be run and we know the allocator
+    // doesn't do anything fancy, then all we need to do is deallocate (and
+    // maybe not even that).
+    if (absl::is_trivially_destructible<ValueType<A>>::value &&
+        std::is_same<A, std::allocator<ValueType<A>>>::value) {
       DeallocateIfAllocated();
-    } else {
-      DestroyContents();
+      return;
     }
+
+    DestroyContents();
   }
 
   // ---------------------------------------------------------------------------
@@ -365,14 +390,18 @@ class Storage {
     return data_.allocated.allocated_data;
   }
 
-  Pointer<A> GetInlinedData() {
-    return reinterpret_cast<Pointer<A>>(
-        std::addressof(data_.inlined.inlined_data[0]));
+  // ABSL_ATTRIBUTE_NO_SANITIZE_CFI is used because the memory pointed to may be
+  // uninitialized, a common pattern in allocate()+construct() APIs.
+  // https://clang.llvm.org/docs/ControlFlowIntegrity.html#bad-cast-checking
+  // NOTE: When this was written, LLVM documentation did not explicitly
+  // mention that casting `char*` and using `reinterpret_cast` qualifies
+  // as a bad cast.
+  ABSL_ATTRIBUTE_NO_SANITIZE_CFI Pointer<A> GetInlinedData() {
+    return reinterpret_cast<Pointer<A>>(data_.inlined.inlined_data);
   }
 
-  ConstPointer<A> GetInlinedData() const {
-    return reinterpret_cast<ConstPointer<A>>(
-        std::addressof(data_.inlined.inlined_data[0]));
+  ABSL_ATTRIBUTE_NO_SANITIZE_CFI ConstPointer<A> GetInlinedData() const {
+    return reinterpret_cast<ConstPointer<A>>(data_.inlined.inlined_data);
   }
 
   SizeType<A> GetAllocatedCapacity() const {
@@ -461,8 +490,32 @@ class Storage {
   }
 
   void MemcpyFrom(const Storage& other_storage) {
-    ABSL_HARDENING_ASSERT(IsMemcpyOk<A>::value ||
-                          other_storage.GetIsAllocated());
+    // Assumption check: it doesn't make sense to memcpy inlined elements unless
+    // we know the allocator doesn't do anything fancy, and one of the following
+    // holds:
+    //
+    //  *  The elements are trivially relocatable.
+    //
+    //  *  It's possible to trivially assign the elements and then destroy the
+    //     source.
+    //
+    //  *  It's possible to trivially copy construct/assign the elements.
+    //
+    {
+      using V = ValueType<A>;
+      ABSL_HARDENING_ASSERT(
+          other_storage.GetIsAllocated() ||
+          (std::is_same<A, std::allocator<V>>::value &&
+           (
+               // First case above
+               absl::is_trivially_relocatable<V>::value ||
+               // Second case above
+               (absl::is_trivially_move_assignable<V>::value &&
+                absl::is_trivially_destructible<V>::value) ||
+               // Third case above
+               (absl::is_trivially_copy_constructible<V>::value ||
+                absl::is_trivially_copy_assignable<V>::value))));
+    }
 
     GetSizeAndIsAllocated() = other_storage.GetSizeAndIsAllocated();
     data_ = other_storage.data_;
@@ -542,13 +595,19 @@ void Storage<T, N, A>::InitFrom(const Storage& other) {
     dst = allocation.data;
     src = other.GetAllocatedData();
   }
-  if (IsMemcpyOk<A>::value) {
+
+  // Fast path: if the value type is trivially copy constructible and we know
+  // the allocator doesn't do anything fancy, then we know it is legal for us to
+  // simply memcpy the other vector's elements.
+  if (absl::is_trivially_copy_constructible<ValueType<A>>::value &&
+      std::is_same<A, std::allocator<ValueType<A>>>::value) {
     std::memcpy(reinterpret_cast<char*>(dst),
                 reinterpret_cast<const char*>(src), n * sizeof(ValueType<A>));
   } else {
     auto values = IteratorValueAdapter<A, ConstPointer<A>>(src);
     ConstructElements<A>(GetAllocator(), dst, values, n);
   }
+
   GetSizeAndIsAllocated() = other.GetSizeAndIsAllocated();
 }
 
@@ -921,7 +980,7 @@ auto Storage<T, N, A>::Swap(Storage* other_storage_ptr) -> void {
   if (GetIsAllocated() && other_storage_ptr->GetIsAllocated()) {
     swap(data_.allocated, other_storage_ptr->data_.allocated);
   } else if (!GetIsAllocated() && !other_storage_ptr->GetIsAllocated()) {
-    SwapInlinedElements(SwapPolicy{}, other_storage_ptr);
+    SwapInlinedElements(SwapInlinedElementsPolicy{}, other_storage_ptr);
   } else {
     Storage* allocated_ptr = this;
     Storage* inlined_ptr = other_storage_ptr;
@@ -995,7 +1054,7 @@ template <typename NotMemcpyPolicy>
 void Storage<T, N, A>::SwapInlinedElements(NotMemcpyPolicy policy,
                                            Storage* other) {
   // Note: `destroy` needs to use pre-swap allocator while `construct` -
-  // post-swap allocator. Allocators will be swaped later on outside of
+  // post-swap allocator. Allocators will be swapped later on outside of
   // `SwapInlinedElements`.
   Storage* small_ptr = this;
   Storage* large_ptr = other;
diff --git a/absl/container/internal/layout_benchmark.cc b/absl/container/internal/layout_benchmark.cc
index d8636e8d..3af35e33 100644
--- a/absl/container/internal/layout_benchmark.cc
+++ b/absl/container/internal/layout_benchmark.cc
@@ -85,7 +85,7 @@ void BM_OffsetVariable(benchmark::State& state) {
   size_t m = 5;
   size_t k = 7;
   ABSL_RAW_CHECK(L::Partial(n, m, k).template Offset<3>() == Offset,
-                 "Inavlid offset");
+                 "Invalid offset");
   for (auto _ : state) {
     DoNotOptimize(n);
     DoNotOptimize(m);
diff --git a/absl/container/internal/layout_test.cc b/absl/container/internal/layout_test.cc
index 54e5d5bb..ce599ce7 100644
--- a/absl/container/internal/layout_test.cc
+++ b/absl/container/internal/layout_test.cc
@@ -26,7 +26,7 @@
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
 #include "absl/base/config.h"
-#include "absl/base/internal/raw_logging.h"
+#include "absl/log/check.h"
 #include "absl/types/span.h"
 
 namespace absl {
@@ -38,7 +38,7 @@ using ::absl::Span;
 using ::testing::ElementsAre;
 
 size_t Distance(const void* from, const void* to) {
-  ABSL_RAW_CHECK(from <= to, "Distance must be non-negative");
+  CHECK_LE(from, to) << "Distance must be non-negative";
   return static_cast<const char*>(to) - static_cast<const char*>(from);
 }
 
@@ -366,7 +366,7 @@ TEST(Layout, Sizes) {
 }
 
 TEST(Layout, PointerByIndex) {
-  alignas(max_align_t) const unsigned char p[100] = {};
+  alignas(max_align_t) const unsigned char p[100] = {0};
   {
     using L = Layout<int32_t>;
     EXPECT_EQ(0, Distance(p, Type<const int32_t*>(L::Partial().Pointer<0>(p))));
@@ -447,7 +447,7 @@ TEST(Layout, PointerByIndex) {
 }
 
 TEST(Layout, PointerByType) {
-  alignas(max_align_t) const unsigned char p[100] = {};
+  alignas(max_align_t) const unsigned char p[100] = {0};
   {
     using L = Layout<int32_t>;
     EXPECT_EQ(
@@ -526,7 +526,7 @@ TEST(Layout, PointerByType) {
 }
 
 TEST(Layout, MutablePointerByIndex) {
-  alignas(max_align_t) unsigned char p[100];
+  alignas(max_align_t) unsigned char p[100] = {0};
   {
     using L = Layout<int32_t>;
     EXPECT_EQ(0, Distance(p, Type<int32_t*>(L::Partial().Pointer<0>(p))));
@@ -581,7 +581,7 @@ TEST(Layout, MutablePointerByIndex) {
 }
 
 TEST(Layout, MutablePointerByType) {
-  alignas(max_align_t) unsigned char p[100];
+  alignas(max_align_t) unsigned char p[100] = {0};
   {
     using L = Layout<int32_t>;
     EXPECT_EQ(0, Distance(p, Type<int32_t*>(L::Partial().Pointer<int32_t>(p))));
@@ -647,7 +647,7 @@ TEST(Layout, MutablePointerByType) {
 }
 
 TEST(Layout, Pointers) {
-  alignas(max_align_t) const unsigned char p[100] = {};
+  alignas(max_align_t) const unsigned char p[100] = {0};
   using L = Layout<int8_t, int8_t, Int128>;
   {
     const auto x = L::Partial();
@@ -683,7 +683,7 @@ TEST(Layout, Pointers) {
 }
 
 TEST(Layout, MutablePointers) {
-  alignas(max_align_t) unsigned char p[100];
+  alignas(max_align_t) unsigned char p[100] = {0};
   using L = Layout<int8_t, int8_t, Int128>;
   {
     const auto x = L::Partial();
@@ -716,7 +716,7 @@ TEST(Layout, MutablePointers) {
 }
 
 TEST(Layout, SliceByIndexSize) {
-  alignas(max_align_t) const unsigned char p[100] = {};
+  alignas(max_align_t) const unsigned char p[100] = {0};
   {
     using L = Layout<int32_t>;
     EXPECT_EQ(0, L::Partial(0).Slice<0>(p).size());
@@ -744,7 +744,7 @@ TEST(Layout, SliceByIndexSize) {
 }
 
 TEST(Layout, SliceByTypeSize) {
-  alignas(max_align_t) const unsigned char p[100] = {};
+  alignas(max_align_t) const unsigned char p[100] = {0};
   {
     using L = Layout<int32_t>;
     EXPECT_EQ(0, L::Partial(0).Slice<int32_t>(p).size());
@@ -766,7 +766,7 @@ TEST(Layout, SliceByTypeSize) {
 }
 
 TEST(Layout, MutableSliceByIndexSize) {
-  alignas(max_align_t) unsigned char p[100];
+  alignas(max_align_t) unsigned char p[100] = {0};
   {
     using L = Layout<int32_t>;
     EXPECT_EQ(0, L::Partial(0).Slice<0>(p).size());
@@ -794,7 +794,7 @@ TEST(Layout, MutableSliceByIndexSize) {
 }
 
 TEST(Layout, MutableSliceByTypeSize) {
-  alignas(max_align_t) unsigned char p[100];
+  alignas(max_align_t) unsigned char p[100] = {0};
   {
     using L = Layout<int32_t>;
     EXPECT_EQ(0, L::Partial(0).Slice<int32_t>(p).size());
@@ -816,7 +816,7 @@ TEST(Layout, MutableSliceByTypeSize) {
 }
 
 TEST(Layout, SliceByIndexData) {
-  alignas(max_align_t) const unsigned char p[100] = {};
+  alignas(max_align_t) const unsigned char p[100] = {0};
   {
     using L = Layout<int32_t>;
     EXPECT_EQ(
@@ -939,7 +939,7 @@ TEST(Layout, SliceByIndexData) {
 }
 
 TEST(Layout, SliceByTypeData) {
-  alignas(max_align_t) const unsigned char p[100] = {};
+  alignas(max_align_t) const unsigned char p[100] = {0};
   {
     using L = Layout<int32_t>;
     EXPECT_EQ(
@@ -1037,7 +1037,7 @@ TEST(Layout, SliceByTypeData) {
 }
 
 TEST(Layout, MutableSliceByIndexData) {
-  alignas(max_align_t) unsigned char p[100];
+  alignas(max_align_t) unsigned char p[100] = {0};
   {
     using L = Layout<int32_t>;
     EXPECT_EQ(
@@ -1122,7 +1122,7 @@ TEST(Layout, MutableSliceByIndexData) {
 }
 
 TEST(Layout, MutableSliceByTypeData) {
-  alignas(max_align_t) unsigned char p[100];
+  alignas(max_align_t) unsigned char p[100] = {0};
   {
     using L = Layout<int32_t>;
     EXPECT_EQ(
@@ -1268,7 +1268,7 @@ testing::PolymorphicMatcher<TupleMatcher<M...>> Tuple(M... matchers) {
 }
 
 TEST(Layout, Slices) {
-  alignas(max_align_t) const unsigned char p[100] = {};
+  alignas(max_align_t) const unsigned char p[100] = {0};
   using L = Layout<int8_t, int8_t, Int128>;
   {
     const auto x = L::Partial();
@@ -1302,7 +1302,7 @@ TEST(Layout, Slices) {
 }
 
 TEST(Layout, MutableSlices) {
-  alignas(max_align_t) unsigned char p[100] = {};
+  alignas(max_align_t) unsigned char p[100] = {0};
   using L = Layout<int8_t, int8_t, Int128>;
   {
     const auto x = L::Partial();
diff --git a/absl/container/internal/raw_hash_map.h b/absl/container/internal/raw_hash_map.h
index c7df2efc..2d5a8710 100644
--- a/absl/container/internal/raw_hash_map.h
+++ b/absl/container/internal/raw_hash_map.h
@@ -71,43 +71,51 @@ class raw_hash_map : public raw_hash_set<Policy, Hash, Eq, Alloc> {
   //   m.insert_or_assign(n, n);
   template <class K = key_type, class V = mapped_type, K* = nullptr,
             V* = nullptr>
-  std::pair<iterator, bool> insert_or_assign(key_arg<K>&& k, V&& v) {
+  std::pair<iterator, bool> insert_or_assign(key_arg<K>&& k, V&& v)
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return insert_or_assign_impl(std::forward<K>(k), std::forward<V>(v));
   }
 
   template <class K = key_type, class V = mapped_type, K* = nullptr>
-  std::pair<iterator, bool> insert_or_assign(key_arg<K>&& k, const V& v) {
+  std::pair<iterator, bool> insert_or_assign(key_arg<K>&& k, const V& v)
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return insert_or_assign_impl(std::forward<K>(k), v);
   }
 
   template <class K = key_type, class V = mapped_type, V* = nullptr>
-  std::pair<iterator, bool> insert_or_assign(const key_arg<K>& k, V&& v) {
+  std::pair<iterator, bool> insert_or_assign(const key_arg<K>& k, V&& v)
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return insert_or_assign_impl(k, std::forward<V>(v));
   }
 
   template <class K = key_type, class V = mapped_type>
-  std::pair<iterator, bool> insert_or_assign(const key_arg<K>& k, const V& v) {
+  std::pair<iterator, bool> insert_or_assign(const key_arg<K>& k, const V& v)
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return insert_or_assign_impl(k, v);
   }
 
   template <class K = key_type, class V = mapped_type, K* = nullptr,
             V* = nullptr>
-  iterator insert_or_assign(const_iterator, key_arg<K>&& k, V&& v) {
+  iterator insert_or_assign(const_iterator, key_arg<K>&& k,
+                            V&& v) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return insert_or_assign(std::forward<K>(k), std::forward<V>(v)).first;
   }
 
   template <class K = key_type, class V = mapped_type, K* = nullptr>
-  iterator insert_or_assign(const_iterator, key_arg<K>&& k, const V& v) {
+  iterator insert_or_assign(const_iterator, key_arg<K>&& k,
+                            const V& v) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return insert_or_assign(std::forward<K>(k), v).first;
   }
 
   template <class K = key_type, class V = mapped_type, V* = nullptr>
-  iterator insert_or_assign(const_iterator, const key_arg<K>& k, V&& v) {
+  iterator insert_or_assign(const_iterator, const key_arg<K>& k,
+                            V&& v) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return insert_or_assign(k, std::forward<V>(v)).first;
   }
 
   template <class K = key_type, class V = mapped_type>
-  iterator insert_or_assign(const_iterator, const key_arg<K>& k, const V& v) {
+  iterator insert_or_assign(const_iterator, const key_arg<K>& k,
+                            const V& v) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return insert_or_assign(k, v).first;
   }
 
@@ -118,29 +126,33 @@ class raw_hash_map : public raw_hash_set<Policy, Hash, Eq, Alloc> {
             typename std::enable_if<
                 !std::is_convertible<K, const_iterator>::value, int>::type = 0,
             K* = nullptr>
-  std::pair<iterator, bool> try_emplace(key_arg<K>&& k, Args&&... args) {
+  std::pair<iterator, bool> try_emplace(key_arg<K>&& k, Args&&... args)
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return try_emplace_impl(std::forward<K>(k), std::forward<Args>(args)...);
   }
 
   template <class K = key_type, class... Args,
             typename std::enable_if<
                 !std::is_convertible<K, const_iterator>::value, int>::type = 0>
-  std::pair<iterator, bool> try_emplace(const key_arg<K>& k, Args&&... args) {
+  std::pair<iterator, bool> try_emplace(const key_arg<K>& k, Args&&... args)
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return try_emplace_impl(k, std::forward<Args>(args)...);
   }
 
   template <class K = key_type, class... Args, K* = nullptr>
-  iterator try_emplace(const_iterator, key_arg<K>&& k, Args&&... args) {
+  iterator try_emplace(const_iterator, key_arg<K>&& k,
+                       Args&&... args) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return try_emplace(std::forward<K>(k), std::forward<Args>(args)...).first;
   }
 
   template <class K = key_type, class... Args>
-  iterator try_emplace(const_iterator, const key_arg<K>& k, Args&&... args) {
+  iterator try_emplace(const_iterator, const key_arg<K>& k,
+                       Args&&... args) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return try_emplace(k, std::forward<Args>(args)...).first;
   }
 
   template <class K = key_type, class P = Policy>
-  MappedReference<P> at(const key_arg<K>& key) {
+  MappedReference<P> at(const key_arg<K>& key) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     auto it = this->find(key);
     if (it == this->end()) {
       base_internal::ThrowStdOutOfRange(
@@ -150,7 +162,8 @@ class raw_hash_map : public raw_hash_set<Policy, Hash, Eq, Alloc> {
   }
 
   template <class K = key_type, class P = Policy>
-  MappedConstReference<P> at(const key_arg<K>& key) const {
+  MappedConstReference<P> at(const key_arg<K>& key) const
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
     auto it = this->find(key);
     if (it == this->end()) {
       base_internal::ThrowStdOutOfRange(
@@ -160,18 +173,21 @@ class raw_hash_map : public raw_hash_set<Policy, Hash, Eq, Alloc> {
   }
 
   template <class K = key_type, class P = Policy, K* = nullptr>
-  MappedReference<P> operator[](key_arg<K>&& key) {
+  MappedReference<P> operator[](key_arg<K>&& key)
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return Policy::value(&*try_emplace(std::forward<K>(key)).first);
   }
 
   template <class K = key_type, class P = Policy>
-  MappedReference<P> operator[](const key_arg<K>& key) {
+  MappedReference<P> operator[](const key_arg<K>& key)
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return Policy::value(&*try_emplace(key).first);
   }
 
  private:
   template <class K, class V>
-  std::pair<iterator, bool> insert_or_assign_impl(K&& k, V&& v) {
+  std::pair<iterator, bool> insert_or_assign_impl(K&& k, V&& v)
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
     auto res = this->find_or_prepare_insert(k);
     if (res.second)
       this->emplace_at(res.first, std::forward<K>(k), std::forward<V>(v));
@@ -181,7 +197,8 @@ class raw_hash_map : public raw_hash_set<Policy, Hash, Eq, Alloc> {
   }
 
   template <class K = key_type, class... Args>
-  std::pair<iterator, bool> try_emplace_impl(K&& k, Args&&... args) {
+  std::pair<iterator, bool> try_emplace_impl(K&& k, Args&&... args)
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
     auto res = this->find_or_prepare_insert(k);
     if (res.second)
       this->emplace_at(res.first, std::piecewise_construct,
diff --git a/absl/container/internal/raw_hash_set.cc b/absl/container/internal/raw_hash_set.cc
index 3677ac59..2ff95b61 100644
--- a/absl/container/internal/raw_hash_set.cc
+++ b/absl/container/internal/raw_hash_set.cc
@@ -15,34 +15,50 @@
 #include "absl/container/internal/raw_hash_set.h"
 
 #include <atomic>
+#include <cassert>
 #include <cstddef>
 #include <cstring>
 
+#include "absl/base/attributes.h"
 #include "absl/base/config.h"
+#include "absl/base/dynamic_annotations.h"
+#include "absl/hash/hash.h"
 
 namespace absl {
 ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 
-// A single block of empty control bytes for tables without any slots allocated.
-// This enables removing a branch in the hot path of find().
-// We have 17 bytes because there may be a generation counter. Any constant is
-// fine for the generation counter.
-alignas(16) ABSL_CONST_INIT ABSL_DLL const ctrl_t kEmptyGroup[17] = {
+// We have space for `growth_left` before a single block of control bytes. A
+// single block of empty control bytes for tables without any slots allocated.
+// This enables removing a branch in the hot path of find(). In order to ensure
+// that the control bytes are aligned to 16, we have 16 bytes before the control
+// bytes even though growth_left only needs 8.
+constexpr ctrl_t ZeroCtrlT() { return static_cast<ctrl_t>(0); }
+alignas(16) ABSL_CONST_INIT ABSL_DLL const ctrl_t kEmptyGroup[32] = {
+    ZeroCtrlT(),       ZeroCtrlT(),    ZeroCtrlT(),    ZeroCtrlT(),
+    ZeroCtrlT(),       ZeroCtrlT(),    ZeroCtrlT(),    ZeroCtrlT(),
+    ZeroCtrlT(),       ZeroCtrlT(),    ZeroCtrlT(),    ZeroCtrlT(),
+    ZeroCtrlT(),       ZeroCtrlT(),    ZeroCtrlT(),    ZeroCtrlT(),
     ctrl_t::kSentinel, ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty,
     ctrl_t::kEmpty,    ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty,
     ctrl_t::kEmpty,    ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty,
-    ctrl_t::kEmpty,    ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty,
-    static_cast<ctrl_t>(0)};
+    ctrl_t::kEmpty,    ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty};
 
 #ifdef ABSL_INTERNAL_NEED_REDUNDANT_CONSTEXPR_DECL
 constexpr size_t Group::kWidth;
 #endif
 
+namespace {
+
 // Returns "random" seed.
 inline size_t RandomSeed() {
 #ifdef ABSL_HAVE_THREAD_LOCAL
   static thread_local size_t counter = 0;
+  // On Linux kernels >= 5.4 the MSAN runtime has a false-positive when
+  // accessing thread local storage data from loaded libraries
+  // (https://github.com/google/sanitizers/issues/1265), for this reason counter
+  // needs to be annotated as initialized.
+  ABSL_ANNOTATE_MEMORY_IS_INITIALIZED(&counter, sizeof(size_t));
   size_t value = ++counter;
 #else   // ABSL_HAVE_THREAD_LOCAL
   static std::atomic<size_t> counter(0);
@@ -51,6 +67,32 @@ inline size_t RandomSeed() {
   return value ^ static_cast<size_t>(reinterpret_cast<uintptr_t>(&counter));
 }
 
+}  // namespace
+
+GenerationType* EmptyGeneration() {
+  if (SwisstableGenerationsEnabled()) {
+    constexpr size_t kNumEmptyGenerations = 1024;
+    static constexpr GenerationType kEmptyGenerations[kNumEmptyGenerations]{};
+    return const_cast<GenerationType*>(
+        &kEmptyGenerations[RandomSeed() % kNumEmptyGenerations]);
+  }
+  return nullptr;
+}
+
+bool CommonFieldsGenerationInfoEnabled::
+    should_rehash_for_bug_detection_on_insert(const ctrl_t* ctrl,
+                                              size_t capacity) const {
+  if (reserved_growth_ == kReservedGrowthJustRanOut) return true;
+  if (reserved_growth_ > 0) return false;
+  // Note: we can't use the abseil-random library because abseil-random
+  // depends on swisstable. We want to return true with probability
+  // `min(1, RehashProbabilityConstant() / capacity())`. In order to do this,
+  // we probe based on a random hash and see if the offset is less than
+  // RehashProbabilityConstant().
+  return probe(ctrl, capacity, absl::HashOf(RandomSeed())).offset() <
+         RehashProbabilityConstant();
+}
+
 bool ShouldInsertBackwards(size_t hash, const ctrl_t* ctrl) {
   // To avoid problems with weak hashes and single bit tests, we use % 13.
   // TODO(kfm,sbenza): revisit after we do unconditional mixing
@@ -75,21 +117,22 @@ FindInfo find_first_non_full_outofline(const CommonFields& common,
   return find_first_non_full(common, hash);
 }
 
-// Return address of the ith slot in slots where each slot occupies slot_size.
+// Returns the address of the ith slot in slots where each slot occupies
+// slot_size.
 static inline void* SlotAddress(void* slot_array, size_t slot,
                                 size_t slot_size) {
   return reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(slot_array) +
                                  (slot * slot_size));
 }
 
-// Return the address of the slot just after slot assuming each slot
-// has the specified size.
+// Returns the address of the slot just after slot assuming each slot has the
+// specified size.
 static inline void* NextSlot(void* slot, size_t slot_size) {
   return reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(slot) + slot_size);
 }
 
-// Return the address of the slot just before slot assuming each slot
-// has the specified size.
+// Returns the address of the slot just before slot assuming each slot has the
+// specified size.
 static inline void* PrevSlot(void* slot, size_t slot_size) {
   return reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(slot) - slot_size);
 }
@@ -97,8 +140,8 @@ static inline void* PrevSlot(void* slot, size_t slot_size) {
 void DropDeletesWithoutResize(CommonFields& common,
                               const PolicyFunctions& policy, void* tmp_space) {
   void* set = &common;
-  void* slot_array = common.slots_;
-  const size_t capacity = common.capacity_;
+  void* slot_array = common.slot_array();
+  const size_t capacity = common.capacity();
   assert(IsValidCapacity(capacity));
   assert(!is_small(capacity));
   // Algorithm:
@@ -117,7 +160,7 @@ void DropDeletesWithoutResize(CommonFields& common,
   //       swap current element with target element
   //       mark target as FULL
   //       repeat procedure for current slot with moved from element (target)
-  ctrl_t* ctrl = common.control_;
+  ctrl_t* ctrl = common.control();
   ConvertDeletedToEmptyAndFullToDeleted(ctrl, capacity);
   auto hasher = policy.hash_slot;
   auto transfer = policy.transfer;
@@ -177,11 +220,11 @@ void DropDeletesWithoutResize(CommonFields& common,
 
 void EraseMetaOnly(CommonFields& c, ctrl_t* it, size_t slot_size) {
   assert(IsFull(*it) && "erasing a dangling iterator");
-  --c.size_;
-  const auto index = static_cast<size_t>(it - c.control_);
-  const size_t index_before = (index - Group::kWidth) & c.capacity_;
+  c.set_size(c.size() - 1);
+  const auto index = static_cast<size_t>(it - c.control());
+  const size_t index_before = (index - Group::kWidth) & c.capacity();
   const auto empty_after = Group(it).MaskEmpty();
-  const auto empty_before = Group(c.control_ + index_before).MaskEmpty();
+  const auto empty_before = Group(c.control() + index_before).MaskEmpty();
 
   // We count how many consecutive non empties we have to the right and to the
   // left of `it`. If the sum is >= kWidth then there is at least one probe
@@ -193,26 +236,24 @@ void EraseMetaOnly(CommonFields& c, ctrl_t* it, size_t slot_size) {
 
   SetCtrl(c, index, was_never_full ? ctrl_t::kEmpty : ctrl_t::kDeleted,
           slot_size);
-  c.growth_left() += (was_never_full ? 1 : 0);
+  c.set_growth_left(c.growth_left() + (was_never_full ? 1 : 0));
   c.infoz().RecordErase();
 }
 
 void ClearBackingArray(CommonFields& c, const PolicyFunctions& policy,
                        bool reuse) {
-  c.size_ = 0;
+  c.set_size(0);
   if (reuse) {
     ResetCtrl(c, policy.slot_size);
-    c.infoz().RecordStorageChanged(0, c.capacity_);
+    c.infoz().RecordStorageChanged(0, c.capacity());
   } else {
-    void* set = &c;
-    (*policy.dealloc)(set, policy, c.control_, c.slots_, c.capacity_);
-    c.control_ = EmptyGroup();
+    (*policy.dealloc)(c, policy);
+    c.set_control(EmptyGroup());
     c.set_generation_ptr(EmptyGeneration());
-    c.slots_ = nullptr;
-    c.capacity_ = 0;
-    c.growth_left() = 0;
+    c.set_slots(nullptr);
+    c.set_capacity(0);
     c.infoz().RecordClearedReservation();
-    assert(c.size_ == 0);
+    assert(c.size() == 0);
     c.infoz().RecordStorageChanged(0, 0);
   }
 }
diff --git a/absl/container/internal/raw_hash_set.h b/absl/container/internal/raw_hash_set.h
index 61ef196d..5f89d8ef 100644
--- a/absl/container/internal/raw_hash_set.h
+++ b/absl/container/internal/raw_hash_set.h
@@ -62,6 +62,8 @@
 // pseudo-struct:
 //
 //   struct BackingArray {
+//     // The number of elements we can insert before growing the capacity.
+//     size_t growth_left;
 //     // Control bytes for the "real" slots.
 //     ctrl_t ctrl[capacity];
 //     // Always `ctrl_t::kSentinel`. This is used by iterators to find when to
@@ -115,7 +117,7 @@
 // starting with that index and extract potential candidates: occupied slots
 // with a control byte equal to `H2(hash(x))`. If we find an empty slot in the
 // group, we stop and return an error. Each candidate slot `y` is compared with
-// `x`; if `x == y`, we are done and return `&y`; otherwise we contine to the
+// `x`; if `x == y`, we are done and return `&y`; otherwise we continue to the
 // next probe index. Tombstones effectively behave like full slots that never
 // match the value we're looking for.
 //
@@ -174,21 +176,23 @@
 
 #include <algorithm>
 #include <cmath>
+#include <cstddef>
 #include <cstdint>
 #include <cstring>
 #include <iterator>
 #include <limits>
 #include <memory>
+#include <string>
 #include <tuple>
 #include <type_traits>
 #include <utility>
 
 #include "absl/base/config.h"
 #include "absl/base/internal/endian.h"
-#include "absl/base/internal/prefetch.h"
 #include "absl/base/internal/raw_logging.h"
 #include "absl/base/optimization.h"
 #include "absl/base/port.h"
+#include "absl/base/prefetch.h"
 #include "absl/container/internal/common.h"
 #include "absl/container/internal/compressed_tuple.h"
 #include "absl/container/internal/container_memory.h"
@@ -235,6 +239,14 @@ namespace container_internal {
 // We use uint8_t so we don't need to worry about padding.
 using GenerationType = uint8_t;
 
+// A sentinel value for empty generations. Using 0 makes it easy to constexpr
+// initialize an array of this value.
+constexpr GenerationType SentinelEmptyGeneration() { return 0; }
+
+constexpr GenerationType NextGeneration(GenerationType generation) {
+  return ++generation == SentinelEmptyGeneration() ? ++generation : generation;
+}
+
 #ifdef ABSL_SWISSTABLE_ENABLE_GENERATIONS
 constexpr bool SwisstableGenerationsEnabled() { return true; }
 constexpr size_t NumGenerationBytes() { return sizeof(GenerationType); }
@@ -367,12 +379,12 @@ class NonIterableBitMask {
     return static_cast<uint32_t>((bit_width(mask_) - 1) >> Shift);
   }
 
-  // Return the number of trailing zero *abstract* bits.
+  // Returns the number of trailing zero *abstract* bits.
   uint32_t TrailingZeros() const {
     return container_internal::TrailingZeros(mask_) >> Shift;
   }
 
-  // Return the number of leading zero *abstract* bits.
+  // Returns the number of leading zero *abstract* bits.
   uint32_t LeadingZeros() const {
     constexpr int total_significant_bits = SignificantBits << Shift;
     constexpr int extra_bits = sizeof(T) * 8 - total_significant_bits;
@@ -475,19 +487,23 @@ static_assert(ctrl_t::kDeleted == static_cast<ctrl_t>(-2),
               "ctrl_t::kDeleted must be -2 to make the implementation of "
               "ConvertSpecialToEmptyAndFullToDeleted efficient");
 
-ABSL_DLL extern const ctrl_t kEmptyGroup[17];
+// See definition comment for why this is size 32.
+ABSL_DLL extern const ctrl_t kEmptyGroup[32];
 
 // Returns a pointer to a control byte group that can be used by empty tables.
 inline ctrl_t* EmptyGroup() {
   // Const must be cast away here; no uses of this function will actually write
   // to it, because it is only used for empty tables.
-  return const_cast<ctrl_t*>(kEmptyGroup);
+  return const_cast<ctrl_t*>(kEmptyGroup + 16);
 }
 
-// Returns a pointer to the generation byte at the end of the empty group, if it
-// exists.
-inline GenerationType* EmptyGeneration() {
-  return reinterpret_cast<GenerationType*>(EmptyGroup() + 16);
+// Returns a pointer to a generation to use for an empty hashtable.
+GenerationType* EmptyGeneration();
+
+// Returns whether `generation` is a generation for an empty hashtable that
+// could be returned by EmptyGeneration().
+inline bool IsEmptyGeneration(const GenerationType* generation) {
+  return *generation == SentinelEmptyGeneration();
 }
 
 // Mixes a randomly generated per-process seed with `hash` and `ctrl` to
@@ -674,9 +690,10 @@ struct GroupAArch64Impl {
   void ConvertSpecialToEmptyAndFullToDeleted(ctrl_t* dst) const {
     uint64_t mask = vget_lane_u64(vreinterpret_u64_u8(ctrl), 0);
     constexpr uint64_t msbs = 0x8080808080808080ULL;
-    constexpr uint64_t lsbs = 0x0101010101010101ULL;
-    auto x = mask & msbs;
-    auto res = (~x + (x >> 7)) & ~lsbs;
+    constexpr uint64_t slsbs = 0x0202020202020202ULL;
+    constexpr uint64_t midbs = 0x7e7e7e7e7e7e7e7eULL;
+    auto x = slsbs & (mask >> 6);
+    auto res = (x + midbs) | msbs;
     little_endian::Store64(dst, res);
   }
 
@@ -749,6 +766,15 @@ using Group = GroupAArch64Impl;
 using Group = GroupPortableImpl;
 #endif
 
+// When there is an insertion with no reserved growth, we rehash with
+// probability `min(1, RehashProbabilityConstant() / capacity())`. Using a
+// constant divided by capacity ensures that inserting N elements is still O(N)
+// in the average case. Using the constant 16 means that we expect to rehash ~8
+// times more often than when generations are disabled. We are adding expected
+// rehash_probability * #insertions/capacity_growth = 16/capacity * ((7/8 -
+// 7/16) * capacity)/capacity_growth = ~7 extra rehashes per capacity growth.
+inline size_t RehashProbabilityConstant() { return 16; }
+
 class CommonFieldsGenerationInfoEnabled {
   // A sentinel value for reserved_growth_ indicating that we just ran out of
   // reserved growth on the last insertion. When reserve is called and then
@@ -760,8 +786,11 @@ class CommonFieldsGenerationInfoEnabled {
  public:
   CommonFieldsGenerationInfoEnabled() = default;
   CommonFieldsGenerationInfoEnabled(CommonFieldsGenerationInfoEnabled&& that)
-      : reserved_growth_(that.reserved_growth_), generation_(that.generation_) {
+      : reserved_growth_(that.reserved_growth_),
+        reservation_size_(that.reservation_size_),
+        generation_(that.generation_) {
     that.reserved_growth_ = 0;
+    that.reservation_size_ = 0;
     that.generation_ = EmptyGeneration();
   }
   CommonFieldsGenerationInfoEnabled& operator=(
@@ -769,19 +798,17 @@ class CommonFieldsGenerationInfoEnabled {
 
   // Whether we should rehash on insert in order to detect bugs of using invalid
   // references. We rehash on the first insertion after reserved_growth_ reaches
-  // 0 after a call to reserve.
-  // TODO(b/254649633): we could potentially do a rehash with low probability
+  // 0 after a call to reserve. We also do a rehash with low probability
   // whenever reserved_growth_ is zero.
-  bool should_rehash_for_bug_detection_on_insert() const {
-    return reserved_growth_ == kReservedGrowthJustRanOut;
-  }
+  bool should_rehash_for_bug_detection_on_insert(const ctrl_t* ctrl,
+                                                 size_t capacity) const;
   void maybe_increment_generation_on_insert() {
     if (reserved_growth_ == kReservedGrowthJustRanOut) reserved_growth_ = 0;
 
     if (reserved_growth_ > 0) {
       if (--reserved_growth_ == 0) reserved_growth_ = kReservedGrowthJustRanOut;
     } else {
-      ++*generation_;
+      *generation_ = NextGeneration(*generation_);
     }
   }
   void reset_reserved_growth(size_t reservation, size_t size) {
@@ -789,6 +816,8 @@ class CommonFieldsGenerationInfoEnabled {
   }
   size_t reserved_growth() const { return reserved_growth_; }
   void set_reserved_growth(size_t r) { reserved_growth_ = r; }
+  size_t reservation_size() const { return reservation_size_; }
+  void set_reservation_size(size_t r) { reservation_size_ = r; }
   GenerationType generation() const { return *generation_; }
   void set_generation(GenerationType g) { *generation_ = g; }
   GenerationType* generation_ptr() const { return generation_; }
@@ -796,10 +825,14 @@ class CommonFieldsGenerationInfoEnabled {
 
  private:
   // The number of insertions remaining that are guaranteed to not rehash due to
-  // a prior call to reserve. Note: we store reserved growth rather than
+  // a prior call to reserve. Note: we store reserved growth in addition to
   // reservation size because calls to erase() decrease size_ but don't decrease
   // reserved growth.
   size_t reserved_growth_ = 0;
+  // The maximum argument to reserve() since the container was cleared. We need
+  // to keep track of this, in addition to reserved growth, because we reset
+  // reserved growth to this when erase(begin(), end()) is called.
+  size_t reservation_size_ = 0;
   // Pointer to the generation counter, which is used to validate iterators and
   // is stored in the backing array between the control bytes and the slots.
   // Note that we can't store the generation inside the container itself and
@@ -820,11 +853,15 @@ class CommonFieldsGenerationInfoDisabled {
   CommonFieldsGenerationInfoDisabled& operator=(
       CommonFieldsGenerationInfoDisabled&&) = default;
 
-  bool should_rehash_for_bug_detection_on_insert() const { return false; }
+  bool should_rehash_for_bug_detection_on_insert(const ctrl_t*, size_t) const {
+    return false;
+  }
   void maybe_increment_generation_on_insert() {}
   void reset_reserved_growth(size_t, size_t) {}
   size_t reserved_growth() const { return 0; }
   void set_reserved_growth(size_t) {}
+  size_t reservation_size() const { return 0; }
+  void set_reservation_size(size_t) {}
   GenerationType generation() const { return 0; }
   void set_generation(GenerationType) {}
   GenerationType* generation_ptr() const { return nullptr; }
@@ -867,6 +904,44 @@ using CommonFieldsGenerationInfo = CommonFieldsGenerationInfoDisabled;
 using HashSetIteratorGenerationInfo = HashSetIteratorGenerationInfoDisabled;
 #endif
 
+// Returns whether `n` is a valid capacity (i.e., number of slots).
+//
+// A valid capacity is a non-zero integer `2^m - 1`.
+inline bool IsValidCapacity(size_t n) { return ((n + 1) & n) == 0 && n > 0; }
+
+// Computes the offset from the start of the backing allocation of the control
+// bytes. growth_left is stored at the beginning of the backing array.
+inline size_t ControlOffset() { return sizeof(size_t); }
+
+// Returns the number of "cloned control bytes".
+//
+// This is the number of control bytes that are present both at the beginning
+// of the control byte array and at the end, such that we can create a
+// `Group::kWidth`-width probe window starting from any control byte.
+constexpr size_t NumClonedBytes() { return Group::kWidth - 1; }
+
+// Given the capacity of a table, computes the offset (from the start of the
+// backing allocation) of the generation counter (if it exists).
+inline size_t GenerationOffset(size_t capacity) {
+  assert(IsValidCapacity(capacity));
+  const size_t num_control_bytes = capacity + 1 + NumClonedBytes();
+  return ControlOffset() + num_control_bytes;
+}
+
+// Given the capacity of a table, computes the offset (from the start of the
+// backing allocation) at which the slots begin.
+inline size_t SlotOffset(size_t capacity, size_t slot_align) {
+  assert(IsValidCapacity(capacity));
+  return (GenerationOffset(capacity) + NumGenerationBytes() + slot_align - 1) &
+         (~slot_align + 1);
+}
+
+// Given the capacity of a table, computes the total size of the backing
+// array.
+inline size_t AllocSize(size_t capacity, size_t slot_size, size_t slot_align) {
+  return SlotOffset(capacity, slot_align) + capacity * slot_size;
+}
+
 // CommonFields hold the fields in raw_hash_set that do not depend
 // on template parameters. This allows us to conveniently pass all
 // of this state to helper functions as a single argument.
@@ -884,72 +959,102 @@ class CommonFields : public CommonFieldsGenerationInfo {
             std::move(static_cast<CommonFieldsGenerationInfo&&>(that))),
         // Explicitly copying fields into "this" and then resetting "that"
         // fields generates less code then calling absl::exchange per field.
-        control_(that.control_),
-        slots_(that.slots_),
-        size_(that.size_),
-        capacity_(that.capacity_),
-        compressed_tuple_(that.growth_left(), std::move(that.infoz())) {
-    that.control_ = EmptyGroup();
-    that.slots_ = nullptr;
-    that.size_ = 0;
-    that.capacity_ = 0;
-    that.growth_left() = 0;
+        control_(that.control()),
+        slots_(that.slot_array()),
+        capacity_(that.capacity()),
+        compressed_tuple_(that.size(), std::move(that.infoz())) {
+    that.set_control(EmptyGroup());
+    that.set_slots(nullptr);
+    that.set_capacity(0);
+    that.set_size(0);
   }
   CommonFields& operator=(CommonFields&&) = default;
 
+  ctrl_t* control() const { return control_; }
+  void set_control(ctrl_t* c) { control_ = c; }
+  void* backing_array_start() const {
+    // growth_left is stored before control bytes.
+    assert(reinterpret_cast<uintptr_t>(control()) % alignof(size_t) == 0);
+    return control() - sizeof(size_t);
+  }
+
+  // Note: we can't use slots() because Qt defines "slots" as a macro.
+  void* slot_array() const { return slots_; }
+  void set_slots(void* s) { slots_ = s; }
+
+  // The number of filled slots.
+  size_t size() const { return compressed_tuple_.template get<0>(); }
+  void set_size(size_t s) { compressed_tuple_.template get<0>() = s; }
+
+  // The total number of available slots.
+  size_t capacity() const { return capacity_; }
+  void set_capacity(size_t c) {
+    assert(c == 0 || IsValidCapacity(c));
+    capacity_ = c;
+  }
+
   // The number of slots we can still fill without needing to rehash.
-  size_t& growth_left() { return compressed_tuple_.template get<0>(); }
+  // This is stored in the heap allocation before the control bytes.
+  size_t growth_left() const {
+    return *reinterpret_cast<size_t*>(backing_array_start());
+  }
+  void set_growth_left(size_t gl) {
+    *reinterpret_cast<size_t*>(backing_array_start()) = gl;
+  }
 
   HashtablezInfoHandle& infoz() { return compressed_tuple_.template get<1>(); }
   const HashtablezInfoHandle& infoz() const {
     return compressed_tuple_.template get<1>();
   }
 
+  bool should_rehash_for_bug_detection_on_insert() const {
+    return CommonFieldsGenerationInfo::
+        should_rehash_for_bug_detection_on_insert(control(), capacity());
+  }
   void reset_reserved_growth(size_t reservation) {
-    CommonFieldsGenerationInfo::reset_reserved_growth(reservation, size_);
+    CommonFieldsGenerationInfo::reset_reserved_growth(reservation, size());
+  }
+
+  // The size of the backing array allocation.
+  size_t alloc_size(size_t slot_size, size_t slot_align) const {
+    return AllocSize(capacity(), slot_size, slot_align);
   }
 
+  // Returns the number of control bytes set to kDeleted. For testing only.
+  size_t TombstonesCount() const {
+    return static_cast<size_t>(
+        std::count(control(), control() + capacity(), ctrl_t::kDeleted));
+  }
+
+ private:
   // TODO(b/259599413): Investigate removing some of these fields:
   // - control/slots can be derived from each other
-  // - size can be moved into the slot array
+  // - we can use 6 bits for capacity since it's always a power of two minus 1
 
-  // The control bytes (and, also, a pointer to the base of the backing array).
+  // The control bytes (and, also, a pointer near to the base of the backing
+  // array).
   //
   // This contains `capacity + 1 + NumClonedBytes()` entries, even
   // when the table is empty (hence EmptyGroup).
+  //
+  // Note that growth_left is stored immediately before this pointer.
   ctrl_t* control_ = EmptyGroup();
 
   // The beginning of the slots, located at `SlotOffset()` bytes after
   // `control`. May be null for empty tables.
   void* slots_ = nullptr;
 
-  // The number of filled slots.
-  size_t size_ = 0;
-
-  // The total number of available slots.
   size_t capacity_ = 0;
 
-  // Bundle together growth_left and HashtablezInfoHandle to ensure EBO for
+  // Bundle together size and HashtablezInfoHandle to ensure EBO for
   // HashtablezInfoHandle when sampling is turned off.
   absl::container_internal::CompressedTuple<size_t, HashtablezInfoHandle>
       compressed_tuple_{0u, HashtablezInfoHandle{}};
 };
 
-// Returns he number of "cloned control bytes".
-//
-// This is the number of control bytes that are present both at the beginning
-// of the control byte array and at the end, such that we can create a
-// `Group::kWidth`-width probe window starting from any control byte.
-constexpr size_t NumClonedBytes() { return Group::kWidth - 1; }
-
 template <class Policy, class Hash, class Eq, class Alloc>
 class raw_hash_set;
 
-// Returns whether `n` is a valid capacity (i.e., number of slots).
-//
-// A valid capacity is a non-zero integer `2^m - 1`.
-inline bool IsValidCapacity(size_t n) { return ((n + 1) & n) == 0 && n > 0; }
-
 // Returns the next valid capacity after `n`.
 inline size_t NextCapacity(size_t n) {
   assert(IsValidCapacity(n) || n == 0);
@@ -1021,34 +1126,75 @@ size_t SelectBucketCountForIterRange(InputIter first, InputIter last,
   return 0;
 }
 
-#define ABSL_INTERNAL_ASSERT_IS_FULL(ctrl, generation, generation_ptr,         \
-                                     operation)                                \
-  do {                                                                         \
-    ABSL_HARDENING_ASSERT(                                                     \
-        (ctrl != nullptr) && operation                                         \
-        " called on invalid iterator. The iterator might be an end() "         \
-        "iterator or may have been default constructed.");                     \
-    if (SwisstableGenerationsEnabled() && generation != *generation_ptr)       \
-      ABSL_INTERNAL_LOG(FATAL, operation                                       \
-                        " called on invalidated iterator. The table could "    \
-                        "have rehashed since this iterator was initialized."); \
-    ABSL_HARDENING_ASSERT(                                                     \
-        (IsFull(*ctrl)) && operation                                           \
-        " called on invalid iterator. The element might have been erased or "  \
-        "the table might have rehashed.");                                     \
-  } while (0)
+constexpr bool SwisstableDebugEnabled() {
+#if defined(ABSL_SWISSTABLE_ENABLE_GENERATIONS) || \
+    ABSL_OPTION_HARDENED == 1 || !defined(NDEBUG)
+  return true;
+#else
+  return false;
+#endif
+}
+
+inline void AssertIsFull(const ctrl_t* ctrl, GenerationType generation,
+                         const GenerationType* generation_ptr,
+                         const char* operation) {
+  if (!SwisstableDebugEnabled()) return;
+  if (ctrl == nullptr) {
+    ABSL_INTERNAL_LOG(FATAL,
+                      std::string(operation) + " called on end() iterator.");
+  }
+  if (ctrl == EmptyGroup()) {
+    ABSL_INTERNAL_LOG(FATAL, std::string(operation) +
+                                 " called on default-constructed iterator.");
+  }
+  if (SwisstableGenerationsEnabled()) {
+    if (generation != *generation_ptr) {
+      ABSL_INTERNAL_LOG(FATAL,
+                        std::string(operation) +
+                            " called on invalid iterator. The table could have "
+                            "rehashed since this iterator was initialized.");
+    }
+    if (!IsFull(*ctrl)) {
+      ABSL_INTERNAL_LOG(
+          FATAL,
+          std::string(operation) +
+              " called on invalid iterator. The element was likely erased.");
+    }
+  } else {
+    if (!IsFull(*ctrl)) {
+      ABSL_INTERNAL_LOG(
+          FATAL,
+          std::string(operation) +
+              " called on invalid iterator. The element might have been erased "
+              "or the table might have rehashed. Consider running with "
+              "--config=asan to diagnose rehashing issues.");
+    }
+  }
+}
 
 // Note that for comparisons, null/end iterators are valid.
 inline void AssertIsValidForComparison(const ctrl_t* ctrl,
                                        GenerationType generation,
                                        const GenerationType* generation_ptr) {
-  ABSL_HARDENING_ASSERT((ctrl == nullptr || IsFull(*ctrl)) &&
-                        "Invalid iterator comparison. The element might have "
-                        "been erased or the table might have rehashed.");
-  if (SwisstableGenerationsEnabled() && generation != *generation_ptr) {
-    ABSL_INTERNAL_LOG(FATAL,
-                      "Invalid iterator comparison. The table could have "
-                      "rehashed since this iterator was initialized.");
+  if (!SwisstableDebugEnabled()) return;
+  const bool ctrl_is_valid_for_comparison =
+      ctrl == nullptr || ctrl == EmptyGroup() || IsFull(*ctrl);
+  if (SwisstableGenerationsEnabled()) {
+    if (generation != *generation_ptr) {
+      ABSL_INTERNAL_LOG(FATAL,
+                        "Invalid iterator comparison. The table could have "
+                        "rehashed since this iterator was initialized.");
+    }
+    if (!ctrl_is_valid_for_comparison) {
+      ABSL_INTERNAL_LOG(
+          FATAL, "Invalid iterator comparison. The element was likely erased.");
+    }
+  } else {
+    ABSL_HARDENING_ASSERT(
+        ctrl_is_valid_for_comparison &&
+        "Invalid iterator comparison. The element might have been erased or "
+        "the table might have rehashed. Consider running with --config=asan to "
+        "diagnose rehashing issues.");
   }
 }
 
@@ -1074,16 +1220,54 @@ inline bool AreItersFromSameContainer(const ctrl_t* ctrl_a,
 // Asserts that two iterators come from the same container.
 // Note: we take slots by reference so that it's not UB if they're uninitialized
 // as long as we don't read them (when ctrl is null).
-// TODO(b/254649633): when generations are enabled, we can detect more cases of
-// different containers by comparing the pointers to the generations - this
-// can cover cases of end iterators that we would otherwise miss.
 inline void AssertSameContainer(const ctrl_t* ctrl_a, const ctrl_t* ctrl_b,
                                 const void* const& slot_a,
-                                const void* const& slot_b) {
-  ABSL_HARDENING_ASSERT(
-      AreItersFromSameContainer(ctrl_a, ctrl_b, slot_a, slot_b) &&
-      "Invalid iterator comparison. The iterators may be from different "
-      "containers or the container might have rehashed.");
+                                const void* const& slot_b,
+                                const GenerationType* generation_ptr_a,
+                                const GenerationType* generation_ptr_b) {
+  if (!SwisstableDebugEnabled()) return;
+  const bool a_is_default = ctrl_a == EmptyGroup();
+  const bool b_is_default = ctrl_b == EmptyGroup();
+  if (a_is_default != b_is_default) {
+    ABSL_INTERNAL_LOG(
+        FATAL,
+        "Invalid iterator comparison. Comparing default-constructed iterator "
+        "with non-default-constructed iterator.");
+  }
+  if (a_is_default && b_is_default) return;
+
+  if (SwisstableGenerationsEnabled()) {
+    if (generation_ptr_a == generation_ptr_b) return;
+    const bool a_is_empty = IsEmptyGeneration(generation_ptr_a);
+    const bool b_is_empty = IsEmptyGeneration(generation_ptr_b);
+    if (a_is_empty != b_is_empty) {
+      ABSL_INTERNAL_LOG(FATAL,
+                        "Invalid iterator comparison. Comparing iterator from "
+                        "a non-empty hashtable with an iterator from an empty "
+                        "hashtable.");
+    }
+    if (a_is_empty && b_is_empty) {
+      ABSL_INTERNAL_LOG(FATAL,
+                        "Invalid iterator comparison. Comparing iterators from "
+                        "different empty hashtables.");
+    }
+    const bool a_is_end = ctrl_a == nullptr;
+    const bool b_is_end = ctrl_b == nullptr;
+    if (a_is_end || b_is_end) {
+      ABSL_INTERNAL_LOG(FATAL,
+                        "Invalid iterator comparison. Comparing iterator with "
+                        "an end() iterator from a different hashtable.");
+    }
+    ABSL_INTERNAL_LOG(FATAL,
+                      "Invalid iterator comparison. Comparing non-end() "
+                      "iterators from different hashtables.");
+  } else {
+    ABSL_HARDENING_ASSERT(
+        AreItersFromSameContainer(ctrl_a, ctrl_b, slot_a, slot_b) &&
+        "Invalid iterator comparison. The iterators may be from different "
+        "containers or the container might have rehashed. Consider running "
+        "with --config=asan to diagnose rehashing issues.");
+  }
 }
 
 struct FindInfo {
@@ -1106,11 +1290,13 @@ struct FindInfo {
 inline bool is_small(size_t capacity) { return capacity < Group::kWidth - 1; }
 
 // Begins a probing operation on `common.control`, using `hash`.
-inline probe_seq<Group::kWidth> probe(const CommonFields& common, size_t hash) {
-  const ctrl_t* ctrl = common.control_;
-  const size_t capacity = common.capacity_;
+inline probe_seq<Group::kWidth> probe(const ctrl_t* ctrl, const size_t capacity,
+                                      size_t hash) {
   return probe_seq<Group::kWidth>(H1(hash, ctrl), capacity);
 }
+inline probe_seq<Group::kWidth> probe(const CommonFields& common, size_t hash) {
+  return probe(common.control(), common.capacity(), hash);
+}
 
 // Probes an array of control bits using a probe sequence derived from `hash`,
 // and returns the offset corresponding to the first deleted or empty slot.
@@ -1122,7 +1308,7 @@ inline probe_seq<Group::kWidth> probe(const CommonFields& common, size_t hash) {
 template <typename = void>
 inline FindInfo find_first_non_full(const CommonFields& common, size_t hash) {
   auto seq = probe(common, hash);
-  const ctrl_t* ctrl = common.control_;
+  const ctrl_t* ctrl = common.control();
   while (true) {
     Group g{ctrl + seq.offset()};
     auto mask = g.MaskEmptyOrDeleted();
@@ -1132,14 +1318,14 @@ inline FindInfo find_first_non_full(const CommonFields& common, size_t hash) {
       // In debug build we will randomly insert in either the front or back of
       // the group.
       // TODO(kfm,sbenza): revisit after we do unconditional mixing
-      if (!is_small(common.capacity_) && ShouldInsertBackwards(hash, ctrl)) {
+      if (!is_small(common.capacity()) && ShouldInsertBackwards(hash, ctrl)) {
         return {seq.offset(mask.HighestBitSet()), seq.index()};
       }
 #endif
       return {seq.offset(mask.LowestBitSet()), seq.index()};
     }
     seq.next();
-    assert(seq.index() <= common.capacity_ && "full table!");
+    assert(seq.index() <= common.capacity() && "full table!");
   }
 }
 
@@ -1153,18 +1339,18 @@ extern template FindInfo find_first_non_full(const CommonFields&, size_t);
 FindInfo find_first_non_full_outofline(const CommonFields&, size_t);
 
 inline void ResetGrowthLeft(CommonFields& common) {
-  common.growth_left() = CapacityToGrowth(common.capacity_) - common.size_;
+  common.set_growth_left(CapacityToGrowth(common.capacity()) - common.size());
 }
 
 // Sets `ctrl` to `{kEmpty, kSentinel, ..., kEmpty}`, marking the entire
 // array as marked as empty.
 inline void ResetCtrl(CommonFields& common, size_t slot_size) {
-  const size_t capacity = common.capacity_;
-  ctrl_t* ctrl = common.control_;
+  const size_t capacity = common.capacity();
+  ctrl_t* ctrl = common.control();
   std::memset(ctrl, static_cast<int8_t>(ctrl_t::kEmpty),
               capacity + 1 + NumClonedBytes());
   ctrl[capacity] = ctrl_t::kSentinel;
-  SanitizerPoisonMemoryRegion(common.slots_, slot_size * capacity);
+  SanitizerPoisonMemoryRegion(common.slot_array(), slot_size * capacity);
   ResetGrowthLeft(common);
 }
 
@@ -1174,17 +1360,17 @@ inline void ResetCtrl(CommonFields& common, size_t slot_size) {
 // mirror the value to the cloned tail if necessary.
 inline void SetCtrl(const CommonFields& common, size_t i, ctrl_t h,
                     size_t slot_size) {
-  const size_t capacity = common.capacity_;
+  const size_t capacity = common.capacity();
   assert(i < capacity);
 
-  auto* slot_i = static_cast<const char*>(common.slots_) + i * slot_size;
+  auto* slot_i = static_cast<const char*>(common.slot_array()) + i * slot_size;
   if (IsFull(h)) {
     SanitizerUnpoisonMemoryRegion(slot_i, slot_size);
   } else {
     SanitizerPoisonMemoryRegion(slot_i, slot_size);
   }
 
-  ctrl_t* ctrl = common.control_;
+  ctrl_t* ctrl = common.control();
   ctrl[i] = h;
   ctrl[((i - NumClonedBytes()) & capacity) + (NumClonedBytes() & capacity)] = h;
 }
@@ -1195,56 +1381,41 @@ inline void SetCtrl(const CommonFields& common, size_t i, h2_t h,
   SetCtrl(common, i, static_cast<ctrl_t>(h), slot_size);
 }
 
-// Given the capacity of a table, computes the offset (from the start of the
-// backing allocation) of the generation counter (if it exists).
-inline size_t GenerationOffset(size_t capacity) {
-  assert(IsValidCapacity(capacity));
-  const size_t num_control_bytes = capacity + 1 + NumClonedBytes();
-  return num_control_bytes;
-}
-
-// Given the capacity of a table, computes the offset (from the start of the
-// backing allocation) at which the slots begin.
-inline size_t SlotOffset(size_t capacity, size_t slot_align) {
-  assert(IsValidCapacity(capacity));
-  const size_t num_control_bytes = capacity + 1 + NumClonedBytes();
-  return (num_control_bytes + NumGenerationBytes() + slot_align - 1) &
-         (~slot_align + 1);
-}
-
-// Given the capacity of a table, computes the total size of the backing
-// array.
-inline size_t AllocSize(size_t capacity, size_t slot_size, size_t slot_align) {
-  return SlotOffset(capacity, slot_align) + capacity * slot_size;
+// growth_left (which is a size_t) is stored with the backing array.
+constexpr size_t BackingArrayAlignment(size_t align_of_slot) {
+  return (std::max)(align_of_slot, alignof(size_t));
 }
 
 template <typename Alloc, size_t SizeOfSlot, size_t AlignOfSlot>
 ABSL_ATTRIBUTE_NOINLINE void InitializeSlots(CommonFields& c, Alloc alloc) {
-  assert(c.capacity_);
+  assert(c.capacity());
   // Folks with custom allocators often make unwarranted assumptions about the
   // behavior of their classes vis-a-vis trivial destructability and what
   // calls they will or won't make.  Avoid sampling for people with custom
   // allocators to get us out of this mess.  This is not a hard guarantee but
   // a workaround while we plan the exact guarantee we want to provide.
   const size_t sample_size =
-      (std::is_same<Alloc, std::allocator<char>>::value && c.slots_ == nullptr)
+      (std::is_same<Alloc, std::allocator<char>>::value &&
+       c.slot_array() == nullptr)
           ? SizeOfSlot
           : 0;
 
-  const size_t cap = c.capacity_;
+  const size_t cap = c.capacity();
+  const size_t alloc_size = AllocSize(cap, SizeOfSlot, AlignOfSlot);
+  // growth_left (which is a size_t) is stored with the backing array.
   char* mem = static_cast<char*>(
-      Allocate<AlignOfSlot>(&alloc, AllocSize(cap, SizeOfSlot, AlignOfSlot)));
+      Allocate<BackingArrayAlignment(AlignOfSlot)>(&alloc, alloc_size));
   const GenerationType old_generation = c.generation();
   c.set_generation_ptr(
       reinterpret_cast<GenerationType*>(mem + GenerationOffset(cap)));
-  c.set_generation(old_generation + 1);
-  c.control_ = reinterpret_cast<ctrl_t*>(mem);
-  c.slots_ = mem + SlotOffset(cap, AlignOfSlot);
+  c.set_generation(NextGeneration(old_generation));
+  c.set_control(reinterpret_cast<ctrl_t*>(mem + ControlOffset()));
+  c.set_slots(mem + SlotOffset(cap, AlignOfSlot));
   ResetCtrl(c, SizeOfSlot);
   if (sample_size) {
     c.infoz() = Sample(sample_size);
   }
-  c.infoz().RecordStorageChanged(c.size_, cap);
+  c.infoz().RecordStorageChanged(c.size(), cap);
 }
 
 // PolicyFunctions bundles together some information for a particular
@@ -1254,15 +1425,14 @@ ABSL_ATTRIBUTE_NOINLINE void InitializeSlots(CommonFields& c, Alloc alloc) {
 struct PolicyFunctions {
   size_t slot_size;
 
-  // Return the hash of the pointed-to slot.
+  // Returns the hash of the pointed-to slot.
   size_t (*hash_slot)(void* set, void* slot);
 
   // Transfer the contents of src_slot to dst_slot.
   void (*transfer)(void* set, void* dst_slot, void* src_slot);
 
-  // Deallocate the specified backing store which is sized for n slots.
-  void (*dealloc)(void* set, const PolicyFunctions& policy, ctrl_t* ctrl,
-                  void* slot_array, size_t n);
+  // Deallocate the backing store from common.
+  void (*dealloc)(CommonFields& common, const PolicyFunctions& policy);
 };
 
 // ClearBackingArray clears the backing array, either modifying it in place,
@@ -1279,16 +1449,16 @@ void EraseMetaOnly(CommonFields& c, ctrl_t* it, size_t slot_size);
 // function body for raw_hash_set instantiations that have the
 // same slot alignment.
 template <size_t AlignOfSlot>
-ABSL_ATTRIBUTE_NOINLINE void DeallocateStandard(void*,
-                                                const PolicyFunctions& policy,
-                                                ctrl_t* ctrl, void* slot_array,
-                                                size_t n) {
+ABSL_ATTRIBUTE_NOINLINE void DeallocateStandard(CommonFields& common,
+                                                const PolicyFunctions& policy) {
   // Unpoison before returning the memory to the allocator.
-  SanitizerUnpoisonMemoryRegion(slot_array, policy.slot_size * n);
+  SanitizerUnpoisonMemoryRegion(common.slot_array(),
+                                policy.slot_size * common.capacity());
 
   std::allocator<char> alloc;
-  Deallocate<AlignOfSlot>(&alloc, ctrl,
-                          AllocSize(n, policy.slot_size, AlignOfSlot));
+  Deallocate<BackingArrayAlignment(AlignOfSlot)>(
+      &alloc, common.backing_array_start(),
+      common.alloc_size(policy.slot_size, AlignOfSlot));
 }
 
 // For trivially relocatable types we use memcpy directly. This allows us to
@@ -1419,22 +1589,19 @@ class raw_hash_set {
 
     // PRECONDITION: not an end() iterator.
     reference operator*() const {
-      ABSL_INTERNAL_ASSERT_IS_FULL(ctrl_, generation(), generation_ptr(),
-                                   "operator*()");
+      AssertIsFull(ctrl_, generation(), generation_ptr(), "operator*()");
       return PolicyTraits::element(slot_);
     }
 
     // PRECONDITION: not an end() iterator.
     pointer operator->() const {
-      ABSL_INTERNAL_ASSERT_IS_FULL(ctrl_, generation(), generation_ptr(),
-                                   "operator->");
+      AssertIsFull(ctrl_, generation(), generation_ptr(), "operator->");
       return &operator*();
     }
 
     // PRECONDITION: not an end() iterator.
     iterator& operator++() {
-      ABSL_INTERNAL_ASSERT_IS_FULL(ctrl_, generation(), generation_ptr(),
-                                   "operator++");
+      AssertIsFull(ctrl_, generation(), generation_ptr(), "operator++");
       ++ctrl_;
       ++slot_;
       skip_empty_or_deleted();
@@ -1448,9 +1615,10 @@ class raw_hash_set {
     }
 
     friend bool operator==(const iterator& a, const iterator& b) {
-      AssertSameContainer(a.ctrl_, b.ctrl_, a.slot_, b.slot_);
       AssertIsValidForComparison(a.ctrl_, a.generation(), a.generation_ptr());
       AssertIsValidForComparison(b.ctrl_, b.generation(), b.generation_ptr());
+      AssertSameContainer(a.ctrl_, b.ctrl_, a.slot_, b.slot_,
+                          a.generation_ptr(), b.generation_ptr());
       return a.ctrl_ == b.ctrl_;
     }
     friend bool operator!=(const iterator& a, const iterator& b) {
@@ -1469,7 +1637,7 @@ class raw_hash_set {
     }
     // For end() iterators.
     explicit iterator(const GenerationType* generation_ptr)
-        : HashSetIteratorGenerationInfo(generation_ptr) {}
+        : HashSetIteratorGenerationInfo(generation_ptr), ctrl_(nullptr) {}
 
     // Fixes up `ctrl_` to point to a full by advancing it and `slot_` until
     // they reach one.
@@ -1484,7 +1652,9 @@ class raw_hash_set {
       if (ABSL_PREDICT_FALSE(*ctrl_ == ctrl_t::kSentinel)) ctrl_ = nullptr;
     }
 
-    ctrl_t* ctrl_ = nullptr;
+    // We use EmptyGroup() for default-constructed iterators so that they can
+    // be distinguished from end iterators, which have nullptr ctrl_.
+    ctrl_t* ctrl_ = EmptyGroup();
     // To avoid uninitialized member warnings, put slot_ in an anonymous union.
     // The member is not initialized on singleton and end iterators.
     union {
@@ -1537,9 +1707,9 @@ class raw_hash_set {
   // Note: can't use `= default` due to non-default noexcept (causes
   // problems for some compilers). NOLINTNEXTLINE
   raw_hash_set() noexcept(
-      std::is_nothrow_default_constructible<hasher>::value&&
-          std::is_nothrow_default_constructible<key_equal>::value&&
-              std::is_nothrow_default_constructible<allocator_type>::value) {}
+      std::is_nothrow_default_constructible<hasher>::value &&
+      std::is_nothrow_default_constructible<key_equal>::value &&
+      std::is_nothrow_default_constructible<allocator_type>::value) {}
 
   ABSL_ATTRIBUTE_NOINLINE explicit raw_hash_set(
       size_t bucket_count, const hasher& hash = hasher(),
@@ -1547,7 +1717,7 @@ class raw_hash_set {
       const allocator_type& alloc = allocator_type())
       : settings_(CommonFields{}, hash, eq, alloc) {
     if (bucket_count) {
-      common().capacity_ = NormalizeCapacity(bucket_count);
+      common().set_capacity(NormalizeCapacity(bucket_count));
       initialize_slots();
     }
   }
@@ -1649,7 +1819,9 @@ class raw_hash_set {
 
   raw_hash_set(const raw_hash_set& that, const allocator_type& a)
       : raw_hash_set(0, that.hash_ref(), that.eq_ref(), a) {
-    reserve(that.size());
+    const size_t size = that.size();
+    if (size == 0) return;
+    reserve(size);
     // Because the table is guaranteed to be empty, we can do something faster
     // than a full `insert`.
     for (const auto& v : that) {
@@ -1660,14 +1832,14 @@ class raw_hash_set {
       common().maybe_increment_generation_on_insert();
       infoz().RecordInsert(hash, target.probe_length);
     }
-    common().size_ = that.size();
-    growth_left() -= that.size();
+    common().set_size(size);
+    set_growth_left(growth_left() - size);
   }
 
   ABSL_ATTRIBUTE_NOINLINE raw_hash_set(raw_hash_set&& that) noexcept(
-      std::is_nothrow_copy_constructible<hasher>::value&&
-          std::is_nothrow_copy_constructible<key_equal>::value&&
-              std::is_nothrow_copy_constructible<allocator_type>::value)
+      std::is_nothrow_copy_constructible<hasher>::value &&
+      std::is_nothrow_copy_constructible<key_equal>::value &&
+      std::is_nothrow_copy_constructible<allocator_type>::value)
       :  // Hash, equality and allocator are copied instead of moved because
          // `that` must be left valid. If Hash is std::function<Key>, moving it
          // would create a nullptr functor that cannot be called.
@@ -1696,9 +1868,9 @@ class raw_hash_set {
   }
 
   raw_hash_set& operator=(raw_hash_set&& that) noexcept(
-      absl::allocator_traits<allocator_type>::is_always_equal::value&&
-          std::is_nothrow_move_assignable<hasher>::value&&
-              std::is_nothrow_move_assignable<key_equal>::value) {
+      absl::allocator_traits<allocator_type>::is_always_equal::value &&
+      std::is_nothrow_move_assignable<hasher>::value &&
+      std::is_nothrow_move_assignable<key_equal>::value) {
     // TODO(sbenza): We should only use the operations from the noexcept clause
     // to make sure we actually adhere to that contract.
     // NOLINTNEXTLINE: not returning *this for performance.
@@ -1714,30 +1886,36 @@ class raw_hash_set {
 
     // Unpoison before returning the memory to the allocator.
     SanitizerUnpoisonMemoryRegion(slot_array(), sizeof(slot_type) * cap);
-    Deallocate<alignof(slot_type)>(
-        &alloc_ref(), control(),
+    Deallocate<BackingArrayAlignment(alignof(slot_type))>(
+        &alloc_ref(), common().backing_array_start(),
         AllocSize(cap, sizeof(slot_type), alignof(slot_type)));
 
     infoz().Unregister();
   }
 
-  iterator begin() {
+  iterator begin() ABSL_ATTRIBUTE_LIFETIME_BOUND {
     auto it = iterator_at(0);
     it.skip_empty_or_deleted();
     return it;
   }
-  iterator end() { return iterator(common().generation_ptr()); }
+  iterator end() ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return iterator(common().generation_ptr());
+  }
 
-  const_iterator begin() const {
+  const_iterator begin() const ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return const_cast<raw_hash_set*>(this)->begin();
   }
-  const_iterator end() const { return iterator(common().generation_ptr()); }
-  const_iterator cbegin() const { return begin(); }
-  const_iterator cend() const { return end(); }
+  const_iterator end() const ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return iterator(common().generation_ptr());
+  }
+  const_iterator cbegin() const ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return begin();
+  }
+  const_iterator cend() const ABSL_ATTRIBUTE_LIFETIME_BOUND { return end(); }
 
   bool empty() const { return !size(); }
-  size_t size() const { return common().size_; }
-  size_t capacity() const { return common().capacity_; }
+  size_t size() const { return common().size(); }
+  size_t capacity() const { return common().capacity(); }
   size_t max_size() const { return (std::numeric_limits<size_t>::max)(); }
 
   ABSL_ATTRIBUTE_REINITIALIZES void clear() {
@@ -1753,10 +1931,10 @@ class raw_hash_set {
       // Already guaranteed to be empty; so nothing to do.
     } else {
       destroy_slots();
-      ClearBackingArray(common(), GetPolicyFunctions(),
-                        /*reuse=*/cap < 128);
+      ClearBackingArray(common(), GetPolicyFunctions(), /*reuse=*/cap < 128);
     }
     common().set_reserved_growth(0);
+    common().set_reservation_size(0);
   }
 
   inline void destroy_slots() {
@@ -1780,7 +1958,7 @@ class raw_hash_set {
   template <class T, RequiresInsertable<T> = 0, class T2 = T,
             typename std::enable_if<IsDecomposable<T2>::value, int>::type = 0,
             T* = nullptr>
-  std::pair<iterator, bool> insert(T&& value) {
+  std::pair<iterator, bool> insert(T&& value) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return emplace(std::forward<T>(value));
   }
 
@@ -1795,13 +1973,11 @@ class raw_hash_set {
   //   const char* p = "hello";
   //   s.insert(p);
   //
-  // TODO(romanp): Once we stop supporting gcc 5.1 and below, replace
-  // RequiresInsertable<T> with RequiresInsertable<const T&>.
-  // We are hitting this bug: https://godbolt.org/g/1Vht4f.
   template <
-      class T, RequiresInsertable<T> = 0,
+      class T, RequiresInsertable<const T&> = 0,
       typename std::enable_if<IsDecomposable<const T&>::value, int>::type = 0>
-  std::pair<iterator, bool> insert(const T& value) {
+  std::pair<iterator, bool> insert(const T& value)
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return emplace(value);
   }
 
@@ -1810,7 +1986,8 @@ class raw_hash_set {
   //
   //   flat_hash_map<std::string, int> s;
   //   s.insert({"abc", 42});
-  std::pair<iterator, bool> insert(init_type&& value) {
+  std::pair<iterator, bool> insert(init_type&& value)
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return emplace(std::move(value));
   }
 
@@ -1819,21 +1996,20 @@ class raw_hash_set {
   template <class T, RequiresInsertable<T> = 0, class T2 = T,
             typename std::enable_if<IsDecomposable<T2>::value, int>::type = 0,
             T* = nullptr>
-  iterator insert(const_iterator, T&& value) {
+  iterator insert(const_iterator, T&& value) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return insert(std::forward<T>(value)).first;
   }
 
-  // TODO(romanp): Once we stop supporting gcc 5.1 and below, replace
-  // RequiresInsertable<T> with RequiresInsertable<const T&>.
-  // We are hitting this bug: https://godbolt.org/g/1Vht4f.
   template <
-      class T, RequiresInsertable<T> = 0,
+      class T, RequiresInsertable<const T&> = 0,
       typename std::enable_if<IsDecomposable<const T&>::value, int>::type = 0>
-  iterator insert(const_iterator, const T& value) {
+  iterator insert(const_iterator,
+                  const T& value) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return insert(value).first;
   }
 
-  iterator insert(const_iterator, init_type&& value) {
+  iterator insert(const_iterator,
+                  init_type&& value) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return insert(std::move(value)).first;
   }
 
@@ -1851,7 +2027,7 @@ class raw_hash_set {
     insert(ilist.begin(), ilist.end());
   }
 
-  insert_return_type insert(node_type&& node) {
+  insert_return_type insert(node_type&& node) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     if (!node) return {end(), false, node_type()};
     const auto& elem = PolicyTraits::element(CommonAccess::GetSlot(node));
     auto res = PolicyTraits::apply(
@@ -1865,7 +2041,8 @@ class raw_hash_set {
     }
   }
 
-  iterator insert(const_iterator, node_type&& node) {
+  iterator insert(const_iterator,
+                  node_type&& node) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     auto res = insert(std::move(node));
     node = std::move(res.node);
     return res.position;
@@ -1882,7 +2059,8 @@ class raw_hash_set {
   //   m.emplace("abc", "xyz");
   template <class... Args, typename std::enable_if<
                                IsDecomposable<Args...>::value, int>::type = 0>
-  std::pair<iterator, bool> emplace(Args&&... args) {
+  std::pair<iterator, bool> emplace(Args&&... args)
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return PolicyTraits::apply(EmplaceDecomposable{*this},
                                std::forward<Args>(args)...);
   }
@@ -1892,7 +2070,8 @@ class raw_hash_set {
   // destroys.
   template <class... Args, typename std::enable_if<
                                !IsDecomposable<Args...>::value, int>::type = 0>
-  std::pair<iterator, bool> emplace(Args&&... args) {
+  std::pair<iterator, bool> emplace(Args&&... args)
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
     alignas(slot_type) unsigned char raw[sizeof(slot_type)];
     slot_type* slot = reinterpret_cast<slot_type*>(&raw);
 
@@ -1902,14 +2081,16 @@ class raw_hash_set {
   }
 
   template <class... Args>
-  iterator emplace_hint(const_iterator, Args&&... args) {
+  iterator emplace_hint(const_iterator,
+                        Args&&... args) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return emplace(std::forward<Args>(args)...).first;
   }
 
   // Extension API: support for lazy emplace.
   //
   // Looks up key in the table. If found, returns the iterator to the element.
-  // Otherwise calls `f` with one argument of type `raw_hash_set::constructor`.
+  // Otherwise calls `f` with one argument of type `raw_hash_set::constructor`,
+  // and returns an iterator to the new element.
   //
   // `f` must abide by several restrictions:
   //  - it MUST call `raw_hash_set::constructor` with arguments as if a
@@ -1952,7 +2133,8 @@ class raw_hash_set {
   };
 
   template <class K = key_type, class F>
-  iterator lazy_emplace(const key_arg<K>& key, F&& f) {
+  iterator lazy_emplace(const key_arg<K>& key,
+                        F&& f) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     auto res = find_or_prepare_insert(key);
     if (res.second) {
       slot_type* slot = slot_array() + res.first;
@@ -1997,13 +2179,25 @@ class raw_hash_set {
   // This overload is necessary because otherwise erase<K>(const K&) would be
   // a better match if non-const iterator is passed as an argument.
   void erase(iterator it) {
-    ABSL_INTERNAL_ASSERT_IS_FULL(it.ctrl_, it.generation(), it.generation_ptr(),
-                                 "erase()");
+    AssertIsFull(it.ctrl_, it.generation(), it.generation_ptr(), "erase()");
     PolicyTraits::destroy(&alloc_ref(), it.slot_);
     erase_meta_only(it);
   }
 
-  iterator erase(const_iterator first, const_iterator last) {
+  iterator erase(const_iterator first,
+                 const_iterator last) ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    // We check for empty first because ClearBackingArray requires that
+    // capacity() > 0 as a precondition.
+    if (empty()) return end();
+    if (first == begin() && last == end()) {
+      // TODO(ezb): we access control bytes in destroy_slots so it could make
+      // sense to combine destroy_slots and ClearBackingArray to avoid cache
+      // misses when the table is large. Note that we also do this in clear().
+      destroy_slots();
+      ClearBackingArray(common(), GetPolicyFunctions(), /*reuse=*/true);
+      common().set_reserved_growth(common().reservation_size());
+      return end();
+    }
     while (first != last) {
       erase(first++);
     }
@@ -2032,9 +2226,8 @@ class raw_hash_set {
   }
 
   node_type extract(const_iterator position) {
-    ABSL_INTERNAL_ASSERT_IS_FULL(position.inner_.ctrl_,
-                                 position.inner_.generation(),
-                                 position.inner_.generation_ptr(), "extract()");
+    AssertIsFull(position.inner_.ctrl_, position.inner_.generation(),
+                 position.inner_.generation_ptr(), "extract()");
     auto node =
         CommonAccess::Transfer<node_type>(alloc_ref(), position.inner_.slot_);
     erase_meta_only(position);
@@ -2064,8 +2257,7 @@ class raw_hash_set {
   void rehash(size_t n) {
     if (n == 0 && capacity() == 0) return;
     if (n == 0 && size() == 0) {
-      ClearBackingArray(common(), GetPolicyFunctions(),
-                        /*reuse=*/false);
+      ClearBackingArray(common(), GetPolicyFunctions(), /*reuse=*/false);
       return;
     }
 
@@ -2092,6 +2284,7 @@ class raw_hash_set {
       infoz().RecordReservation(n);
     }
     common().reset_reserved_growth(n);
+    common().set_reservation_size(n);
   }
 
   // Extension API: support for heterogeneous keys.
@@ -2117,12 +2310,12 @@ class raw_hash_set {
   void prefetch(const key_arg<K>& key) const {
     (void)key;
     // Avoid probing if we won't be able to prefetch the addresses received.
-#ifdef ABSL_INTERNAL_HAVE_PREFETCH
+#ifdef ABSL_HAVE_PREFETCH
     prefetch_heap_block();
     auto seq = probe(common(), hash_ref()(key));
-    base_internal::PrefetchT0(control() + seq.offset());
-    base_internal::PrefetchT0(slot_array() + seq.offset());
-#endif  // ABSL_INTERNAL_HAVE_PREFETCH
+    PrefetchToLocalCache(control() + seq.offset());
+    PrefetchToLocalCache(slot_array() + seq.offset());
+#endif  // ABSL_HAVE_PREFETCH
   }
 
   // The API of find() has two extensions.
@@ -2133,7 +2326,8 @@ class raw_hash_set {
   // 2. The type of the key argument doesn't have to be key_type. This is so
   // called heterogeneous key support.
   template <class K = key_type>
-  iterator find(const key_arg<K>& key, size_t hash) {
+  iterator find(const key_arg<K>& key,
+                size_t hash) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     auto seq = probe(common(), hash);
     slot_type* slot_ptr = slot_array();
     const ctrl_t* ctrl = control();
@@ -2151,17 +2345,19 @@ class raw_hash_set {
     }
   }
   template <class K = key_type>
-  iterator find(const key_arg<K>& key) {
+  iterator find(const key_arg<K>& key) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     prefetch_heap_block();
     return find(key, hash_ref()(key));
   }
 
   template <class K = key_type>
-  const_iterator find(const key_arg<K>& key, size_t hash) const {
+  const_iterator find(const key_arg<K>& key,
+                      size_t hash) const ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return const_cast<raw_hash_set*>(this)->find(key, hash);
   }
   template <class K = key_type>
-  const_iterator find(const key_arg<K>& key) const {
+  const_iterator find(const key_arg<K>& key) const
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
     prefetch_heap_block();
     return find(key, hash_ref()(key));
   }
@@ -2172,14 +2368,15 @@ class raw_hash_set {
   }
 
   template <class K = key_type>
-  std::pair<iterator, iterator> equal_range(const key_arg<K>& key) {
+  std::pair<iterator, iterator> equal_range(const key_arg<K>& key)
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
     auto it = find(key);
     if (it != end()) return {it, std::next(it)};
     return {it, it};
   }
   template <class K = key_type>
   std::pair<const_iterator, const_iterator> equal_range(
-      const key_arg<K>& key) const {
+      const key_arg<K>& key) const ABSL_ATTRIBUTE_LIFETIME_BOUND {
     auto it = find(key);
     if (it != end()) return {it, std::next(it)};
     return {it, it};
@@ -2313,8 +2510,8 @@ class raw_hash_set {
     assert(IsValidCapacity(new_capacity));
     auto* old_ctrl = control();
     auto* old_slots = slot_array();
-    const size_t old_capacity = common().capacity_;
-    common().capacity_ = new_capacity;
+    const size_t old_capacity = common().capacity();
+    common().set_capacity(new_capacity);
     initialize_slots();
 
     auto* new_slots = slot_array();
@@ -2333,8 +2530,8 @@ class raw_hash_set {
     if (old_capacity) {
       SanitizerUnpoisonMemoryRegion(old_slots,
                                     sizeof(slot_type) * old_capacity);
-      Deallocate<alignof(slot_type)>(
-          &alloc_ref(), old_ctrl,
+      Deallocate<BackingArrayAlignment(alignof(slot_type))>(
+          &alloc_ref(), old_ctrl - ControlOffset(),
           AllocSize(old_capacity, sizeof(slot_type), alignof(slot_type)));
     }
     infoz().RecordRehash(total_probe_length);
@@ -2357,8 +2554,8 @@ class raw_hash_set {
   void rehash_and_grow_if_necessary() {
     const size_t cap = capacity();
     if (cap > Group::kWidth &&
-        // Do these calcuations in 64-bit to avoid overflow.
-        size() * uint64_t{32} <= cap* uint64_t{25}) {
+        // Do these calculations in 64-bit to avoid overflow.
+        size() * uint64_t{32} <= cap * uint64_t{25}) {
       // Squash DELETED without growing if there is enough capacity.
       //
       // Rehash in place if the current size is <= 25/32 of capacity.
@@ -2481,8 +2678,8 @@ class raw_hash_set {
       rehash_and_grow_if_necessary();
       target = find_first_non_full(common(), hash);
     }
-    ++common().size_;
-    growth_left() -= IsEmpty(control()[target.offset]);
+    common().set_size(common().size() + 1);
+    set_growth_left(growth_left() - IsEmpty(control()[target.offset]));
     SetCtrl(common(), target.offset, H2(hash), sizeof(slot_type));
     common().maybe_increment_generation_on_insert();
     infoz().RecordInsert(hash, target.probe_length);
@@ -2507,10 +2704,10 @@ class raw_hash_set {
            "constructed value does not match the lookup key");
   }
 
-  iterator iterator_at(size_t i) {
+  iterator iterator_at(size_t i) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return {control() + i, slot_array() + i, common().generation_ptr()};
   }
-  const_iterator iterator_at(size_t i) const {
+  const_iterator iterator_at(size_t i) const ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return {control() + i, slot_array() + i, common().generation_ptr()};
   }
 
@@ -2527,19 +2724,24 @@ class raw_hash_set {
   // side-effect.
   //
   // See `CapacityToGrowth()`.
-  size_t& growth_left() { return common().growth_left(); }
-
-  // Prefetch the heap-allocated memory region to resolve potential TLB misses.
-  // This is intended to overlap with execution of calculating the hash for a
-  // key.
-  void prefetch_heap_block() const { base_internal::PrefetchT2(control()); }
+  size_t growth_left() const { return common().growth_left(); }
+  void set_growth_left(size_t gl) { return common().set_growth_left(gl); }
+
+  // Prefetch the heap-allocated memory region to resolve potential TLB and
+  // cache misses. This is intended to overlap with execution of calculating the
+  // hash for a key.
+  void prefetch_heap_block() const {
+#if ABSL_HAVE_BUILTIN(__builtin_prefetch) || defined(__GNUC__)
+    __builtin_prefetch(control(), 0, 1);
+#endif
+  }
 
   CommonFields& common() { return settings_.template get<0>(); }
   const CommonFields& common() const { return settings_.template get<0>(); }
 
-  ctrl_t* control() const { return common().control_; }
+  ctrl_t* control() const { return common().control(); }
   slot_type* slot_array() const {
-    return static_cast<slot_type*>(common().slots_);
+    return static_cast<slot_type*>(common().slot_array());
   }
   HashtablezInfoHandle& infoz() { return common().infoz(); }
 
@@ -2565,16 +2767,16 @@ class raw_hash_set {
                            static_cast<slot_type*>(src));
   }
   // Note: dealloc_fn will only be used if we have a non-standard allocator.
-  static void dealloc_fn(void* set, const PolicyFunctions&, ctrl_t* ctrl,
-                         void* slot_mem, size_t n) {
-    auto* h = static_cast<raw_hash_set*>(set);
+  static void dealloc_fn(CommonFields& common, const PolicyFunctions&) {
+    auto* set = reinterpret_cast<raw_hash_set*>(&common);
 
     // Unpoison before returning the memory to the allocator.
-    SanitizerUnpoisonMemoryRegion(slot_mem, sizeof(slot_type) * n);
+    SanitizerUnpoisonMemoryRegion(common.slot_array(),
+                                  sizeof(slot_type) * common.capacity());
 
-    Deallocate<alignof(slot_type)>(
-        &h->alloc_ref(), ctrl,
-        AllocSize(n, sizeof(slot_type), alignof(slot_type)));
+    Deallocate<BackingArrayAlignment(alignof(slot_type))>(
+        &set->alloc_ref(), common.backing_array_start(),
+        common.alloc_size(sizeof(slot_type), alignof(slot_type)));
   }
 
   static const PolicyFunctions& GetPolicyFunctions() {
@@ -2680,6 +2882,5 @@ ABSL_NAMESPACE_END
 }  // namespace absl
 
 #undef ABSL_SWISSTABLE_ENABLE_GENERATIONS
-#undef ABSL_INTERNAL_ASSERT_IS_FULL
 
 #endif  // ABSL_CONTAINER_INTERNAL_RAW_HASH_SET_H_
diff --git a/absl/container/internal/raw_hash_set_benchmark.cc b/absl/container/internal/raw_hash_set_benchmark.cc
index f77f2a7b..a3647890 100644
--- a/absl/container/internal/raw_hash_set_benchmark.cc
+++ b/absl/container/internal/raw_hash_set_benchmark.cc
@@ -142,7 +142,7 @@ struct string_generator {
   template <class RNG>
   std::string operator()(RNG& rng) const {
     std::string res;
-    res.resize(12);
+    res.resize(size);
     std::uniform_int_distribution<uint32_t> printable_ascii(0x20, 0x7E);
     std::generate(res.begin(), res.end(), [&] { return printable_ascii(rng); });
     return res;
diff --git a/absl/container/internal/raw_hash_set_test.cc b/absl/container/internal/raw_hash_set_test.cc
index 3d3b089c..242a97cb 100644
--- a/absl/container/internal/raw_hash_set_test.cc
+++ b/absl/container/internal/raw_hash_set_test.cc
@@ -17,6 +17,7 @@
 #include <algorithm>
 #include <atomic>
 #include <cmath>
+#include <cstddef>
 #include <cstdint>
 #include <deque>
 #include <functional>
@@ -40,8 +41,7 @@
 #include "absl/base/attributes.h"
 #include "absl/base/config.h"
 #include "absl/base/internal/cycleclock.h"
-#include "absl/base/internal/prefetch.h"
-#include "absl/base/internal/raw_logging.h"
+#include "absl/base/prefetch.h"
 #include "absl/container/flat_hash_map.h"
 #include "absl/container/flat_hash_set.h"
 #include "absl/container/internal/container_memory.h"
@@ -60,6 +60,10 @@ struct RawHashSetTestOnlyAccess {
   static auto GetSlots(const C& c) -> decltype(c.slot_array()) {
     return c.slot_array();
   }
+  template <typename C>
+  static size_t CountTombstones(const C& c) {
+    return c.common().TombstonesCount();
+  }
 };
 
 namespace {
@@ -437,6 +441,63 @@ struct CustomAllocIntTable
   using Base::Base;
 };
 
+// Tries to allocate memory at the minimum alignment even when the default
+// allocator uses a higher alignment.
+template <typename T>
+struct MinimumAlignmentAlloc : std::allocator<T> {
+  MinimumAlignmentAlloc() = default;
+
+  template <typename U>
+  explicit MinimumAlignmentAlloc(const MinimumAlignmentAlloc<U>& /*other*/) {}
+
+  template <class U>
+  struct rebind {
+    using other = MinimumAlignmentAlloc<U>;
+  };
+
+  T* allocate(size_t n) {
+    T* ptr = std::allocator<T>::allocate(n + 1);
+    char* cptr = reinterpret_cast<char*>(ptr);
+    cptr += alignof(T);
+    return reinterpret_cast<T*>(cptr);
+  }
+
+  void deallocate(T* ptr, size_t n) {
+    char* cptr = reinterpret_cast<char*>(ptr);
+    cptr -= alignof(T);
+    std::allocator<T>::deallocate(reinterpret_cast<T*>(cptr), n + 1);
+  }
+};
+
+struct MinimumAlignmentUint8Table
+    : raw_hash_set<Uint8Policy, container_internal::hash_default_hash<uint8_t>,
+                   std::equal_to<uint8_t>, MinimumAlignmentAlloc<uint8_t>> {
+  using Base = typename MinimumAlignmentUint8Table::raw_hash_set;
+  using Base::Base;
+};
+
+// Allows for freezing the allocator to expect no further allocations.
+template <typename T>
+struct FreezableAlloc : std::allocator<T> {
+  explicit FreezableAlloc(bool* f) : frozen(f) {}
+
+  template <typename U>
+  explicit FreezableAlloc(const FreezableAlloc<U>& other)
+      : frozen(other.frozen) {}
+
+  template <class U>
+  struct rebind {
+    using other = FreezableAlloc<U>;
+  };
+
+  T* allocate(size_t n) {
+    EXPECT_FALSE(*frozen);
+    return std::allocator<T>::allocate(n);
+  }
+
+  bool* frozen;
+};
+
 struct BadFastHash {
   template <class T>
   size_t operator()(const T&) const {
@@ -444,6 +505,13 @@ struct BadFastHash {
   }
 };
 
+struct BadHashFreezableIntTable
+    : raw_hash_set<IntPolicy, BadFastHash, std::equal_to<int64_t>,
+                   FreezableAlloc<int64_t>> {
+  using Base = typename BadHashFreezableIntTable::raw_hash_set;
+  using Base::Base;
+};
+
 struct BadTable : raw_hash_set<IntPolicy, BadFastHash, std::equal_to<int>,
                                std::allocator<int>> {
   using Base = typename BadTable::raw_hash_set;
@@ -461,14 +529,12 @@ TEST(Table, EmptyFunctorOptimization) {
     void* slots;
     size_t size;
     size_t capacity;
-    size_t growth_left;
   };
   struct MockTableInfozDisabled {
     void* ctrl;
     void* slots;
     size_t size;
     size_t capacity;
-    size_t growth_left;
   };
   struct StatelessHash {
     size_t operator()(absl::string_view) const { return 0; }
@@ -479,6 +545,7 @@ TEST(Table, EmptyFunctorOptimization) {
 
   struct GenerationData {
     size_t reserved_growth;
+    size_t reservation_size;
     GenerationType* generation;
   };
 
@@ -865,6 +932,10 @@ void TestDecompose(bool construct_three) {
 }
 
 TEST(Table, Decompose) {
+  if (SwisstableGenerationsEnabled()) {
+    GTEST_SKIP() << "Generations being enabled causes extra rehashes.";
+  }
+
   TestDecompose<DecomposeHash, DecomposeEq>(false);
 
   struct TransparentHashIntOverload {
@@ -903,6 +974,10 @@ struct Modulo1000HashTable
 
 // Test that rehash with no resize happen in case of many deleted slots.
 TEST(Table, RehashWithNoResize) {
+  if (SwisstableGenerationsEnabled()) {
+    GTEST_SKIP() << "Generations being enabled causes extra rehashes.";
+  }
+
   Modulo1000HashTable t;
   // Adding the same length (and the same hash) strings
   // to have at least kMinFullGroups groups
@@ -996,6 +1071,10 @@ TEST(Table, EnsureNonQuadraticAsInRust) {
 }
 
 TEST(Table, ClearBug) {
+  if (SwisstableGenerationsEnabled()) {
+    GTEST_SKIP() << "Generations being enabled causes extra rehashes.";
+  }
+
   IntTable t;
   constexpr size_t capacity = container_internal::Group::kWidth - 1;
   constexpr size_t max_size = capacity / 2 + 1;
@@ -1048,6 +1127,14 @@ TEST(Table, EraseMaintainsValidIterator) {
   EXPECT_EQ(num_erase_calls, kNumElements);
 }
 
+TEST(Table, EraseBeginEnd) {
+  IntTable t;
+  for (int i = 0; i < 10; ++i) t.insert(i);
+  EXPECT_EQ(t.size(), 10);
+  t.erase(t.begin(), t.end());
+  EXPECT_EQ(t.size(), 0);
+}
+
 // Collect N bad keys by following algorithm:
 // 1. Create an empty table and reserve it to 2 * N.
 // 2. Insert N random elements.
@@ -1268,7 +1355,7 @@ ExpectedStats XorSeedExpectedStats() {
                 {{0.95, 0}, {0.99, 1}, {0.999, 4}, {0.9999, 10}}};
       }
   }
-  ABSL_RAW_LOG(FATAL, "%s", "Unknown Group width");
+  LOG(FATAL) << "Unknown Group width";
   return {};
 }
 
@@ -1364,7 +1451,7 @@ ExpectedStats LinearTransformExpectedStats() {
                 {{0.95, 0}, {0.99, 1}, {0.999, 6}, {0.9999, 10}}};
       }
   }
-  ABSL_RAW_LOG(FATAL, "%s", "Unknown Group width");
+  LOG(FATAL) << "Unknown Group width";
   return {};
 }
 
@@ -2044,30 +2131,43 @@ bool IsAssertEnabled() {
 }
 
 TEST(TableDeathTest, InvalidIteratorAsserts) {
-  if (!IsAssertEnabled()) GTEST_SKIP() << "Assertions not enabled.";
+  if (!IsAssertEnabled() && !SwisstableGenerationsEnabled())
+    GTEST_SKIP() << "Assertions not enabled.";
 
   IntTable t;
   // Extra simple "regexp" as regexp support is highly varied across platforms.
-  EXPECT_DEATH_IF_SUPPORTED(
-      t.erase(t.end()),
-      "erase.* called on invalid iterator. The iterator might be an "
-      "end.*iterator or may have been default constructed.");
+  EXPECT_DEATH_IF_SUPPORTED(t.erase(t.end()),
+                            "erase.* called on end.. iterator.");
   typename IntTable::iterator iter;
   EXPECT_DEATH_IF_SUPPORTED(
-      ++iter,
-      "operator.* called on invalid iterator. The iterator might be an "
-      "end.*iterator or may have been default constructed.");
+      ++iter, "operator.* called on default-constructed iterator.");
   t.insert(0);
   iter = t.begin();
   t.erase(iter);
-  EXPECT_DEATH_IF_SUPPORTED(
-      ++iter,
-      "operator.* called on invalid iterator. The element might have been "
-      "erased or .*the table might have rehashed.");
+  const char* const kErasedDeathMessage =
+      SwisstableGenerationsEnabled()
+          ? "operator.* called on invalid iterator.*was likely erased"
+          : "operator.* called on invalid iterator.*might have been "
+            "erased.*config=asan";
+  EXPECT_DEATH_IF_SUPPORTED(++iter, kErasedDeathMessage);
 }
 
+// Invalid iterator use can trigger heap-use-after-free in asan,
+// use-of-uninitialized-value in msan, or invalidated iterator assertions.
+constexpr const char* kInvalidIteratorDeathMessage =
+    "heap-use-after-free|use-of-uninitialized-value|invalidated "
+    "iterator|Invalid iterator|invalid iterator";
+
+// MSVC doesn't support | in regex.
+#if defined(_MSC_VER)
+constexpr bool kMsvc = true;
+#else
+constexpr bool kMsvc = false;
+#endif
+
 TEST(TableDeathTest, IteratorInvalidAssertsEqualityOperator) {
-  if (!IsAssertEnabled()) GTEST_SKIP() << "Assertions not enabled.";
+  if (!IsAssertEnabled() && !SwisstableGenerationsEnabled())
+    GTEST_SKIP() << "Assertions not enabled.";
 
   IntTable t;
   t.insert(1);
@@ -2080,8 +2180,9 @@ TEST(TableDeathTest, IteratorInvalidAssertsEqualityOperator) {
   t.erase(iter1);
   // Extra simple "regexp" as regexp support is highly varied across platforms.
   const char* const kErasedDeathMessage =
-      "Invalid iterator comparison. The element might have .*been erased or "
-      "the table might have rehashed.";
+      SwisstableGenerationsEnabled()
+          ? "Invalid iterator comparison.*was likely erased"
+          : "Invalid iterator comparison.*might have been erased.*config=asan";
   EXPECT_DEATH_IF_SUPPORTED(void(iter1 == iter2), kErasedDeathMessage);
   EXPECT_DEATH_IF_SUPPORTED(void(iter2 != iter1), kErasedDeathMessage);
   t.erase(iter2);
@@ -2093,15 +2194,25 @@ TEST(TableDeathTest, IteratorInvalidAssertsEqualityOperator) {
   iter1 = t1.begin();
   iter2 = t2.begin();
   const char* const kContainerDiffDeathMessage =
-      "Invalid iterator comparison. The iterators may be from different "
-      ".*containers or the container might have rehashed.";
+      SwisstableGenerationsEnabled()
+          ? "Invalid iterator comparison.*iterators from different hashtables"
+          : "Invalid iterator comparison.*may be from different "
+            ".*containers.*config=asan";
   EXPECT_DEATH_IF_SUPPORTED(void(iter1 == iter2), kContainerDiffDeathMessage);
   EXPECT_DEATH_IF_SUPPORTED(void(iter2 == iter1), kContainerDiffDeathMessage);
 
   for (int i = 0; i < 10; ++i) t1.insert(i);
   // There should have been a rehash in t1.
-  EXPECT_DEATH_IF_SUPPORTED(void(iter1 == t1.begin()),
-                            kContainerDiffDeathMessage);
+  if (kMsvc) return;  // MSVC doesn't support | in regex.
+
+  // NOTE(b/293887834): After rehashing, iterators will contain pointers to
+  // freed memory, which may be detected by ThreadSanitizer.
+  const char* const kRehashedDeathMessage =
+      SwisstableGenerationsEnabled()
+          ? kInvalidIteratorDeathMessage
+          : "Invalid iterator comparison.*might have rehashed.*config=asan"
+            "|ThreadSanitizer: heap-use-after-free";
+  EXPECT_DEATH_IF_SUPPORTED(void(iter1 == t1.begin()), kRehashedDeathMessage);
 }
 
 #if defined(ABSL_INTERNAL_HASHTABLEZ_SAMPLE)
@@ -2216,11 +2327,17 @@ TEST(Sanitizer, PoisoningOnErase) {
 }
 #endif  // ABSL_HAVE_ADDRESS_SANITIZER
 
-TEST(Table, AlignOne) {
+template <typename T>
+class AlignOneTest : public ::testing::Test {};
+using AlignOneTestTypes =
+    ::testing::Types<Uint8Table, MinimumAlignmentUint8Table>;
+TYPED_TEST_SUITE(AlignOneTest, AlignOneTestTypes);
+
+TYPED_TEST(AlignOneTest, AlignOne) {
   // We previously had a bug in which we were copying a control byte over the
   // first slot when alignof(value_type) is 1. We test repeated
   // insertions/erases and verify that the behavior is correct.
-  Uint8Table t;
+  TypeParam t;
   std::unordered_set<uint8_t> verifier;  // NOLINT
 
   // Do repeated insertions/erases from the table.
@@ -2246,21 +2363,9 @@ TEST(Table, AlignOne) {
   }
 }
 
-// Invalid iterator use can trigger heap-use-after-free in asan,
-// use-of-uninitialized-value in msan, or invalidated iterator assertions.
-constexpr const char* kInvalidIteratorDeathMessage =
-    "heap-use-after-free|use-of-uninitialized-value|invalidated "
-    "iterator|Invalid iterator";
-
-#if defined(__clang__) && defined(_MSC_VER)
-constexpr bool kLexan = true;
-#else
-constexpr bool kLexan = false;
-#endif
-
 TEST(Iterator, InvalidUseCrashesWithSanitizers) {
   if (!SwisstableGenerationsEnabled()) GTEST_SKIP() << "Generations disabled.";
-  if (kLexan) GTEST_SKIP() << "Lexan doesn't support | in regexp.";
+  if (kMsvc) GTEST_SKIP() << "MSVC doesn't support | in regexp.";
 
   IntTable t;
   // Start with 1 element so that `it` is never an end iterator.
@@ -2276,7 +2381,7 @@ TEST(Iterator, InvalidUseCrashesWithSanitizers) {
 
 TEST(Iterator, InvalidUseWithReserveCrashesWithSanitizers) {
   if (!SwisstableGenerationsEnabled()) GTEST_SKIP() << "Generations disabled.";
-  if (kLexan) GTEST_SKIP() << "Lexan doesn't support | in regexp.";
+  if (kMsvc) GTEST_SKIP() << "MSVC doesn't support | in regexp.";
 
   IntTable t;
   t.reserve(10);
@@ -2289,6 +2394,7 @@ TEST(Iterator, InvalidUseWithReserveCrashesWithSanitizers) {
   }
   // ptr will become invalidated on rehash.
   const int64_t* ptr = &*it;
+  (void)ptr;
 
   // erase decreases size but does not decrease reserved growth so the next
   // insertion still invalidates iterators.
@@ -2299,8 +2405,9 @@ TEST(Iterator, InvalidUseWithReserveCrashesWithSanitizers) {
   EXPECT_DEATH_IF_SUPPORTED(*it, kInvalidIteratorDeathMessage);
   EXPECT_DEATH_IF_SUPPORTED(void(it == t.begin()),
                             kInvalidIteratorDeathMessage);
-  EXPECT_DEATH_IF_SUPPORTED(std::cout << *ptr,
-                            "heap-use-after-free|use-of-uninitialized-value");
+#ifdef ABSL_HAVE_ADDRESS_SANITIZER
+  EXPECT_DEATH_IF_SUPPORTED(std::cout << *ptr, "heap-use-after-free");
+#endif
 }
 
 TEST(Table, ReservedGrowthUpdatesWhenTableDoesntGrow) {
@@ -2318,6 +2425,91 @@ TEST(Table, ReservedGrowthUpdatesWhenTableDoesntGrow) {
   EXPECT_EQ(*it, 0);
 }
 
+TEST(Table, EraseBeginEndResetsReservedGrowth) {
+  bool frozen = false;
+  BadHashFreezableIntTable t{FreezableAlloc<int64_t>(&frozen)};
+  t.reserve(100);
+  const size_t cap = t.capacity();
+  frozen = true;  // no further allocs allowed
+
+  for (int i = 0; i < 10; ++i) {
+    // Create a long run (hash function returns constant).
+    for (int j = 0; j < 100; ++j) t.insert(j);
+    // Erase elements from the middle of the long run, which creates tombstones.
+    for (int j = 30; j < 60; ++j) t.erase(j);
+    EXPECT_EQ(t.size(), 70);
+    EXPECT_EQ(t.capacity(), cap);
+    ASSERT_EQ(RawHashSetTestOnlyAccess::CountTombstones(t), 30);
+
+    t.erase(t.begin(), t.end());
+
+    EXPECT_EQ(t.size(), 0);
+    EXPECT_EQ(t.capacity(), cap);
+    ASSERT_EQ(RawHashSetTestOnlyAccess::CountTombstones(t), 0);
+  }
+}
+
+TEST(Table, GenerationInfoResetsOnClear) {
+  if (!SwisstableGenerationsEnabled()) GTEST_SKIP() << "Generations disabled.";
+  if (kMsvc) GTEST_SKIP() << "MSVC doesn't support | in regexp.";
+
+  IntTable t;
+  for (int i = 0; i < 1000; ++i) t.insert(i);
+  t.reserve(t.size() + 100);
+
+  t.clear();
+
+  t.insert(0);
+  auto it = t.begin();
+  t.insert(1);
+  EXPECT_DEATH_IF_SUPPORTED(*it, kInvalidIteratorDeathMessage);
+}
+
+TEST(Table, InvalidReferenceUseCrashesWithSanitizers) {
+  if (!SwisstableGenerationsEnabled()) GTEST_SKIP() << "Generations disabled.";
+#ifdef ABSL_HAVE_MEMORY_SANITIZER
+  GTEST_SKIP() << "MSan fails to detect some of these rehashes.";
+#endif
+
+  IntTable t;
+  t.insert(0);
+  // Rehashing is guaranteed on every insertion while capacity is less than
+  // RehashProbabilityConstant().
+  int64_t i = 0;
+  while (t.capacity() <= RehashProbabilityConstant()) {
+    // ptr will become invalidated on rehash.
+    const int64_t* ptr = &*t.begin();
+    t.insert(++i);
+    EXPECT_DEATH_IF_SUPPORTED(std::cout << *ptr, "heap-use-after-free") << i;
+  }
+}
+
+TEST(Iterator, InvalidComparisonDifferentTables) {
+  if (!SwisstableGenerationsEnabled()) GTEST_SKIP() << "Generations disabled.";
+
+  IntTable t1, t2;
+  IntTable::iterator default_constructed_iter;
+  // We randomly use one of N empty generations for generations from empty
+  // hashtables. In general, we won't always detect when iterators from
+  // different empty hashtables are compared, but in this test case, we
+  // should deterministically detect the error due to our randomness yielding
+  // consecutive random generations.
+  EXPECT_DEATH_IF_SUPPORTED(void(t1.end() == t2.end()),
+                            "Invalid iterator comparison.*empty hashtables");
+  EXPECT_DEATH_IF_SUPPORTED(void(t1.end() == default_constructed_iter),
+                            "Invalid iterator comparison.*default-constructed");
+  t1.insert(0);
+  EXPECT_DEATH_IF_SUPPORTED(void(t1.begin() == t2.end()),
+                            "Invalid iterator comparison.*empty hashtable");
+  EXPECT_DEATH_IF_SUPPORTED(void(t1.begin() == default_constructed_iter),
+                            "Invalid iterator comparison.*default-constructed");
+  t2.insert(0);
+  EXPECT_DEATH_IF_SUPPORTED(void(t1.begin() == t2.end()),
+                            "Invalid iterator comparison.*end.. iterator");
+  EXPECT_DEATH_IF_SUPPORTED(void(t1.begin() == t2.begin()),
+                            "Invalid iterator comparison.*non-end");
+}
+
 }  // namespace
 }  // namespace container_internal
 ABSL_NAMESPACE_END
diff --git a/absl/container/node_hash_map.h b/absl/container/node_hash_map.h
index 6868e63a..a396de2e 100644
--- a/absl/container/node_hash_map.h
+++ b/absl/container/node_hash_map.h
@@ -226,7 +226,11 @@ class node_hash_map
   // iterator erase(const_iterator first, const_iterator last):
   //
   //   Erases the elements in the open interval [`first`, `last`), returning an
-  //   iterator pointing to `last`.
+  //   iterator pointing to `last`. The special case of calling
+  //   `erase(begin(), end())` resets the reserved growth such that if
+  //   `reserve(N)` has previously been called and there has been no intervening
+  //   call to `clear()`, then after calling `erase(begin(), end())`, it is safe
+  //   to assume that inserting N elements will not cause a rehash.
   //
   // size_type erase(const key_type& key):
   //
@@ -404,7 +408,7 @@ class node_hash_map
   // for the past-the-end iterator, which is invalidated.
   //
   // `swap()` requires that the node hash map's hashing and key equivalence
-  // functions be Swappable, and are exchaged using unqualified calls to
+  // functions be Swappable, and are exchanged using unqualified calls to
   // non-member `swap()`. If the map's allocator has
   // `std::allocator_traits<allocator_type>::propagate_on_container_swap::value`
   // set to `true`, the allocators are also exchanged using an unqualified call
diff --git a/absl/container/node_hash_set.h b/absl/container/node_hash_set.h
index f2cc70c3..421ff460 100644
--- a/absl/container/node_hash_set.h
+++ b/absl/container/node_hash_set.h
@@ -218,7 +218,11 @@ class node_hash_set
   // iterator erase(const_iterator first, const_iterator last):
   //
   //   Erases the elements in the open interval [`first`, `last`), returning an
-  //   iterator pointing to `last`.
+  //   iterator pointing to `last`. The special case of calling
+  //   `erase(begin(), end())` resets the reserved growth such that if
+  //   `reserve(N)` has previously been called and there has been no intervening
+  //   call to `clear()`, then after calling `erase(begin(), end())`, it is safe
+  //   to assume that inserting N elements will not cause a rehash.
   //
   // size_type erase(const key_type& key):
   //
@@ -334,7 +338,7 @@ class node_hash_set
   // for the past-the-end iterator, which is invalidated.
   //
   // `swap()` requires that the node hash set's hashing and key equivalence
-  // functions be Swappable, and are exchaged using unqualified calls to
+  // functions be Swappable, and are exchanged using unqualified calls to
   // non-member `swap()`. If the set's allocator has
   // `std::allocator_traits<allocator_type>::propagate_on_container_swap::value`
   // set to `true`, the allocators are also exchanged using an unqualified call
diff --git a/absl/copts/AbseilConfigureCopts.cmake b/absl/copts/AbseilConfigureCopts.cmake
index 8209b262..3f737c81 100644
--- a/absl/copts/AbseilConfigureCopts.cmake
+++ b/absl/copts/AbseilConfigureCopts.cmake
@@ -83,6 +83,16 @@ elseif(CMAKE_CXX_COMPILER_ID MATCHES "Clang")  # MATCHES so we get both Clang an
     set(ABSL_DEFAULT_COPTS "${ABSL_LLVM_FLAGS}")
     set(ABSL_TEST_COPTS "${ABSL_LLVM_TEST_FLAGS}")
   endif()
+elseif(CMAKE_CXX_COMPILER_ID STREQUAL "IntelLLVM")
+  # IntelLLVM is similar to Clang, with some additional flags.
+  if(MSVC)
+    # clang-cl is half MSVC, half LLVM
+    set(ABSL_DEFAULT_COPTS "${ABSL_CLANG_CL_FLAGS}")
+    set(ABSL_TEST_COPTS "${ABSL_CLANG_CL_TEST_FLAGS}")
+  else()
+    set(ABSL_DEFAULT_COPTS "${ABSL_LLVM_FLAGS}")
+    set(ABSL_TEST_COPTS "${ABSL_LLVM_TEST_FLAGS}")
+  endif()
 elseif(CMAKE_CXX_COMPILER_ID STREQUAL "MSVC")
   set(ABSL_DEFAULT_COPTS "${ABSL_MSVC_FLAGS}")
   set(ABSL_TEST_COPTS "${ABSL_MSVC_TEST_FLAGS}")
diff --git a/absl/crc/BUILD.bazel b/absl/crc/BUILD.bazel
index 1c58f46c..cdbaa9b2 100644
--- a/absl/crc/BUILD.bazel
+++ b/absl/crc/BUILD.bazel
@@ -93,6 +93,7 @@ cc_library(
         "//absl/base:endian",
         "//absl/base:prefetch",
         "//absl/strings",
+        "//absl/strings:str_format",
     ],
 )
 
@@ -105,6 +106,7 @@ cc_test(
     deps = [
         ":crc32c",
         "//absl/strings",
+        "//absl/strings:str_format",
         "@com_google_googletest//:gtest_main",
     ],
 )
diff --git a/absl/crc/CMakeLists.txt b/absl/crc/CMakeLists.txt
index 72ea2094..21247160 100644
--- a/absl/crc/CMakeLists.txt
+++ b/absl/crc/CMakeLists.txt
@@ -77,6 +77,7 @@ absl_cc_library(
     absl::dynamic_annotations
     absl::endian
     absl::prefetch
+    absl::str_format
     absl::strings
 )
 
@@ -90,6 +91,7 @@ absl_cc_test(
   DEPS
     absl::crc32c
     absl::strings
+    absl::str_format
     GTest::gtest_main
 )
 
diff --git a/absl/crc/crc32c.h b/absl/crc/crc32c.h
index ba09e52a..362861e4 100644
--- a/absl/crc/crc32c.h
+++ b/absl/crc/crc32c.h
@@ -29,6 +29,7 @@
 #include <ostream>
 
 #include "absl/crc/internal/crc32c_inline.h"
+#include "absl/strings/str_format.h"
 #include "absl/strings/string_view.h"
 
 namespace absl {
@@ -61,10 +62,16 @@ class crc32c_t final {
 
   friend bool operator!=(crc32c_t lhs, crc32c_t rhs) { return !(lhs == rhs); }
 
+  template <typename Sink>
+  friend void AbslStringify(Sink& sink, crc32c_t crc) {
+    absl::Format(&sink, "%08x", static_cast<uint32_t>(crc));
+  }
+
  private:
   uint32_t crc_;
 };
 
+
 namespace crc_internal {
 // Non-inline code path for `absl::ExtendCrc32c()`. Do not call directly.
 // Call `absl::ExtendCrc32c()` (defined below) instead.
@@ -174,7 +181,7 @@ crc32c_t RemoveCrc32cSuffix(crc32c_t full_string_crc, crc32c_t suffix_crc,
 //
 // Streams the CRC32C value `crc` to the stream `os`.
 inline std::ostream& operator<<(std::ostream& os, crc32c_t crc) {
-  return os << static_cast<uint32_t>(crc);
+  return os << absl::StreamFormat("%08x", static_cast<uint32_t>(crc));
 }
 
 ABSL_NAMESPACE_END
diff --git a/absl/crc/crc32c_test.cc b/absl/crc/crc32c_test.cc
index 72d422a1..df0afb3e 100644
--- a/absl/crc/crc32c_test.cc
+++ b/absl/crc/crc32c_test.cc
@@ -18,11 +18,13 @@
 #include <cstddef>
 #include <cstdint>
 #include <cstring>
+#include <sstream>
 #include <string>
 
 #include "gtest/gtest.h"
 #include "absl/crc/internal/crc32c.h"
 #include "absl/strings/str_cat.h"
+#include "absl/strings/str_format.h"
 #include "absl/strings/string_view.h"
 
 namespace {
@@ -191,4 +193,35 @@ TEST(CRC32C, RemoveSuffix) {
 
   EXPECT_EQ(absl::RemoveCrc32cSuffix(crc_ab, crc_b, world.size()), crc_a);
 }
+
+TEST(CRC32C, InsertionOperator) {
+  {
+    std::ostringstream buf;
+    buf << absl::crc32c_t{0xc99465aa};
+    EXPECT_EQ(buf.str(), "c99465aa");
+  }
+  {
+    std::ostringstream buf;
+    buf << absl::crc32c_t{0};
+    EXPECT_EQ(buf.str(), "00000000");
+  }
+  {
+    std::ostringstream buf;
+    buf << absl::crc32c_t{17};
+    EXPECT_EQ(buf.str(), "00000011");
+  }
+}
+
+TEST(CRC32C, AbslStringify) {
+  // StrFormat
+  EXPECT_EQ(absl::StrFormat("%v", absl::crc32c_t{0xc99465aa}), "c99465aa");
+  EXPECT_EQ(absl::StrFormat("%v", absl::crc32c_t{0}), "00000000");
+  EXPECT_EQ(absl::StrFormat("%v", absl::crc32c_t{17}), "00000011");
+
+  // StrCat
+  EXPECT_EQ(absl::StrCat(absl::crc32c_t{0xc99465aa}), "c99465aa");
+  EXPECT_EQ(absl::StrCat(absl::crc32c_t{0}), "00000000");
+  EXPECT_EQ(absl::StrCat(absl::crc32c_t{17}), "00000011");
+}
+
 }  // namespace
diff --git a/absl/crc/internal/cpu_detect.cc b/absl/crc/internal/cpu_detect.cc
index d61b7018..83838085 100644
--- a/absl/crc/internal/cpu_detect.cc
+++ b/absl/crc/internal/cpu_detect.cc
@@ -28,15 +28,12 @@
 #include <intrin.h>
 #endif
 
-namespace absl {
-ABSL_NAMESPACE_BEGIN
-namespace crc_internal {
-
 #if defined(__x86_64__) || defined(_M_X64)
-
-namespace {
-
-#if !defined(_WIN32) && !defined(_WIN64)
+#if ABSL_HAVE_BUILTIN(__cpuid)
+// MSVC-equivalent __cpuid intrinsic declaration for clang-like compilers
+// for non-Windows build environments.
+extern void __cpuid(int[4], int);
+#elif !defined(_WIN32) && !defined(_WIN64)
 // MSVC defines this function for us.
 // https://learn.microsoft.com/en-us/cpp/intrinsics/cpuid-cpuidex
 static void __cpuid(int cpu_info[4], int info_type) {
@@ -46,6 +43,15 @@ static void __cpuid(int cpu_info[4], int info_type) {
                    : "a"(info_type), "c"(0));
 }
 #endif  // !defined(_WIN32) && !defined(_WIN64)
+#endif  // defined(__x86_64__) || defined(_M_X64)
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace crc_internal {
+
+#if defined(__x86_64__) || defined(_M_X64)
+
+namespace {
 
 enum class Vendor {
   kUnknown,
diff --git a/absl/crc/internal/crc.cc b/absl/crc/internal/crc.cc
index bb8936e3..22e91c53 100644
--- a/absl/crc/internal/crc.cc
+++ b/absl/crc/internal/crc.cc
@@ -44,8 +44,8 @@
 #include <cstdint>
 
 #include "absl/base/internal/endian.h"
-#include "absl/base/internal/prefetch.h"
 #include "absl/base/internal/raw_logging.h"
+#include "absl/base/prefetch.h"
 #include "absl/crc/internal/crc_internal.h"
 
 namespace absl {
@@ -176,9 +176,6 @@ CRCImpl* CRCImpl::NewInternal() {
   return result;
 }
 
-// The CRC of the empty string is always the CRC polynomial itself.
-void CRCImpl::Empty(uint32_t* crc) const { *crc = kCrc32cPoly; }
-
 //  The 32-bit implementation
 
 void CRC32::InitTables() {
@@ -261,7 +258,7 @@ void CRC32::Extend(uint32_t* crc, const void* bytes, size_t length) const {
   const uint8_t* e = p + length;
   uint32_t l = *crc;
 
-  auto step_one_byte = [this, &p, &l] () {
+  auto step_one_byte = [this, &p, &l]() {
     int c = (l & 0xff) ^ *p++;
     l = this->table0_[c] ^ (l >> 8);
   };
@@ -309,7 +306,7 @@ void CRC32::Extend(uint32_t* crc, const void* bytes, size_t length) const {
 
     // Process kStride interleaved swaths through the data in parallel.
     while ((e - p) > kPrefetchHorizon) {
-      base_internal::PrefetchNta(
+      PrefetchToLocalCacheNta(
           reinterpret_cast<const void*>(p + kPrefetchHorizon));
       // Process 64 bytes at a time
       step_stride();
@@ -359,7 +356,7 @@ void CRC32::Extend(uint32_t* crc, const void* bytes, size_t length) const {
 
 void CRC32::ExtendByZeroesImpl(uint32_t* crc, size_t length,
                                const uint32_t zeroes_table[256],
-                               const uint32_t poly_table[256]) const {
+                               const uint32_t poly_table[256]) {
   if (length != 0) {
     uint32_t l = *crc;
     // For each ZEROES_BASE_LG bits in length
@@ -435,34 +432,6 @@ CRC* CRC::Crc32c() {
   return singleton;
 }
 
-// This Concat implementation works for arbitrary polynomials.
-void CRC::Concat(uint32_t* px, uint32_t y, size_t ylen) {
-  // https://en.wikipedia.org/wiki/Mathematics_of_cyclic_redundancy_checks
-  // The CRC of a message M is the remainder of polynomial divison modulo G,
-  // where the coefficient arithmetic is performed modulo 2 (so +/- are XOR):
-  //   R(x) = M(x) x**n (mod G)
-  // (n is the degree of G)
-  // In practice, we use an initial value A and a bitmask B to get
-  //   R = (A ^ B)x**|M| ^ Mx**n ^ B (mod G)
-  // If M is the concatenation of two strings S and T, and Z is the string of
-  // len(T) 0s, then the remainder CRC(ST) can be expressed as:
-  //   R = (A ^ B)x**|ST| ^ STx**n ^ B
-  //     = (A ^ B)x**|SZ| ^ SZx**n ^ B ^ Tx**n
-  //     = CRC(SZ) ^ Tx**n
-  // CRC(Z) = (A ^ B)x**|T| ^ B
-  // CRC(T) = (A ^ B)x**|T| ^ Tx**n ^ B
-  // So R = CRC(SZ) ^ CRC(Z) ^ CRC(T)
-  //
-  // And further, since CRC(SZ) = Extend(CRC(S), Z),
-  //  CRC(SZ) ^ CRC(Z) = Extend(CRC(S) ^ CRC(''), Z).
-  uint32_t z;
-  uint32_t t;
-  Empty(&z);
-  t = *px ^ z;
-  ExtendByZeroes(&t, ylen);
-  *px = t ^ y;
-}
-
 }  // namespace crc_internal
 ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/crc/internal/crc.h b/absl/crc/internal/crc.h
index 72515b06..4efdd032 100644
--- a/absl/crc/internal/crc.h
+++ b/absl/crc/internal/crc.h
@@ -40,9 +40,6 @@ class CRC {
  public:
   virtual ~CRC();
 
-  // Place the CRC of the empty string in "*crc"
-  virtual void Empty(uint32_t* crc) const = 0;
-
   // If "*crc" is the CRC of bytestring A, place the CRC of
   // the bytestring formed from the concatenation of A and the "length"
   // bytes at "bytes" into "*crc".
@@ -53,22 +50,17 @@ class CRC {
   // points to an array of "length" zero bytes.
   virtual void ExtendByZeroes(uint32_t* crc, size_t length) const = 0;
 
-  // Inverse opration of ExtendByZeroes.  If `crc` is the CRC value of a string
+  // Inverse operation of ExtendByZeroes.  If `crc` is the CRC value of a string
   // ending in `length` zero bytes, this returns a CRC value of that string
   // with those zero bytes removed.
   virtual void UnextendByZeroes(uint32_t* crc, size_t length) const = 0;
 
-  // If *px is the CRC (as defined by *crc) of some string X,
-  // and y is the CRC of some string Y that is ylen bytes long, set
-  // *px to the CRC of the concatenation of X followed by Y.
-  virtual void Concat(uint32_t* px, uint32_t y, size_t ylen);
-
   // Apply a non-linear transformation to "*crc" so that
   // it is safe to CRC the result with the same polynomial without
   // any reduction of error-detection ability in the outer CRC.
   // Unscramble() performs the inverse transformation.
   // It is strongly recommended that CRCs be scrambled before storage or
-  // transmission, and unscrambled at the other end before futher manipulation.
+  // transmission, and unscrambled at the other end before further manipulation.
   virtual void Scramble(uint32_t* crc) const = 0;
   virtual void Unscramble(uint32_t* crc) const = 0;
 
diff --git a/absl/crc/internal/crc32_x86_arm_combined_simd.h b/absl/crc/internal/crc32_x86_arm_combined_simd.h
index fb643986..39e53dd0 100644
--- a/absl/crc/internal/crc32_x86_arm_combined_simd.h
+++ b/absl/crc/internal/crc32_x86_arm_combined_simd.h
@@ -33,7 +33,7 @@
 #include <x86intrin.h>
 #define ABSL_CRC_INTERNAL_HAVE_X86_SIMD
 
-#elif defined(_MSC_VER) && defined(__AVX__)
+#elif defined(_MSC_VER) && !defined(__clang__) && defined(__AVX__)
 
 // MSVC AVX (/arch:AVX) implies SSE 4.2 and PCLMULQDQ.
 #include <intrin.h>
diff --git a/absl/crc/internal/crc_cord_state.cc b/absl/crc/internal/crc_cord_state.cc
index d0be0ddd..28d04dc4 100644
--- a/absl/crc/internal/crc_cord_state.cc
+++ b/absl/crc/internal/crc_cord_state.cc
@@ -121,7 +121,7 @@ void CrcCordState::Poison() {
     }
   } else {
     // Add a fake corrupt chunk.
-    rep->prefix_crc.push_back(PrefixCrc(0, crc32c_t{1}));
+    rep->prefix_crc.emplace_back(0, crc32c_t{1});
   }
 }
 
diff --git a/absl/crc/internal/crc_cord_state.h b/absl/crc/internal/crc_cord_state.h
index d305424c..fbbb8c00 100644
--- a/absl/crc/internal/crc_cord_state.h
+++ b/absl/crc/internal/crc_cord_state.h
@@ -71,9 +71,9 @@ class CrcCordState {
   struct Rep {
     // `removed_prefix` is the crc and length of any prefix that has been
     // removed from the Cord (for example, by calling
-    // `CrcCord::RemovePrefix()`). To get the checkum of any prefix of the cord,
-    // this value must be subtracted from `prefix_crc`. See `Checksum()` for an
-    // example.
+    // `CrcCord::RemovePrefix()`). To get the checksum of any prefix of the
+    // cord, this value must be subtracted from `prefix_crc`. See `Checksum()`
+    // for an example.
     //
     // CrcCordState is said to be "normalized" if removed_prefix.length == 0.
     PrefixCrc removed_prefix;
@@ -109,7 +109,7 @@ class CrcCordState {
   // Returns true if the chunked CRC32C cached is normalized.
   bool IsNormalized() const { return rep().removed_prefix.length == 0; }
 
-  // Normalizes the chunked CRC32C checksum cache by substracting any removed
+  // Normalizes the chunked CRC32C checksum cache by subtracting any removed
   // prefix from the chunks.
   void Normalize();
 
diff --git a/absl/crc/internal/crc_internal.h b/absl/crc/internal/crc_internal.h
index 0611b383..4d3582d9 100644
--- a/absl/crc/internal/crc_internal.h
+++ b/absl/crc/internal/crc_internal.h
@@ -60,18 +60,16 @@ constexpr uint64_t kScrambleHi = (static_cast<uint64_t>(0x4f1bbcdcU) << 32) |
 constexpr uint64_t kScrambleLo = (static_cast<uint64_t>(0xf9ce6030U) << 32) |
                                  static_cast<uint64_t>(0x2e76e41bU);
 
-class CRCImpl : public CRC {  // Implemention of the abstract class CRC
+class CRCImpl : public CRC {  // Implementation of the abstract class CRC
  public:
   using Uint32By256 = uint32_t[256];
 
-  CRCImpl() {}
+  CRCImpl() = default;
   ~CRCImpl() override = default;
 
   // The internal version of CRC::New().
   static CRCImpl* NewInternal();
 
-  void Empty(uint32_t* crc) const override;
-
   // Fill in a table for updating a CRC by one word of 'word_size' bytes
   // [last_lo, last_hi] contains the answer if the last bit in the word
   // is set.
@@ -96,8 +94,8 @@ class CRCImpl : public CRC {  // Implemention of the abstract class CRC
 // This is the 32-bit implementation.  It handles all sizes from 8 to 32.
 class CRC32 : public CRCImpl {
  public:
-  CRC32() {}
-  ~CRC32() override {}
+  CRC32() = default;
+  ~CRC32() override = default;
 
   void Extend(uint32_t* crc, const void* bytes, size_t length) const override;
   void ExtendByZeroes(uint32_t* crc, size_t length) const override;
@@ -111,16 +109,16 @@ class CRC32 : public CRCImpl {
   // Common implementation guts for ExtendByZeroes and UnextendByZeroes().
   //
   // zeroes_table is a table as returned by FillZeroesTable(), containing
-  // polynomials representing CRCs of strings-of-zeros of various lenghts,
+  // polynomials representing CRCs of strings-of-zeros of various lengths,
   // and which can be combined by polynomial multiplication.  poly_table is
   // a table of CRC byte extension values.  These tables are determined by
   // the generator polynomial.
   //
   // These will be set to reverse_zeroes_ and reverse_table0_ for Unextend, and
   // CRC32::zeroes_ and CRC32::table0_ for Extend.
-  void ExtendByZeroesImpl(uint32_t* crc, size_t length,
-                          const uint32_t zeroes_table[256],
-                          const uint32_t poly_table[256]) const;
+  static void ExtendByZeroesImpl(uint32_t* crc, size_t length,
+                                 const uint32_t zeroes_table[256],
+                                 const uint32_t poly_table[256]);
 
   uint32_t table0_[256];  // table of byte extensions
   uint32_t zeroes_[256];  // table of zero extensions
diff --git a/absl/crc/internal/crc_memcpy_x86_64.cc b/absl/crc/internal/crc_memcpy_x86_64.cc
index 66f784de..d42b08dc 100644
--- a/absl/crc/internal/crc_memcpy_x86_64.cc
+++ b/absl/crc/internal/crc_memcpy_x86_64.cc
@@ -52,8 +52,8 @@
 #include <type_traits>
 
 #include "absl/base/dynamic_annotations.h"
-#include "absl/base/internal/prefetch.h"
 #include "absl/base/optimization.h"
+#include "absl/base/prefetch.h"
 #include "absl/crc/crc32c.h"
 #include "absl/crc/internal/cpu_detect.h"
 #include "absl/crc/internal/crc_memcpy.h"
@@ -242,10 +242,8 @@ crc32c_t AcceleratedCrcMemcpyEngine<vec_regions, int_regions>::Compute(
   while (copy_rounds > kBlocksPerCacheLine) {
     // Prefetch kPrefetchAhead bytes ahead of each pointer.
     for (size_t i = 0; i < kRegions; i++) {
-      absl::base_internal::PrefetchT0(src_bytes + kPrefetchAhead +
-                                      region_size * i);
-      absl::base_internal::PrefetchT0(dst_bytes + kPrefetchAhead +
-                                      region_size * i);
+      absl::PrefetchToLocalCache(src_bytes + kPrefetchAhead + region_size * i);
+      absl::PrefetchToLocalCache(dst_bytes + kPrefetchAhead + region_size * i);
     }
 
     // Load and store data, computing CRC on the way.
@@ -359,18 +357,18 @@ CrcMemcpy::ArchSpecificEngines CrcMemcpy::GetArchSpecificEngines() {
     case CpuType::kIntelHaswell:
     case CpuType::kIntelIvybridge:
       return {
-          .temporal = new FallbackCrcMemcpyEngine(),
-          .non_temporal = new CrcNonTemporalMemcpyAVXEngine(),
+          /*.temporal=*/new FallbackCrcMemcpyEngine(),
+          /*.non_temporal=*/new CrcNonTemporalMemcpyAVXEngine(),
       };
     // INTEL_SANDYBRIDGE performs better with SSE than AVX.
     case CpuType::kIntelSandybridge:
       return {
-          .temporal = new FallbackCrcMemcpyEngine(),
-          .non_temporal = new CrcNonTemporalMemcpyEngine(),
+          /*.temporal=*/new FallbackCrcMemcpyEngine(),
+          /*.non_temporal=*/new CrcNonTemporalMemcpyEngine(),
       };
     default:
-      return {.temporal = new FallbackCrcMemcpyEngine(),
-              .non_temporal = new FallbackCrcMemcpyEngine()};
+      return {/*.temporal=*/new FallbackCrcMemcpyEngine(),
+              /*.non_temporal=*/new FallbackCrcMemcpyEngine()};
   }
 #else
   // Get the underlying architecture.
@@ -388,8 +386,8 @@ CrcMemcpy::ArchSpecificEngines CrcMemcpy::GetArchSpecificEngines() {
     case CpuType::kAmdRome:
     case CpuType::kAmdNaples:
       return {
-          .temporal = new AcceleratedCrcMemcpyEngine<1, 2>(),
-          .non_temporal = new CrcNonTemporalMemcpyAVXEngine(),
+          /*.temporal=*/new AcceleratedCrcMemcpyEngine<1, 2>(),
+          /*.non_temporal=*/new CrcNonTemporalMemcpyAVXEngine(),
       };
     // PCLMULQDQ is slow and we don't have wide enough issue width to take
     // advantage of it.  For an unknown architecture, don't risk using CLMULs.
@@ -400,18 +398,18 @@ CrcMemcpy::ArchSpecificEngines CrcMemcpy::GetArchSpecificEngines() {
     case CpuType::kIntelHaswell:
     case CpuType::kIntelIvybridge:
       return {
-          .temporal = new AcceleratedCrcMemcpyEngine<3, 0>(),
-          .non_temporal = new CrcNonTemporalMemcpyAVXEngine(),
+          /*.temporal=*/new AcceleratedCrcMemcpyEngine<3, 0>(),
+          /*.non_temporal=*/new CrcNonTemporalMemcpyAVXEngine(),
       };
     // INTEL_SANDYBRIDGE performs better with SSE than AVX.
     case CpuType::kIntelSandybridge:
       return {
-          .temporal = new AcceleratedCrcMemcpyEngine<3, 0>(),
-          .non_temporal = new CrcNonTemporalMemcpyEngine(),
+          /*.temporal=*/new AcceleratedCrcMemcpyEngine<3, 0>(),
+          /*.non_temporal=*/new CrcNonTemporalMemcpyEngine(),
       };
     default:
-      return {.temporal = new FallbackCrcMemcpyEngine(),
-              .non_temporal = new FallbackCrcMemcpyEngine()};
+      return {/*.temporal=*/new FallbackCrcMemcpyEngine(),
+              /*.non_temporal=*/new FallbackCrcMemcpyEngine()};
   }
 #endif  // UNDEFINED_BEHAVIOR_SANITIZER
 }
diff --git a/absl/crc/internal/crc_x86_arm_combined.cc b/absl/crc/internal/crc_x86_arm_combined.cc
index d71191e3..ef521d22 100644
--- a/absl/crc/internal/crc_x86_arm_combined.cc
+++ b/absl/crc/internal/crc_x86_arm_combined.cc
@@ -21,7 +21,7 @@
 #include "absl/base/config.h"
 #include "absl/base/dynamic_annotations.h"
 #include "absl/base/internal/endian.h"
-#include "absl/base/internal/prefetch.h"
+#include "absl/base/prefetch.h"
 #include "absl/crc/internal/cpu_detect.h"
 #include "absl/crc/internal/crc.h"
 #include "absl/crc/internal/crc32_x86_arm_combined_simd.h"
@@ -429,11 +429,11 @@ class CRC32AcceleratedX86ARMCombinedMultipleStreams
           ABSL_INTERNAL_STEP8BY3(l64, l641, l642, p, p1, p2);
           ABSL_INTERNAL_STEP8BY3(l64, l641, l642, p, p1, p2);
           ABSL_INTERNAL_STEP8BY3(l64, l641, l642, p, p1, p2);
-          base_internal::PrefetchT0(
+          PrefetchToLocalCache(
               reinterpret_cast<const char*>(p + kPrefetchHorizonMedium));
-          base_internal::PrefetchT0(
+          PrefetchToLocalCache(
               reinterpret_cast<const char*>(p1 + kPrefetchHorizonMedium));
-          base_internal::PrefetchT0(
+          PrefetchToLocalCache(
               reinterpret_cast<const char*>(p2 + kPrefetchHorizonMedium));
         }
         // Don't run crc on last 8 bytes.
@@ -515,14 +515,14 @@ class CRC32AcceleratedX86ARMCombinedMultipleStreams
       }
 
       for (size_t i = 1; i < bs; i++) {
-        // Prefetch data for next itterations.
+        // Prefetch data for next iterations.
         for (size_t j = 0; j < num_crc_streams; j++) {
-          base_internal::PrefetchT0(
+          PrefetchToLocalCache(
               reinterpret_cast<const char*>(crc_streams[j] + kPrefetchHorizon));
         }
         for (size_t j = 0; j < num_pclmul_streams; j++) {
-          base_internal::PrefetchT0(reinterpret_cast<const char*>(
-              pclmul_streams[j] + kPrefetchHorizon));
+          PrefetchToLocalCache(reinterpret_cast<const char*>(pclmul_streams[j] +
+                                                             kPrefetchHorizon));
         }
 
         // We process each stream in 64 byte blocks. This can be written as
diff --git a/absl/debugging/BUILD.bazel b/absl/debugging/BUILD.bazel
index edbb3698..42124bfb 100644
--- a/absl/debugging/BUILD.bazel
+++ b/absl/debugging/BUILD.bazel
@@ -49,6 +49,7 @@ cc_library(
         ":debugging_internal",
         "//absl/base:config",
         "//absl/base:core_headers",
+        "//absl/base:dynamic_annotations",
         "//absl/base:raw_logging_internal",
     ],
 )
@@ -83,6 +84,10 @@ cc_library(
     linkopts = ABSL_DEFAULT_LINKOPTS + select({
         "//absl:msvc_compiler": ["-DEFAULTLIB:dbghelp.lib"],
         "//absl:clang-cl_compiler": ["-DEFAULTLIB:dbghelp.lib"],
+        "//absl:mingw_compiler": [
+            "-DEFAULTLIB:dbghelp.lib",
+            "-ldbghelp",
+        ],
         "//conditions:default": [],
     }),
     deps = [
@@ -117,7 +122,8 @@ cc_test(
         "//absl/base",
         "//absl/base:config",
         "//absl/base:core_headers",
-        "//absl/base:raw_logging_internal",
+        "//absl/log",
+        "//absl/log:check",
         "//absl/memory",
         "//absl/strings",
         "@com_google_googletest//:gtest",
@@ -175,6 +181,7 @@ cc_test(
         ":stacktrace",
         ":symbolize",
         "//absl/base:raw_logging_internal",
+        "//absl/log:check",
         "//absl/strings",
         "@com_google_googletest//:gtest",
     ],
@@ -228,7 +235,7 @@ cc_test(
         ":stack_consumption",
         "//absl/base:config",
         "//absl/base:core_headers",
-        "//absl/base:raw_logging_internal",
+        "//absl/log",
         "//absl/memory",
         "@com_google_googletest//:gtest_main",
     ],
@@ -255,7 +262,7 @@ cc_test(
     deps = [
         ":leak_check",
         "//absl/base:config",
-        "//absl/base:raw_logging_internal",
+        "//absl/log",
         "@com_google_googletest//:gtest_main",
     ],
 )
@@ -272,7 +279,7 @@ cc_binary(
     linkopts = ABSL_DEFAULT_LINKOPTS,
     deps = [
         ":leak_check",
-        "//absl/base:raw_logging_internal",
+        "//absl/log",
         "@com_google_googletest//:gtest_main",
     ],
 )
@@ -301,7 +308,7 @@ cc_test(
     deps = [
         ":stack_consumption",
         "//absl/base:core_headers",
-        "//absl/base:raw_logging_internal",
+        "//absl/log",
         "@com_google_googletest//:gtest_main",
     ],
 )
diff --git a/absl/debugging/CMakeLists.txt b/absl/debugging/CMakeLists.txt
index 8f29cc07..65e2af88 100644
--- a/absl/debugging/CMakeLists.txt
+++ b/absl/debugging/CMakeLists.txt
@@ -41,6 +41,7 @@ absl_cc_library(
     absl::debugging_internal
     absl::config
     absl::core_headers
+    absl::dynamic_annotations
     absl::raw_logging_internal
   PUBLIC
 )
@@ -100,14 +101,15 @@ absl_cc_test(
   LINKOPTS
     $<$<BOOL:${MSVC}>:-DEBUG>
   DEPS
-    absl::stack_consumption
-    absl::symbolize
     absl::base
+    absl::check
     absl::config
     absl::core_headers
+    absl::log
     absl::memory
-    absl::raw_logging_internal
+    absl::stack_consumption
     absl::strings
+    absl::symbolize
     GTest::gmock
 )
 
@@ -156,6 +158,7 @@ absl_cc_test(
   COPTS
     ${ABSL_TEST_COPTS}
   DEPS
+    absl::check
     absl::failure_signal_handler
     absl::stacktrace
     absl::symbolize
@@ -215,8 +218,8 @@ absl_cc_test(
     absl::stack_consumption
     absl::config
     absl::core_headers
+    absl::log
     absl::memory
-    absl::raw_logging_internal
     GTest::gmock_main
 )
 
@@ -247,6 +250,7 @@ absl_cc_test(
   DEPS
     absl::leak_check
     absl::base
+    absl::log
     GTest::gmock_main
 )
 
@@ -277,7 +281,7 @@ absl_cc_test(
   DEPS
     absl::stack_consumption
     absl::core_headers
-    absl::raw_logging_internal
+    absl::log
     GTest::gmock_main
 )
 
diff --git a/absl/debugging/failure_signal_handler.cc b/absl/debugging/failure_signal_handler.cc
index ef8ab9e5..992c89c3 100644
--- a/absl/debugging/failure_signal_handler.cc
+++ b/absl/debugging/failure_signal_handler.cc
@@ -31,6 +31,13 @@
 
 #ifdef ABSL_HAVE_MMAP
 #include <sys/mman.h>
+#if defined(MAP_ANON) && !defined(MAP_ANONYMOUS)
+#define MAP_ANONYMOUS MAP_ANON
+#endif
+#endif
+
+#ifdef __linux__
+#include <sys/prctl.h>
 #endif
 
 #include <algorithm>
@@ -77,10 +84,10 @@ struct FailureSignalData {
   struct sigaction previous_action;
   // StructSigaction is used to silence -Wmissing-field-initializers.
   using StructSigaction = struct sigaction;
-  #define FSD_PREVIOUS_INIT FailureSignalData::StructSigaction()
+#define FSD_PREVIOUS_INIT FailureSignalData::StructSigaction()
 #else
   void (*previous_handler)(int);
-  #define FSD_PREVIOUS_INIT SIG_DFL
+#define FSD_PREVIOUS_INIT SIG_DFL
 #endif
 };
 
@@ -132,7 +139,7 @@ const char* FailureSignalToString(int signo) {
 #ifdef ABSL_HAVE_SIGALTSTACK
 
 static bool SetupAlternateStackOnce() {
-#if defined(__wasm__) || defined (__asjms__)
+#if defined(__wasm__) || defined(__asjms__)
   const size_t page_mask = getpagesize() - 1;
 #else
   const size_t page_mask = static_cast<size_t>(sysconf(_SC_PAGESIZE)) - 1;
@@ -154,9 +161,6 @@ static bool SetupAlternateStackOnce() {
 #ifndef MAP_STACK
 #define MAP_STACK 0
 #endif
-#if defined(MAP_ANON) && !defined(MAP_ANONYMOUS)
-#define MAP_ANONYMOUS MAP_ANON
-#endif
   sigstk.ss_sp = mmap(nullptr, sigstk.ss_size, PROT_READ | PROT_WRITE,
                       MAP_PRIVATE | MAP_ANONYMOUS | MAP_STACK, -1, 0);
   if (sigstk.ss_sp == MAP_FAILED) {
@@ -172,6 +176,20 @@ static bool SetupAlternateStackOnce() {
   if (sigaltstack(&sigstk, nullptr) != 0) {
     ABSL_RAW_LOG(FATAL, "sigaltstack() failed with errno=%d", errno);
   }
+
+#ifdef __linux__
+#if defined(PR_SET_VMA) && defined(PR_SET_VMA_ANON_NAME)
+  // Make a best-effort attempt to name the allocated region in
+  // /proc/$PID/smaps.
+  //
+  // The call to prctl() may fail if the kernel was not configured with the
+  // CONFIG_ANON_VMA_NAME kernel option.  This is OK since the call is
+  // primarily a debugging aid.
+  prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, sigstk.ss_sp, sigstk.ss_size,
+        "absl-signalstack");
+#endif
+#endif  // __linux__
+
   return true;
 }
 
@@ -218,10 +236,6 @@ static void InstallOneFailureHandler(FailureSignalData* data,
 
 #endif
 
-static void WriteToStderr(const char* data) {
-  absl::raw_log_internal::AsyncSignalSafeWriteToStderr(data, strlen(data));
-}
-
 static void WriteSignalMessage(int signo, int cpu,
                                void (*writerfn)(const char*)) {
   char buf[96];
@@ -234,7 +248,7 @@ static void WriteSignalMessage(int signo, int cpu,
   if (signal_string != nullptr && signal_string[0] != '\0') {
     snprintf(buf, sizeof(buf), "*** %s received at time=%ld%s ***\n",
              signal_string,
-             static_cast<long>(time(nullptr)),   // NOLINT(runtime/int)
+             static_cast<long>(time(nullptr)),  // NOLINT(runtime/int)
              on_cpu);
   } else {
     snprintf(buf, sizeof(buf), "*** Signal %d received at time=%ld%s ***\n",
@@ -297,7 +311,8 @@ static void PortableSleepForSeconds(int seconds) {
   struct timespec sleep_time;
   sleep_time.tv_sec = seconds;
   sleep_time.tv_nsec = 0;
-  while (nanosleep(&sleep_time, &sleep_time) != 0 && errno == EINTR) {}
+  while (nanosleep(&sleep_time, &sleep_time) != 0 && errno == EINTR) {
+  }
 #endif
 }
 
@@ -307,9 +322,7 @@ static void PortableSleepForSeconds(int seconds) {
 // set amount of time. If AbslFailureSignalHandler() hangs for more than
 // the alarm timeout, ImmediateAbortSignalHandler() will abort the
 // program.
-static void ImmediateAbortSignalHandler(int) {
-  RaiseToDefaultHandler(SIGABRT);
-}
+static void ImmediateAbortSignalHandler(int) { RaiseToDefaultHandler(SIGABRT); }
 #endif
 
 // absl::base_internal::GetTID() returns pid_t on most platforms, but
@@ -362,7 +375,10 @@ static void AbslFailureSignalHandler(int signo, siginfo_t*, void* ucontext) {
 #endif
 
   // First write to stderr.
-  WriteFailureInfo(signo, ucontext, my_cpu, WriteToStderr);
+  WriteFailureInfo(
+      signo, ucontext, my_cpu, +[](const char* data) {
+        absl::raw_log_internal::AsyncSignalSafeWriteError(data, strlen(data));
+      });
 
   // Riskier code (because it is less likely to be async-signal-safe)
   // goes after this point.
diff --git a/absl/debugging/failure_signal_handler.h b/absl/debugging/failure_signal_handler.h
index 500115c0..5e034785 100644
--- a/absl/debugging/failure_signal_handler.h
+++ b/absl/debugging/failure_signal_handler.h
@@ -62,7 +62,7 @@ struct FailureSignalHandlerOptions {
   // If true, try to run signal handlers on an alternate stack (if supported on
   // the given platform). An alternate stack is useful for program crashes due
   // to a stack overflow; by running on a alternate stack, the signal handler
-  // may run even when normal stack space has been exausted. The downside of
+  // may run even when normal stack space has been exhausted. The downside of
   // using an alternate stack is that extra memory for the alternate stack needs
   // to be pre-allocated.
   bool use_alternate_stack = true;
diff --git a/absl/debugging/failure_signal_handler_test.cc b/absl/debugging/failure_signal_handler_test.cc
index 6a62428b..72816a3e 100644
--- a/absl/debugging/failure_signal_handler_test.cc
+++ b/absl/debugging/failure_signal_handler_test.cc
@@ -22,11 +22,12 @@
 #include <cstring>
 #include <fstream>
 
-#include "gtest/gtest.h"
 #include "gmock/gmock.h"
+#include "gtest/gtest.h"
 #include "absl/base/internal/raw_logging.h"
 #include "absl/debugging/stacktrace.h"
 #include "absl/debugging/symbolize.h"
+#include "absl/log/check.h"
 #include "absl/strings/match.h"
 #include "absl/strings/str_cat.h"
 
@@ -87,7 +88,7 @@ std::string GetTmpDir() {
 // This function runs in a fork()ed process on most systems.
 void InstallHandlerWithWriteToFileAndRaise(const char* file, int signo) {
   error_file = fopen(file, "w");
-  ABSL_RAW_CHECK(error_file != nullptr, "Failed create error_file");
+  CHECK_NE(error_file, nullptr) << "Failed create error_file";
   absl::FailureSignalHandlerOptions options;
   options.writerfn = WriteToErrorFile;
   absl::InstallFailureSignalHandler(options);
diff --git a/absl/debugging/internal/demangle_test.cc b/absl/debugging/internal/demangle_test.cc
index 8463a2b7..faec72b5 100644
--- a/absl/debugging/internal/demangle_test.cc
+++ b/absl/debugging/internal/demangle_test.cc
@@ -19,8 +19,8 @@
 
 #include "gtest/gtest.h"
 #include "absl/base/config.h"
-#include "absl/base/internal/raw_logging.h"
 #include "absl/debugging/internal/stack_consumption.h"
+#include "absl/log/log.h"
 #include "absl/memory/memory.h"
 
 namespace absl {
@@ -38,7 +38,7 @@ static const char *DemangleIt(const char * const mangled) {
   }
 }
 
-// Test corner cases of bounary conditions.
+// Test corner cases of boundary conditions.
 TEST(Demangle, CornerCases) {
   char tmp[10];
   EXPECT_TRUE(Demangle("_Z6foobarv", tmp, sizeof(tmp)));
@@ -151,7 +151,7 @@ static const char *DemangleStackConsumption(const char *mangled,
                                             int *stack_consumed) {
   g_mangled = mangled;
   *stack_consumed = GetSignalHandlerStackConsumption(DemangleSignalHandler);
-  ABSL_RAW_LOG(INFO, "Stack consumption of Demangle: %d", *stack_consumed);
+  LOG(INFO) << "Stack consumption of Demangle: " << *stack_consumed;
   return g_demangle_result;
 }
 
diff --git a/absl/debugging/internal/elf_mem_image.h b/absl/debugging/internal/elf_mem_image.h
index 113071a9..e7fe6ab0 100644
--- a/absl/debugging/internal/elf_mem_image.h
+++ b/absl/debugging/internal/elf_mem_image.h
@@ -33,7 +33,8 @@
 
 #if defined(__ELF__) && !defined(__OpenBSD__) && !defined(__QNX__) && \
     !defined(__native_client__) && !defined(__asmjs__) &&             \
-    !defined(__wasm__) && !defined(__HAIKU__)
+    !defined(__wasm__) && !defined(__HAIKU__) && !defined(__sun) &&   \
+    !defined(__VXWORKS__) && !defined(__hexagon__)
 #define ABSL_HAVE_ELF_MEM_IMAGE 1
 #endif
 
diff --git a/absl/debugging/internal/examine_stack.cc b/absl/debugging/internal/examine_stack.cc
index 57863228..3dd6ba1a 100644
--- a/absl/debugging/internal/examine_stack.cc
+++ b/absl/debugging/internal/examine_stack.cc
@@ -24,6 +24,9 @@
 
 #ifdef ABSL_HAVE_MMAP
 #include <sys/mman.h>
+#if defined(MAP_ANON) && !defined(MAP_ANONYMOUS)
+#define MAP_ANONYMOUS MAP_ANON
+#endif
 #endif
 
 #if defined(__linux__) || defined(__APPLE__)
diff --git a/absl/debugging/internal/stack_consumption.cc b/absl/debugging/internal/stack_consumption.cc
index 51348649..3f40beac 100644
--- a/absl/debugging/internal/stack_consumption.cc
+++ b/absl/debugging/internal/stack_consumption.cc
@@ -18,14 +18,17 @@
 #ifdef ABSL_INTERNAL_HAVE_DEBUGGING_STACK_CONSUMPTION
 
 #include <signal.h>
+#include <string.h>
 #include <sys/mman.h>
 #include <unistd.h>
 
-#include <string.h>
-
 #include "absl/base/attributes.h"
 #include "absl/base/internal/raw_logging.h"
 
+#if defined(MAP_ANON) && !defined(MAP_ANONYMOUS)
+#define MAP_ANONYMOUS MAP_ANON
+#endif
+
 namespace absl {
 ABSL_NAMESPACE_BEGIN
 namespace debugging_internal {
@@ -162,7 +165,7 @@ int GetSignalHandlerStackConsumption(void (*signal_handler)(int)) {
     // versions of musl have a bug that rejects ss_size==0. Work around this by
     // setting ss_size to MINSIGSTKSZ, which should be ignored by the kernel
     // when SS_DISABLE is set.
-    old_sigstk.ss_size = MINSIGSTKSZ;
+    old_sigstk.ss_size = static_cast<size_t>(MINSIGSTKSZ);
   }
   ABSL_RAW_CHECK(sigaltstack(&old_sigstk, nullptr) == 0,
                  "sigaltstack() failed");
diff --git a/absl/debugging/internal/stack_consumption_test.cc b/absl/debugging/internal/stack_consumption_test.cc
index 80445bf4..0255ac8f 100644
--- a/absl/debugging/internal/stack_consumption_test.cc
+++ b/absl/debugging/internal/stack_consumption_test.cc
@@ -20,7 +20,7 @@
 #include <string.h>
 
 #include "gtest/gtest.h"
-#include "absl/base/internal/raw_logging.h"
+#include "absl/log/log.h"
 
 namespace absl {
 ABSL_NAMESPACE_BEGIN
@@ -33,7 +33,7 @@ static void SimpleSignalHandler(int signo) {
 
   // Never true, but prevents compiler from optimizing buf out.
   if (signo == 0) {
-    ABSL_RAW_LOG(INFO, "%p", static_cast<void*>(buf));
+    LOG(INFO) << static_cast<void*>(buf);
   }
 }
 
diff --git a/absl/debugging/internal/stacktrace_aarch64-inl.inc b/absl/debugging/internal/stacktrace_aarch64-inl.inc
index 71cdaf09..3f087162 100644
--- a/absl/debugging/internal/stacktrace_aarch64-inl.inc
+++ b/absl/debugging/internal/stacktrace_aarch64-inl.inc
@@ -13,6 +13,7 @@
 #include <cassert>
 #include <cstdint>
 #include <iostream>
+#include <limits>
 
 #include "absl/base/attributes.h"
 #include "absl/debugging/internal/address_is_readable.h"
@@ -20,6 +21,10 @@
 #include "absl/debugging/stacktrace.h"
 
 static const size_t kUnknownFrameSize = 0;
+// Stack end to use when we don't know the actual stack end
+// (effectively just the end of address space).
+constexpr uintptr_t kUnknownStackEnd =
+    std::numeric_limits<size_t>::max() - sizeof(void *);
 
 #if defined(__linux__)
 // Returns the address of the VDSO __kernel_rt_sigreturn function, if present.
@@ -79,8 +84,9 @@ static inline size_t ComputeStackFrameSize(const T* low,
 // "STRICT_UNWINDING") to reduce the chance that a bad pointer is returned.
 template<bool STRICT_UNWINDING, bool WITH_CONTEXT>
 ABSL_ATTRIBUTE_NO_SANITIZE_ADDRESS  // May read random elements from stack.
-ABSL_ATTRIBUTE_NO_SANITIZE_MEMORY   // May read random elements from stack.
-static void **NextStackFrame(void **old_frame_pointer, const void *uc) {
+ABSL_ATTRIBUTE_NO_SANITIZE_MEMORY  // May read random elements from stack.
+static void **NextStackFrame(void **old_frame_pointer, const void *uc,
+                             size_t stack_low, size_t stack_high) {
   void **new_frame_pointer = reinterpret_cast<void**>(*old_frame_pointer);
   bool check_frame_size = true;
 
@@ -94,16 +100,21 @@ static void **NextStackFrame(void **old_frame_pointer, const void *uc) {
       void **const pre_signal_frame_pointer =
           reinterpret_cast<void **>(ucv->uc_mcontext.regs[29]);
 
+      // The most recent signal always needs special handling to find the frame
+      // pointer, but a nested signal does not.  If pre_signal_frame_pointer is
+      // earlier in the stack than the old_frame_pointer, then use it. If it is
+      // later, then we have already unwound through it and it needs no special
+      // handling.
+      if (pre_signal_frame_pointer >= old_frame_pointer) {
+        new_frame_pointer = pre_signal_frame_pointer;
+      }
       // Check that alleged frame pointer is actually readable. This is to
       // prevent "double fault" in case we hit the first fault due to e.g.
       // stack corruption.
       if (!absl::debugging_internal::AddressIsReadable(
-              pre_signal_frame_pointer))
+              new_frame_pointer))
         return nullptr;
 
-      // Alleged frame pointer is readable, use it for further unwinding.
-      new_frame_pointer = pre_signal_frame_pointer;
-
       // Skip frame size check if we return from a signal. We may be using a
       // an alternate stack for signals.
       check_frame_size = false;
@@ -121,8 +132,26 @@ static void **NextStackFrame(void **old_frame_pointer, const void *uc) {
     const size_t max_size = STRICT_UNWINDING ? 100000 : 1000000;
     const size_t frame_size =
         ComputeStackFrameSize(old_frame_pointer, new_frame_pointer);
-    if (frame_size == kUnknownFrameSize || frame_size > max_size)
-      return nullptr;
+    if (frame_size == kUnknownFrameSize)
+       return nullptr;
+    // A very large frame may mean corrupt memory or an erroneous frame
+    // pointer. But also maybe just a plain-old large frame.  Assume that if the
+    // frame is within the known stack, then it is valid.
+    if (frame_size > max_size) {
+       if (stack_high < kUnknownStackEnd &&
+          static_cast<size_t>(getpagesize()) < stack_low) {
+        const uintptr_t new_fp_u =
+            reinterpret_cast<uintptr_t>(new_frame_pointer);
+        // Stack bounds are known.
+        if (!(stack_low < new_fp_u && new_fp_u <= stack_high)) {
+          // new_frame_pointer is not within the known stack.
+          return nullptr;
+        }
+      } else {
+        // Stack bounds are unknown, prefer truncated stack to possible crash.
+        return nullptr;
+      }
+    }
   }
 
   return new_frame_pointer;
@@ -138,42 +167,49 @@ static int UnwindImpl(void** result, int* sizes, int max_depth, int skip_count,
 #else
 # error reading stack point not yet supported on this platform.
 #endif
-
   skip_count++;    // Skip the frame for this function.
   int n = 0;
 
+  // Assume that the first page is not stack.
+  size_t stack_low = static_cast<size_t>(getpagesize());
+  size_t stack_high = kUnknownStackEnd;
+
   // The frame pointer points to low address of a frame.  The first 64-bit
   // word of a frame points to the next frame up the call chain, which normally
   // is just after the high address of the current frame.  The second word of
-  // a frame contains return adress of to the caller.   To find a pc value
+  // a frame contains return address of to the caller.   To find a pc value
   // associated with the current frame, we need to go down a level in the call
   // chain.  So we remember return the address of the last frame seen.  This
   // does not work for the first stack frame, which belongs to UnwindImp() but
   // we skip the frame for UnwindImp() anyway.
   void* prev_return_address = nullptr;
+  // The nth frame size is the difference between the nth frame pointer and the
+  // the frame pointer below it in the call chain. There is no frame below the
+  // leaf frame, but this function is the leaf anyway, and we skip it.
+  void** prev_frame_pointer = nullptr;
 
-  while (frame_pointer && n < max_depth) {
-    // The absl::GetStackFrames routine is called when we are in some
-    // informational context (the failure signal handler for example).
-    // Use the non-strict unwinding rules to produce a stack trace
-    // that is as complete as possible (even if it contains a few bogus
-    // entries in some rare cases).
-    void **next_frame_pointer =
-        NextStackFrame<!IS_STACK_FRAMES, IS_WITH_CONTEXT>(frame_pointer, ucp);
-
+   while (frame_pointer && n < max_depth) {
     if (skip_count > 0) {
       skip_count--;
     } else {
       result[n] = prev_return_address;
       if (IS_STACK_FRAMES) {
         sizes[n] = static_cast<int>(
-            ComputeStackFrameSize(frame_pointer, next_frame_pointer));
+            ComputeStackFrameSize(prev_frame_pointer, frame_pointer));
       }
       n++;
     }
     prev_return_address = frame_pointer[1];
-    frame_pointer = next_frame_pointer;
+    prev_frame_pointer = frame_pointer;
+    // The absl::GetStackFrames routine is called when we are in some
+    // informational context (the failure signal handler for example).
+    // Use the non-strict unwinding rules to produce a stack trace
+    // that is as complete as possible (even if it contains a few bogus
+    // entries in some rare cases).
+    frame_pointer = NextStackFrame<!IS_STACK_FRAMES, IS_WITH_CONTEXT>(
+        frame_pointer, ucp, stack_low, stack_high);
   }
+
   if (min_dropped_frames != nullptr) {
     // Implementation detail: we clamp the max of frames we are willing to
     // count, so as not to spend too much time in the loop below.
@@ -185,8 +221,8 @@ static int UnwindImpl(void** result, int* sizes, int max_depth, int skip_count,
       } else {
         num_dropped_frames++;
       }
-      frame_pointer =
-          NextStackFrame<!IS_STACK_FRAMES, IS_WITH_CONTEXT>(frame_pointer, ucp);
+      frame_pointer = NextStackFrame<!IS_STACK_FRAMES, IS_WITH_CONTEXT>(
+          frame_pointer, ucp, stack_low, stack_high);
     }
     *min_dropped_frames = num_dropped_frames;
   }
diff --git a/absl/debugging/internal/stacktrace_powerpc-inl.inc b/absl/debugging/internal/stacktrace_powerpc-inl.inc
index 085cef67..a49ed2f7 100644
--- a/absl/debugging/internal/stacktrace_powerpc-inl.inc
+++ b/absl/debugging/internal/stacktrace_powerpc-inl.inc
@@ -57,7 +57,7 @@ static inline void *StacktracePowerPCGetLR(void **sp) {
   // This check is in case the compiler doesn't define _CALL_SYSV.
   return *(sp+1);
 #else
-#error Need to specify the PPC ABI for your archiecture.
+#error Need to specify the PPC ABI for your architecture.
 #endif
 }
 
diff --git a/absl/debugging/internal/stacktrace_x86-inl.inc b/absl/debugging/internal/stacktrace_x86-inl.inc
index 7b26464e..1975ba74 100644
--- a/absl/debugging/internal/stacktrace_x86-inl.inc
+++ b/absl/debugging/internal/stacktrace_x86-inl.inc
@@ -40,7 +40,7 @@ using absl::debugging_internal::AddressIsReadable;
 
 #if defined(__linux__) && defined(__i386__)
 // Count "push %reg" instructions in VDSO __kernel_vsyscall(),
-// preceeding "syscall" or "sysenter".
+// preceding "syscall" or "sysenter".
 // If __kernel_vsyscall uses frame pointer, answer 0.
 //
 // kMaxBytes tells how many instruction bytes of __kernel_vsyscall
diff --git a/absl/debugging/internal/symbolize.h b/absl/debugging/internal/symbolize.h
index 27d5e652..5593fde6 100644
--- a/absl/debugging/internal/symbolize.h
+++ b/absl/debugging/internal/symbolize.h
@@ -115,7 +115,7 @@ bool RemoveSymbolDecorator(int ticket);
 
 // Remove all installed decorators.  Returns true if successful, false if
 // symbolization is currently in progress.
-bool RemoveAllSymbolDecorators(void);
+bool RemoveAllSymbolDecorators();
 
 // Registers an address range to a file mapping.
 //
diff --git a/absl/debugging/leak_check.cc b/absl/debugging/leak_check.cc
index 195e82bf..fdb8798b 100644
--- a/absl/debugging/leak_check.cc
+++ b/absl/debugging/leak_check.cc
@@ -65,8 +65,8 @@ bool LeakCheckerIsActive() { return false; }
 void DoIgnoreLeak(const void*) { }
 void RegisterLivePointers(const void*, size_t) { }
 void UnRegisterLivePointers(const void*, size_t) { }
-LeakCheckDisabler::LeakCheckDisabler() { }
-LeakCheckDisabler::~LeakCheckDisabler() { }
+LeakCheckDisabler::LeakCheckDisabler() = default;
+LeakCheckDisabler::~LeakCheckDisabler() = default;
 ABSL_NAMESPACE_END
 }  // namespace absl
 
diff --git a/absl/debugging/leak_check_fail_test.cc b/absl/debugging/leak_check_fail_test.cc
index c49b81a9..46e9fb62 100644
--- a/absl/debugging/leak_check_fail_test.cc
+++ b/absl/debugging/leak_check_fail_test.cc
@@ -13,9 +13,10 @@
 // limitations under the License.
 
 #include <memory>
+
 #include "gtest/gtest.h"
-#include "absl/base/internal/raw_logging.h"
 #include "absl/debugging/leak_check.h"
+#include "absl/log/log.h"
 
 namespace {
 
@@ -25,7 +26,7 @@ TEST(LeakCheckTest, LeakMemory) {
   // failed exit code.
 
   char* foo = strdup("lsan should complain about this leaked string");
-  ABSL_RAW_LOG(INFO, "Should detect leaked string %s", foo);
+  LOG(INFO) << "Should detect leaked string " << foo;
 }
 
 TEST(LeakCheckTest, LeakMemoryAfterDisablerScope) {
@@ -34,8 +35,7 @@ TEST(LeakCheckTest, LeakMemoryAfterDisablerScope) {
   // failed exit code.
   { absl::LeakCheckDisabler disabler; }
   char* foo = strdup("lsan should also complain about this leaked string");
-  ABSL_RAW_LOG(INFO, "Re-enabled leak detection.Should detect leaked string %s",
-               foo);
+  LOG(INFO) << "Re-enabled leak detection.Should detect leaked string " << foo;
 }
 
 }  // namespace
diff --git a/absl/debugging/leak_check_test.cc b/absl/debugging/leak_check_test.cc
index 6a42e31b..6f0135ed 100644
--- a/absl/debugging/leak_check_test.cc
+++ b/absl/debugging/leak_check_test.cc
@@ -16,8 +16,8 @@
 
 #include "gtest/gtest.h"
 #include "absl/base/config.h"
-#include "absl/base/internal/raw_logging.h"
 #include "absl/debugging/leak_check.h"
+#include "absl/log/log.h"
 
 namespace {
 
@@ -26,7 +26,7 @@ TEST(LeakCheckTest, IgnoreLeakSuppressesLeakedMemoryErrors) {
     GTEST_SKIP() << "LeakChecker is not active";
   }
   auto foo = absl::IgnoreLeak(new std::string("some ignored leaked string"));
-  ABSL_RAW_LOG(INFO, "Ignoring leaked string %s", foo->c_str());
+  LOG(INFO) << "Ignoring leaked string " << foo;
 }
 
 TEST(LeakCheckTest, LeakCheckDisablerIgnoresLeak) {
@@ -35,7 +35,7 @@ TEST(LeakCheckTest, LeakCheckDisablerIgnoresLeak) {
   }
   absl::LeakCheckDisabler disabler;
   auto foo = new std::string("some string leaked while checks are disabled");
-  ABSL_RAW_LOG(INFO, "Ignoring leaked string %s", foo->c_str());
+  LOG(INFO) << "Ignoring leaked string " << foo;
 }
 
 }  // namespace
diff --git a/absl/debugging/stacktrace_test.cc b/absl/debugging/stacktrace_test.cc
index 78ce7ad0..31f7723c 100644
--- a/absl/debugging/stacktrace_test.cc
+++ b/absl/debugging/stacktrace_test.cc
@@ -20,8 +20,8 @@
 
 namespace {
 
-// This test is currently only known to pass on linux/x86_64.
-#if defined(__linux__) && defined(__x86_64__)
+// This test is currently only known to pass on Linux x86_64/aarch64.
+#if defined(__linux__) && (defined(__x86_64__) || defined(__aarch64__))
 ABSL_ATTRIBUTE_NOINLINE void Unwind(void* p) {
   ABSL_ATTRIBUTE_UNUSED static void* volatile sink = p;
   constexpr int kSize = 16;
diff --git a/absl/debugging/symbolize_elf.inc b/absl/debugging/symbolize_elf.inc
index ffb4eecf..30638cb2 100644
--- a/absl/debugging/symbolize_elf.inc
+++ b/absl/debugging/symbolize_elf.inc
@@ -532,6 +532,11 @@ bool ForEachSection(int fd,
     return false;
   }
 
+  // Technically it can be larger, but in practice this never happens.
+  if (elf_header.e_shentsize != sizeof(ElfW(Shdr))) {
+    return false;
+  }
+
   ElfW(Shdr) shstrtab;
   off_t shstrtab_offset = static_cast<off_t>(elf_header.e_shoff) +
                           elf_header.e_shentsize * elf_header.e_shstrndx;
@@ -584,6 +589,11 @@ bool GetSectionHeaderByName(int fd, const char *name, size_t name_len,
     return false;
   }
 
+  // Technically it can be larger, but in practice this never happens.
+  if (elf_header.e_shentsize != sizeof(ElfW(Shdr))) {
+    return false;
+  }
+
   ElfW(Shdr) shstrtab;
   off_t shstrtab_offset = static_cast<off_t>(elf_header.e_shoff) +
                           elf_header.e_shentsize * elf_header.e_shstrndx;
@@ -648,8 +658,10 @@ static bool ShouldPickFirstSymbol(const ElfW(Sym) & symbol1,
 }
 
 // Return true if an address is inside a section.
-static bool InSection(const void *address, const ElfW(Shdr) * section) {
-  const char *start = reinterpret_cast<const char *>(section->sh_addr);
+static bool InSection(const void *address, ptrdiff_t relocation,
+                      const ElfW(Shdr) * section) {
+  const char *start = reinterpret_cast<const char *>(
+      section->sh_addr + static_cast<ElfW(Addr)>(relocation));
   size_t size = static_cast<size_t>(section->sh_size);
   return start <= address && address < (start + size);
 }
@@ -689,8 +701,8 @@ static ABSL_ATTRIBUTE_NOINLINE FindSymbolResult FindSymbol(
   // starting address.  However, we do not always want to use the real
   // starting address because we sometimes want to symbolize a function
   // pointer into the .opd section, e.g. FindSymbol(&foo,...).
-  const bool pc_in_opd =
-      kPlatformUsesOPDSections && opd != nullptr && InSection(pc, opd);
+  const bool pc_in_opd = kPlatformUsesOPDSections && opd != nullptr &&
+                         InSection(pc, relocation, opd);
   const bool deref_function_descriptor_pointer =
       kPlatformUsesOPDSections && opd != nullptr && !pc_in_opd;
 
@@ -730,7 +742,7 @@ static ABSL_ATTRIBUTE_NOINLINE FindSymbolResult FindSymbol(
 #endif
 
       if (deref_function_descriptor_pointer &&
-          InSection(original_start_address, opd)) {
+          InSection(original_start_address, /*relocation=*/0, opd)) {
         // The opd section is mapped into memory.  Just dereference
         // start_address to get the first double word, which points to the
         // function entry.
@@ -1326,7 +1338,7 @@ static bool MaybeInitializeObjFile(ObjFile *obj) {
     const int phnum = obj->elf_header.e_phnum;
     const int phentsize = obj->elf_header.e_phentsize;
     auto phoff = static_cast<off_t>(obj->elf_header.e_phoff);
-    size_t num_executable_load_segments = 0;
+    size_t num_interesting_load_segments = 0;
     for (int j = 0; j < phnum; j++) {
       ElfW(Phdr) phdr;
       if (!ReadFromOffsetExact(obj->fd, &phdr, sizeof(phdr), phoff)) {
@@ -1335,23 +1347,35 @@ static bool MaybeInitializeObjFile(ObjFile *obj) {
         return false;
       }
       phoff += phentsize;
-      constexpr int rx = PF_X | PF_R;
-      if (phdr.p_type != PT_LOAD || (phdr.p_flags & rx) != rx) {
-        // Not a LOAD segment, or not executable code.
+
+#if defined(__powerpc__) && !(_CALL_ELF > 1)
+      // On the PowerPC ELF v1 ABI, function pointers actually point to function
+      // descriptors. These descriptors are stored in an .opd section, which is
+      // mapped read-only. We thus need to look at all readable segments, not
+      // just the executable ones.
+      constexpr int interesting = PF_R;
+#else
+      constexpr int interesting = PF_X | PF_R;
+#endif
+
+      if (phdr.p_type != PT_LOAD
+          || (phdr.p_flags & interesting) != interesting) {
+        // Not a LOAD segment, not executable code, and not a function
+        // descriptor.
         continue;
       }
-      if (num_executable_load_segments < obj->phdr.size()) {
-        memcpy(&obj->phdr[num_executable_load_segments++], &phdr, sizeof(phdr));
+      if (num_interesting_load_segments < obj->phdr.size()) {
+        memcpy(&obj->phdr[num_interesting_load_segments++], &phdr, sizeof(phdr));
       } else {
         ABSL_RAW_LOG(
-            WARNING, "%s: too many executable LOAD segments: %zu >= %zu",
-            obj->filename, num_executable_load_segments, obj->phdr.size());
+            WARNING, "%s: too many interesting LOAD segments: %zu >= %zu",
+            obj->filename, num_interesting_load_segments, obj->phdr.size());
         break;
       }
     }
-    if (num_executable_load_segments == 0) {
-      // This object has no "r-x" LOAD segments. That's unexpected.
-      ABSL_RAW_LOG(WARNING, "%s: no executable LOAD segments", obj->filename);
+    if (num_interesting_load_segments == 0) {
+      // This object has no interesting LOAD segments. That's unexpected.
+      ABSL_RAW_LOG(WARNING, "%s: no interesting LOAD segments", obj->filename);
       return false;
     }
   }
@@ -1379,8 +1403,8 @@ const char *Symbolizer::GetUncachedSymbol(const void *pc) {
         // X in the file will have a start address of [true relocation]+X.
         relocation = static_cast<ptrdiff_t>(start_addr - obj->offset);
 
-        // Note: some binaries have multiple "rx" LOAD segments. We must
-        // find the right one.
+        // Note: some binaries have multiple LOAD segments that can contain
+        // function pointers. We must find the right one.
         ElfW(Phdr) *phdr = nullptr;
         for (size_t j = 0; j < obj->phdr.size(); j++) {
           ElfW(Phdr) &p = obj->phdr[j];
@@ -1390,7 +1414,7 @@ const char *Symbolizer::GetUncachedSymbol(const void *pc) {
             ABSL_RAW_CHECK(p.p_type == PT_NULL, "unexpected p_type");
             break;
           }
-          if (pc < reinterpret_cast<void *>(start_addr + p.p_memsz)) {
+          if (pc < reinterpret_cast<void *>(start_addr + p.p_vaddr + p.p_memsz)) {
             phdr = &p;
             break;
           }
diff --git a/absl/debugging/symbolize_emscripten.inc b/absl/debugging/symbolize_emscripten.inc
index c226c456..a0f344dd 100644
--- a/absl/debugging/symbolize_emscripten.inc
+++ b/absl/debugging/symbolize_emscripten.inc
@@ -50,6 +50,9 @@ bool Symbolize(const void* pc, char* out, int out_size) {
   if (!HaveOffsetConverter()) {
     return false;
   }
+  if (pc == nullptr || out_size <= 0) {
+    return false;
+  }
   const char* func_name = emscripten_pc_get_function(pc);
   if (func_name == nullptr) {
     return false;
diff --git a/absl/debugging/symbolize_test.cc b/absl/debugging/symbolize_test.cc
index 3165c6ed..d0feab2f 100644
--- a/absl/debugging/symbolize_test.cc
+++ b/absl/debugging/symbolize_test.cc
@@ -14,6 +14,10 @@
 
 #include "absl/debugging/symbolize.h"
 
+#ifdef __EMSCRIPTEN__
+#include <emscripten.h>
+#endif
+
 #ifndef _WIN32
 #include <fcntl.h>
 #include <sys/mman.h>
@@ -29,12 +33,17 @@
 #include "absl/base/casts.h"
 #include "absl/base/config.h"
 #include "absl/base/internal/per_thread_tls.h"
-#include "absl/base/internal/raw_logging.h"
 #include "absl/base/optimization.h"
 #include "absl/debugging/internal/stack_consumption.h"
+#include "absl/log/check.h"
+#include "absl/log/log.h"
 #include "absl/memory/memory.h"
 #include "absl/strings/string_view.h"
 
+#if defined(MAP_ANON) && !defined(MAP_ANONYMOUS)
+#define MAP_ANONYMOUS MAP_ANON
+#endif
+
 using testing::Contains;
 
 #ifdef _WIN32
@@ -81,21 +90,13 @@ int ABSL_ATTRIBUTE_SECTION_VARIABLE(.text.unlikely) unlikely_func() {
   return 0;
 }
 
-int ABSL_ATTRIBUTE_SECTION_VARIABLE(.text.hot) hot_func() {
-  return 0;
-}
+int ABSL_ATTRIBUTE_SECTION_VARIABLE(.text.hot) hot_func() { return 0; }
 
-int ABSL_ATTRIBUTE_SECTION_VARIABLE(.text.startup) startup_func() {
-  return 0;
-}
+int ABSL_ATTRIBUTE_SECTION_VARIABLE(.text.startup) startup_func() { return 0; }
 
-int ABSL_ATTRIBUTE_SECTION_VARIABLE(.text.exit) exit_func() {
-  return 0;
-}
+int ABSL_ATTRIBUTE_SECTION_VARIABLE(.text.exit) exit_func() { return 0; }
 
-int /*ABSL_ATTRIBUTE_SECTION_VARIABLE(.text)*/ regular_func() {
-  return 0;
-}
+int /*ABSL_ATTRIBUTE_SECTION_VARIABLE(.text)*/ regular_func() { return 0; }
 
 // Thread-local data may confuse the symbolizer, ensure that it does not.
 // Variable sizes and order are important.
@@ -106,6 +107,8 @@ static ABSL_PER_THREAD_TLS_KEYWORD char
 #endif
 
 #if !defined(__EMSCRIPTEN__)
+static void *GetPCFromFnPtr(void *ptr) { return ptr; }
+
 // Used below to hopefully inhibit some compiler/linker optimizations
 // that may remove kHpageTextPadding, kPadding0, and kPadding1 from
 // the binary.
@@ -114,7 +117,14 @@ static volatile bool volatile_bool = false;
 // Force the binary to be large enough that a THP .text remap will succeed.
 static constexpr size_t kHpageSize = 1 << 21;
 const char kHpageTextPadding[kHpageSize * 4] ABSL_ATTRIBUTE_SECTION_VARIABLE(
-    .text) = "";
+        .text) = "";
+
+#else
+static void *GetPCFromFnPtr(void *ptr) {
+  return EM_ASM_PTR(
+      { return wasmOffsetConverter.convert(wasmTable.get($0).name, 0); }, ptr);
+}
+
 #endif  // !defined(__EMSCRIPTEN__)
 
 static char try_symbolize_buffer[4096];
@@ -124,15 +134,17 @@ static char try_symbolize_buffer[4096];
 // absl::Symbolize() returns false, otherwise returns try_symbolize_buffer with
 // the result of absl::Symbolize().
 static const char *TrySymbolizeWithLimit(void *pc, int limit) {
-  ABSL_RAW_CHECK(limit <= sizeof(try_symbolize_buffer),
-                 "try_symbolize_buffer is too small");
+  CHECK_LE(limit, sizeof(try_symbolize_buffer))
+      << "try_symbolize_buffer is too small";
 
   // Use the heap to facilitate heap and buffer sanitizer tools.
   auto heap_buffer = absl::make_unique<char[]>(sizeof(try_symbolize_buffer));
   bool found = absl::Symbolize(pc, heap_buffer.get(), limit);
   if (found) {
-    ABSL_RAW_CHECK(strnlen(heap_buffer.get(), limit) < limit,
-                   "absl::Symbolize() did not properly terminate the string");
+    CHECK_LT(static_cast<int>(
+                 strnlen(heap_buffer.get(), static_cast<size_t>(limit))),
+             limit)
+        << "absl::Symbolize() did not properly terminate the string";
     strncpy(try_symbolize_buffer, heap_buffer.get(),
             sizeof(try_symbolize_buffer) - 1);
     try_symbolize_buffer[sizeof(try_symbolize_buffer) - 1] = '\0';
@@ -155,21 +167,20 @@ void ABSL_ATTRIBUTE_NOINLINE TestWithReturnAddress() {
 #if defined(ABSL_HAVE_ATTRIBUTE_NOINLINE)
   void *return_address = __builtin_return_address(0);
   const char *symbol = TrySymbolize(return_address);
-  ABSL_RAW_CHECK(symbol != nullptr, "TestWithReturnAddress failed");
-  ABSL_RAW_CHECK(strcmp(symbol, "main") == 0, "TestWithReturnAddress failed");
+  CHECK_NE(symbol, nullptr) << "TestWithReturnAddress failed";
+  CHECK_STREQ(symbol, "main") << "TestWithReturnAddress failed";
   std::cout << "TestWithReturnAddress passed" << std::endl;
 #endif
 }
 
-#ifndef ABSL_INTERNAL_HAVE_EMSCRIPTEN_SYMBOLIZE
-
 TEST(Symbolize, Cached) {
   // Compilers should give us pointers to them.
-  EXPECT_STREQ("nonstatic_func", TrySymbolize((void *)(&nonstatic_func)));
-
+  EXPECT_STREQ("nonstatic_func",
+               TrySymbolize(GetPCFromFnPtr((void *)(&nonstatic_func))));
   // The name of an internal linkage symbol is not specified; allow either a
   // mangled or an unmangled name here.
-  const char *static_func_symbol = TrySymbolize((void *)(&static_func));
+  const char *static_func_symbol =
+      TrySymbolize(GetPCFromFnPtr((void *)(&static_func)));
   EXPECT_TRUE(strcmp("static_func", static_func_symbol) == 0 ||
               strcmp("static_func()", static_func_symbol) == 0);
 
@@ -179,33 +190,50 @@ TEST(Symbolize, Cached) {
 TEST(Symbolize, Truncation) {
   constexpr char kNonStaticFunc[] = "nonstatic_func";
   EXPECT_STREQ("nonstatic_func",
-               TrySymbolizeWithLimit((void *)(&nonstatic_func),
+               TrySymbolizeWithLimit(GetPCFromFnPtr((void *)(&nonstatic_func)),
                                      strlen(kNonStaticFunc) + 1));
   EXPECT_STREQ("nonstatic_...",
-               TrySymbolizeWithLimit((void *)(&nonstatic_func),
+               TrySymbolizeWithLimit(GetPCFromFnPtr((void *)(&nonstatic_func)),
                                      strlen(kNonStaticFunc) + 0));
   EXPECT_STREQ("nonstatic...",
-               TrySymbolizeWithLimit((void *)(&nonstatic_func),
+               TrySymbolizeWithLimit(GetPCFromFnPtr((void *)(&nonstatic_func)),
                                      strlen(kNonStaticFunc) - 1));
-  EXPECT_STREQ("n...", TrySymbolizeWithLimit((void *)(&nonstatic_func), 5));
-  EXPECT_STREQ("...", TrySymbolizeWithLimit((void *)(&nonstatic_func), 4));
-  EXPECT_STREQ("..", TrySymbolizeWithLimit((void *)(&nonstatic_func), 3));
-  EXPECT_STREQ(".", TrySymbolizeWithLimit((void *)(&nonstatic_func), 2));
-  EXPECT_STREQ("", TrySymbolizeWithLimit((void *)(&nonstatic_func), 1));
-  EXPECT_EQ(nullptr, TrySymbolizeWithLimit((void *)(&nonstatic_func), 0));
+  EXPECT_STREQ("n...", TrySymbolizeWithLimit(
+                           GetPCFromFnPtr((void *)(&nonstatic_func)), 5));
+  EXPECT_STREQ("...", TrySymbolizeWithLimit(
+                          GetPCFromFnPtr((void *)(&nonstatic_func)), 4));
+  EXPECT_STREQ("..", TrySymbolizeWithLimit(
+                         GetPCFromFnPtr((void *)(&nonstatic_func)), 3));
+  EXPECT_STREQ(
+      ".", TrySymbolizeWithLimit(GetPCFromFnPtr((void *)(&nonstatic_func)), 2));
+  EXPECT_STREQ(
+      "", TrySymbolizeWithLimit(GetPCFromFnPtr((void *)(&nonstatic_func)), 1));
+  EXPECT_EQ(nullptr, TrySymbolizeWithLimit(
+                         GetPCFromFnPtr((void *)(&nonstatic_func)), 0));
 }
 
 TEST(Symbolize, SymbolizeWithDemangling) {
   Foo::func(100);
-  EXPECT_STREQ("Foo::func()", TrySymbolize((void *)(&Foo::func)));
+#ifdef __EMSCRIPTEN__
+  // Emscripten's online symbolizer is more precise with arguments.
+  EXPECT_STREQ("Foo::func(int)",
+               TrySymbolize(GetPCFromFnPtr((void *)(&Foo::func))));
+#else
+  EXPECT_STREQ("Foo::func()",
+               TrySymbolize(GetPCFromFnPtr((void *)(&Foo::func))));
+#endif
 }
 
 TEST(Symbolize, SymbolizeSplitTextSections) {
-  EXPECT_STREQ("unlikely_func()", TrySymbolize((void *)(&unlikely_func)));
-  EXPECT_STREQ("hot_func()", TrySymbolize((void *)(&hot_func)));
-  EXPECT_STREQ("startup_func()", TrySymbolize((void *)(&startup_func)));
-  EXPECT_STREQ("exit_func()", TrySymbolize((void *)(&exit_func)));
-  EXPECT_STREQ("regular_func()", TrySymbolize((void *)(&regular_func)));
+  EXPECT_STREQ("unlikely_func()",
+               TrySymbolize(GetPCFromFnPtr((void *)(&unlikely_func))));
+  EXPECT_STREQ("hot_func()", TrySymbolize(GetPCFromFnPtr((void *)(&hot_func))));
+  EXPECT_STREQ("startup_func()",
+               TrySymbolize(GetPCFromFnPtr((void *)(&startup_func))));
+  EXPECT_STREQ("exit_func()",
+               TrySymbolize(GetPCFromFnPtr((void *)(&exit_func))));
+  EXPECT_STREQ("regular_func()",
+               TrySymbolize(GetPCFromFnPtr((void *)(&regular_func))));
 }
 
 // Tests that verify that Symbolize stack footprint is within some limit.
@@ -275,15 +303,14 @@ TEST(Symbolize, SymbolizeWithDemanglingStackConsumption) {
 
 #endif  // ABSL_INTERNAL_HAVE_DEBUGGING_STACK_CONSUMPTION
 
-#ifndef ABSL_INTERNAL_HAVE_DARWIN_SYMBOLIZE
+#if !defined(ABSL_INTERNAL_HAVE_DARWIN_SYMBOLIZE) && \
+    !defined(ABSL_INTERNAL_HAVE_EMSCRIPTEN_SYMBOLIZE)
 // Use a 64K page size for PPC.
 const size_t kPageSize = 64 << 10;
 // We place a read-only symbols into the .text section and verify that we can
 // symbolize them and other symbols after remapping them.
-const char kPadding0[kPageSize * 4] ABSL_ATTRIBUTE_SECTION_VARIABLE(.text) =
-    "";
-const char kPadding1[kPageSize * 4] ABSL_ATTRIBUTE_SECTION_VARIABLE(.text) =
-    "";
+const char kPadding0[kPageSize * 4] ABSL_ATTRIBUTE_SECTION_VARIABLE(.text) = "";
+const char kPadding1[kPageSize * 4] ABSL_ATTRIBUTE_SECTION_VARIABLE(.text) = "";
 
 static int FilterElfHeader(struct dl_phdr_info *info, size_t size, void *data) {
   for (int i = 0; i < info->dlpi_phnum; i++) {
@@ -314,8 +341,8 @@ static int FilterElfHeader(struct dl_phdr_info *info, size_t size, void *data) {
 TEST(Symbolize, SymbolizeWithMultipleMaps) {
   // Force kPadding0 and kPadding1 to be linked in.
   if (volatile_bool) {
-    ABSL_RAW_LOG(INFO, "%s", kPadding0);
-    ABSL_RAW_LOG(INFO, "%s", kPadding1);
+    LOG(INFO) << kPadding0;
+    LOG(INFO) << kPadding1;
   }
 
   // Verify we can symbolize everything.
@@ -433,17 +460,17 @@ TEST(Symbolize, ForEachSection) {
 
   close(fd);
 }
-#endif  // !ABSL_INTERNAL_HAVE_DARWIN_SYMBOLIZE
-#endif  // !ABSL_INTERNAL_HAVE_EMSCRIPTEN_SYMBOLIZE
+#endif  // !ABSL_INTERNAL_HAVE_DARWIN_SYMBOLIZE &&
+        // !ABSL_INTERNAL_HAVE_EMSCRIPTEN_SYMBOLIZE
 
 // x86 specific tests.  Uses some inline assembler.
 extern "C" {
 inline void *ABSL_ATTRIBUTE_ALWAYS_INLINE inline_func() {
   void *pc = nullptr;
 #if defined(__i386__)
-  __asm__ __volatile__("call 1f;\n 1: pop %[PC]" : [ PC ] "=r"(pc));
+  __asm__ __volatile__("call 1f;\n 1: pop %[PC]" : [PC] "=r"(pc));
 #elif defined(__x86_64__)
-  __asm__ __volatile__("leaq 0(%%rip),%[PC];\n" : [ PC ] "=r"(pc));
+  __asm__ __volatile__("leaq 0(%%rip),%[PC];\n" : [PC] "=r"(pc));
 #endif
   return pc;
 }
@@ -451,9 +478,9 @@ inline void *ABSL_ATTRIBUTE_ALWAYS_INLINE inline_func() {
 void *ABSL_ATTRIBUTE_NOINLINE non_inline_func() {
   void *pc = nullptr;
 #if defined(__i386__)
-  __asm__ __volatile__("call 1f;\n 1: pop %[PC]" : [ PC ] "=r"(pc));
+  __asm__ __volatile__("call 1f;\n 1: pop %[PC]" : [PC] "=r"(pc));
 #elif defined(__x86_64__)
-  __asm__ __volatile__("leaq 0(%%rip),%[PC];\n" : [ PC ] "=r"(pc));
+  __asm__ __volatile__("leaq 0(%%rip),%[PC];\n" : [PC] "=r"(pc));
 #endif
   return pc;
 }
@@ -463,9 +490,9 @@ void ABSL_ATTRIBUTE_NOINLINE TestWithPCInsideNonInlineFunction() {
     (defined(__i386__) || defined(__x86_64__))
   void *pc = non_inline_func();
   const char *symbol = TrySymbolize(pc);
-  ABSL_RAW_CHECK(symbol != nullptr, "TestWithPCInsideNonInlineFunction failed");
-  ABSL_RAW_CHECK(strcmp(symbol, "non_inline_func") == 0,
-                 "TestWithPCInsideNonInlineFunction failed");
+  CHECK_NE(symbol, nullptr) << "TestWithPCInsideNonInlineFunction failed";
+  CHECK_STREQ(symbol, "non_inline_func")
+      << "TestWithPCInsideNonInlineFunction failed";
   std::cout << "TestWithPCInsideNonInlineFunction passed" << std::endl;
 #endif
 }
@@ -475,9 +502,8 @@ void ABSL_ATTRIBUTE_NOINLINE TestWithPCInsideInlineFunction() {
     (defined(__i386__) || defined(__x86_64__))
   void *pc = inline_func();  // Must be inlined.
   const char *symbol = TrySymbolize(pc);
-  ABSL_RAW_CHECK(symbol != nullptr, "TestWithPCInsideInlineFunction failed");
-  ABSL_RAW_CHECK(strcmp(symbol, __FUNCTION__) == 0,
-                 "TestWithPCInsideInlineFunction failed");
+  CHECK_NE(symbol, nullptr) << "TestWithPCInsideInlineFunction failed";
+  CHECK_STREQ(symbol, __FUNCTION__) << "TestWithPCInsideInlineFunction failed";
   std::cout << "TestWithPCInsideInlineFunction passed" << std::endl;
 #endif
 }
@@ -519,9 +545,8 @@ __attribute__((target("arm"))) int ArmThumbOverlapArm(int x) {
 void ABSL_ATTRIBUTE_NOINLINE TestArmThumbOverlap() {
 #if defined(ABSL_HAVE_ATTRIBUTE_NOINLINE)
   const char *symbol = TrySymbolize((void *)&ArmThumbOverlapArm);
-  ABSL_RAW_CHECK(symbol != nullptr, "TestArmThumbOverlap failed");
-  ABSL_RAW_CHECK(strcmp("ArmThumbOverlapArm()", symbol) == 0,
-                 "TestArmThumbOverlap failed");
+  CHECK_NE(symbol, nullptr) << "TestArmThumbOverlap failed";
+  CHECK_STREQ("ArmThumbOverlapArm()", symbol) << "TestArmThumbOverlap failed";
   std::cout << "TestArmThumbOverlap passed" << std::endl;
 #endif
 }
@@ -570,7 +595,7 @@ TEST(Symbolize, SymbolizeWithDemangling) {
 }
 
 #endif  // !defined(ABSL_CONSUME_DLL)
-#else  // Symbolizer unimplemented
+#else   // Symbolizer unimplemented
 TEST(Symbolize, Unimplemented) {
   char buf[64];
   EXPECT_FALSE(absl::Symbolize((void *)(&nonstatic_func), buf, sizeof(buf)));
@@ -584,7 +609,7 @@ int main(int argc, char **argv) {
 #if !defined(__EMSCRIPTEN__)
   // Make sure kHpageTextPadding is linked into the binary.
   if (volatile_bool) {
-    ABSL_RAW_LOG(INFO, "%s", kHpageTextPadding);
+    LOG(INFO) << kHpageTextPadding;
   }
 #endif  // !defined(__EMSCRIPTEN__)
 
@@ -597,7 +622,8 @@ int main(int argc, char **argv) {
   absl::InitializeSymbolizer(argv[0]);
   testing::InitGoogleTest(&argc, argv);
 
-#if defined(ABSL_INTERNAL_HAVE_ELF_SYMBOLIZE) || \
+#if defined(ABSL_INTERNAL_HAVE_ELF_SYMBOLIZE) ||        \
+    defined(ABSL_INTERNAL_HAVE_EMSCRIPTEN_SYMBOLIZE) || \
     defined(ABSL_INTERNAL_HAVE_DARWIN_SYMBOLIZE)
   TestWithPCInsideInlineFunction();
   TestWithPCInsideNonInlineFunction();
diff --git a/absl/flags/BUILD.bazel b/absl/flags/BUILD.bazel
index f5b3e033..50bf387c 100644
--- a/absl/flags/BUILD.bazel
+++ b/absl/flags/BUILD.bazel
@@ -99,6 +99,7 @@ cc_library(
         "//absl/base:config",
         "//absl/base:core_headers",
         "//absl/base:log_severity",
+        "//absl/numeric:int128",
         "//absl/strings",
         "//absl/strings:str_format",
         "//absl/types:optional",
@@ -284,6 +285,7 @@ cc_library(
         ":usage_internal",
         "//absl/base:config",
         "//absl/base:core_headers",
+        "//absl/base:raw_logging_internal",
         "//absl/strings",
         "//absl/synchronization",
     ],
@@ -386,6 +388,7 @@ cc_test(
         ":reflection",
         "//absl/base:core_headers",
         "//absl/base:malloc_internal",
+        "//absl/numeric:int128",
         "//absl/strings",
         "//absl/time",
         "@com_google_googletest//:gtest_main",
@@ -451,8 +454,8 @@ cc_test(
         ":parse",
         ":reflection",
         ":usage_internal",
-        "//absl/base:raw_logging_internal",
         "//absl/base:scoped_set_env",
+        "//absl/log",
         "//absl/strings",
         "//absl/types:span",
         "@com_google_googletest//:gtest_main",
diff --git a/absl/flags/CMakeLists.txt b/absl/flags/CMakeLists.txt
index 2f234aa4..b20463f5 100644
--- a/absl/flags/CMakeLists.txt
+++ b/absl/flags/CMakeLists.txt
@@ -87,6 +87,7 @@ absl_cc_library(
     absl::config
     absl::core_headers
     absl::log_severity
+    absl::int128
     absl::optional
     absl::strings
     absl::str_format
@@ -262,6 +263,7 @@ absl_cc_library(
     absl::config
     absl::core_headers
     absl::flags_usage_internal
+    absl::raw_logging_internal
     absl::strings
     absl::synchronization
 )
@@ -296,7 +298,7 @@ absl_cc_library(
 )
 
 ############################################################################
-# Unit tests in alpahabetical order.
+# Unit tests in alphabetical order.
 
 absl_cc_test(
   NAME
@@ -344,6 +346,7 @@ absl_cc_test(
     absl::flags_internal
     absl::flags_marshalling
     absl::flags_reflection
+    absl::int128
     absl::strings
     absl::time
     GTest::gtest_main
@@ -373,7 +376,7 @@ absl_cc_test(
     absl::flags_parse
     absl::flags_reflection
     absl::flags_usage_internal
-    absl::raw_logging_internal
+    absl::log
     absl::scoped_set_env
     absl::span
     absl::strings
diff --git a/absl/flags/commandlineflag.h b/absl/flags/commandlineflag.h
index f2fa0897..c30aa609 100644
--- a/absl/flags/commandlineflag.h
+++ b/absl/flags/commandlineflag.h
@@ -186,7 +186,7 @@ class CommandLineFlag {
   // command line.
   virtual bool IsSpecifiedOnCommandLine() const = 0;
 
-  // Validates supplied value usign validator or parseflag routine
+  // Validates supplied value using validator or parseflag routine
   virtual bool ValidateInputValue(absl::string_view value) const = 0;
 
   // Checks that flags default value can be converted to string and back to the
diff --git a/absl/flags/flag_test.cc b/absl/flags/flag_test.cc
index 845b4eba..f9cda02e 100644
--- a/absl/flags/flag_test.cc
+++ b/absl/flags/flag_test.cc
@@ -34,6 +34,7 @@
 #include "absl/flags/marshalling.h"
 #include "absl/flags/reflection.h"
 #include "absl/flags/usage_config.h"
+#include "absl/numeric/int128.h"
 #include "absl/strings/match.h"
 #include "absl/strings/numbers.h"
 #include "absl/strings/str_cat.h"
@@ -127,6 +128,11 @@ TEST_F(FlagTest, Traits) {
             flags::FlagValueStorageKind::kAlignedBuffer);
   EXPECT_EQ(flags::StorageKind<std::vector<std::string>>(),
             flags::FlagValueStorageKind::kAlignedBuffer);
+
+  EXPECT_EQ(flags::StorageKind<absl::int128>(),
+            flags::FlagValueStorageKind::kSequenceLocked);
+  EXPECT_EQ(flags::StorageKind<absl::uint128>(),
+            flags::FlagValueStorageKind::kSequenceLocked);
 }
 
 // --------------------------------------------------------------------
@@ -135,6 +141,8 @@ constexpr flags::FlagHelpArg help_arg{flags::FlagHelpMsg("literal help"),
                                       flags::FlagHelpKind::kLiteral};
 
 using String = std::string;
+using int128 = absl::int128;
+using uint128 = absl::uint128;
 
 #if !defined(_MSC_VER) || defined(__clang__)
 #define DEFINE_CONSTRUCTED_FLAG(T, dflt, dflt_kind)                        \
@@ -171,6 +179,8 @@ DEFINE_CONSTRUCTED_FLAG(float, 7.8, kOneWord);
 DEFINE_CONSTRUCTED_FLAG(double, 9.10, kOneWord);
 DEFINE_CONSTRUCTED_FLAG(String, &TestMakeDflt<String>, kGenFunc);
 DEFINE_CONSTRUCTED_FLAG(UDT, &TestMakeDflt<UDT>, kGenFunc);
+DEFINE_CONSTRUCTED_FLAG(int128, 13, kGenFunc);
+DEFINE_CONSTRUCTED_FLAG(uint128, 14, kGenFunc);
 
 template <typename T>
 bool TestConstructionFor(const absl::Flag<T>& f1, absl::Flag<T>& f2) {
@@ -202,6 +212,8 @@ TEST_F(FlagTest, TestConstruction) {
   TEST_CONSTRUCTED_FLAG(double);
   TEST_CONSTRUCTED_FLAG(String);
   TEST_CONSTRUCTED_FLAG(UDT);
+  TEST_CONSTRUCTED_FLAG(int128);
+  TEST_CONSTRUCTED_FLAG(uint128);
 }
 
 // --------------------------------------------------------------------
@@ -220,6 +232,8 @@ ABSL_DECLARE_FLAG(double, test_flag_09);
 ABSL_DECLARE_FLAG(float, test_flag_10);
 ABSL_DECLARE_FLAG(std::string, test_flag_11);
 ABSL_DECLARE_FLAG(absl::Duration, test_flag_12);
+ABSL_DECLARE_FLAG(absl::int128, test_flag_13);
+ABSL_DECLARE_FLAG(absl::uint128, test_flag_14);
 
 namespace {
 
@@ -251,6 +265,10 @@ TEST_F(FlagTest, TestFlagDeclaration) {
             "test_flag_11");
   EXPECT_EQ(absl::GetFlagReflectionHandle(FLAGS_test_flag_12).Name(),
             "test_flag_12");
+  EXPECT_EQ(absl::GetFlagReflectionHandle(FLAGS_test_flag_13).Name(),
+            "test_flag_13");
+  EXPECT_EQ(absl::GetFlagReflectionHandle(FLAGS_test_flag_14).Name(),
+            "test_flag_14");
 }
 #endif  // !ABSL_FLAGS_STRIP_NAMES
 
@@ -270,6 +288,9 @@ ABSL_FLAG(double, test_flag_09, -9.876e-50, "test flag 09");
 ABSL_FLAG(float, test_flag_10, 1.234e12f, "test flag 10");
 ABSL_FLAG(std::string, test_flag_11, "", "test flag 11");
 ABSL_FLAG(absl::Duration, test_flag_12, absl::Minutes(10), "test flag 12");
+ABSL_FLAG(absl::int128, test_flag_13, absl::MakeInt128(-1, 0), "test flag 13");
+ABSL_FLAG(absl::uint128, test_flag_14, absl::MakeUint128(0, 0xFFFAAABBBCCCDDD),
+          "test flag 14");
 
 namespace {
 
@@ -384,6 +405,24 @@ TEST_F(FlagTest, TestFlagDefinition) {
       absl::GetFlagReflectionHandle(FLAGS_test_flag_12).Filename(),
       expected_file_name))
       << absl::GetFlagReflectionHandle(FLAGS_test_flag_12).Filename();
+
+  EXPECT_EQ(absl::GetFlagReflectionHandle(FLAGS_test_flag_13).Name(),
+            "test_flag_13");
+  EXPECT_EQ(absl::GetFlagReflectionHandle(FLAGS_test_flag_13).Help(),
+            "test flag 13");
+  EXPECT_TRUE(absl::EndsWith(
+      absl::GetFlagReflectionHandle(FLAGS_test_flag_13).Filename(),
+      expected_file_name))
+      << absl::GetFlagReflectionHandle(FLAGS_test_flag_13).Filename();
+
+  EXPECT_EQ(absl::GetFlagReflectionHandle(FLAGS_test_flag_14).Name(),
+            "test_flag_14");
+  EXPECT_EQ(absl::GetFlagReflectionHandle(FLAGS_test_flag_14).Help(),
+            "test flag 14");
+  EXPECT_TRUE(absl::EndsWith(
+      absl::GetFlagReflectionHandle(FLAGS_test_flag_14).Filename(),
+      expected_file_name))
+      << absl::GetFlagReflectionHandle(FLAGS_test_flag_14).Filename();
 }
 #endif  // !ABSL_FLAGS_STRIP_NAMES
 
@@ -414,6 +453,10 @@ TEST_F(FlagTest, TestDefault) {
             "");
   EXPECT_EQ(absl::GetFlagReflectionHandle(FLAGS_test_flag_12).DefaultValue(),
             "10m");
+  EXPECT_EQ(absl::GetFlagReflectionHandle(FLAGS_test_flag_13).DefaultValue(),
+            "-18446744073709551616");
+  EXPECT_EQ(absl::GetFlagReflectionHandle(FLAGS_test_flag_14).DefaultValue(),
+            "1152827684197027293");
 
   EXPECT_EQ(absl::GetFlagReflectionHandle(FLAGS_test_flag_01).CurrentValue(),
             "true");
@@ -439,6 +482,10 @@ TEST_F(FlagTest, TestDefault) {
             "");
   EXPECT_EQ(absl::GetFlagReflectionHandle(FLAGS_test_flag_12).CurrentValue(),
             "10m");
+  EXPECT_EQ(absl::GetFlagReflectionHandle(FLAGS_test_flag_13).CurrentValue(),
+            "-18446744073709551616");
+  EXPECT_EQ(absl::GetFlagReflectionHandle(FLAGS_test_flag_14).CurrentValue(),
+            "1152827684197027293");
 
   EXPECT_EQ(absl::GetFlag(FLAGS_test_flag_01), true);
   EXPECT_EQ(absl::GetFlag(FLAGS_test_flag_02), 1234);
@@ -452,6 +499,9 @@ TEST_F(FlagTest, TestDefault) {
   EXPECT_NEAR(absl::GetFlag(FLAGS_test_flag_10), 1.234e12f, 1e5f);
   EXPECT_EQ(absl::GetFlag(FLAGS_test_flag_11), "");
   EXPECT_EQ(absl::GetFlag(FLAGS_test_flag_12), absl::Minutes(10));
+  EXPECT_EQ(absl::GetFlag(FLAGS_test_flag_13), absl::MakeInt128(-1, 0));
+  EXPECT_EQ(absl::GetFlag(FLAGS_test_flag_14),
+            absl::MakeUint128(0, 0xFFFAAABBBCCCDDD));
 }
 
 // --------------------------------------------------------------------
@@ -553,6 +603,13 @@ TEST_F(FlagTest, TestGetSet) {
 
   absl::SetFlag(&FLAGS_test_flag_12, absl::Seconds(110));
   EXPECT_EQ(absl::GetFlag(FLAGS_test_flag_12), absl::Seconds(110));
+
+  absl::SetFlag(&FLAGS_test_flag_13, absl::MakeInt128(-1, 0));
+  EXPECT_EQ(absl::GetFlag(FLAGS_test_flag_13), absl::MakeInt128(-1, 0));
+
+  absl::SetFlag(&FLAGS_test_flag_14, absl::MakeUint128(0, 0xFFFAAABBBCCCDDD));
+  EXPECT_EQ(absl::GetFlag(FLAGS_test_flag_14),
+            absl::MakeUint128(0, 0xFFFAAABBBCCCDDD));
 }
 
 // --------------------------------------------------------------------
@@ -582,6 +639,11 @@ TEST_F(FlagTest, TestGetViaReflection) {
   EXPECT_EQ(*handle->TryGet<std::string>(), "");
   handle = absl::FindCommandLineFlag("test_flag_12");
   EXPECT_EQ(*handle->TryGet<absl::Duration>(), absl::Minutes(10));
+  handle = absl::FindCommandLineFlag("test_flag_13");
+  EXPECT_EQ(*handle->TryGet<absl::int128>(), absl::MakeInt128(-1, 0));
+  handle = absl::FindCommandLineFlag("test_flag_14");
+  EXPECT_EQ(*handle->TryGet<absl::uint128>(),
+            absl::MakeUint128(0, 0xFFFAAABBBCCCDDD));
 }
 
 // --------------------------------------------------------------------
@@ -980,7 +1042,7 @@ TEST_F(FlagTest, TesTypeWrappingEnum) {
 
 // This is a compile test to ensure macros are expanded within ABSL_FLAG and
 // ABSL_DECLARE_FLAG.
-#define FLAG_NAME_MACRO(name) prefix_ ## name
+#define FLAG_NAME_MACRO(name) prefix_##name
 ABSL_DECLARE_FLAG(int, FLAG_NAME_MACRO(test_macro_named_flag));
 ABSL_FLAG(int, FLAG_NAME_MACRO(test_macro_named_flag), 0,
           "Testing macro expansion within ABSL_FLAG");
diff --git a/absl/flags/internal/commandlineflag.cc b/absl/flags/internal/commandlineflag.cc
index 4482955c..3c114d10 100644
--- a/absl/flags/internal/commandlineflag.cc
+++ b/absl/flags/internal/commandlineflag.cc
@@ -19,7 +19,7 @@ namespace absl {
 ABSL_NAMESPACE_BEGIN
 namespace flags_internal {
 
-FlagStateInterface::~FlagStateInterface() {}
+FlagStateInterface::~FlagStateInterface() = default;
 
 }  // namespace flags_internal
 ABSL_NAMESPACE_END
diff --git a/absl/flags/internal/flag.cc b/absl/flags/internal/flag.cc
index cc656f9d..65d0e58f 100644
--- a/absl/flags/internal/flag.cc
+++ b/absl/flags/internal/flag.cc
@@ -197,7 +197,7 @@ void FlagImpl::AssertValidType(FlagFastTypeId rhs_type_id,
   FlagFastTypeId lhs_type_id = flags_internal::FastTypeId(op_);
 
   // `rhs_type_id` is the fast type id corresponding to the declaration
-  // visibile at the call site. `lhs_type_id` is the fast type id
+  // visible at the call site. `lhs_type_id` is the fast type id
   // corresponding to the type specified in flag definition. They must match
   //  for this operation to be well-defined.
   if (ABSL_PREDICT_TRUE(lhs_type_id == rhs_type_id)) return;
@@ -238,7 +238,7 @@ void FlagImpl::StoreValue(const void* src) {
   switch (ValueStorageKind()) {
     case FlagValueStorageKind::kValueAndInitBit:
     case FlagValueStorageKind::kOneWordAtomic: {
-      // Load the current value to avoid setting 'init' bit manualy.
+      // Load the current value to avoid setting 'init' bit manually.
       int64_t one_word_val = OneWordValue().load(std::memory_order_acquire);
       std::memcpy(&one_word_val, src, Sizeof(op_));
       OneWordValue().store(one_word_val, std::memory_order_release);
diff --git a/absl/flags/internal/flag.h b/absl/flags/internal/flag.h
index 6154638c..b41f9a69 100644
--- a/absl/flags/internal/flag.h
+++ b/absl/flags/internal/flag.h
@@ -121,7 +121,7 @@ inline void* Clone(FlagOpFn op, const void* obj) {
   flags_internal::CopyConstruct(op, obj, res);
   return res;
 }
-// Returns true if parsing of input text is successfull.
+// Returns true if parsing of input text is successful.
 inline bool Parse(FlagOpFn op, absl::string_view text, void* dst,
                   std::string* error) {
   return op(FlagOp::kParse, &text, dst, error) != nullptr;
@@ -139,12 +139,12 @@ inline size_t Sizeof(FlagOpFn op) {
   return static_cast<size_t>(reinterpret_cast<intptr_t>(
       op(FlagOp::kSizeof, nullptr, nullptr, nullptr)));
 }
-// Returns fast type id coresponding to the value type.
+// Returns fast type id corresponding to the value type.
 inline FlagFastTypeId FastTypeId(FlagOpFn op) {
   return reinterpret_cast<FlagFastTypeId>(
       op(FlagOp::kFastTypeId, nullptr, nullptr, nullptr));
 }
-// Returns fast type id coresponding to the value type.
+// Returns fast type id corresponding to the value type.
 inline const std::type_info* RuntimeTypeId(FlagOpFn op) {
   return reinterpret_cast<const std::type_info*>(
       op(FlagOp::kRuntimeTypeId, nullptr, nullptr, nullptr));
@@ -223,12 +223,12 @@ extern const char kStrippedFlagHelp[];
 // first overload if possible. If help message is evaluatable on constexpr
 // context We'll be able to make FixedCharArray out of it and we'll choose first
 // overload. In this case the help message expression is immediately evaluated
-// and is used to construct the absl::Flag. No additionl code is generated by
+// and is used to construct the absl::Flag. No additional code is generated by
 // ABSL_FLAG Otherwise SFINAE kicks in and first overload is dropped from the
 // consideration, in which case the second overload will be used. The second
 // overload does not attempt to evaluate the help message expression
-// immediately and instead delays the evaluation by returing the function
-// pointer (&T::NonConst) genering the help message when necessary. This is
+// immediately and instead delays the evaluation by returning the function
+// pointer (&T::NonConst) generating the help message when necessary. This is
 // evaluatable in constexpr context, but the cost is an extra function being
 // generated in the ABSL_FLAG code.
 template <typename Gen, size_t N>
@@ -308,19 +308,20 @@ constexpr int64_t UninitializedFlagValue() {
 }
 
 template <typename T>
-using FlagUseValueAndInitBitStorage = std::integral_constant<
-    bool, absl::type_traits_internal::is_trivially_copyable<T>::value &&
-              std::is_default_constructible<T>::value && (sizeof(T) < 8)>;
+using FlagUseValueAndInitBitStorage =
+    std::integral_constant<bool, std::is_trivially_copyable<T>::value &&
+                                     std::is_default_constructible<T>::value &&
+                                     (sizeof(T) < 8)>;
 
 template <typename T>
-using FlagUseOneWordStorage = std::integral_constant<
-    bool, absl::type_traits_internal::is_trivially_copyable<T>::value &&
-              (sizeof(T) <= 8)>;
+using FlagUseOneWordStorage =
+    std::integral_constant<bool, std::is_trivially_copyable<T>::value &&
+                                     (sizeof(T) <= 8)>;
 
 template <class T>
-using FlagUseSequenceLockStorage = std::integral_constant<
-    bool, absl::type_traits_internal::is_trivially_copyable<T>::value &&
-              (sizeof(T) > 8)>;
+using FlagUseSequenceLockStorage =
+    std::integral_constant<bool, std::is_trivially_copyable<T>::value &&
+                                     (sizeof(T) > 8)>;
 
 enum class FlagValueStorageKind : uint8_t {
   kValueAndInitBit = 0,
diff --git a/absl/flags/internal/flag_msvc.inc b/absl/flags/internal/flag_msvc.inc
index c31bd27f..614d09fd 100644
--- a/absl/flags/internal/flag_msvc.inc
+++ b/absl/flags/internal/flag_msvc.inc
@@ -29,7 +29,7 @@
 // second level of protection is a global Mutex, so if two threads attempt to
 // construct the flag concurrently only one wins.
 //
-// This solution is based on a recomendation here:
+// This solution is based on a recommendation here:
 // https://developercommunity.visualstudio.com/content/problem/336946/class-with-constexpr-constructor-not-using-static.html?childToView=648454#comment-648454
 
 namespace flags_internal {
diff --git a/absl/flags/internal/parse.h b/absl/flags/internal/parse.h
index 0a7012fc..10c531b8 100644
--- a/absl/flags/internal/parse.h
+++ b/absl/flags/internal/parse.h
@@ -16,11 +16,14 @@
 #ifndef ABSL_FLAGS_INTERNAL_PARSE_H_
 #define ABSL_FLAGS_INTERNAL_PARSE_H_
 
+#include <iostream>
+#include <ostream>
 #include <string>
 #include <vector>
 
 #include "absl/base/config.h"
 #include "absl/flags/declare.h"
+#include "absl/flags/internal/usage.h"
 #include "absl/strings/string_view.h"
 
 ABSL_DECLARE_FLAG(std::vector<std::string>, flagfile);
@@ -32,7 +35,6 @@ namespace absl {
 ABSL_NAMESPACE_BEGIN
 namespace flags_internal {
 
-enum class ArgvListAction { kRemoveParsedArgs, kKeepParsedArgs };
 enum class UsageFlagsAction { kHandleUsage, kIgnoreUsage };
 enum class OnUndefinedFlag {
   kIgnoreUndefined,
@@ -40,10 +42,15 @@ enum class OnUndefinedFlag {
   kAbortIfUndefined
 };
 
-std::vector<char*> ParseCommandLineImpl(int argc, char* argv[],
-                                        ArgvListAction arg_list_act,
-                                        UsageFlagsAction usage_flag_act,
-                                        OnUndefinedFlag on_undef_flag);
+// This is not a public interface. This interface exists to expose the ability
+// to change help output stream in case of parsing errors. This is used by
+// internal unit tests to validate expected outputs.
+// When this was written, `EXPECT_EXIT` only supported matchers on stderr,
+// but not on stdout.
+std::vector<char*> ParseCommandLineImpl(
+    int argc, char* argv[], UsageFlagsAction usage_flag_action,
+    OnUndefinedFlag undef_flag_action,
+    std::ostream& error_help_output = std::cout);
 
 // --------------------------------------------------------------------
 // Inspect original command line
diff --git a/absl/flags/internal/usage.cc b/absl/flags/internal/usage.cc
index 5efc7b07..13852e14 100644
--- a/absl/flags/internal/usage.cc
+++ b/absl/flags/internal/usage.cc
@@ -18,6 +18,7 @@
 #include <stdint.h>
 
 #include <algorithm>
+#include <cstdlib>
 #include <functional>
 #include <iterator>
 #include <map>
@@ -91,8 +92,16 @@ class XMLElement {
         case '>':
           out << "&gt;";
           break;
+        case '\n':
+        case '\v':
+        case '\f':
+        case '\t':
+          out << " ";
+          break;
         default:
-          out << c;
+          if (IsValidXmlCharacter(static_cast<unsigned char>(c))) {
+            out << c;
+          }
           break;
       }
     }
@@ -101,6 +110,7 @@ class XMLElement {
   }
 
  private:
+  static bool IsValidXmlCharacter(unsigned char c) { return c >= 0x20; }
   absl::string_view tag_;
   absl::string_view txt_;
 };
@@ -130,7 +140,7 @@ class FlagHelpPrettyPrinter {
       for (auto line : absl::StrSplit(str, absl::ByAnyChar("\n\r"))) {
         if (!tokens.empty()) {
           // Keep line separators in the input string.
-          tokens.push_back("\n");
+          tokens.emplace_back("\n");
         }
         for (auto token :
              absl::StrSplit(line, absl::ByAnyChar(" \t"), absl::SkipEmpty())) {
@@ -354,8 +364,8 @@ void FlagsHelp(std::ostream& out, absl::string_view filter, HelpFormat format,
 // --------------------------------------------------------------------
 // Checks all the 'usage' command line flags to see if any have been set.
 // If so, handles them appropriately.
-int HandleUsageFlags(std::ostream& out,
-                     absl::string_view program_usage_message) {
+HelpMode HandleUsageFlags(std::ostream& out,
+                          absl::string_view program_usage_message) {
   switch (GetFlagsHelpMode()) {
     case HelpMode::kNone:
       break;
@@ -363,25 +373,24 @@ int HandleUsageFlags(std::ostream& out,
       flags_internal::FlagsHelpImpl(
           out, flags_internal::GetUsageConfig().contains_help_flags,
           GetFlagsHelpFormat(), program_usage_message);
-      return 1;
+      break;
 
     case HelpMode::kShort:
       flags_internal::FlagsHelpImpl(
           out, flags_internal::GetUsageConfig().contains_helpshort_flags,
           GetFlagsHelpFormat(), program_usage_message);
-      return 1;
+      break;
 
     case HelpMode::kFull:
       flags_internal::FlagsHelp(out, "", GetFlagsHelpFormat(),
                                 program_usage_message);
-      return 1;
+      break;
 
     case HelpMode::kPackage:
       flags_internal::FlagsHelpImpl(
           out, flags_internal::GetUsageConfig().contains_helppackage_flags,
           GetFlagsHelpFormat(), program_usage_message);
-
-      return 1;
+      break;
 
     case HelpMode::kMatch: {
       std::string substr = GetFlagsHelpMatchSubstr();
@@ -400,20 +409,19 @@ int HandleUsageFlags(std::ostream& out,
         flags_internal::FlagsHelpImpl(
             out, filter_cb, HelpFormat::kHumanReadable, program_usage_message);
       }
-
-      return 1;
+      break;
     }
     case HelpMode::kVersion:
       if (flags_internal::GetUsageConfig().version_string)
         out << flags_internal::GetUsageConfig().version_string();
       // Unlike help, we may be asking for version in a script, so return 0
-      return 0;
+      break;
 
     case HelpMode::kOnlyCheckArgs:
-      return 0;
+      break;
   }
 
-  return -1;
+  return GetFlagsHelpMode();
 }
 
 // --------------------------------------------------------------------
@@ -521,6 +529,22 @@ bool DeduceUsageFlags(absl::string_view name, absl::string_view value) {
   return false;
 }
 
+// --------------------------------------------------------------------
+
+void MaybeExit(HelpMode mode) {
+  switch (mode) {
+    case flags_internal::HelpMode::kNone:
+      return;
+    case flags_internal::HelpMode::kOnlyCheckArgs:
+    case flags_internal::HelpMode::kVersion:
+      std::exit(0);
+    default:  // For all the other modes we exit with 1
+      std::exit(1);
+  }
+}
+
+// --------------------------------------------------------------------
+
 }  // namespace flags_internal
 ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/flags/internal/usage.h b/absl/flags/internal/usage.h
index c0bcac57..a96cbf38 100644
--- a/absl/flags/internal/usage.h
+++ b/absl/flags/internal/usage.h
@@ -17,11 +17,11 @@
 #define ABSL_FLAGS_INTERNAL_USAGE_H_
 
 #include <iosfwd>
+#include <ostream>
 #include <string>
 
 #include "absl/base/config.h"
 #include "absl/flags/commandlineflag.h"
-#include "absl/flags/declare.h"
 #include "absl/strings/string_view.h"
 
 // --------------------------------------------------------------------
@@ -36,6 +36,18 @@ enum class HelpFormat {
   kHumanReadable,
 };
 
+// The kind of usage help requested.
+enum class HelpMode {
+  kNone,
+  kImportant,
+  kShort,
+  kFull,
+  kPackage,
+  kMatch,
+  kVersion,
+  kOnlyCheckArgs
+};
+
 // Streams the help message describing `flag` to `out`.
 // The default value for `flag` is included in the output.
 void FlagHelp(std::ostream& out, const CommandLineFlag& flag,
@@ -57,28 +69,18 @@ void FlagsHelp(std::ostream& out, absl::string_view filter,
 
 // If any of the 'usage' related command line flags (listed on the bottom of
 // this file) has been set this routine produces corresponding help message in
-// the specified output stream and returns:
-//  0 - if "version" or "only_check_flags" flags were set and handled.
-//  1 - if some other 'usage' related flag was set and handled.
-// -1 - if no usage flags were set on a commmand line.
-// Non negative return values are expected to be used as an exit code for a
-// binary.
-int HandleUsageFlags(std::ostream& out,
-                     absl::string_view program_usage_message);
+// the specified output stream and returns HelpMode that was handled. Otherwise
+// it returns HelpMode::kNone.
+HelpMode HandleUsageFlags(std::ostream& out,
+                          absl::string_view program_usage_message);
 
 // --------------------------------------------------------------------
-// Globals representing usage reporting flags
+// Encapsulates the logic of exiting the binary depending on handled help mode.
 
-enum class HelpMode {
-  kNone,
-  kImportant,
-  kShort,
-  kFull,
-  kPackage,
-  kMatch,
-  kVersion,
-  kOnlyCheckArgs
-};
+void MaybeExit(HelpMode mode);
+
+// --------------------------------------------------------------------
+// Globals representing usage reporting flags
 
 // Returns substring to filter help output (--help=substr argument)
 std::string GetFlagsHelpMatchSubstr();
diff --git a/absl/flags/internal/usage_test.cc b/absl/flags/internal/usage_test.cc
index 209a7be9..6847386f 100644
--- a/absl/flags/internal/usage_test.cc
+++ b/absl/flags/internal/usage_test.cc
@@ -24,7 +24,6 @@
 #include "gtest/gtest.h"
 #include "absl/flags/flag.h"
 #include "absl/flags/internal/parse.h"
-#include "absl/flags/internal/path_util.h"
 #include "absl/flags/internal/program_name.h"
 #include "absl/flags/reflection.h"
 #include "absl/flags/usage.h"
@@ -40,6 +39,8 @@ ABSL_FLAG(double, usage_reporting_test_flag_03, 1.03,
           "usage_reporting_test_flag_03 help message");
 ABSL_FLAG(int64_t, usage_reporting_test_flag_04, 1000000000000004L,
           "usage_reporting_test_flag_04 help message");
+ABSL_FLAG(std::string, usage_reporting_test_flag_07, "\r\n\f\v\a\b\t ",
+          "usage_reporting_test_flag_07 help \r\n\f\v\a\b\t ");
 
 static const char kTestUsageMessage[] = "Custom usage message";
 
@@ -204,8 +205,12 @@ TEST_F(UsageReportingTest, TestFlagsHelpHRF) {
 
       Some more help.
       Even more long long long long long long long long long long long long help
-      message.); default: "";
+      message.); default: "";)"
+
+      "\n    --usage_reporting_test_flag_07 (usage_reporting_test_flag_07 "
+      "help\n\n      \f\v\a\b ); default: \"\r\n\f\v\a\b\t \";\n"
 
+      R"(
 Try --helpfull to get a list of all flags or --help=substring shows help for
 flags which include specified substring in either in the name, or description or
 path.
@@ -256,7 +261,8 @@ path.
 
 TEST_F(UsageReportingTest, TestNoUsageFlags) {
   std::stringstream test_buf;
-  EXPECT_EQ(flags::HandleUsageFlags(test_buf, kTestUsageMessage), -1);
+  EXPECT_EQ(flags::HandleUsageFlags(test_buf, kTestUsageMessage),
+            flags::HelpMode::kNone);
 }
 
 // --------------------------------------------------------------------
@@ -265,9 +271,11 @@ TEST_F(UsageReportingTest, TestUsageFlag_helpshort) {
   flags::SetFlagsHelpMode(flags::HelpMode::kShort);
 
   std::stringstream test_buf;
-  EXPECT_EQ(flags::HandleUsageFlags(test_buf, kTestUsageMessage), 1);
-  EXPECT_EQ(test_buf.str(),
-            R"(usage_test: Custom usage message
+  EXPECT_EQ(flags::HandleUsageFlags(test_buf, kTestUsageMessage),
+            flags::HelpMode::kShort);
+  EXPECT_EQ(
+      test_buf.str(),
+      R"(usage_test: Custom usage message
 
   Flags from absl/flags/internal/usage_test.cc:
     --usage_reporting_test_flag_01 (usage_reporting_test_flag_01 help message);
@@ -284,8 +292,12 @@ TEST_F(UsageReportingTest, TestUsageFlag_helpshort) {
 
       Some more help.
       Even more long long long long long long long long long long long long help
-      message.); default: "";
+      message.); default: "";)"
+
+      "\n    --usage_reporting_test_flag_07 (usage_reporting_test_flag_07 "
+      "help\n\n      \f\v\a\b ); default: \"\r\n\f\v\a\b\t \";\n"
 
+      R"(
 Try --helpfull to get a list of all flags or --help=substring shows help for
 flags which include specified substring in either in the name, or description or
 path.
@@ -298,9 +310,11 @@ TEST_F(UsageReportingTest, TestUsageFlag_help_simple) {
   flags::SetFlagsHelpMode(flags::HelpMode::kImportant);
 
   std::stringstream test_buf;
-  EXPECT_EQ(flags::HandleUsageFlags(test_buf, kTestUsageMessage), 1);
-  EXPECT_EQ(test_buf.str(),
-            R"(usage_test: Custom usage message
+  EXPECT_EQ(flags::HandleUsageFlags(test_buf, kTestUsageMessage),
+            flags::HelpMode::kImportant);
+  EXPECT_EQ(
+      test_buf.str(),
+      R"(usage_test: Custom usage message
 
   Flags from absl/flags/internal/usage_test.cc:
     --usage_reporting_test_flag_01 (usage_reporting_test_flag_01 help message);
@@ -317,8 +331,12 @@ TEST_F(UsageReportingTest, TestUsageFlag_help_simple) {
 
       Some more help.
       Even more long long long long long long long long long long long long help
-      message.); default: "";
+      message.); default: "";)"
+
+      "\n    --usage_reporting_test_flag_07 (usage_reporting_test_flag_07 "
+      "help\n\n      \f\v\a\b ); default: \"\r\n\f\v\a\b\t \";\n"
 
+      R"(
 Try --helpfull to get a list of all flags or --help=substring shows help for
 flags which include specified substring in either in the name, or description or
 path.
@@ -332,7 +350,8 @@ TEST_F(UsageReportingTest, TestUsageFlag_help_one_flag) {
   flags::SetFlagsHelpMatchSubstr("usage_reporting_test_flag_06");
 
   std::stringstream test_buf;
-  EXPECT_EQ(flags::HandleUsageFlags(test_buf, kTestUsageMessage), 1);
+  EXPECT_EQ(flags::HandleUsageFlags(test_buf, kTestUsageMessage),
+            flags::HelpMode::kMatch);
   EXPECT_EQ(test_buf.str(),
             R"(usage_test: Custom usage message
 
@@ -356,9 +375,11 @@ TEST_F(UsageReportingTest, TestUsageFlag_help_multiple_flag) {
   flags::SetFlagsHelpMatchSubstr("test_flag");
 
   std::stringstream test_buf;
-  EXPECT_EQ(flags::HandleUsageFlags(test_buf, kTestUsageMessage), 1);
-  EXPECT_EQ(test_buf.str(),
-            R"(usage_test: Custom usage message
+  EXPECT_EQ(flags::HandleUsageFlags(test_buf, kTestUsageMessage),
+            flags::HelpMode::kMatch);
+  EXPECT_EQ(
+      test_buf.str(),
+      R"(usage_test: Custom usage message
 
   Flags from absl/flags/internal/usage_test.cc:
     --usage_reporting_test_flag_01 (usage_reporting_test_flag_01 help message);
@@ -375,8 +396,12 @@ TEST_F(UsageReportingTest, TestUsageFlag_help_multiple_flag) {
 
       Some more help.
       Even more long long long long long long long long long long long long help
-      message.); default: "";
+      message.); default: "";)"
+
+      "\n    --usage_reporting_test_flag_07 (usage_reporting_test_flag_07 "
+      "help\n\n      \f\v\a\b ); default: \"\r\n\f\v\a\b\t \";\n"
 
+      R"(
 Try --helpfull to get a list of all flags or --help=substring shows help for
 flags which include specified substring in either in the name, or description or
 path.
@@ -389,9 +414,11 @@ TEST_F(UsageReportingTest, TestUsageFlag_helppackage) {
   flags::SetFlagsHelpMode(flags::HelpMode::kPackage);
 
   std::stringstream test_buf;
-  EXPECT_EQ(flags::HandleUsageFlags(test_buf, kTestUsageMessage), 1);
-  EXPECT_EQ(test_buf.str(),
-            R"(usage_test: Custom usage message
+  EXPECT_EQ(flags::HandleUsageFlags(test_buf, kTestUsageMessage),
+            flags::HelpMode::kPackage);
+  EXPECT_EQ(
+      test_buf.str(),
+      R"(usage_test: Custom usage message
 
   Flags from absl/flags/internal/usage_test.cc:
     --usage_reporting_test_flag_01 (usage_reporting_test_flag_01 help message);
@@ -408,8 +435,12 @@ TEST_F(UsageReportingTest, TestUsageFlag_helppackage) {
 
       Some more help.
       Even more long long long long long long long long long long long long help
-      message.); default: "";
+      message.); default: "";)"
 
+      "\n    --usage_reporting_test_flag_07 (usage_reporting_test_flag_07 "
+      "help\n\n      \f\v\a\b ); default: \"\r\n\f\v\a\b\t \";\n"
+
+      R"(
 Try --helpfull to get a list of all flags or --help=substring shows help for
 flags which include specified substring in either in the name, or description or
 path.
@@ -422,7 +453,8 @@ TEST_F(UsageReportingTest, TestUsageFlag_version) {
   flags::SetFlagsHelpMode(flags::HelpMode::kVersion);
 
   std::stringstream test_buf;
-  EXPECT_EQ(flags::HandleUsageFlags(test_buf, kTestUsageMessage), 0);
+  EXPECT_EQ(flags::HandleUsageFlags(test_buf, kTestUsageMessage),
+            flags::HelpMode::kVersion);
 #ifndef NDEBUG
   EXPECT_EQ(test_buf.str(), "usage_test\nDebug build (NDEBUG not #defined)\n");
 #else
@@ -436,7 +468,8 @@ TEST_F(UsageReportingTest, TestUsageFlag_only_check_args) {
   flags::SetFlagsHelpMode(flags::HelpMode::kOnlyCheckArgs);
 
   std::stringstream test_buf;
-  EXPECT_EQ(flags::HandleUsageFlags(test_buf, kTestUsageMessage), 0);
+  EXPECT_EQ(flags::HandleUsageFlags(test_buf, kTestUsageMessage),
+            flags::HelpMode::kOnlyCheckArgs);
   EXPECT_EQ(test_buf.str(), "");
 }
 
@@ -447,7 +480,8 @@ TEST_F(UsageReportingTest, TestUsageFlag_helpon) {
   flags::SetFlagsHelpMatchSubstr("/bla-bla.");
 
   std::stringstream test_buf_01;
-  EXPECT_EQ(flags::HandleUsageFlags(test_buf_01, kTestUsageMessage), 1);
+  EXPECT_EQ(flags::HandleUsageFlags(test_buf_01, kTestUsageMessage),
+            flags::HelpMode::kMatch);
   EXPECT_EQ(test_buf_01.str(),
             R"(usage_test: Custom usage message
 
@@ -461,9 +495,11 @@ path.
   flags::SetFlagsHelpMatchSubstr("/usage_test.");
 
   std::stringstream test_buf_02;
-  EXPECT_EQ(flags::HandleUsageFlags(test_buf_02, kTestUsageMessage), 1);
-  EXPECT_EQ(test_buf_02.str(),
-            R"(usage_test: Custom usage message
+  EXPECT_EQ(flags::HandleUsageFlags(test_buf_02, kTestUsageMessage),
+            flags::HelpMode::kMatch);
+  EXPECT_EQ(
+      test_buf_02.str(),
+      R"(usage_test: Custom usage message
 
   Flags from absl/flags/internal/usage_test.cc:
     --usage_reporting_test_flag_01 (usage_reporting_test_flag_01 help message);
@@ -480,8 +516,12 @@ path.
 
       Some more help.
       Even more long long long long long long long long long long long long help
-      message.); default: "";
+      message.); default: "";)"
+
+      "\n    --usage_reporting_test_flag_07 (usage_reporting_test_flag_07 "
+      "help\n\n      \f\v\a\b ); default: \"\r\n\f\v\a\b\t \";\n"
 
+      R"(
 Try --helpfull to get a list of all flags or --help=substring shows help for
 flags which include specified substring in either in the name, or description or
 path.
diff --git a/absl/flags/marshalling.cc b/absl/flags/marshalling.cc
index 81f9cebd..dc69754f 100644
--- a/absl/flags/marshalling.cc
+++ b/absl/flags/marshalling.cc
@@ -19,6 +19,7 @@
 
 #include <cmath>
 #include <limits>
+#include <sstream>
 #include <string>
 #include <type_traits>
 #include <vector>
@@ -26,6 +27,7 @@
 #include "absl/base/config.h"
 #include "absl/base/log_severity.h"
 #include "absl/base/macros.h"
+#include "absl/numeric/int128.h"
 #include "absl/strings/ascii.h"
 #include "absl/strings/match.h"
 #include "absl/strings/numbers.h"
@@ -68,8 +70,10 @@ bool AbslParseFlag(absl::string_view text, bool* dst, std::string*) {
 // puts us in base 16.  But leading 0 does not put us in base 8. It
 // caused too many bugs when we had that behavior.
 static int NumericBase(absl::string_view text) {
-  const bool hex = (text.size() >= 2 && text[0] == '0' &&
-                    (text[1] == 'x' || text[1] == 'X'));
+  if (text.empty()) return 0;
+  size_t num_start = (text[0] == '-' || text[0] == '+') ? 1 : 0;
+  const bool hex = (text.size() >= num_start + 2 && text[num_start] == '0' &&
+                    (text[num_start + 1] == 'x' || text[num_start + 1] == 'X'));
   return hex ? 16 : 10;
 }
 
@@ -125,6 +129,32 @@ bool AbslParseFlag(absl::string_view text, unsigned long long* dst,
   return ParseFlagImpl(text, *dst);
 }
 
+bool AbslParseFlag(absl::string_view text, absl::int128* dst, std::string*) {
+  text = absl::StripAsciiWhitespace(text);
+
+  // check hex
+  int base = NumericBase(text);
+  if (!absl::numbers_internal::safe_strto128_base(text, dst, base)) {
+    return false;
+  }
+
+  return base == 16 ? absl::SimpleHexAtoi(text, dst)
+                    : absl::SimpleAtoi(text, dst);
+}
+
+bool AbslParseFlag(absl::string_view text, absl::uint128* dst, std::string*) {
+  text = absl::StripAsciiWhitespace(text);
+
+  // check hex
+  int base = NumericBase(text);
+  if (!absl::numbers_internal::safe_strtou128_base(text, dst, base)) {
+    return false;
+  }
+
+  return base == 16 ? absl::SimpleHexAtoi(text, dst)
+                    : absl::SimpleAtoi(text, dst);
+}
+
 // --------------------------------------------------------------------
 // AbslParseFlag for floating point types.
 
@@ -171,6 +201,17 @@ std::string Unparse(long v) { return absl::StrCat(v); }
 std::string Unparse(unsigned long v) { return absl::StrCat(v); }
 std::string Unparse(long long v) { return absl::StrCat(v); }
 std::string Unparse(unsigned long long v) { return absl::StrCat(v); }
+std::string Unparse(absl::int128 v) {
+  std::stringstream ss;
+  ss << v;
+  return ss.str();
+}
+std::string Unparse(absl::uint128 v) {
+  std::stringstream ss;
+  ss << v;
+  return ss.str();
+}
+
 template <typename T>
 std::string UnparseFloatingPointVal(T v) {
   // digits10 is guaranteed to roundtrip correctly in string -> value -> string
diff --git a/absl/flags/marshalling.h b/absl/flags/marshalling.h
index 325e75e5..301213a9 100644
--- a/absl/flags/marshalling.h
+++ b/absl/flags/marshalling.h
@@ -200,6 +200,7 @@
 #define ABSL_FLAGS_MARSHALLING_H_
 
 #include "absl/base/config.h"
+#include "absl/numeric/int128.h"
 
 #if defined(ABSL_HAVE_STD_OPTIONAL) && !defined(ABSL_USES_STD_OPTIONAL)
 #include <optional>
@@ -233,6 +234,8 @@ bool AbslParseFlag(absl::string_view, unsigned long*, std::string*);   // NOLINT
 bool AbslParseFlag(absl::string_view, long long*, std::string*);       // NOLINT
 bool AbslParseFlag(absl::string_view, unsigned long long*,             // NOLINT
                    std::string*);
+bool AbslParseFlag(absl::string_view, absl::int128*, std::string*);    // NOLINT
+bool AbslParseFlag(absl::string_view, absl::uint128*, std::string*);   // NOLINT
 bool AbslParseFlag(absl::string_view, float*, std::string*);
 bool AbslParseFlag(absl::string_view, double*, std::string*);
 bool AbslParseFlag(absl::string_view, std::string*, std::string*);
@@ -310,6 +313,8 @@ std::string Unparse(long v);                // NOLINT
 std::string Unparse(unsigned long v);       // NOLINT
 std::string Unparse(long long v);           // NOLINT
 std::string Unparse(unsigned long long v);  // NOLINT
+std::string Unparse(absl::int128 v);
+std::string Unparse(absl::uint128 v);
 std::string Unparse(float v);
 std::string Unparse(double v);
 
diff --git a/absl/flags/marshalling_test.cc b/absl/flags/marshalling_test.cc
index 7b6d2ad5..b0e055f5 100644
--- a/absl/flags/marshalling_test.cc
+++ b/absl/flags/marshalling_test.cc
@@ -137,11 +137,10 @@ TEST(MarshallingTest, TestInt16Parsing) {
   EXPECT_EQ(value, 16);
   EXPECT_TRUE(absl::ParseFlag("0X234", &value, &err));
   EXPECT_EQ(value, 564);
-  // TODO(rogeeff): fix below validations
-  EXPECT_FALSE(absl::ParseFlag("-0x7FFD", &value, &err));
-  EXPECT_NE(value, -3);
-  EXPECT_FALSE(absl::ParseFlag("+0x31", &value, &err));
-  EXPECT_NE(value, 49);
+  EXPECT_TRUE(absl::ParseFlag("-0x7FFD", &value, &err));
+  EXPECT_EQ(value, -32765);
+  EXPECT_TRUE(absl::ParseFlag("+0x31", &value, &err));
+  EXPECT_EQ(value, 49);
 
   // Whitespace handling
   EXPECT_TRUE(absl::ParseFlag("10  ", &value, &err));
@@ -194,9 +193,8 @@ TEST(MarshallingTest, TestUint16Parsing) {
   EXPECT_EQ(value, 16);
   EXPECT_TRUE(absl::ParseFlag("0X234", &value, &err));
   EXPECT_EQ(value, 564);
-  // TODO(rogeeff): fix below validations
-  EXPECT_FALSE(absl::ParseFlag("+0x31", &value, &err));
-  EXPECT_NE(value, 49);
+  EXPECT_TRUE(absl::ParseFlag("+0x31", &value, &err));
+  EXPECT_EQ(value, 49);
 
   // Whitespace handling
   EXPECT_TRUE(absl::ParseFlag("10  ", &value, &err));
@@ -254,11 +252,11 @@ TEST(MarshallingTest, TestInt32Parsing) {
   EXPECT_EQ(value, 16);
   EXPECT_TRUE(absl::ParseFlag("0X234", &value, &err));
   EXPECT_EQ(value, 564);
-  // TODO(rogeeff): fix below validations
-  EXPECT_FALSE(absl::ParseFlag("-0x7FFFFFFD", &value, &err));
-  EXPECT_NE(value, -3);
-  EXPECT_FALSE(absl::ParseFlag("+0x31", &value, &err));
-  EXPECT_NE(value, 49);
+
+  EXPECT_TRUE(absl::ParseFlag("-0x7FFFFFFD", &value, &err));
+  EXPECT_EQ(value, -2147483645);
+  EXPECT_TRUE(absl::ParseFlag("+0x31", &value, &err));
+  EXPECT_EQ(value, 49);
 
   // Whitespace handling
   EXPECT_TRUE(absl::ParseFlag("10  ", &value, &err));
@@ -311,9 +309,8 @@ TEST(MarshallingTest, TestUint32Parsing) {
   EXPECT_EQ(value, 564);
   EXPECT_TRUE(absl::ParseFlag("0xFFFFFFFD", &value, &err));
   EXPECT_EQ(value, 4294967293);
-  // TODO(rogeeff): fix below validations
-  EXPECT_FALSE(absl::ParseFlag("+0x31", &value, &err));
-  EXPECT_NE(value, 49);
+  EXPECT_TRUE(absl::ParseFlag("+0x31", &value, &err));
+  EXPECT_EQ(value, 49);
 
   // Whitespace handling
   EXPECT_TRUE(absl::ParseFlag("10  ", &value, &err));
@@ -371,11 +368,12 @@ TEST(MarshallingTest, TestInt64Parsing) {
   EXPECT_EQ(value, 16);
   EXPECT_TRUE(absl::ParseFlag("0XFFFAAABBBCCCDDD", &value, &err));
   EXPECT_EQ(value, 1152827684197027293);
-  // TODO(rogeeff): fix below validation
-  EXPECT_FALSE(absl::ParseFlag("-0x7FFFFFFFFFFFFFFE", &value, &err));
-  EXPECT_NE(value, -2);
-  EXPECT_FALSE(absl::ParseFlag("+0x31", &value, &err));
-  EXPECT_NE(value, 49);
+  EXPECT_TRUE(absl::ParseFlag("-0x7FFFFFFFFFFFFFFE", &value, &err));
+  EXPECT_EQ(value, -9223372036854775806);
+  EXPECT_TRUE(absl::ParseFlag("-0x02", &value, &err));
+  EXPECT_EQ(value, -2);
+  EXPECT_TRUE(absl::ParseFlag("+0x31", &value, &err));
+  EXPECT_EQ(value, 49);
 
   // Whitespace handling
   EXPECT_TRUE(absl::ParseFlag("10  ", &value, &err));
@@ -428,9 +426,8 @@ TEST(MarshallingTest, TestUInt64Parsing) {
   EXPECT_EQ(value, 16);
   EXPECT_TRUE(absl::ParseFlag("0XFFFF", &value, &err));
   EXPECT_EQ(value, 65535);
-  // TODO(rogeeff): fix below validation
-  EXPECT_FALSE(absl::ParseFlag("+0x31", &value, &err));
-  EXPECT_NE(value, 49);
+  EXPECT_TRUE(absl::ParseFlag("+0x31", &value, &err));
+  EXPECT_EQ(value, 49);
 
   // Whitespace handling
   EXPECT_TRUE(absl::ParseFlag("10  ", &value, &err));
@@ -455,6 +452,125 @@ TEST(MarshallingTest, TestUInt64Parsing) {
 
 // --------------------------------------------------------------------
 
+TEST(MarshallingTest, TestInt128Parsing) {
+  std::string err;
+  absl::int128 value;
+
+  // Decimal values.
+  EXPECT_TRUE(absl::ParseFlag("0", &value, &err));
+  EXPECT_EQ(value, 0);
+  EXPECT_TRUE(absl::ParseFlag("1", &value, &err));
+  EXPECT_EQ(value, 1);
+  EXPECT_TRUE(absl::ParseFlag("-1", &value, &err));
+  EXPECT_EQ(value, -1);
+  EXPECT_TRUE(absl::ParseFlag("123", &value, &err));
+  EXPECT_EQ(value, 123);
+  EXPECT_TRUE(absl::ParseFlag("-98765", &value, &err));
+  EXPECT_EQ(value, -98765);
+  EXPECT_TRUE(absl::ParseFlag("+3", &value, &err));
+  EXPECT_EQ(value, 3);
+
+  // Leading zero values.
+  EXPECT_TRUE(absl::ParseFlag("01", &value, &err));
+  EXPECT_EQ(value, 1);
+  EXPECT_TRUE(absl::ParseFlag("001", &value, &err));
+  EXPECT_EQ(value, 1);
+  EXPECT_TRUE(absl::ParseFlag("0000100", &value, &err));
+  EXPECT_EQ(value, 100);
+
+  // Hex values.
+  EXPECT_TRUE(absl::ParseFlag("0x10", &value, &err));
+  EXPECT_EQ(value, 16);
+  EXPECT_TRUE(absl::ParseFlag("0xFFFAAABBBCCCDDD", &value, &err));
+  EXPECT_EQ(value, 1152827684197027293);
+  EXPECT_TRUE(absl::ParseFlag("0xFFF0FFFFFFFFFFFFFFF", &value, &err));
+  EXPECT_EQ(value, absl::MakeInt128(0x000000000000fff, 0xFFFFFFFFFFFFFFF));
+
+  EXPECT_TRUE(absl::ParseFlag("-0x10000000000000000", &value, &err));
+  EXPECT_EQ(value, absl::MakeInt128(-1, 0));
+  EXPECT_TRUE(absl::ParseFlag("+0x31", &value, &err));
+  EXPECT_EQ(value, 49);
+
+  // Whitespace handling
+  EXPECT_TRUE(absl::ParseFlag("16  ", &value, &err));
+  EXPECT_EQ(value, 16);
+  EXPECT_TRUE(absl::ParseFlag("  16", &value, &err));
+  EXPECT_EQ(value, 16);
+  EXPECT_TRUE(absl::ParseFlag("  0100  ", &value, &err));
+  EXPECT_EQ(value, 100);
+  EXPECT_TRUE(absl::ParseFlag(" 0x7B    ", &value, &err));
+  EXPECT_EQ(value, 123);
+
+  // Invalid values.
+  EXPECT_FALSE(absl::ParseFlag("", &value, &err));
+  EXPECT_FALSE(absl::ParseFlag(" ", &value, &err));
+  EXPECT_FALSE(absl::ParseFlag("  ", &value, &err));
+  EXPECT_FALSE(absl::ParseFlag("--1", &value, &err));
+  EXPECT_FALSE(absl::ParseFlag("\n", &value, &err));
+  EXPECT_FALSE(absl::ParseFlag("\t", &value, &err));
+  EXPECT_FALSE(absl::ParseFlag("2U", &value, &err));
+  EXPECT_FALSE(absl::ParseFlag("FFF", &value, &err));
+}
+
+// --------------------------------------------------------------------
+
+TEST(MarshallingTest, TestUint128Parsing) {
+  std::string err;
+  absl::uint128 value;
+
+  // Decimal values.
+  EXPECT_TRUE(absl::ParseFlag("0", &value, &err));
+  EXPECT_EQ(value, 0);
+  EXPECT_TRUE(absl::ParseFlag("1", &value, &err));
+  EXPECT_EQ(value, 1);
+  EXPECT_TRUE(absl::ParseFlag("123", &value, &err));
+  EXPECT_EQ(value, 123);
+  EXPECT_TRUE(absl::ParseFlag("+3", &value, &err));
+  EXPECT_EQ(value, 3);
+
+  // Leading zero values.
+  EXPECT_TRUE(absl::ParseFlag("01", &value, &err));
+  EXPECT_EQ(value, 1);
+  EXPECT_TRUE(absl::ParseFlag("001", &value, &err));
+  EXPECT_EQ(value, 1);
+  EXPECT_TRUE(absl::ParseFlag("0000100", &value, &err));
+  EXPECT_EQ(value, 100);
+
+  // Hex values.
+  EXPECT_TRUE(absl::ParseFlag("0x10", &value, &err));
+  EXPECT_EQ(value, 16);
+  EXPECT_TRUE(absl::ParseFlag("0xFFFAAABBBCCCDDD", &value, &err));
+  EXPECT_EQ(value, 1152827684197027293);
+  EXPECT_TRUE(absl::ParseFlag("0xFFF0FFFFFFFFFFFFFFF", &value, &err));
+  EXPECT_EQ(value, absl::MakeInt128(0x000000000000fff, 0xFFFFFFFFFFFFFFF));
+  EXPECT_TRUE(absl::ParseFlag("+0x31", &value, &err));
+  EXPECT_EQ(value, 49);
+
+  // Whitespace handling
+  EXPECT_TRUE(absl::ParseFlag("16  ", &value, &err));
+  EXPECT_EQ(value, 16);
+  EXPECT_TRUE(absl::ParseFlag("  16", &value, &err));
+  EXPECT_EQ(value, 16);
+  EXPECT_TRUE(absl::ParseFlag("  0100  ", &value, &err));
+  EXPECT_EQ(value, 100);
+  EXPECT_TRUE(absl::ParseFlag(" 0x7B    ", &value, &err));
+  EXPECT_EQ(value, 123);
+
+  // Invalid values.
+  EXPECT_FALSE(absl::ParseFlag("", &value, &err));
+  EXPECT_FALSE(absl::ParseFlag(" ", &value, &err));
+  EXPECT_FALSE(absl::ParseFlag("  ", &value, &err));
+  EXPECT_FALSE(absl::ParseFlag("-1", &value, &err));
+  EXPECT_FALSE(absl::ParseFlag("--1", &value, &err));
+  EXPECT_FALSE(absl::ParseFlag("\n", &value, &err));
+  EXPECT_FALSE(absl::ParseFlag("\t", &value, &err));
+  EXPECT_FALSE(absl::ParseFlag("2U", &value, &err));
+  EXPECT_FALSE(absl::ParseFlag("FFF", &value, &err));
+  EXPECT_FALSE(absl::ParseFlag("-0x10000000000000000", &value, &err));
+}
+
+// --------------------------------------------------------------------
+
 TEST(MarshallingTest, TestFloatParsing) {
   std::string err;
   float value;
@@ -844,6 +960,40 @@ TEST(MarshallingTest, TestUint64Unparsing) {
 
 // --------------------------------------------------------------------
 
+TEST(MarshallingTest, TestInt128Unparsing) {
+  absl::int128 value;
+
+  value = 1;
+  EXPECT_EQ(absl::UnparseFlag(value), "1");
+  value = 0;
+  EXPECT_EQ(absl::UnparseFlag(value), "0");
+  value = -1;
+  EXPECT_EQ(absl::UnparseFlag(value), "-1");
+  value = 123456789L;
+  EXPECT_EQ(absl::UnparseFlag(value), "123456789");
+  value = -987654321L;
+  EXPECT_EQ(absl::UnparseFlag(value), "-987654321");
+  value = 0x7FFFFFFFFFFFFFFF;
+  EXPECT_EQ(absl::UnparseFlag(value), "9223372036854775807");
+}
+
+// --------------------------------------------------------------------
+
+TEST(MarshallingTest, TestUint128Unparsing) {
+  absl::uint128 value;
+
+  value = 1;
+  EXPECT_EQ(absl::UnparseFlag(value), "1");
+  value = 0;
+  EXPECT_EQ(absl::UnparseFlag(value), "0");
+  value = 123456789L;
+  EXPECT_EQ(absl::UnparseFlag(value), "123456789");
+  value = absl::MakeUint128(0, 0xFFFFFFFFFFFFFFFF);
+  EXPECT_EQ(absl::UnparseFlag(value), "18446744073709551615");
+}
+
+// --------------------------------------------------------------------
+
 TEST(MarshallingTest, TestFloatUnparsing) {
   float value;
 
diff --git a/absl/flags/parse.cc b/absl/flags/parse.cc
index fa953f55..4cdd9d0a 100644
--- a/absl/flags/parse.cc
+++ b/absl/flags/parse.cc
@@ -19,9 +19,10 @@
 
 #include <algorithm>
 #include <cstdint>
+#include <cstdlib>
 #include <fstream>
 #include <iostream>
-#include <iterator>
+#include <ostream>
 #include <string>
 #include <tuple>
 #include <utility>
@@ -98,6 +99,8 @@ struct SpecifiedFlagsCompare {
 ABSL_NAMESPACE_END
 }  // namespace absl
 
+// These flags influence how command line flags are parsed and are only intended
+// to be set on the command line.  Avoid reading or setting them from C++ code.
 ABSL_FLAG(std::vector<std::string>, flagfile, {},
           "comma-separated list of files to load flags from")
     .OnUpdate([]() {
@@ -147,6 +150,8 @@ ABSL_FLAG(std::vector<std::string>, tryfromenv, {},
       absl::flags_internal::tryfromenv_needs_processing = true;
     });
 
+// Rather than reading or setting --undefok from C++ code, please consider using
+// ABSL_RETIRED_FLAG instead.
 ABSL_FLAG(std::vector<std::string>, undefok, {},
           "comma-separated list of flag names that it is okay to specify "
           "on the command line even if the program does not define a flag "
@@ -190,7 +195,7 @@ bool ArgsList::ReadFromFlagfile(const std::string& flag_file_name) {
 
   // This argument represents fake argv[0], which should be present in all arg
   // lists.
-  args_.push_back("");
+  args_.emplace_back("");
 
   std::string line;
   bool success = true;
@@ -212,7 +217,7 @@ bool ArgsList::ReadFromFlagfile(const std::string& flag_file_name) {
         break;
       }
 
-      args_.push_back(std::string(stripped));
+      args_.emplace_back(stripped);
       continue;
     }
 
@@ -278,7 +283,7 @@ std::tuple<absl::string_view, absl::string_view, bool> SplitNameAndValue(
     return std::make_tuple("", "", false);
   }
 
-  auto equal_sign_pos = arg.find("=");
+  auto equal_sign_pos = arg.find('=');
 
   absl::string_view flag_name = arg.substr(0, equal_sign_pos);
 
@@ -367,7 +372,7 @@ bool ReadFlagsFromEnv(const std::vector<std::string>& flag_names,
 
   // This argument represents fake argv[0], which should be present in all arg
   // lists.
-  args.push_back("");
+  args.emplace_back("");
 
   for (const auto& flag_name : flag_names) {
     // Avoid infinite recursion.
@@ -416,7 +421,7 @@ bool HandleGeneratorFlags(std::vector<ArgsList>& input_args,
   // programmatically before invoking ParseCommandLine. Note that we do not
   // actually process arguments specified in the flagfile, but instead
   // create a secondary arguments list to be processed along with the rest
-  // of the comamnd line arguments. Since we always the process most recently
+  // of the command line arguments. Since we always the process most recently
   // created list of arguments first, this will result in flagfile argument
   // being processed before any other argument in the command line. If
   // FLAGS_flagfile contains more than one file name we create multiple new
@@ -599,6 +604,34 @@ bool CanIgnoreUndefinedFlag(absl::string_view flag_name) {
   return false;
 }
 
+// --------------------------------------------------------------------
+
+void ReportUnrecognizedFlags(
+    const std::vector<UnrecognizedFlag>& unrecognized_flags,
+    bool report_as_fatal_error) {
+  for (const auto& unrecognized : unrecognized_flags) {
+    // Verify if flag_name has the "no" already removed
+    std::vector<std::string> misspelling_hints;
+    if (unrecognized.source == UnrecognizedFlag::kFromArgv) {
+      misspelling_hints =
+          flags_internal::GetMisspellingHints(unrecognized.flag_name);
+    }
+
+    if (misspelling_hints.empty()) {
+      flags_internal::ReportUsageError(
+          absl::StrCat("Unknown command line flag '", unrecognized.flag_name,
+                       "'"),
+          report_as_fatal_error);
+    } else {
+      flags_internal::ReportUsageError(
+          absl::StrCat("Unknown command line flag '", unrecognized.flag_name,
+                       "'. Did you mean: ",
+                       absl::StrJoin(misspelling_hints, ", "), " ?"),
+          report_as_fatal_error);
+    }
+  }
+}
+
 }  // namespace
 
 // --------------------------------------------------------------------
@@ -638,7 +671,7 @@ std::vector<std::string> GetMisspellingHints(const absl::string_view flag) {
   const size_t maxCutoff = std::min(flag.size() / 2 + 1, kMaxDistance);
   auto undefok = absl::GetFlag(FLAGS_undefok);
   BestHints best_hints(static_cast<uint8_t>(maxCutoff));
-  absl::flags_internal::ForEachFlag([&](const CommandLineFlag& f) {
+  flags_internal::ForEachFlag([&](const CommandLineFlag& f) {
     if (best_hints.hints.size() >= kMaxHints) return;
     uint8_t distance = strings_internal::CappedDamerauLevenshteinDistance(
         flag, f.Name(), best_hints.best_distance);
@@ -664,59 +697,94 @@ std::vector<std::string> GetMisspellingHints(const absl::string_view flag) {
 // --------------------------------------------------------------------
 
 std::vector<char*> ParseCommandLineImpl(int argc, char* argv[],
-                                        ArgvListAction arg_list_act,
-                                        UsageFlagsAction usage_flag_act,
-                                        OnUndefinedFlag on_undef_flag) {
-  ABSL_INTERNAL_CHECK(argc > 0, "Missing argv[0]");
+                                        UsageFlagsAction usage_flag_action,
+                                        OnUndefinedFlag undef_flag_action,
+                                        std::ostream& error_help_output) {
+  std::vector<char*> positional_args;
+  std::vector<UnrecognizedFlag> unrecognized_flags;
 
-  // Once parsing has started we will not have more flag registrations.
-  // If we did, they would be missing during parsing, which is a problem on
-  // itself.
-  flags_internal::FinalizeRegistry();
+  auto help_mode = flags_internal::ParseAbseilFlagsOnlyImpl(
+      argc, argv, positional_args, unrecognized_flags, usage_flag_action);
 
-  // This routine does not return anything since we abort on failure.
-  CheckDefaultValuesParsingRoundtrip();
+  if (undef_flag_action != OnUndefinedFlag::kIgnoreUndefined) {
+    flags_internal::ReportUnrecognizedFlags(
+        unrecognized_flags,
+        (undef_flag_action == OnUndefinedFlag::kAbortIfUndefined));
 
-  std::vector<std::string> flagfile_value;
+    if (undef_flag_action == OnUndefinedFlag::kAbortIfUndefined) {
+      if (!unrecognized_flags.empty()) {
+        flags_internal::HandleUsageFlags(error_help_output,
+        ProgramUsageMessage()); std::exit(1);
+      }
+    }
+  }
+
+  flags_internal::MaybeExit(help_mode);
+
+  return positional_args;
+}
+
+// --------------------------------------------------------------------
 
+// This function handles all Abseil Flags and built-in usage flags and, if any
+// help mode was handled, it returns that help mode. The caller of this function
+// can decide to exit based on the returned help mode.
+// The caller may decide to handle unrecognized positional arguments and
+// unrecognized flags first before exiting.
+//
+// Returns:
+// * HelpMode::kFull if parsing errors were detected in recognized arguments
+// * The HelpMode that was handled in case when `usage_flag_action` is
+//   UsageFlagsAction::kHandleUsage and a usage flag was specified on the
+//   commandline
+// * Otherwise it returns HelpMode::kNone
+HelpMode ParseAbseilFlagsOnlyImpl(
+    int argc, char* argv[], std::vector<char*>& positional_args,
+    std::vector<UnrecognizedFlag>& unrecognized_flags,
+    UsageFlagsAction usage_flag_action) {
+  ABSL_INTERNAL_CHECK(argc > 0, "Missing argv[0]");
+
+  using flags_internal::ArgsList;
+  using flags_internal::specified_flags;
+
+  std::vector<std::string> flagfile_value;
   std::vector<ArgsList> input_args;
-  input_args.push_back(ArgsList(argc, argv));
 
-  std::vector<char*> output_args;
-  std::vector<char*> positional_args;
-  output_args.reserve(static_cast<size_t>(argc));
+  // Once parsing has started we will not allow more flag registrations.
+  flags_internal::FinalizeRegistry();
+
+  // This routine does not return anything since we abort on failure.
+  flags_internal::CheckDefaultValuesParsingRoundtrip();
 
-  // This is the list of undefined flags. The element of the list is the pair
-  // consisting of boolean indicating if flag came from command line (vs from
-  // some flag file we've read) and flag name.
-  // TODO(rogeeff): Eliminate the first element in the pair after cleanup.
-  std::vector<std::pair<bool, std::string>> undefined_flag_names;
+  input_args.push_back(ArgsList(argc, argv));
 
   // Set program invocation name if it is not set before.
-  if (ProgramInvocationName() == "UNKNOWN") {
+  if (flags_internal::ProgramInvocationName() == "UNKNOWN") {
     flags_internal::SetProgramInvocationName(argv[0]);
   }
-  output_args.push_back(argv[0]);
+  positional_args.push_back(argv[0]);
 
-  absl::MutexLock l(&specified_flags_guard);
+  absl::MutexLock l(&flags_internal::specified_flags_guard);
   if (specified_flags == nullptr) {
     specified_flags = new std::vector<const CommandLineFlag*>;
   } else {
     specified_flags->clear();
   }
 
-  // Iterate through the list of the input arguments. First level are arguments
-  // originated from argc/argv. Following levels are arguments originated from
-  // recursive parsing of flagfile(s).
+  // Iterate through the list of the input arguments. First level are
+  // arguments originated from argc/argv. Following levels are arguments
+  // originated from recursive parsing of flagfile(s).
   bool success = true;
   while (!input_args.empty()) {
-    // 10. First we process the built-in generator flags.
-    success &= HandleGeneratorFlags(input_args, flagfile_value);
+    // First we process the built-in generator flags.
+    success &= flags_internal::HandleGeneratorFlags(input_args, flagfile_value);
 
-    // 30. Select top-most (most recent) arguments list. If it is empty drop it
+    // Select top-most (most recent) arguments list. If it is empty drop it
     // and re-try.
     ArgsList& curr_list = input_args.back();
 
+    // Every ArgsList starts with real or fake program name, so we can always
+    // start by skipping it.
     curr_list.PopFront();
 
     if (curr_list.Size() == 0) {
@@ -724,13 +792,13 @@ std::vector<char*> ParseCommandLineImpl(int argc, char* argv[],
       continue;
     }
 
-    // 40. Pick up the front remaining argument in the current list. If current
-    // stack of argument lists contains only one element - we are processing an
-    // argument from the original argv.
+    // Handle the next argument in the current list. If the stack of argument
+    // lists contains only one element - we are processing an argument from
+    // the original argv.
     absl::string_view arg(curr_list.Front());
     bool arg_from_argv = input_args.size() == 1;
 
-    // 50. If argument does not start with - or is just "-" - this is
+    // If argument does not start with '-' or is just "-" - this is
     // positional argument.
     if (!absl::ConsumePrefix(&arg, "-") || arg.empty()) {
       ABSL_INTERNAL_CHECK(arg_from_argv,
@@ -740,12 +808,8 @@ std::vector<char*> ParseCommandLineImpl(int argc, char* argv[],
       continue;
     }
 
-    if (arg_from_argv && (arg_list_act == ArgvListAction::kKeepParsedArgs)) {
-      output_args.push_back(argv[curr_list.FrontIndex()]);
-    }
-
-    // 60. Split the current argument on '=' to figure out the argument
-    // name and value. If flag name is empty it means we've got "--". value
+    // Split the current argument on '=' to deduce the argument flag name and
+    // value. If flag name is empty it means we've got an "--" argument. Value
     // can be empty either if there were no '=' in argument string at all or
     // an argument looked like "--foo=". In a latter case is_empty_value is
     // true.
@@ -753,10 +817,11 @@ std::vector<char*> ParseCommandLineImpl(int argc, char* argv[],
     absl::string_view value;
     bool is_empty_value = false;
 
-    std::tie(flag_name, value, is_empty_value) = SplitNameAndValue(arg);
+    std::tie(flag_name, value, is_empty_value) =
+        flags_internal::SplitNameAndValue(arg);
 
-    // 70. "--" alone means what it does for GNU: stop flags parsing. We do
-    // not support positional arguments in flagfiles, so we just drop them.
+    // Standalone "--" argument indicates that the rest of the arguments are
+    // positional. We do not support positional arguments in flagfiles.
     if (flag_name.empty()) {
       ABSL_INTERNAL_CHECK(arg_from_argv,
                           "Flagfile cannot contain positional argument");
@@ -765,43 +830,36 @@ std::vector<char*> ParseCommandLineImpl(int argc, char* argv[],
       break;
     }
 
-    // 80. Locate the flag based on flag name. Handle both --foo and --nofoo
+    // Locate the flag based on flag name. Handle both --foo and --nofoo.
     CommandLineFlag* flag = nullptr;
     bool is_negative = false;
-    std::tie(flag, is_negative) = LocateFlag(flag_name);
+    std::tie(flag, is_negative) = flags_internal::LocateFlag(flag_name);
 
     if (flag == nullptr) {
       // Usage flags are not modeled as Abseil flags. Locate them separately.
       if (flags_internal::DeduceUsageFlags(flag_name, value)) {
         continue;
       }
-
-      if (on_undef_flag != OnUndefinedFlag::kIgnoreUndefined) {
-        undefined_flag_names.emplace_back(arg_from_argv,
-                                          std::string(flag_name));
-      }
+      unrecognized_flags.emplace_back(arg_from_argv
+                                          ? UnrecognizedFlag::kFromArgv
+                                          : UnrecognizedFlag::kFromFlagfile,
+                                      flag_name);
       continue;
     }
 
-    // 90. Deduce flag's value (from this or next argument)
-    auto curr_index = curr_list.FrontIndex();
+    // Deduce flag's value (from this or next argument).
     bool value_success = true;
-    std::tie(value_success, value) =
-        DeduceFlagValue(*flag, value, is_negative, is_empty_value, &curr_list);
+    std::tie(value_success, value) = flags_internal::DeduceFlagValue(
+        *flag, value, is_negative, is_empty_value, &curr_list);
     success &= value_success;
 
-    // If above call consumed an argument, it was a standalone value
-    if (arg_from_argv && (arg_list_act == ArgvListAction::kKeepParsedArgs) &&
-        (curr_index != curr_list.FrontIndex())) {
-      output_args.push_back(argv[curr_list.FrontIndex()]);
-    }
-
-    // 100. Set the located flag to a new new value, unless it is retired.
-    // Setting retired flag fails, but we ignoring it here while also reporting
-    // access to retired flag.
+    // Set the located flag to a new value, unless it is retired. Setting
+    // retired flag fails, but we ignoring it here while also reporting access
+    // to retired flag.
     std::string error;
     if (!flags_internal::PrivateHandleAccessor::ParseFrom(
-            *flag, value, SET_FLAGS_VALUE, kCommandLine, error)) {
+            *flag, value, flags_internal::SET_FLAGS_VALUE,
+            flags_internal::kCommandLine, error)) {
       if (flag->IsRetired()) continue;
 
       flags_internal::ReportUsageError(error, true);
@@ -811,78 +869,73 @@ std::vector<char*> ParseCommandLineImpl(int argc, char* argv[],
     }
   }
 
-  for (const auto& flag_name : undefined_flag_names) {
-    if (CanIgnoreUndefinedFlag(flag_name.second)) continue;
-    // Verify if flag_name has the "no" already removed
-    std::vector<std::string> flags;
-    if (flag_name.first) flags = GetMisspellingHints(flag_name.second);
-    if (flags.empty()) {
-      flags_internal::ReportUsageError(
-          absl::StrCat("Unknown command line flag '", flag_name.second, "'"),
-          true);
-    } else {
-      flags_internal::ReportUsageError(
-          absl::StrCat("Unknown command line flag '", flag_name.second,
-                       "'. Did you mean: ", absl::StrJoin(flags, ", "), " ?"),
-          true);
+  flags_internal::ResetGeneratorFlags(flagfile_value);
+
+  // All the remaining arguments are positional.
+  if (!input_args.empty()) {
+    for (size_t arg_index = input_args.back().FrontIndex();
+         arg_index < static_cast<size_t>(argc); ++arg_index) {
+      positional_args.push_back(argv[arg_index]);
     }
+  }
 
-    success = false;
+  // Trim and sort the vector.
+  specified_flags->shrink_to_fit();
+  std::sort(specified_flags->begin(), specified_flags->end(),
+            flags_internal::SpecifiedFlagsCompare{});
+
+  // Filter out unrecognized flags, which are ok to ignore.
+  std::vector<UnrecognizedFlag> filtered;
+  filtered.reserve(unrecognized_flags.size());
+  for (const auto& unrecognized : unrecognized_flags) {
+    if (flags_internal::CanIgnoreUndefinedFlag(unrecognized.flag_name))
+      continue;
+    filtered.push_back(unrecognized);
   }
 
-#if ABSL_FLAGS_STRIP_NAMES
+  std::swap(unrecognized_flags, filtered);
+
   if (!success) {
+#if ABSL_FLAGS_STRIP_NAMES
     flags_internal::ReportUsageError(
         "NOTE: command line flags are disabled in this build", true);
-  }
+#else
+    flags_internal::HandleUsageFlags(std::cerr, ProgramUsageMessage());
 #endif
-
-  if (!success) {
-    flags_internal::HandleUsageFlags(std::cout,
-                                     ProgramUsageMessage());
-    std::exit(1);
+    return HelpMode::kFull;  // We just need to make sure the exit with
+                             // code 1.
   }
 
-  if (usage_flag_act == UsageFlagsAction::kHandleUsage) {
-    int exit_code = flags_internal::HandleUsageFlags(
-        std::cout, ProgramUsageMessage());
+  return usage_flag_action == UsageFlagsAction::kHandleUsage
+             ? flags_internal::HandleUsageFlags(std::cout,
+                                                ProgramUsageMessage())
+             : HelpMode::kNone;
+}
 
-    if (exit_code != -1) {
-      std::exit(exit_code);
-    }
-  }
+}  // namespace flags_internal
 
-  ResetGeneratorFlags(flagfile_value);
+void ParseAbseilFlagsOnly(int argc, char* argv[],
+                          std::vector<char*>& positional_args,
+                          std::vector<UnrecognizedFlag>& unrecognized_flags) {
+  auto help_mode = flags_internal::ParseAbseilFlagsOnlyImpl(
+      argc, argv, positional_args, unrecognized_flags,
+      flags_internal::UsageFlagsAction::kHandleUsage);
 
-  // Reinstate positional args which were intermixed with flags in the arguments
-  // list.
-  for (auto arg : positional_args) {
-    output_args.push_back(arg);
-  }
+  flags_internal::MaybeExit(help_mode);
+}
 
-  // All the remaining arguments are positional.
-  if (!input_args.empty()) {
-    for (size_t arg_index = input_args.back().FrontIndex();
-         arg_index < static_cast<size_t>(argc); ++arg_index) {
-      output_args.push_back(argv[arg_index]);
-    }
-  }
+// --------------------------------------------------------------------
 
-  // Trim and sort the vector.
-  specified_flags->shrink_to_fit();
-  std::sort(specified_flags->begin(), specified_flags->end(),
-            SpecifiedFlagsCompare{});
-  return output_args;
+void ReportUnrecognizedFlags(
+    const std::vector<UnrecognizedFlag>& unrecognized_flags) {
+  flags_internal::ReportUnrecognizedFlags(unrecognized_flags, true);
 }
 
-}  // namespace flags_internal
-
 // --------------------------------------------------------------------
 
 std::vector<char*> ParseCommandLine(int argc, char* argv[]) {
   return flags_internal::ParseCommandLineImpl(
-      argc, argv, flags_internal::ArgvListAction::kRemoveParsedArgs,
-      flags_internal::UsageFlagsAction::kHandleUsage,
+      argc, argv, flags_internal::UsageFlagsAction::kHandleUsage,
       flags_internal::OnUndefinedFlag::kAbortIfUndefined);
 }
 
diff --git a/absl/flags/parse.h b/absl/flags/parse.h
index 929de2cb..f2a5cb10 100644
--- a/absl/flags/parse.h
+++ b/absl/flags/parse.h
@@ -23,6 +23,7 @@
 #ifndef ABSL_FLAGS_PARSE_H_
 #define ABSL_FLAGS_PARSE_H_
 
+#include <string>
 #include <vector>
 
 #include "absl/base/config.h"
@@ -31,27 +32,96 @@
 namespace absl {
 ABSL_NAMESPACE_BEGIN
 
+// This type represent information about an unrecognized flag in the command
+// line.
+struct UnrecognizedFlag {
+  enum Source { kFromArgv, kFromFlagfile };
+
+  explicit UnrecognizedFlag(Source s, absl::string_view f)
+      : source(s), flag_name(f) {}
+  // This field indicates where we found this flag: on the original command line
+  // or read in some flag file.
+  Source source;
+  // Name of the flag we did not recognize in --flag_name=value or --flag_name.
+  std::string flag_name;
+};
+
+inline bool operator==(const UnrecognizedFlag& lhs,
+                       const UnrecognizedFlag& rhs) {
+  return lhs.source == rhs.source && lhs.flag_name == rhs.flag_name;
+}
+
+namespace flags_internal {
+
+HelpMode ParseAbseilFlagsOnlyImpl(
+    int argc, char* argv[], std::vector<char*>& positional_args,
+    std::vector<UnrecognizedFlag>& unrecognized_flags,
+    UsageFlagsAction usage_flag_action);
+
+}  // namespace flags_internal
+
+// ParseAbseilFlagsOnly()
+//
+// Parses a list of command-line arguments, passed in the `argc` and `argv[]`
+// parameters, into a set of Abseil Flag values, returning any unparsed
+// arguments in `positional_args` and `unrecognized_flags` output parameters.
+//
+// This function classifies all the arguments (including content of the
+// flagfiles, if any) into one of the following groups:
+//
+//   * arguments specified as "--flag=value" or "--flag value" that match
+//     registered or built-in Abseil Flags. These are "Abseil Flag arguments."
+//   * arguments specified as "--flag" that are unrecognized as Abseil Flags
+//   * arguments that are not specified as "--flag" are positional arguments
+//   * arguments that follow the flag-terminating delimiter (`--`) are also
+//     treated as positional arguments regardless of their syntax.
+//
+// All of the deduced Abseil Flag arguments are then parsed into their
+// corresponding flag values. If any syntax errors are found in these arguments,
+// the binary exits with code 1.
+//
+// This function also handles Abseil Flags built-in usage flags (e.g. --help)
+// if any were present on the command line.
+//
+// All the remaining positional arguments including original program name
+// (argv[0]) are are returned in the `positional_args` output parameter.
+//
+// All unrecognized flags that are not otherwise ignored are returned in the
+// `unrecognized_flags` output parameter. Note that the special `undefok`
+// flag allows you to specify flags which can be safely ignored; `undefok`
+// specifies these flags as a comma-separated list. Any unrecognized flags
+// that appear within `undefok` will therefore be ignored and not included in
+// the `unrecognized_flag` output parameter.
+//
+void ParseAbseilFlagsOnly(int argc, char* argv[],
+                          std::vector<char*>& positional_args,
+                          std::vector<UnrecognizedFlag>& unrecognized_flags);
+
+// ReportUnrecognizedFlags()
+//
+// Reports an error to `stderr` for all non-ignored unrecognized flags in
+// the provided `unrecognized_flags` list.
+void ReportUnrecognizedFlags(
+    const std::vector<UnrecognizedFlag>& unrecognized_flags);
+
 // ParseCommandLine()
 //
-// Parses the set of command-line arguments passed in the `argc` (argument
-// count) and `argv[]` (argument vector) parameters from `main()`, assigning
-// values to any defined Abseil flags. (Any arguments passed after the
-// flag-terminating delimiter (`--`) are treated as positional arguments and
-// ignored.)
-//
-// Any command-line flags (and arguments to those flags) are parsed into Abseil
-// Flag values, if those flags are defined. Any undefined flags will either
-// return an error, or be ignored if that flag is designated using `undefok` to
-// indicate "undefined is OK."
-//
-// Any command-line positional arguments not part of any command-line flag (or
-// arguments to a flag) are returned in a vector, with the program invocation
-// name at position 0 of that vector. (Note that this includes positional
-// arguments after the flag-terminating delimiter `--`.)
-//
-// After all flags and flag arguments are parsed, this function looks for any
-// built-in usage flags (e.g. `--help`), and if any were specified, it reports
-// help messages and then exits the program.
+// First parses Abseil Flags only from the command line according to the
+// description in `ParseAbseilFlagsOnly`. In addition this function handles
+// unrecognized and usage flags.
+//
+// If any unrecognized flags are located they are reported using
+// `ReportUnrecognizedFlags`.
+//
+// If any errors detected during command line parsing, this routine reports a
+// usage message and aborts the program.
+//
+// If any built-in usage flags were specified on the command line (e.g.
+// `--help`), this function reports help messages and then gracefully exits the
+// program.
+//
+// This function returns all the remaining positional arguments collected by
+// `ParseAbseilFlagsOnly`.
 std::vector<char*> ParseCommandLine(int argc, char* argv[]);
 
 ABSL_NAMESPACE_END
diff --git a/absl/flags/parse_test.cc b/absl/flags/parse_test.cc
index 418b0e55..97b78980 100644
--- a/absl/flags/parse_test.cc
+++ b/absl/flags/parse_test.cc
@@ -17,20 +17,19 @@
 
 #include <stdlib.h>
 
-#include <cstddef>
 #include <fstream>
+#include <iostream>
 #include <string>
 #include <vector>
 
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
-#include "absl/base/internal/raw_logging.h"
 #include "absl/base/internal/scoped_set_env.h"
-#include "absl/flags/declare.h"
 #include "absl/flags/flag.h"
 #include "absl/flags/internal/parse.h"
 #include "absl/flags/internal/usage.h"
 #include "absl/flags/reflection.h"
+#include "absl/log/log.h"
 #include "absl/strings/str_cat.h"
 #include "absl/strings/string_view.h"
 #include "absl/strings/substitute.h"
@@ -151,8 +150,7 @@ const std::string& GetTestTempDir() {
     }
 
     if (res->empty()) {
-      ABSL_INTERNAL_LOG(FATAL,
-                        "Failed to make temporary directory for data files");
+      LOG(FATAL) << "Failed to make temporary directory for data files";
     }
 
 #ifdef _WIN32
@@ -199,7 +197,7 @@ constexpr const char* const ff2_data[] = {
 // Builds flagfile flag in the flagfile_flag buffer and returns it. This
 // function also creates a temporary flagfile based on FlagfileData input.
 // We create a flagfile in a temporary directory with the name specified in
-// FlagfileData and populate it with lines specifed in FlagfileData. If $0 is
+// FlagfileData and populate it with lines specified in FlagfileData. If $0 is
 // referenced in any of the lines in FlagfileData they are replaced with
 // temporary directory location. This way we can test inclusion of one flagfile
 // from another flagfile.
@@ -237,7 +235,9 @@ ABSL_RETIRED_FLAG(std::string, legacy_str, "l", "");
 namespace {
 
 namespace flags = absl::flags_internal;
+using testing::AllOf;
 using testing::ElementsAreArray;
+using testing::HasSubstr;
 
 class ParseTest : public testing::Test {
  public:
@@ -250,6 +250,38 @@ class ParseTest : public testing::Test {
 // --------------------------------------------------------------------
 
 template <int N>
+flags::HelpMode InvokeParseAbslOnlyImpl(const char* (&in_argv)[N]) {
+  std::vector<char*> positional_args;
+  std::vector<absl::UnrecognizedFlag> unrecognized_flags;
+
+  return flags::ParseAbseilFlagsOnlyImpl(N, const_cast<char**>(in_argv),
+                                         positional_args, unrecognized_flags,
+                                         flags::UsageFlagsAction::kHandleUsage);
+}
+
+// --------------------------------------------------------------------
+
+template <int N>
+void InvokeParseAbslOnly(const char* (&in_argv)[N]) {
+  std::vector<char*> positional_args;
+  std::vector<absl::UnrecognizedFlag> unrecognized_flags;
+
+  absl::ParseAbseilFlagsOnly(2, const_cast<char**>(in_argv), positional_args,
+                             unrecognized_flags);
+}
+
+// --------------------------------------------------------------------
+
+template <int N>
+std::vector<char*> InvokeParseCommandLineImpl(const char* (&in_argv)[N]) {
+  return flags::ParseCommandLineImpl(
+      N, const_cast<char**>(in_argv), flags::UsageFlagsAction::kHandleUsage,
+      flags::OnUndefinedFlag::kAbortIfUndefined, std::cerr);
+}
+
+// --------------------------------------------------------------------
+
+template <int N>
 std::vector<char*> InvokeParse(const char* (&in_argv)[N]) {
   return absl::ParseCommandLine(N, const_cast<char**>(in_argv));
 }
@@ -854,129 +886,66 @@ TEST_F(ParseTest, TestReadingFlagsFromEnvMoxedWithRegularFlags) {
 
 // --------------------------------------------------------------------
 
-TEST_F(ParseTest, TestKeepParsedArgs) {
-  const char* in_args1[] = {
-      "testbin",        "arg1", "--bool_flag",
-      "--int_flag=211", "arg2", "--double_flag=1.1",
-      "--string_flag",  "asd",  "--",
-      "arg3",           "arg4",
-  };
-
-  auto out_args1 = InvokeParse(in_args1);
-
-  EXPECT_THAT(
-      out_args1,
-      ElementsAreArray({absl::string_view("testbin"), absl::string_view("arg1"),
-                        absl::string_view("arg2"), absl::string_view("arg3"),
-                        absl::string_view("arg4")}));
-
-  auto out_args2 = flags::ParseCommandLineImpl(
-      11, const_cast<char**>(in_args1), flags::ArgvListAction::kKeepParsedArgs,
-      flags::UsageFlagsAction::kHandleUsage,
-      flags::OnUndefinedFlag::kAbortIfUndefined);
-
-  EXPECT_THAT(
-      out_args2,
-      ElementsAreArray({absl::string_view("testbin"),
-                        absl::string_view("--bool_flag"),
-                        absl::string_view("--int_flag=211"),
-                        absl::string_view("--double_flag=1.1"),
-                        absl::string_view("--string_flag"),
-                        absl::string_view("asd"), absl::string_view("--"),
-                        absl::string_view("arg1"), absl::string_view("arg2"),
-                        absl::string_view("arg3"), absl::string_view("arg4")}));
-}
-
-// --------------------------------------------------------------------
-
-TEST_F(ParseTest, TestIgnoreUndefinedFlags) {
+TEST_F(ParseDeathTest, TestSimpleHelpFlagHandling) {
   const char* in_args1[] = {
       "testbin",
-      "arg1",
-      "--undef_flag=aa",
-      "--int_flag=21",
+      "--help",
   };
 
-  auto out_args1 = flags::ParseCommandLineImpl(
-      4, const_cast<char**>(in_args1), flags::ArgvListAction::kRemoveParsedArgs,
-      flags::UsageFlagsAction::kHandleUsage,
-      flags::OnUndefinedFlag::kIgnoreUndefined);
-
-  EXPECT_THAT(out_args1, ElementsAreArray({absl::string_view("testbin"),
-                                           absl::string_view("arg1")}));
-
-  EXPECT_EQ(absl::GetFlag(FLAGS_int_flag), 21);
+  EXPECT_EQ(InvokeParseAbslOnlyImpl(in_args1), flags::HelpMode::kImportant);
+  EXPECT_EXIT(InvokeParse(in_args1), testing::ExitedWithCode(1), "");
 
   const char* in_args2[] = {
       "testbin",
-      "arg1",
-      "--undef_flag=aa",
-      "--string_flag=AA",
+      "--help",
+      "--int_flag=3",
   };
 
-  auto out_args2 = flags::ParseCommandLineImpl(
-      4, const_cast<char**>(in_args2), flags::ArgvListAction::kKeepParsedArgs,
-      flags::UsageFlagsAction::kHandleUsage,
-      flags::OnUndefinedFlag::kIgnoreUndefined);
+  EXPECT_EQ(InvokeParseAbslOnlyImpl(in_args2), flags::HelpMode::kImportant);
+  EXPECT_EQ(absl::GetFlag(FLAGS_int_flag), 3);
 
-  EXPECT_THAT(
-      out_args2,
-      ElementsAreArray(
-          {absl::string_view("testbin"), absl::string_view("--undef_flag=aa"),
-           absl::string_view("--string_flag=AA"), absl::string_view("arg1")}));
+  const char* in_args3[] = {"testbin", "--help", "some_positional_arg"};
 
-  EXPECT_EQ(absl::GetFlag(FLAGS_string_flag), "AA");
+  EXPECT_EQ(InvokeParseAbslOnlyImpl(in_args3), flags::HelpMode::kImportant);
 }
 
 // --------------------------------------------------------------------
 
-TEST_F(ParseDeathTest, TestSimpleHelpFlagHandling) {
+TEST_F(ParseTest, TestSubstringHelpFlagHandling) {
   const char* in_args1[] = {
       "testbin",
-      "--help",
-  };
-
-  EXPECT_EXIT(InvokeParse(in_args1), testing::ExitedWithCode(1), "");
-
-  const char* in_args2[] = {
-      "testbin",
-      "--help",
-      "--int_flag=3",
+      "--help=abcd",
   };
 
-  auto out_args2 = flags::ParseCommandLineImpl(
-      3, const_cast<char**>(in_args2), flags::ArgvListAction::kRemoveParsedArgs,
-      flags::UsageFlagsAction::kIgnoreUsage,
-      flags::OnUndefinedFlag::kAbortIfUndefined);
-
-  EXPECT_EQ(flags::GetFlagsHelpMode(), flags::HelpMode::kImportant);
-  EXPECT_EQ(absl::GetFlag(FLAGS_int_flag), 3);
+  EXPECT_EQ(InvokeParseAbslOnlyImpl(in_args1), flags::HelpMode::kMatch);
+  EXPECT_EQ(flags::GetFlagsHelpMatchSubstr(), "abcd");
 }
 
 // --------------------------------------------------------------------
 
-TEST_F(ParseDeathTest, TestSubstringHelpFlagHandling) {
+TEST_F(ParseDeathTest, TestVersionHandling) {
   const char* in_args1[] = {
       "testbin",
-      "--help=abcd",
+      "--version",
   };
 
-  auto out_args1 = flags::ParseCommandLineImpl(
-      2, const_cast<char**>(in_args1), flags::ArgvListAction::kRemoveParsedArgs,
-      flags::UsageFlagsAction::kIgnoreUsage,
-      flags::OnUndefinedFlag::kAbortIfUndefined);
+  EXPECT_EQ(InvokeParseAbslOnlyImpl(in_args1), flags::HelpMode::kVersion);
+}
 
-  EXPECT_EQ(flags::GetFlagsHelpMode(), flags::HelpMode::kMatch);
-  EXPECT_EQ(flags::GetFlagsHelpMatchSubstr(), "abcd");
+// --------------------------------------------------------------------
 
-  const char* in_args2[] = {"testbin", "--help", "some_positional_arg"};
+TEST_F(ParseTest, TestCheckArgsHandling) {
+  const char* in_args1[] = {"testbin", "--only_check_args", "--int_flag=211"};
 
-  auto out_args2 = flags::ParseCommandLineImpl(
-      3, const_cast<char**>(in_args2), flags::ArgvListAction::kRemoveParsedArgs,
-      flags::UsageFlagsAction::kIgnoreUsage,
-      flags::OnUndefinedFlag::kAbortIfUndefined);
+  EXPECT_EQ(InvokeParseAbslOnlyImpl(in_args1), flags::HelpMode::kOnlyCheckArgs);
+  EXPECT_EXIT(InvokeParseAbslOnly(in_args1), testing::ExitedWithCode(0), "");
+  EXPECT_EXIT(InvokeParse(in_args1), testing::ExitedWithCode(0), "");
 
-  EXPECT_EQ(flags::GetFlagsHelpMode(), flags::HelpMode::kImportant);
+  const char* in_args2[] = {"testbin", "--only_check_args", "--unknown_flag=a"};
+
+  EXPECT_EQ(InvokeParseAbslOnlyImpl(in_args2), flags::HelpMode::kOnlyCheckArgs);
+  EXPECT_EXIT(InvokeParseAbslOnly(in_args2), testing::ExitedWithCode(0), "");
+  EXPECT_EXIT(InvokeParse(in_args2), testing::ExitedWithCode(1), "");
 }
 
 // --------------------------------------------------------------------
@@ -1001,4 +970,118 @@ TEST_F(ParseTest, WasPresentOnCommandLine) {
 
 // --------------------------------------------------------------------
 
+TEST_F(ParseTest, ParseAbseilFlagsOnlySuccess) {
+  const char* in_args[] = {
+      "testbin",
+      "arg1",
+      "--bool_flag",
+      "--int_flag=211",
+      "arg2",
+      "--double_flag=1.1",
+      "--undef_flag1",
+      "--undef_flag2=123",
+      "--string_flag",
+      "asd",
+      "--",
+      "--some_flag",
+      "arg4",
+  };
+
+  std::vector<char*> positional_args;
+  std::vector<absl::UnrecognizedFlag> unrecognized_flags;
+
+  absl::ParseAbseilFlagsOnly(13, const_cast<char**>(in_args), positional_args,
+                             unrecognized_flags);
+  EXPECT_THAT(positional_args,
+              ElementsAreArray(
+                  {absl::string_view("testbin"), absl::string_view("arg1"),
+                   absl::string_view("arg2"), absl::string_view("--some_flag"),
+                   absl::string_view("arg4")}));
+  EXPECT_THAT(unrecognized_flags,
+              ElementsAreArray(
+                  {absl::UnrecognizedFlag(absl::UnrecognizedFlag::kFromArgv,
+                                          "undef_flag1"),
+                   absl::UnrecognizedFlag(absl::UnrecognizedFlag::kFromArgv,
+                                          "undef_flag2")}));
+}
+
+// --------------------------------------------------------------------
+
+TEST_F(ParseDeathTest, ParseAbseilFlagsOnlyFailure) {
+  const char* in_args[] = {
+      "testbin",
+      "--int_flag=21.1",
+  };
+
+  EXPECT_DEATH_IF_SUPPORTED(
+      InvokeParseAbslOnly(in_args),
+      "Illegal value '21.1' specified for flag 'int_flag'");
+}
+
+// --------------------------------------------------------------------
+
+TEST_F(ParseTest, UndefOkFlagsAreIgnored) {
+  const char* in_args[] = {
+      "testbin",           "--undef_flag1",
+      "--undef_flag2=123", "--undefok=undef_flag2",
+      "--undef_flag3",     "value",
+  };
+
+  std::vector<char*> positional_args;
+  std::vector<absl::UnrecognizedFlag> unrecognized_flags;
+
+  absl::ParseAbseilFlagsOnly(6, const_cast<char**>(in_args), positional_args,
+                             unrecognized_flags);
+  EXPECT_THAT(positional_args, ElementsAreArray({absl::string_view("testbin"),
+                                                 absl::string_view("value")}));
+  EXPECT_THAT(unrecognized_flags,
+              ElementsAreArray(
+                  {absl::UnrecognizedFlag(absl::UnrecognizedFlag::kFromArgv,
+                                          "undef_flag1"),
+                   absl::UnrecognizedFlag(absl::UnrecognizedFlag::kFromArgv,
+                                          "undef_flag3")}));
+}
+
+// --------------------------------------------------------------------
+
+TEST_F(ParseTest, AllUndefOkFlagsAreIgnored) {
+  const char* in_args[] = {
+      "testbin",
+      "--undef_flag1",
+      "--undef_flag2=123",
+      "--undefok=undef_flag2,undef_flag1,undef_flag3",
+      "--undef_flag3",
+      "value",
+      "--",
+      "--undef_flag4",
+  };
+
+  std::vector<char*> positional_args;
+  std::vector<absl::UnrecognizedFlag> unrecognized_flags;
+
+  absl::ParseAbseilFlagsOnly(8, const_cast<char**>(in_args), positional_args,
+                             unrecognized_flags);
+  EXPECT_THAT(positional_args,
+              ElementsAreArray({absl::string_view("testbin"),
+                                absl::string_view("value"),
+                                absl::string_view("--undef_flag4")}));
+  EXPECT_THAT(unrecognized_flags, testing::IsEmpty());
+}
+
+// --------------------------------------------------------------------
+
+TEST_F(ParseDeathTest, ExitOnUnrecognizedFlagPrintsHelp) {
+  const char* in_args[] = {
+      "testbin",
+      "--undef_flag1",
+      "--help=int_flag",
+  };
+
+  EXPECT_EXIT(InvokeParseCommandLineImpl(in_args), testing::ExitedWithCode(1),
+              AllOf(HasSubstr("Unknown command line flag 'undef_flag1'"),
+                    HasSubstr("Try --helpfull to get a list of all flags")));
+}
+
+// --------------------------------------------------------------------
+
 }  // namespace
diff --git a/absl/flags/usage.cc b/absl/flags/usage.cc
index 452f6675..267a5039 100644
--- a/absl/flags/usage.cc
+++ b/absl/flags/usage.cc
@@ -21,6 +21,7 @@
 #include "absl/base/attributes.h"
 #include "absl/base/config.h"
 #include "absl/base/const_init.h"
+#include "absl/base/internal/raw_logging.h"
 #include "absl/base/thread_annotations.h"
 #include "absl/flags/internal/usage.h"
 #include "absl/strings/string_view.h"
diff --git a/absl/functional/BUILD.bazel b/absl/functional/BUILD.bazel
index c4fbce98..4ceac539 100644
--- a/absl/functional/BUILD.bazel
+++ b/absl/functional/BUILD.bazel
@@ -92,6 +92,7 @@ cc_library(
     copts = ABSL_DEFAULT_COPTS,
     linkopts = ABSL_DEFAULT_LINKOPTS,
     deps = [
+        ":any_invocable",
         "//absl/base:base_internal",
         "//absl/base:core_headers",
         "//absl/meta:type_traits",
@@ -104,6 +105,7 @@ cc_test(
     srcs = ["function_ref_test.cc"],
     copts = ABSL_TEST_COPTS,
     deps = [
+        ":any_invocable",
         ":function_ref",
         "//absl/container:test_instance_tracker",
         "//absl/memory",
diff --git a/absl/functional/CMakeLists.txt b/absl/functional/CMakeLists.txt
index c0f6eaaa..c704e049 100644
--- a/absl/functional/CMakeLists.txt
+++ b/absl/functional/CMakeLists.txt
@@ -39,7 +39,7 @@ absl_cc_test(
     "any_invocable_test.cc"
     "internal/any_invocable.h"
   COPTS
-    ${ABSL_DEFAULT_COPTS}
+    ${ABSL_TEST_COPTS}
   DEPS
     absl::any_invocable
     absl::base_internal
@@ -90,6 +90,7 @@ absl_cc_library(
   DEPS
     absl::base_internal
     absl::core_headers
+    absl::any_invocable
     absl::meta
   PUBLIC
 )
diff --git a/absl/functional/any_invocable.h b/absl/functional/any_invocable.h
index 3e783c87..68d88253 100644
--- a/absl/functional/any_invocable.h
+++ b/absl/functional/any_invocable.h
@@ -266,9 +266,17 @@ class AnyInvocable : private internal_any_invocable::Impl<Sig> {
   // Exchanges the targets of `*this` and `other`.
   void swap(AnyInvocable& other) noexcept { std::swap(*this, other); }
 
-  // abl::AnyInvocable::operator bool()
+  // absl::AnyInvocable::operator bool()
   //
   // Returns `true` if `*this` is not empty.
+  //
+  // WARNING: An `AnyInvocable` that wraps an empty `std::function` is not
+  // itself empty. This behavior is consistent with the standard equivalent
+  // `std::move_only_function`.
+  //
+  // In other words:
+  //   std::function<void()> f;  // empty
+  //   absl::AnyInvocable<void()> a = std::move(f);  // not empty
   explicit operator bool() const noexcept { return this->HasValue(); }
 
   // Invokes the target object of `*this`. `*this` must not be empty.
diff --git a/absl/functional/any_invocable_test.cc b/absl/functional/any_invocable_test.cc
index 1ed85407..a740faa6 100644
--- a/absl/functional/any_invocable_test.cc
+++ b/absl/functional/any_invocable_test.cc
@@ -1418,7 +1418,7 @@ TYPED_TEST_P(AnyInvTestRvalue, NonConstCrashesOnSecondCall) {
   // Ensure we're still valid
   EXPECT_TRUE(static_cast<bool>(fun));  // NOLINT(bugprone-use-after-move)
 
-#if !defined(NDEBUG) || ABSL_OPTION_HARDENED == 1
+#if !defined(NDEBUG)
   EXPECT_DEATH_IF_SUPPORTED(std::move(fun)(7, 8, 9), "");
 #endif
 }
@@ -1431,14 +1431,14 @@ TYPED_TEST_P(AnyInvTestRvalue, QualifierIndependentObjectLifetime) {
   auto refs = std::make_shared<std::nullptr_t>();
   {
     AnyInvType fun([refs](auto&&...) noexcept { return 0; });
-    EXPECT_FALSE(refs.unique());
+    EXPECT_GT(refs.use_count(), 1);
 
     std::move(fun)(7, 8, 9);
 
     // Ensure destructor hasn't run even if rref-qualified
-    EXPECT_FALSE(refs.unique());
+    EXPECT_GT(refs.use_count(), 1);
   }
-  EXPECT_TRUE(refs.unique());
+  EXPECT_EQ(refs.use_count(), 1);
 }
 
 // NOTE: This test suite originally attempted to enumerate all possible
diff --git a/absl/functional/bind_front.h b/absl/functional/bind_front.h
index f9075bd1..a956eb02 100644
--- a/absl/functional/bind_front.h
+++ b/absl/functional/bind_front.h
@@ -46,7 +46,7 @@ ABSL_NAMESPACE_BEGIN
 //
 // Like `std::bind()`, `absl::bind_front()` is implicitly convertible to
 // `std::function`.  In particular, it may be used as a simpler replacement for
-// `std::bind()` in most cases, as it does not require  placeholders to be
+// `std::bind()` in most cases, as it does not require placeholders to be
 // specified. More importantly, it provides more reliable correctness guarantees
 // than `std::bind()`; while `std::bind()` will silently ignore passing more
 // parameters than expected, for example, `absl::bind_front()` will report such
diff --git a/absl/functional/function_ref.h b/absl/functional/function_ref.h
index f9779607..2b9139d3 100644
--- a/absl/functional/function_ref.h
+++ b/absl/functional/function_ref.h
@@ -66,11 +66,11 @@ class FunctionRef;
 
 // FunctionRef
 //
-// An `absl::FunctionRef` is a lightweight wrapper to any invokable object with
+// An `absl::FunctionRef` is a lightweight wrapper to any invocable object with
 // a compatible signature. Generally, an `absl::FunctionRef` should only be used
 // as an argument type and should be preferred as an argument over a const
 // reference to a `std::function`. `absl::FunctionRef` itself does not allocate,
-// although the wrapped invokable may.
+// although the wrapped invocable may.
 //
 // Example:
 //
@@ -98,7 +98,7 @@ class FunctionRef<R(Args...)> {
                               std::is_convertible<FR, R>::value>::type;
 
  public:
-  // Constructs a FunctionRef from any invokable type.
+  // Constructs a FunctionRef from any invocable type.
   template <typename F, typename = EnableIfCompatible<const F&>>
   // NOLINTNEXTLINE(runtime/explicit)
   FunctionRef(const F& f ABSL_ATTRIBUTE_LIFETIME_BOUND)
diff --git a/absl/functional/function_ref_test.cc b/absl/functional/function_ref_test.cc
index 412027cd..c61117eb 100644
--- a/absl/functional/function_ref_test.cc
+++ b/absl/functional/function_ref_test.cc
@@ -20,6 +20,7 @@
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
 #include "absl/container/internal/test_instance_tracker.h"
+#include "absl/functional/any_invocable.h"
 #include "absl/memory/memory.h"
 
 namespace absl {
@@ -157,6 +158,25 @@ TEST(FunctionRef, NullMemberPtrAssertFails) {
   EXPECT_DEBUG_DEATH({ FunctionRef<int(const S& s)> ref(mem_ptr); }, "");
 }
 
+TEST(FunctionRef, NullStdFunctionAssertPasses) {
+  std::function<void()> function = []() {};
+  FunctionRef<void()> ref(function);
+}
+
+TEST(FunctionRef, NullStdFunctionAssertFails) {
+  std::function<void()> function = nullptr;
+  EXPECT_DEBUG_DEATH({ FunctionRef<void()> ref(function); }, "");
+}
+
+TEST(FunctionRef, NullAnyInvocableAssertPasses) {
+  AnyInvocable<void() const> invocable = []() {};
+  FunctionRef<void()> ref(invocable);
+}
+TEST(FunctionRef, NullAnyInvocableAssertFails) {
+  AnyInvocable<void() const> invocable = nullptr;
+  EXPECT_DEBUG_DEATH({ FunctionRef<void()> ref(invocable); }, "");
+}
+
 #endif  // GTEST_HAS_DEATH_TEST
 
 TEST(FunctionRef, CopiesAndMovesPerPassByValue) {
@@ -237,7 +257,7 @@ TEST(FunctionRef, PassByValueTypes) {
       "Reference types should be preserved");
 
   // Make sure the address of an object received by reference is the same as the
-  // addess of the object passed by the caller.
+  // address of the object passed by the caller.
   {
     LargeTrivial obj;
     auto test = [&obj](LargeTrivial& input) { ASSERT_EQ(&input, &obj); };
@@ -253,6 +273,16 @@ TEST(FunctionRef, PassByValueTypes) {
   }
 }
 
+TEST(FunctionRef, ReferenceToIncompleteType) {
+  struct IncompleteType;
+  auto test = [](IncompleteType&) {};
+  absl::FunctionRef<void(IncompleteType&)> ref(test);
+
+  struct IncompleteType {};
+  IncompleteType obj;
+  ref(obj);
+}
+
 }  // namespace
 ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/functional/internal/any_invocable.h b/absl/functional/internal/any_invocable.h
index 6bfbda18..f096bb02 100644
--- a/absl/functional/internal/any_invocable.h
+++ b/absl/functional/internal/any_invocable.h
@@ -56,6 +56,7 @@
 #include <cassert>
 #include <cstddef>
 #include <cstring>
+#include <exception>
 #include <functional>
 #include <initializer_list>
 #include <memory>
@@ -134,8 +135,16 @@ void InvokeR(F&& f, P&&... args) {
 template <class ReturnType, class F, class... P,
           absl::enable_if_t<!std::is_void<ReturnType>::value, int> = 0>
 ReturnType InvokeR(F&& f, P&&... args) {
+  // GCC 12 has a false-positive -Wmaybe-uninitialized warning here.
+#if ABSL_INTERNAL_HAVE_MIN_GNUC_VERSION(12, 0)
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wmaybe-uninitialized"
+#endif
   return absl::base_internal::invoke(std::forward<F>(f),
                                      std::forward<P>(args)...);
+#if ABSL_INTERNAL_HAVE_MIN_GNUC_VERSION(12, 0)
+#pragma GCC diagnostic pop
+#endif
 }
 
 //
@@ -196,7 +205,7 @@ union TypeErasedState {
 template <class T>
 T& ObjectInLocalStorage(TypeErasedState* const state) {
   // We launder here because the storage may be reused with the same type.
-#if ABSL_INTERNAL_CPLUSPLUS_LANG >= 201703L
+#if defined(__cpp_lib_launder) && __cpp_lib_launder >= 201606L
   return *std::launder(reinterpret_cast<T*>(&state->storage));
 #elif ABSL_HAVE_BUILTIN(__builtin_launder)
   return *__builtin_launder(reinterpret_cast<T*>(&state->storage));
@@ -431,11 +440,11 @@ class CoreImpl {
 
   CoreImpl() noexcept : manager_(EmptyManager), invoker_(nullptr) {}
 
-  enum class TargetType : int {
-    kPointer = 0,
-    kCompatibleAnyInvocable = 1,
-    kIncompatibleAnyInvocable = 2,
-    kOther = 3,
+  enum class TargetType {
+    kPointer,
+    kCompatibleAnyInvocable,
+    kIncompatibleAnyInvocable,
+    kOther,
   };
 
   // Note: QualDecayedTRef here includes the cv-ref qualifiers associated with
@@ -457,8 +466,7 @@ class CoreImpl {
     // NOTE: We only use integers instead of enums as template parameters in
     // order to work around a bug on C++14 under MSVC 2017.
     // See b/236131881.
-    Initialize<static_cast<int>(kTargetType), QualDecayedTRef>(
-        std::forward<F>(f));
+    Initialize<kTargetType, QualDecayedTRef>(std::forward<F>(f));
   }
 
   // Note: QualTRef here includes the cv-ref qualifiers associated with the
@@ -487,7 +495,7 @@ class CoreImpl {
     // object.
     Clear();
 
-    // Perform the actual move/destory operation on the target function.
+    // Perform the actual move/destroy operation on the target function.
     other.manager_(FunctionToCall::relocate_from_to, &other.state_, &state_);
     manager_ = other.manager_;
     invoker_ = other.invoker_;
@@ -509,8 +517,8 @@ class CoreImpl {
     invoker_ = nullptr;
   }
 
-  template <int target_type, class QualDecayedTRef, class F,
-            absl::enable_if_t<target_type == 0, int> = 0>
+  template <TargetType target_type, class QualDecayedTRef, class F,
+            absl::enable_if_t<target_type == TargetType::kPointer, int> = 0>
   void Initialize(F&& f) {
 // This condition handles types that decay into pointers, which includes
 // function references. Since function references cannot be null, GCC warns
@@ -534,8 +542,9 @@ class CoreImpl {
     InitializeStorage<QualDecayedTRef>(std::forward<F>(f));
   }
 
-  template <int target_type, class QualDecayedTRef, class F,
-            absl::enable_if_t<target_type == 1, int> = 0>
+  template <TargetType target_type, class QualDecayedTRef, class F,
+            absl::enable_if_t<
+                target_type == TargetType::kCompatibleAnyInvocable, int> = 0>
   void Initialize(F&& f) {
     // In this case we can "steal the guts" of the other AnyInvocable.
     f.manager_(FunctionToCall::relocate_from_to, &f.state_, &state_);
@@ -546,8 +555,9 @@ class CoreImpl {
     f.invoker_ = nullptr;
   }
 
-  template <int target_type, class QualDecayedTRef, class F,
-            absl::enable_if_t<target_type == 2, int> = 0>
+  template <TargetType target_type, class QualDecayedTRef, class F,
+            absl::enable_if_t<
+                target_type == TargetType::kIncompatibleAnyInvocable, int> = 0>
   void Initialize(F&& f) {
     if (f.HasValue()) {
       InitializeStorage<QualDecayedTRef>(std::forward<F>(f));
@@ -557,8 +567,8 @@ class CoreImpl {
     }
   }
 
-  template <int target_type, class QualDecayedTRef, class F,
-            typename = absl::enable_if_t<target_type == 3>>
+  template <TargetType target_type, class QualDecayedTRef, class F,
+            typename = absl::enable_if_t<target_type == TargetType::kOther>>
   void Initialize(F&& f) {
     InitializeStorage<QualDecayedTRef>(std::forward<F>(f));
   }
@@ -810,19 +820,22 @@ using CanAssignReferenceWrapper = TrueAlias<
         : Core(absl::in_place_type<absl::decay_t<T> inv_quals>,                \
                std::forward<Args>(args)...) {}                                 \
                                                                                \
+    /*Raises a fatal error when the AnyInvocable is invoked after a move*/     \
+    static ReturnType InvokedAfterMove(                                        \
+      TypeErasedState*,                                                        \
+      ForwardedParameterType<P>...) noexcept(noex) {                           \
+      ABSL_HARDENING_ASSERT(false && "AnyInvocable use-after-move");           \
+      std::terminate();                                                        \
+    }                                                                          \
+                                                                               \
     InvokerType<noex, ReturnType, P...>* ExtractInvoker() cv {                 \
       using QualifiedTestType = int cv ref;                                    \
       auto* invoker = this->invoker_;                                          \
       if (!std::is_const<QualifiedTestType>::value &&                          \
           std::is_rvalue_reference<QualifiedTestType>::value) {                \
-        ABSL_HARDENING_ASSERT([this]() {                                       \
+        ABSL_ASSERT([this]() {                                                 \
           /* We checked that this isn't const above, so const_cast is safe */  \
-          const_cast<Impl*>(this)->invoker_ =                                  \
-              [](TypeErasedState*,                                             \
-                 ForwardedParameterType<P>...) noexcept(noex) -> ReturnType {  \
-            ABSL_HARDENING_ASSERT(false && "AnyInvocable use-after-move");     \
-            std::terminate();                                                  \
-          };                                                                   \
+          const_cast<Impl*>(this)->invoker_ = InvokedAfterMove;                \
           return this->HasValue();                                             \
         }());                                                                  \
       }                                                                        \
diff --git a/absl/functional/internal/function_ref.h b/absl/functional/internal/function_ref.h
index b5bb8b43..1cd34a3c 100644
--- a/absl/functional/internal/function_ref.h
+++ b/absl/functional/internal/function_ref.h
@@ -20,6 +20,7 @@
 #include <type_traits>
 
 #include "absl/base/internal/invoke.h"
+#include "absl/functional/any_invocable.h"
 #include "absl/meta/type_traits.h"
 
 namespace absl {
@@ -40,18 +41,21 @@ union VoidPtr {
 // Chooses the best type for passing T as an argument.
 // Attempt to be close to SystemV AMD64 ABI. Objects with trivial copy ctor are
 // passed by value.
+template <typename T,
+          bool IsLValueReference = std::is_lvalue_reference<T>::value>
+struct PassByValue : std::false_type {};
+
 template <typename T>
-constexpr bool PassByValue() {
-  return !std::is_lvalue_reference<T>::value &&
-         absl::is_trivially_copy_constructible<T>::value &&
-         absl::is_trivially_copy_assignable<
-             typename std::remove_cv<T>::type>::value &&
-         std::is_trivially_destructible<T>::value &&
-         sizeof(T) <= 2 * sizeof(void*);
-}
+struct PassByValue<T, /*IsLValueReference=*/false>
+    : std::integral_constant<bool,
+                             absl::is_trivially_copy_constructible<T>::value &&
+                                 absl::is_trivially_copy_assignable<
+                                     typename std::remove_cv<T>::type>::value &&
+                                 std::is_trivially_destructible<T>::value &&
+                                 sizeof(T) <= 2 * sizeof(void*)> {};
 
 template <typename T>
-struct ForwardT : std::conditional<PassByValue<T>(), T, T&&> {};
+struct ForwardT : std::conditional<PassByValue<T>::value, T, T&&> {};
 
 // An Invoker takes a pointer to the type-erased invokable object, followed by
 // the arguments that the invokable object expects.
@@ -87,6 +91,12 @@ void AssertNonNull(const std::function<Sig>& f) {
   (void)f;
 }
 
+template <typename Sig>
+void AssertNonNull(const AnyInvocable<Sig>& f) {
+  assert(f != nullptr);
+  (void)f;
+}
+
 template <typename F>
 void AssertNonNull(const F&) {}
 
diff --git a/absl/hash/BUILD.bazel b/absl/hash/BUILD.bazel
index a0db919b..4346fc49 100644
--- a/absl/hash/BUILD.bazel
+++ b/absl/hash/BUILD.bazel
@@ -68,13 +68,17 @@ cc_library(
 
 cc_test(
     name = "hash_test",
-    srcs = ["hash_test.cc"],
+    srcs = [
+        "hash_test.cc",
+        "internal/hash_test.h",
+    ],
     copts = ABSL_TEST_COPTS,
     linkopts = ABSL_DEFAULT_LINKOPTS,
     deps = [
         ":hash",
         ":hash_testing",
         ":spy_hash_state",
+        "//absl/base:config",
         "//absl/base:core_headers",
         "//absl/container:btree",
         "//absl/container:flat_hash_map",
@@ -88,6 +92,27 @@ cc_test(
     ],
 )
 
+cc_test(
+    name = "hash_instantiated_test",
+    srcs = [
+        "hash_instantiated_test.cc",
+        "internal/hash_test.h",
+    ],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":hash",
+        ":hash_testing",
+        "//absl/base:config",
+        "//absl/container:btree",
+        "//absl/container:flat_hash_map",
+        "//absl/container:flat_hash_set",
+        "//absl/container:node_hash_map",
+        "//absl/container:node_hash_set",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
 cc_binary(
     name = "hash_benchmark",
     testonly = 1,
@@ -158,6 +183,7 @@ cc_library(
     deps = [
         "//absl/base:config",
         "//absl/base:endian",
+        "//absl/base:prefetch",
         "//absl/numeric:int128",
     ],
 )
diff --git a/absl/hash/CMakeLists.txt b/absl/hash/CMakeLists.txt
index f99f35bc..65fd2a5f 100644
--- a/absl/hash/CMakeLists.txt
+++ b/absl/hash/CMakeLists.txt
@@ -64,6 +64,7 @@ absl_cc_test(
     hash_test
   SRCS
     "hash_test.cc"
+    "internal/hash_test.h"
   COPTS
     ${ABSL_TEST_COPTS}
   DEPS
@@ -82,6 +83,26 @@ absl_cc_test(
     GTest::gmock_main
 )
 
+absl_cc_test(
+  NAME
+    hash_instantiated_test
+  SRCS
+    "hash_test.cc"
+    "internal/hash_test.h"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  DEPS
+    absl::hash
+    absl::hash_testing
+    absl::config
+    absl::btree
+    absl::flat_hash_map
+    absl::flat_hash_set
+    absl::node_hash_map
+    absl::node_hash_set
+    GTest::gtest_main
+)
+
 # Internal-only target, do not depend on directly.
 #
 # Note: Even though external code should not depend on this target
@@ -144,6 +165,7 @@ absl_cc_library(
     absl::config
     absl::endian
     absl::int128
+    absl::prefetch
 )
 
 absl_cc_test(
diff --git a/absl/hash/hash.h b/absl/hash/hash.h
index 74e2d7c0..470cca48 100644
--- a/absl/hash/hash.h
+++ b/absl/hash/hash.h
@@ -42,7 +42,7 @@
 //
 // `absl::Hash` may also produce different values from different dynamically
 // loaded libraries. For this reason, `absl::Hash` values must never cross
-// boundries in dynamically loaded libraries (including when used in types like
+// boundaries in dynamically loaded libraries (including when used in types like
 // hash containers.)
 //
 // `absl::Hash` is intended to strongly mix input bits with a target of passing
@@ -110,9 +110,12 @@ ABSL_NAMESPACE_BEGIN
 //   * std::unique_ptr and std::shared_ptr
 //   * All string-like types including:
 //     * absl::Cord
-//     * std::string
-//     * std::string_view (as well as any instance of std::basic_string that
-//       uses char and std::char_traits)
+//     * std::string (as well as any instance of std::basic_string that
+//       uses one of {char, wchar_t, char16_t, char32_t} and its associated
+//       std::char_traits)
+//     * std::string_view (as well as any instance of std::basic_string_view
+//       that uses one of {char, wchar_t, char16_t, char32_t} and its associated
+//       std::char_traits)
 //  * All the standard sequence containers (provided the elements are hashable)
 //  * All the standard associative containers (provided the elements are
 //    hashable)
diff --git a/absl/hash/hash_instantiated_test.cc b/absl/hash/hash_instantiated_test.cc
new file mode 100644
index 00000000..e65de9ca
--- /dev/null
+++ b/absl/hash/hash_instantiated_test.cc
@@ -0,0 +1,224 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// This file contains a few select absl::Hash tests that, due to their reliance
+// on INSTANTIATE_TYPED_TEST_SUITE_P, require a large amount of memory to
+// compile. Put new tests in hash_test.cc, not this file.
+
+#include "absl/hash/hash.h"
+
+#include <stddef.h>
+
+#include <algorithm>
+#include <deque>
+#include <forward_list>
+#include <initializer_list>
+#include <list>
+#include <map>
+#include <set>
+#include <string>
+#include <type_traits>
+#include <unordered_map>
+#include <unordered_set>
+#include <utility>
+#include <vector>
+
+#include "gtest/gtest.h"
+#include "absl/container/btree_map.h"
+#include "absl/container/btree_set.h"
+#include "absl/container/flat_hash_map.h"
+#include "absl/container/flat_hash_set.h"
+#include "absl/container/node_hash_map.h"
+#include "absl/container/node_hash_set.h"
+#include "absl/hash/hash_testing.h"
+#include "absl/hash/internal/hash_test.h"
+
+namespace {
+
+using ::absl::hash_test_internal::is_hashable;
+using ::absl::hash_test_internal::TypeErasedContainer;
+
+// Dummy type with unordered equality and hashing semantics.  This preserves
+// input order internally, and is used below to ensure we get test coverage
+// for equal sequences with different iteraton orders.
+template <typename T>
+class UnorderedSequence {
+ public:
+  UnorderedSequence() = default;
+  template <typename TT>
+  UnorderedSequence(std::initializer_list<TT> l)
+      : values_(l.begin(), l.end()) {}
+  template <typename ForwardIterator,
+            typename std::enable_if<!std::is_integral<ForwardIterator>::value,
+                                    bool>::type = true>
+  UnorderedSequence(ForwardIterator begin, ForwardIterator end)
+      : values_(begin, end) {}
+  // one-argument constructor of value type T, to appease older toolchains that
+  // get confused by one-element initializer lists in some contexts
+  explicit UnorderedSequence(const T& v) : values_(&v, &v + 1) {}
+
+  using value_type = T;
+
+  size_t size() const { return values_.size(); }
+  typename std::vector<T>::const_iterator begin() const {
+    return values_.begin();
+  }
+  typename std::vector<T>::const_iterator end() const { return values_.end(); }
+
+  friend bool operator==(const UnorderedSequence& lhs,
+                         const UnorderedSequence& rhs) {
+    return lhs.size() == rhs.size() &&
+           std::is_permutation(lhs.begin(), lhs.end(), rhs.begin());
+  }
+  friend bool operator!=(const UnorderedSequence& lhs,
+                         const UnorderedSequence& rhs) {
+    return !(lhs == rhs);
+  }
+  template <typename H>
+  friend H AbslHashValue(H h, const UnorderedSequence& u) {
+    return H::combine(H::combine_unordered(std::move(h), u.begin(), u.end()),
+                      u.size());
+  }
+
+ private:
+  std::vector<T> values_;
+};
+
+template <typename T>
+class HashValueSequenceTest : public testing::Test {};
+TYPED_TEST_SUITE_P(HashValueSequenceTest);
+
+TYPED_TEST_P(HashValueSequenceTest, BasicUsage) {
+  EXPECT_TRUE((is_hashable<TypeParam>::value));
+
+  using IntType = typename TypeParam::value_type;
+  auto a = static_cast<IntType>(0);
+  auto b = static_cast<IntType>(23);
+  auto c = static_cast<IntType>(42);
+
+  std::vector<TypeParam> exemplars = {
+      TypeParam(),        TypeParam(),        TypeParam{a, b, c},
+      TypeParam{a, c, b}, TypeParam{c, a, b}, TypeParam{a},
+      TypeParam{a, a},    TypeParam{a, a, a}, TypeParam{a, a, b},
+      TypeParam{a, b, a}, TypeParam{b, a, a}, TypeParam{a, b},
+      TypeParam{b, c}};
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(exemplars));
+}
+
+REGISTER_TYPED_TEST_SUITE_P(HashValueSequenceTest, BasicUsage);
+using IntSequenceTypes = testing::Types<
+    std::deque<int>, std::forward_list<int>, std::list<int>, std::vector<int>,
+    std::vector<bool>, TypeErasedContainer<std::vector<int>>, std::set<int>,
+    std::multiset<int>, UnorderedSequence<int>,
+    TypeErasedContainer<UnorderedSequence<int>>, std::unordered_set<int>,
+    std::unordered_multiset<int>, absl::flat_hash_set<int>,
+    absl::node_hash_set<int>, absl::btree_set<int>>;
+INSTANTIATE_TYPED_TEST_SUITE_P(My, HashValueSequenceTest, IntSequenceTypes);
+
+template <typename T>
+class HashValueNestedSequenceTest : public testing::Test {};
+TYPED_TEST_SUITE_P(HashValueNestedSequenceTest);
+
+TYPED_TEST_P(HashValueNestedSequenceTest, BasicUsage) {
+  using T = TypeParam;
+  using V = typename T::value_type;
+  std::vector<T> exemplars = {
+      // empty case
+      T{},
+      // sets of empty sets
+      T{V{}}, T{V{}, V{}}, T{V{}, V{}, V{}},
+      // multisets of different values
+      T{V{1}}, T{V{1, 1}, V{1, 1}}, T{V{1, 1, 1}, V{1, 1, 1}, V{1, 1, 1}},
+      // various orderings of same nested sets
+      T{V{}, V{1, 2}}, T{V{}, V{2, 1}}, T{V{1, 2}, V{}}, T{V{2, 1}, V{}},
+      // various orderings of various nested sets, case 2
+      T{V{1, 2}, V{3, 4}}, T{V{1, 2}, V{4, 3}}, T{V{1, 3}, V{2, 4}},
+      T{V{1, 3}, V{4, 2}}, T{V{1, 4}, V{2, 3}}, T{V{1, 4}, V{3, 2}},
+      T{V{2, 3}, V{1, 4}}, T{V{2, 3}, V{4, 1}}, T{V{2, 4}, V{1, 3}},
+      T{V{2, 4}, V{3, 1}}, T{V{3, 4}, V{1, 2}}, T{V{3, 4}, V{2, 1}}};
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(exemplars));
+}
+
+REGISTER_TYPED_TEST_SUITE_P(HashValueNestedSequenceTest, BasicUsage);
+template <typename T>
+using TypeErasedSet = TypeErasedContainer<UnorderedSequence<T>>;
+
+using NestedIntSequenceTypes = testing::Types<
+    std::vector<std::vector<int>>, std::vector<UnorderedSequence<int>>,
+    std::vector<TypeErasedSet<int>>, UnorderedSequence<std::vector<int>>,
+    UnorderedSequence<UnorderedSequence<int>>,
+    UnorderedSequence<TypeErasedSet<int>>, TypeErasedSet<std::vector<int>>,
+    TypeErasedSet<UnorderedSequence<int>>, TypeErasedSet<TypeErasedSet<int>>>;
+INSTANTIATE_TYPED_TEST_SUITE_P(My, HashValueNestedSequenceTest,
+                               NestedIntSequenceTypes);
+
+template <typename T>
+class HashValueAssociativeMapTest : public testing::Test {};
+TYPED_TEST_SUITE_P(HashValueAssociativeMapTest);
+
+TYPED_TEST_P(HashValueAssociativeMapTest, BasicUsage) {
+  using M = TypeParam;
+  using V = typename M::value_type;
+  std::vector<M> exemplars{M{},
+                           M{V{0, "foo"}},
+                           M{V{1, "foo"}},
+                           M{V{0, "bar"}},
+                           M{V{1, "bar"}},
+                           M{V{0, "foo"}, V{42, "bar"}},
+                           M{V{42, "bar"}, V{0, "foo"}},
+                           M{V{1, "foo"}, V{42, "bar"}},
+                           M{V{1, "foo"}, V{43, "bar"}},
+                           M{V{1, "foo"}, V{43, "baz"}}};
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(exemplars));
+}
+
+REGISTER_TYPED_TEST_SUITE_P(HashValueAssociativeMapTest, BasicUsage);
+using AssociativeMapTypes = testing::Types<
+    std::map<int, std::string>, std::unordered_map<int, std::string>,
+    absl::flat_hash_map<int, std::string>,
+    absl::node_hash_map<int, std::string>, absl::btree_map<int, std::string>,
+    UnorderedSequence<std::pair<const int, std::string>>>;
+INSTANTIATE_TYPED_TEST_SUITE_P(My, HashValueAssociativeMapTest,
+                               AssociativeMapTypes);
+
+template <typename T>
+class HashValueAssociativeMultimapTest : public testing::Test {};
+TYPED_TEST_SUITE_P(HashValueAssociativeMultimapTest);
+
+TYPED_TEST_P(HashValueAssociativeMultimapTest, BasicUsage) {
+  using MM = TypeParam;
+  using V = typename MM::value_type;
+  std::vector<MM> exemplars{MM{},
+                            MM{V{0, "foo"}},
+                            MM{V{1, "foo"}},
+                            MM{V{0, "bar"}},
+                            MM{V{1, "bar"}},
+                            MM{V{0, "foo"}, V{0, "bar"}},
+                            MM{V{0, "bar"}, V{0, "foo"}},
+                            MM{V{0, "foo"}, V{42, "bar"}},
+                            MM{V{1, "foo"}, V{42, "bar"}},
+                            MM{V{1, "foo"}, V{1, "foo"}, V{43, "bar"}},
+                            MM{V{1, "foo"}, V{43, "bar"}, V{1, "foo"}},
+                            MM{V{1, "foo"}, V{43, "baz"}}};
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(exemplars));
+}
+
+REGISTER_TYPED_TEST_SUITE_P(HashValueAssociativeMultimapTest, BasicUsage);
+using AssociativeMultimapTypes =
+    testing::Types<std::multimap<int, std::string>,
+                   std::unordered_multimap<int, std::string>>;
+INSTANTIATE_TYPED_TEST_SUITE_P(My, HashValueAssociativeMultimapTest,
+                               AssociativeMultimapTypes);
+
+}  // namespace
diff --git a/absl/hash/hash_test.cc b/absl/hash/hash_test.cc
index 5b556180..a0e2e4a7 100644
--- a/absl/hash/hash_test.cc
+++ b/absl/hash/hash_test.cc
@@ -17,6 +17,7 @@
 #include <algorithm>
 #include <array>
 #include <bitset>
+#include <cstdint>
 #include <cstring>
 #include <deque>
 #include <forward_list>
@@ -47,59 +48,21 @@
 #include "absl/container/node_hash_map.h"
 #include "absl/container/node_hash_set.h"
 #include "absl/hash/hash_testing.h"
+#include "absl/hash/internal/hash_test.h"
 #include "absl/hash/internal/spy_hash_state.h"
 #include "absl/meta/type_traits.h"
 #include "absl/numeric/int128.h"
 #include "absl/strings/cord_test_helpers.h"
 
-namespace {
-
-// Utility wrapper of T for the purposes of testing the `AbslHash` type erasure
-// mechanism.  `TypeErasedValue<T>` can be constructed with a `T`, and can
-// be compared and hashed.  However, all hashing goes through the hashing
-// type-erasure framework.
-template <typename T>
-class TypeErasedValue {
- public:
-  TypeErasedValue() = default;
-  TypeErasedValue(const TypeErasedValue&) = default;
-  TypeErasedValue(TypeErasedValue&&) = default;
-  explicit TypeErasedValue(const T& n) : n_(n) {}
-
-  template <typename H>
-  friend H AbslHashValue(H hash_state, const TypeErasedValue& v) {
-    v.HashValue(absl::HashState::Create(&hash_state));
-    return hash_state;
-  }
-
-  void HashValue(absl::HashState state) const {
-    absl::HashState::combine(std::move(state), n_);
-  }
+#ifdef ABSL_HAVE_STD_STRING_VIEW
+#include <string_view>
+#endif
 
-  bool operator==(const TypeErasedValue& rhs) const { return n_ == rhs.n_; }
-  bool operator!=(const TypeErasedValue& rhs) const { return !(*this == rhs); }
+namespace {
 
- private:
-  T n_;
-};
-
-// A TypeErasedValue refinement, for containers.  It exposes the wrapped
-// `value_type` and is constructible from an initializer list.
-template <typename T>
-class TypeErasedContainer : public TypeErasedValue<T> {
- public:
-  using value_type = typename T::value_type;
-  TypeErasedContainer() = default;
-  TypeErasedContainer(const TypeErasedContainer&) = default;
-  TypeErasedContainer(TypeErasedContainer&&) = default;
-  explicit TypeErasedContainer(const T& n) : TypeErasedValue<T>(n) {}
-  TypeErasedContainer(std::initializer_list<value_type> init_list)
-      : TypeErasedContainer(T(init_list.begin(), init_list.end())) {}
-  // one-argument constructor of value type T, to appease older toolchains that
-  // get confused by one-element initializer lists in some contexts
-  explicit TypeErasedContainer(const value_type& v)
-      : TypeErasedContainer(T(&v, &v + 1)) {}
-};
+using ::absl::hash_test_internal::is_hashable;
+using ::absl::hash_test_internal::TypeErasedContainer;
+using ::absl::hash_test_internal::TypeErasedValue;
 
 template <typename T>
 using TypeErasedVector = TypeErasedContainer<std::vector<T>>;
@@ -117,11 +80,6 @@ SpyHashState SpyHash(const T& value) {
   return SpyHashState::combine(SpyHashState(), value);
 }
 
-// Helper trait to verify if T is hashable. We use absl::Hash's poison status to
-// detect it.
-template <typename T>
-using is_hashable = std::is_default_constructible<absl::Hash<T>>;
-
 TYPED_TEST_P(HashValueIntTest, BasicUsage) {
   EXPECT_TRUE((is_hashable<TypeParam>::value));
 
@@ -487,6 +445,47 @@ TEST(HashValueTest, U32String) {
       std::u32string(U"Iñtërnâtiônàlizætiøn"))));
 }
 
+TEST(HashValueTest, WStringView) {
+#ifndef ABSL_HAVE_STD_STRING_VIEW
+  GTEST_SKIP();
+#else
+  EXPECT_TRUE((is_hashable<std::wstring_view>::value));
+
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(std::make_tuple(
+      std::wstring_view(), std::wstring_view(L"ABC"), std::wstring_view(L"ABC"),
+      std::wstring_view(L"Some other different string_view"),
+      std::wstring_view(L"Iñtërnâtiônàlizætiøn"))));
+#endif
+}
+
+TEST(HashValueTest, U16StringView) {
+#ifndef ABSL_HAVE_STD_STRING_VIEW
+  GTEST_SKIP();
+#else
+  EXPECT_TRUE((is_hashable<std::u16string_view>::value));
+
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(
+      std::make_tuple(std::u16string_view(), std::u16string_view(u"ABC"),
+                      std::u16string_view(u"ABC"),
+                      std::u16string_view(u"Some other different string_view"),
+                      std::u16string_view(u"Iñtërnâtiônàlizætiøn"))));
+#endif
+}
+
+TEST(HashValueTest, U32StringView) {
+#ifndef ABSL_HAVE_STD_STRING_VIEW
+  GTEST_SKIP();
+#else
+  EXPECT_TRUE((is_hashable<std::u32string_view>::value));
+
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(
+      std::make_tuple(std::u32string_view(), std::u32string_view(U"ABC"),
+                      std::u32string_view(U"ABC"),
+                      std::u32string_view(U"Some other different string_view"),
+                      std::u32string_view(U"Iñtërnâtiônàlizætiøn"))));
+#endif
+}
+
 TEST(HashValueTest, StdArray) {
   EXPECT_TRUE((is_hashable<std::array<int, 3>>::value));
 
@@ -520,121 +519,6 @@ TEST(HashValueTest, StdBitset) {
        std::bitset<kNumBits>(bit_strings[5].c_str())}));
 }  // namespace
 
-// Dummy type with unordered equality and hashing semantics.  This preserves
-// input order internally, and is used below to ensure we get test coverage
-// for equal sequences with different iteraton orders.
-template <typename T>
-class UnorderedSequence {
- public:
-  UnorderedSequence() = default;
-  template <typename TT>
-  UnorderedSequence(std::initializer_list<TT> l)
-      : values_(l.begin(), l.end()) {}
-  template <typename ForwardIterator,
-            typename std::enable_if<!std::is_integral<ForwardIterator>::value,
-                                    bool>::type = true>
-  UnorderedSequence(ForwardIterator begin, ForwardIterator end)
-      : values_(begin, end) {}
-  // one-argument constructor of value type T, to appease older toolchains that
-  // get confused by one-element initializer lists in some contexts
-  explicit UnorderedSequence(const T& v) : values_(&v, &v + 1) {}
-
-  using value_type = T;
-
-  size_t size() const { return values_.size(); }
-  typename std::vector<T>::const_iterator begin() const {
-    return values_.begin();
-  }
-  typename std::vector<T>::const_iterator end() const { return values_.end(); }
-
-  friend bool operator==(const UnorderedSequence& lhs,
-                         const UnorderedSequence& rhs) {
-    return lhs.size() == rhs.size() &&
-           std::is_permutation(lhs.begin(), lhs.end(), rhs.begin());
-  }
-  friend bool operator!=(const UnorderedSequence& lhs,
-                         const UnorderedSequence& rhs) {
-    return !(lhs == rhs);
-  }
-  template <typename H>
-  friend H AbslHashValue(H h, const UnorderedSequence& u) {
-    return H::combine(H::combine_unordered(std::move(h), u.begin(), u.end()),
-                      u.size());
-  }
-
- private:
-  std::vector<T> values_;
-};
-
-template <typename T>
-class HashValueSequenceTest : public testing::Test {
-};
-TYPED_TEST_SUITE_P(HashValueSequenceTest);
-
-TYPED_TEST_P(HashValueSequenceTest, BasicUsage) {
-  EXPECT_TRUE((is_hashable<TypeParam>::value));
-
-  using IntType = typename TypeParam::value_type;
-  auto a = static_cast<IntType>(0);
-  auto b = static_cast<IntType>(23);
-  auto c = static_cast<IntType>(42);
-
-  std::vector<TypeParam> exemplars = {
-      TypeParam(),        TypeParam(),        TypeParam{a, b, c},
-      TypeParam{a, c, b}, TypeParam{c, a, b}, TypeParam{a},
-      TypeParam{a, a},    TypeParam{a, a, a}, TypeParam{a, a, b},
-      TypeParam{a, b, a}, TypeParam{b, a, a}, TypeParam{a, b},
-      TypeParam{b, c}};
-  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(exemplars));
-}
-
-REGISTER_TYPED_TEST_SUITE_P(HashValueSequenceTest, BasicUsage);
-using IntSequenceTypes = testing::Types<
-    std::deque<int>, std::forward_list<int>, std::list<int>, std::vector<int>,
-    std::vector<bool>, TypeErasedContainer<std::vector<int>>, std::set<int>,
-    std::multiset<int>, UnorderedSequence<int>,
-    TypeErasedContainer<UnorderedSequence<int>>, std::unordered_set<int>,
-    std::unordered_multiset<int>, absl::flat_hash_set<int>,
-    absl::node_hash_set<int>, absl::btree_set<int>>;
-INSTANTIATE_TYPED_TEST_SUITE_P(My, HashValueSequenceTest, IntSequenceTypes);
-
-template <typename T>
-class HashValueNestedSequenceTest : public testing::Test {};
-TYPED_TEST_SUITE_P(HashValueNestedSequenceTest);
-
-TYPED_TEST_P(HashValueNestedSequenceTest, BasicUsage) {
-  using T = TypeParam;
-  using V = typename T::value_type;
-  std::vector<T> exemplars = {
-      // empty case
-      T{},
-      // sets of empty sets
-      T{V{}}, T{V{}, V{}}, T{V{}, V{}, V{}},
-      // multisets of different values
-      T{V{1}}, T{V{1, 1}, V{1, 1}}, T{V{1, 1, 1}, V{1, 1, 1}, V{1, 1, 1}},
-      // various orderings of same nested sets
-      T{V{}, V{1, 2}}, T{V{}, V{2, 1}}, T{V{1, 2}, V{}}, T{V{2, 1}, V{}},
-      // various orderings of various nested sets, case 2
-      T{V{1, 2}, V{3, 4}}, T{V{1, 2}, V{4, 3}}, T{V{1, 3}, V{2, 4}},
-      T{V{1, 3}, V{4, 2}}, T{V{1, 4}, V{2, 3}}, T{V{1, 4}, V{3, 2}},
-      T{V{2, 3}, V{1, 4}}, T{V{2, 3}, V{4, 1}}, T{V{2, 4}, V{1, 3}},
-      T{V{2, 4}, V{3, 1}}, T{V{3, 4}, V{1, 2}}, T{V{3, 4}, V{2, 1}}};
-  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(exemplars));
-}
-
-REGISTER_TYPED_TEST_SUITE_P(HashValueNestedSequenceTest, BasicUsage);
-template <typename T>
-using TypeErasedSet = TypeErasedContainer<UnorderedSequence<T>>;
-
-using NestedIntSequenceTypes = testing::Types<
-    std::vector<std::vector<int>>, std::vector<UnorderedSequence<int>>,
-    std::vector<TypeErasedSet<int>>, UnorderedSequence<std::vector<int>>,
-    UnorderedSequence<UnorderedSequence<int>>,
-    UnorderedSequence<TypeErasedSet<int>>, TypeErasedSet<std::vector<int>>,
-    TypeErasedSet<UnorderedSequence<int>>, TypeErasedSet<TypeErasedSet<int>>>;
-INSTANTIATE_TYPED_TEST_SUITE_P(My, HashValueNestedSequenceTest,
-                              NestedIntSequenceTypes);
-
 // Private type that only supports AbslHashValue to make sure our chosen hash
 // implementation is recursive within absl::Hash.
 // It uses std::abs() on the value to provide different bitwise representations
@@ -793,64 +677,6 @@ TEST(HashValueTest, Variant) {
 #endif
 }
 
-template <typename T>
-class HashValueAssociativeMapTest : public testing::Test {};
-TYPED_TEST_SUITE_P(HashValueAssociativeMapTest);
-
-TYPED_TEST_P(HashValueAssociativeMapTest, BasicUsage) {
-  using M = TypeParam;
-  using V = typename M::value_type;
-  std::vector<M> exemplars{M{},
-                           M{V{0, "foo"}},
-                           M{V{1, "foo"}},
-                           M{V{0, "bar"}},
-                           M{V{1, "bar"}},
-                           M{V{0, "foo"}, V{42, "bar"}},
-                           M{V{42, "bar"}, V{0, "foo"}},
-                           M{V{1, "foo"}, V{42, "bar"}},
-                           M{V{1, "foo"}, V{43, "bar"}},
-                           M{V{1, "foo"}, V{43, "baz"}}};
-  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(exemplars));
-}
-
-REGISTER_TYPED_TEST_SUITE_P(HashValueAssociativeMapTest, BasicUsage);
-using AssociativeMapTypes = testing::Types<
-    std::map<int, std::string>, std::unordered_map<int, std::string>,
-    absl::flat_hash_map<int, std::string>,
-    absl::node_hash_map<int, std::string>, absl::btree_map<int, std::string>,
-    UnorderedSequence<std::pair<const int, std::string>>>;
-INSTANTIATE_TYPED_TEST_SUITE_P(My, HashValueAssociativeMapTest,
-                              AssociativeMapTypes);
-
-template <typename T>
-class HashValueAssociativeMultimapTest : public testing::Test {};
-TYPED_TEST_SUITE_P(HashValueAssociativeMultimapTest);
-
-TYPED_TEST_P(HashValueAssociativeMultimapTest, BasicUsage) {
-  using MM = TypeParam;
-  using V = typename MM::value_type;
-  std::vector<MM> exemplars{MM{},
-                            MM{V{0, "foo"}},
-                            MM{V{1, "foo"}},
-                            MM{V{0, "bar"}},
-                            MM{V{1, "bar"}},
-                            MM{V{0, "foo"}, V{0, "bar"}},
-                            MM{V{0, "bar"}, V{0, "foo"}},
-                            MM{V{0, "foo"}, V{42, "bar"}},
-                            MM{V{1, "foo"}, V{42, "bar"}},
-                            MM{V{1, "foo"}, V{1, "foo"}, V{43, "bar"}},
-                            MM{V{1, "foo"}, V{43, "bar"}, V{1, "foo"}},
-                            MM{V{1, "foo"}, V{43, "baz"}}};
-  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(exemplars));
-}
-
-REGISTER_TYPED_TEST_SUITE_P(HashValueAssociativeMultimapTest, BasicUsage);
-using AssociativeMultimapTypes =
-    testing::Types<std::multimap<int, std::string>,
-                   std::unordered_multimap<int, std::string>>;
-INSTANTIATE_TYPED_TEST_SUITE_P(My, HashValueAssociativeMultimapTest,
-                              AssociativeMultimapTypes);
-
 TEST(HashValueTest, ReferenceWrapper) {
   EXPECT_TRUE(is_hashable<std::reference_wrapper<Private>>::value);
 
@@ -1241,14 +1067,24 @@ TEST(HashTest, DoesNotUseImplicitConversionsToBool) {
 
 TEST(HashOf, MatchesHashForSingleArgument) {
   std::string s = "forty two";
-  int i = 42;
   double d = 42.0;
   std::tuple<int, int> t{4, 2};
+  int i = 42;
+  int neg_i = -42;
+  int16_t i16 = 42;
+  int16_t neg_i16 = -42;
+  int8_t i8 = 42;
+  int8_t neg_i8 = -42;
 
   EXPECT_EQ(absl::HashOf(s), absl::Hash<std::string>{}(s));
-  EXPECT_EQ(absl::HashOf(i), absl::Hash<int>{}(i));
   EXPECT_EQ(absl::HashOf(d), absl::Hash<double>{}(d));
   EXPECT_EQ(absl::HashOf(t), (absl::Hash<std::tuple<int, int>>{}(t)));
+  EXPECT_EQ(absl::HashOf(i), absl::Hash<int>{}(i));
+  EXPECT_EQ(absl::HashOf(neg_i), absl::Hash<int>{}(neg_i));
+  EXPECT_EQ(absl::HashOf(i16), absl::Hash<int16_t>{}(i16));
+  EXPECT_EQ(absl::HashOf(neg_i16), absl::Hash<int16_t>{}(neg_i16));
+  EXPECT_EQ(absl::HashOf(i8), absl::Hash<int8_t>{}(i8));
+  EXPECT_EQ(absl::HashOf(neg_i8), absl::Hash<int8_t>{}(neg_i8));
 }
 
 TEST(HashOf, MatchesHashOfTupleForMultipleArguments) {
diff --git a/absl/hash/internal/hash.h b/absl/hash/internal/hash.h
index ccf4cc1a..ef3f3664 100644
--- a/absl/hash/internal/hash.h
+++ b/absl/hash/internal/hash.h
@@ -56,6 +56,10 @@
 #include "absl/types/variant.h"
 #include "absl/utility/utility.h"
 
+#ifdef ABSL_HAVE_STD_STRING_VIEW
+#include <string_view>
+#endif
+
 namespace absl {
 ABSL_NAMESPACE_BEGIN
 
@@ -424,7 +428,7 @@ H AbslHashValue(H hash_state, std::nullptr_t) {
 
 // AbslHashValue() for hashing pointers-to-member
 template <typename H, typename T, typename C>
-H AbslHashValue(H hash_state, T C::* ptr) {
+H AbslHashValue(H hash_state, T C::*ptr) {
   auto salient_ptm_size = [](std::size_t n) -> std::size_t {
 #if defined(_MSC_VER)
     // Pointers-to-member-function on MSVC consist of one pointer plus 0, 1, 2,
@@ -442,8 +446,8 @@ H AbslHashValue(H hash_state, T C::* ptr) {
       return n == 24 ? 20 : n == 16 ? 12 : n;
     }
 #else
-    // On other platforms, we assume that pointers-to-members do not have
-    // padding.
+  // On other platforms, we assume that pointers-to-members do not have
+  // padding.
 #ifdef __cpp_lib_has_unique_object_representations
     static_assert(std::has_unique_object_representations<T C::*>::value);
 #endif  // __cpp_lib_has_unique_object_representations
@@ -516,14 +520,15 @@ H AbslHashValue(H hash_state, const std::shared_ptr<T>& ptr) {
 // the same character sequence. These types are:
 //
 //  - `absl::Cord`
-//  - `std::string` (and std::basic_string<char, std::char_traits<char>, A> for
-//      any allocator A)
-//  - `absl::string_view` and `std::string_view`
+//  - `std::string` (and std::basic_string<T, std::char_traits<T>, A> for
+//      any allocator A and any T in {char, wchar_t, char16_t, char32_t})
+//  - `absl::string_view`, `std::string_view`, `std::wstring_view`,
+//    `std::u16string_view`, and `std::u32_string_view`.
 //
-// For simplicity, we currently support only `char` strings. This support may
-// be broadened, if necessary, but with some caution - this overload would
-// misbehave in cases where the traits' `eq()` member isn't equivalent to `==`
-// on the underlying character type.
+// For simplicity, we currently support only strings built on `char`, `wchar_t`,
+// `char16_t`, or `char32_t`. This support may be broadened, if necessary, but
+// with some caution - this overload would misbehave in cases where the traits'
+// `eq()` member isn't equivalent to `==` on the underlying character type.
 template <typename H>
 H AbslHashValue(H hash_state, absl::string_view str) {
   return H::combine(
@@ -544,6 +549,21 @@ H AbslHashValue(
       str.size());
 }
 
+#ifdef ABSL_HAVE_STD_STRING_VIEW
+
+// Support std::wstring_view, std::u16string_view and std::u32string_view.
+template <typename Char, typename H,
+          typename = absl::enable_if_t<std::is_same<Char, wchar_t>::value ||
+                                       std::is_same<Char, char16_t>::value ||
+                                       std::is_same<Char, char32_t>::value>>
+H AbslHashValue(H hash_state, std::basic_string_view<Char> str) {
+  return H::combine(
+      H::combine_contiguous(std::move(hash_state), str.data(), str.size()),
+      str.size());
+}
+
+#endif  // ABSL_HAVE_STD_STRING_VIEW
+
 // -----------------------------------------------------------------------------
 // AbslHashValue for Sequence Containers
 // -----------------------------------------------------------------------------
@@ -935,8 +955,8 @@ class ABSL_DLL MixingHashState : public HashStateBase<MixingHashState> {
 #endif  // ABSL_HAVE_INTRINSIC_INT128
 
   static constexpr uint64_t kMul =
-      sizeof(size_t) == 4 ? uint64_t{0xcc9e2d51}
-                          : uint64_t{0x9ddfea08eb382d69};
+  sizeof(size_t) == 4 ? uint64_t{0xcc9e2d51}
+                      : uint64_t{0x9ddfea08eb382d69};
 
   template <typename T>
   using IntegralFastPath =
@@ -969,7 +989,8 @@ class ABSL_DLL MixingHashState : public HashStateBase<MixingHashState> {
   // The result should be the same as running the whole algorithm, but faster.
   template <typename T, absl::enable_if_t<IntegralFastPath<T>::value, int> = 0>
   static size_t hash(T value) {
-    return static_cast<size_t>(Mix(Seed(), static_cast<uint64_t>(value)));
+    return static_cast<size_t>(
+        Mix(Seed(), static_cast<std::make_unsigned_t<T>>(value)));
   }
 
   // Overload of MixingHashState::hash()
@@ -1073,6 +1094,7 @@ class ABSL_DLL MixingHashState : public HashStateBase<MixingHashState> {
 
   // Reads 1 to 3 bytes from p. Zero pads to fill uint32_t.
   static uint32_t Read1To3(const unsigned char* p, size_t len) {
+    // The trick used by this implementation is to avoid branches if possible.
     unsigned char mem0 = p[0];
     unsigned char mem1 = p[len / 2];
     unsigned char mem2 = p[len - 1];
@@ -1082,7 +1104,7 @@ class ABSL_DLL MixingHashState : public HashStateBase<MixingHashState> {
     unsigned char significant0 = mem0;
 #else
     unsigned char significant2 = mem0;
-    unsigned char significant1 = mem1;
+    unsigned char significant1 = len == 2 ? mem0 : mem1;
     unsigned char significant0 = mem2;
 #endif
     return static_cast<uint32_t>(significant0 |                     //
@@ -1135,7 +1157,8 @@ class ABSL_DLL MixingHashState : public HashStateBase<MixingHashState> {
   // probably per-build and not per-process.
   ABSL_ATTRIBUTE_ALWAYS_INLINE static uint64_t Seed() {
 #if (!defined(__clang__) || __clang_major__ > 11) && \
-    !defined(__apple_build_version__)
+    (!defined(__apple_build_version__) ||            \
+     __apple_build_version__ >= 19558921)  // Xcode 12
     return static_cast<uint64_t>(reinterpret_cast<uintptr_t>(&kSeed));
 #else
     // Workaround the absence of
diff --git a/absl/hash/internal/hash_test.h b/absl/hash/internal/hash_test.h
new file mode 100644
index 00000000..9963dc0b
--- /dev/null
+++ b/absl/hash/internal/hash_test.h
@@ -0,0 +1,87 @@
+// Copyright 2023 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Common code shared between absl/hash/hash_test.cc and
+// absl/hash/hash_instantiated_test.cc.
+
+#ifndef ABSL_HASH_INTERNAL_HASH_TEST_H_
+#define ABSL_HASH_INTERNAL_HASH_TEST_H_
+
+#include <type_traits>
+#include <utility>
+
+#include "absl/base/config.h"
+#include "absl/hash/hash.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace hash_test_internal {
+
+// Utility wrapper of T for the purposes of testing the `AbslHash` type erasure
+// mechanism.  `TypeErasedValue<T>` can be constructed with a `T`, and can
+// be compared and hashed.  However, all hashing goes through the hashing
+// type-erasure framework.
+template <typename T>
+class TypeErasedValue {
+ public:
+  TypeErasedValue() = default;
+  TypeErasedValue(const TypeErasedValue&) = default;
+  TypeErasedValue(TypeErasedValue&&) = default;
+  explicit TypeErasedValue(const T& n) : n_(n) {}
+
+  template <typename H>
+  friend H AbslHashValue(H hash_state, const TypeErasedValue& v) {
+    v.HashValue(absl::HashState::Create(&hash_state));
+    return hash_state;
+  }
+
+  void HashValue(absl::HashState state) const {
+    absl::HashState::combine(std::move(state), n_);
+  }
+
+  bool operator==(const TypeErasedValue& rhs) const { return n_ == rhs.n_; }
+  bool operator!=(const TypeErasedValue& rhs) const { return !(*this == rhs); }
+
+ private:
+  T n_;
+};
+
+// A TypeErasedValue refinement, for containers.  It exposes the wrapped
+// `value_type` and is constructible from an initializer list.
+template <typename T>
+class TypeErasedContainer : public TypeErasedValue<T> {
+ public:
+  using value_type = typename T::value_type;
+  TypeErasedContainer() = default;
+  TypeErasedContainer(const TypeErasedContainer&) = default;
+  TypeErasedContainer(TypeErasedContainer&&) = default;
+  explicit TypeErasedContainer(const T& n) : TypeErasedValue<T>(n) {}
+  TypeErasedContainer(std::initializer_list<value_type> init_list)
+      : TypeErasedContainer(T(init_list.begin(), init_list.end())) {}
+  // one-argument constructor of value type T, to appease older toolchains that
+  // get confused by one-element initializer lists in some contexts
+  explicit TypeErasedContainer(const value_type& v)
+      : TypeErasedContainer(T(&v, &v + 1)) {}
+};
+
+// Helper trait to verify if T is hashable. We use absl::Hash's poison status to
+// detect it.
+template <typename T>
+using is_hashable = std::is_default_constructible<absl::Hash<T>>;
+
+}  // namespace hash_test_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_HASH_INTERNAL_HASH_TEST_H_
diff --git a/absl/hash/internal/low_level_hash.cc b/absl/hash/internal/low_level_hash.cc
index c917457a..b5db0b89 100644
--- a/absl/hash/internal/low_level_hash.cc
+++ b/absl/hash/internal/low_level_hash.cc
@@ -15,6 +15,7 @@
 #include "absl/hash/internal/low_level_hash.h"
 
 #include "absl/base/internal/unaligned_access.h"
+#include "absl/base/prefetch.h"
 #include "absl/numeric/int128.h"
 
 namespace absl {
@@ -29,6 +30,8 @@ static uint64_t Mix(uint64_t v0, uint64_t v1) {
 
 uint64_t LowLevelHash(const void* data, size_t len, uint64_t seed,
                       const uint64_t salt[5]) {
+  // Prefetch the cacheline that data resides in.
+  PrefetchToLocalCache(data);
   const uint8_t* ptr = static_cast<const uint8_t*>(data);
   uint64_t starting_length = static_cast<uint64_t>(len);
   uint64_t current_state = seed ^ salt[0];
@@ -40,6 +43,9 @@ uint64_t LowLevelHash(const void* data, size_t len, uint64_t seed,
     uint64_t duplicated_state = current_state;
 
     do {
+      // Always prefetch the next cacheline.
+      PrefetchToLocalCache(ptr + ABSL_CACHELINE_SIZE);
+
       uint64_t a = absl::base_internal::UnalignedLoad64(ptr);
       uint64_t b = absl::base_internal::UnalignedLoad64(ptr + 8);
       uint64_t c = absl::base_internal::UnalignedLoad64(ptr + 16);
diff --git a/absl/log/BUILD.bazel b/absl/log/BUILD.bazel
index e9e411ff..e1410637 100644
--- a/absl/log/BUILD.bazel
+++ b/absl/log/BUILD.bazel
@@ -109,6 +109,7 @@ cc_library(
         "//absl/base:config",
         "//absl/base:core_headers",
         "//absl/base:log_severity",
+        "//absl/base:raw_logging_internal",
         "//absl/hash",
         "//absl/strings",
     ],
@@ -288,7 +289,7 @@ cc_library(
         "no_test_ios",
         "no_test_wasm",
     ],
-    textual_hdrs = ["check_test_impl.h"],
+    textual_hdrs = ["check_test_impl.inc"],
     visibility = ["//visibility:private"],
     deps = [
         "//absl/base:config",
@@ -372,7 +373,7 @@ cc_library(
     testonly = True,
     copts = ABSL_TEST_COPTS,
     linkopts = ABSL_DEFAULT_LINKOPTS,
-    textual_hdrs = ["log_basic_test_impl.h"],
+    textual_hdrs = ["log_basic_test_impl.inc"],
     visibility = ["//visibility:private"],
     deps = [
         "//absl/base",
@@ -458,7 +459,6 @@ cc_test(
         ":log_sink_registry",
         ":scoped_mock_log",
         "//absl/base:core_headers",
-        "//absl/base:raw_logging_internal",
         "//absl/log/internal:test_actions",
         "//absl/log/internal:test_helpers",
         "//absl/log/internal:test_matchers",
@@ -546,6 +546,7 @@ cc_test(
     deps = [
         ":check",
         ":log",
+        "//absl/base:log_severity",
         "//absl/base:strerror",
         "//absl/flags:program_name",
         "//absl/log/internal:test_helpers",
diff --git a/absl/log/CMakeLists.txt b/absl/log/CMakeLists.txt
index fb1b59f5..9320ce59 100644
--- a/absl/log/CMakeLists.txt
+++ b/absl/log/CMakeLists.txt
@@ -1,4 +1,3 @@
-#
 # Copyright 2022 The Abseil Authors.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
@@ -501,6 +500,7 @@ absl_cc_library(
     absl::core_headers
     absl::hash
     absl::log_severity
+    absl::raw_logging_internal
     absl::strings
 )
 
@@ -678,7 +678,7 @@ absl_cc_test(
     absl_check_test
   SRCS
     "absl_check_test.cc"
-    "check_test_impl.h"
+    "check_test_impl.inc"
   COPTS
     ${ABSL_TEST_COPTS}
   LINKOPTS
@@ -698,7 +698,7 @@ absl_cc_test(
     absl_log_basic_test
   SRCS
     "log_basic_test.cc"
-    "log_basic_test_impl.h"
+    "log_basic_test_impl.inc"
   COPTS
     ${ABSL_TEST_COPTS}
   LINKOPTS
@@ -722,7 +722,7 @@ absl_cc_test(
     check_test
   SRCS
     "check_test.cc"
-    "check_test_impl.h"
+    "check_test_impl.inc"
   COPTS
     ${ABSL_TEST_COPTS}
   LINKOPTS
@@ -758,7 +758,7 @@ absl_cc_test(
     log_basic_test
   SRCS
     "log_basic_test.cc"
-    "log_basic_test_impl.h"
+    "log_basic_test_impl.inc"
   COPTS
     ${ABSL_TEST_COPTS}
   LINKOPTS
@@ -905,7 +905,6 @@ absl_cc_test(
     absl::log_sink
     absl::log_sink_registry
     absl::log_severity
-    absl::raw_logging_internal
     absl::scoped_mock_log
     absl::strings
     GTest::gtest_main
@@ -1014,6 +1013,7 @@ absl_cc_test(
     absl::flags_program_name
     absl::log
     absl::log_internal_test_helpers
+    absl::log_severity
     absl::strerror
     absl::strings
     absl::str_format
diff --git a/absl/log/absl_check.h b/absl/log/absl_check.h
index 14a2307f..1bb43bd3 100644
--- a/absl/log/absl_check.h
+++ b/absl/log/absl_check.h
@@ -37,69 +37,81 @@
 
 #include "absl/log/internal/check_impl.h"
 
-#define ABSL_CHECK(condition) ABSL_CHECK_IMPL((condition), #condition)
-#define ABSL_QCHECK(condition) ABSL_QCHECK_IMPL((condition), #condition)
-#define ABSL_PCHECK(condition) ABSL_PCHECK_IMPL((condition), #condition)
-#define ABSL_DCHECK(condition) ABSL_DCHECK_IMPL((condition), #condition)
+#define ABSL_CHECK(condition) \
+  ABSL_LOG_INTERNAL_CHECK_IMPL((condition), #condition)
+#define ABSL_QCHECK(condition) \
+  ABSL_LOG_INTERNAL_QCHECK_IMPL((condition), #condition)
+#define ABSL_PCHECK(condition) \
+  ABSL_LOG_INTERNAL_PCHECK_IMPL((condition), #condition)
+#define ABSL_DCHECK(condition) \
+  ABSL_LOG_INTERNAL_DCHECK_IMPL((condition), #condition)
 
 #define ABSL_CHECK_EQ(val1, val2) \
-  ABSL_CHECK_EQ_IMPL((val1), #val1, (val2), #val2)
+  ABSL_LOG_INTERNAL_CHECK_EQ_IMPL((val1), #val1, (val2), #val2)
 #define ABSL_CHECK_NE(val1, val2) \
-  ABSL_CHECK_NE_IMPL((val1), #val1, (val2), #val2)
+  ABSL_LOG_INTERNAL_CHECK_NE_IMPL((val1), #val1, (val2), #val2)
 #define ABSL_CHECK_LE(val1, val2) \
-  ABSL_CHECK_LE_IMPL((val1), #val1, (val2), #val2)
+  ABSL_LOG_INTERNAL_CHECK_LE_IMPL((val1), #val1, (val2), #val2)
 #define ABSL_CHECK_LT(val1, val2) \
-  ABSL_CHECK_LT_IMPL((val1), #val1, (val2), #val2)
+  ABSL_LOG_INTERNAL_CHECK_LT_IMPL((val1), #val1, (val2), #val2)
 #define ABSL_CHECK_GE(val1, val2) \
-  ABSL_CHECK_GE_IMPL((val1), #val1, (val2), #val2)
+  ABSL_LOG_INTERNAL_CHECK_GE_IMPL((val1), #val1, (val2), #val2)
 #define ABSL_CHECK_GT(val1, val2) \
-  ABSL_CHECK_GT_IMPL((val1), #val1, (val2), #val2)
+  ABSL_LOG_INTERNAL_CHECK_GT_IMPL((val1), #val1, (val2), #val2)
 #define ABSL_QCHECK_EQ(val1, val2) \
-  ABSL_QCHECK_EQ_IMPL((val1), #val1, (val2), #val2)
+  ABSL_LOG_INTERNAL_QCHECK_EQ_IMPL((val1), #val1, (val2), #val2)
 #define ABSL_QCHECK_NE(val1, val2) \
-  ABSL_QCHECK_NE_IMPL((val1), #val1, (val2), #val2)
+  ABSL_LOG_INTERNAL_QCHECK_NE_IMPL((val1), #val1, (val2), #val2)
 #define ABSL_QCHECK_LE(val1, val2) \
-  ABSL_QCHECK_LE_IMPL((val1), #val1, (val2), #val2)
+  ABSL_LOG_INTERNAL_QCHECK_LE_IMPL((val1), #val1, (val2), #val2)
 #define ABSL_QCHECK_LT(val1, val2) \
-  ABSL_QCHECK_LT_IMPL((val1), #val1, (val2), #val2)
+  ABSL_LOG_INTERNAL_QCHECK_LT_IMPL((val1), #val1, (val2), #val2)
 #define ABSL_QCHECK_GE(val1, val2) \
-  ABSL_QCHECK_GE_IMPL((val1), #val1, (val2), #val2)
+  ABSL_LOG_INTERNAL_QCHECK_GE_IMPL((val1), #val1, (val2), #val2)
 #define ABSL_QCHECK_GT(val1, val2) \
-  ABSL_QCHECK_GT_IMPL((val1), #val1, (val2), #val2)
+  ABSL_LOG_INTERNAL_QCHECK_GT_IMPL((val1), #val1, (val2), #val2)
 #define ABSL_DCHECK_EQ(val1, val2) \
-  ABSL_DCHECK_EQ_IMPL((val1), #val1, (val2), #val2)
+  ABSL_LOG_INTERNAL_DCHECK_EQ_IMPL((val1), #val1, (val2), #val2)
 #define ABSL_DCHECK_NE(val1, val2) \
-  ABSL_DCHECK_NE_IMPL((val1), #val1, (val2), #val2)
+  ABSL_LOG_INTERNAL_DCHECK_NE_IMPL((val1), #val1, (val2), #val2)
 #define ABSL_DCHECK_LE(val1, val2) \
-  ABSL_DCHECK_LE_IMPL((val1), #val1, (val2), #val2)
+  ABSL_LOG_INTERNAL_DCHECK_LE_IMPL((val1), #val1, (val2), #val2)
 #define ABSL_DCHECK_LT(val1, val2) \
-  ABSL_DCHECK_LT_IMPL((val1), #val1, (val2), #val2)
+  ABSL_LOG_INTERNAL_DCHECK_LT_IMPL((val1), #val1, (val2), #val2)
 #define ABSL_DCHECK_GE(val1, val2) \
-  ABSL_DCHECK_GE_IMPL((val1), #val1, (val2), #val2)
+  ABSL_LOG_INTERNAL_DCHECK_GE_IMPL((val1), #val1, (val2), #val2)
 #define ABSL_DCHECK_GT(val1, val2) \
-  ABSL_DCHECK_GT_IMPL((val1), #val1, (val2), #val2)
+  ABSL_LOG_INTERNAL_DCHECK_GT_IMPL((val1), #val1, (val2), #val2)
 
-#define ABSL_CHECK_OK(status) ABSL_CHECK_OK_IMPL((status), #status)
-#define ABSL_QCHECK_OK(status) ABSL_QCHECK_OK_IMPL((status), #status)
-#define ABSL_DCHECK_OK(status) ABSL_DCHECK_OK_IMPL((status), #status)
+#define ABSL_CHECK_OK(status) ABSL_LOG_INTERNAL_CHECK_OK_IMPL((status), #status)
+#define ABSL_QCHECK_OK(status) \
+  ABSL_LOG_INTERNAL_QCHECK_OK_IMPL((status), #status)
+#define ABSL_DCHECK_OK(status) \
+  ABSL_LOG_INTERNAL_DCHECK_OK_IMPL((status), #status)
 
-#define ABSL_CHECK_STREQ(s1, s2) ABSL_CHECK_STREQ_IMPL((s1), #s1, (s2), #s2)
-#define ABSL_CHECK_STRNE(s1, s2) ABSL_CHECK_STRNE_IMPL((s1), #s1, (s2), #s2)
+#define ABSL_CHECK_STREQ(s1, s2) \
+  ABSL_LOG_INTERNAL_CHECK_STREQ_IMPL((s1), #s1, (s2), #s2)
+#define ABSL_CHECK_STRNE(s1, s2) \
+  ABSL_LOG_INTERNAL_CHECK_STRNE_IMPL((s1), #s1, (s2), #s2)
 #define ABSL_CHECK_STRCASEEQ(s1, s2) \
-  ABSL_CHECK_STRCASEEQ_IMPL((s1), #s1, (s2), #s2)
+  ABSL_LOG_INTERNAL_CHECK_STRCASEEQ_IMPL((s1), #s1, (s2), #s2)
 #define ABSL_CHECK_STRCASENE(s1, s2) \
-  ABSL_CHECK_STRCASENE_IMPL((s1), #s1, (s2), #s2)
-#define ABSL_QCHECK_STREQ(s1, s2) ABSL_QCHECK_STREQ_IMPL((s1), #s1, (s2), #s2)
-#define ABSL_QCHECK_STRNE(s1, s2) ABSL_QCHECK_STRNE_IMPL((s1), #s1, (s2), #s2)
+  ABSL_LOG_INTERNAL_CHECK_STRCASENE_IMPL((s1), #s1, (s2), #s2)
+#define ABSL_QCHECK_STREQ(s1, s2) \
+  ABSL_LOG_INTERNAL_QCHECK_STREQ_IMPL((s1), #s1, (s2), #s2)
+#define ABSL_QCHECK_STRNE(s1, s2) \
+  ABSL_LOG_INTERNAL_QCHECK_STRNE_IMPL((s1), #s1, (s2), #s2)
 #define ABSL_QCHECK_STRCASEEQ(s1, s2) \
-  ABSL_QCHECK_STRCASEEQ_IMPL((s1), #s1, (s2), #s2)
+  ABSL_LOG_INTERNAL_QCHECK_STRCASEEQ_IMPL((s1), #s1, (s2), #s2)
 #define ABSL_QCHECK_STRCASENE(s1, s2) \
-  ABSL_QCHECK_STRCASENE_IMPL((s1), #s1, (s2), #s2)
-#define ABSL_DCHECK_STREQ(s1, s2) ABSL_DCHECK_STREQ_IMPL((s1), #s1, (s2), #s2)
-#define ABSL_DCHECK_STRNE(s1, s2) ABSL_DCHECK_STRNE_IMPL((s1), #s1, (s2), #s2)
+  ABSL_LOG_INTERNAL_QCHECK_STRCASENE_IMPL((s1), #s1, (s2), #s2)
+#define ABSL_DCHECK_STREQ(s1, s2) \
+  ABSL_LOG_INTERNAL_DCHECK_STREQ_IMPL((s1), #s1, (s2), #s2)
+#define ABSL_DCHECK_STRNE(s1, s2) \
+  ABSL_LOG_INTERNAL_DCHECK_STRNE_IMPL((s1), #s1, (s2), #s2)
 #define ABSL_DCHECK_STRCASEEQ(s1, s2) \
-  ABSL_DCHECK_STRCASEEQ_IMPL((s1), #s1, (s2), #s2)
+  ABSL_LOG_INTERNAL_DCHECK_STRCASEEQ_IMPL((s1), #s1, (s2), #s2)
 #define ABSL_DCHECK_STRCASENE(s1, s2) \
-  ABSL_DCHECK_STRCASENE_IMPL((s1), #s1, (s2), #s2)
+  ABSL_LOG_INTERNAL_DCHECK_STRCASENE_IMPL((s1), #s1, (s2), #s2)
 
 #endif  // ABSL_LOG_ABSL_CHECK_H_
diff --git a/absl/log/absl_check_test.cc b/absl/log/absl_check_test.cc
index 8ddacdb1..d84940fa 100644
--- a/absl/log/absl_check_test.cc
+++ b/absl/log/absl_check_test.cc
@@ -55,4 +55,4 @@
 #define ABSL_TEST_QCHECK_STRCASENE ABSL_QCHECK_STRCASENE
 
 #include "gtest/gtest.h"
-#include "absl/log/check_test_impl.h"
+#include "absl/log/check_test_impl.inc"
diff --git a/absl/log/absl_log.h b/absl/log/absl_log.h
index 1c6cf263..0517760b 100644
--- a/absl/log/absl_log.h
+++ b/absl/log/absl_log.h
@@ -35,60 +35,69 @@
 
 #include "absl/log/internal/log_impl.h"
 
-#define ABSL_LOG(severity) ABSL_LOG_IMPL(_##severity)
-#define ABSL_PLOG(severity) ABSL_PLOG_IMPL(_##severity)
-#define ABSL_DLOG(severity) ABSL_DLOG_IMPL(_##severity)
+#define ABSL_LOG(severity) ABSL_LOG_INTERNAL_LOG_IMPL(_##severity)
+#define ABSL_PLOG(severity) ABSL_LOG_INTERNAL_PLOG_IMPL(_##severity)
+#define ABSL_DLOG(severity) ABSL_LOG_INTERNAL_DLOG_IMPL(_##severity)
 
 #define ABSL_LOG_IF(severity, condition) \
-  ABSL_LOG_IF_IMPL(_##severity, condition)
+  ABSL_LOG_INTERNAL_LOG_IF_IMPL(_##severity, condition)
 #define ABSL_PLOG_IF(severity, condition) \
-  ABSL_PLOG_IF_IMPL(_##severity, condition)
+  ABSL_LOG_INTERNAL_PLOG_IF_IMPL(_##severity, condition)
 #define ABSL_DLOG_IF(severity, condition) \
-  ABSL_DLOG_IF_IMPL(_##severity, condition)
+  ABSL_LOG_INTERNAL_DLOG_IF_IMPL(_##severity, condition)
 
-#define ABSL_LOG_EVERY_N(severity, n) ABSL_LOG_EVERY_N_IMPL(_##severity, n)
-#define ABSL_LOG_FIRST_N(severity, n) ABSL_LOG_FIRST_N_IMPL(_##severity, n)
-#define ABSL_LOG_EVERY_POW_2(severity) ABSL_LOG_EVERY_POW_2_IMPL(_##severity)
+#define ABSL_LOG_EVERY_N(severity, n) \
+  ABSL_LOG_INTERNAL_LOG_EVERY_N_IMPL(_##severity, n)
+#define ABSL_LOG_FIRST_N(severity, n) \
+  ABSL_LOG_INTERNAL_LOG_FIRST_N_IMPL(_##severity, n)
+#define ABSL_LOG_EVERY_POW_2(severity) \
+  ABSL_LOG_INTERNAL_LOG_EVERY_POW_2_IMPL(_##severity)
 #define ABSL_LOG_EVERY_N_SEC(severity, n_seconds) \
-  ABSL_LOG_EVERY_N_SEC_IMPL(_##severity, n_seconds)
+  ABSL_LOG_INTERNAL_LOG_EVERY_N_SEC_IMPL(_##severity, n_seconds)
 
-#define ABSL_PLOG_EVERY_N(severity, n) ABSL_PLOG_EVERY_N_IMPL(_##severity, n)
-#define ABSL_PLOG_FIRST_N(severity, n) ABSL_PLOG_FIRST_N_IMPL(_##severity, n)
-#define ABSL_PLOG_EVERY_POW_2(severity) ABSL_PLOG_EVERY_POW_2_IMPL(_##severity)
+#define ABSL_PLOG_EVERY_N(severity, n) \
+  ABSL_LOG_INTERNAL_PLOG_EVERY_N_IMPL(_##severity, n)
+#define ABSL_PLOG_FIRST_N(severity, n) \
+  ABSL_LOG_INTERNAL_PLOG_FIRST_N_IMPL(_##severity, n)
+#define ABSL_PLOG_EVERY_POW_2(severity) \
+  ABSL_LOG_INTERNAL_PLOG_EVERY_POW_2_IMPL(_##severity)
 #define ABSL_PLOG_EVERY_N_SEC(severity, n_seconds) \
-  ABSL_PLOG_EVERY_N_SEC_IMPL(_##severity, n_seconds)
+  ABSL_LOG_INTERNAL_PLOG_EVERY_N_SEC_IMPL(_##severity, n_seconds)
 
-#define ABSL_DLOG_EVERY_N(severity, n) ABSL_DLOG_EVERY_N_IMPL(_##severity, n)
-#define ABSL_DLOG_FIRST_N(severity, n) ABSL_DLOG_FIRST_N_IMPL(_##severity, n)
-#define ABSL_DLOG_EVERY_POW_2(severity) ABSL_DLOG_EVERY_POW_2_IMPL(_##severity)
+#define ABSL_DLOG_EVERY_N(severity, n) \
+  ABSL_LOG_INTERNAL_DLOG_EVERY_N_IMPL(_##severity, n)
+#define ABSL_DLOG_FIRST_N(severity, n) \
+  ABSL_LOG_INTERNAL_DLOG_FIRST_N_IMPL(_##severity, n)
+#define ABSL_DLOG_EVERY_POW_2(severity) \
+  ABSL_LOG_INTERNAL_DLOG_EVERY_POW_2_IMPL(_##severity)
 #define ABSL_DLOG_EVERY_N_SEC(severity, n_seconds) \
-  ABSL_DLOG_EVERY_N_SEC_IMPL(_##severity, n_seconds)
+  ABSL_LOG_INTERNAL_DLOG_EVERY_N_SEC_IMPL(_##severity, n_seconds)
 
 #define ABSL_LOG_IF_EVERY_N(severity, condition, n) \
-  ABSL_LOG_IF_EVERY_N_IMPL(_##severity, condition, n)
+  ABSL_LOG_INTERNAL_LOG_IF_EVERY_N_IMPL(_##severity, condition, n)
 #define ABSL_LOG_IF_FIRST_N(severity, condition, n) \
-  ABSL_LOG_IF_FIRST_N_IMPL(_##severity, condition, n)
+  ABSL_LOG_INTERNAL_LOG_IF_FIRST_N_IMPL(_##severity, condition, n)
 #define ABSL_LOG_IF_EVERY_POW_2(severity, condition) \
-  ABSL_LOG_IF_EVERY_POW_2_IMPL(_##severity, condition)
+  ABSL_LOG_INTERNAL_LOG_IF_EVERY_POW_2_IMPL(_##severity, condition)
 #define ABSL_LOG_IF_EVERY_N_SEC(severity, condition, n_seconds) \
-  ABSL_LOG_IF_EVERY_N_SEC_IMPL(_##severity, condition, n_seconds)
+  ABSL_LOG_INTERNAL_LOG_IF_EVERY_N_SEC_IMPL(_##severity, condition, n_seconds)
 
 #define ABSL_PLOG_IF_EVERY_N(severity, condition, n) \
-  ABSL_PLOG_IF_EVERY_N_IMPL(_##severity, condition, n)
+  ABSL_LOG_INTERNAL_PLOG_IF_EVERY_N_IMPL(_##severity, condition, n)
 #define ABSL_PLOG_IF_FIRST_N(severity, condition, n) \
-  ABSL_PLOG_IF_FIRST_N_IMPL(_##severity, condition, n)
+  ABSL_LOG_INTERNAL_PLOG_IF_FIRST_N_IMPL(_##severity, condition, n)
 #define ABSL_PLOG_IF_EVERY_POW_2(severity, condition) \
-  ABSL_PLOG_IF_EVERY_POW_2_IMPL(_##severity, condition)
+  ABSL_LOG_INTERNAL_PLOG_IF_EVERY_POW_2_IMPL(_##severity, condition)
 #define ABSL_PLOG_IF_EVERY_N_SEC(severity, condition, n_seconds) \
-  ABSL_PLOG_IF_EVERY_N_SEC_IMPL(_##severity, condition, n_seconds)
+  ABSL_LOG_INTERNAL_PLOG_IF_EVERY_N_SEC_IMPL(_##severity, condition, n_seconds)
 
 #define ABSL_DLOG_IF_EVERY_N(severity, condition, n) \
-  ABSL_DLOG_IF_EVERY_N_IMPL(_##severity, condition, n)
+  ABSL_LOG_INTERNAL_DLOG_IF_EVERY_N_IMPL(_##severity, condition, n)
 #define ABSL_DLOG_IF_FIRST_N(severity, condition, n) \
-  ABSL_DLOG_IF_FIRST_N_IMPL(_##severity, condition, n)
+  ABSL_LOG_INTERNAL_DLOG_IF_FIRST_N_IMPL(_##severity, condition, n)
 #define ABSL_DLOG_IF_EVERY_POW_2(severity, condition) \
-  ABSL_DLOG_IF_EVERY_POW_2_IMPL(_##severity, condition)
+  ABSL_LOG_INTERNAL_DLOG_IF_EVERY_POW_2_IMPL(_##severity, condition)
 #define ABSL_DLOG_IF_EVERY_N_SEC(severity, condition, n_seconds) \
-  ABSL_DLOG_IF_EVERY_N_SEC_IMPL(_##severity, condition, n_seconds)
+  ABSL_LOG_INTERNAL_DLOG_IF_EVERY_N_SEC_IMPL(_##severity, condition, n_seconds)
 
 #endif  // ABSL_LOG_ABSL_LOG_H_
diff --git a/absl/log/absl_log_basic_test.cc b/absl/log/absl_log_basic_test.cc
index bc8a787d..3a4b83c1 100644
--- a/absl/log/absl_log_basic_test.cc
+++ b/absl/log/absl_log_basic_test.cc
@@ -18,4 +18,4 @@
 #define ABSL_TEST_LOG ABSL_LOG
 
 #include "gtest/gtest.h"
-#include "absl/log/log_basic_test_impl.h"
+#include "absl/log/log_basic_test_impl.inc"
diff --git a/absl/log/check.h b/absl/log/check.h
index 33145a57..0a2f2e4e 100644
--- a/absl/log/check.h
+++ b/absl/log/check.h
@@ -54,7 +54,7 @@
 // Might produce a message like:
 //
 //   Check failed: !cheese.empty() Out of Cheese
-#define CHECK(condition) ABSL_CHECK_IMPL((condition), #condition)
+#define CHECK(condition) ABSL_LOG_INTERNAL_CHECK_IMPL((condition), #condition)
 
 // QCHECK()
 //
@@ -62,7 +62,7 @@
 // not run registered error handlers (as `QFATAL`).  It is useful when the
 // problem is definitely unrelated to program flow, e.g. when validating user
 // input.
-#define QCHECK(condition) ABSL_QCHECK_IMPL((condition), #condition)
+#define QCHECK(condition) ABSL_LOG_INTERNAL_QCHECK_IMPL((condition), #condition)
 
 // PCHECK()
 //
@@ -77,7 +77,7 @@
 // Might produce a message like:
 //
 //   Check failed: fd != -1 posix is difficult: No such file or directory [2]
-#define PCHECK(condition) ABSL_PCHECK_IMPL((condition), #condition)
+#define PCHECK(condition) ABSL_LOG_INTERNAL_PCHECK_IMPL((condition), #condition)
 
 // DCHECK()
 //
@@ -85,7 +85,7 @@
 // `DLOG`).  Unlike with `CHECK` (but as with `assert`), it is not safe to rely
 // on evaluation of `condition`: when `NDEBUG` is enabled, DCHECK does not
 // evaluate the condition.
-#define DCHECK(condition) ABSL_DCHECK_IMPL((condition), #condition)
+#define DCHECK(condition) ABSL_LOG_INTERNAL_DCHECK_IMPL((condition), #condition)
 
 // `CHECK_EQ` and friends are syntactic sugar for `CHECK(x == y)` that
 // automatically output the expression being tested and the evaluated values on
@@ -113,24 +113,42 @@
 //
 // WARNING: Passing `NULL` as an argument to `CHECK_EQ` and similar macros does
 // not compile.  Use `nullptr` instead.
-#define CHECK_EQ(val1, val2) ABSL_CHECK_EQ_IMPL((val1), #val1, (val2), #val2)
-#define CHECK_NE(val1, val2) ABSL_CHECK_NE_IMPL((val1), #val1, (val2), #val2)
-#define CHECK_LE(val1, val2) ABSL_CHECK_LE_IMPL((val1), #val1, (val2), #val2)
-#define CHECK_LT(val1, val2) ABSL_CHECK_LT_IMPL((val1), #val1, (val2), #val2)
-#define CHECK_GE(val1, val2) ABSL_CHECK_GE_IMPL((val1), #val1, (val2), #val2)
-#define CHECK_GT(val1, val2) ABSL_CHECK_GT_IMPL((val1), #val1, (val2), #val2)
-#define QCHECK_EQ(val1, val2) ABSL_QCHECK_EQ_IMPL((val1), #val1, (val2), #val2)
-#define QCHECK_NE(val1, val2) ABSL_QCHECK_NE_IMPL((val1), #val1, (val2), #val2)
-#define QCHECK_LE(val1, val2) ABSL_QCHECK_LE_IMPL((val1), #val1, (val2), #val2)
-#define QCHECK_LT(val1, val2) ABSL_QCHECK_LT_IMPL((val1), #val1, (val2), #val2)
-#define QCHECK_GE(val1, val2) ABSL_QCHECK_GE_IMPL((val1), #val1, (val2), #val2)
-#define QCHECK_GT(val1, val2) ABSL_QCHECK_GT_IMPL((val1), #val1, (val2), #val2)
-#define DCHECK_EQ(val1, val2) ABSL_DCHECK_EQ_IMPL((val1), #val1, (val2), #val2)
-#define DCHECK_NE(val1, val2) ABSL_DCHECK_NE_IMPL((val1), #val1, (val2), #val2)
-#define DCHECK_LE(val1, val2) ABSL_DCHECK_LE_IMPL((val1), #val1, (val2), #val2)
-#define DCHECK_LT(val1, val2) ABSL_DCHECK_LT_IMPL((val1), #val1, (val2), #val2)
-#define DCHECK_GE(val1, val2) ABSL_DCHECK_GE_IMPL((val1), #val1, (val2), #val2)
-#define DCHECK_GT(val1, val2) ABSL_DCHECK_GT_IMPL((val1), #val1, (val2), #val2)
+#define CHECK_EQ(val1, val2) \
+  ABSL_LOG_INTERNAL_CHECK_EQ_IMPL((val1), #val1, (val2), #val2)
+#define CHECK_NE(val1, val2) \
+  ABSL_LOG_INTERNAL_CHECK_NE_IMPL((val1), #val1, (val2), #val2)
+#define CHECK_LE(val1, val2) \
+  ABSL_LOG_INTERNAL_CHECK_LE_IMPL((val1), #val1, (val2), #val2)
+#define CHECK_LT(val1, val2) \
+  ABSL_LOG_INTERNAL_CHECK_LT_IMPL((val1), #val1, (val2), #val2)
+#define CHECK_GE(val1, val2) \
+  ABSL_LOG_INTERNAL_CHECK_GE_IMPL((val1), #val1, (val2), #val2)
+#define CHECK_GT(val1, val2) \
+  ABSL_LOG_INTERNAL_CHECK_GT_IMPL((val1), #val1, (val2), #val2)
+#define QCHECK_EQ(val1, val2) \
+  ABSL_LOG_INTERNAL_QCHECK_EQ_IMPL((val1), #val1, (val2), #val2)
+#define QCHECK_NE(val1, val2) \
+  ABSL_LOG_INTERNAL_QCHECK_NE_IMPL((val1), #val1, (val2), #val2)
+#define QCHECK_LE(val1, val2) \
+  ABSL_LOG_INTERNAL_QCHECK_LE_IMPL((val1), #val1, (val2), #val2)
+#define QCHECK_LT(val1, val2) \
+  ABSL_LOG_INTERNAL_QCHECK_LT_IMPL((val1), #val1, (val2), #val2)
+#define QCHECK_GE(val1, val2) \
+  ABSL_LOG_INTERNAL_QCHECK_GE_IMPL((val1), #val1, (val2), #val2)
+#define QCHECK_GT(val1, val2) \
+  ABSL_LOG_INTERNAL_QCHECK_GT_IMPL((val1), #val1, (val2), #val2)
+#define DCHECK_EQ(val1, val2) \
+  ABSL_LOG_INTERNAL_DCHECK_EQ_IMPL((val1), #val1, (val2), #val2)
+#define DCHECK_NE(val1, val2) \
+  ABSL_LOG_INTERNAL_DCHECK_NE_IMPL((val1), #val1, (val2), #val2)
+#define DCHECK_LE(val1, val2) \
+  ABSL_LOG_INTERNAL_DCHECK_LE_IMPL((val1), #val1, (val2), #val2)
+#define DCHECK_LT(val1, val2) \
+  ABSL_LOG_INTERNAL_DCHECK_LT_IMPL((val1), #val1, (val2), #val2)
+#define DCHECK_GE(val1, val2) \
+  ABSL_LOG_INTERNAL_DCHECK_GE_IMPL((val1), #val1, (val2), #val2)
+#define DCHECK_GT(val1, val2) \
+  ABSL_LOG_INTERNAL_DCHECK_GT_IMPL((val1), #val1, (val2), #val2)
 
 // `CHECK_OK` and friends validate that the provided `absl::Status` or
 // `absl::StatusOr<T>` is OK.  If it isn't, they print a failure message that
@@ -146,9 +164,9 @@
 // Might produce a message like:
 //
 //   Check failed: FunctionReturnsStatus(x, y, z) is OK (ABORTED: timeout) oops!
-#define CHECK_OK(status) ABSL_CHECK_OK_IMPL((status), #status)
-#define QCHECK_OK(status) ABSL_QCHECK_OK_IMPL((status), #status)
-#define DCHECK_OK(status) ABSL_DCHECK_OK_IMPL((status), #status)
+#define CHECK_OK(status) ABSL_LOG_INTERNAL_CHECK_OK_IMPL((status), #status)
+#define QCHECK_OK(status) ABSL_LOG_INTERNAL_QCHECK_OK_IMPL((status), #status)
+#define DCHECK_OK(status) ABSL_LOG_INTERNAL_DCHECK_OK_IMPL((status), #status)
 
 // `CHECK_STREQ` and friends provide `CHECK_EQ` functionality for C strings,
 // i.e., nul-terminated char arrays.  The `CASE` versions are case-insensitive.
@@ -163,21 +181,29 @@
 // Example:
 //
 //   CHECK_STREQ(Foo().c_str(), Bar().c_str());
-#define CHECK_STREQ(s1, s2) ABSL_CHECK_STREQ_IMPL((s1), #s1, (s2), #s2)
-#define CHECK_STRNE(s1, s2) ABSL_CHECK_STRNE_IMPL((s1), #s1, (s2), #s2)
-#define CHECK_STRCASEEQ(s1, s2) ABSL_CHECK_STRCASEEQ_IMPL((s1), #s1, (s2), #s2)
-#define CHECK_STRCASENE(s1, s2) ABSL_CHECK_STRCASENE_IMPL((s1), #s1, (s2), #s2)
-#define QCHECK_STREQ(s1, s2) ABSL_QCHECK_STREQ_IMPL((s1), #s1, (s2), #s2)
-#define QCHECK_STRNE(s1, s2) ABSL_QCHECK_STRNE_IMPL((s1), #s1, (s2), #s2)
+#define CHECK_STREQ(s1, s2) \
+  ABSL_LOG_INTERNAL_CHECK_STREQ_IMPL((s1), #s1, (s2), #s2)
+#define CHECK_STRNE(s1, s2) \
+  ABSL_LOG_INTERNAL_CHECK_STRNE_IMPL((s1), #s1, (s2), #s2)
+#define CHECK_STRCASEEQ(s1, s2) \
+  ABSL_LOG_INTERNAL_CHECK_STRCASEEQ_IMPL((s1), #s1, (s2), #s2)
+#define CHECK_STRCASENE(s1, s2) \
+  ABSL_LOG_INTERNAL_CHECK_STRCASENE_IMPL((s1), #s1, (s2), #s2)
+#define QCHECK_STREQ(s1, s2) \
+  ABSL_LOG_INTERNAL_QCHECK_STREQ_IMPL((s1), #s1, (s2), #s2)
+#define QCHECK_STRNE(s1, s2) \
+  ABSL_LOG_INTERNAL_QCHECK_STRNE_IMPL((s1), #s1, (s2), #s2)
 #define QCHECK_STRCASEEQ(s1, s2) \
-  ABSL_QCHECK_STRCASEEQ_IMPL((s1), #s1, (s2), #s2)
+  ABSL_LOG_INTERNAL_QCHECK_STRCASEEQ_IMPL((s1), #s1, (s2), #s2)
 #define QCHECK_STRCASENE(s1, s2) \
-  ABSL_QCHECK_STRCASENE_IMPL((s1), #s1, (s2), #s2)
-#define DCHECK_STREQ(s1, s2) ABSL_DCHECK_STREQ_IMPL((s1), #s1, (s2), #s2)
-#define DCHECK_STRNE(s1, s2) ABSL_DCHECK_STRNE_IMPL((s1), #s1, (s2), #s2)
+  ABSL_LOG_INTERNAL_QCHECK_STRCASENE_IMPL((s1), #s1, (s2), #s2)
+#define DCHECK_STREQ(s1, s2) \
+  ABSL_LOG_INTERNAL_DCHECK_STREQ_IMPL((s1), #s1, (s2), #s2)
+#define DCHECK_STRNE(s1, s2) \
+  ABSL_LOG_INTERNAL_DCHECK_STRNE_IMPL((s1), #s1, (s2), #s2)
 #define DCHECK_STRCASEEQ(s1, s2) \
-  ABSL_DCHECK_STRCASEEQ_IMPL((s1), #s1, (s2), #s2)
+  ABSL_LOG_INTERNAL_DCHECK_STRCASEEQ_IMPL((s1), #s1, (s2), #s2)
 #define DCHECK_STRCASENE(s1, s2) \
-  ABSL_DCHECK_STRCASENE_IMPL((s1), #s1, (s2), #s2)
+  ABSL_LOG_INTERNAL_DCHECK_STRCASENE_IMPL((s1), #s1, (s2), #s2)
 
 #endif  // ABSL_LOG_CHECK_H_
diff --git a/absl/log/check_test.cc b/absl/log/check_test.cc
index f44a686e..ef415bd4 100644
--- a/absl/log/check_test.cc
+++ b/absl/log/check_test.cc
@@ -55,4 +55,4 @@
 #define ABSL_TEST_QCHECK_STRCASENE QCHECK_STRCASENE
 
 #include "gtest/gtest.h"
-#include "absl/log/check_test_impl.h"
+#include "absl/log/check_test_impl.inc"
diff --git a/absl/log/check_test_impl.h b/absl/log/check_test_impl.inc
index d5c0aee4..d5c0aee4 100644
--- a/absl/log/check_test_impl.h
+++ b/absl/log/check_test_impl.inc
diff --git a/absl/log/flags.cc b/absl/log/flags.cc
index b5308881..215b7bd5 100644
--- a/absl/log/flags.cc
+++ b/absl/log/flags.cc
@@ -90,19 +90,27 @@ ABSL_FLAG(std::string, log_backtrace_at, "",
     .OnUpdate([] {
       const std::string log_backtrace_at =
           absl::GetFlag(FLAGS_log_backtrace_at);
-      if (log_backtrace_at.empty()) return;
+      if (log_backtrace_at.empty()) {
+        absl::ClearLogBacktraceLocation();
+        return;
+      }
 
       const size_t last_colon = log_backtrace_at.rfind(':');
-      if (last_colon == log_backtrace_at.npos) return;
+      if (last_colon == log_backtrace_at.npos) {
+        absl::ClearLogBacktraceLocation();
+        return;
+      }
 
       const absl::string_view file =
           absl::string_view(log_backtrace_at).substr(0, last_colon);
       int line;
-      if (absl::SimpleAtoi(
+      if (!absl::SimpleAtoi(
               absl::string_view(log_backtrace_at).substr(last_colon + 1),
               &line)) {
-        absl::SetLogBacktraceLocation(file, line);
+        absl::ClearLogBacktraceLocation();
+        return;
       }
+      absl::SetLogBacktraceLocation(file, line);
     });
 
 ABSL_FLAG(bool, log_prefix, true,
diff --git a/absl/log/flags_test.cc b/absl/log/flags_test.cc
index a0f6d763..1080ea11 100644
--- a/absl/log/flags_test.cc
+++ b/absl/log/flags_test.cc
@@ -92,23 +92,23 @@ TEST_F(LogFlagsTest, PrependLogPrefix) {
 
 TEST_F(LogFlagsTest, EmptyBacktraceAtFlag) {
   absl::SetMinLogLevel(absl::LogSeverityAtLeast::kInfo);
-  absl::SetFlag(&FLAGS_log_backtrace_at, "");
   absl::ScopedMockLog test_sink(absl::MockLogDefault::kDisallowUnexpected);
 
   EXPECT_CALL(test_sink, Send(TextMessage(Not(HasSubstr("(stacktrace:")))));
 
   test_sink.StartCapturingLogs();
+  absl::SetFlag(&FLAGS_log_backtrace_at, "");
   LOG(INFO) << "hello world";
 }
 
 TEST_F(LogFlagsTest, BacktraceAtNonsense) {
   absl::SetMinLogLevel(absl::LogSeverityAtLeast::kInfo);
-  absl::SetFlag(&FLAGS_log_backtrace_at, "gibberish");
   absl::ScopedMockLog test_sink(absl::MockLogDefault::kDisallowUnexpected);
 
   EXPECT_CALL(test_sink, Send(TextMessage(Not(HasSubstr("(stacktrace:")))));
 
   test_sink.StartCapturingLogs();
+  absl::SetFlag(&FLAGS_log_backtrace_at, "gibberish");
   LOG(INFO) << "hello world";
 }
 
@@ -116,13 +116,13 @@ TEST_F(LogFlagsTest, BacktraceAtWrongFile) {
   absl::SetMinLogLevel(absl::LogSeverityAtLeast::kInfo);
   const int log_line = __LINE__ + 1;
   auto do_log = [] { LOG(INFO) << "hello world"; };
-  absl::SetFlag(&FLAGS_log_backtrace_at,
-                absl::StrCat("some_other_file.cc:", log_line));
   absl::ScopedMockLog test_sink(absl::MockLogDefault::kDisallowUnexpected);
 
   EXPECT_CALL(test_sink, Send(TextMessage(Not(HasSubstr("(stacktrace:")))));
 
   test_sink.StartCapturingLogs();
+  absl::SetFlag(&FLAGS_log_backtrace_at,
+                absl::StrCat("some_other_file.cc:", log_line));
   do_log();
 }
 
@@ -130,13 +130,13 @@ TEST_F(LogFlagsTest, BacktraceAtWrongLine) {
   absl::SetMinLogLevel(absl::LogSeverityAtLeast::kInfo);
   const int log_line = __LINE__ + 1;
   auto do_log = [] { LOG(INFO) << "hello world"; };
-  absl::SetFlag(&FLAGS_log_backtrace_at,
-                absl::StrCat("flags_test.cc:", log_line + 1));
   absl::ScopedMockLog test_sink(absl::MockLogDefault::kDisallowUnexpected);
 
   EXPECT_CALL(test_sink, Send(TextMessage(Not(HasSubstr("(stacktrace:")))));
 
   test_sink.StartCapturingLogs();
+  absl::SetFlag(&FLAGS_log_backtrace_at,
+                absl::StrCat("flags_test.cc:", log_line + 1));
   do_log();
 }
 
@@ -144,12 +144,12 @@ TEST_F(LogFlagsTest, BacktraceAtWholeFilename) {
   absl::SetMinLogLevel(absl::LogSeverityAtLeast::kInfo);
   const int log_line = __LINE__ + 1;
   auto do_log = [] { LOG(INFO) << "hello world"; };
-  absl::SetFlag(&FLAGS_log_backtrace_at, absl::StrCat(__FILE__, ":", log_line));
   absl::ScopedMockLog test_sink(absl::MockLogDefault::kDisallowUnexpected);
 
   EXPECT_CALL(test_sink, Send(TextMessage(Not(HasSubstr("(stacktrace:")))));
 
   test_sink.StartCapturingLogs();
+  absl::SetFlag(&FLAGS_log_backtrace_at, absl::StrCat(__FILE__, ":", log_line));
   do_log();
 }
 
@@ -157,13 +157,13 @@ TEST_F(LogFlagsTest, BacktraceAtNonmatchingSuffix) {
   absl::SetMinLogLevel(absl::LogSeverityAtLeast::kInfo);
   const int log_line = __LINE__ + 1;
   auto do_log = [] { LOG(INFO) << "hello world"; };
-  absl::SetFlag(&FLAGS_log_backtrace_at,
-                absl::StrCat("flags_test.cc:", log_line, "gibberish"));
   absl::ScopedMockLog test_sink(absl::MockLogDefault::kDisallowUnexpected);
 
   EXPECT_CALL(test_sink, Send(TextMessage(Not(HasSubstr("(stacktrace:")))));
 
   test_sink.StartCapturingLogs();
+  absl::SetFlag(&FLAGS_log_backtrace_at,
+                absl::StrCat("flags_test.cc:", log_line, "gibberish"));
   do_log();
 }
 
@@ -171,13 +171,17 @@ TEST_F(LogFlagsTest, LogsBacktrace) {
   absl::SetMinLogLevel(absl::LogSeverityAtLeast::kInfo);
   const int log_line = __LINE__ + 1;
   auto do_log = [] { LOG(INFO) << "hello world"; };
-  absl::SetFlag(&FLAGS_log_backtrace_at,
-                absl::StrCat("flags_test.cc:", log_line));
   absl::ScopedMockLog test_sink(absl::MockLogDefault::kDisallowUnexpected);
 
+  testing::InSequence seq;
   EXPECT_CALL(test_sink, Send(TextMessage(HasSubstr("(stacktrace:"))));
+  EXPECT_CALL(test_sink, Send(TextMessage(Not(HasSubstr("(stacktrace:")))));
 
   test_sink.StartCapturingLogs();
+  absl::SetFlag(&FLAGS_log_backtrace_at,
+                absl::StrCat("flags_test.cc:", log_line));
+  do_log();
+  absl::SetFlag(&FLAGS_log_backtrace_at, "");
   do_log();
 }
 
diff --git a/absl/log/globals.cc b/absl/log/globals.cc
index 6dfe81f0..cc85438f 100644
--- a/absl/log/globals.cc
+++ b/absl/log/globals.cc
@@ -14,14 +14,17 @@
 
 #include "absl/log/globals.h"
 
-#include <stddef.h>
-#include <stdint.h>
-
 #include <atomic>
+#include <cstddef>
+#include <cstdint>
+#include <cstdlib>
+#include <cstring>
+#include <string>
 
 #include "absl/base/attributes.h"
 #include "absl/base/config.h"
 #include "absl/base/internal/atomic_hook.h"
+#include "absl/base/internal/raw_logging.h"
 #include "absl/base/log_severity.h"
 #include "absl/hash/hash.h"
 #include "absl/strings/string_view.h"
@@ -43,6 +46,9 @@ ABSL_CONST_INIT std::atomic<int> stderrthreshold{
 ABSL_CONST_INIT std::atomic<size_t> log_backtrace_at_hash{0};
 ABSL_CONST_INIT std::atomic<bool> prepend_log_prefix{true};
 
+constexpr char kDefaultAndroidTag[] = "native";
+ABSL_CONST_INIT std::atomic<const char*> android_log_tag{kDefaultAndroidTag};
+
 ABSL_INTERNAL_ATOMIC_HOOK_ATTRIBUTES
 absl::base_internal::AtomicHook<log_internal::LoggingGlobalsListener>
     logging_globals_listener;
@@ -121,9 +127,29 @@ ScopedStderrThreshold::~ScopedStderrThreshold() {
 
 namespace log_internal {
 
+const char* GetAndroidNativeTag() {
+  return android_log_tag.load(std::memory_order_acquire);
+}
+
+}  // namespace log_internal
+
+void SetAndroidNativeTag(const char* tag) {
+  ABSL_CONST_INIT static std::atomic<const std::string*> user_log_tag(nullptr);
+  ABSL_INTERNAL_CHECK(tag, "tag must be non-null.");
+
+  const std::string* tag_str = new std::string(tag);
+  ABSL_INTERNAL_CHECK(
+      android_log_tag.exchange(tag_str->c_str(), std::memory_order_acq_rel) ==
+          kDefaultAndroidTag,
+      "SetAndroidNativeTag() must only be called once per process!");
+  user_log_tag.store(tag_str, std::memory_order_relaxed);
+}
+
+namespace log_internal {
+
 bool ShouldLogBacktraceAt(absl::string_view file, int line) {
   const size_t flag_hash =
-      log_backtrace_at_hash.load(std::memory_order_acquire);
+      log_backtrace_at_hash.load(std::memory_order_relaxed);
 
   return flag_hash != 0 && flag_hash == HashSiteForLogBacktraceAt(file, line);
 }
@@ -132,7 +158,11 @@ bool ShouldLogBacktraceAt(absl::string_view file, int line) {
 
 void SetLogBacktraceLocation(absl::string_view file, int line) {
   log_backtrace_at_hash.store(HashSiteForLogBacktraceAt(file, line),
-                              std::memory_order_release);
+                              std::memory_order_relaxed);
+}
+
+void ClearLogBacktraceLocation() {
+  log_backtrace_at_hash.store(0, std::memory_order_relaxed);
 }
 
 bool ShouldPrependLogPrefix() {
diff --git a/absl/log/globals.h b/absl/log/globals.h
index 32b87db0..bc3864c1 100644
--- a/absl/log/globals.h
+++ b/absl/log/globals.h
@@ -110,8 +110,8 @@ class ScopedStderrThreshold final {
 // Log Backtrace At
 //------------------------------------------------------------------------------
 //
-// Users can request backtrace to be logged at specific locations, specified
-// by file and line number.
+// Users can request an existing `LOG` statement, specified by file and line
+// number, to also include a backtrace when logged.
 
 // ShouldLogBacktraceAt()
 //
@@ -123,9 +123,16 @@ ABSL_MUST_USE_RESULT bool ShouldLogBacktraceAt(absl::string_view file,
 
 // SetLogBacktraceLocation()
 //
-// Sets the location the backtrace should be logged at.
+// Sets the location the backtrace should be logged at.  If the specified
+// location isn't a `LOG` statement, the effect will be the same as
+// `ClearLogBacktraceLocation` (but less efficient).
 void SetLogBacktraceLocation(absl::string_view file, int line);
 
+// ClearLogBacktraceLocation()
+//
+// Clears the set location so that backtraces will no longer be logged at it.
+void ClearLogBacktraceLocation();
+
 //------------------------------------------------------------------------------
 // Prepend Log Prefix
 //------------------------------------------------------------------------------
@@ -145,6 +152,29 @@ ABSL_MUST_USE_RESULT bool ShouldPrependLogPrefix();
 // This function is async-signal-safe.
 void EnableLogPrefix(bool on_off);
 
+//------------------------------------------------------------------------------
+// Configure Android Native Log Tag
+//------------------------------------------------------------------------------
+//
+// The logging library forwards to the Android system log API when built for
+// Android.  That API takes a string "tag" value in addition to a message and
+// severity level.  The tag is used to identify the source of messages and to
+// filter them.  This library uses the tag "native" by default.
+
+// SetAndroidNativeTag()
+//
+// Stores a copy of the string pointed to by `tag` and uses it as the Android
+// logging tag thereafter. `tag` must not be null.
+// This function must not be called more than once!
+void SetAndroidNativeTag(const char* tag);
+
+namespace log_internal {
+// GetAndroidNativeTag()
+//
+// Returns the configured Android logging tag.
+const char* GetAndroidNativeTag();
+}  // namespace log_internal
+
 namespace log_internal {
 
 using LoggingGlobalsListener = void (*)();
diff --git a/absl/log/globals_test.cc b/absl/log/globals_test.cc
index 6710c5aa..f7af47cd 100644
--- a/absl/log/globals_test.cc
+++ b/absl/log/globals_test.cc
@@ -15,8 +15,6 @@
 
 #include "absl/log/globals.h"
 
-#include <string>
-
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
 #include "absl/base/attributes.h"
@@ -27,6 +25,8 @@
 #include "absl/log/scoped_mock_log.h"
 
 namespace {
+using ::testing::_;
+using ::testing::StrEq;
 
 auto* test_env ABSL_ATTRIBUTE_UNUSED = ::testing::AddGlobalTestEnvironment(
     new absl::log_internal::LogTestEnvironment);
@@ -88,4 +88,17 @@ TEST(TestGlobals, LogPrefix) {
   EXPECT_TRUE(absl::ShouldPrependLogPrefix());
 }
 
+TEST(TestGlobals, AndroidLogTag) {
+  // Verify invalid tags result in a check failure.
+  EXPECT_DEATH_IF_SUPPORTED(absl::SetAndroidNativeTag(nullptr), ".*");
+
+  // Verify valid tags applied.
+  EXPECT_THAT(absl::log_internal::GetAndroidNativeTag(), StrEq("native"));
+  absl::SetAndroidNativeTag("test_tag");
+  EXPECT_THAT(absl::log_internal::GetAndroidNativeTag(), StrEq("test_tag"));
+
+  // Verify that additional calls (more than 1) result in a check failure.
+  EXPECT_DEATH_IF_SUPPORTED(absl::SetAndroidNativeTag("test_tag_fail"), ".*");
+}
+
 }  // namespace
diff --git a/absl/log/internal/BUILD.bazel b/absl/log/internal/BUILD.bazel
index a1f1a67c..555c5e5c 100644
--- a/absl/log/internal/BUILD.bazel
+++ b/absl/log/internal/BUILD.bazel
@@ -320,13 +320,13 @@ cc_library(
     linkopts = ABSL_DEFAULT_LINKOPTS,
     deps = [
         ":test_helpers",
-        "@com_google_googletest//:gtest",
         "//absl/base:config",
         "//absl/base:core_headers",
         "//absl/base:log_severity",
         "//absl/log:log_entry",
         "//absl/strings",
         "//absl/time",
+        "@com_google_googletest//:gtest",
     ] + select({
         "//absl:msvc_compiler": [],
         "//conditions:default": [
diff --git a/absl/log/internal/check_impl.h b/absl/log/internal/check_impl.h
index c9c28e3e..00f25f80 100644
--- a/absl/log/internal/check_impl.h
+++ b/absl/log/internal/check_impl.h
@@ -22,128 +22,128 @@
 #include "absl/log/internal/strip.h"
 
 // CHECK
-#define ABSL_CHECK_IMPL(condition, condition_text)                    \
+#define ABSL_LOG_INTERNAL_CHECK_IMPL(condition, condition_text)       \
   ABSL_LOG_INTERNAL_CONDITION_FATAL(STATELESS,                        \
                                     ABSL_PREDICT_FALSE(!(condition))) \
   ABSL_LOG_INTERNAL_CHECK(condition_text).InternalStream()
 
-#define ABSL_QCHECK_IMPL(condition, condition_text)                    \
+#define ABSL_LOG_INTERNAL_QCHECK_IMPL(condition, condition_text)       \
   ABSL_LOG_INTERNAL_CONDITION_QFATAL(STATELESS,                        \
                                      ABSL_PREDICT_FALSE(!(condition))) \
   ABSL_LOG_INTERNAL_QCHECK(condition_text).InternalStream()
 
-#define ABSL_PCHECK_IMPL(condition, condition_text) \
-  ABSL_CHECK_IMPL(condition, condition_text).WithPerror()
+#define ABSL_LOG_INTERNAL_PCHECK_IMPL(condition, condition_text) \
+  ABSL_LOG_INTERNAL_CHECK_IMPL(condition, condition_text).WithPerror()
 
 #ifndef NDEBUG
-#define ABSL_DCHECK_IMPL(condition, condition_text) \
-  ABSL_CHECK_IMPL(condition, condition_text)
+#define ABSL_LOG_INTERNAL_DCHECK_IMPL(condition, condition_text) \
+  ABSL_LOG_INTERNAL_CHECK_IMPL(condition, condition_text)
 #else
-#define ABSL_DCHECK_IMPL(condition, condition_text) \
-  ABSL_CHECK_IMPL(true || (condition), "true")
+#define ABSL_LOG_INTERNAL_DCHECK_IMPL(condition, condition_text) \
+  ABSL_LOG_INTERNAL_CHECK_IMPL(true || (condition), "true")
 #endif
 
 // CHECK_EQ
-#define ABSL_CHECK_EQ_IMPL(val1, val1_text, val2, val2_text) \
+#define ABSL_LOG_INTERNAL_CHECK_EQ_IMPL(val1, val1_text, val2, val2_text) \
   ABSL_LOG_INTERNAL_CHECK_OP(Check_EQ, ==, val1, val1_text, val2, val2_text)
-#define ABSL_CHECK_NE_IMPL(val1, val1_text, val2, val2_text) \
+#define ABSL_LOG_INTERNAL_CHECK_NE_IMPL(val1, val1_text, val2, val2_text) \
   ABSL_LOG_INTERNAL_CHECK_OP(Check_NE, !=, val1, val1_text, val2, val2_text)
-#define ABSL_CHECK_LE_IMPL(val1, val1_text, val2, val2_text) \
+#define ABSL_LOG_INTERNAL_CHECK_LE_IMPL(val1, val1_text, val2, val2_text) \
   ABSL_LOG_INTERNAL_CHECK_OP(Check_LE, <=, val1, val1_text, val2, val2_text)
-#define ABSL_CHECK_LT_IMPL(val1, val1_text, val2, val2_text) \
+#define ABSL_LOG_INTERNAL_CHECK_LT_IMPL(val1, val1_text, val2, val2_text) \
   ABSL_LOG_INTERNAL_CHECK_OP(Check_LT, <, val1, val1_text, val2, val2_text)
-#define ABSL_CHECK_GE_IMPL(val1, val1_text, val2, val2_text) \
+#define ABSL_LOG_INTERNAL_CHECK_GE_IMPL(val1, val1_text, val2, val2_text) \
   ABSL_LOG_INTERNAL_CHECK_OP(Check_GE, >=, val1, val1_text, val2, val2_text)
-#define ABSL_CHECK_GT_IMPL(val1, val1_text, val2, val2_text) \
+#define ABSL_LOG_INTERNAL_CHECK_GT_IMPL(val1, val1_text, val2, val2_text) \
   ABSL_LOG_INTERNAL_CHECK_OP(Check_GT, >, val1, val1_text, val2, val2_text)
-#define ABSL_QCHECK_EQ_IMPL(val1, val1_text, val2, val2_text) \
+#define ABSL_LOG_INTERNAL_QCHECK_EQ_IMPL(val1, val1_text, val2, val2_text) \
   ABSL_LOG_INTERNAL_QCHECK_OP(Check_EQ, ==, val1, val1_text, val2, val2_text)
-#define ABSL_QCHECK_NE_IMPL(val1, val1_text, val2, val2_text) \
+#define ABSL_LOG_INTERNAL_QCHECK_NE_IMPL(val1, val1_text, val2, val2_text) \
   ABSL_LOG_INTERNAL_QCHECK_OP(Check_NE, !=, val1, val1_text, val2, val2_text)
-#define ABSL_QCHECK_LE_IMPL(val1, val1_text, val2, val2_text) \
+#define ABSL_LOG_INTERNAL_QCHECK_LE_IMPL(val1, val1_text, val2, val2_text) \
   ABSL_LOG_INTERNAL_QCHECK_OP(Check_LE, <=, val1, val1_text, val2, val2_text)
-#define ABSL_QCHECK_LT_IMPL(val1, val1_text, val2, val2_text) \
+#define ABSL_LOG_INTERNAL_QCHECK_LT_IMPL(val1, val1_text, val2, val2_text) \
   ABSL_LOG_INTERNAL_QCHECK_OP(Check_LT, <, val1, val1_text, val2, val2_text)
-#define ABSL_QCHECK_GE_IMPL(val1, val1_text, val2, val2_text) \
+#define ABSL_LOG_INTERNAL_QCHECK_GE_IMPL(val1, val1_text, val2, val2_text) \
   ABSL_LOG_INTERNAL_QCHECK_OP(Check_GE, >=, val1, val1_text, val2, val2_text)
-#define ABSL_QCHECK_GT_IMPL(val1, val1_text, val2, val2_text) \
+#define ABSL_LOG_INTERNAL_QCHECK_GT_IMPL(val1, val1_text, val2, val2_text) \
   ABSL_LOG_INTERNAL_QCHECK_OP(Check_GT, >, val1, val1_text, val2, val2_text)
 #ifndef NDEBUG
-#define ABSL_DCHECK_EQ_IMPL(val1, val1_text, val2, val2_text) \
-  ABSL_CHECK_EQ_IMPL(val1, val1_text, val2, val2_text)
-#define ABSL_DCHECK_NE_IMPL(val1, val1_text, val2, val2_text) \
-  ABSL_CHECK_NE_IMPL(val1, val1_text, val2, val2_text)
-#define ABSL_DCHECK_LE_IMPL(val1, val1_text, val2, val2_text) \
-  ABSL_CHECK_LE_IMPL(val1, val1_text, val2, val2_text)
-#define ABSL_DCHECK_LT_IMPL(val1, val1_text, val2, val2_text) \
-  ABSL_CHECK_LT_IMPL(val1, val1_text, val2, val2_text)
-#define ABSL_DCHECK_GE_IMPL(val1, val1_text, val2, val2_text) \
-  ABSL_CHECK_GE_IMPL(val1, val1_text, val2, val2_text)
-#define ABSL_DCHECK_GT_IMPL(val1, val1_text, val2, val2_text) \
-  ABSL_CHECK_GT_IMPL(val1, val1_text, val2, val2_text)
+#define ABSL_LOG_INTERNAL_DCHECK_EQ_IMPL(val1, val1_text, val2, val2_text) \
+  ABSL_LOG_INTERNAL_CHECK_EQ_IMPL(val1, val1_text, val2, val2_text)
+#define ABSL_LOG_INTERNAL_DCHECK_NE_IMPL(val1, val1_text, val2, val2_text) \
+  ABSL_LOG_INTERNAL_CHECK_NE_IMPL(val1, val1_text, val2, val2_text)
+#define ABSL_LOG_INTERNAL_DCHECK_LE_IMPL(val1, val1_text, val2, val2_text) \
+  ABSL_LOG_INTERNAL_CHECK_LE_IMPL(val1, val1_text, val2, val2_text)
+#define ABSL_LOG_INTERNAL_DCHECK_LT_IMPL(val1, val1_text, val2, val2_text) \
+  ABSL_LOG_INTERNAL_CHECK_LT_IMPL(val1, val1_text, val2, val2_text)
+#define ABSL_LOG_INTERNAL_DCHECK_GE_IMPL(val1, val1_text, val2, val2_text) \
+  ABSL_LOG_INTERNAL_CHECK_GE_IMPL(val1, val1_text, val2, val2_text)
+#define ABSL_LOG_INTERNAL_DCHECK_GT_IMPL(val1, val1_text, val2, val2_text) \
+  ABSL_LOG_INTERNAL_CHECK_GT_IMPL(val1, val1_text, val2, val2_text)
 #else  // ndef NDEBUG
-#define ABSL_DCHECK_EQ_IMPL(val1, val1_text, val2, val2_text) \
+#define ABSL_LOG_INTERNAL_DCHECK_EQ_IMPL(val1, val1_text, val2, val2_text) \
   ABSL_LOG_INTERNAL_DCHECK_NOP(val1, val2)
-#define ABSL_DCHECK_NE_IMPL(val1, val1_text, val2, val2_text) \
+#define ABSL_LOG_INTERNAL_DCHECK_NE_IMPL(val1, val1_text, val2, val2_text) \
   ABSL_LOG_INTERNAL_DCHECK_NOP(val1, val2)
-#define ABSL_DCHECK_LE_IMPL(val1, val1_text, val2, val2_text) \
+#define ABSL_LOG_INTERNAL_DCHECK_LE_IMPL(val1, val1_text, val2, val2_text) \
   ABSL_LOG_INTERNAL_DCHECK_NOP(val1, val2)
-#define ABSL_DCHECK_LT_IMPL(val1, val1_text, val2, val2_text) \
+#define ABSL_LOG_INTERNAL_DCHECK_LT_IMPL(val1, val1_text, val2, val2_text) \
   ABSL_LOG_INTERNAL_DCHECK_NOP(val1, val2)
-#define ABSL_DCHECK_GE_IMPL(val1, val1_text, val2, val2_text) \
+#define ABSL_LOG_INTERNAL_DCHECK_GE_IMPL(val1, val1_text, val2, val2_text) \
   ABSL_LOG_INTERNAL_DCHECK_NOP(val1, val2)
-#define ABSL_DCHECK_GT_IMPL(val1, val1_text, val2, val2_text) \
+#define ABSL_LOG_INTERNAL_DCHECK_GT_IMPL(val1, val1_text, val2, val2_text) \
   ABSL_LOG_INTERNAL_DCHECK_NOP(val1, val2)
 #endif  // def NDEBUG
 
 // CHECK_OK
-#define ABSL_CHECK_OK_IMPL(status, status_text) \
+#define ABSL_LOG_INTERNAL_CHECK_OK_IMPL(status, status_text) \
   ABSL_LOG_INTERNAL_CHECK_OK(status, status_text)
-#define ABSL_QCHECK_OK_IMPL(status, status_text) \
+#define ABSL_LOG_INTERNAL_QCHECK_OK_IMPL(status, status_text) \
   ABSL_LOG_INTERNAL_QCHECK_OK(status, status_text)
 #ifndef NDEBUG
-#define ABSL_DCHECK_OK_IMPL(status, status_text) \
+#define ABSL_LOG_INTERNAL_DCHECK_OK_IMPL(status, status_text) \
   ABSL_LOG_INTERNAL_CHECK_OK(status, status_text)
 #else
-#define ABSL_DCHECK_OK_IMPL(status, status_text) \
+#define ABSL_LOG_INTERNAL_DCHECK_OK_IMPL(status, status_text) \
   ABSL_LOG_INTERNAL_DCHECK_NOP(status, nullptr)
 #endif
 
 // CHECK_STREQ
-#define ABSL_CHECK_STREQ_IMPL(s1, s1_text, s2, s2_text) \
+#define ABSL_LOG_INTERNAL_CHECK_STREQ_IMPL(s1, s1_text, s2, s2_text) \
   ABSL_LOG_INTERNAL_CHECK_STROP(strcmp, ==, true, s1, s1_text, s2, s2_text)
-#define ABSL_CHECK_STRNE_IMPL(s1, s1_text, s2, s2_text) \
+#define ABSL_LOG_INTERNAL_CHECK_STRNE_IMPL(s1, s1_text, s2, s2_text) \
   ABSL_LOG_INTERNAL_CHECK_STROP(strcmp, !=, false, s1, s1_text, s2, s2_text)
-#define ABSL_CHECK_STRCASEEQ_IMPL(s1, s1_text, s2, s2_text) \
+#define ABSL_LOG_INTERNAL_CHECK_STRCASEEQ_IMPL(s1, s1_text, s2, s2_text) \
   ABSL_LOG_INTERNAL_CHECK_STROP(strcasecmp, ==, true, s1, s1_text, s2, s2_text)
-#define ABSL_CHECK_STRCASENE_IMPL(s1, s1_text, s2, s2_text) \
+#define ABSL_LOG_INTERNAL_CHECK_STRCASENE_IMPL(s1, s1_text, s2, s2_text) \
   ABSL_LOG_INTERNAL_CHECK_STROP(strcasecmp, !=, false, s1, s1_text, s2, s2_text)
-#define ABSL_QCHECK_STREQ_IMPL(s1, s1_text, s2, s2_text) \
+#define ABSL_LOG_INTERNAL_QCHECK_STREQ_IMPL(s1, s1_text, s2, s2_text) \
   ABSL_LOG_INTERNAL_QCHECK_STROP(strcmp, ==, true, s1, s1_text, s2, s2_text)
-#define ABSL_QCHECK_STRNE_IMPL(s1, s1_text, s2, s2_text) \
+#define ABSL_LOG_INTERNAL_QCHECK_STRNE_IMPL(s1, s1_text, s2, s2_text) \
   ABSL_LOG_INTERNAL_QCHECK_STROP(strcmp, !=, false, s1, s1_text, s2, s2_text)
-#define ABSL_QCHECK_STRCASEEQ_IMPL(s1, s1_text, s2, s2_text) \
+#define ABSL_LOG_INTERNAL_QCHECK_STRCASEEQ_IMPL(s1, s1_text, s2, s2_text) \
   ABSL_LOG_INTERNAL_QCHECK_STROP(strcasecmp, ==, true, s1, s1_text, s2, s2_text)
-#define ABSL_QCHECK_STRCASENE_IMPL(s1, s1_text, s2, s2_text)             \
-  ABSL_LOG_INTERNAL_QCHECK_STROP(strcasecmp, !=, false, s1, s1_text, s2, \
+#define ABSL_LOG_INTERNAL_QCHECK_STRCASENE_IMPL(s1, s1_text, s2, s2_text) \
+  ABSL_LOG_INTERNAL_QCHECK_STROP(strcasecmp, !=, false, s1, s1_text, s2,  \
                                  s2_text)
 #ifndef NDEBUG
-#define ABSL_DCHECK_STREQ_IMPL(s1, s1_text, s2, s2_text) \
-  ABSL_CHECK_STREQ_IMPL(s1, s1_text, s2, s2_text)
-#define ABSL_DCHECK_STRCASEEQ_IMPL(s1, s1_text, s2, s2_text) \
-  ABSL_CHECK_STRCASEEQ_IMPL(s1, s1_text, s2, s2_text)
-#define ABSL_DCHECK_STRNE_IMPL(s1, s1_text, s2, s2_text) \
-  ABSL_CHECK_STRNE_IMPL(s1, s1_text, s2, s2_text)
-#define ABSL_DCHECK_STRCASENE_IMPL(s1, s1_text, s2, s2_text) \
-  ABSL_CHECK_STRCASENE_IMPL(s1, s1_text, s2, s2_text)
+#define ABSL_LOG_INTERNAL_DCHECK_STREQ_IMPL(s1, s1_text, s2, s2_text) \
+  ABSL_LOG_INTERNAL_CHECK_STREQ_IMPL(s1, s1_text, s2, s2_text)
+#define ABSL_LOG_INTERNAL_DCHECK_STRCASEEQ_IMPL(s1, s1_text, s2, s2_text) \
+  ABSL_LOG_INTERNAL_CHECK_STRCASEEQ_IMPL(s1, s1_text, s2, s2_text)
+#define ABSL_LOG_INTERNAL_DCHECK_STRNE_IMPL(s1, s1_text, s2, s2_text) \
+  ABSL_LOG_INTERNAL_CHECK_STRNE_IMPL(s1, s1_text, s2, s2_text)
+#define ABSL_LOG_INTERNAL_DCHECK_STRCASENE_IMPL(s1, s1_text, s2, s2_text) \
+  ABSL_LOG_INTERNAL_CHECK_STRCASENE_IMPL(s1, s1_text, s2, s2_text)
 #else  // ndef NDEBUG
-#define ABSL_DCHECK_STREQ_IMPL(s1, s1_text, s2, s2_text) \
+#define ABSL_LOG_INTERNAL_DCHECK_STREQ_IMPL(s1, s1_text, s2, s2_text) \
   ABSL_LOG_INTERNAL_DCHECK_NOP(s1, s2)
-#define ABSL_DCHECK_STRCASEEQ_IMPL(s1, s1_text, s2, s2_text) \
+#define ABSL_LOG_INTERNAL_DCHECK_STRCASEEQ_IMPL(s1, s1_text, s2, s2_text) \
   ABSL_LOG_INTERNAL_DCHECK_NOP(s1, s2)
-#define ABSL_DCHECK_STRNE_IMPL(s1, s1_text, s2, s2_text) \
+#define ABSL_LOG_INTERNAL_DCHECK_STRNE_IMPL(s1, s1_text, s2, s2_text) \
   ABSL_LOG_INTERNAL_DCHECK_NOP(s1, s2)
-#define ABSL_DCHECK_STRCASENE_IMPL(s1, s1_text, s2, s2_text) \
+#define ABSL_LOG_INTERNAL_DCHECK_STRCASENE_IMPL(s1, s1_text, s2, s2_text) \
   ABSL_LOG_INTERNAL_DCHECK_NOP(s1, s2)
 #endif  // def NDEBUG
 
diff --git a/absl/log/internal/check_op.h b/absl/log/internal/check_op.h
index 4907b89b..20b01b5e 100644
--- a/absl/log/internal/check_op.h
+++ b/absl/log/internal/check_op.h
@@ -371,7 +371,9 @@ inline constexpr unsigned short GetReferenceableValue(               // NOLINT
   return t;
 }
 inline constexpr int GetReferenceableValue(int t) { return t; }
-inline unsigned int GetReferenceableValue(unsigned int t) { return t; }
+inline constexpr unsigned int GetReferenceableValue(unsigned int t) {
+  return t;
+}
 inline constexpr long GetReferenceableValue(long t) { return t; }  // NOLINT
 inline constexpr unsigned long GetReferenceableValue(              // NOLINT
     unsigned long t) {                                             // NOLINT
diff --git a/absl/log/internal/conditions.h b/absl/log/internal/conditions.h
index b89f1dfd..f576d650 100644
--- a/absl/log/internal/conditions.h
+++ b/absl/log/internal/conditions.h
@@ -23,7 +23,7 @@
 #ifndef ABSL_LOG_INTERNAL_CONDITIONS_H_
 #define ABSL_LOG_INTERNAL_CONDITIONS_H_
 
-#ifdef _WIN32
+#if defined(_WIN32) || defined(__hexagon__)
 #include <cstdlib>
 #else
 #include <unistd.h>
@@ -56,9 +56,15 @@
 // the ternary expression does a better job avoiding spurious diagnostics
 // (dangling else, missing switch case) and preserving noreturn semantics (e.g.
 // on `LOG(FATAL)`) without requiring braces.
+//
+// The `switch` ensures that this expansion is the begnning of a statement (as
+// opposed to an expression) and prevents shenanigans like
+// `AFunction(LOG(INFO))` and `decltype(LOG(INFO))`.  The apparently-redundant
+// `default` case makes the condition more amenable to Clang dataflow analysis.
 #define ABSL_LOG_INTERNAL_STATELESS_CONDITION(condition) \
   switch (0)                                             \
   case 0:                                                \
+  default:                                               \
     !(condition) ? (void)0 : ::absl::log_internal::Voidify()&&
 
 // `ABSL_LOG_INTERNAL_STATEFUL_CONDITION` applies a condition like
diff --git a/absl/log/internal/globals.cc b/absl/log/internal/globals.cc
index 863b047f..359858f1 100644
--- a/absl/log/internal/globals.cc
+++ b/absl/log/internal/globals.cc
@@ -17,11 +17,16 @@
 #include <atomic>
 #include <cstdio>
 
+#if defined(__EMSCRIPTEN__)
+#include <emscripten/console.h>
+#endif
+
 #include "absl/base/attributes.h"
 #include "absl/base/config.h"
 #include "absl/base/internal/raw_logging.h"
 #include "absl/base/log_severity.h"
 #include "absl/strings/string_view.h"
+#include "absl/strings/strip.h"
 #include "absl/time/time.h"
 
 namespace absl {
@@ -55,9 +60,24 @@ void SetInitialized() {
 }
 
 void WriteToStderr(absl::string_view message, absl::LogSeverity severity) {
+  if (message.empty()) return;
+#if defined(__EMSCRIPTEN__)
+  // In WebAssembly, bypass filesystem emulation via fwrite.
+  // Skip a trailing newline character as emscripten_errn adds one itself.
+  const auto message_minus_newline = absl::StripSuffix(message, "\n");
+  // emscripten_errn was introduced in 3.1.41 but broken in standalone mode
+  // until 3.1.43.
+#if ABSL_INTERNAL_EMSCRIPTEN_VERSION >= 3001043
+  emscripten_errn(message_minus_newline.data(), message_minus_newline.size());
+#else
+  std::string null_terminated_message(message_minus_newline);
+  _emscripten_err(null_terminated_message.c_str());
+#endif
+#else
   // Avoid using std::cerr from this module since we may get called during
   // exit code, and cerr may be partially or fully destroyed by then.
   std::fwrite(message.data(), message.size(), 1, stderr);
+#endif
 
 #if defined(_WIN64) || defined(_WIN32) || defined(_WIN16)
   // C99 requires stderr to not be fully-buffered by default (7.19.3.7), but
diff --git a/absl/log/internal/log_format.cc b/absl/log/internal/log_format.cc
index b8cd5ac4..23cef88a 100644
--- a/absl/log/internal/log_format.cc
+++ b/absl/log/internal/log_format.cc
@@ -49,7 +49,7 @@ namespace {
 
 // This templated function avoids compiler warnings about tautological
 // comparisons when log_internal::Tid is unsigned. It can be replaced with a
-// constexpr if once the minimum C++ version Abseil suppports is C++17.
+// constexpr if once the minimum C++ version Abseil supports is C++17.
 template <typename T>
 inline std::enable_if_t<!std::is_signed<T>::value>
 PutLeadingWhitespace(T tid, char*& p) {
@@ -113,27 +113,29 @@ size_t FormatBoundedFields(absl::LogSeverity severity, absl::Time timestamp,
   char* p = buf.data();
   *p++ = absl::LogSeverityName(severity)[0];
   const absl::TimeZone::CivilInfo ci = tz->At(timestamp);
-  absl::numbers_internal::PutTwoDigits(static_cast<size_t>(ci.cs.month()), p);
+  absl::numbers_internal::PutTwoDigits(static_cast<uint32_t>(ci.cs.month()), p);
   p += 2;
-  absl::numbers_internal::PutTwoDigits(static_cast<size_t>(ci.cs.day()), p);
+  absl::numbers_internal::PutTwoDigits(static_cast<uint32_t>(ci.cs.day()), p);
   p += 2;
   *p++ = ' ';
-  absl::numbers_internal::PutTwoDigits(static_cast<size_t>(ci.cs.hour()), p);
+  absl::numbers_internal::PutTwoDigits(static_cast<uint32_t>(ci.cs.hour()), p);
   p += 2;
   *p++ = ':';
-  absl::numbers_internal::PutTwoDigits(static_cast<size_t>(ci.cs.minute()), p);
+  absl::numbers_internal::PutTwoDigits(static_cast<uint32_t>(ci.cs.minute()),
+                                       p);
   p += 2;
   *p++ = ':';
-  absl::numbers_internal::PutTwoDigits(static_cast<size_t>(ci.cs.second()), p);
+  absl::numbers_internal::PutTwoDigits(static_cast<uint32_t>(ci.cs.second()),
+                                       p);
   p += 2;
   *p++ = '.';
   const int64_t usecs = absl::ToInt64Microseconds(ci.subsecond);
-  absl::numbers_internal::PutTwoDigits(static_cast<size_t>(usecs / 10000), p);
+  absl::numbers_internal::PutTwoDigits(static_cast<uint32_t>(usecs / 10000), p);
   p += 2;
-  absl::numbers_internal::PutTwoDigits(static_cast<size_t>(usecs / 100 % 100),
+  absl::numbers_internal::PutTwoDigits(static_cast<uint32_t>(usecs / 100 % 100),
                                        p);
   p += 2;
-  absl::numbers_internal::PutTwoDigits(static_cast<size_t>(usecs % 100), p);
+  absl::numbers_internal::PutTwoDigits(static_cast<uint32_t>(usecs % 100), p);
   p += 2;
   *p++ = ' ';
   PutLeadingWhitespace(tid, p);
diff --git a/absl/log/internal/log_impl.h b/absl/log/internal/log_impl.h
index 82b5ed84..9326780d 100644
--- a/absl/log/internal/log_impl.h
+++ b/absl/log/internal/log_impl.h
@@ -20,190 +20,194 @@
 #include "absl/log/internal/strip.h"
 
 // ABSL_LOG()
-#define ABSL_LOG_IMPL(severity)                          \
+#define ABSL_LOG_INTERNAL_LOG_IMPL(severity)             \
   ABSL_LOG_INTERNAL_CONDITION##severity(STATELESS, true) \
       ABSL_LOGGING_INTERNAL_LOG##severity.InternalStream()
 
 // ABSL_PLOG()
-#define ABSL_PLOG_IMPL(severity)                           \
+#define ABSL_LOG_INTERNAL_PLOG_IMPL(severity)              \
   ABSL_LOG_INTERNAL_CONDITION##severity(STATELESS, true)   \
       ABSL_LOGGING_INTERNAL_LOG##severity.InternalStream() \
           .WithPerror()
 
 // ABSL_DLOG()
 #ifndef NDEBUG
-#define ABSL_DLOG_IMPL(severity)                         \
+#define ABSL_LOG_INTERNAL_DLOG_IMPL(severity)            \
   ABSL_LOG_INTERNAL_CONDITION##severity(STATELESS, true) \
       ABSL_LOGGING_INTERNAL_LOG##severity.InternalStream()
 #else
-#define ABSL_DLOG_IMPL(severity)                          \
+#define ABSL_LOG_INTERNAL_DLOG_IMPL(severity)             \
   ABSL_LOG_INTERNAL_CONDITION##severity(STATELESS, false) \
       ABSL_LOGGING_INTERNAL_LOG##severity.InternalStream()
 #endif
 
-#define ABSL_LOG_IF_IMPL(severity, condition)                 \
+#define ABSL_LOG_INTERNAL_LOG_IF_IMPL(severity, condition)    \
   ABSL_LOG_INTERNAL_CONDITION##severity(STATELESS, condition) \
       ABSL_LOGGING_INTERNAL_LOG##severity.InternalStream()
-#define ABSL_PLOG_IF_IMPL(severity, condition)                \
+#define ABSL_LOG_INTERNAL_PLOG_IF_IMPL(severity, condition)   \
   ABSL_LOG_INTERNAL_CONDITION##severity(STATELESS, condition) \
       ABSL_LOGGING_INTERNAL_LOG##severity.InternalStream()    \
           .WithPerror()
 
 #ifndef NDEBUG
-#define ABSL_DLOG_IF_IMPL(severity, condition)                \
+#define ABSL_LOG_INTERNAL_DLOG_IF_IMPL(severity, condition)   \
   ABSL_LOG_INTERNAL_CONDITION##severity(STATELESS, condition) \
       ABSL_LOGGING_INTERNAL_LOG##severity.InternalStream()
 #else
-#define ABSL_DLOG_IF_IMPL(severity, condition)                           \
+#define ABSL_LOG_INTERNAL_DLOG_IF_IMPL(severity, condition)              \
   ABSL_LOG_INTERNAL_CONDITION##severity(STATELESS, false && (condition)) \
       ABSL_LOGGING_INTERNAL_LOG##severity.InternalStream()
 #endif
 
 // ABSL_LOG_EVERY_N
-#define ABSL_LOG_EVERY_N_IMPL(severity, n)                         \
+#define ABSL_LOG_INTERNAL_LOG_EVERY_N_IMPL(severity, n)            \
   ABSL_LOG_INTERNAL_CONDITION##severity(STATEFUL, true)(EveryN, n) \
       ABSL_LOGGING_INTERNAL_LOG##severity.InternalStream()
 
 // ABSL_LOG_FIRST_N
-#define ABSL_LOG_FIRST_N_IMPL(severity, n)                         \
+#define ABSL_LOG_INTERNAL_LOG_FIRST_N_IMPL(severity, n)            \
   ABSL_LOG_INTERNAL_CONDITION##severity(STATEFUL, true)(FirstN, n) \
       ABSL_LOGGING_INTERNAL_LOG##severity.InternalStream()
 
 // ABSL_LOG_EVERY_POW_2
-#define ABSL_LOG_EVERY_POW_2_IMPL(severity)                        \
+#define ABSL_LOG_INTERNAL_LOG_EVERY_POW_2_IMPL(severity)           \
   ABSL_LOG_INTERNAL_CONDITION##severity(STATEFUL, true)(EveryPow2) \
       ABSL_LOGGING_INTERNAL_LOG##severity.InternalStream()
 
 // ABSL_LOG_EVERY_N_SEC
-#define ABSL_LOG_EVERY_N_SEC_IMPL(severity, n_seconds)                        \
+#define ABSL_LOG_INTERNAL_LOG_EVERY_N_SEC_IMPL(severity, n_seconds)           \
   ABSL_LOG_INTERNAL_CONDITION##severity(STATEFUL, true)(EveryNSec, n_seconds) \
       ABSL_LOGGING_INTERNAL_LOG##severity.InternalStream()
 
-#define ABSL_PLOG_EVERY_N_IMPL(severity, n)                        \
+#define ABSL_LOG_INTERNAL_PLOG_EVERY_N_IMPL(severity, n)           \
   ABSL_LOG_INTERNAL_CONDITION##severity(STATEFUL, true)(EveryN, n) \
       ABSL_LOGGING_INTERNAL_LOG##severity.InternalStream()         \
           .WithPerror()
 
-#define ABSL_PLOG_FIRST_N_IMPL(severity, n)                        \
+#define ABSL_LOG_INTERNAL_PLOG_FIRST_N_IMPL(severity, n)           \
   ABSL_LOG_INTERNAL_CONDITION##severity(STATEFUL, true)(FirstN, n) \
       ABSL_LOGGING_INTERNAL_LOG##severity.InternalStream()         \
           .WithPerror()
 
-#define ABSL_PLOG_EVERY_POW_2_IMPL(severity)                       \
+#define ABSL_LOG_INTERNAL_PLOG_EVERY_POW_2_IMPL(severity)          \
   ABSL_LOG_INTERNAL_CONDITION##severity(STATEFUL, true)(EveryPow2) \
       ABSL_LOGGING_INTERNAL_LOG##severity.InternalStream()         \
           .WithPerror()
 
-#define ABSL_PLOG_EVERY_N_SEC_IMPL(severity, n_seconds)                       \
+#define ABSL_LOG_INTERNAL_PLOG_EVERY_N_SEC_IMPL(severity, n_seconds)          \
   ABSL_LOG_INTERNAL_CONDITION##severity(STATEFUL, true)(EveryNSec, n_seconds) \
       ABSL_LOGGING_INTERNAL_LOG##severity.InternalStream()                    \
           .WithPerror()
 
 #ifndef NDEBUG
-#define ABSL_DLOG_EVERY_N_IMPL(severity, n)        \
-  ABSL_LOG_INTERNAL_CONDITION_INFO(STATEFUL, true) \
+#define ABSL_LOG_INTERNAL_DLOG_EVERY_N_IMPL(severity, n) \
+  ABSL_LOG_INTERNAL_CONDITION_INFO(STATEFUL, true)       \
   (EveryN, n) ABSL_LOGGING_INTERNAL_LOG##severity.InternalStream()
 
-#define ABSL_DLOG_FIRST_N_IMPL(severity, n)        \
-  ABSL_LOG_INTERNAL_CONDITION_INFO(STATEFUL, true) \
+#define ABSL_LOG_INTERNAL_DLOG_FIRST_N_IMPL(severity, n) \
+  ABSL_LOG_INTERNAL_CONDITION_INFO(STATEFUL, true)       \
   (FirstN, n) ABSL_LOGGING_INTERNAL_LOG##severity.InternalStream()
 
-#define ABSL_DLOG_EVERY_POW_2_IMPL(severity)       \
-  ABSL_LOG_INTERNAL_CONDITION_INFO(STATEFUL, true) \
+#define ABSL_LOG_INTERNAL_DLOG_EVERY_POW_2_IMPL(severity) \
+  ABSL_LOG_INTERNAL_CONDITION_INFO(STATEFUL, true)        \
   (EveryPow2) ABSL_LOGGING_INTERNAL_LOG##severity.InternalStream()
 
-#define ABSL_DLOG_EVERY_N_SEC_IMPL(severity, n_seconds) \
-  ABSL_LOG_INTERNAL_CONDITION_INFO(STATEFUL, true)      \
+#define ABSL_LOG_INTERNAL_DLOG_EVERY_N_SEC_IMPL(severity, n_seconds) \
+  ABSL_LOG_INTERNAL_CONDITION_INFO(STATEFUL, true)                   \
   (EveryNSec, n_seconds) ABSL_LOGGING_INTERNAL_LOG##severity.InternalStream()
 
 #else  // def NDEBUG
-#define ABSL_DLOG_EVERY_N_IMPL(severity, n)         \
-  ABSL_LOG_INTERNAL_CONDITION_INFO(STATEFUL, false) \
+#define ABSL_LOG_INTERNAL_DLOG_EVERY_N_IMPL(severity, n) \
+  ABSL_LOG_INTERNAL_CONDITION_INFO(STATEFUL, false)      \
   (EveryN, n) ABSL_LOGGING_INTERNAL_LOG##severity.InternalStream()
 
-#define ABSL_DLOG_FIRST_N_IMPL(severity, n)         \
-  ABSL_LOG_INTERNAL_CONDITION_INFO(STATEFUL, false) \
+#define ABSL_LOG_INTERNAL_DLOG_FIRST_N_IMPL(severity, n) \
+  ABSL_LOG_INTERNAL_CONDITION_INFO(STATEFUL, false)      \
   (FirstN, n) ABSL_LOGGING_INTERNAL_LOG##severity.InternalStream()
 
-#define ABSL_DLOG_EVERY_POW_2_IMPL(severity)        \
-  ABSL_LOG_INTERNAL_CONDITION_INFO(STATEFUL, false) \
+#define ABSL_LOG_INTERNAL_DLOG_EVERY_POW_2_IMPL(severity) \
+  ABSL_LOG_INTERNAL_CONDITION_INFO(STATEFUL, false)       \
   (EveryPow2) ABSL_LOGGING_INTERNAL_LOG##severity.InternalStream()
 
-#define ABSL_DLOG_EVERY_N_SEC_IMPL(severity, n_seconds) \
-  ABSL_LOG_INTERNAL_CONDITION_INFO(STATEFUL, false)     \
+#define ABSL_LOG_INTERNAL_DLOG_EVERY_N_SEC_IMPL(severity, n_seconds) \
+  ABSL_LOG_INTERNAL_CONDITION_INFO(STATEFUL, false)                  \
   (EveryNSec, n_seconds) ABSL_LOGGING_INTERNAL_LOG##severity.InternalStream()
 #endif  // def NDEBUG
 
-#define ABSL_LOG_IF_EVERY_N_IMPL(severity, condition, n)                \
+#define ABSL_LOG_INTERNAL_LOG_IF_EVERY_N_IMPL(severity, condition, n)   \
   ABSL_LOG_INTERNAL_CONDITION##severity(STATEFUL, condition)(EveryN, n) \
       ABSL_LOGGING_INTERNAL_LOG##severity.InternalStream()
 
-#define ABSL_LOG_IF_FIRST_N_IMPL(severity, condition, n)                \
+#define ABSL_LOG_INTERNAL_LOG_IF_FIRST_N_IMPL(severity, condition, n)   \
   ABSL_LOG_INTERNAL_CONDITION##severity(STATEFUL, condition)(FirstN, n) \
       ABSL_LOGGING_INTERNAL_LOG##severity.InternalStream()
 
-#define ABSL_LOG_IF_EVERY_POW_2_IMPL(severity, condition)               \
+#define ABSL_LOG_INTERNAL_LOG_IF_EVERY_POW_2_IMPL(severity, condition)  \
   ABSL_LOG_INTERNAL_CONDITION##severity(STATEFUL, condition)(EveryPow2) \
       ABSL_LOGGING_INTERNAL_LOG##severity.InternalStream()
 
-#define ABSL_LOG_IF_EVERY_N_SEC_IMPL(severity, condition, n_seconds)    \
+#define ABSL_LOG_INTERNAL_LOG_IF_EVERY_N_SEC_IMPL(severity, condition,  \
+                                                  n_seconds)            \
   ABSL_LOG_INTERNAL_CONDITION##severity(STATEFUL, condition)(EveryNSec, \
                                                              n_seconds) \
       ABSL_LOGGING_INTERNAL_LOG##severity.InternalStream()
 
-#define ABSL_PLOG_IF_EVERY_N_IMPL(severity, condition, n)               \
+#define ABSL_LOG_INTERNAL_PLOG_IF_EVERY_N_IMPL(severity, condition, n)  \
   ABSL_LOG_INTERNAL_CONDITION##severity(STATEFUL, condition)(EveryN, n) \
       ABSL_LOGGING_INTERNAL_LOG##severity.InternalStream()              \
           .WithPerror()
 
-#define ABSL_PLOG_IF_FIRST_N_IMPL(severity, condition, n)               \
+#define ABSL_LOG_INTERNAL_PLOG_IF_FIRST_N_IMPL(severity, condition, n)  \
   ABSL_LOG_INTERNAL_CONDITION##severity(STATEFUL, condition)(FirstN, n) \
       ABSL_LOGGING_INTERNAL_LOG##severity.InternalStream()              \
           .WithPerror()
 
-#define ABSL_PLOG_IF_EVERY_POW_2_IMPL(severity, condition)              \
+#define ABSL_LOG_INTERNAL_PLOG_IF_EVERY_POW_2_IMPL(severity, condition) \
   ABSL_LOG_INTERNAL_CONDITION##severity(STATEFUL, condition)(EveryPow2) \
       ABSL_LOGGING_INTERNAL_LOG##severity.InternalStream()              \
           .WithPerror()
 
-#define ABSL_PLOG_IF_EVERY_N_SEC_IMPL(severity, condition, n_seconds)   \
+#define ABSL_LOG_INTERNAL_PLOG_IF_EVERY_N_SEC_IMPL(severity, condition, \
+                                                   n_seconds)           \
   ABSL_LOG_INTERNAL_CONDITION##severity(STATEFUL, condition)(EveryNSec, \
                                                              n_seconds) \
       ABSL_LOGGING_INTERNAL_LOG##severity.InternalStream()              \
           .WithPerror()
 
 #ifndef NDEBUG
-#define ABSL_DLOG_IF_EVERY_N_IMPL(severity, condition, n)               \
+#define ABSL_LOG_INTERNAL_DLOG_IF_EVERY_N_IMPL(severity, condition, n)  \
   ABSL_LOG_INTERNAL_CONDITION##severity(STATEFUL, condition)(EveryN, n) \
       ABSL_LOGGING_INTERNAL_LOG##severity.InternalStream()
 
-#define ABSL_DLOG_IF_FIRST_N_IMPL(severity, condition, n)               \
+#define ABSL_LOG_INTERNAL_DLOG_IF_FIRST_N_IMPL(severity, condition, n)  \
   ABSL_LOG_INTERNAL_CONDITION##severity(STATEFUL, condition)(FirstN, n) \
       ABSL_LOGGING_INTERNAL_LOG##severity.InternalStream()
 
-#define ABSL_DLOG_IF_EVERY_POW_2_IMPL(severity, condition)              \
+#define ABSL_LOG_INTERNAL_DLOG_IF_EVERY_POW_2_IMPL(severity, condition) \
   ABSL_LOG_INTERNAL_CONDITION##severity(STATEFUL, condition)(EveryPow2) \
       ABSL_LOGGING_INTERNAL_LOG##severity.InternalStream()
 
-#define ABSL_DLOG_IF_EVERY_N_SEC_IMPL(severity, condition, n_seconds)   \
+#define ABSL_LOG_INTERNAL_DLOG_IF_EVERY_N_SEC_IMPL(severity, condition, \
+                                                   n_seconds)           \
   ABSL_LOG_INTERNAL_CONDITION##severity(STATEFUL, condition)(EveryNSec, \
                                                              n_seconds) \
       ABSL_LOGGING_INTERNAL_LOG##severity.InternalStream()
 
 #else  // def NDEBUG
-#define ABSL_DLOG_IF_EVERY_N_IMPL(severity, condition, n)                \
+#define ABSL_LOG_INTERNAL_DLOG_IF_EVERY_N_IMPL(severity, condition, n)   \
   ABSL_LOG_INTERNAL_CONDITION##severity(STATEFUL, false && (condition))( \
       EveryN, n) ABSL_LOGGING_INTERNAL_LOG##severity.InternalStream()
 
-#define ABSL_DLOG_IF_FIRST_N_IMPL(severity, condition, n)                \
+#define ABSL_LOG_INTERNAL_DLOG_IF_FIRST_N_IMPL(severity, condition, n)   \
   ABSL_LOG_INTERNAL_CONDITION##severity(STATEFUL, false && (condition))( \
       FirstN, n) ABSL_LOGGING_INTERNAL_LOG##severity.InternalStream()
 
-#define ABSL_DLOG_IF_EVERY_POW_2_IMPL(severity, condition)               \
+#define ABSL_LOG_INTERNAL_DLOG_IF_EVERY_POW_2_IMPL(severity, condition)  \
   ABSL_LOG_INTERNAL_CONDITION##severity(STATEFUL, false && (condition))( \
       EveryPow2) ABSL_LOGGING_INTERNAL_LOG##severity.InternalStream()
 
-#define ABSL_DLOG_IF_EVERY_N_SEC_IMPL(severity, condition, n_seconds)    \
+#define ABSL_LOG_INTERNAL_DLOG_IF_EVERY_N_SEC_IMPL(severity, condition,  \
+                                                   n_seconds)            \
   ABSL_LOG_INTERNAL_CONDITION##severity(STATEFUL, false && (condition))( \
       EveryNSec, n_seconds)                                              \
       ABSL_LOGGING_INTERNAL_LOG##severity.InternalStream()
diff --git a/absl/log/internal/log_message.cc b/absl/log/internal/log_message.cc
index bdb10f2a..10ac2453 100644
--- a/absl/log/internal/log_message.cc
+++ b/absl/log/internal/log_message.cc
@@ -234,6 +234,13 @@ LogMessage::LogMessage(const char* file, int line, absl::LogSeverity severity)
   LogBacktraceIfNeeded();
 }
 
+LogMessage::LogMessage(const char* file, int line, InfoTag)
+    : LogMessage(file, line, absl::LogSeverity::kInfo) {}
+LogMessage::LogMessage(const char* file, int line, WarningTag)
+    : LogMessage(file, line, absl::LogSeverity::kWarning) {}
+LogMessage::LogMessage(const char* file, int line, ErrorTag)
+    : LogMessage(file, line, absl::LogSeverity::kError) {}
+
 LogMessage::~LogMessage() {
 #ifdef ABSL_MIN_LOG_LEVEL
   if (data_->entry.log_severity() <
@@ -346,12 +353,12 @@ void LogMessage::FailQuietly() {
 }
 
 LogMessage& LogMessage::operator<<(const std::string& v) {
-  CopyToEncodedBuffer(v, StringType::kNotLiteral);
+  CopyToEncodedBuffer<StringType::kNotLiteral>(v);
   return *this;
 }
 
 LogMessage& LogMessage::operator<<(absl::string_view v) {
-  CopyToEncodedBuffer(v, StringType::kNotLiteral);
+  CopyToEncodedBuffer<StringType::kNotLiteral>(v);
   return *this;
 }
 LogMessage& LogMessage::operator<<(std::ostream& (*m)(std::ostream& os)) {
@@ -383,8 +390,7 @@ template LogMessage& LogMessage::operator<<(const double& v);
 template LogMessage& LogMessage::operator<<(const bool& v);
 
 void LogMessage::Flush() {
-  if (data_->entry.log_severity() < absl::MinLogLevel())
-    return;
+  if (data_->entry.log_severity() < absl::MinLogLevel()) return;
 
   if (data_->is_perror) {
     InternalStream() << ": " << absl::base_internal::StrError(errno_saver_())
@@ -427,7 +433,7 @@ LogMessage::OstreamView::OstreamView(LogMessageData& message_data)
                          &encoded_remaining_copy_);
   string_start_ =
       EncodeMessageStart(ValueTag::kString, encoded_remaining_copy_.size(),
-                       &encoded_remaining_copy_);
+                         &encoded_remaining_copy_);
   setp(encoded_remaining_copy_.data(),
        encoded_remaining_copy_.data() + encoded_remaining_copy_.size());
   data_.manipulated.rdbuf(this);
@@ -519,8 +525,8 @@ void LogMessage::LogBacktraceIfNeeded() {
 // containing the specified string data using a `Value` field appropriate to
 // `str_type`.  Truncates `str` if necessary, but emits nothing and marks the
 // buffer full if  even the field headers do not fit.
-void LogMessage::CopyToEncodedBuffer(absl::string_view str,
-                                     StringType str_type) {
+template <LogMessage::StringType str_type>
+void LogMessage::CopyToEncodedBuffer(absl::string_view str) {
   auto encoded_remaining_copy = data_->encoded_remaining;
   auto start = EncodeMessageStart(
       EventTag::kValue, BufferSizeFor(WireType::kLengthDelimited) + str.size(),
@@ -541,7 +547,12 @@ void LogMessage::CopyToEncodedBuffer(absl::string_view str,
     data_->encoded_remaining.remove_suffix(data_->encoded_remaining.size());
   }
 }
-void LogMessage::CopyToEncodedBuffer(char ch, size_t num, StringType str_type) {
+template void LogMessage::CopyToEncodedBuffer<LogMessage::StringType::kLiteral>(
+    absl::string_view str);
+template void LogMessage::CopyToEncodedBuffer<
+    LogMessage::StringType::kNotLiteral>(absl::string_view str);
+template <LogMessage::StringType str_type>
+void LogMessage::CopyToEncodedBuffer(char ch, size_t num) {
   auto encoded_remaining_copy = data_->encoded_remaining;
   auto value_start = EncodeMessageStart(
       EventTag::kValue, BufferSizeFor(WireType::kLengthDelimited) + num,
@@ -562,6 +573,10 @@ void LogMessage::CopyToEncodedBuffer(char ch, size_t num, StringType str_type) {
     data_->encoded_remaining.remove_suffix(data_->encoded_remaining.size());
   }
 }
+template void LogMessage::CopyToEncodedBuffer<LogMessage::StringType::kLiteral>(
+    char ch, size_t num);
+template void LogMessage::CopyToEncodedBuffer<
+    LogMessage::StringType::kNotLiteral>(char ch, size_t num);
 
 LogMessageFatal::LogMessageFatal(const char* file, int line)
     : LogMessage(file, line, absl::LogSeverity::kFatal) {}
diff --git a/absl/log/internal/log_message.h b/absl/log/internal/log_message.h
index 3744276b..46937728 100644
--- a/absl/log/internal/log_message.h
+++ b/absl/log/internal/log_message.h
@@ -51,9 +51,21 @@ constexpr int kLogMessageBufferSize = 15000;
 
 class LogMessage {
  public:
+  struct InfoTag {};
+  struct WarningTag {};
+  struct ErrorTag {};
+
   // Used for `LOG`.
   LogMessage(const char* file, int line,
              absl::LogSeverity severity) ABSL_ATTRIBUTE_COLD;
+  // These constructors are slightly smaller/faster to call; the severity is
+  // curried into the function pointer.
+  LogMessage(const char* file, int line,
+             InfoTag) ABSL_ATTRIBUTE_COLD ABSL_ATTRIBUTE_NOINLINE;
+  LogMessage(const char* file, int line,
+             WarningTag) ABSL_ATTRIBUTE_COLD ABSL_ATTRIBUTE_NOINLINE;
+  LogMessage(const char* file, int line,
+             ErrorTag) ABSL_ATTRIBUTE_COLD ABSL_ATTRIBUTE_NOINLINE;
   LogMessage(const LogMessage&) = delete;
   LogMessage& operator=(const LogMessage&) = delete;
   ~LogMessage() ABSL_ATTRIBUTE_COLD;
@@ -219,10 +231,10 @@ class LogMessage {
     kLiteral,
     kNotLiteral,
   };
-  void CopyToEncodedBuffer(absl::string_view str,
-                           StringType str_type) ABSL_ATTRIBUTE_NOINLINE;
-  void CopyToEncodedBuffer(char ch, size_t num,
-                           StringType str_type) ABSL_ATTRIBUTE_NOINLINE;
+  template <StringType str_type>
+  void CopyToEncodedBuffer(absl::string_view str) ABSL_ATTRIBUTE_NOINLINE;
+  template <StringType str_type>
+  void CopyToEncodedBuffer(char ch, size_t num) ABSL_ATTRIBUTE_NOINLINE;
 
   // Returns `true` if the message is fatal or enabled debug-fatal.
   bool IsFatal() const;
@@ -252,12 +264,12 @@ class StringifySink final {
   explicit StringifySink(LogMessage& message) : message_(message) {}
 
   void Append(size_t count, char ch) {
-    message_.CopyToEncodedBuffer(ch, count,
-                                 LogMessage::StringType::kNotLiteral);
+    message_.CopyToEncodedBuffer<LogMessage::StringType::kNotLiteral>(ch,
+                                                                      count);
   }
 
   void Append(absl::string_view v) {
-    message_.CopyToEncodedBuffer(v, LogMessage::StringType::kNotLiteral);
+    message_.CopyToEncodedBuffer<LogMessage::StringType::kNotLiteral>(v);
   }
 
   // For types that implement `AbslStringify` using `absl::Format()`.
@@ -292,14 +304,14 @@ LogMessage& LogMessage::operator<<(const T& v) {
 
 template <int SIZE>
 LogMessage& LogMessage::operator<<(const char (&buf)[SIZE]) {
-  CopyToEncodedBuffer(buf, StringType::kLiteral);
+  CopyToEncodedBuffer<StringType::kLiteral>(buf);
   return *this;
 }
 
 // Note: the following is declared `ABSL_ATTRIBUTE_NOINLINE`
 template <int SIZE>
 LogMessage& LogMessage::operator<<(char (&buf)[SIZE]) {
-  CopyToEncodedBuffer(buf, StringType::kNotLiteral);
+  CopyToEncodedBuffer<StringType::kNotLiteral>(buf);
   return *this;
 }
 // We instantiate these specializations in the library's TU to save space in
@@ -327,6 +339,16 @@ extern template LogMessage& LogMessage::operator<<(const float& v);
 extern template LogMessage& LogMessage::operator<<(const double& v);
 extern template LogMessage& LogMessage::operator<<(const bool& v);
 
+extern template void LogMessage::CopyToEncodedBuffer<
+    LogMessage::StringType::kLiteral>(absl::string_view str);
+extern template void LogMessage::CopyToEncodedBuffer<
+    LogMessage::StringType::kNotLiteral>(absl::string_view str);
+extern template void
+LogMessage::CopyToEncodedBuffer<LogMessage::StringType::kLiteral>(char ch,
+                                                                  size_t num);
+extern template void LogMessage::CopyToEncodedBuffer<
+    LogMessage::StringType::kNotLiteral>(char ch, size_t num);
+
 // `LogMessageFatal` ensures the process will exit in failure after logging this
 // message.
 class LogMessageFatal final : public LogMessage {
diff --git a/absl/log/internal/log_sink_set.cc b/absl/log/internal/log_sink_set.cc
index f9d030aa..b7cbe364 100644
--- a/absl/log/internal/log_sink_set.cc
+++ b/absl/log/internal/log_sink_set.cc
@@ -122,11 +122,11 @@ class AndroidLogSink final : public LogSink {
 
   void Send(const absl::LogEntry& entry) override {
     const int level = AndroidLogLevel(entry);
-    // TODO(b/37587197): make the tag ("native") configurable.
-    __android_log_write(level, "native",
+    const char* const tag = GetAndroidNativeTag();
+    __android_log_write(level, tag,
                         entry.text_message_with_prefix_and_newline_c_str());
     if (entry.log_severity() == absl::LogSeverity::kFatal)
-      __android_log_write(ANDROID_LOG_FATAL, "native", "terminating.\n");
+      __android_log_write(ANDROID_LOG_FATAL, tag, "terminating.\n");
   }
 
  private:
diff --git a/absl/log/internal/nullguard.cc b/absl/log/internal/nullguard.cc
index 4f2f9d40..3296c014 100644
--- a/absl/log/internal/nullguard.cc
+++ b/absl/log/internal/nullguard.cc
@@ -23,11 +23,11 @@ namespace absl {
 ABSL_NAMESPACE_BEGIN
 namespace log_internal {
 
-ABSL_DLL ABSL_CONST_INIT const std::array<char, 7> kCharNull{
+ABSL_CONST_INIT ABSL_DLL const std::array<char, 7> kCharNull{
     {'(', 'n', 'u', 'l', 'l', ')', '\0'}};
-ABSL_DLL ABSL_CONST_INIT const std::array<signed char, 7> kSignedCharNull{
+ABSL_CONST_INIT ABSL_DLL const std::array<signed char, 7> kSignedCharNull{
     {'(', 'n', 'u', 'l', 'l', ')', '\0'}};
-ABSL_DLL ABSL_CONST_INIT const std::array<unsigned char, 7> kUnsignedCharNull{
+ABSL_CONST_INIT ABSL_DLL const std::array<unsigned char, 7> kUnsignedCharNull{
     {'(', 'n', 'u', 'l', 'l', ')', '\0'}};
 
 }  // namespace log_internal
diff --git a/absl/log/internal/nullguard.h b/absl/log/internal/nullguard.h
index 926f61bb..623943c5 100644
--- a/absl/log/internal/nullguard.h
+++ b/absl/log/internal/nullguard.h
@@ -34,10 +34,10 @@ namespace absl {
 ABSL_NAMESPACE_BEGIN
 namespace log_internal {
 
-ABSL_DLL ABSL_CONST_INIT extern const std::array<char, 7> kCharNull;
-ABSL_DLL ABSL_CONST_INIT extern const std::array<signed char, 7>
+ABSL_CONST_INIT ABSL_DLL extern const std::array<char, 7> kCharNull;
+ABSL_CONST_INIT ABSL_DLL extern const std::array<signed char, 7>
     kSignedCharNull;
-ABSL_DLL ABSL_CONST_INIT extern const std::array<unsigned char, 7>
+ABSL_CONST_INIT ABSL_DLL extern const std::array<unsigned char, 7>
     kUnsignedCharNull;
 
 template <typename T>
diff --git a/absl/log/internal/nullstream.h b/absl/log/internal/nullstream.h
index 8ed63d52..9266852e 100644
--- a/absl/log/internal/nullstream.h
+++ b/absl/log/internal/nullstream.h
@@ -102,7 +102,9 @@ class NullStreamMaybeFatal final : public NullStream {
   explicit NullStreamMaybeFatal(absl::LogSeverity severity)
       : fatal_(severity == absl::LogSeverity::kFatal) {}
   ~NullStreamMaybeFatal() {
-    if (fatal_) _exit(1);
+    if (fatal_) {
+      _exit(1);
+    }
   }
 
  private:
@@ -114,7 +116,7 @@ class NullStreamMaybeFatal final : public NullStream {
 // and expression-defined severity use `NullStreamMaybeFatal` above.
 class NullStreamFatal final : public NullStream {
  public:
-  NullStreamFatal() {}
+  NullStreamFatal() = default;
   // ABSL_ATTRIBUTE_NORETURN doesn't seem to work on destructors with msvc, so
   // disable msvc's warning about the d'tor never returning.
 #if defined(_MSC_VER) && !defined(__clang__)
diff --git a/absl/log/internal/strip.h b/absl/log/internal/strip.h
index 848c3867..adc86ffd 100644
--- a/absl/log/internal/strip.h
+++ b/absl/log/internal/strip.h
@@ -42,15 +42,15 @@
 #define ABSL_LOG_INTERNAL_QCHECK(failure_message) \
   ABSL_LOGGING_INTERNAL_LOG_QFATAL
 #else  // !defined(STRIP_LOG) || !STRIP_LOG
-#define ABSL_LOGGING_INTERNAL_LOG_INFO                 \
-  ::absl::log_internal::LogMessage(__FILE__, __LINE__, \
-                                   ::absl::LogSeverity::kInfo)
-#define ABSL_LOGGING_INTERNAL_LOG_WARNING              \
-  ::absl::log_internal::LogMessage(__FILE__, __LINE__, \
-                                   ::absl::LogSeverity::kWarning)
-#define ABSL_LOGGING_INTERNAL_LOG_ERROR                \
-  ::absl::log_internal::LogMessage(__FILE__, __LINE__, \
-                                   ::absl::LogSeverity::kError)
+#define ABSL_LOGGING_INTERNAL_LOG_INFO \
+  ::absl::log_internal::LogMessage(    \
+      __FILE__, __LINE__, ::absl::log_internal::LogMessage::InfoTag{})
+#define ABSL_LOGGING_INTERNAL_LOG_WARNING \
+  ::absl::log_internal::LogMessage(       \
+      __FILE__, __LINE__, ::absl::log_internal::LogMessage::WarningTag{})
+#define ABSL_LOGGING_INTERNAL_LOG_ERROR \
+  ::absl::log_internal::LogMessage(     \
+      __FILE__, __LINE__, ::absl::log_internal::LogMessage::ErrorTag{})
 #define ABSL_LOGGING_INTERNAL_LOG_FATAL \
   ::absl::log_internal::LogMessageFatal(__FILE__, __LINE__)
 #define ABSL_LOGGING_INTERNAL_LOG_QFATAL \
diff --git a/absl/log/internal/structured.h b/absl/log/internal/structured.h
index 08caea66..5223dbc3 100644
--- a/absl/log/internal/structured.h
+++ b/absl/log/internal/structured.h
@@ -42,7 +42,7 @@ class ABSL_MUST_USE_RESULT AsLiteralImpl final {
     return os << as_literal.str_;
   }
   void AddToMessage(log_internal::LogMessage& m) {
-    m.CopyToEncodedBuffer(str_, log_internal::LogMessage::StringType::kLiteral);
+    m.CopyToEncodedBuffer<log_internal::LogMessage::StringType::kLiteral>(str_);
   }
   friend log_internal::LogMessage& operator<<(log_internal::LogMessage& m,
                                               AsLiteralImpl as_literal) {
diff --git a/absl/log/internal/test_helpers.cc b/absl/log/internal/test_helpers.cc
index 0de5b96b..bfcc9679 100644
--- a/absl/log/internal/test_helpers.cc
+++ b/absl/log/internal/test_helpers.cc
@@ -68,7 +68,7 @@ bool DiedOfQFatal(int exit_status) {
 #endif
 
 // -----------------------------------------------------------------------------
-// Helper for Log inititalization in test
+// Helper for Log initialization in test
 // -----------------------------------------------------------------------------
 
 void LogTestEnvironment::SetUp() {
diff --git a/absl/log/internal/test_helpers.h b/absl/log/internal/test_helpers.h
index fd06e295..714bc7bd 100644
--- a/absl/log/internal/test_helpers.h
+++ b/absl/log/internal/test_helpers.h
@@ -54,7 +54,7 @@ bool DiedOfQFatal(int exit_status);
 #endif
 
 // -----------------------------------------------------------------------------
-// Helper for Log inititalization in test
+// Helper for Log initialization in test
 // -----------------------------------------------------------------------------
 
 class LogTestEnvironment : public ::testing::Environment {
diff --git a/absl/log/log.h b/absl/log/log.h
index e060a0b6..602b5acf 100644
--- a/absl/log/log.h
+++ b/absl/log/log.h
@@ -196,29 +196,32 @@
 // Example:
 //
 //   LOG(INFO) << "Found " << num_cookies << " cookies";
-#define LOG(severity) ABSL_LOG_IMPL(_##severity)
+#define LOG(severity) ABSL_LOG_INTERNAL_LOG_IMPL(_##severity)
 
 // PLOG()
 //
 // `PLOG` behaves like `LOG` except that a description of the current state of
 // `errno` is appended to the streamed message.
-#define PLOG(severity) ABSL_PLOG_IMPL(_##severity)
+#define PLOG(severity) ABSL_LOG_INTERNAL_PLOG_IMPL(_##severity)
 
 // DLOG()
 //
 // `DLOG` behaves like `LOG` in debug mode (i.e. `#ifndef NDEBUG`).  Otherwise
 // it compiles away and does nothing.  Note that `DLOG(FATAL)` does not
 // terminate the program if `NDEBUG` is defined.
-#define DLOG(severity) ABSL_DLOG_IMPL(_##severity)
+#define DLOG(severity) ABSL_LOG_INTERNAL_DLOG_IMPL(_##severity)
 
 // `LOG_IF` and friends add a second argument which specifies a condition.  If
 // the condition is false, nothing is logged.
 // Example:
 //
 //   LOG_IF(INFO, num_cookies > 10) << "Got lots of cookies";
-#define LOG_IF(severity, condition) ABSL_LOG_IF_IMPL(_##severity, condition)
-#define PLOG_IF(severity, condition) ABSL_PLOG_IF_IMPL(_##severity, condition)
-#define DLOG_IF(severity, condition) ABSL_DLOG_IF_IMPL(_##severity, condition)
+#define LOG_IF(severity, condition) \
+  ABSL_LOG_INTERNAL_LOG_IF_IMPL(_##severity, condition)
+#define PLOG_IF(severity, condition) \
+  ABSL_LOG_INTERNAL_PLOG_IF_IMPL(_##severity, condition)
+#define DLOG_IF(severity, condition) \
+  ABSL_LOG_INTERNAL_DLOG_IF_IMPL(_##severity, condition)
 
 // LOG_EVERY_N
 //
@@ -231,21 +234,24 @@
 //
 //   LOG_EVERY_N(WARNING, 1000) << "Got a packet with a bad CRC (" << COUNTER
 //                              << " total)";
-#define LOG_EVERY_N(severity, n) ABSL_LOG_EVERY_N_IMPL(_##severity, n)
+#define LOG_EVERY_N(severity, n) \
+  ABSL_LOG_INTERNAL_LOG_EVERY_N_IMPL(_##severity, n)
 
 // LOG_FIRST_N
 //
 // `LOG_FIRST_N` behaves like `LOG_EVERY_N` except that the specified message is
 // logged when the counter's value is less than `n`.  `LOG_FIRST_N` is
 // thread-safe.
-#define LOG_FIRST_N(severity, n) ABSL_LOG_FIRST_N_IMPL(_##severity, n)
+#define LOG_FIRST_N(severity, n) \
+  ABSL_LOG_INTERNAL_LOG_FIRST_N_IMPL(_##severity, n)
 
 // LOG_EVERY_POW_2
 //
 // `LOG_EVERY_POW_2` behaves like `LOG_EVERY_N` except that the specified
 // message is logged when the counter's value is a power of 2.
 // `LOG_EVERY_POW_2` is thread-safe.
-#define LOG_EVERY_POW_2(severity) ABSL_LOG_EVERY_POW_2_IMPL(_##severity)
+#define LOG_EVERY_POW_2(severity) \
+  ABSL_LOG_INTERNAL_LOG_EVERY_POW_2_IMPL(_##severity)
 
 // LOG_EVERY_N_SEC
 //
@@ -257,19 +263,25 @@
 //
 //   LOG_EVERY_N_SEC(INFO, 2.5) << "Got " << COUNTER << " cookies so far";
 #define LOG_EVERY_N_SEC(severity, n_seconds) \
-  ABSL_LOG_EVERY_N_SEC_IMPL(_##severity, n_seconds)
+  ABSL_LOG_INTERNAL_LOG_EVERY_N_SEC_IMPL(_##severity, n_seconds)
 
-#define PLOG_EVERY_N(severity, n) ABSL_PLOG_EVERY_N_IMPL(_##severity, n)
-#define PLOG_FIRST_N(severity, n) ABSL_PLOG_FIRST_N_IMPL(_##severity, n)
-#define PLOG_EVERY_POW_2(severity) ABSL_PLOG_EVERY_POW_2_IMPL(_##severity)
+#define PLOG_EVERY_N(severity, n) \
+  ABSL_LOG_INTERNAL_PLOG_EVERY_N_IMPL(_##severity, n)
+#define PLOG_FIRST_N(severity, n) \
+  ABSL_LOG_INTERNAL_PLOG_FIRST_N_IMPL(_##severity, n)
+#define PLOG_EVERY_POW_2(severity) \
+  ABSL_LOG_INTERNAL_PLOG_EVERY_POW_2_IMPL(_##severity)
 #define PLOG_EVERY_N_SEC(severity, n_seconds) \
-  ABSL_PLOG_EVERY_N_SEC_IMPL(_##severity, n_seconds)
+  ABSL_LOG_INTERNAL_PLOG_EVERY_N_SEC_IMPL(_##severity, n_seconds)
 
-#define DLOG_EVERY_N(severity, n) ABSL_DLOG_EVERY_N_IMPL(_##severity, n)
-#define DLOG_FIRST_N(severity, n) ABSL_DLOG_FIRST_N_IMPL(_##severity, n)
-#define DLOG_EVERY_POW_2(severity) ABSL_DLOG_EVERY_POW_2_IMPL(_##severity)
+#define DLOG_EVERY_N(severity, n) \
+  ABSL_LOG_INTERNAL_DLOG_EVERY_N_IMPL(_##severity, n)
+#define DLOG_FIRST_N(severity, n) \
+  ABSL_LOG_INTERNAL_DLOG_FIRST_N_IMPL(_##severity, n)
+#define DLOG_EVERY_POW_2(severity) \
+  ABSL_LOG_INTERNAL_DLOG_EVERY_POW_2_IMPL(_##severity)
 #define DLOG_EVERY_N_SEC(severity, n_seconds) \
-  ABSL_DLOG_EVERY_N_SEC_IMPL(_##severity, n_seconds)
+  ABSL_LOG_INTERNAL_DLOG_EVERY_N_SEC_IMPL(_##severity, n_seconds)
 
 // `LOG_IF_EVERY_N` and friends behave as the corresponding `LOG_EVERY_N`
 // but neither increment a counter nor log a message if condition is false (as
@@ -279,30 +291,30 @@
 //   LOG_IF_EVERY_N(INFO, (size > 1024), 10) << "Got the " << COUNTER
 //                                           << "th big cookie";
 #define LOG_IF_EVERY_N(severity, condition, n) \
-  ABSL_LOG_IF_EVERY_N_IMPL(_##severity, condition, n)
+  ABSL_LOG_INTERNAL_LOG_IF_EVERY_N_IMPL(_##severity, condition, n)
 #define LOG_IF_FIRST_N(severity, condition, n) \
-  ABSL_LOG_IF_FIRST_N_IMPL(_##severity, condition, n)
+  ABSL_LOG_INTERNAL_LOG_IF_FIRST_N_IMPL(_##severity, condition, n)
 #define LOG_IF_EVERY_POW_2(severity, condition) \
-  ABSL_LOG_IF_EVERY_POW_2_IMPL(_##severity, condition)
+  ABSL_LOG_INTERNAL_LOG_IF_EVERY_POW_2_IMPL(_##severity, condition)
 #define LOG_IF_EVERY_N_SEC(severity, condition, n_seconds) \
-  ABSL_LOG_IF_EVERY_N_SEC_IMPL(_##severity, condition, n_seconds)
+  ABSL_LOG_INTERNAL_LOG_IF_EVERY_N_SEC_IMPL(_##severity, condition, n_seconds)
 
 #define PLOG_IF_EVERY_N(severity, condition, n) \
-  ABSL_PLOG_IF_EVERY_N_IMPL(_##severity, condition, n)
+  ABSL_LOG_INTERNAL_PLOG_IF_EVERY_N_IMPL(_##severity, condition, n)
 #define PLOG_IF_FIRST_N(severity, condition, n) \
-  ABSL_PLOG_IF_FIRST_N_IMPL(_##severity, condition, n)
+  ABSL_LOG_INTERNAL_PLOG_IF_FIRST_N_IMPL(_##severity, condition, n)
 #define PLOG_IF_EVERY_POW_2(severity, condition) \
-  ABSL_PLOG_IF_EVERY_POW_2_IMPL(_##severity, condition)
+  ABSL_LOG_INTERNAL_PLOG_IF_EVERY_POW_2_IMPL(_##severity, condition)
 #define PLOG_IF_EVERY_N_SEC(severity, condition, n_seconds) \
-  ABSL_PLOG_IF_EVERY_N_SEC_IMPL(_##severity, condition, n_seconds)
+  ABSL_LOG_INTERNAL_PLOG_IF_EVERY_N_SEC_IMPL(_##severity, condition, n_seconds)
 
 #define DLOG_IF_EVERY_N(severity, condition, n) \
-  ABSL_DLOG_IF_EVERY_N_IMPL(_##severity, condition, n)
+  ABSL_LOG_INTERNAL_DLOG_IF_EVERY_N_IMPL(_##severity, condition, n)
 #define DLOG_IF_FIRST_N(severity, condition, n) \
-  ABSL_DLOG_IF_FIRST_N_IMPL(_##severity, condition, n)
+  ABSL_LOG_INTERNAL_DLOG_IF_FIRST_N_IMPL(_##severity, condition, n)
 #define DLOG_IF_EVERY_POW_2(severity, condition) \
-  ABSL_DLOG_IF_EVERY_POW_2_IMPL(_##severity, condition)
+  ABSL_LOG_INTERNAL_DLOG_IF_EVERY_POW_2_IMPL(_##severity, condition)
 #define DLOG_IF_EVERY_N_SEC(severity, condition, n_seconds) \
-  ABSL_DLOG_IF_EVERY_N_SEC_IMPL(_##severity, condition, n_seconds)
+  ABSL_LOG_INTERNAL_DLOG_IF_EVERY_N_SEC_IMPL(_##severity, condition, n_seconds)
 
 #endif  // ABSL_LOG_LOG_H_
diff --git a/absl/log/log_basic_test.cc b/absl/log/log_basic_test.cc
index b8d87c94..7fc7111d 100644
--- a/absl/log/log_basic_test.cc
+++ b/absl/log/log_basic_test.cc
@@ -18,4 +18,4 @@
 #define ABSL_TEST_LOG LOG
 
 #include "gtest/gtest.h"
-#include "absl/log/log_basic_test_impl.h"
+#include "absl/log/log_basic_test_impl.inc"
diff --git a/absl/log/log_basic_test_impl.h b/absl/log/log_basic_test_impl.inc
index 35c0b690..f3400095 100644
--- a/absl/log/log_basic_test_impl.h
+++ b/absl/log/log_basic_test_impl.inc
@@ -94,7 +94,7 @@ TEST_P(BasicLogTest, Info) {
     EXPECT_CALL(
         test_sink,
         Send(AllOf(SourceFilename(Eq(__FILE__)),
-                   SourceBasename(Eq("log_basic_test_impl.h")),
+                   SourceBasename(Eq("log_basic_test_impl.inc")),
                    SourceLine(Eq(log_line)), Prefix(IsTrue()),
                    LogSeverity(Eq(absl::LogSeverity::kInfo)),
                    TimestampInMatchWindow(),
@@ -123,7 +123,7 @@ TEST_P(BasicLogTest, Warning) {
     EXPECT_CALL(
         test_sink,
         Send(AllOf(SourceFilename(Eq(__FILE__)),
-                   SourceBasename(Eq("log_basic_test_impl.h")),
+                   SourceBasename(Eq("log_basic_test_impl.inc")),
                    SourceLine(Eq(log_line)), Prefix(IsTrue()),
                    LogSeverity(Eq(absl::LogSeverity::kWarning)),
                    TimestampInMatchWindow(),
@@ -152,7 +152,7 @@ TEST_P(BasicLogTest, Error) {
     EXPECT_CALL(
         test_sink,
         Send(AllOf(SourceFilename(Eq(__FILE__)),
-                   SourceBasename(Eq("log_basic_test_impl.h")),
+                   SourceBasename(Eq("log_basic_test_impl.inc")),
                    SourceLine(Eq(log_line)), Prefix(IsTrue()),
                    LogSeverity(Eq(absl::LogSeverity::kError)),
                    TimestampInMatchWindow(),
@@ -203,7 +203,7 @@ TEST_P(BasicLogDeathTest, Fatal) {
           EXPECT_CALL(
               test_sink,
               Send(AllOf(SourceFilename(Eq(__FILE__)),
-                         SourceBasename(Eq("log_basic_test_impl.h")),
+                         SourceBasename(Eq("log_basic_test_impl.inc")),
                          SourceLine(Eq(log_line)), Prefix(IsTrue()),
                          LogSeverity(Eq(absl::LogSeverity::kFatal)),
                          TimestampInMatchWindow(),
@@ -219,7 +219,7 @@ TEST_P(BasicLogDeathTest, Fatal) {
           EXPECT_CALL(
               test_sink,
               Send(AllOf(SourceFilename(Eq(__FILE__)),
-                         SourceBasename(Eq("log_basic_test_impl.h")),
+                         SourceBasename(Eq("log_basic_test_impl.inc")),
                          SourceLine(Eq(log_line)), Prefix(IsTrue()),
                          LogSeverity(Eq(absl::LogSeverity::kFatal)),
                          TimestampInMatchWindow(),
@@ -257,7 +257,7 @@ TEST_P(BasicLogDeathTest, QFatal) {
           EXPECT_CALL(
               test_sink,
               Send(AllOf(SourceFilename(Eq(__FILE__)),
-                         SourceBasename(Eq("log_basic_test_impl.h")),
+                         SourceBasename(Eq("log_basic_test_impl.inc")),
                          SourceLine(Eq(log_line)), Prefix(IsTrue()),
                          LogSeverity(Eq(absl::LogSeverity::kFatal)),
                          TimestampInMatchWindow(),
@@ -293,7 +293,7 @@ TEST_P(BasicLogTest, Level) {
       EXPECT_CALL(
           test_sink,
           Send(AllOf(SourceFilename(Eq(__FILE__)),
-                     SourceBasename(Eq("log_basic_test_impl.h")),
+                     SourceBasename(Eq("log_basic_test_impl.inc")),
                      SourceLine(Eq(log_line)), Prefix(IsTrue()),
                      LogSeverity(Eq(severity)), TimestampInMatchWindow(),
                      ThreadID(Eq(absl::base_internal::GetTID())),
@@ -336,7 +336,7 @@ TEST_P(BasicLogDeathTest, Level) {
           EXPECT_CALL(
               test_sink,
               Send(AllOf(SourceFilename(Eq(__FILE__)),
-                         SourceBasename(Eq("log_basic_test_impl.h")),
+                         SourceBasename(Eq("log_basic_test_impl.inc")),
                          SourceLine(Eq(log_line)), Prefix(IsTrue()),
                          LogSeverity(Eq(absl::LogSeverity::kFatal)),
                          TimestampInMatchWindow(),
@@ -351,7 +351,7 @@ TEST_P(BasicLogDeathTest, Level) {
           EXPECT_CALL(
               test_sink,
               Send(AllOf(SourceFilename(Eq(__FILE__)),
-                         SourceBasename(Eq("log_basic_test_impl.h")),
+                         SourceBasename(Eq("log_basic_test_impl.inc")),
                          SourceLine(Eq(log_line)), Prefix(IsTrue()),
                          LogSeverity(Eq(absl::LogSeverity::kFatal)),
                          TimestampInMatchWindow(),
diff --git a/absl/log/log_sink_test.cc b/absl/log/log_sink_test.cc
index 8903da72..fa743060 100644
--- a/absl/log/log_sink_test.cc
+++ b/absl/log/log_sink_test.cc
@@ -18,7 +18,6 @@
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
 #include "absl/base/attributes.h"
-#include "absl/base/internal/raw_logging.h"
 #include "absl/log/internal/test_actions.h"
 #include "absl/log/internal/test_helpers.h"
 #include "absl/log/internal/test_matchers.h"
@@ -205,7 +204,7 @@ class ReentrancyTest : public ::testing::Test {
               << "The log is coming from *inside the sink*.";
           break;
         default:
-          ABSL_RAW_LOG(FATAL, "Invalid mode %d.\n", static_cast<int>(mode_));
+          LOG(FATAL) << "Invalid mode " << static_cast<int>(mode_);
       }
     }
 
diff --git a/absl/log/scoped_mock_log.cc b/absl/log/scoped_mock_log.cc
index 4ebc0a9f..39a0a52a 100644
--- a/absl/log/scoped_mock_log.cc
+++ b/absl/log/scoped_mock_log.cc
@@ -30,7 +30,7 @@ namespace absl {
 ABSL_NAMESPACE_BEGIN
 
 ScopedMockLog::ScopedMockLog(MockLogDefault default_exp)
-    : sink_(this), is_capturing_logs_(false) {
+    : sink_(this), is_capturing_logs_(false), is_triggered_(false) {
   if (default_exp == MockLogDefault::kIgnoreUnexpected) {
     // Ignore all calls to Log we did not set expectations for.
     EXPECT_CALL(*this, Log).Times(::testing::AnyNumber());
diff --git a/absl/log/scoped_mock_log.h b/absl/log/scoped_mock_log.h
index 44470c16..399e604d 100644
--- a/absl/log/scoped_mock_log.h
+++ b/absl/log/scoped_mock_log.h
@@ -185,6 +185,9 @@ class ScopedMockLog final {
 
   ForwardingSink sink_;
   bool is_capturing_logs_;
+  // Until C++20, the default constructor leaves the underlying value wrapped in
+  // std::atomic uninitialized, so all constructors should be sure to initialize
+  // is_triggered_.
   std::atomic<bool> is_triggered_;
 };
 
diff --git a/absl/log/scoped_mock_log_test.cc b/absl/log/scoped_mock_log_test.cc
index 44b8d737..42736939 100644
--- a/absl/log/scoped_mock_log_test.cc
+++ b/absl/log/scoped_mock_log_test.cc
@@ -71,6 +71,11 @@ TEST(ScopedMockLogDeathTest, StopCapturingLogsCannotBeCalledWhenNotCapturing) {
       },
       "StopCapturingLogs");
 }
+
+TEST(ScopedMockLogDeathTest, FailsCheckIfStartCapturingLogsIsNeverCalled) {
+  EXPECT_DEATH({ absl::ScopedMockLog log; },
+               "Did you forget to call StartCapturingLogs");
+}
 #endif
 
 // Tests that ScopedMockLog intercepts LOG()s when it's alive.
diff --git a/absl/log/stripping_test.cc b/absl/log/stripping_test.cc
index d6a6606e..aff91495 100644
--- a/absl/log/stripping_test.cc
+++ b/absl/log/stripping_test.cc
@@ -49,6 +49,7 @@
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
 #include "absl/base/internal/strerror.h"
+#include "absl/base/log_severity.h"
 #include "absl/flags/internal/program_name.h"
 #include "absl/log/check.h"
 #include "absl/log/internal/test_helpers.h"
@@ -57,6 +58,10 @@
 #include "absl/strings/str_format.h"
 #include "absl/strings/string_view.h"
 
+// Set a flag that controls whether we actually execute fatal statements, but
+// prevent the compiler from optimizing it out.
+static volatile bool kReallyDie = false;
+
 namespace {
 using ::testing::_;
 using ::testing::Eq;
@@ -304,7 +309,10 @@ TEST_F(StrippingTest, Fatal) {
   // as would happen if we used a literal.  We might (or might not) leave it
   // lying around later; that's what the tests are for!
   const std::string needle = absl::Base64Escape("StrippingTest.Fatal");
-  EXPECT_DEATH_IF_SUPPORTED(LOG(FATAL) << "U3RyaXBwaW5nVGVzdC5GYXRhbA==", "");
+  // We don't care if the LOG statement is actually executed, we're just
+  // checking that it's stripped.
+  if (kReallyDie) LOG(FATAL) << "U3RyaXBwaW5nVGVzdC5GYXRhbA==";
+
   std::unique_ptr<FILE, std::function<void(FILE*)>> exe = OpenTestExecutable();
   ASSERT_THAT(exe, NotNull());
   if (absl::LogSeverity::kFatal >= kAbslMinLogLevel) {
@@ -337,4 +345,30 @@ TEST_F(StrippingTest, Level) {
   }
 }
 
+TEST_F(StrippingTest, Check) {
+  // Here we also need a variable name with enough entropy that it's unlikely to
+  // appear in the binary by chance.  `volatile` keeps the tautological
+  // comparison (and the rest of the `CHECK`) from being optimized away.
+  const std::string var_needle = absl::Base64Escape("StrippingTestCheckVar");
+  const std::string msg_needle = absl::Base64Escape("StrippingTest.Check");
+  volatile int U3RyaXBwaW5nVGVzdENoZWNrVmFy = 0xCAFE;
+  // We don't care if the CHECK is actually executed, just that stripping works.
+  // Hiding it behind `kReallyDie` works around some overly aggressive
+  // optimizations in older versions of MSVC.
+  if (kReallyDie) {
+    CHECK(U3RyaXBwaW5nVGVzdENoZWNrVmFy != U3RyaXBwaW5nVGVzdENoZWNrVmFy)
+        << "U3RyaXBwaW5nVGVzdC5DaGVjaw==";
+  }
+
+  std::unique_ptr<FILE, std::function<void(FILE*)>> exe = OpenTestExecutable();
+  ASSERT_THAT(exe, NotNull());
+  if (absl::LogSeverity::kFatal >= kAbslMinLogLevel) {
+    EXPECT_THAT(exe.get(), FileHasSubstr(var_needle));
+    EXPECT_THAT(exe.get(), FileHasSubstr(msg_needle));
+  } else {
+    EXPECT_THAT(exe.get(), Not(FileHasSubstr(var_needle)));
+    EXPECT_THAT(exe.get(), Not(FileHasSubstr(msg_needle)));
+  }
+}
+
 }  // namespace
diff --git a/absl/meta/BUILD.bazel b/absl/meta/BUILD.bazel
index 125446f9..13051d83 100644
--- a/absl/meta/BUILD.bazel
+++ b/absl/meta/BUILD.bazel
@@ -32,6 +32,7 @@ cc_library(
     linkopts = ABSL_DEFAULT_LINKOPTS,
     deps = [
         "//absl/base:config",
+        "//absl/base:core_headers",
     ],
 )
 
diff --git a/absl/meta/CMakeLists.txt b/absl/meta/CMakeLists.txt
index bb767d12..d509114c 100644
--- a/absl/meta/CMakeLists.txt
+++ b/absl/meta/CMakeLists.txt
@@ -23,6 +23,7 @@ absl_cc_library(
     ${ABSL_DEFAULT_COPTS}
   DEPS
     absl::config
+    absl::core_headers
   PUBLIC
 )
 
diff --git a/absl/meta/type_traits.h b/absl/meta/type_traits.h
index b1656c39..cf71164b 100644
--- a/absl/meta/type_traits.h
+++ b/absl/meta/type_traits.h
@@ -39,14 +39,9 @@
 #include <functional>
 #include <type_traits>
 
+#include "absl/base/attributes.h"
 #include "absl/base/config.h"
 
-// MSVC constructibility traits do not detect destructor properties and so our
-// implementations should not use them as a source-of-truth.
-#if defined(_MSC_VER) && !defined(__clang__) && !defined(__GNUC__)
-#define ABSL_META_INTERNAL_STD_CONSTRUCTION_TRAITS_DONT_CHECK_DESTRUCTION 1
-#endif
-
 // Defines the default alignment. `__STDCPP_DEFAULT_NEW_ALIGNMENT__` is a C++17
 // feature.
 #if defined(__STDCPP_DEFAULT_NEW_ALIGNMENT__)
@@ -58,57 +53,8 @@
 namespace absl {
 ABSL_NAMESPACE_BEGIN
 
-// Defined and documented later on in this file.
-template <typename T>
-struct is_trivially_destructible;
-
-// Defined and documented later on in this file.
-template <typename T>
-struct is_trivially_move_assignable;
-
 namespace type_traits_internal {
 
-// Silence MSVC warnings about the destructor being defined as deleted.
-#if defined(_MSC_VER) && !defined(__GNUC__)
-#pragma warning(push)
-#pragma warning(disable : 4624)
-#endif  // defined(_MSC_VER) && !defined(__GNUC__)
-
-template <class T>
-union SingleMemberUnion {
-  T t;
-};
-
-// Restore the state of the destructor warning that was silenced above.
-#if defined(_MSC_VER) && !defined(__GNUC__)
-#pragma warning(pop)
-#endif  // defined(_MSC_VER) && !defined(__GNUC__)
-
-template <class T>
-struct IsTriviallyMoveConstructibleObject
-    : std::integral_constant<
-          bool, std::is_move_constructible<
-                    type_traits_internal::SingleMemberUnion<T>>::value &&
-                    absl::is_trivially_destructible<T>::value> {};
-
-template <class T>
-struct IsTriviallyCopyConstructibleObject
-    : std::integral_constant<
-          bool, std::is_copy_constructible<
-                    type_traits_internal::SingleMemberUnion<T>>::value &&
-                    absl::is_trivially_destructible<T>::value> {};
-
-template <class T>
-struct IsTriviallyMoveAssignableReference : std::false_type {};
-
-template <class T>
-struct IsTriviallyMoveAssignableReference<T&>
-    : absl::is_trivially_move_assignable<T>::type {};
-
-template <class T>
-struct IsTriviallyMoveAssignableReference<T&&>
-    : absl::is_trivially_move_assignable<T>::type {};
-
 template <typename... Ts>
 struct VoidTImpl {
   using type = void;
@@ -157,39 +103,8 @@ template <class To, template <class...> class Op, class... Args>
 struct is_detected_convertible
     : is_detected_convertible_impl<void, To, Op, Args...>::type {};
 
-template <typename T>
-using IsCopyAssignableImpl =
-    decltype(std::declval<T&>() = std::declval<const T&>());
-
-template <typename T>
-using IsMoveAssignableImpl = decltype(std::declval<T&>() = std::declval<T&&>());
-
 }  // namespace type_traits_internal
 
-// MSVC 19.20 has a regression that causes our workarounds to fail, but their
-// std forms now appear to be compliant.
-#if defined(_MSC_VER) && !defined(__clang__) && (_MSC_VER >= 1920)
-
-template <typename T>
-using is_copy_assignable = std::is_copy_assignable<T>;
-
-template <typename T>
-using is_move_assignable = std::is_move_assignable<T>;
-
-#else
-
-template <typename T>
-struct is_copy_assignable : type_traits_internal::is_detected<
-                                type_traits_internal::IsCopyAssignableImpl, T> {
-};
-
-template <typename T>
-struct is_move_assignable : type_traits_internal::is_detected<
-                                type_traits_internal::IsMoveAssignableImpl, T> {
-};
-
-#endif
-
 // void_t()
 //
 // Ignores the type of any its arguments and returns `void`. In general, this
@@ -270,246 +185,29 @@ struct is_function
           bool, !(std::is_reference<T>::value ||
                   std::is_const<typename std::add_const<T>::type>::value)> {};
 
+// is_copy_assignable()
+// is_move_assignable()
 // is_trivially_destructible()
-//
-// Determines whether the passed type `T` is trivially destructible.
-//
-// This metafunction is designed to be a drop-in replacement for the C++11
-// `std::is_trivially_destructible()` metafunction for platforms that have
-// incomplete C++11 support (such as libstdc++ 4.x). On any platforms that do
-// fully support C++11, we check whether this yields the same result as the std
-// implementation.
-//
-// NOTE: the extensions (__has_trivial_xxx) are implemented in gcc (version >=
-// 4.3) and clang. Since we are supporting libstdc++ > 4.7, they should always
-// be present. These  extensions are documented at
-// https://gcc.gnu.org/onlinedocs/gcc/Type-Traits.html#Type-Traits.
-template <typename T>
-struct is_trivially_destructible
-#ifdef ABSL_HAVE_STD_IS_TRIVIALLY_DESTRUCTIBLE
-    : std::is_trivially_destructible<T> {
-#else
-    : std::integral_constant<bool, __has_trivial_destructor(T) &&
-                                   std::is_destructible<T>::value> {
-#endif
-#ifdef ABSL_HAVE_STD_IS_TRIVIALLY_DESTRUCTIBLE
- private:
-  static constexpr bool compliant = std::is_trivially_destructible<T>::value ==
-                                    is_trivially_destructible::value;
-  static_assert(compliant || std::is_trivially_destructible<T>::value,
-                "Not compliant with std::is_trivially_destructible; "
-                "Standard: false, Implementation: true");
-  static_assert(compliant || !std::is_trivially_destructible<T>::value,
-                "Not compliant with std::is_trivially_destructible; "
-                "Standard: true, Implementation: false");
-#endif  // ABSL_HAVE_STD_IS_TRIVIALLY_DESTRUCTIBLE
-};
-
 // is_trivially_default_constructible()
-//
-// Determines whether the passed type `T` is trivially default constructible.
-//
-// This metafunction is designed to be a drop-in replacement for the C++11
-// `std::is_trivially_default_constructible()` metafunction for platforms that
-// have incomplete C++11 support (such as libstdc++ 4.x). On any platforms that
-// do fully support C++11, we check whether this yields the same result as the
-// std implementation.
-//
-// NOTE: according to the C++ standard, Section: 20.15.4.3 [meta.unary.prop]
-// "The predicate condition for a template specialization is_constructible<T,
-// Args...> shall be satisfied if and only if the following variable
-// definition would be well-formed for some invented variable t:
-//
-// T t(declval<Args>()...);
-//
-// is_trivially_constructible<T, Args...> additionally requires that the
-// variable definition does not call any operation that is not trivial.
-// For the purposes of this check, the call to std::declval is considered
-// trivial."
-//
-// Notes from https://en.cppreference.com/w/cpp/types/is_constructible:
-// In many implementations, is_nothrow_constructible also checks if the
-// destructor throws because it is effectively noexcept(T(arg)). Same
-// applies to is_trivially_constructible, which, in these implementations, also
-// requires that the destructor is trivial.
-// GCC bug 51452: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=51452
-// LWG issue 2116: http://cplusplus.github.io/LWG/lwg-active.html#2116.
-//
-// "T obj();" need to be well-formed and not call any nontrivial operation.
-// Nontrivially destructible types will cause the expression to be nontrivial.
-template <typename T>
-struct is_trivially_default_constructible
-#if defined(ABSL_HAVE_STD_IS_TRIVIALLY_CONSTRUCTIBLE)
-    : std::is_trivially_default_constructible<T> {
-#else
-    : std::integral_constant<bool, __has_trivial_constructor(T) &&
-                                   std::is_default_constructible<T>::value &&
-                                   is_trivially_destructible<T>::value> {
-#endif
-#if defined(ABSL_HAVE_STD_IS_TRIVIALLY_CONSTRUCTIBLE) && \
-    !defined(                                            \
-        ABSL_META_INTERNAL_STD_CONSTRUCTION_TRAITS_DONT_CHECK_DESTRUCTION)
- private:
-  static constexpr bool compliant =
-      std::is_trivially_default_constructible<T>::value ==
-      is_trivially_default_constructible::value;
-  static_assert(compliant || std::is_trivially_default_constructible<T>::value,
-                "Not compliant with std::is_trivially_default_constructible; "
-                "Standard: false, Implementation: true");
-  static_assert(compliant || !std::is_trivially_default_constructible<T>::value,
-                "Not compliant with std::is_trivially_default_constructible; "
-                "Standard: true, Implementation: false");
-#endif  // ABSL_HAVE_STD_IS_TRIVIALLY_CONSTRUCTIBLE
-};
-
 // is_trivially_move_constructible()
-//
-// Determines whether the passed type `T` is trivially move constructible.
-//
-// This metafunction is designed to be a drop-in replacement for the C++11
-// `std::is_trivially_move_constructible()` metafunction for platforms that have
-// incomplete C++11 support (such as libstdc++ 4.x). On any platforms that do
-// fully support C++11, we check whether this yields the same result as the std
-// implementation.
-//
-// NOTE: `T obj(declval<T>());` needs to be well-formed and not call any
-// nontrivial operation.  Nontrivially destructible types will cause the
-// expression to be nontrivial.
-template <typename T>
-struct is_trivially_move_constructible
-#if defined(ABSL_HAVE_STD_IS_TRIVIALLY_CONSTRUCTIBLE)
-    : std::is_trivially_move_constructible<T> {
-#else
-    : std::conditional<
-          std::is_object<T>::value && !std::is_array<T>::value,
-          type_traits_internal::IsTriviallyMoveConstructibleObject<T>,
-          std::is_reference<T>>::type::type {
-#endif
-#if defined(ABSL_HAVE_STD_IS_TRIVIALLY_CONSTRUCTIBLE) && \
-    !defined(                                            \
-        ABSL_META_INTERNAL_STD_CONSTRUCTION_TRAITS_DONT_CHECK_DESTRUCTION)
- private:
-  static constexpr bool compliant =
-      std::is_trivially_move_constructible<T>::value ==
-      is_trivially_move_constructible::value;
-  static_assert(compliant || std::is_trivially_move_constructible<T>::value,
-                "Not compliant with std::is_trivially_move_constructible; "
-                "Standard: false, Implementation: true");
-  static_assert(compliant || !std::is_trivially_move_constructible<T>::value,
-                "Not compliant with std::is_trivially_move_constructible; "
-                "Standard: true, Implementation: false");
-#endif  // ABSL_HAVE_STD_IS_TRIVIALLY_CONSTRUCTIBLE
-};
-
 // is_trivially_copy_constructible()
-//
-// Determines whether the passed type `T` is trivially copy constructible.
-//
-// This metafunction is designed to be a drop-in replacement for the C++11
-// `std::is_trivially_copy_constructible()` metafunction for platforms that have
-// incomplete C++11 support (such as libstdc++ 4.x). On any platforms that do
-// fully support C++11, we check whether this yields the same result as the std
-// implementation.
-//
-// NOTE: `T obj(declval<const T&>());` needs to be well-formed and not call any
-// nontrivial operation.  Nontrivially destructible types will cause the
-// expression to be nontrivial.
-template <typename T>
-struct is_trivially_copy_constructible
-    : std::conditional<
-          std::is_object<T>::value && !std::is_array<T>::value,
-          type_traits_internal::IsTriviallyCopyConstructibleObject<T>,
-          std::is_lvalue_reference<T>>::type::type {
-#if defined(ABSL_HAVE_STD_IS_TRIVIALLY_CONSTRUCTIBLE) && \
-    !defined(                                            \
-        ABSL_META_INTERNAL_STD_CONSTRUCTION_TRAITS_DONT_CHECK_DESTRUCTION)
- private:
-  static constexpr bool compliant =
-      std::is_trivially_copy_constructible<T>::value ==
-      is_trivially_copy_constructible::value;
-  static_assert(compliant || std::is_trivially_copy_constructible<T>::value,
-                "Not compliant with std::is_trivially_copy_constructible; "
-                "Standard: false, Implementation: true");
-  static_assert(compliant || !std::is_trivially_copy_constructible<T>::value,
-                "Not compliant with std::is_trivially_copy_constructible; "
-                "Standard: true, Implementation: false");
-#endif  // ABSL_HAVE_STD_IS_TRIVIALLY_CONSTRUCTIBLE
-};
-
 // is_trivially_move_assignable()
-//
-// Determines whether the passed type `T` is trivially move assignable.
-//
-// This metafunction is designed to be a drop-in replacement for the C++11
-// `std::is_trivially_move_assignable()` metafunction for platforms that have
-// incomplete C++11 support (such as libstdc++ 4.x). On any platforms that do
-// fully support C++11, we check whether this yields the same result as the std
-// implementation.
-//
-// NOTE: `is_assignable<T, U>::value` is `true` if the expression
-// `declval<T>() = declval<U>()` is well-formed when treated as an unevaluated
-// operand. `is_trivially_assignable<T, U>` requires the assignment to call no
-// operation that is not trivial. `is_trivially_copy_assignable<T>` is simply
-// `is_trivially_assignable<T&, T>`.
-template <typename T>
-struct is_trivially_move_assignable
-    : std::conditional<
-          std::is_object<T>::value && !std::is_array<T>::value &&
-              std::is_move_assignable<T>::value,
-          std::is_move_assignable<type_traits_internal::SingleMemberUnion<T>>,
-          type_traits_internal::IsTriviallyMoveAssignableReference<T>>::type::
-          type {
-#ifdef ABSL_HAVE_STD_IS_TRIVIALLY_ASSIGNABLE
- private:
-  static constexpr bool compliant =
-      std::is_trivially_move_assignable<T>::value ==
-      is_trivially_move_assignable::value;
-  static_assert(compliant || std::is_trivially_move_assignable<T>::value,
-                "Not compliant with std::is_trivially_move_assignable; "
-                "Standard: false, Implementation: true");
-  static_assert(compliant || !std::is_trivially_move_assignable<T>::value,
-                "Not compliant with std::is_trivially_move_assignable; "
-                "Standard: true, Implementation: false");
-#endif  // ABSL_HAVE_STD_IS_TRIVIALLY_ASSIGNABLE
-};
-
 // is_trivially_copy_assignable()
 //
-// Determines whether the passed type `T` is trivially copy assignable.
-//
-// This metafunction is designed to be a drop-in replacement for the C++11
-// `std::is_trivially_copy_assignable()` metafunction for platforms that have
-// incomplete C++11 support (such as libstdc++ 4.x). On any platforms that do
-// fully support C++11, we check whether this yields the same result as the std
-// implementation.
-//
-// NOTE: `is_assignable<T, U>::value` is `true` if the expression
-// `declval<T>() = declval<U>()` is well-formed when treated as an unevaluated
-// operand. `is_trivially_assignable<T, U>` requires the assignment to call no
-// operation that is not trivial. `is_trivially_copy_assignable<T>` is simply
-// `is_trivially_assignable<T&, const T&>`.
-template <typename T>
-struct is_trivially_copy_assignable
-#ifdef ABSL_HAVE_STD_IS_TRIVIALLY_ASSIGNABLE
-    : std::is_trivially_copy_assignable<T> {
-#else
-    : std::integral_constant<
-          bool, __has_trivial_assign(typename std::remove_reference<T>::type) &&
-                    absl::is_copy_assignable<T>::value> {
-#endif
-#ifdef ABSL_HAVE_STD_IS_TRIVIALLY_ASSIGNABLE
- private:
-  static constexpr bool compliant =
-      std::is_trivially_copy_assignable<T>::value ==
-      is_trivially_copy_assignable::value;
-  static_assert(compliant || std::is_trivially_copy_assignable<T>::value,
-                "Not compliant with std::is_trivially_copy_assignable; "
-                "Standard: false, Implementation: true");
-  static_assert(compliant || !std::is_trivially_copy_assignable<T>::value,
-                "Not compliant with std::is_trivially_copy_assignable; "
-                "Standard: true, Implementation: false");
-#endif  // ABSL_HAVE_STD_IS_TRIVIALLY_ASSIGNABLE
-};
+// Historical note: Abseil once provided implementations of these type traits
+// for platforms that lacked full support. New code should prefer to use the
+// std variants.
+//
+// See the documentation for the STL <type_traits> header for more information:
+// https://en.cppreference.com/w/cpp/header/type_traits
+using std::is_copy_assignable;
+using std::is_move_assignable;
+using std::is_trivially_copy_assignable;
+using std::is_trivially_copy_constructible;
+using std::is_trivially_default_constructible;
+using std::is_trivially_destructible;
+using std::is_trivially_move_assignable;
+using std::is_trivially_move_constructible;
 
 #if defined(__cpp_lib_remove_cvref) && __cpp_lib_remove_cvref >= 201711L
 template <typename T>
@@ -532,55 +230,6 @@ template <typename T>
 using remove_cvref_t = typename remove_cvref<T>::type;
 #endif
 
-namespace type_traits_internal {
-// is_trivially_copyable()
-//
-// Determines whether the passed type `T` is trivially copyable.
-//
-// This metafunction is designed to be a drop-in replacement for the C++11
-// `std::is_trivially_copyable()` metafunction for platforms that have
-// incomplete C++11 support (such as libstdc++ 4.x). We use the C++17 definition
-// of TriviallyCopyable.
-//
-// NOTE: `is_trivially_copyable<T>::value` is `true` if all of T's copy/move
-// constructors/assignment operators are trivial or deleted, T has at least
-// one non-deleted copy/move constructor/assignment operator, and T is trivially
-// destructible. Arrays of trivially copyable types are trivially copyable.
-//
-// We expose this metafunction only for internal use within absl.
-
-#if defined(ABSL_HAVE_STD_IS_TRIVIALLY_COPYABLE)
-template <typename T>
-struct is_trivially_copyable : std::is_trivially_copyable<T> {};
-#else
-template <typename T>
-class is_trivially_copyable_impl {
-  using ExtentsRemoved = typename std::remove_all_extents<T>::type;
-  static constexpr bool kIsCopyOrMoveConstructible =
-      std::is_copy_constructible<ExtentsRemoved>::value ||
-      std::is_move_constructible<ExtentsRemoved>::value;
-  static constexpr bool kIsCopyOrMoveAssignable =
-      absl::is_copy_assignable<ExtentsRemoved>::value ||
-      absl::is_move_assignable<ExtentsRemoved>::value;
-
- public:
-  static constexpr bool kValue =
-      (__has_trivial_copy(ExtentsRemoved) || !kIsCopyOrMoveConstructible) &&
-      (__has_trivial_assign(ExtentsRemoved) || !kIsCopyOrMoveAssignable) &&
-      (kIsCopyOrMoveConstructible || kIsCopyOrMoveAssignable) &&
-      is_trivially_destructible<ExtentsRemoved>::value &&
-      // We need to check for this explicitly because otherwise we'll say
-      // references are trivial copyable when compiled by MSVC.
-      !std::is_reference<ExtentsRemoved>::value;
-};
-
-template <typename T>
-struct is_trivially_copyable
-    : std::integral_constant<
-          bool, type_traits_internal::is_trivially_copyable_impl<T>::kValue> {};
-#endif
-}  // namespace type_traits_internal
-
 // -----------------------------------------------------------------------------
 // C++14 "_t" trait aliases
 // -----------------------------------------------------------------------------
@@ -630,6 +279,7 @@ using remove_extent_t = typename std::remove_extent<T>::type;
 template <typename T>
 using remove_all_extents_t = typename std::remove_all_extents<T>::type;
 
+ABSL_INTERNAL_DISABLE_DEPRECATED_DECLARATION_WARNING
 namespace type_traits_internal {
 // This trick to retrieve a default alignment is necessary for our
 // implementation of aligned_storage_t to be consistent with any
@@ -648,6 +298,7 @@ struct default_alignment_of_aligned_storage<
 template <size_t Len, size_t Align = type_traits_internal::
                           default_alignment_of_aligned_storage<Len>::value>
 using aligned_storage_t = typename std::aligned_storage<Len, Align>::type;
+ABSL_INTERNAL_RESTORE_DEPRECATED_DECLARATION_WARNING
 
 template <typename T>
 using decay_t = typename std::decay<T>::type;
@@ -818,9 +469,14 @@ using swap_internal::StdSwapIsUnconstrained;
 }  // namespace type_traits_internal
 
 // absl::is_trivially_relocatable<T>
-// Detects whether a type is "trivially relocatable" -- meaning it can be
-// relocated without invoking the constructor/destructor, using a form of move
-// elision.
+//
+// Detects whether a type is known to be "trivially relocatable" -- meaning it
+// can be relocated without invoking the constructor/destructor, using a form of
+// move elision.
+//
+// This trait is conservative, for backwards compatibility. If it's true then
+// the type is definitely trivially relocatable, but if it's false then the type
+// may or may not be.
 //
 // Example:
 //
@@ -834,14 +490,33 @@ using swap_internal::StdSwapIsUnconstrained;
 // Upstream documentation:
 //
 // https://clang.llvm.org/docs/LanguageExtensions.html#:~:text=__is_trivially_relocatable
+
+// If the compiler offers a builtin that tells us the answer, we can use that.
+// This covers all of the cases in the fallback below, plus types that opt in
+// using e.g. [[clang::trivial_abi]].
 //
-#if ABSL_HAVE_BUILTIN(__is_trivially_relocatable)
+// Clang on Windows has the builtin, but it falsely claims types with a
+// user-provided destructor are trivial (http://b/275003464). So we opt out
+// there.
+//
+// TODO(b/275003464): remove the opt-out once the bug is fixed.
+//
+// According to https://github.com/abseil/abseil-cpp/issues/1479, this does not
+// work with NVCC either.
+#if ABSL_HAVE_BUILTIN(__is_trivially_relocatable) &&                 \
+    !(defined(__clang__) && (defined(_WIN32) || defined(_WIN64))) && \
+    !defined(__NVCC__)
 template <class T>
 struct is_trivially_relocatable
     : std::integral_constant<bool, __is_trivially_relocatable(T)> {};
 #else
+// Otherwise we use a fallback that detects only those types we can feasibly
+// detect. Any time that has trivial move-construction and destruction
+// operations is by definition trivially relocatable.
 template <class T>
-struct is_trivially_relocatable : std::integral_constant<bool, false> {};
+struct is_trivially_relocatable
+    : absl::conjunction<absl::is_trivially_move_constructible<T>,
+                        absl::is_trivially_destructible<T>> {};
 #endif
 
 // absl::is_constant_evaluated()
diff --git a/absl/meta/type_traits_test.cc b/absl/meta/type_traits_test.cc
index b2a7a67b..7412f33d 100644
--- a/absl/meta/type_traits_test.cc
+++ b/absl/meta/type_traits_test.cc
@@ -352,29 +352,6 @@ class Base {
   virtual ~Base() {}
 };
 
-// Old versions of libc++, around Clang 3.5 to 3.6, consider deleted destructors
-// as also being trivial. With the resolution of CWG 1928 and CWG 1734, this
-// is no longer considered true and has thus been amended.
-// Compiler Explorer: https://godbolt.org/g/zT59ZL
-// CWG issue 1734: http://open-std.org/JTC1/SC22/WG21/docs/cwg_defects.html#1734
-// CWG issue 1928: http://open-std.org/JTC1/SC22/WG21/docs/cwg_closed.html#1928
-#if !defined(_LIBCPP_VERSION) || _LIBCPP_VERSION >= 3700
-#define ABSL_TRIVIALLY_DESTRUCTIBLE_CONSIDER_DELETED_DESTRUCTOR_NOT_TRIVIAL 1
-#endif
-
-// As of the moment, GCC versions >5.1 have a problem compiling for
-// std::is_trivially_default_constructible<NontrivialDestructor[10]>, where
-// NontrivialDestructor is a struct with a custom nontrivial destructor. Note
-// that this problem only occurs for arrays of a known size, so something like
-// std::is_trivially_default_constructible<NontrivialDestructor[]> does not
-// have any problems.
-// Compiler Explorer: https://godbolt.org/g/dXRbdK
-// GCC bug 83689: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83689
-#if defined(__clang__) || defined(_MSC_VER) || \
-    (defined(__GNUC__) && __GNUC__ < 5)
-#define ABSL_GCC_BUG_TRIVIALLY_CONSTRUCTIBLE_ON_ARRAY_OF_NONTRIVIAL 1
-#endif
-
 TEST(TypeTraitsTest, TestIsFunction) {
   struct Callable {
     void operator()() {}
@@ -391,562 +368,6 @@ TEST(TypeTraitsTest, TestIsFunction) {
   EXPECT_FALSE(absl::is_function<Callable>::value);
 }
 
-TEST(TypeTraitsTest, TestTrivialDestructor) {
-  // Verify that arithmetic types and pointers have trivial destructors.
-  EXPECT_TRUE(absl::is_trivially_destructible<bool>::value);
-  EXPECT_TRUE(absl::is_trivially_destructible<char>::value);
-  EXPECT_TRUE(absl::is_trivially_destructible<unsigned char>::value);
-  EXPECT_TRUE(absl::is_trivially_destructible<signed char>::value);
-  EXPECT_TRUE(absl::is_trivially_destructible<wchar_t>::value);
-  EXPECT_TRUE(absl::is_trivially_destructible<int>::value);
-  EXPECT_TRUE(absl::is_trivially_destructible<unsigned int>::value);
-  EXPECT_TRUE(absl::is_trivially_destructible<int16_t>::value);
-  EXPECT_TRUE(absl::is_trivially_destructible<uint16_t>::value);
-  EXPECT_TRUE(absl::is_trivially_destructible<int64_t>::value);
-  EXPECT_TRUE(absl::is_trivially_destructible<uint64_t>::value);
-  EXPECT_TRUE(absl::is_trivially_destructible<float>::value);
-  EXPECT_TRUE(absl::is_trivially_destructible<double>::value);
-  EXPECT_TRUE(absl::is_trivially_destructible<long double>::value);
-  EXPECT_TRUE(absl::is_trivially_destructible<std::string*>::value);
-  EXPECT_TRUE(absl::is_trivially_destructible<Trivial*>::value);
-  EXPECT_TRUE(absl::is_trivially_destructible<const std::string*>::value);
-  EXPECT_TRUE(absl::is_trivially_destructible<const Trivial*>::value);
-  EXPECT_TRUE(absl::is_trivially_destructible<std::string**>::value);
-  EXPECT_TRUE(absl::is_trivially_destructible<Trivial**>::value);
-
-  // classes with destructors
-  EXPECT_TRUE(absl::is_trivially_destructible<Trivial>::value);
-  EXPECT_TRUE(absl::is_trivially_destructible<TrivialDestructor>::value);
-
-  // Verify that types with a nontrivial or deleted destructor
-  // are marked as such.
-  EXPECT_FALSE(absl::is_trivially_destructible<NontrivialDestructor>::value);
-#ifdef ABSL_TRIVIALLY_DESTRUCTIBLE_CONSIDER_DELETED_DESTRUCTOR_NOT_TRIVIAL
-  EXPECT_FALSE(absl::is_trivially_destructible<DeletedDestructor>::value);
-#endif
-
-  // simple_pair of such types is trivial
-  EXPECT_TRUE((absl::is_trivially_destructible<simple_pair<int, int>>::value));
-  EXPECT_TRUE((absl::is_trivially_destructible<
-               simple_pair<Trivial, TrivialDestructor>>::value));
-
-  // Verify that types without trivial destructors are correctly marked as such.
-  EXPECT_FALSE(absl::is_trivially_destructible<std::string>::value);
-  EXPECT_FALSE(absl::is_trivially_destructible<std::vector<int>>::value);
-
-  // Verify that simple_pairs of types without trivial destructors
-  // are not marked as trivial.
-  EXPECT_FALSE((absl::is_trivially_destructible<
-                simple_pair<int, std::string>>::value));
-  EXPECT_FALSE((absl::is_trivially_destructible<
-                simple_pair<std::string, int>>::value));
-
-  // array of such types is trivial
-  using int10 = int[10];
-  EXPECT_TRUE(absl::is_trivially_destructible<int10>::value);
-  using Trivial10 = Trivial[10];
-  EXPECT_TRUE(absl::is_trivially_destructible<Trivial10>::value);
-  using TrivialDestructor10 = TrivialDestructor[10];
-  EXPECT_TRUE(absl::is_trivially_destructible<TrivialDestructor10>::value);
-
-  // Conversely, the opposite also holds.
-  using NontrivialDestructor10 = NontrivialDestructor[10];
-  EXPECT_FALSE(absl::is_trivially_destructible<NontrivialDestructor10>::value);
-}
-
-TEST(TypeTraitsTest, TestTrivialDefaultCtor) {
-  // arithmetic types and pointers have trivial default constructors.
-  EXPECT_TRUE(absl::is_trivially_default_constructible<bool>::value);
-  EXPECT_TRUE(absl::is_trivially_default_constructible<char>::value);
-  EXPECT_TRUE(absl::is_trivially_default_constructible<unsigned char>::value);
-  EXPECT_TRUE(absl::is_trivially_default_constructible<signed char>::value);
-  EXPECT_TRUE(absl::is_trivially_default_constructible<wchar_t>::value);
-  EXPECT_TRUE(absl::is_trivially_default_constructible<int>::value);
-  EXPECT_TRUE(absl::is_trivially_default_constructible<unsigned int>::value);
-  EXPECT_TRUE(absl::is_trivially_default_constructible<int16_t>::value);
-  EXPECT_TRUE(absl::is_trivially_default_constructible<uint16_t>::value);
-  EXPECT_TRUE(absl::is_trivially_default_constructible<int64_t>::value);
-  EXPECT_TRUE(absl::is_trivially_default_constructible<uint64_t>::value);
-  EXPECT_TRUE(absl::is_trivially_default_constructible<float>::value);
-  EXPECT_TRUE(absl::is_trivially_default_constructible<double>::value);
-  EXPECT_TRUE(absl::is_trivially_default_constructible<long double>::value);
-  EXPECT_TRUE(absl::is_trivially_default_constructible<std::string*>::value);
-  EXPECT_TRUE(absl::is_trivially_default_constructible<Trivial*>::value);
-  EXPECT_TRUE(
-      absl::is_trivially_default_constructible<const std::string*>::value);
-  EXPECT_TRUE(absl::is_trivially_default_constructible<const Trivial*>::value);
-  EXPECT_TRUE(absl::is_trivially_default_constructible<std::string**>::value);
-  EXPECT_TRUE(absl::is_trivially_default_constructible<Trivial**>::value);
-
-  // types with compiler generated default ctors
-  EXPECT_TRUE(absl::is_trivially_default_constructible<Trivial>::value);
-  EXPECT_TRUE(
-      absl::is_trivially_default_constructible<TrivialDefaultCtor>::value);
-
-  // Verify that types without them are not.
-  EXPECT_FALSE(
-      absl::is_trivially_default_constructible<NontrivialDefaultCtor>::value);
-  EXPECT_FALSE(
-      absl::is_trivially_default_constructible<DeletedDefaultCtor>::value);
-
-  // types with nontrivial destructor are nontrivial
-  EXPECT_FALSE(
-      absl::is_trivially_default_constructible<NontrivialDestructor>::value);
-
-  // types with vtables
-  EXPECT_FALSE(absl::is_trivially_default_constructible<Base>::value);
-
-  // Verify that simple_pair has trivial constructors where applicable.
-  EXPECT_TRUE((absl::is_trivially_default_constructible<
-               simple_pair<int, char*>>::value));
-  EXPECT_TRUE((absl::is_trivially_default_constructible<
-               simple_pair<int, Trivial>>::value));
-  EXPECT_TRUE((absl::is_trivially_default_constructible<
-               simple_pair<int, TrivialDefaultCtor>>::value));
-
-  // Verify that types without trivial constructors are
-  // correctly marked as such.
-  EXPECT_FALSE(absl::is_trivially_default_constructible<std::string>::value);
-  EXPECT_FALSE(
-      absl::is_trivially_default_constructible<std::vector<int>>::value);
-
-  // Verify that simple_pairs of types without trivial constructors
-  // are not marked as trivial.
-  EXPECT_FALSE((absl::is_trivially_default_constructible<
-                simple_pair<int, std::string>>::value));
-  EXPECT_FALSE((absl::is_trivially_default_constructible<
-                simple_pair<std::string, int>>::value));
-
-  // Verify that arrays of such types are trivially default constructible
-  using int10 = int[10];
-  EXPECT_TRUE(absl::is_trivially_default_constructible<int10>::value);
-  using Trivial10 = Trivial[10];
-  EXPECT_TRUE(absl::is_trivially_default_constructible<Trivial10>::value);
-  using TrivialDefaultCtor10 = TrivialDefaultCtor[10];
-  EXPECT_TRUE(
-      absl::is_trivially_default_constructible<TrivialDefaultCtor10>::value);
-
-  // Conversely, the opposite also holds.
-#ifdef ABSL_GCC_BUG_TRIVIALLY_CONSTRUCTIBLE_ON_ARRAY_OF_NONTRIVIAL
-  using NontrivialDefaultCtor10 = NontrivialDefaultCtor[10];
-  EXPECT_FALSE(
-      absl::is_trivially_default_constructible<NontrivialDefaultCtor10>::value);
-#endif
-}
-
-// GCC prior to 7.4 had a bug in its trivially-constructible traits
-// (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80654).
-// This test makes sure that we do not depend on the trait in these cases when
-// implementing absl triviality traits.
-
-template <class T>
-struct BadConstructors {
-  BadConstructors() { static_assert(T::value, ""); }
-
-  BadConstructors(BadConstructors&&) { static_assert(T::value, ""); }
-
-  BadConstructors(const BadConstructors&) { static_assert(T::value, ""); }
-};
-
-TEST(TypeTraitsTest, TestTrivialityBadConstructors) {
-  using BadType = BadConstructors<int>;
-
-  EXPECT_FALSE(absl::is_trivially_default_constructible<BadType>::value);
-  EXPECT_FALSE(absl::is_trivially_move_constructible<BadType>::value);
-  EXPECT_FALSE(absl::is_trivially_copy_constructible<BadType>::value);
-}
-
-TEST(TypeTraitsTest, TestTrivialMoveCtor) {
-  // Verify that arithmetic types and pointers have trivial move
-  // constructors.
-  EXPECT_TRUE(absl::is_trivially_move_constructible<bool>::value);
-  EXPECT_TRUE(absl::is_trivially_move_constructible<char>::value);
-  EXPECT_TRUE(absl::is_trivially_move_constructible<unsigned char>::value);
-  EXPECT_TRUE(absl::is_trivially_move_constructible<signed char>::value);
-  EXPECT_TRUE(absl::is_trivially_move_constructible<wchar_t>::value);
-  EXPECT_TRUE(absl::is_trivially_move_constructible<int>::value);
-  EXPECT_TRUE(absl::is_trivially_move_constructible<unsigned int>::value);
-  EXPECT_TRUE(absl::is_trivially_move_constructible<int16_t>::value);
-  EXPECT_TRUE(absl::is_trivially_move_constructible<uint16_t>::value);
-  EXPECT_TRUE(absl::is_trivially_move_constructible<int64_t>::value);
-  EXPECT_TRUE(absl::is_trivially_move_constructible<uint64_t>::value);
-  EXPECT_TRUE(absl::is_trivially_move_constructible<float>::value);
-  EXPECT_TRUE(absl::is_trivially_move_constructible<double>::value);
-  EXPECT_TRUE(absl::is_trivially_move_constructible<long double>::value);
-  EXPECT_TRUE(absl::is_trivially_move_constructible<std::string*>::value);
-  EXPECT_TRUE(absl::is_trivially_move_constructible<Trivial*>::value);
-  EXPECT_TRUE(absl::is_trivially_move_constructible<const std::string*>::value);
-  EXPECT_TRUE(absl::is_trivially_move_constructible<const Trivial*>::value);
-  EXPECT_TRUE(absl::is_trivially_move_constructible<std::string**>::value);
-  EXPECT_TRUE(absl::is_trivially_move_constructible<Trivial**>::value);
-
-  // Reference types
-  EXPECT_TRUE(absl::is_trivially_move_constructible<int&>::value);
-  EXPECT_TRUE(absl::is_trivially_move_constructible<int&&>::value);
-
-  // types with compiler generated move ctors
-  EXPECT_TRUE(absl::is_trivially_move_constructible<Trivial>::value);
-  EXPECT_TRUE(absl::is_trivially_move_constructible<TrivialMoveCtor>::value);
-
-  // Verify that types without them (i.e. nontrivial or deleted) are not.
-  EXPECT_FALSE(
-      absl::is_trivially_move_constructible<NontrivialCopyCtor>::value);
-  EXPECT_FALSE(absl::is_trivially_move_constructible<DeletedCopyCtor>::value);
-  EXPECT_FALSE(
-      absl::is_trivially_move_constructible<NonCopyableOrMovable>::value);
-
-  // type with nontrivial destructor are nontrivial move construbtible
-  EXPECT_FALSE(
-      absl::is_trivially_move_constructible<NontrivialDestructor>::value);
-
-  // types with vtables
-  EXPECT_FALSE(absl::is_trivially_move_constructible<Base>::value);
-
-  // Verify that simple_pair of such types is trivially move constructible
-  EXPECT_TRUE(
-      (absl::is_trivially_move_constructible<simple_pair<int, char*>>::value));
-  EXPECT_TRUE((
-      absl::is_trivially_move_constructible<simple_pair<int, Trivial>>::value));
-  EXPECT_TRUE((absl::is_trivially_move_constructible<
-               simple_pair<int, TrivialMoveCtor>>::value));
-
-  // Verify that types without trivial move constructors are
-  // correctly marked as such.
-  EXPECT_FALSE(absl::is_trivially_move_constructible<std::string>::value);
-  EXPECT_FALSE(absl::is_trivially_move_constructible<std::vector<int>>::value);
-
-  // Verify that simple_pairs of types without trivial move constructors
-  // are not marked as trivial.
-  EXPECT_FALSE((absl::is_trivially_move_constructible<
-                simple_pair<int, std::string>>::value));
-  EXPECT_FALSE((absl::is_trivially_move_constructible<
-                simple_pair<std::string, int>>::value));
-
-  // Verify that arrays are not
-  using int10 = int[10];
-  EXPECT_FALSE(absl::is_trivially_move_constructible<int10>::value);
-}
-
-TEST(TypeTraitsTest, TestTrivialCopyCtor) {
-  // Verify that arithmetic types and pointers have trivial copy
-  // constructors.
-  EXPECT_TRUE(absl::is_trivially_copy_constructible<bool>::value);
-  EXPECT_TRUE(absl::is_trivially_copy_constructible<char>::value);
-  EXPECT_TRUE(absl::is_trivially_copy_constructible<unsigned char>::value);
-  EXPECT_TRUE(absl::is_trivially_copy_constructible<signed char>::value);
-  EXPECT_TRUE(absl::is_trivially_copy_constructible<wchar_t>::value);
-  EXPECT_TRUE(absl::is_trivially_copy_constructible<int>::value);
-  EXPECT_TRUE(absl::is_trivially_copy_constructible<unsigned int>::value);
-  EXPECT_TRUE(absl::is_trivially_copy_constructible<int16_t>::value);
-  EXPECT_TRUE(absl::is_trivially_copy_constructible<uint16_t>::value);
-  EXPECT_TRUE(absl::is_trivially_copy_constructible<int64_t>::value);
-  EXPECT_TRUE(absl::is_trivially_copy_constructible<uint64_t>::value);
-  EXPECT_TRUE(absl::is_trivially_copy_constructible<float>::value);
-  EXPECT_TRUE(absl::is_trivially_copy_constructible<double>::value);
-  EXPECT_TRUE(absl::is_trivially_copy_constructible<long double>::value);
-  EXPECT_TRUE(absl::is_trivially_copy_constructible<std::string*>::value);
-  EXPECT_TRUE(absl::is_trivially_copy_constructible<Trivial*>::value);
-  EXPECT_TRUE(absl::is_trivially_copy_constructible<const std::string*>::value);
-  EXPECT_TRUE(absl::is_trivially_copy_constructible<const Trivial*>::value);
-  EXPECT_TRUE(absl::is_trivially_copy_constructible<std::string**>::value);
-  EXPECT_TRUE(absl::is_trivially_copy_constructible<Trivial**>::value);
-
-  // Reference types
-  EXPECT_TRUE(absl::is_trivially_copy_constructible<int&>::value);
-  EXPECT_FALSE(absl::is_trivially_copy_constructible<int&&>::value);
-
-  // types with compiler generated copy ctors
-  EXPECT_TRUE(absl::is_trivially_copy_constructible<Trivial>::value);
-  EXPECT_TRUE(absl::is_trivially_copy_constructible<TrivialCopyCtor>::value);
-
-  // Verify that types without them (i.e. nontrivial or deleted) are not.
-  EXPECT_FALSE(
-      absl::is_trivially_copy_constructible<NontrivialCopyCtor>::value);
-  EXPECT_FALSE(absl::is_trivially_copy_constructible<DeletedCopyCtor>::value);
-  EXPECT_FALSE(
-      absl::is_trivially_copy_constructible<MovableNonCopyable>::value);
-  EXPECT_FALSE(
-      absl::is_trivially_copy_constructible<NonCopyableOrMovable>::value);
-
-  // type with nontrivial destructor are nontrivial copy construbtible
-  EXPECT_FALSE(
-      absl::is_trivially_copy_constructible<NontrivialDestructor>::value);
-
-  // types with vtables
-  EXPECT_FALSE(absl::is_trivially_copy_constructible<Base>::value);
-
-  // Verify that simple_pair of such types is trivially copy constructible
-  EXPECT_TRUE(
-      (absl::is_trivially_copy_constructible<simple_pair<int, char*>>::value));
-  EXPECT_TRUE((
-      absl::is_trivially_copy_constructible<simple_pair<int, Trivial>>::value));
-  EXPECT_TRUE((absl::is_trivially_copy_constructible<
-               simple_pair<int, TrivialCopyCtor>>::value));
-
-  // Verify that types without trivial copy constructors are
-  // correctly marked as such.
-  EXPECT_FALSE(absl::is_trivially_copy_constructible<std::string>::value);
-  EXPECT_FALSE(absl::is_trivially_copy_constructible<std::vector<int>>::value);
-
-  // Verify that simple_pairs of types without trivial copy constructors
-  // are not marked as trivial.
-  EXPECT_FALSE((absl::is_trivially_copy_constructible<
-                simple_pair<int, std::string>>::value));
-  EXPECT_FALSE((absl::is_trivially_copy_constructible<
-                simple_pair<std::string, int>>::value));
-
-  // Verify that arrays are not
-  using int10 = int[10];
-  EXPECT_FALSE(absl::is_trivially_copy_constructible<int10>::value);
-}
-
-TEST(TypeTraitsTest, TestTrivialMoveAssign) {
-  // Verify that arithmetic types and pointers have trivial move
-  // assignment operators.
-  EXPECT_TRUE(absl::is_trivially_move_assignable<bool>::value);
-  EXPECT_TRUE(absl::is_trivially_move_assignable<char>::value);
-  EXPECT_TRUE(absl::is_trivially_move_assignable<unsigned char>::value);
-  EXPECT_TRUE(absl::is_trivially_move_assignable<signed char>::value);
-  EXPECT_TRUE(absl::is_trivially_move_assignable<wchar_t>::value);
-  EXPECT_TRUE(absl::is_trivially_move_assignable<int>::value);
-  EXPECT_TRUE(absl::is_trivially_move_assignable<unsigned int>::value);
-  EXPECT_TRUE(absl::is_trivially_move_assignable<int16_t>::value);
-  EXPECT_TRUE(absl::is_trivially_move_assignable<uint16_t>::value);
-  EXPECT_TRUE(absl::is_trivially_move_assignable<int64_t>::value);
-  EXPECT_TRUE(absl::is_trivially_move_assignable<uint64_t>::value);
-  EXPECT_TRUE(absl::is_trivially_move_assignable<float>::value);
-  EXPECT_TRUE(absl::is_trivially_move_assignable<double>::value);
-  EXPECT_TRUE(absl::is_trivially_move_assignable<long double>::value);
-  EXPECT_TRUE(absl::is_trivially_move_assignable<std::string*>::value);
-  EXPECT_TRUE(absl::is_trivially_move_assignable<Trivial*>::value);
-  EXPECT_TRUE(absl::is_trivially_move_assignable<const std::string*>::value);
-  EXPECT_TRUE(absl::is_trivially_move_assignable<const Trivial*>::value);
-  EXPECT_TRUE(absl::is_trivially_move_assignable<std::string**>::value);
-  EXPECT_TRUE(absl::is_trivially_move_assignable<Trivial**>::value);
-
-  // const qualified types are not assignable
-  EXPECT_FALSE(absl::is_trivially_move_assignable<const int>::value);
-
-  // types with compiler generated move assignment
-  EXPECT_TRUE(absl::is_trivially_move_assignable<Trivial>::value);
-  EXPECT_TRUE(absl::is_trivially_move_assignable<TrivialMoveAssign>::value);
-
-  // Verify that types without them (i.e. nontrivial or deleted) are not.
-  EXPECT_FALSE(absl::is_trivially_move_assignable<NontrivialCopyAssign>::value);
-  EXPECT_FALSE(absl::is_trivially_move_assignable<DeletedCopyAssign>::value);
-  EXPECT_FALSE(absl::is_trivially_move_assignable<NonCopyableOrMovable>::value);
-
-  // types with vtables
-  EXPECT_FALSE(absl::is_trivially_move_assignable<Base>::value);
-
-  // Verify that simple_pair is trivially assignable
-  EXPECT_TRUE(
-      (absl::is_trivially_move_assignable<simple_pair<int, char*>>::value));
-  EXPECT_TRUE(
-      (absl::is_trivially_move_assignable<simple_pair<int, Trivial>>::value));
-  EXPECT_TRUE((absl::is_trivially_move_assignable<
-               simple_pair<int, TrivialMoveAssign>>::value));
-
-  // Verify that types not trivially move assignable are
-  // correctly marked as such.
-  EXPECT_FALSE(absl::is_trivially_move_assignable<std::string>::value);
-  EXPECT_FALSE(absl::is_trivially_move_assignable<std::vector<int>>::value);
-
-  // Verify that simple_pairs of types not trivially move assignable
-  // are not marked as trivial.
-  EXPECT_FALSE((absl::is_trivially_move_assignable<
-                simple_pair<int, std::string>>::value));
-  EXPECT_FALSE((absl::is_trivially_move_assignable<
-                simple_pair<std::string, int>>::value));
-
-  // Verify that arrays are not trivially move assignable
-  using int10 = int[10];
-  EXPECT_FALSE(absl::is_trivially_move_assignable<int10>::value);
-
-  // Verify that references are handled correctly
-  EXPECT_TRUE(absl::is_trivially_move_assignable<Trivial&&>::value);
-  EXPECT_TRUE(absl::is_trivially_move_assignable<Trivial&>::value);
-}
-
-TEST(TypeTraitsTest, TestTrivialCopyAssign) {
-  // Verify that arithmetic types and pointers have trivial copy
-  // assignment operators.
-  EXPECT_TRUE(absl::is_trivially_copy_assignable<bool>::value);
-  EXPECT_TRUE(absl::is_trivially_copy_assignable<char>::value);
-  EXPECT_TRUE(absl::is_trivially_copy_assignable<unsigned char>::value);
-  EXPECT_TRUE(absl::is_trivially_copy_assignable<signed char>::value);
-  EXPECT_TRUE(absl::is_trivially_copy_assignable<wchar_t>::value);
-  EXPECT_TRUE(absl::is_trivially_copy_assignable<int>::value);
-  EXPECT_TRUE(absl::is_trivially_copy_assignable<unsigned int>::value);
-  EXPECT_TRUE(absl::is_trivially_copy_assignable<int16_t>::value);
-  EXPECT_TRUE(absl::is_trivially_copy_assignable<uint16_t>::value);
-  EXPECT_TRUE(absl::is_trivially_copy_assignable<int64_t>::value);
-  EXPECT_TRUE(absl::is_trivially_copy_assignable<uint64_t>::value);
-  EXPECT_TRUE(absl::is_trivially_copy_assignable<float>::value);
-  EXPECT_TRUE(absl::is_trivially_copy_assignable<double>::value);
-  EXPECT_TRUE(absl::is_trivially_copy_assignable<long double>::value);
-  EXPECT_TRUE(absl::is_trivially_copy_assignable<std::string*>::value);
-  EXPECT_TRUE(absl::is_trivially_copy_assignable<Trivial*>::value);
-  EXPECT_TRUE(absl::is_trivially_copy_assignable<const std::string*>::value);
-  EXPECT_TRUE(absl::is_trivially_copy_assignable<const Trivial*>::value);
-  EXPECT_TRUE(absl::is_trivially_copy_assignable<std::string**>::value);
-  EXPECT_TRUE(absl::is_trivially_copy_assignable<Trivial**>::value);
-
-  // const qualified types are not assignable
-  EXPECT_FALSE(absl::is_trivially_copy_assignable<const int>::value);
-
-  // types with compiler generated copy assignment
-  EXPECT_TRUE(absl::is_trivially_copy_assignable<Trivial>::value);
-  EXPECT_TRUE(absl::is_trivially_copy_assignable<TrivialCopyAssign>::value);
-
-  // Verify that types without them (i.e. nontrivial or deleted) are not.
-  EXPECT_FALSE(absl::is_trivially_copy_assignable<NontrivialCopyAssign>::value);
-  EXPECT_FALSE(absl::is_trivially_copy_assignable<DeletedCopyAssign>::value);
-  EXPECT_FALSE(absl::is_trivially_copy_assignable<MovableNonCopyable>::value);
-  EXPECT_FALSE(absl::is_trivially_copy_assignable<NonCopyableOrMovable>::value);
-
-  // types with vtables
-  EXPECT_FALSE(absl::is_trivially_copy_assignable<Base>::value);
-
-  // Verify that simple_pair is trivially assignable
-  EXPECT_TRUE(
-      (absl::is_trivially_copy_assignable<simple_pair<int, char*>>::value));
-  EXPECT_TRUE(
-      (absl::is_trivially_copy_assignable<simple_pair<int, Trivial>>::value));
-  EXPECT_TRUE((absl::is_trivially_copy_assignable<
-               simple_pair<int, TrivialCopyAssign>>::value));
-
-  // Verify that types not trivially copy assignable are
-  // correctly marked as such.
-  EXPECT_FALSE(absl::is_trivially_copy_assignable<std::string>::value);
-  EXPECT_FALSE(absl::is_trivially_copy_assignable<std::vector<int>>::value);
-
-  // Verify that simple_pairs of types not trivially copy assignable
-  // are not marked as trivial.
-  EXPECT_FALSE((absl::is_trivially_copy_assignable<
-                simple_pair<int, std::string>>::value));
-  EXPECT_FALSE((absl::is_trivially_copy_assignable<
-                simple_pair<std::string, int>>::value));
-
-  // Verify that arrays are not trivially copy assignable
-  using int10 = int[10];
-  EXPECT_FALSE(absl::is_trivially_copy_assignable<int10>::value);
-
-  // Verify that references are handled correctly
-  EXPECT_TRUE(absl::is_trivially_copy_assignable<Trivial&&>::value);
-  EXPECT_TRUE(absl::is_trivially_copy_assignable<Trivial&>::value);
-}
-
-TEST(TypeTraitsTest, TestTriviallyCopyable) {
-  // Verify that arithmetic types and pointers are trivially copyable.
-  EXPECT_TRUE(absl::type_traits_internal::is_trivially_copyable<bool>::value);
-  EXPECT_TRUE(absl::type_traits_internal::is_trivially_copyable<char>::value);
-  EXPECT_TRUE(
-      absl::type_traits_internal::is_trivially_copyable<unsigned char>::value);
-  EXPECT_TRUE(
-      absl::type_traits_internal::is_trivially_copyable<signed char>::value);
-  EXPECT_TRUE(
-      absl::type_traits_internal::is_trivially_copyable<wchar_t>::value);
-  EXPECT_TRUE(absl::type_traits_internal::is_trivially_copyable<int>::value);
-  EXPECT_TRUE(
-      absl::type_traits_internal::is_trivially_copyable<unsigned int>::value);
-  EXPECT_TRUE(
-      absl::type_traits_internal::is_trivially_copyable<int16_t>::value);
-  EXPECT_TRUE(
-      absl::type_traits_internal::is_trivially_copyable<uint16_t>::value);
-  EXPECT_TRUE(
-      absl::type_traits_internal::is_trivially_copyable<int64_t>::value);
-  EXPECT_TRUE(
-      absl::type_traits_internal::is_trivially_copyable<uint64_t>::value);
-  EXPECT_TRUE(absl::type_traits_internal::is_trivially_copyable<float>::value);
-  EXPECT_TRUE(absl::type_traits_internal::is_trivially_copyable<double>::value);
-  EXPECT_TRUE(
-      absl::type_traits_internal::is_trivially_copyable<long double>::value);
-  EXPECT_TRUE(
-      absl::type_traits_internal::is_trivially_copyable<std::string*>::value);
-  EXPECT_TRUE(
-      absl::type_traits_internal::is_trivially_copyable<Trivial*>::value);
-  EXPECT_TRUE(absl::type_traits_internal::is_trivially_copyable<
-              const std::string*>::value);
-  EXPECT_TRUE(
-      absl::type_traits_internal::is_trivially_copyable<const Trivial*>::value);
-  EXPECT_TRUE(
-      absl::type_traits_internal::is_trivially_copyable<std::string**>::value);
-  EXPECT_TRUE(
-      absl::type_traits_internal::is_trivially_copyable<Trivial**>::value);
-
-  // const qualified types are not assignable but are constructible
-  EXPECT_TRUE(
-      absl::type_traits_internal::is_trivially_copyable<const int>::value);
-
-  // Trivial copy constructor/assignment and destructor.
-  EXPECT_TRUE(
-      absl::type_traits_internal::is_trivially_copyable<Trivial>::value);
-  // Trivial copy assignment, but non-trivial copy constructor/destructor.
-  EXPECT_FALSE(absl::type_traits_internal::is_trivially_copyable<
-               TrivialCopyAssign>::value);
-  // Trivial copy constructor, but non-trivial assignment.
-  EXPECT_FALSE(absl::type_traits_internal::is_trivially_copyable<
-               TrivialCopyCtor>::value);
-
-  // Types with a non-trivial copy constructor/assignment
-  EXPECT_FALSE(absl::type_traits_internal::is_trivially_copyable<
-               NontrivialCopyCtor>::value);
-  EXPECT_FALSE(absl::type_traits_internal::is_trivially_copyable<
-               NontrivialCopyAssign>::value);
-
-  // Types without copy constructor/assignment, but with move
-  // MSVC disagrees with other compilers about this:
-  // EXPECT_TRUE(absl::type_traits_internal::is_trivially_copyable<
-  //             MovableNonCopyable>::value);
-
-  // Types without copy/move constructor/assignment
-  EXPECT_FALSE(absl::type_traits_internal::is_trivially_copyable<
-               NonCopyableOrMovable>::value);
-
-  // No copy assign, but has trivial copy constructor.
-  EXPECT_TRUE(absl::type_traits_internal::is_trivially_copyable<
-              DeletedCopyAssign>::value);
-
-  // types with vtables
-  EXPECT_FALSE(absl::type_traits_internal::is_trivially_copyable<Base>::value);
-
-  // Verify that simple_pair is trivially copyable if members are
-  EXPECT_TRUE((absl::type_traits_internal::is_trivially_copyable<
-               simple_pair<int, char*>>::value));
-  EXPECT_TRUE((absl::type_traits_internal::is_trivially_copyable<
-               simple_pair<int, Trivial>>::value));
-
-  // Verify that types not trivially copyable are
-  // correctly marked as such.
-  EXPECT_FALSE(
-      absl::type_traits_internal::is_trivially_copyable<std::string>::value);
-  EXPECT_FALSE(absl::type_traits_internal::is_trivially_copyable<
-               std::vector<int>>::value);
-
-  // Verify that simple_pairs of types not trivially copyable
-  // are not marked as trivial.
-  EXPECT_FALSE((absl::type_traits_internal::is_trivially_copyable<
-                simple_pair<int, std::string>>::value));
-  EXPECT_FALSE((absl::type_traits_internal::is_trivially_copyable<
-                simple_pair<std::string, int>>::value));
-  EXPECT_FALSE((absl::type_traits_internal::is_trivially_copyable<
-                simple_pair<int, TrivialCopyAssign>>::value));
-
-  // Verify that arrays of trivially copyable types are trivially copyable
-  using int10 = int[10];
-  EXPECT_TRUE(absl::type_traits_internal::is_trivially_copyable<int10>::value);
-  using int10x10 = int[10][10];
-  EXPECT_TRUE(
-      absl::type_traits_internal::is_trivially_copyable<int10x10>::value);
-
-  // Verify that references are handled correctly
-  EXPECT_FALSE(
-      absl::type_traits_internal::is_trivially_copyable<Trivial&&>::value);
-  EXPECT_FALSE(
-      absl::type_traits_internal::is_trivially_copyable<Trivial&>::value);
-}
-
 TEST(TypeTraitsTest, TestRemoveCVRef) {
   EXPECT_TRUE(
       (std::is_same<typename absl::remove_cvref<int>::type, int>::value));
@@ -1241,82 +662,6 @@ TEST(TypeTraitsTest, TestResultOf) {
   EXPECT_EQ(TypeEnum::D, GetTypeExt(Wrap<TypeD>()));
 }
 
-template <typename T>
-bool TestCopyAssign() {
-  return absl::is_copy_assignable<T>::value ==
-         std::is_copy_assignable<T>::value;
-}
-
-TEST(TypeTraitsTest, IsCopyAssignable) {
-  EXPECT_TRUE(TestCopyAssign<int>());
-  EXPECT_TRUE(TestCopyAssign<int&>());
-  EXPECT_TRUE(TestCopyAssign<int&&>());
-
-  struct S {};
-  EXPECT_TRUE(TestCopyAssign<S>());
-  EXPECT_TRUE(TestCopyAssign<S&>());
-  EXPECT_TRUE(TestCopyAssign<S&&>());
-
-  class C {
-   public:
-    explicit C(C* c) : c_(c) {}
-    ~C() { delete c_; }
-
-   private:
-    C* c_;
-  };
-  EXPECT_TRUE(TestCopyAssign<C>());
-  EXPECT_TRUE(TestCopyAssign<C&>());
-  EXPECT_TRUE(TestCopyAssign<C&&>());
-
-  // Reason for ifndef: add_lvalue_reference<T> in libc++ breaks for these cases
-#ifndef _LIBCPP_VERSION
-  EXPECT_TRUE(TestCopyAssign<int()>());
-  EXPECT_TRUE(TestCopyAssign<int(int) const>());
-  EXPECT_TRUE(TestCopyAssign<int(...) volatile&>());
-  EXPECT_TRUE(TestCopyAssign<int(int, ...) const volatile&&>());
-#endif  // _LIBCPP_VERSION
-}
-
-template <typename T>
-bool TestMoveAssign() {
-  return absl::is_move_assignable<T>::value ==
-         std::is_move_assignable<T>::value;
-}
-
-TEST(TypeTraitsTest, IsMoveAssignable) {
-  EXPECT_TRUE(TestMoveAssign<int>());
-  EXPECT_TRUE(TestMoveAssign<int&>());
-  EXPECT_TRUE(TestMoveAssign<int&&>());
-
-  struct S {};
-  EXPECT_TRUE(TestMoveAssign<S>());
-  EXPECT_TRUE(TestMoveAssign<S&>());
-  EXPECT_TRUE(TestMoveAssign<S&&>());
-
-  class C {
-   public:
-    explicit C(C* c) : c_(c) {}
-    ~C() { delete c_; }
-    void operator=(const C&) = delete;
-    void operator=(C&&) = delete;
-
-   private:
-    C* c_;
-  };
-  EXPECT_TRUE(TestMoveAssign<C>());
-  EXPECT_TRUE(TestMoveAssign<C&>());
-  EXPECT_TRUE(TestMoveAssign<C&&>());
-
-  // Reason for ifndef: add_lvalue_reference<T> in libc++ breaks for these cases
-#ifndef _LIBCPP_VERSION
-  EXPECT_TRUE(TestMoveAssign<int()>());
-  EXPECT_TRUE(TestMoveAssign<int(int) const>());
-  EXPECT_TRUE(TestMoveAssign<int(...) volatile&>());
-  EXPECT_TRUE(TestMoveAssign<int(int, ...) const volatile&&>());
-#endif  // _LIBCPP_VERSION
-}
-
 namespace adl_namespace {
 
 struct DeletedSwap {
@@ -1398,24 +743,72 @@ TEST(TypeTraitsTest, IsNothrowSwappable) {
   EXPECT_TRUE(IsNothrowSwappable<adl_namespace::SpecialNoexceptSwap>::value);
 }
 
-TEST(TrivallyRelocatable, Sanity) {
-#if !defined(ABSL_HAVE_ATTRIBUTE_TRIVIAL_ABI) || \
-    !ABSL_HAVE_BUILTIN(__is_trivially_relocatable)
-  GTEST_SKIP() << "No trivial ABI support.";
-#endif
+TEST(TriviallyRelocatable, PrimitiveTypes) {
+  static_assert(absl::is_trivially_relocatable<int>::value, "");
+  static_assert(absl::is_trivially_relocatable<char>::value, "");
+  static_assert(absl::is_trivially_relocatable<void*>::value, "");
+}
 
-  struct Trivial {};
-  struct NonTrivial {
-    NonTrivial(const NonTrivial&) {}  // NOLINT
+// User-defined types can be trivially relocatable as long as they don't have a
+// user-provided move constructor or destructor.
+TEST(TriviallyRelocatable, UserDefinedTriviallyReconstructible) {
+  struct S {
+    int x;
+    int y;
   };
-  struct ABSL_ATTRIBUTE_TRIVIAL_ABI TrivialAbi {
-    TrivialAbi(const TrivialAbi&) {}  // NOLINT
+
+  static_assert(absl::is_trivially_relocatable<S>::value, "");
+}
+
+// A user-provided move constructor disqualifies a type from being trivially
+// relocatable.
+TEST(TriviallyRelocatable, UserProvidedMoveConstructor) {
+  struct S {
+    S(S&&) {}  // NOLINT(modernize-use-equals-default)
+  };
+
+  static_assert(!absl::is_trivially_relocatable<S>::value, "");
+}
+
+// A user-provided copy constructor disqualifies a type from being trivially
+// relocatable.
+TEST(TriviallyRelocatable, UserProvidedCopyConstructor) {
+  struct S {
+    S(const S&) {}  // NOLINT(modernize-use-equals-default)
   };
-  EXPECT_TRUE(absl::is_trivially_relocatable<Trivial>::value);
-  EXPECT_FALSE(absl::is_trivially_relocatable<NonTrivial>::value);
-  EXPECT_TRUE(absl::is_trivially_relocatable<TrivialAbi>::value);
+
+  static_assert(!absl::is_trivially_relocatable<S>::value, "");
 }
 
+// A user-provided destructor disqualifies a type from being trivially
+// relocatable.
+TEST(TriviallyRelocatable, UserProvidedDestructor) {
+  struct S {
+    ~S() {}  // NOLINT(modernize-use-equals-default)
+  };
+
+  static_assert(!absl::is_trivially_relocatable<S>::value, "");
+}
+
+// TODO(b/275003464): remove the opt-out for Clang on Windows once
+// __is_trivially_relocatable is used there again.
+#if defined(ABSL_HAVE_ATTRIBUTE_TRIVIAL_ABI) &&      \
+    ABSL_HAVE_BUILTIN(__is_trivially_relocatable) && \
+    !(defined(__clang__) && (defined(_WIN32) || defined(_WIN64)))
+// A type marked with the "trivial ABI" attribute is trivially relocatable even
+// if it has user-provided move/copy constructors and a user-provided
+// destructor.
+TEST(TrivallyRelocatable, TrivialAbi) {
+  struct ABSL_ATTRIBUTE_TRIVIAL_ABI S {
+    S(S&&) {}       // NOLINT(modernize-use-equals-default)
+    S(const S&) {}  // NOLINT(modernize-use-equals-default)
+    ~S() {}         // NOLINT(modernize-use-equals-default)
+  };
+
+  static_assert(absl::is_trivially_relocatable<S>::value, "");
+}
+#endif
+
 #ifdef ABSL_HAVE_CONSTANT_EVALUATED
 
 constexpr int64_t NegateIfConstantEvaluated(int64_t i) {
diff --git a/absl/numeric/BUILD.bazel b/absl/numeric/BUILD.bazel
index ec0b8701..c5aaf72b 100644
--- a/absl/numeric/BUILD.bazel
+++ b/absl/numeric/BUILD.bazel
@@ -97,6 +97,7 @@ cc_test(
         "//absl/base",
         "//absl/hash:hash_testing",
         "//absl/meta:type_traits",
+        "//absl/strings",
         "@com_google_googletest//:gtest_main",
     ],
 )
diff --git a/absl/numeric/CMakeLists.txt b/absl/numeric/CMakeLists.txt
index 384c0fc0..7181b91a 100644
--- a/absl/numeric/CMakeLists.txt
+++ b/absl/numeric/CMakeLists.txt
@@ -72,6 +72,7 @@ absl_cc_test(
     absl::base
     absl::hash_testing
     absl::type_traits
+    absl::strings
     GTest::gmock_main
 )
 
diff --git a/absl/numeric/bits.h b/absl/numeric/bits.h
index df81b9a9..5ed36f52 100644
--- a/absl/numeric/bits.h
+++ b/absl/numeric/bits.h
@@ -38,19 +38,19 @@
 #include <limits>
 #include <type_traits>
 
-#if (defined(__cpp_lib_int_pow2) && __cpp_lib_int_pow2 >= 202002L) || \
-    (defined(__cpp_lib_bitops) && __cpp_lib_bitops >= 201907L)
+#include "absl/base/config.h"
+
+#if ABSL_INTERNAL_CPLUSPLUS_LANG >= 202002L
 #include <bit>
 #endif
 
 #include "absl/base/attributes.h"
-#include "absl/base/config.h"
 #include "absl/numeric/internal/bits.h"
 
 namespace absl {
 ABSL_NAMESPACE_BEGIN
-
 #if !(defined(__cpp_lib_bitops) && __cpp_lib_bitops >= 201907L)
+
 // rotating
 template <class T>
 ABSL_MUST_USE_RESULT constexpr
diff --git a/absl/numeric/bits_test.cc b/absl/numeric/bits_test.cc
index 7c942aae..14955eb3 100644
--- a/absl/numeric/bits_test.cc
+++ b/absl/numeric/bits_test.cc
@@ -15,6 +15,7 @@
 #include "absl/numeric/bits.h"
 
 #include <limits>
+#include <type_traits>
 
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
@@ -24,6 +25,73 @@ namespace absl {
 ABSL_NAMESPACE_BEGIN
 namespace {
 
+template <typename IntT>
+class IntegerTypesTest : public ::testing::Test {};
+
+using OneByteIntegerTypes = ::testing::Types<
+    unsigned char,
+    uint8_t
+    >;
+
+TYPED_TEST_SUITE(IntegerTypesTest, OneByteIntegerTypes);
+
+TYPED_TEST(IntegerTypesTest, HandlesTypes) {
+  using UIntType = TypeParam;
+
+  EXPECT_EQ(rotl(UIntType{0x12}, 0), uint8_t{0x12});
+  EXPECT_EQ(rotr(UIntType{0x12}, -4), uint8_t{0x21});
+  static_assert(rotl(UIntType{0x12}, 0) == uint8_t{0x12}, "");
+
+  static_assert(rotr(UIntType{0x12}, 0) == uint8_t{0x12}, "");
+  EXPECT_EQ(rotr(UIntType{0x12}, 0), uint8_t{0x12});
+
+#if ABSL_INTERNAL_HAS_CONSTEXPR_CLZ
+  static_assert(countl_zero(UIntType{}) == 8, "");
+  static_assert(countl_zero(static_cast<UIntType>(-1)) == 0, "");
+
+  static_assert(countl_one(UIntType{}) == 0, "");
+  static_assert(countl_one(static_cast<UIntType>(-1)) == 8, "");
+
+  static_assert(countr_zero(UIntType{}) == 8, "");
+  static_assert(countr_zero(static_cast<UIntType>(-1)) == 0, "");
+
+  static_assert(countr_one(UIntType{}) == 0, "");
+  static_assert(countr_one(static_cast<UIntType>(-1)) == 8, "");
+
+  static_assert(popcount(UIntType{}) == 0, "");
+  static_assert(popcount(UIntType{1}) == 1, "");
+  static_assert(popcount(static_cast<UIntType>(-1)) == 8, "");
+
+  static_assert(bit_width(UIntType{}) == 0, "");
+  static_assert(bit_width(UIntType{1}) == 1, "");
+  static_assert(bit_width(UIntType{3}) == 2, "");
+  static_assert(bit_width(static_cast<UIntType>(-1)) == 8, "");
+#endif
+
+  EXPECT_EQ(countl_zero(UIntType{}), 8);
+  EXPECT_EQ(countl_zero(static_cast<UIntType>(-1)), 0);
+
+  EXPECT_EQ(countl_one(UIntType{}), 0);
+  EXPECT_EQ(countl_one(static_cast<UIntType>(-1)), 8);
+
+  EXPECT_EQ(countr_zero(UIntType{}), 8);
+  EXPECT_EQ(countr_zero(static_cast<UIntType>(-1)), 0);
+
+  EXPECT_EQ(countr_one(UIntType{}), 0);
+  EXPECT_EQ(countr_one(static_cast<UIntType>(-1)), 8);
+
+  EXPECT_EQ(popcount(UIntType{}), 0);
+  EXPECT_EQ(popcount(UIntType{1}), 1);
+
+  EXPECT_FALSE(has_single_bit(UIntType{}));
+  EXPECT_FALSE(has_single_bit(static_cast<UIntType>(-1)));
+
+  EXPECT_EQ(bit_width(UIntType{}), 0);
+  EXPECT_EQ(bit_width(UIntType{1}), 1);
+  EXPECT_EQ(bit_width(UIntType{3}), 2);
+  EXPECT_EQ(bit_width(static_cast<UIntType>(-1)), 8);
+}
+
 TEST(Rotate, Left) {
   static_assert(rotl(uint8_t{0x12}, 0) == uint8_t{0x12}, "");
   static_assert(rotl(uint16_t{0x1234}, 0) == uint16_t{0x1234}, "");
diff --git a/absl/numeric/int128.cc b/absl/numeric/int128.cc
index e5526c6f..daa32b51 100644
--- a/absl/numeric/int128.cc
+++ b/absl/numeric/int128.cc
@@ -111,7 +111,7 @@ uint128 MakeUint128FromFloat(T v) {
   return MakeUint128(0, static_cast<uint64_t>(v));
 }
 
-#if defined(__clang__) && !defined(__SSE3__)
+#if defined(__clang__) && (__clang_major__ < 9) && !defined(__SSE3__)
 // Workaround for clang bug: https://bugs.llvm.org/show_bug.cgi?id=38289
 // Casting from long double to uint64_t is miscompiled and drops bits.
 // It is more work, so only use when we need the workaround.
@@ -131,7 +131,7 @@ uint128 MakeUint128FromFloat(long double v) {
   return (static_cast<uint128>(w0) << 100) | (static_cast<uint128>(w1) << 50) |
          static_cast<uint128>(w2);
 }
-#endif  // __clang__ && !__SSE3__
+#endif  // __clang__ && (__clang_major__ < 9) && !__SSE3__
 }  // namespace
 
 uint128::uint128(float v) : uint128(MakeUint128FromFloat(v)) {}
@@ -202,6 +202,10 @@ std::string Uint128ToFormattedString(uint128 v, std::ios_base::fmtflags flags) {
 
 }  // namespace
 
+std::string uint128::ToString() const {
+  return Uint128ToFormattedString(*this, std::ios_base::dec);
+}
+
 std::ostream& operator<<(std::ostream& os, uint128 v) {
   std::ios_base::fmtflags flags = os.flags();
   std::string rep = Uint128ToFormattedString(v, flags);
@@ -216,9 +220,9 @@ std::ostream& operator<<(std::ostream& os, uint128 v) {
     } else if (adjustfield == std::ios::internal &&
                (flags & std::ios::showbase) &&
                (flags & std::ios::basefield) == std::ios::hex && v != 0) {
-      rep.insert(2, count, os.fill());
+      rep.insert(size_t{2}, count, os.fill());
     } else {
-      rep.insert(0, count, os.fill());
+      rep.insert(size_t{0}, count, os.fill());
     }
   }
 
@@ -285,6 +289,14 @@ int128 operator%(int128 lhs, int128 rhs) {
 }
 #endif  // ABSL_HAVE_INTRINSIC_INT128
 
+std::string int128::ToString() const {
+  std::string rep;
+  if (Int128High64(*this) < 0) rep = "-";
+  rep.append(Uint128ToFormattedString(UnsignedAbsoluteValue(*this),
+                                      std::ios_base::dec));
+  return rep;
+}
+
 std::ostream& operator<<(std::ostream& os, int128 v) {
   std::ios_base::fmtflags flags = os.flags();
   std::string rep;
@@ -314,16 +326,16 @@ std::ostream& operator<<(std::ostream& os, int128 v) {
         break;
       case std::ios::internal:
         if (print_as_decimal && (rep[0] == '+' || rep[0] == '-')) {
-          rep.insert(1, count, os.fill());
+          rep.insert(size_t{1}, count, os.fill());
         } else if ((flags & std::ios::basefield) == std::ios::hex &&
                    (flags & std::ios::showbase) && v != 0) {
-          rep.insert(2, count, os.fill());
+          rep.insert(size_t{2}, count, os.fill());
         } else {
-          rep.insert(0, count, os.fill());
+          rep.insert(size_t{0}, count, os.fill());
         }
         break;
       default:  // std::ios::right
-        rep.insert(0, count, os.fill());
+        rep.insert(size_t{0}, count, os.fill());
         break;
     }
   }
diff --git a/absl/numeric/int128.h b/absl/numeric/int128.h
index 7a899eec..7530a793 100644
--- a/absl/numeric/int128.h
+++ b/absl/numeric/int128.h
@@ -32,6 +32,7 @@
 #include <cstring>
 #include <iosfwd>
 #include <limits>
+#include <string>
 #include <utility>
 
 #include "absl/base/config.h"
@@ -119,8 +120,8 @@ class
 #ifdef ABSL_HAVE_INTRINSIC_INT128
   constexpr uint128(__int128 v);           // NOLINT(runtime/explicit)
   constexpr uint128(unsigned __int128 v);  // NOLINT(runtime/explicit)
-#endif  // ABSL_HAVE_INTRINSIC_INT128
-  constexpr uint128(int128 v);  // NOLINT(runtime/explicit)
+#endif                                     // ABSL_HAVE_INTRINSIC_INT128
+  constexpr uint128(int128 v);             // NOLINT(runtime/explicit)
   explicit uint128(float v);
   explicit uint128(double v);
   explicit uint128(long double v);
@@ -217,9 +218,17 @@ class
     return H::combine(std::move(h), Uint128High64(v), Uint128Low64(v));
   }
 
+  // Support for absl::StrCat() etc.
+  template <typename Sink>
+  friend void AbslStringify(Sink& sink, uint128 v) {
+    sink.Append(v.ToString());
+  }
+
  private:
   constexpr uint128(uint64_t high, uint64_t low);
 
+  std::string ToString() const;
+
   // TODO(strel) Update implementation to use __int128 once all users of
   // uint128 are fixed to not depend on alignof(uint128) == 8. Also add
   // alignas(16) to class definition to keep alignment consistent across
@@ -286,9 +295,9 @@ class numeric_limits<absl::uint128> {
 #endif  // ABSL_HAVE_INTRINSIC_INT128
   static constexpr bool tinyness_before = false;
 
-  static constexpr absl::uint128 (min)() { return 0; }
+  static constexpr absl::uint128(min)() { return 0; }
   static constexpr absl::uint128 lowest() { return 0; }
-  static constexpr absl::uint128 (max)() { return absl::Uint128Max(); }
+  static constexpr absl::uint128(max)() { return absl::Uint128Max(); }
   static constexpr absl::uint128 epsilon() { return 0; }
   static constexpr absl::uint128 round_error() { return 0; }
   static constexpr absl::uint128 infinity() { return 0; }
@@ -454,9 +463,17 @@ class int128 {
     return H::combine(std::move(h), Int128High64(v), Int128Low64(v));
   }
 
+  // Support for absl::StrCat() etc.
+  template <typename Sink>
+  friend void AbslStringify(Sink& sink, int128 v) {
+    sink.Append(v.ToString());
+  }
+
  private:
   constexpr int128(int64_t high, uint64_t low);
 
+  std::string ToString() const;
+
 #if defined(ABSL_HAVE_INTRINSIC_INT128)
   __int128 v_;
 #else  // ABSL_HAVE_INTRINSIC_INT128
@@ -521,9 +538,9 @@ class numeric_limits<absl::int128> {
 #endif  // ABSL_HAVE_INTRINSIC_INT128
   static constexpr bool tinyness_before = false;
 
-  static constexpr absl::int128 (min)() { return absl::Int128Min(); }
+  static constexpr absl::int128(min)() { return absl::Int128Min(); }
   static constexpr absl::int128 lowest() { return absl::Int128Min(); }
-  static constexpr absl::int128 (max)() { return absl::Int128Max(); }
+  static constexpr absl::int128(max)() { return absl::Int128Max(); }
   static constexpr absl::int128 epsilon() { return 0; }
   static constexpr absl::int128 round_error() { return 0; }
   static constexpr absl::int128 infinity() { return 0; }
@@ -561,9 +578,7 @@ inline uint128& uint128::operator=(unsigned long v) {
 }
 
 // NOLINTNEXTLINE(runtime/int)
-inline uint128& uint128::operator=(long long v) {
-  return *this = uint128(v);
-}
+inline uint128& uint128::operator=(long long v) { return *this = uint128(v); }
 
 // NOLINTNEXTLINE(runtime/int)
 inline uint128& uint128::operator=(unsigned long long v) {
@@ -571,18 +586,14 @@ inline uint128& uint128::operator=(unsigned long long v) {
 }
 
 #ifdef ABSL_HAVE_INTRINSIC_INT128
-inline uint128& uint128::operator=(__int128 v) {
-  return *this = uint128(v);
-}
+inline uint128& uint128::operator=(__int128 v) { return *this = uint128(v); }
 
 inline uint128& uint128::operator=(unsigned __int128 v) {
   return *this = uint128(v);
 }
 #endif  // ABSL_HAVE_INTRINSIC_INT128
 
-inline uint128& uint128::operator=(int128 v) {
-  return *this = uint128(v);
-}
+inline uint128& uint128::operator=(int128 v) { return *this = uint128(v); }
 
 // Arithmetic operators.
 
@@ -637,8 +648,7 @@ constexpr uint64_t Uint128High64(uint128 v) { return v.hi_; }
 
 #if defined(ABSL_IS_LITTLE_ENDIAN)
 
-constexpr uint128::uint128(uint64_t high, uint64_t low)
-    : lo_{low}, hi_{high} {}
+constexpr uint128::uint128(uint64_t high, uint64_t low) : lo_{low}, hi_{high} {}
 
 constexpr uint128::uint128(int v)
     : lo_{static_cast<uint64_t>(v)},
@@ -670,8 +680,7 @@ constexpr uint128::uint128(int128 v)
 
 #elif defined(ABSL_IS_BIG_ENDIAN)
 
-constexpr uint128::uint128(uint64_t high, uint64_t low)
-    : hi_{high}, lo_{low} {}
+constexpr uint128::uint128(uint64_t high, uint64_t low) : hi_{high}, lo_{low} {}
 
 constexpr uint128::uint128(int v)
     : hi_{v < 0 ? (std::numeric_limits<uint64_t>::max)() : 0},
@@ -817,13 +826,9 @@ constexpr bool operator>=(uint128 lhs, uint128 rhs) { return !(lhs < rhs); }
 
 // Unary operators.
 
-constexpr inline uint128 operator+(uint128 val) {
-  return val;
-}
+constexpr inline uint128 operator+(uint128 val) { return val; }
 
-constexpr inline int128 operator+(int128 val) {
-  return val;
-}
+constexpr inline int128 operator+(int128 val) { return val; }
 
 constexpr uint128 operator-(uint128 val) {
 #if defined(ABSL_HAVE_INTRINSIC_INT128)
@@ -906,7 +911,7 @@ constexpr uint128 operator<<(uint128 lhs, int amount) {
 #else
   // uint64_t shifts of >= 64 are undefined, so we will need some
   // special-casing.
-  return amount >= 64 ? MakeUint128(Uint128Low64(lhs) << (amount - 64), 0)
+  return amount >= 64  ? MakeUint128(Uint128Low64(lhs) << (amount - 64), 0)
          : amount == 0 ? lhs
                        : MakeUint128((Uint128High64(lhs) << amount) |
                                          (Uint128Low64(lhs) >> (64 - amount)),
@@ -920,7 +925,7 @@ constexpr uint128 operator>>(uint128 lhs, int amount) {
 #else
   // uint64_t shifts of >= 64 are undefined, so we will need some
   // special-casing.
-  return amount >= 64 ? MakeUint128(0, Uint128High64(lhs) >> (amount - 64))
+  return amount >= 64  ? MakeUint128(0, Uint128High64(lhs) >> (amount - 64))
          : amount == 0 ? lhs
                        : MakeUint128(Uint128High64(lhs) >> amount,
                                      (Uint128Low64(lhs) >> amount) |
@@ -1042,27 +1047,19 @@ constexpr int128 MakeInt128(int64_t high, uint64_t low) {
 }
 
 // Assignment from integer types.
-inline int128& int128::operator=(int v) {
-  return *this = int128(v);
-}
+inline int128& int128::operator=(int v) { return *this = int128(v); }
 
-inline int128& int128::operator=(unsigned int v) {
-  return *this = int128(v);
-}
+inline int128& int128::operator=(unsigned int v) { return *this = int128(v); }
 
 inline int128& int128::operator=(long v) {  // NOLINT(runtime/int)
   return *this = int128(v);
 }
 
 // NOLINTNEXTLINE(runtime/int)
-inline int128& int128::operator=(unsigned long v) {
-  return *this = int128(v);
-}
+inline int128& int128::operator=(unsigned long v) { return *this = int128(v); }
 
 // NOLINTNEXTLINE(runtime/int)
-inline int128& int128::operator=(long long v) {
-  return *this = int128(v);
-}
+inline int128& int128::operator=(long long v) { return *this = int128(v); }
 
 // NOLINTNEXTLINE(runtime/int)
 inline int128& int128::operator=(unsigned long long v) {
diff --git a/absl/numeric/int128_have_intrinsic.inc b/absl/numeric/int128_have_intrinsic.inc
index 3945fa29..6f1ac644 100644
--- a/absl/numeric/int128_have_intrinsic.inc
+++ b/absl/numeric/int128_have_intrinsic.inc
@@ -162,9 +162,6 @@ inline int128::operator long double() const {
 }
 
 #else  // Clang on PowerPC
-// Forward declaration for conversion operators to floating point types.
-constexpr int128 operator-(int128 v);
-constexpr bool operator!=(int128 lhs, int128 rhs);
 
 inline int128::operator float() const {
   // We must convert the absolute value and then negate as needed, because
diff --git a/absl/numeric/int128_no_intrinsic.inc b/absl/numeric/int128_no_intrinsic.inc
index 8834804c..6f5d8377 100644
--- a/absl/numeric/int128_no_intrinsic.inc
+++ b/absl/numeric/int128_no_intrinsic.inc
@@ -23,8 +23,7 @@ constexpr int64_t Int128High64(int128 v) { return v.hi_; }
 
 #if defined(ABSL_IS_LITTLE_ENDIAN)
 
-constexpr int128::int128(int64_t high, uint64_t low) :
-    lo_(low), hi_(high) {}
+constexpr int128::int128(int64_t high, uint64_t low) : lo_(low), hi_(high) {}
 
 constexpr int128::int128(int v)
     : lo_{static_cast<uint64_t>(v)}, hi_{v < 0 ? ~int64_t{0} : 0} {}
@@ -44,8 +43,7 @@ constexpr int128::int128(uint128 v)
 
 #elif defined(ABSL_IS_BIG_ENDIAN)
 
-constexpr int128::int128(int64_t high, uint64_t low) :
-    hi_{high}, lo_{low} {}
+constexpr int128::int128(int64_t high, uint64_t low) : hi_{high}, lo_{low} {}
 
 constexpr int128::int128(int v)
     : hi_{v < 0 ? ~int64_t{0} : 0}, lo_{static_cast<uint64_t>(v)} {}
@@ -279,33 +277,52 @@ constexpr int128 operator^(int128 lhs, int128 rhs) {
 }
 
 constexpr int128 operator<<(int128 lhs, int amount) {
-  // int64_t shifts of >= 64 are undefined, so we need some special-casing.
-  return amount >= 64
-             ? MakeInt128(
-                   static_cast<int64_t>(Int128Low64(lhs) << (amount - 64)), 0)
-         : amount == 0
-             ? lhs
-             : MakeInt128(
-                   (Int128High64(lhs) << amount) |
-                       static_cast<int64_t>(Int128Low64(lhs) >> (64 - amount)),
-                   Int128Low64(lhs) << amount);
+  // int64_t shifts of >= 63 are undefined, so we need some special-casing.
+  assert(amount >= 0 && amount < 127);
+  if (amount <= 0) {
+    return lhs;
+  } else if (amount < 63) {
+    return MakeInt128(
+        (Int128High64(lhs) << amount) |
+            static_cast<int64_t>(Int128Low64(lhs) >> (64 - amount)),
+        Int128Low64(lhs) << amount);
+  } else if (amount == 63) {
+    return MakeInt128(((Int128High64(lhs) << 32) << 31) |
+                          static_cast<int64_t>(Int128Low64(lhs) >> 1),
+                      (Int128Low64(lhs) << 32) << 31);
+  } else if (amount == 127) {
+    return MakeInt128(static_cast<int64_t>(Int128Low64(lhs) << 63), 0);
+  } else if (amount > 127) {
+    return MakeInt128(0, 0);
+  } else {
+    // amount >= 64 && amount < 127
+    return MakeInt128(static_cast<int64_t>(Int128Low64(lhs) << (amount - 64)),
+                      0);
+  }
 }
 
 constexpr int128 operator>>(int128 lhs, int amount) {
-  // int64_t shifts of >= 64 are undefined, so we need some special-casing.
-  // The (Int128High64(lhs) >> 32) >> 32 "trick" causes the the most significant
-  // int64 to be inititialized with all zeros or all ones correctly. It takes
-  // into account whether the number is negative or positive, and whether the
-  // current architecture does arithmetic or logical right shifts for negative
-  // numbers.
-  return amount >= 64
-             ? MakeInt128(
-                   (Int128High64(lhs) >> 32) >> 32,
-                   static_cast<uint64_t>(Int128High64(lhs) >> (amount - 64)))
-         : amount == 0
-             ? lhs
-             : MakeInt128(Int128High64(lhs) >> amount,
-                          (Int128Low64(lhs) >> amount) |
-                              (static_cast<uint64_t>(Int128High64(lhs))
-                               << (64 - amount)));
+  // int64_t shifts of >= 63 are undefined, so we need some special-casing.
+  assert(amount >= 0 && amount < 127);
+  if (amount <= 0) {
+    return lhs;
+  } else if (amount < 63) {
+    return MakeInt128(
+        Int128High64(lhs) >> amount,
+        Int128Low64(lhs) >> amount | static_cast<uint64_t>(Int128High64(lhs))
+                                         << (64 - amount));
+  } else if (amount == 63) {
+    return MakeInt128((Int128High64(lhs) >> 32) >> 31,
+                      static_cast<uint64_t>(Int128High64(lhs) << 1) |
+                          (Int128Low64(lhs) >> 32) >> 31);
+
+  } else if (amount >= 127) {
+    return MakeInt128((Int128High64(lhs) >> 32) >> 31,
+                      static_cast<uint64_t>((Int128High64(lhs) >> 32) >> 31));
+  } else {
+    // amount >= 64 && amount < 127
+    return MakeInt128(
+        (Int128High64(lhs) >> 32) >> 31,
+        static_cast<uint64_t>(Int128High64(lhs) >> (amount - 64)));
+  }
 }
diff --git a/absl/numeric/int128_stream_test.cc b/absl/numeric/int128_stream_test.cc
index 81d2adee..bd937847 100644
--- a/absl/numeric/int128_stream_test.cc
+++ b/absl/numeric/int128_stream_test.cc
@@ -18,6 +18,7 @@
 #include <string>
 
 #include "gtest/gtest.h"
+#include "absl/strings/str_cat.h"
 
 namespace {
 
@@ -87,6 +88,9 @@ constexpr std::ios::fmtflags kBase = std::ios::showbase;
 constexpr std::ios::fmtflags kPos = std::ios::showpos;
 
 void CheckUint128Case(const Uint128TestCase& test_case) {
+  if (test_case.flags == kDec && test_case.width == 0) {
+    EXPECT_EQ(absl::StrCat(test_case.value), test_case.expected);
+  }
   std::ostringstream os;
   os.flags(test_case.flags);
   os.width(test_case.width);
@@ -155,6 +159,9 @@ struct Int128TestCase {
 };
 
 void CheckInt128Case(const Int128TestCase& test_case) {
+  if (test_case.flags == kDec && test_case.width == 0) {
+    EXPECT_EQ(absl::StrCat(test_case.value), test_case.expected);
+  }
   std::ostringstream os;
   os.flags(test_case.flags);
   os.width(test_case.width);
diff --git a/absl/numeric/int128_test.cc b/absl/numeric/int128_test.cc
index dd9425d7..01e3eb5c 100644
--- a/absl/numeric/int128_test.cc
+++ b/absl/numeric/int128_test.cc
@@ -32,6 +32,8 @@
 #pragma warning(disable:4146)
 #endif
 
+#define MAKE_INT128(HI, LO) absl::MakeInt128(static_cast<int64_t>(HI), LO)
+
 namespace {
 
 template <typename T>
@@ -283,8 +285,9 @@ TEST(Uint128, ConversionTests) {
   EXPECT_EQ(from_precise_double, from_precise_ints);
   EXPECT_DOUBLE_EQ(static_cast<double>(from_precise_ints), precise_double);
 
-  double approx_double = 0xffffeeeeddddcccc * std::pow(2.0, 64.0) +
-                         0xbbbbaaaa99998888;
+  double approx_double =
+      static_cast<double>(0xffffeeeeddddcccc) * std::pow(2.0, 64.0) +
+      static_cast<double>(0xbbbbaaaa99998888);
   absl::uint128 from_approx_double(approx_double);
   EXPECT_DOUBLE_EQ(static_cast<double>(from_approx_double), approx_double);
 
@@ -1245,6 +1248,27 @@ TEST(Int128, BitwiseShiftTest) {
                 absl::MakeInt128(uint64_t{1} << j, 0) >>= (j - i));
     }
   }
+
+  // Manually calculated cases with shift count for positive (val1) and negative
+  // (val2) values
+  absl::int128 val1 = MAKE_INT128(0x123456789abcdef0, 0x123456789abcdef0);
+  absl::int128 val2 = MAKE_INT128(0xfedcba0987654321, 0xfedcba0987654321);
+
+  EXPECT_EQ(val1 << 63, MAKE_INT128(0x91a2b3c4d5e6f78, 0x0));
+  EXPECT_EQ(val1 << 64, MAKE_INT128(0x123456789abcdef0, 0x0));
+  EXPECT_EQ(val2 << 63, MAKE_INT128(0xff6e5d04c3b2a190, 0x8000000000000000));
+  EXPECT_EQ(val2 << 64, MAKE_INT128(0xfedcba0987654321, 0x0));
+
+  EXPECT_EQ(val1 << 126, MAKE_INT128(0x0, 0x0));
+  EXPECT_EQ(val2 << 126, MAKE_INT128(0x4000000000000000, 0x0));
+
+  EXPECT_EQ(val1 >> 63, MAKE_INT128(0x0, 0x2468acf13579bde0));
+  EXPECT_EQ(val1 >> 64, MAKE_INT128(0x0, 0x123456789abcdef0));
+  EXPECT_EQ(val2 >> 63, MAKE_INT128(0xffffffffffffffff, 0xfdb974130eca8643));
+  EXPECT_EQ(val2 >> 64, MAKE_INT128(0xffffffffffffffff, 0xfedcba0987654321));
+
+  EXPECT_EQ(val1 >> 126, MAKE_INT128(0x0, 0x0));
+  EXPECT_EQ(val2 >> 126, MAKE_INT128(0xffffffffffffffff, 0xffffffffffffffff));
 }
 
 TEST(Int128, NumericLimitsTest) {
diff --git a/absl/random/BUILD.bazel b/absl/random/BUILD.bazel
index 133c0659..19130ff7 100644
--- a/absl/random/BUILD.bazel
+++ b/absl/random/BUILD.bazel
@@ -189,7 +189,7 @@ cc_test(
     deps = [
         ":distributions",
         ":random",
-        "//absl/base:raw_logging_internal",
+        "//absl/log",
         "//absl/numeric:representation",
         "//absl/random/internal:distribution_test_util",
         "//absl/random/internal:pcg_engine",
@@ -244,7 +244,7 @@ cc_test(
     deps = [
         ":distributions",
         ":random",
-        "//absl/base:raw_logging_internal",
+        "//absl/log",
         "//absl/random/internal:distribution_test_util",
         "//absl/random/internal:pcg_engine",
         "//absl/random/internal:sequence_urbg",
@@ -265,7 +265,7 @@ cc_test(
     deps = [
         ":distributions",
         ":random",
-        "//absl/base:raw_logging_internal",
+        "//absl/log",
         "//absl/random/internal:distribution_test_util",
         "//absl/random/internal:pcg_engine",
         "//absl/random/internal:sequence_urbg",
@@ -292,8 +292,8 @@ cc_test(
         ":distributions",
         ":random",
         "//absl/base:core_headers",
-        "//absl/base:raw_logging_internal",
         "//absl/container:flat_hash_map",
+        "//absl/log",
         "//absl/random/internal:distribution_test_util",
         "//absl/random/internal:pcg_engine",
         "//absl/random/internal:sequence_urbg",
@@ -314,7 +314,7 @@ cc_test(
         ":distributions",
         ":random",
         "//absl/base:core_headers",
-        "//absl/base:raw_logging_internal",
+        "//absl/log",
         "//absl/numeric:representation",
         "//absl/random/internal:distribution_test_util",
         "//absl/random/internal:pcg_engine",
@@ -338,7 +338,7 @@ cc_test(
         ":distributions",
         ":random",
         "//absl/base:core_headers",
-        "//absl/base:raw_logging_internal",
+        "//absl/log",
         "//absl/numeric:representation",
         "//absl/random/internal:distribution_test_util",
         "//absl/random/internal:sequence_urbg",
@@ -360,7 +360,7 @@ cc_test(
     deps = [
         ":distributions",
         ":random",
-        "//absl/base:raw_logging_internal",
+        "//absl/log",
         "//absl/random/internal:distribution_test_util",
         "//absl/random/internal:pcg_engine",
         "//absl/random/internal:sequence_urbg",
@@ -385,7 +385,7 @@ cc_test(
     deps = [
         ":distributions",
         ":random",
-        "//absl/base:raw_logging_internal",
+        "//absl/log",
         "//absl/numeric:representation",
         "//absl/random/internal:distribution_test_util",
         "//absl/random/internal:pcg_engine",
@@ -406,7 +406,7 @@ cc_test(
     deps = [
         ":distributions",
         ":random",
-        "//absl/base:raw_logging_internal",
+        "//absl/log",
         "//absl/random/internal:distribution_test_util",
         "//absl/random/internal:pcg_engine",
         "//absl/random/internal:sequence_urbg",
diff --git a/absl/random/CMakeLists.txt b/absl/random/CMakeLists.txt
index c74fd300..bd363d88 100644
--- a/absl/random/CMakeLists.txt
+++ b/absl/random/CMakeLists.txt
@@ -260,13 +260,13 @@ absl_cc_test(
   LINKOPTS
     ${ABSL_DEFAULT_LINKOPTS}
   DEPS
+    absl::log
     absl::numeric_representation
     absl::random_distributions
     absl::random_random
     absl::random_internal_distribution_test_util
     absl::random_internal_sequence_urbg
     absl::random_internal_pcg_engine
-    absl::raw_logging_internal
     absl::strings
     absl::str_format
     GTest::gmock
@@ -299,6 +299,7 @@ absl_cc_test(
     ${ABSL_TEST_COPTS}
   LINKOPTS
     ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
     absl::random_distributions
     absl::random_random
     absl::raw_logging_internal
@@ -315,12 +316,13 @@ absl_cc_test(
     ${ABSL_TEST_COPTS}
   LINKOPTS
     ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::log
     absl::random_distributions
     absl::random_internal_distribution_test_util
     absl::random_internal_pcg_engine
     absl::random_internal_sequence_urbg
     absl::random_random
-    absl::raw_logging_internal
     absl::strings
     absl::str_format
     GTest::gmock
@@ -337,12 +339,12 @@ absl_cc_test(
   LINKOPTS
     ${ABSL_DEFAULT_LINKOPTS}
   DEPS
+    absl::log
     absl::random_distributions
     absl::random_internal_distribution_test_util
     absl::random_internal_pcg_engine
     absl::random_internal_sequence_urbg
     absl::random_random
-    absl::raw_logging_internal
     absl::strings
     GTest::gmock
     GTest::gtest_main
@@ -362,10 +364,10 @@ absl_cc_test(
     absl::random_random
     absl::core_headers
     absl::flat_hash_map
+    absl::log
     absl::random_internal_distribution_test_util
     absl::random_internal_pcg_engine
     absl::random_internal_sequence_urbg
-    absl::raw_logging_internal
     absl::strings
     absl::str_format
     GTest::gmock
@@ -383,13 +385,13 @@ absl_cc_test(
     ${ABSL_DEFAULT_LINKOPTS}
   DEPS
     absl::core_headers
+    absl::log
     absl::numeric_representation
     absl::random_distributions
     absl::random_internal_distribution_test_util
     absl::random_internal_pcg_engine
     absl::random_internal_sequence_urbg
     absl::random_random
-    absl::raw_logging_internal
     absl::strings
     absl::str_format
     GTest::gmock
@@ -407,12 +409,12 @@ absl_cc_test(
     ${ABSL_DEFAULT_LINKOPTS}
   DEPS
     absl::core_headers
+    absl::log
     absl::numeric_representation
     absl::random_distributions
     absl::random_internal_distribution_test_util
     absl::random_internal_sequence_urbg
     absl::random_random
-    absl::raw_logging_internal
     absl::strings
     absl::str_format
     GTest::gmock
@@ -429,12 +431,12 @@ absl_cc_test(
   LINKOPTS
     ${ABSL_DEFAULT_LINKOPTS}
   DEPS
+    absl::log
     absl::random_distributions
     absl::random_internal_distribution_test_util
     absl::random_internal_pcg_engine
     absl::random_internal_sequence_urbg
     absl::random_random
-    absl::raw_logging_internal
     absl::strings
     GTest::gmock
     GTest::gtest_main
@@ -450,6 +452,7 @@ absl_cc_test(
   LINKOPTS
     ${ABSL_DEFAULT_LINKOPTS}
   DEPS
+    absl::log
     absl::numeric_representation
     absl::random_distributions
     absl::random_internal_distribution_test_util
@@ -471,12 +474,12 @@ absl_cc_test(
   LINKOPTS
     ${ABSL_DEFAULT_LINKOPTS}
   DEPS
+    absl::log
     absl::random_distributions
     absl::random_internal_distribution_test_util
     absl::random_internal_pcg_engine
     absl::random_internal_sequence_urbg
     absl::random_random
-    absl::raw_logging_internal
     absl::strings
     GTest::gmock
     GTest::gtest_main
@@ -1090,9 +1093,9 @@ absl_cc_test(
   LINKOPTS
     ${ABSL_DEFAULT_LINKOPTS}
   DEPS
+    absl::log
     absl::random_internal_explicit_seed_seq
     absl::random_internal_randen_engine
-    absl::raw_logging_internal
     absl::strings
     absl::time
     GTest::gmock
@@ -1142,10 +1145,10 @@ absl_cc_test(
   LINKOPTS
     ${ABSL_DEFAULT_LINKOPTS}
   DEPS
+    absl::log
     absl::random_internal_platform
     absl::random_internal_randen_hwaes
     absl::random_internal_randen_hwaes_impl
-    absl::raw_logging_internal
     absl::str_format
     GTest::gmock
     GTest::gtest
diff --git a/absl/random/benchmarks.cc b/absl/random/benchmarks.cc
index 87bbb981..0900e818 100644
--- a/absl/random/benchmarks.cc
+++ b/absl/random/benchmarks.cc
@@ -62,7 +62,7 @@ class PrecompiledSeedSeq {
  public:
   using result_type = uint32_t;
 
-  PrecompiledSeedSeq() {}
+  PrecompiledSeedSeq() = default;
 
   template <typename Iterator>
   PrecompiledSeedSeq(Iterator begin, Iterator end) {}
diff --git a/absl/random/beta_distribution_test.cc b/absl/random/beta_distribution_test.cc
index c16fbb4f..c93b2a33 100644
--- a/absl/random/beta_distribution_test.cc
+++ b/absl/random/beta_distribution_test.cc
@@ -28,7 +28,7 @@
 
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
-#include "absl/base/internal/raw_logging.h"
+#include "absl/log/log.h"
 #include "absl/numeric/internal/representation.h"
 #include "absl/random/internal/chi_square.h"
 #include "absl/random/internal/distribution_test_util.h"
@@ -107,8 +107,8 @@ TYPED_TEST(BetaDistributionInterfaceTest, SerializeTest) {
   };
   for (TypeParam alpha : kValues) {
     for (TypeParam beta : kValues) {
-      ABSL_INTERNAL_LOG(
-          INFO, absl::StrFormat("Smoke test for Beta(%a, %a)", alpha, beta));
+      LOG(INFO) << absl::StreamFormat("Smoke test for Beta(%a, %a)", alpha,
+                                      beta);
 
       param_type param(alpha, beta);
       absl::beta_distribution<TypeParam> before(alpha, beta);
@@ -327,15 +327,13 @@ bool BetaDistributionTest::SingleZTestOnMeanAndVariance(double p,
       absl::random_internal::Near("z", z_mean, 0.0, max_err) &&
       absl::random_internal::Near("z_variance", z_variance, 0.0, max_err);
   if (!pass) {
-    ABSL_INTERNAL_LOG(
-        INFO,
-        absl::StrFormat(
-            "Beta(%f, %f), "
-            "mean: sample %f, expect %f, which is %f stddevs away, "
-            "variance: sample %f, expect %f, which is %f stddevs away.",
-            alpha_, beta_, m.mean, Mean(),
-            std::abs(m.mean - Mean()) / mean_stddev, m.variance, Variance(),
-            std::abs(m.variance - Variance()) / variance_stddev));
+    LOG(INFO) << "Beta(" << alpha_ << ", " << beta_ << "), mean: sample "
+              << m.mean << ", expect " << Mean() << ", which is "
+              << std::abs(m.mean - Mean()) / mean_stddev
+              << " stddevs away, variance: sample " << m.variance << ", expect "
+              << Variance() << ", which is "
+              << std::abs(m.variance - Variance()) / variance_stddev
+              << " stddevs away.";
   }
   return pass;
 }
@@ -396,18 +394,15 @@ bool BetaDistributionTest::SingleChiSquaredTest(double p, size_t samples,
   const bool pass =
       (absl::random_internal::ChiSquarePValue(chi_square, dof) >= p);
   if (!pass) {
-    for (int i = 0; i < cutoffs.size(); i++) {
-      ABSL_INTERNAL_LOG(
-          INFO, absl::StrFormat("cutoff[%d] = %f, actual count %d, expected %d",
-                                i, cutoffs[i], counts[i],
-                                static_cast<int>(expected[i])));
+    for (size_t i = 0; i < cutoffs.size(); i++) {
+      LOG(INFO) << "cutoff[" << i << "] = " << cutoffs[i] << ", actual count "
+                << counts[i] << ", expected " << static_cast<int>(expected[i]);
     }
 
-    ABSL_INTERNAL_LOG(
-        INFO, absl::StrFormat(
-                  "Beta(%f, %f) %s %f, p = %f", alpha_, beta_,
-                  absl::random_internal::kChiSquared, chi_square,
-                  absl::random_internal::ChiSquarePValue(chi_square, dof)));
+    LOG(INFO) << "Beta(" << alpha_ << ", " << beta_ << ") "
+              << absl::random_internal::kChiSquared << " " << chi_square
+              << ", p = "
+              << absl::random_internal::ChiSquarePValue(chi_square, dof);
   }
   return pass;
 }
diff --git a/absl/random/discrete_distribution_test.cc b/absl/random/discrete_distribution_test.cc
index 415b14cc..32405ea9 100644
--- a/absl/random/discrete_distribution_test.cc
+++ b/absl/random/discrete_distribution_test.cc
@@ -26,7 +26,7 @@
 
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
-#include "absl/base/internal/raw_logging.h"
+#include "absl/log/log.h"
 #include "absl/random/internal/chi_square.h"
 #include "absl/random/internal/distribution_test_util.h"
 #include "absl/random/internal/pcg_engine.h"
@@ -146,7 +146,7 @@ TEST(DiscreteDistributionTest, ChiSquaredTest50) {
   using absl::random_internal::kChiSquared;
 
   constexpr size_t kTrials = 10000;
-  constexpr int kBuckets = 50;  // inclusive, so actally +1
+  constexpr int kBuckets = 50;  // inclusive, so actually +1
 
   // 1-in-100000 threshold, but remember, there are about 8 tests
   // in this file. And the test could fail for other reasons.
@@ -194,7 +194,7 @@ TEST(DiscreteDistributionTest, ChiSquaredTest50) {
     absl::StrAppend(&msg, kChiSquared, " p-value ", p_value, "\n");
     absl::StrAppend(&msg, "High ", kChiSquared, " value: ", chi_square, " > ",
                     kThreshold);
-    ABSL_RAW_LOG(INFO, "%s", msg.c_str());
+    LOG(INFO) << msg;
     FAIL() << msg;
   }
 }
diff --git a/absl/random/exponential_distribution_test.cc b/absl/random/exponential_distribution_test.cc
index 3c44d9ec..fb9a0d16 100644
--- a/absl/random/exponential_distribution_test.cc
+++ b/absl/random/exponential_distribution_test.cc
@@ -29,8 +29,8 @@
 
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
-#include "absl/base/internal/raw_logging.h"
 #include "absl/base/macros.h"
+#include "absl/log/log.h"
 #include "absl/numeric/internal/representation.h"
 #include "absl/random/internal/chi_square.h"
 #include "absl/random/internal/distribution_test_util.h"
@@ -115,9 +115,8 @@ TYPED_TEST(ExponentialDistributionTypedTest, SerializeTest) {
       if (sample < sample_min) sample_min = sample;
     }
     if (!std::is_same<TypeParam, long double>::value) {
-      ABSL_INTERNAL_LOG(INFO,
-                        absl::StrFormat("Range {%f}: %f, %f, lambda=%f", lambda,
-                                        sample_min, sample_max, lambda));
+      LOG(INFO) << "Range {" << lambda << "}: " << sample_min << ", "
+                << sample_max << ", lambda=" << lambda;
     }
 
     std::stringstream ss;
@@ -219,17 +218,16 @@ bool ExponentialDistributionTests::SingleZTest(const double p,
   const bool pass = absl::random_internal::Near("z", z, 0.0, max_err);
 
   if (!pass) {
-    ABSL_INTERNAL_LOG(
-        INFO, absl::StrFormat("p=%f max_err=%f\n"
-                              " lambda=%f\n"
-                              " mean=%f vs. %f\n"
-                              " stddev=%f vs. %f\n"
-                              " skewness=%f vs. %f\n"
-                              " kurtosis=%f vs. %f\n"
-                              " z=%f vs. 0",
-                              p, max_err, lambda(), m.mean, mean(),
-                              std::sqrt(m.variance), stddev(), m.skewness,
-                              skew(), m.kurtosis, kurtosis(), z));
+    // clang-format off
+    LOG(INFO)
+        << "p=" << p << " max_err=" << max_err << "\n"
+           " lambda=" << lambda() << "\n"
+           " mean=" << m.mean << " vs. " << mean() << "\n"
+           " stddev=" << std::sqrt(m.variance) << " vs. " << stddev() << "\n"
+           " skewness=" << m.skewness << " vs. " << skew() << "\n"
+           " kurtosis=" << m.kurtosis << " vs. " << kurtosis() << "\n"
+           " z=" << z << " vs. 0";
+    // clang-format on
   }
   return pass;
 }
@@ -274,16 +272,16 @@ double ExponentialDistributionTests::SingleChiSquaredTest() {
   double p = absl::random_internal::ChiSquarePValue(chi_square, dof);
 
   if (chi_square > threshold) {
-    for (int i = 0; i < cutoffs.size(); i++) {
-      ABSL_INTERNAL_LOG(
-          INFO, absl::StrFormat("%d : (%f) = %d", i, cutoffs[i], counts[i]));
+    for (size_t i = 0; i < cutoffs.size(); i++) {
+      LOG(INFO) << i << " : (" << cutoffs[i] << ") = " << counts[i];
     }
 
-    ABSL_INTERNAL_LOG(INFO,
-                      absl::StrCat("lambda ", lambda(), "\n",     //
-                                   " expected ", expected, "\n",  //
-                                   kChiSquared, " ", chi_square, " (", p, ")\n",
-                                   kChiSquared, " @ 0.98 = ", threshold));
+    // clang-format off
+    LOG(INFO) << "lambda " << lambda() << "\n"
+                 " expected " << expected << "\n"
+              << kChiSquared << " " << chi_square << " (" << p << ")\n"
+              << kChiSquared << " @ 0.98 = " << threshold;
+    // clang-format on
   }
   return p;
 }
diff --git a/absl/random/gaussian_distribution_test.cc b/absl/random/gaussian_distribution_test.cc
index 4584ac92..bad3476f 100644
--- a/absl/random/gaussian_distribution_test.cc
+++ b/absl/random/gaussian_distribution_test.cc
@@ -26,8 +26,8 @@
 
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
-#include "absl/base/internal/raw_logging.h"
 #include "absl/base/macros.h"
+#include "absl/log/log.h"
 #include "absl/numeric/internal/representation.h"
 #include "absl/random/internal/chi_square.h"
 #include "absl/random/internal/distribution_test_util.h"
@@ -116,9 +116,8 @@ TYPED_TEST(GaussianDistributionInterfaceTest, SerializeTest) {
           EXPECT_LE(sample, before.max()) << before;
         }
         if (!std::is_same<TypeParam, long double>::value) {
-          ABSL_INTERNAL_LOG(
-              INFO, absl::StrFormat("Range{%f, %f}: %f, %f", mean, stddev,
-                                    sample_min, sample_max));
+          LOG(INFO) << "Range{" << mean << ", " << stddev << "}: " << sample_min
+                    << ", " << sample_max;
         }
 
         std::stringstream ss;
@@ -240,17 +239,16 @@ bool GaussianDistributionTests::SingleZTest(const double p,
       (std::pow(m.skewness, 2.0) + std::pow(m.kurtosis - 3.0, 2.0) / 4.0);
 
   if (!pass || jb > 9.21) {
-    ABSL_INTERNAL_LOG(
-        INFO, absl::StrFormat("p=%f max_err=%f\n"
-                              " mean=%f vs. %f\n"
-                              " stddev=%f vs. %f\n"
-                              " skewness=%f vs. %f\n"
-                              " kurtosis=%f vs. %f\n"
-                              " z=%f vs. 0\n"
-                              " jb=%f vs. 9.21",
-                              p, max_err, m.mean, mean(), std::sqrt(m.variance),
-                              stddev(), m.skewness, skew(), m.kurtosis,
-                              kurtosis(), z, jb));
+    // clang-format off
+    LOG(INFO)
+        << "p=" << p << " max_err=" << max_err << "\n"
+           " mean=" << m.mean << " vs. " << mean() << "\n"
+           " stddev=" << std::sqrt(m.variance) << " vs. " << stddev() << "\n"
+           " skewness=" << m.skewness << " vs. " << skew() << "\n"
+           " kurtosis=" << m.kurtosis << " vs. " << kurtosis() << "\n"
+           " z=" << z << " vs. 0\n"
+           " jb=" << jb << " vs. 9.21";
+    // clang-format on
   }
   return pass;
 }
@@ -297,16 +295,16 @@ double GaussianDistributionTests::SingleChiSquaredTest() {
 
   // Log if the chi_square value is above the threshold.
   if (chi_square > threshold) {
-    for (int i = 0; i < cutoffs.size(); i++) {
-      ABSL_INTERNAL_LOG(
-          INFO, absl::StrFormat("%d : (%f) = %d", i, cutoffs[i], counts[i]));
+    for (size_t i = 0; i < cutoffs.size(); i++) {
+      LOG(INFO) << i << " : (" << cutoffs[i] << ") = " << counts[i];
     }
 
-    ABSL_INTERNAL_LOG(
-        INFO, absl::StrCat("mean=", mean(), " stddev=", stddev(), "\n",   //
-                           " expected ", expected, "\n",                  //
-                           kChiSquared, " ", chi_square, " (", p, ")\n",  //
-                           kChiSquared, " @ 0.98 = ", threshold));
+    // clang-format off
+    LOG(INFO) << "mean=" << mean() << " stddev=" << stddev() << "\n"
+                 " expected " << expected << "\n"
+              << kChiSquared << " " << chi_square << " (" << p << ")\n"
+              << kChiSquared << " @ 0.98 = " << threshold;
+    // clang-format on
   }
   return p;
 }
diff --git a/absl/random/generators_test.cc b/absl/random/generators_test.cc
index 14fd24e9..20091309 100644
--- a/absl/random/generators_test.cc
+++ b/absl/random/generators_test.cc
@@ -49,7 +49,7 @@ void TestUniform(URBG* gen) {
   // (a, b) semantics, inferred types.
   absl::Uniform(absl::IntervalOpenOpen, *gen, 0, 1.0);  // Promoted to double
 
-  // Explict overriding of types.
+  // Explicit overriding of types.
   absl::Uniform<int>(*gen, 0, 100);
   absl::Uniform<int8_t>(*gen, 0, 100);
   absl::Uniform<int16_t>(*gen, 0, 100);
@@ -117,6 +117,7 @@ void TestBernoulli(URBG* gen) {
   absl::Bernoulli(*gen, 0.5);
 }
 
+
 template <typename URBG>
 void TestZipf(URBG* gen) {
   absl::Zipf<int>(*gen, 100);
diff --git a/absl/random/internal/BUILD.bazel b/absl/random/internal/BUILD.bazel
index 81ca669b..37f4d6e2 100644
--- a/absl/random/internal/BUILD.bazel
+++ b/absl/random/internal/BUILD.bazel
@@ -82,6 +82,10 @@ cc_library(
     linkopts = ABSL_DEFAULT_LINKOPTS + select({
         "//absl:msvc_compiler": ["-DEFAULTLIB:bcrypt.lib"],
         "//absl:clang-cl_compiler": ["-DEFAULTLIB:bcrypt.lib"],
+        "//absl:mingw_compiler": [
+            "-DEFAULTLIB:bcrypt.lib",
+            "-lbcrypt",
+        ],
         "//conditions:default": [],
     }),
     deps = [
@@ -597,7 +601,7 @@ cc_test(
     deps = [
         ":explicit_seed_seq",
         ":randen_engine",
-        "//absl/base:raw_logging_internal",
+        "//absl/log",
         "//absl/strings",
         "//absl/time",
         "@com_google_googletest//:gtest_main",
@@ -642,7 +646,7 @@ cc_test(
         ":platform",
         ":randen_hwaes",
         ":randen_hwaes_impl",  # build_cleaner: keep
-        "//absl/base:raw_logging_internal",
+        "//absl/log",
         "//absl/strings:str_format",
         "@com_google_googletest//:gtest",
     ],
@@ -703,8 +707,10 @@ cc_test(
     ],
     deps = [
         ":nanobenchmark",
-        "//absl/base:raw_logging_internal",
+        "//absl/log",
+        "//absl/log:check",
         "//absl/strings",
+        "//absl/strings:str_format",
     ],
 )
 
diff --git a/absl/random/internal/distribution_test_util.cc b/absl/random/internal/distribution_test_util.cc
index e9005658..9fa37bd6 100644
--- a/absl/random/internal/distribution_test_util.cc
+++ b/absl/random/internal/distribution_test_util.cc
@@ -213,7 +213,7 @@ double BetaIncompleteImpl(const double x, const double p, const double q,
   double result = 1.;
   int ns = static_cast<int>(q + xc * psq);
 
-  // Use the soper reduction forumla.
+  // Use the soper reduction formula.
   double rx = (ns == 0) ? x : x / xc;
   double temp = q - ai;
   for (;;) {
@@ -236,7 +236,7 @@ double BetaIncompleteImpl(const double x, const double p, const double q,
     }
   }
 
-  // NOTE: See also TOMS Alogrithm 708.
+  // NOTE: See also TOMS Algorithm 708.
   // http://www.netlib.org/toms/index.html
   //
   // NOTE: The NWSC library also includes BRATIO / ISUBX (p87)
@@ -247,7 +247,7 @@ double BetaIncompleteImpl(const double x, const double p, const double q,
 // https://www.jstor.org/stable/2346798?read-now=1&seq=4#page_scan_tab_contents
 // https://www.jstor.org/stable/2346887?seq=1#page_scan_tab_contents
 //
-// XINBTA(p, q, beta, alhpa)
+// XINBTA(p, q, beta, alpha)
 //  p:     the value of the parameter p.
 //  q:     the value of the parameter q.
 //  beta:  the value of ln B(p, q)
diff --git a/absl/random/internal/fast_uniform_bits.h b/absl/random/internal/fast_uniform_bits.h
index 8d8ed045..83ee5c0f 100644
--- a/absl/random/internal/fast_uniform_bits.h
+++ b/absl/random/internal/fast_uniform_bits.h
@@ -57,9 +57,10 @@ constexpr UIntType IntegerLog2(UIntType n) {
 // `PowerOfTwoVariate(urbg)`.
 template <typename URBG>
 constexpr size_t NumBits() {
-  return RangeSize<URBG>() == 0
-             ? std::numeric_limits<typename URBG::result_type>::digits
-             : IntegerLog2(RangeSize<URBG>());
+  return static_cast<size_t>(
+      RangeSize<URBG>() == 0
+          ? std::numeric_limits<typename URBG::result_type>::digits
+          : IntegerLog2(RangeSize<URBG>()));
 }
 
 // Given a shift value `n`, constructs a mask with exactly the low `n` bits set.
diff --git a/absl/random/internal/fast_uniform_bits_test.cc b/absl/random/internal/fast_uniform_bits_test.cc
index cee702df..34c25206 100644
--- a/absl/random/internal/fast_uniform_bits_test.cc
+++ b/absl/random/internal/fast_uniform_bits_test.cc
@@ -167,7 +167,7 @@ TEST(FastUniformBitsTest, RangeSize) {
              FakeUrbg<uint64_t, 0, (std::numeric_limits<uint64_t>::max)()>>()));
 }
 
-// The constants need to be choosen so that an infinite rejection loop doesn't
+// The constants need to be chosen so that an infinite rejection loop doesn't
 // happen...
 using Urng1_5bit = FakeUrbg<uint8_t, 0, 2, 0>;  // ~1.5 bits (range 3)
 using Urng4bits = FakeUrbg<uint8_t, 1, 0x10, 2>;
diff --git a/absl/random/internal/generate_real.h b/absl/random/internal/generate_real.h
index b569450c..9a6f4005 100644
--- a/absl/random/internal/generate_real.h
+++ b/absl/random/internal/generate_real.h
@@ -78,7 +78,7 @@ inline RealType GenerateRealFromBits(uint64_t bits, int exp_bias = 0) {
       "GenerateRealFromBits must be parameterized by either float or double.");
 
   static_assert(sizeof(uint_type) == sizeof(real_type),
-                "Mismatched unsinged and real types.");
+                "Mismatched unsigned and real types.");
 
   static_assert((std::numeric_limits<real_type>::is_iec559 &&
                  std::numeric_limits<real_type>::radix == 2),
diff --git a/absl/random/internal/iostream_state_saver_test.cc b/absl/random/internal/iostream_state_saver_test.cc
index 6e66266c..ea9d2af0 100644
--- a/absl/random/internal/iostream_state_saver_test.cc
+++ b/absl/random/internal/iostream_state_saver_test.cc
@@ -345,8 +345,9 @@ TEST(IOStreamStateSaver, RoundTripLongDoubles) {
     }
 
     // Avoid undefined behavior (overflow/underflow).
-    if (dd <= std::numeric_limits<int64_t>::max() &&
-        dd >= std::numeric_limits<int64_t>::lowest()) {
+    if (dd <= static_cast<long double>(std::numeric_limits<int64_t>::max()) &&
+        dd >=
+            static_cast<long double>(std::numeric_limits<int64_t>::lowest())) {
       int64_t x = static_cast<int64_t>(dd);
       EXPECT_EQ(x, StreamRoundTrip<int64_t>(x));
     }
diff --git a/absl/random/internal/mock_helpers.h b/absl/random/internal/mock_helpers.h
index 882b0518..a7a97bfc 100644
--- a/absl/random/internal/mock_helpers.h
+++ b/absl/random/internal/mock_helpers.h
@@ -101,7 +101,7 @@ class MockHelpers {
   template <typename KeyT, typename URBG, typename... Args>
   static auto MaybeInvokeMock(URBG* urbg, Args&&... args)
       -> absl::optional<typename KeySignature<KeyT>::result_type> {
-    // Use function overloading to dispatch to the implemenation since
+    // Use function overloading to dispatch to the implementation since
     // more modern patterns (e.g. require + constexpr) are not supported in all
     // compiler configurations.
     return InvokeMockImpl<KeyT, typename KeySignature<KeyT>::result_type,
diff --git a/absl/random/internal/nanobenchmark.cc b/absl/random/internal/nanobenchmark.cc
index c9181813..0f31a7d5 100644
--- a/absl/random/internal/nanobenchmark.cc
+++ b/absl/random/internal/nanobenchmark.cc
@@ -361,7 +361,7 @@ void CountingSort(T* values, size_t num_values) {
   // Write that many copies of each unique value to the array.
   T* ABSL_RANDOM_INTERNAL_RESTRICT p = values;
   for (const auto& value_count : unique) {
-    std::fill(p, p + value_count.second, value_count.first);
+    std::fill_n(p, value_count.second, value_count.first);
     p += value_count.second;
   }
   ABSL_RAW_CHECK(p == values + num_values, "Did not produce enough output");
diff --git a/absl/random/internal/nanobenchmark_test.cc b/absl/random/internal/nanobenchmark_test.cc
index f1571e26..d4f1028d 100644
--- a/absl/random/internal/nanobenchmark_test.cc
+++ b/absl/random/internal/nanobenchmark_test.cc
@@ -14,8 +14,10 @@
 
 #include "absl/random/internal/nanobenchmark.h"
 
-#include "absl/base/internal/raw_logging.h"
+#include "absl/log/check.h"
+#include "absl/log/log.h"
 #include "absl/strings/numbers.h"
+#include "absl/strings/str_format.h"
 
 namespace absl {
 ABSL_NAMESPACE_BEGIN
@@ -36,16 +38,16 @@ void MeasureDiv(const FuncInput (&inputs)[N]) {
   params.max_evals = 6;  // avoid test timeout
   const size_t num_results = Measure(&Div, nullptr, inputs, N, results, params);
   if (num_results == 0) {
-    ABSL_RAW_LOG(
-        WARNING,
-        "WARNING: Measurement failed, should not happen when using "
-        "PinThreadToCPU unless the region to measure takes > 1 second.\n");
+    LOG(WARNING)
+        << "WARNING: Measurement failed, should not happen when using "
+           "PinThreadToCPU unless the region to measure takes > 1 second.";
     return;
   }
   for (size_t i = 0; i < num_results; ++i) {
-    ABSL_RAW_LOG(INFO, "%5zu: %6.2f ticks; MAD=%4.2f%%\n", results[i].input,
-                 results[i].ticks, results[i].variability * 100.0);
-    ABSL_RAW_CHECK(results[i].ticks != 0.0f, "Zero duration");
+    LOG(INFO) << absl::StreamFormat("%5u: %6.2f ticks; MAD=%4.2f%%\n",
+                                    results[i].input, results[i].ticks,
+                                    results[i].variability * 100.0);
+    CHECK_NE(results[i].ticks, 0.0f) << "Zero duration";
   }
 }
 
@@ -54,7 +56,7 @@ void RunAll(const int argc, char* argv[]) {
   int cpu = -1;
   if (argc == 2) {
     if (!absl::SimpleAtoi(argv[1], &cpu)) {
-      ABSL_RAW_LOG(FATAL, "The optional argument must be a CPU number >= 0.\n");
+      LOG(FATAL) << "The optional argument must be a CPU number >= 0.";
     }
   }
   PinThreadToCPU(cpu);
diff --git a/absl/random/internal/platform.h b/absl/random/internal/platform.h
index bbdb4e62..d779f481 100644
--- a/absl/random/internal/platform.h
+++ b/absl/random/internal/platform.h
@@ -131,7 +131,7 @@
 
 // ABSL_RANDOM_INTERNAL_AES_DISPATCH indicates whether the currently active
 // platform has, or should use run-time dispatch for selecting the
-// acclerated Randen implementation.
+// accelerated Randen implementation.
 #define ABSL_RANDOM_INTERNAL_AES_DISPATCH 0
 
 #if defined(ABSL_ARCH_X86_64)
diff --git a/absl/random/internal/randen_benchmarks.cc b/absl/random/internal/randen_benchmarks.cc
index f589172c..ec086cea 100644
--- a/absl/random/internal/randen_benchmarks.cc
+++ b/absl/random/internal/randen_benchmarks.cc
@@ -47,8 +47,10 @@ static constexpr size_t kSeedSizeT = Randen::kSeedBytes / sizeof(uint32_t);
 // Randen implementation benchmarks.
 template <typename T>
 struct AbsorbFn : public T {
-  mutable uint64_t state[kStateSizeT] = {};
-  mutable uint32_t seed[kSeedSizeT] = {};
+  // These are both cast to uint128* in the RandenHwAes implementation, so
+  // ensure they are 16 byte aligned.
+  alignas(16) mutable uint64_t state[kStateSizeT] = {};
+  alignas(16) mutable uint32_t seed[kSeedSizeT] = {};
 
   static constexpr size_t bytes() { return sizeof(seed); }
 
diff --git a/absl/random/internal/randen_detect.cc b/absl/random/internal/randen_detect.cc
index 6dababa3..bdeab877 100644
--- a/absl/random/internal/randen_detect.cc
+++ b/absl/random/internal/randen_detect.cc
@@ -45,6 +45,10 @@
 #if defined(ABSL_INTERNAL_USE_X86_CPUID)
 #if defined(_WIN32) || defined(_WIN64)
 #include <intrin.h>  // NOLINT(build/include_order)
+#elif ABSL_HAVE_BUILTIN(__cpuid)
+// MSVC-equivalent __cpuid intrinsic declaration for clang-like compilers
+// for non-Windows build environments.
+extern void __cpuid(int[4], int);
 #else
 // MSVC-equivalent __cpuid intrinsic function.
 static void __cpuid(int cpu_info[4], int info_type) {
diff --git a/absl/random/internal/randen_engine.h b/absl/random/internal/randen_engine.h
index b4708664..fe2d9f6c 100644
--- a/absl/random/internal/randen_engine.h
+++ b/absl/random/internal/randen_engine.h
@@ -142,7 +142,7 @@ class alignas(8) randen_engine {
       // The Randen paper suggests preferentially initializing even-numbered
       // 128-bit vectors of the randen state (there are 16 such vectors).
       // The seed data is merged into the state offset by 128-bits, which
-      // implies prefering seed bytes [16..31, ..., 208..223]. Since the
+      // implies preferring seed bytes [16..31, ..., 208..223]. Since the
       // buffer is 32-bit values, we swap the corresponding buffer positions in
       // 128-bit chunks.
       size_t dst = kBufferSize;
diff --git a/absl/random/internal/randen_engine_test.cc b/absl/random/internal/randen_engine_test.cc
index c8e7685b..a94f4916 100644
--- a/absl/random/internal/randen_engine_test.cc
+++ b/absl/random/internal/randen_engine_test.cc
@@ -21,7 +21,7 @@
 
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
-#include "absl/base/internal/raw_logging.h"
+#include "absl/log/log.h"
 #include "absl/random/internal/explicit_seed_seq.h"
 #include "absl/strings/str_cat.h"
 #include "absl/time/clock.h"
@@ -645,9 +645,8 @@ TEST(RandenTest, IsFastOrSlow) {
   }
   auto duration = absl::GetCurrentTimeNanos() - start;
 
-  ABSL_INTERNAL_LOG(INFO, absl::StrCat(static_cast<double>(duration) /
-                                           static_cast<double>(kCount),
-                                       "ns"));
+  LOG(INFO) << static_cast<double>(duration) / static_cast<double>(kCount)
+            << "ns";
 
   EXPECT_GT(sum, 0);
   EXPECT_GE(duration, kCount);  // Should be slower than 1ns per call.
diff --git a/absl/random/internal/randen_hwaes.cc b/absl/random/internal/randen_hwaes.cc
index fee6677c..f535f4c5 100644
--- a/absl/random/internal/randen_hwaes.cc
+++ b/absl/random/internal/randen_hwaes.cc
@@ -31,7 +31,7 @@
 // a hardware accelerated implementation of randen, or whether it
 // will contain stubs that exit the process.
 #if ABSL_HAVE_ACCELERATED_AES
-// The following plaforms have implemented RandenHwAes.
+// The following platforms have implemented RandenHwAes.
 #if defined(ABSL_ARCH_X86_64) || defined(ABSL_ARCH_X86_32) || \
     defined(ABSL_ARCH_PPC) || defined(ABSL_ARCH_ARM) ||       \
     defined(ABSL_ARCH_AARCH64)
diff --git a/absl/random/internal/randen_hwaes_test.cc b/absl/random/internal/randen_hwaes_test.cc
index 2348b55c..00d96efd 100644
--- a/absl/random/internal/randen_hwaes_test.cc
+++ b/absl/random/internal/randen_hwaes_test.cc
@@ -16,7 +16,7 @@
 
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
-#include "absl/base/internal/raw_logging.h"
+#include "absl/log/log.h"
 #include "absl/random/internal/platform.h"
 #include "absl/random/internal/randen_detect.h"
 #include "absl/random/internal/randen_traits.h"
@@ -67,32 +67,32 @@ TEST(RandenHwAesTest, Default) {
 int main(int argc, char* argv[]) {
   testing::InitGoogleTest(&argc, argv);
 
-  ABSL_RAW_LOG(INFO, "ABSL_HAVE_ACCELERATED_AES=%d", ABSL_HAVE_ACCELERATED_AES);
-  ABSL_RAW_LOG(INFO, "ABSL_RANDOM_INTERNAL_AES_DISPATCH=%d",
-               ABSL_RANDOM_INTERNAL_AES_DISPATCH);
+  LOG(INFO) << "ABSL_HAVE_ACCELERATED_AES=" << ABSL_HAVE_ACCELERATED_AES;
+  LOG(INFO) << "ABSL_RANDOM_INTERNAL_AES_DISPATCH="
+            << ABSL_RANDOM_INTERNAL_AES_DISPATCH;
 
 #if defined(ABSL_ARCH_X86_64)
-  ABSL_RAW_LOG(INFO, "ABSL_ARCH_X86_64");
+  LOG(INFO) << "ABSL_ARCH_X86_64";
 #elif defined(ABSL_ARCH_X86_32)
-  ABSL_RAW_LOG(INFO, "ABSL_ARCH_X86_32");
+  LOG(INFO) << "ABSL_ARCH_X86_32";
 #elif defined(ABSL_ARCH_AARCH64)
-  ABSL_RAW_LOG(INFO, "ABSL_ARCH_AARCH64");
+  LOG(INFO) << "ABSL_ARCH_AARCH64";
 #elif defined(ABSL_ARCH_ARM)
-  ABSL_RAW_LOG(INFO, "ABSL_ARCH_ARM");
+  LOG(INFO) << "ABSL_ARCH_ARM";
 #elif defined(ABSL_ARCH_PPC)
-  ABSL_RAW_LOG(INFO, "ABSL_ARCH_PPC");
+  LOG(INFO) << "ABSL_ARCH_PPC";
 #else
-  ABSL_RAW_LOG(INFO, "ARCH Unknown");
+  LOG(INFO) << "ARCH Unknown";
 #endif
 
   int x = absl::random_internal::HasRandenHwAesImplementation();
-  ABSL_RAW_LOG(INFO, "HasRandenHwAesImplementation = %d", x);
+  LOG(INFO) << "HasRandenHwAesImplementation = " << x;
 
   int y = absl::random_internal::CPUSupportsRandenHwAes();
-  ABSL_RAW_LOG(INFO, "CPUSupportsRandenHwAes = %d", x);
+  LOG(INFO) << "CPUSupportsRandenHwAes = " << x;
 
   if (!x || !y) {
-    ABSL_RAW_LOG(INFO, "Skipping Randen HWAES tests.");
+    LOG(INFO) << "Skipping Randen HWAES tests.";
     return 0;
   }
   return RUN_ALL_TESTS();
diff --git a/absl/random/internal/uniform_helper.h b/absl/random/internal/uniform_helper.h
index e68b82ee..db737e13 100644
--- a/absl/random/internal/uniform_helper.h
+++ b/absl/random/internal/uniform_helper.h
@@ -217,7 +217,7 @@ using UniformDistribution =
 // UniformDistributionWrapper is used as the underlying distribution type
 // by the absl::Uniform template function. It selects the proper Abseil
 // uniform distribution and provides constructor overloads that match the
-// expected parameter order as well as adjusting distribtuion bounds based
+// expected parameter order as well as adjusting distribution bounds based
 // on the tag.
 template <typename NumType>
 struct UniformDistributionWrapper : public UniformDistribution<NumType> {
diff --git a/absl/random/log_uniform_int_distribution_test.cc b/absl/random/log_uniform_int_distribution_test.cc
index 0d0fcb95..5df3edac 100644
--- a/absl/random/log_uniform_int_distribution_test.cc
+++ b/absl/random/log_uniform_int_distribution_test.cc
@@ -24,7 +24,7 @@
 
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
-#include "absl/base/internal/raw_logging.h"
+#include "absl/log/log.h"
 #include "absl/random/internal/chi_square.h"
 #include "absl/random/internal/distribution_test_util.h"
 #include "absl/random/internal/pcg_engine.h"
@@ -108,8 +108,7 @@ TYPED_TEST(LogUniformIntDistributionTypeTest, SerializeTest) {
       if (sample > sample_max) sample_max = sample;
       if (sample < sample_min) sample_min = sample;
     }
-    ABSL_INTERNAL_LOG(INFO,
-                      absl::StrCat("Range: ", +sample_min, ", ", +sample_max));
+    LOG(INFO) << "Range: " << sample_min << ", " << sample_max;
   }
 }
 
@@ -182,16 +181,14 @@ double LogUniformIntChiSquaredTest::ChiSquaredTestImpl() {
   const double p = absl::random_internal::ChiSquarePValue(chi_square, dof);
 
   if (chi_square > threshold) {
-    ABSL_INTERNAL_LOG(INFO, "values");
+    LOG(INFO) << "values";
     for (size_t i = 0; i < buckets.size(); i++) {
-      ABSL_INTERNAL_LOG(INFO, absl::StrCat(i, ": ", buckets[i]));
+      LOG(INFO) << i << ": " << buckets[i];
     }
-    ABSL_INTERNAL_LOG(INFO,
-                      absl::StrFormat("trials=%d\n"
-                                      "%s(data, %d) = %f (%f)\n"
-                                      "%s @ 0.98 = %f",
-                                      trials, kChiSquared, dof, chi_square, p,
-                                      kChiSquared, threshold));
+    LOG(INFO) << "trials=" << trials << "\n"
+              << kChiSquared << "(data, " << dof << ") = " << chi_square << " ("
+              << p << ")\n"
+              << kChiSquared << " @ 0.98 = " << threshold;
   }
   return p;
 }
diff --git a/absl/random/poisson_distribution_test.cc b/absl/random/poisson_distribution_test.cc
index 4f585b9b..54755960 100644
--- a/absl/random/poisson_distribution_test.cc
+++ b/absl/random/poisson_distribution_test.cc
@@ -25,9 +25,9 @@
 
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
-#include "absl/base/internal/raw_logging.h"
 #include "absl/base/macros.h"
 #include "absl/container/flat_hash_map.h"
+#include "absl/log/log.h"
 #include "absl/random/internal/chi_square.h"
 #include "absl/random/internal/distribution_test_util.h"
 #include "absl/random/internal/pcg_engine.h"
@@ -134,8 +134,8 @@ TYPED_TEST(PoissonDistributionInterfaceTest, SerializeTest) {
       if (sample < sample_min) sample_min = sample;
     }
 
-    ABSL_INTERNAL_LOG(INFO, absl::StrCat("Range {", param.mean(), "}: ",
-                                         +sample_min, ", ", +sample_max));
+    LOG(INFO) << "Range {" << param.mean() << "}: " << sample_min << ", "
+              << sample_max;
 
     // Validate stream serialization.
     std::stringstream ss;
@@ -188,10 +188,9 @@ class PoissonModel {
   }
 
   void LogCDF() {
-    ABSL_INTERNAL_LOG(INFO, absl::StrCat("CDF (mean = ", mean_, ")"));
+    LOG(INFO) << "CDF (mean = " << mean_ << ")";
     for (const auto c : cdf_) {
-      ABSL_INTERNAL_LOG(INFO,
-                        absl::StrCat(c.index, ": pmf=", c.pmf, " cdf=", c.cdf));
+      LOG(INFO) << c.index << ": pmf=" << c.pmf << " cdf=" << c.cdf;
     }
   }
 
@@ -286,16 +285,15 @@ bool PoissonDistributionZTest::SingleZTest(const double p,
   const bool pass = absl::random_internal::Near("z", z, 0.0, max_err);
 
   if (!pass) {
-    ABSL_INTERNAL_LOG(
-        INFO, absl::StrFormat("p=%f max_err=%f\n"
-                              " mean=%f vs. %f\n"
-                              " stddev=%f vs. %f\n"
-                              " skewness=%f vs. %f\n"
-                              " kurtosis=%f vs. %f\n"
-                              " z=%f",
-                              p, max_err, m.mean, mean(), std::sqrt(m.variance),
-                              stddev(), m.skewness, skew(), m.kurtosis,
-                              kurtosis(), z));
+    // clang-format off
+    LOG(INFO)
+        << "p=" << p << " max_err=" << max_err << "\n"
+           " mean=" << m.mean << " vs. " << mean() << "\n"
+           " stddev=" << std::sqrt(m.variance) << " vs. " << stddev() << "\n"
+           " skewness=" << m.skewness << " vs. " << skew() << "\n"
+           " kurtosis=" << m.kurtosis << " vs. " << kurtosis() << "\n"
+           " z=" << z;
+    // clang-format on
   }
   return pass;
 }
@@ -439,17 +437,16 @@ double PoissonDistributionChiSquaredTest::ChiSquaredTestImpl() {
   if (chi_square > threshold) {
     LogCDF();
 
-    ABSL_INTERNAL_LOG(INFO, absl::StrCat("VALUES  buckets=", counts.size(),
-                                         "  samples=", kSamples));
+    LOG(INFO) << "VALUES  buckets=" << counts.size()
+              << "  samples=" << kSamples;
     for (size_t i = 0; i < counts.size(); i++) {
-      ABSL_INTERNAL_LOG(
-          INFO, absl::StrCat(cutoffs_[i], ": ", counts[i], " vs. E=", e[i]));
+      LOG(INFO) << cutoffs_[i] << ": " << counts[i] << " vs. E=" << e[i];
     }
 
-    ABSL_INTERNAL_LOG(
-        INFO,
-        absl::StrCat(kChiSquared, "(data, dof=", dof, ") = ", chi_square, " (",
-                     p, ")\n", " vs.\n", kChiSquared, " @ 0.98 = ", threshold));
+    LOG(INFO) << kChiSquared << "(data, dof=" << dof << ") = " << chi_square
+              << " (" << p << ")\n"
+              << " vs.\n"
+              << kChiSquared << " @ 0.98 = " << threshold;
   }
   return p;
 }
diff --git a/absl/random/uniform_int_distribution_test.cc b/absl/random/uniform_int_distribution_test.cc
index a830117a..b40d6185 100644
--- a/absl/random/uniform_int_distribution_test.cc
+++ b/absl/random/uniform_int_distribution_test.cc
@@ -24,7 +24,7 @@
 
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
-#include "absl/base/internal/raw_logging.h"
+#include "absl/log/log.h"
 #include "absl/random/internal/chi_square.h"
 #include "absl/random/internal/distribution_test_util.h"
 #include "absl/random/internal/pcg_engine.h"
@@ -107,8 +107,7 @@ TYPED_TEST(UniformIntDistributionTest, ParamSerializeTest) {
         sample_min = sample;
       }
     }
-    std::string msg = absl::StrCat("Range: ", +sample_min, ", ", +sample_max);
-    ABSL_RAW_LOG(INFO, "%s", msg.c_str());
+    LOG(INFO) << "Range: " << sample_min << ", " << sample_max;
   }
 }
 
@@ -210,7 +209,7 @@ TYPED_TEST(UniformIntDistributionTest, ChiSquaredTest50) {
     absl::StrAppend(&msg, kChiSquared, " p-value ", p_value, "\n");
     absl::StrAppend(&msg, "High ", kChiSquared, " value: ", chi_square, " > ",
                     kThreshold);
-    ABSL_RAW_LOG(INFO, "%s", msg.c_str());
+    LOG(INFO) << msg;
     FAIL() << msg;
   }
 }
diff --git a/absl/random/uniform_real_distribution_test.cc b/absl/random/uniform_real_distribution_test.cc
index 07f199d3..260aac96 100644
--- a/absl/random/uniform_real_distribution_test.cc
+++ b/absl/random/uniform_real_distribution_test.cc
@@ -26,7 +26,7 @@
 
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
-#include "absl/base/internal/raw_logging.h"
+#include "absl/log/log.h"
 #include "absl/numeric/internal/representation.h"
 #include "absl/random/internal/chi_square.h"
 #include "absl/random/internal/distribution_test_util.h"
@@ -182,9 +182,8 @@ TYPED_TEST(UniformRealDistributionTest, ParamSerializeTest) {
 
     if (!std::is_same<real_type, long double>::value) {
       // static_cast<double>(long double) can overflow.
-      std::string msg = absl::StrCat("Range: ", static_cast<double>(sample_min),
-                                     ", ", static_cast<double>(sample_max));
-      ABSL_RAW_LOG(INFO, "%s", msg.c_str());
+      LOG(INFO) << "Range: " << static_cast<double>(sample_min) << ", "
+                << static_cast<double>(sample_max);
     }
   }
 }
@@ -324,7 +323,7 @@ TYPED_TEST(UniformRealDistributionTest, ChiSquaredTest50) {
       absl::StrAppend(&msg, kChiSquared, " p-value ", p_value, "\n");
       absl::StrAppend(&msg, "High ", kChiSquared, " value: ", chi_square, " > ",
                       kThreshold);
-      ABSL_RAW_LOG(INFO, "%s", msg.c_str());
+      LOG(INFO) << msg;
       FAIL() << msg;
     }
   }
diff --git a/absl/random/zipf_distribution_test.cc b/absl/random/zipf_distribution_test.cc
index c8bb89db..801ec4f6 100644
--- a/absl/random/zipf_distribution_test.cc
+++ b/absl/random/zipf_distribution_test.cc
@@ -25,7 +25,7 @@
 
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
-#include "absl/base/internal/raw_logging.h"
+#include "absl/log/log.h"
 #include "absl/random/internal/chi_square.h"
 #include "absl/random/internal/pcg_engine.h"
 #include "absl/random/internal/sequence_urbg.h"
@@ -102,8 +102,7 @@ TYPED_TEST(ZipfDistributionTypedTest, SerializeTest) {
       if (sample > sample_max) sample_max = sample;
       if (sample < sample_min) sample_min = sample;
     }
-    ABSL_INTERNAL_LOG(INFO,
-                      absl::StrCat("Range: ", +sample_min, ", ", +sample_max));
+    LOG(INFO) << "Range: " << sample_min << ", " << sample_max;
   }
 }
 
@@ -303,18 +302,15 @@ TEST_P(ZipfTest, ChiSquaredTest) {
 
   // Log if the chi_squared value is above the threshold.
   if (chi_square > threshold) {
-    ABSL_INTERNAL_LOG(INFO, "values");
+    LOG(INFO) << "values";
     for (size_t i = 0; i < expected.size(); i++) {
-      ABSL_INTERNAL_LOG(INFO, absl::StrCat(points[i], ": ", buckets[i],
-                                           " vs. E=", expected[i]));
+      LOG(INFO) << points[i] << ": " << buckets[i] << " vs. E=" << expected[i];
     }
-    ABSL_INTERNAL_LOG(INFO, absl::StrCat("trials ", trials));
-    ABSL_INTERNAL_LOG(INFO,
-                      absl::StrCat("mean ", avg, " vs. expected ", mean()));
-    ABSL_INTERNAL_LOG(INFO, absl::StrCat(kChiSquared, "(data, ", dof, ") = ",
-                                         chi_square, " (", p_actual, ")"));
-    ABSL_INTERNAL_LOG(INFO,
-                      absl::StrCat(kChiSquared, " @ 0.9995 = ", threshold));
+    LOG(INFO) << "trials " << trials;
+    LOG(INFO) << "mean " << avg << " vs. expected " << mean();
+    LOG(INFO) << kChiSquared << "(data, " << dof << ") = " << chi_square << " ("
+              << p_actual << ")";
+    LOG(INFO) << kChiSquared << " @ 0.9995 = " << threshold;
     FAIL() << kChiSquared << " value of " << chi_square
            << " is above the threshold.";
   }
diff --git a/absl/status/CMakeLists.txt b/absl/status/CMakeLists.txt
index 15db36af..4a3c5d68 100644
--- a/absl/status/CMakeLists.txt
+++ b/absl/status/CMakeLists.txt
@@ -25,6 +25,8 @@ absl_cc_library(
     "status_payload_printer.cc"
   COPTS
     ${ABSL_DEFAULT_COPTS}
+  DEFINES
+    "$<$<PLATFORM_ID:AIX>:_LINUX_SOURCE_COMPAT>"
   DEPS
     absl::atomic_hook
     absl::config
diff --git a/absl/status/internal/status_internal.h b/absl/status/internal/status_internal.h
index 873eb5c2..6198e726 100644
--- a/absl/status/internal/status_internal.h
+++ b/absl/status/internal/status_internal.h
@@ -66,6 +66,10 @@ struct StatusRep {
 
   std::atomic<int32_t> ref;
   absl::StatusCode code;
+
+  // As an internal implementation detail, we guarantee that if status.message()
+  // is non-empty, then the resulting string_view is null terminated.
+  // This is required to implement 'StatusMessageAsCStr(...)'
   std::string message;
   std::unique_ptr<status_internal::Payloads> payloads;
 };
diff --git a/absl/status/internal/statusor_internal.h b/absl/status/internal/statusor_internal.h
index eaac2c0b..49cead7a 100644
--- a/absl/status/internal/statusor_internal.h
+++ b/absl/status/internal/statusor_internal.h
@@ -69,11 +69,8 @@ using IsConstructibleOrConvertibleOrAssignableFromStatusOr =
 template <typename T, typename U>
 struct IsDirectInitializationAmbiguous
     : public absl::conditional_t<
-          std::is_same<absl::remove_cv_t<absl::remove_reference_t<U>>,
-                       U>::value,
-          std::false_type,
-          IsDirectInitializationAmbiguous<
-              T, absl::remove_cv_t<absl::remove_reference_t<U>>>> {};
+          std::is_same<absl::remove_cvref_t<U>, U>::value, std::false_type,
+          IsDirectInitializationAmbiguous<T, absl::remove_cvref_t<U>>> {};
 
 template <typename T, typename V>
 struct IsDirectInitializationAmbiguous<T, absl::StatusOr<V>>
@@ -84,14 +81,11 @@ struct IsDirectInitializationAmbiguous<T, absl::StatusOr<V>>
 template <typename T, typename U>
 using IsDirectInitializationValid = absl::disjunction<
     // Short circuits if T is basically U.
-    std::is_same<T, absl::remove_cv_t<absl::remove_reference_t<U>>>,
+    std::is_same<T, absl::remove_cvref_t<U>>,
     absl::negation<absl::disjunction<
-        std::is_same<absl::StatusOr<T>,
-                     absl::remove_cv_t<absl::remove_reference_t<U>>>,
-        std::is_same<absl::Status,
-                     absl::remove_cv_t<absl::remove_reference_t<U>>>,
-        std::is_same<absl::in_place_t,
-                     absl::remove_cv_t<absl::remove_reference_t<U>>>,
+        std::is_same<absl::StatusOr<T>, absl::remove_cvref_t<U>>,
+        std::is_same<absl::Status, absl::remove_cvref_t<U>>,
+        std::is_same<absl::in_place_t, absl::remove_cvref_t<U>>,
         IsDirectInitializationAmbiguous<T, U>>>>;
 
 // This trait detects whether `StatusOr<T>::operator=(U&&)` is ambiguous, which
@@ -107,11 +101,8 @@ using IsDirectInitializationValid = absl::disjunction<
 template <typename T, typename U>
 struct IsForwardingAssignmentAmbiguous
     : public absl::conditional_t<
-          std::is_same<absl::remove_cv_t<absl::remove_reference_t<U>>,
-                       U>::value,
-          std::false_type,
-          IsForwardingAssignmentAmbiguous<
-              T, absl::remove_cv_t<absl::remove_reference_t<U>>>> {};
+          std::is_same<absl::remove_cvref_t<U>, U>::value, std::false_type,
+          IsForwardingAssignmentAmbiguous<T, absl::remove_cvref_t<U>>> {};
 
 template <typename T, typename U>
 struct IsForwardingAssignmentAmbiguous<T, absl::StatusOr<U>>
@@ -122,14 +113,11 @@ struct IsForwardingAssignmentAmbiguous<T, absl::StatusOr<U>>
 template <typename T, typename U>
 using IsForwardingAssignmentValid = absl::disjunction<
     // Short circuits if T is basically U.
-    std::is_same<T, absl::remove_cv_t<absl::remove_reference_t<U>>>,
+    std::is_same<T, absl::remove_cvref_t<U>>,
     absl::negation<absl::disjunction<
-        std::is_same<absl::StatusOr<T>,
-                     absl::remove_cv_t<absl::remove_reference_t<U>>>,
-        std::is_same<absl::Status,
-                     absl::remove_cv_t<absl::remove_reference_t<U>>>,
-        std::is_same<absl::in_place_t,
-                     absl::remove_cv_t<absl::remove_reference_t<U>>>,
+        std::is_same<absl::StatusOr<T>, absl::remove_cvref_t<U>>,
+        std::is_same<absl::Status, absl::remove_cvref_t<U>>,
+        std::is_same<absl::in_place_t, absl::remove_cvref_t<U>>,
         IsForwardingAssignmentAmbiguous<T, U>>>>;
 
 class Helper {
diff --git a/absl/status/status.cc b/absl/status/status.cc
index 160eb417..26e68294 100644
--- a/absl/status/status.cc
+++ b/absl/status/status.cc
@@ -80,10 +80,8 @@ std::ostream& operator<<(std::ostream& os, StatusCode code) {
 namespace status_internal {
 
 static absl::optional<size_t> FindPayloadIndexByUrl(
-    const Payloads* payloads,
-    absl::string_view type_url) {
-  if (payloads == nullptr)
-    return absl::nullopt;
+    const Payloads* payloads, absl::string_view type_url) {
+  if (payloads == nullptr) return absl::nullopt;
 
   for (size_t i = 0; i < payloads->size(); ++i) {
     if ((*payloads)[i].type_url == type_url) return i;
@@ -125,8 +123,7 @@ absl::optional<absl::Cord> Status::GetPayload(
   const auto* payloads = GetPayloads();
   absl::optional<size_t> index =
       status_internal::FindPayloadIndexByUrl(payloads, type_url);
-  if (index.has_value())
-    return (*payloads)[index.value()].payload;
+  if (index.has_value()) return (*payloads)[index.value()].payload;
 
   return absl::nullopt;
 }
@@ -303,7 +300,7 @@ std::string Status::ToStringSlow(StatusToStringMode mode) const {
   absl::StrAppend(&text, absl::StatusCodeToString(code()), ": ", message());
 
   const bool with_payload = (mode & StatusToStringMode::kWithPayload) ==
-                      StatusToStringMode::kWithPayload;
+                            StatusToStringMode::kWithPayload;
 
   if (with_payload) {
     status_internal::StatusPayloadPrinter printer =
@@ -619,5 +616,12 @@ std::string* MakeCheckFailString(const absl::Status* status,
 
 }  // namespace status_internal
 
+const char* StatusMessageAsCStr(const Status& status) {
+  // As an internal implementation detail, we guarantee that if status.message()
+  // is non-empty, then the resulting string_view is null terminated.
+  auto sv_message = status.message();
+  return sv_message.empty() ? "" : sv_message.data();
+}
+
 ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/status/status.h b/absl/status/status.h
index 4e8292fc..595064c0 100644
--- a/absl/status/status.h
+++ b/absl/status/status.h
@@ -398,7 +398,7 @@ inline StatusToStringMode& operator^=(StatusToStringMode& lhs,
 //
 //   * It may provide more fine-grained semantic information about the error to
 //     facilitate actionable remedies.
-//   * It may provide human-readable contexual information that is more
+//   * It may provide human-readable contextual information that is more
 //     appropriate to display to an end user.
 //
 // Example:
@@ -538,7 +538,7 @@ class Status final {
   //
   //   * It may provide more fine-grained semantic information about the error
   //     to facilitate actionable remedies.
-  //   * It may provide human-readable contexual information that is more
+  //   * It may provide human-readable contextual information that is more
   //     appropriate to display to an end user.
   //
   // A payload consists of a [key,value] pair, where the key is a string
@@ -886,6 +886,15 @@ inline Status OkStatus() { return Status(); }
 // message-less kCancelled errors are common in the infrastructure.
 inline Status CancelledError() { return Status(absl::StatusCode::kCancelled); }
 
+// Retrieves a message's status as a null terminated C string. The lifetime of
+// this string is tied to the lifetime of the status object itself.
+//
+// If the status's message is empty, the empty string is returned.
+//
+// StatusMessageAsCStr exists for C support. Use `status.message()` in C++.
+const char* StatusMessageAsCStr(
+    const Status& status ABSL_ATTRIBUTE_LIFETIME_BOUND);
+
 ABSL_NAMESPACE_END
 }  // namespace absl
 
diff --git a/absl/status/status_test.cc b/absl/status/status_test.cc
index 74a64ace..898a9cb2 100644
--- a/absl/status/status_test.cc
+++ b/absl/status/status_test.cc
@@ -132,6 +132,29 @@ TEST(Status, ConstructorWithCodeMessage) {
   }
 }
 
+TEST(Status, StatusMessageCStringTest) {
+  {
+    absl::Status status = absl::OkStatus();
+    EXPECT_EQ(status.message(), "");
+    EXPECT_STREQ(absl::StatusMessageAsCStr(status), "");
+    EXPECT_EQ(status.message(), absl::StatusMessageAsCStr(status));
+    EXPECT_NE(absl::StatusMessageAsCStr(status), nullptr);
+  }
+  {
+    absl::Status status;
+    EXPECT_EQ(status.message(), "");
+    EXPECT_NE(absl::StatusMessageAsCStr(status), nullptr);
+    EXPECT_STREQ(absl::StatusMessageAsCStr(status), "");
+  }
+  {
+    absl::Status status(absl::StatusCode::kInternal, "message");
+    EXPECT_FALSE(status.ok());
+    EXPECT_EQ(absl::StatusCode::kInternal, status.code());
+    EXPECT_EQ("message", status.message());
+    EXPECT_STREQ("message", absl::StatusMessageAsCStr(status));
+  }
+}
+
 TEST(Status, ConstructOutOfRangeCode) {
   const int kRawCode = 9999;
   absl::Status status(static_cast<absl::StatusCode>(kRawCode), "");
diff --git a/absl/status/statusor.h b/absl/status/statusor.h
index a76e7201..54c7ce02 100644
--- a/absl/status/statusor.h
+++ b/absl/status/statusor.h
@@ -146,7 +146,7 @@ class ABSL_MUST_USE_RESULT StatusOr;
 //
 //   absl::StatusOr<int> i = GetCount();
 //   if (i.ok()) {
-//     updated_total += *i
+//     updated_total += *i;
 //   }
 //
 // NOTE: using `absl::StatusOr<T>::value()` when no valid value is present will
@@ -411,7 +411,7 @@ class StatusOr : private internal_statusor::StatusOrData<T>,
       typename = typename std::enable_if<absl::conjunction<
           std::is_constructible<T, U&&>, std::is_assignable<T&, U&&>,
           absl::disjunction<
-              std::is_same<absl::remove_cv_t<absl::remove_reference_t<U>>, T>,
+              std::is_same<absl::remove_cvref_t<U>, T>,
               absl::conjunction<
                   absl::negation<std::is_convertible<U&&, absl::Status>>,
                   absl::negation<internal_statusor::
@@ -444,8 +444,7 @@ class StatusOr : private internal_statusor::StatusOrData<T>,
               internal_statusor::IsDirectInitializationValid<T, U&&>,
               std::is_constructible<T, U&&>, std::is_convertible<U&&, T>,
               absl::disjunction<
-                  std::is_same<absl::remove_cv_t<absl::remove_reference_t<U>>,
-                               T>,
+                  std::is_same<absl::remove_cvref_t<U>, T>,
                   absl::conjunction<
                       absl::negation<std::is_convertible<U&&, absl::Status>>,
                       absl::negation<
@@ -461,8 +460,7 @@ class StatusOr : private internal_statusor::StatusOrData<T>,
           absl::conjunction<
               internal_statusor::IsDirectInitializationValid<T, U&&>,
               absl::disjunction<
-                  std::is_same<absl::remove_cv_t<absl::remove_reference_t<U>>,
-                               T>,
+                  std::is_same<absl::remove_cvref_t<U>, T>,
                   absl::conjunction<
                       absl::negation<std::is_constructible<absl::Status, U&&>>,
                       absl::negation<
@@ -584,7 +582,7 @@ class StatusOr : private internal_statusor::StatusOrData<T>,
   // Reconstructs the inner value T in-place using the provided args, using the
   // T(args...) constructor. Returns reference to the reconstructed `T`.
   template <typename... Args>
-  T& emplace(Args&&... args) {
+  T& emplace(Args&&... args) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     if (ok()) {
       this->Clear();
       this->MakeValue(std::forward<Args>(args)...);
@@ -600,7 +598,8 @@ class StatusOr : private internal_statusor::StatusOrData<T>,
       absl::enable_if_t<
           std::is_constructible<T, std::initializer_list<U>&, Args&&...>::value,
           int> = 0>
-  T& emplace(std::initializer_list<U> ilist, Args&&... args) {
+  T& emplace(std::initializer_list<U> ilist,
+             Args&&... args) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     if (ok()) {
       this->Clear();
       this->MakeValue(ilist, std::forward<Args>(args)...);
@@ -611,6 +610,21 @@ class StatusOr : private internal_statusor::StatusOrData<T>,
     return this->data_;
   }
 
+  // StatusOr<T>::AssignStatus()
+  //
+  // Sets the status of `absl::StatusOr<T>` to the given non-ok status value.
+  //
+  // NOTE: We recommend using the constructor and `operator=` where possible.
+  // This method is intended for use in generic programming, to enable setting
+  // the status of a `StatusOr<T>` when `T` may be `Status`. In that case, the
+  // constructor and `operator=` would assign into the inner value of type
+  // `Status`, rather than status of the `StatusOr` (b/280392796).
+  //
+  // REQUIRES: !Status(std::forward<U>(v)).ok(). This requirement is DCHECKed.
+  // In optimized builds, passing absl::OkStatus() here will have the effect
+  // of passing absl::StatusCode::kInternal as a fallback.
+  using internal_statusor::StatusOrData<T>::AssignStatus;
+
  private:
   using internal_statusor::StatusOrData<T>::Assign;
   template <typename U>
diff --git a/absl/status/statusor_test.cc b/absl/status/statusor_test.cc
index 29021543..e65f5d27 100644
--- a/absl/status/statusor_test.cc
+++ b/absl/status/statusor_test.cc
@@ -1844,4 +1844,37 @@ TEST(StatusOr, AssignmentFromTypeConvertibleToStatus) {
   }
 }
 
+TEST(StatusOr, StatusAssignmentFromStatusError) {
+  absl::StatusOr<absl::Status> statusor;
+  statusor.AssignStatus(absl::CancelledError());
+
+  EXPECT_FALSE(statusor.ok());
+  EXPECT_EQ(statusor.status(), absl::CancelledError());
+}
+
+#if GTEST_HAS_DEATH_TEST
+TEST(StatusOr, StatusAssignmentFromStatusOk) {
+  EXPECT_DEBUG_DEATH(
+      {
+        absl::StatusOr<absl::Status> statusor;
+        // This will DCHECK.
+        statusor.AssignStatus(absl::OkStatus());
+        // In optimized mode, we are actually going to get error::INTERNAL for
+        // status here, rather than crashing, so check that.
+        EXPECT_FALSE(statusor.ok());
+        EXPECT_EQ(statusor.status().code(), absl::StatusCode::kInternal);
+      },
+      "An OK status is not a valid constructor argument to StatusOr<T>");
+}
+#endif
+
+TEST(StatusOr, StatusAssignmentFromTypeConvertibleToStatus) {
+  CustomType<MyType, kConvToStatus> v;
+  absl::StatusOr<MyType> statusor;
+  statusor.AssignStatus(v);
+
+  EXPECT_FALSE(statusor.ok());
+  EXPECT_EQ(statusor.status(), static_cast<absl::Status>(v));
+}
+
 }  // namespace
diff --git a/absl/strings/BUILD.bazel b/absl/strings/BUILD.bazel
index 53c57718..819bbe69 100644
--- a/absl/strings/BUILD.bazel
+++ b/absl/strings/BUILD.bazel
@@ -28,6 +28,20 @@ package(
 licenses(["notice"])
 
 cc_library(
+    name = "string_view",
+    srcs = ["string_view.cc"],
+    hdrs = ["string_view.h"],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        "//absl/base",
+        "//absl/base:config",
+        "//absl/base:core_headers",
+        "//absl/base:throw_delegate",
+    ],
+)
+
+cc_library(
     name = "strings",
     srcs = [
         "ascii.cc",
@@ -50,7 +64,6 @@ cc_library(
         "str_cat.cc",
         "str_replace.cc",
         "str_split.cc",
-        "string_view.cc",
         "substitute.cc",
     ],
     hdrs = [
@@ -72,8 +85,15 @@ cc_library(
     ],
     copts = ABSL_DEFAULT_COPTS,
     linkopts = ABSL_DEFAULT_LINKOPTS,
+    textual_hdrs = [
+        # string_view.h was once part of :strings, so string_view.h is
+        # re-exported for backwards compatibility.
+        # New code should directly depend on :string_view.
+        "string_view.h",
+    ],
     deps = [
         ":internal",
+        ":string_view",
         "//absl/base",
         "//absl/base:config",
         "//absl/base:core_headers",
@@ -263,6 +283,7 @@ cc_test(
     tags = ["benchmark"],
     visibility = ["//visibility:private"],
     deps = [
+        ":string_view",
         ":strings",
         "//absl/base:core_headers",
         "//absl/base:raw_logging_internal",
@@ -277,7 +298,7 @@ cc_test(
     copts = ABSL_TEST_COPTS,
     visibility = ["//visibility:private"],
     deps = [
-        ":strings",
+        ":string_view",
         "//absl/base:config",
         "//absl/base:core_headers",
         "//absl/base:dynamic_annotations",
@@ -350,6 +371,7 @@ cc_test(
 cc_test(
     name = "cord_rep_btree_test",
     size = "medium",
+    timeout = "long",
     srcs = ["internal/cord_rep_btree_test.cc"],
     copts = ABSL_TEST_COPTS,
     visibility = ["//visibility:private"],
@@ -457,7 +479,6 @@ cc_library(
         ":cordz_update_scope",
         ":cordz_update_tracker",
         ":internal",
-        ":str_format",
         ":strings",
         "//absl/base",
         "//absl/base:config",
@@ -514,6 +535,7 @@ cc_library(
         "//absl/container:inlined_vector",
         "//absl/debugging:stacktrace",
         "//absl/synchronization",
+        "//absl/time",
         "//absl/types:span",
     ],
 )
@@ -773,10 +795,10 @@ cc_test(
         "//absl/base:config",
         "//absl/base:core_headers",
         "//absl/base:endian",
-        "//absl/base:raw_logging_internal",
         "//absl/container:fixed_array",
         "//absl/hash",
         "//absl/log",
+        "//absl/log:check",
         "//absl/random",
         "@com_google_googletest//:gtest_main",
     ],
@@ -1018,7 +1040,7 @@ cc_test(
         ":pow10_helper",
         ":strings",
         "//absl/base:config",
-        "//absl/base:raw_logging_internal",
+        "//absl/log",
         "//absl/random",
         "//absl/random:distributions",
         "@com_google_googletest//:gtest_main",
@@ -1095,7 +1117,7 @@ cc_test(
     deps = [
         ":strings",
         "//absl/base:config",
-        "//absl/base:raw_logging_internal",
+        "//absl/log:check",
         "@com_google_googletest//:gtest_main",
     ],
 )
@@ -1168,6 +1190,7 @@ cc_library(
         ":strings",
         "//absl/base:config",
         "//absl/base:core_headers",
+        "//absl/container:inlined_vector",
         "//absl/functional:function_ref",
         "//absl/meta:type_traits",
         "//absl/numeric:bits",
@@ -1252,6 +1275,7 @@ cc_test(
         ":strings",
         "//absl/base:core_headers",
         "//absl/base:raw_logging_internal",
+        "//absl/log",
         "//absl/types:optional",
         "@com_google_googletest//:gtest_main",
     ],
@@ -1317,3 +1341,15 @@ cc_binary(
         "//absl/types:optional",
     ],
 )
+
+cc_test(
+    name = "char_formatting_test",
+    srcs = [
+        "char_formatting_test.cc",
+    ],
+    deps = [
+        ":str_format",
+        ":strings",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
diff --git a/absl/strings/CMakeLists.txt b/absl/strings/CMakeLists.txt
index a0f7cc54..1959dc91 100644
--- a/absl/strings/CMakeLists.txt
+++ b/absl/strings/CMakeLists.txt
@@ -16,6 +16,23 @@
 
 absl_cc_library(
   NAME
+    string_view
+  HDRS
+    string_view.h
+  SRCS
+    string_view.cc
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  DEPS
+    absl::base
+    absl::config
+    absl::core_headers
+    absl::throw_delegate
+  PUBLIC
+)
+
+absl_cc_library(
+  NAME
     strings
   HDRS
     "ascii.h"
@@ -30,7 +47,6 @@ absl_cc_library(
     "str_join.h"
     "str_replace.h"
     "str_split.h"
-    "string_view.h"
     "strip.h"
     "substitute.h"
   SRCS
@@ -54,11 +70,11 @@ absl_cc_library(
     "str_cat.cc"
     "str_replace.cc"
     "str_split.cc"
-    "string_view.cc"
     "substitute.cc"
   COPTS
     ${ABSL_DEFAULT_COPTS}
   DEPS
+    absl::string_view
     absl::strings_internal
     absl::base
     absl::bits
@@ -317,7 +333,7 @@ absl_cc_test(
     absl::core_headers
     absl::pow10_helper
     absl::config
-    absl::raw_logging_internal
+    absl::log
     absl::random_random
     absl::random_distributions
     absl::strings_internal
@@ -372,9 +388,9 @@ absl_cc_test(
   COPTS
     ${ABSL_TEST_COPTS}
   DEPS
-    absl::strings
+    absl::check
     absl::config
-    absl::raw_logging_internal
+    absl::strings
     GTest::gmock_main
 )
 
@@ -432,6 +448,7 @@ absl_cc_library(
     absl::strings
     absl::config
     absl::core_headers
+    absl::inlined_vector
     absl::numeric_representation
     absl::type_traits
     absl::utility
@@ -516,6 +533,7 @@ absl_cc_test(
     absl::strings
     absl::str_format_internal
     absl::core_headers
+    absl::log
     absl::raw_logging_internal
     absl::int128
     GTest::gmock_main
@@ -547,6 +565,20 @@ absl_cc_test(
     GTest::gmock_main
 )
 
+absl_cc_test(
+  NAME
+    char_formatting_test
+  SRCS
+    "char_formatting_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  DEPS
+    absl::base
+    absl::str_format
+    absl::strings
+    GTest::gmock_main
+)
+
 # Internal-only target, do not depend on directly.
 absl_cc_library(
   NAME
@@ -745,6 +777,7 @@ absl_cc_library(
     absl::raw_logging_internal
     absl::stacktrace
     absl::synchronization
+    absl::time
 )
 
 absl_cc_test(
@@ -959,19 +992,20 @@ absl_cc_test(
   COPTS
     ${ABSL_TEST_COPTS}
   DEPS
-    absl::cord
-    absl::str_format
-    absl::strings
     absl::base
+    absl::check
     absl::config
+    absl::cord
     absl::cord_test_helpers
     absl::cordz_test_helpers
     absl::core_headers
     absl::endian
+    absl::fixed_array
     absl::hash
+    absl::log
     absl::random_random
-    absl::raw_logging_internal
-    absl::fixed_array
+    absl::str_format
+    absl::strings
     GTest::gmock_main
 )
 
diff --git a/absl/strings/ascii.cc b/absl/strings/ascii.cc
index 868df2d1..16c96899 100644
--- a/absl/strings/ascii.cc
+++ b/absl/strings/ascii.cc
@@ -14,6 +14,10 @@
 
 #include "absl/strings/ascii.h"
 
+#include <climits>
+#include <cstring>
+#include <string>
+
 namespace absl {
 ABSL_NAMESPACE_BEGIN
 namespace ascii_internal {
@@ -153,18 +157,62 @@ ABSL_DLL const char kToUpper[256] = {
 };
 // clang-format on
 
+template <bool ToUpper>
+constexpr void AsciiStrCaseFold(char* p, char* end) {
+  // The upper- and lowercase versions of ASCII characters differ by only 1 bit.
+  // When we need to flip the case, we can xor with this bit to achieve the
+  // desired result. Note that the choice of 'a' and 'A' here is arbitrary. We
+  // could have chosen 'z' and 'Z', or any other pair of characters as they all
+  // have the same single bit difference.
+  constexpr unsigned char kAsciiCaseBitFlip = 'a' ^ 'A';
+
+  constexpr char ch_a = ToUpper ? 'a' : 'A';
+  constexpr char ch_z = ToUpper ? 'z' : 'Z';
+  for (; p < end; ++p) {
+    unsigned char v = static_cast<unsigned char>(*p);
+    // We use & instead of && to ensure this always stays branchless
+    // We use static_cast<int> to suppress -Wbitwise-instead-of-logical
+    bool is_in_range = static_cast<bool>(static_cast<int>(ch_a <= v) &
+                                         static_cast<int>(v <= ch_z));
+    v ^= is_in_range ? kAsciiCaseBitFlip : 0;
+    *p = static_cast<char>(v);
+  }
+}
+
+static constexpr size_t ValidateAsciiCasefold() {
+  constexpr size_t num_chars = 1 + CHAR_MAX - CHAR_MIN;
+  size_t incorrect_index = 0;
+  char lowered[num_chars] = {};
+  char uppered[num_chars] = {};
+  for (unsigned int i = 0; i < num_chars; ++i) {
+    uppered[i] = lowered[i] = static_cast<char>(i);
+  }
+  AsciiStrCaseFold<false>(&lowered[0], &lowered[num_chars]);
+  AsciiStrCaseFold<true>(&uppered[0], &uppered[num_chars]);
+  for (size_t i = 0; i < num_chars; ++i) {
+    const char ch = static_cast<char>(i),
+               ch_upper = ('a' <= ch && ch <= 'z' ? 'A' + (ch - 'a') : ch),
+               ch_lower = ('A' <= ch && ch <= 'Z' ? 'a' + (ch - 'A') : ch);
+    if (uppered[i] != ch_upper || lowered[i] != ch_lower) {
+      incorrect_index = i > 0 ? i : num_chars;
+      break;
+    }
+  }
+  return incorrect_index;
+}
+
+static_assert(ValidateAsciiCasefold() == 0, "error in case conversion");
+
 }  // namespace ascii_internal
 
 void AsciiStrToLower(std::string* s) {
-  for (auto& ch : *s) {
-    ch = absl::ascii_tolower(static_cast<unsigned char>(ch));
-  }
+  char* p = &(*s)[0];  // Guaranteed to be valid for empty strings
+  return ascii_internal::AsciiStrCaseFold<false>(p, p + s->size());
 }
 
 void AsciiStrToUpper(std::string* s) {
-  for (auto& ch : *s) {
-    ch = absl::ascii_toupper(static_cast<unsigned char>(ch));
-  }
+  char* p = &(*s)[0];  // Guaranteed to be valid for empty strings
+  return ascii_internal::AsciiStrCaseFold<true>(p, p + s->size());
 }
 
 void RemoveExtraAsciiWhitespace(std::string* str) {
diff --git a/absl/strings/ascii_test.cc b/absl/strings/ascii_test.cc
index dfed114c..4ea262f1 100644
--- a/absl/strings/ascii_test.cc
+++ b/absl/strings/ascii_test.cc
@@ -14,6 +14,7 @@
 
 #include "absl/strings/ascii.h"
 
+#include <algorithm>
 #include <cctype>
 #include <clocale>
 #include <cstring>
@@ -189,14 +190,14 @@ TEST(AsciiStrTo, Lower) {
   const std::string str("GHIJKL");
   const std::string str2("MNOPQR");
   const absl::string_view sp(str2);
-  std::string mutable_str("STUVWX");
+  std::string mutable_str("_`?@[{AMNOPQRSTUVWXYZ");
 
   EXPECT_EQ("abcdef", absl::AsciiStrToLower(buf));
   EXPECT_EQ("ghijkl", absl::AsciiStrToLower(str));
   EXPECT_EQ("mnopqr", absl::AsciiStrToLower(sp));
 
   absl::AsciiStrToLower(&mutable_str);
-  EXPECT_EQ("stuvwx", mutable_str);
+  EXPECT_EQ("_`?@[{amnopqrstuvwxyz", mutable_str);
 
   char mutable_buf[] = "Mutable";
   std::transform(mutable_buf, mutable_buf + strlen(mutable_buf),
@@ -207,12 +208,12 @@ TEST(AsciiStrTo, Lower) {
 TEST(AsciiStrTo, Upper) {
   const char buf[] = "abcdef";
   const std::string str("ghijkl");
-  const std::string str2("mnopqr");
+  const std::string str2("_`?@[{amnopqrstuvwxyz");
   const absl::string_view sp(str2);
 
   EXPECT_EQ("ABCDEF", absl::AsciiStrToUpper(buf));
   EXPECT_EQ("GHIJKL", absl::AsciiStrToUpper(str));
-  EXPECT_EQ("MNOPQR", absl::AsciiStrToUpper(sp));
+  EXPECT_EQ("_`?@[{AMNOPQRSTUVWXYZ", absl::AsciiStrToUpper(sp));
 
   char mutable_buf[] = "Mutable";
   std::transform(mutable_buf, mutable_buf + strlen(mutable_buf),
diff --git a/absl/strings/char_formatting_test.cc b/absl/strings/char_formatting_test.cc
new file mode 100644
index 00000000..1692da70
--- /dev/null
+++ b/absl/strings/char_formatting_test.cc
@@ -0,0 +1,169 @@
+// Copyright 2023 The Abseil Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <cstddef>
+
+#include "gtest/gtest.h"
+#include "absl/strings/str_cat.h"
+#include "absl/strings/str_format.h"
+#include "absl/strings/substitute.h"
+
+namespace {
+
+TEST(CharFormatting, Char) {
+  const char v = 'A';
+
+  // Desired behavior: does not compile:
+  // EXPECT_EQ(absl::StrCat(v, "B"), "AB");
+  // EXPECT_EQ(absl::StrFormat("%vB", v), "AB");
+
+  // Legacy behavior: format as char:
+  EXPECT_EQ(absl::Substitute("$0B", v), "AB");
+}
+
+enum CharEnum : char {};
+TEST(CharFormatting, CharEnum) {
+  auto v = static_cast<CharEnum>('A');
+
+  // Desired behavior: format as decimal
+  EXPECT_EQ(absl::StrFormat("%vB", v), "65B");
+  EXPECT_EQ(absl::StrCat(v, "B"), "65B");
+
+  // Legacy behavior: format as character:
+
+  // Some older versions of gcc behave differently in this one case
+#if !defined(__GNUC__) || defined(__clang__)
+  EXPECT_EQ(absl::Substitute("$0B", v), "AB");
+#endif
+}
+
+enum class CharEnumClass: char {};
+TEST(CharFormatting, CharEnumClass) {
+  auto v = static_cast<CharEnumClass>('A');
+
+  // Desired behavior: format as decimal:
+  EXPECT_EQ(absl::StrFormat("%vB", v), "65B");
+  EXPECT_EQ(absl::StrCat(v, "B"), "65B");
+
+  // Legacy behavior: format as character:
+  EXPECT_EQ(absl::Substitute("$0B", v), "AB");
+}
+
+TEST(CharFormatting, UnsignedChar) {
+  const unsigned char v = 'A';
+
+  // Desired behavior: format as decimal:
+  EXPECT_EQ(absl::StrCat(v, "B"), "65B");
+  EXPECT_EQ(absl::Substitute("$0B", v), "65B");
+  EXPECT_EQ(absl::StrFormat("%vB", v), "65B");
+
+  // Signedness check
+  const unsigned char w = 255;
+  EXPECT_EQ(absl::StrCat(w, "B"), "255B");
+  EXPECT_EQ(absl::Substitute("$0B", w), "255B");
+  // EXPECT_EQ(absl::StrFormat("%vB", v), "255B");
+}
+
+TEST(CharFormatting, SignedChar) {
+  const signed char v = 'A';
+
+  // Desired behavior: format as decimal:
+  EXPECT_EQ(absl::StrCat(v, "B"), "65B");
+  EXPECT_EQ(absl::Substitute("$0B", v), "65B");
+  EXPECT_EQ(absl::StrFormat("%vB", v), "65B");
+
+  // Signedness check
+  const signed char w = -128;
+  EXPECT_EQ(absl::StrCat(w, "B"), "-128B");
+  EXPECT_EQ(absl::Substitute("$0B", w), "-128B");
+}
+
+enum UnsignedCharEnum : unsigned char {};
+TEST(CharFormatting, UnsignedCharEnum) {
+  auto v = static_cast<UnsignedCharEnum>('A');
+
+  // Desired behavior: format as decimal:
+  EXPECT_EQ(absl::StrCat(v, "B"), "65B");
+  EXPECT_EQ(absl::Substitute("$0B", v), "65B");
+  EXPECT_EQ(absl::StrFormat("%vB", v), "65B");
+
+  // Signedness check
+  auto w = static_cast<UnsignedCharEnum>(255);
+  EXPECT_EQ(absl::StrCat(w, "B"), "255B");
+  EXPECT_EQ(absl::Substitute("$0B", w), "255B");
+  EXPECT_EQ(absl::StrFormat("%vB", w), "255B");
+}
+
+enum SignedCharEnum : signed char {};
+TEST(CharFormatting, SignedCharEnum) {
+  auto v = static_cast<SignedCharEnum>('A');
+
+  // Desired behavior: format as decimal:
+  EXPECT_EQ(absl::StrCat(v, "B"), "65B");
+  EXPECT_EQ(absl::Substitute("$0B", v), "65B");
+  EXPECT_EQ(absl::StrFormat("%vB", v), "65B");
+
+  // Signedness check
+  auto w = static_cast<SignedCharEnum>(-128);
+  EXPECT_EQ(absl::StrCat(w, "B"), "-128B");
+  EXPECT_EQ(absl::Substitute("$0B", w), "-128B");
+  EXPECT_EQ(absl::StrFormat("%vB", w), "-128B");
+}
+
+enum class UnsignedCharEnumClass : unsigned char {};
+TEST(CharFormatting, UnsignedCharEnumClass) {
+  auto v = static_cast<UnsignedCharEnumClass>('A');
+
+  // Desired behavior: format as decimal:
+  EXPECT_EQ(absl::StrCat(v, "B"), "65B");
+  EXPECT_EQ(absl::Substitute("$0B", v), "65B");
+  EXPECT_EQ(absl::StrFormat("%vB", v), "65B");
+
+  // Signedness check
+  auto w = static_cast<UnsignedCharEnumClass>(255);
+  EXPECT_EQ(absl::StrCat(w, "B"), "255B");
+  EXPECT_EQ(absl::Substitute("$0B", w), "255B");
+  EXPECT_EQ(absl::StrFormat("%vB", w), "255B");
+}
+
+enum SignedCharEnumClass : signed char {};
+TEST(CharFormatting, SignedCharEnumClass) {
+  auto v = static_cast<SignedCharEnumClass>('A');
+
+  // Desired behavior: format as decimal:
+  EXPECT_EQ(absl::StrCat(v, "B"), "65B");
+  EXPECT_EQ(absl::Substitute("$0B", v), "65B");
+  EXPECT_EQ(absl::StrFormat("%vB", v), "65B");
+
+  // Signedness check
+  auto w = static_cast<SignedCharEnumClass>(-128);
+  EXPECT_EQ(absl::StrCat(w, "B"), "-128B");
+  EXPECT_EQ(absl::Substitute("$0B", w), "-128B");
+  EXPECT_EQ(absl::StrFormat("%vB", w), "-128B");
+}
+
+#ifdef __cpp_lib_byte
+TEST(CharFormatting, StdByte) {
+  auto v = static_cast<std::byte>('A');
+  // Desired behavior: format as 0xff
+  // (No APIs do this today.)
+
+  // Legacy behavior: format as decimal:
+  EXPECT_EQ(absl::StrCat(v, "B"), "65B");
+  EXPECT_EQ(absl::Substitute("$0B", v), "65B");
+  EXPECT_EQ(absl::StrFormat("%vB", v), "65B");
+}
+#endif  // _cpp_lib_byte
+
+}  // namespace
diff --git a/absl/strings/charconv.cc b/absl/strings/charconv.cc
index 69d420bc..778a1c75 100644
--- a/absl/strings/charconv.cc
+++ b/absl/strings/charconv.cc
@@ -21,6 +21,7 @@
 #include <limits>
 
 #include "absl/base/casts.h"
+#include "absl/base/config.h"
 #include "absl/numeric/bits.h"
 #include "absl/numeric/int128.h"
 #include "absl/strings/internal/charconv_bigint.h"
@@ -118,10 +119,17 @@ struct FloatTraits<double> {
   static constexpr int kEiselLemireMaxExclusiveExp10 = 309;
 
   static double MakeNan(const char* tagp) {
+#if ABSL_HAVE_BUILTIN(__builtin_nan)
+    // Use __builtin_nan() if available since it has a fix for
+    // https://bugs.llvm.org/show_bug.cgi?id=37778
+    // std::nan may use the glibc implementation.
+    return __builtin_nan(tagp);
+#else
     // Support nan no matter which namespace it's in.  Some platforms
     // incorrectly don't put it in namespace std.
     using namespace std;  // NOLINT
     return nan(tagp);
+#endif
   }
 
   // Builds a nonzero floating point number out of the provided parts.
@@ -184,10 +192,17 @@ struct FloatTraits<float> {
   static constexpr int kEiselLemireMaxExclusiveExp10 = 39;
 
   static float MakeNan(const char* tagp) {
+#if ABSL_HAVE_BUILTIN(__builtin_nanf)
+    // Use __builtin_nanf() if available since it has a fix for
+    // https://bugs.llvm.org/show_bug.cgi?id=37778
+    // std::nanf may use the glibc implementation.
+    return __builtin_nanf(tagp);
+#else
     // Support nanf no matter which namespace it's in.  Some platforms
     // incorrectly don't put it in namespace std.
     using namespace std;  // NOLINT
-    return nanf(tagp);
+    return std::nanf(tagp);
+#endif
   }
 
   static float Make(mantissa_t mantissa, int exponent, bool sign) {
@@ -203,7 +218,8 @@ struct FloatTraits<float> {
     if (mantissa > kMantissaMask) {
       // Normal value.
       // Adjust by 127 for the exponent representation bias, and an additional
-      // 23 due to the implied decimal point in the IEEE mantissa represenation.
+      // 23 due to the implied decimal point in the IEEE mantissa
+      // representation.
       flt += static_cast<uint32_t>(exponent + 127 + kTargetMantissaBits - 1)
              << 23;
       mantissa &= kMantissaMask;
@@ -349,7 +365,8 @@ bool HandleEdgeCase(const strings_internal::ParsedFloat& input, bool negative,
     // https://bugs.llvm.org/show_bug.cgi?id=37778
     // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86113
     constexpr ptrdiff_t kNanBufferSize = 128;
-#if defined(__GNUC__) || (defined(__clang__) && __clang_major__ < 7)
+#if (defined(__GNUC__) && !defined(__clang__)) || \
+    (defined(__clang__) && __clang_major__ < 7)
     volatile char n_char_sequence[kNanBufferSize];
 #else
     char n_char_sequence[kNanBufferSize];
@@ -462,7 +479,7 @@ uint64_t ShiftRightAndRound(uint128 value, int shift, bool input_exact,
     // the low bit of `value` is set.
     //
     // In inexact mode, the nonzero error means the actual value is greater
-    // than the halfway point and we must alway round up.
+    // than the halfway point and we must always round up.
     if ((value & 1) == 1 || !input_exact) {
       ++value;
     }
diff --git a/absl/strings/charconv.h b/absl/strings/charconv.h
index 7c509812..111c7120 100644
--- a/absl/strings/charconv.h
+++ b/absl/strings/charconv.h
@@ -22,7 +22,7 @@
 namespace absl {
 ABSL_NAMESPACE_BEGIN
 
-// Workalike compatibilty version of std::chars_format from C++17.
+// Workalike compatibility version of std::chars_format from C++17.
 //
 // This is an bitfield enumerator which can be passed to absl::from_chars to
 // configure the string-to-float conversion.
@@ -48,7 +48,7 @@ struct from_chars_result {
   std::errc ec;
 };
 
-// Workalike compatibilty version of std::from_chars from C++17.  Currently
+// Workalike compatibility version of std::from_chars from C++17.  Currently
 // this only supports the `double` and `float` types.
 //
 // This interface incorporates the proposed resolutions for library issues
diff --git a/absl/strings/cord.cc b/absl/strings/cord.cc
index 1d33dd83..14976aef 100644
--- a/absl/strings/cord.cc
+++ b/absl/strings/cord.cc
@@ -48,7 +48,6 @@
 #include "absl/strings/internal/cordz_update_tracker.h"
 #include "absl/strings/internal/resize_uninitialized.h"
 #include "absl/strings/str_cat.h"
-#include "absl/strings/str_format.h"
 #include "absl/strings/str_join.h"
 #include "absl/strings/string_view.h"
 
@@ -795,7 +794,7 @@ int CompareChunks(absl::string_view* lhs, absl::string_view* rhs,
 }
 
 // This overload set computes comparison results from memcmp result. This
-// interface is used inside GenericCompare below. Differet implementations
+// interface is used inside GenericCompare below. Different implementations
 // are specialized for int and bool. For int we clamp result to {-1, 0, 1}
 // set. For bool we just interested in "value == 0".
 template <typename ResultType>
diff --git a/absl/strings/cord.h b/absl/strings/cord.h
index c4a0d5aa..457ccf06 100644
--- a/absl/strings/cord.h
+++ b/absl/strings/cord.h
@@ -110,9 +110,30 @@ enum class CordMemoryAccounting {
   // Counts the *approximate* number of bytes held in full or in part by this
   // Cord (which may not remain the same between invocations). Cords that share
   // memory could each be "charged" independently for the same shared memory.
+  // See also comment on `kTotalMorePrecise` on internally shared memory.
   kTotal,
 
   // Counts the *approximate* number of bytes held in full or in part by this
+  // Cord for the distinct memory held by this cord. This option is similar
+  // to `kTotal`, except that if the cord has multiple references to the same
+  // memory, that memory is only counted once.
+  //
+  // For example:
+  //   absl::Cord cord;
+  //   cord.append(some_other_cord);
+  //   cord.append(some_other_cord);
+  //   // Counts `some_other_cord` twice:
+  //   cord.EstimatedMemoryUsage(kTotal);
+  //   // Counts `some_other_cord` once:
+  //   cord.EstimatedMemoryUsage(kTotalMorePrecise);
+  //
+  // The `kTotalMorePrecise` number is more expensive to compute as it requires
+  // deduplicating all memory references. Applications should prefer to use
+  // `kFairShare` or `kTotal` unless they really need a more precise estimate
+  // on "how much memory is potentially held / kept alive by this cord?"
+  kTotalMorePrecise,
+
+  // Counts the *approximate* number of bytes held in full or in part by this
   // Cord weighted by the sharing ratio of that data. For example, if some data
   // edge is shared by 4 different Cords, then each cord is attributed 1/4th of
   // the total memory usage as a 'fair share' of the total memory usage.
@@ -661,7 +682,7 @@ class Cord {
   class CharRange {
    public:
     // Fulfill minimum c++ container requirements [container.requirements]
-    // Theses (partial) container type definitions allow CharRange to be used
+    // These (partial) container type definitions allow CharRange to be used
     // in various utilities expecting a subset of [container.requirements].
     // For example, the below enables using `::testing::ElementsAre(...)`
     using value_type = char;
@@ -1273,10 +1294,16 @@ inline size_t Cord::EstimatedMemoryUsage(
     CordMemoryAccounting accounting_method) const {
   size_t result = sizeof(Cord);
   if (const absl::cord_internal::CordRep* rep = contents_.tree()) {
-    if (accounting_method == CordMemoryAccounting::kFairShare) {
-      result += cord_internal::GetEstimatedFairShareMemoryUsage(rep);
-    } else {
-      result += cord_internal::GetEstimatedMemoryUsage(rep);
+    switch (accounting_method) {
+      case CordMemoryAccounting::kFairShare:
+        result += cord_internal::GetEstimatedFairShareMemoryUsage(rep);
+        break;
+      case CordMemoryAccounting::kTotalMorePrecise:
+        result += cord_internal::GetMorePreciseMemoryUsage(rep);
+        break;
+      case CordMemoryAccounting::kTotal:
+        result += cord_internal::GetEstimatedMemoryUsage(rep);
+        break;
     }
   }
   return result;
diff --git a/absl/strings/cord_analysis.cc b/absl/strings/cord_analysis.cc
index 73d3c4e6..e859b0db 100644
--- a/absl/strings/cord_analysis.cc
+++ b/absl/strings/cord_analysis.cc
@@ -16,6 +16,7 @@
 
 #include <cstddef>
 #include <cstdint>
+#include <unordered_set>
 
 #include "absl/base/attributes.h"
 #include "absl/base/config.h"
@@ -37,7 +38,7 @@ namespace cord_internal {
 namespace {
 
 // Accounting mode for analyzing memory usage.
-enum class Mode { kTotal, kFairShare };
+enum class Mode { kFairShare, kTotal, kTotalMorePrecise };
 
 // CordRepRef holds a `const CordRep*` reference in rep, and depending on mode,
 // holds a 'fraction' representing a cumulative inverse refcount weight.
@@ -62,6 +63,23 @@ struct RawUsage {
   void Add(size_t size, CordRepRef<mode>) { total += size; }
 };
 
+// Overloaded representation of RawUsage that tracks the set of objects
+// counted, and avoids double-counting objects referenced more than once
+// by the same Cord.
+template <>
+struct RawUsage<Mode::kTotalMorePrecise> {
+  size_t total = 0;
+  // TODO(b/289250880): Replace this with a flat_hash_set.
+  std::unordered_set<const CordRep*> counted;
+
+  void Add(size_t size, CordRepRef<Mode::kTotalMorePrecise> repref) {
+    if (counted.find(repref.rep) == counted.end()) {
+      counted.insert(repref.rep);
+      total += size;
+    }
+  }
+};
+
 // Returns n / refcount avoiding a div for the common refcount == 1.
 template <typename refcount_t>
 double MaybeDiv(double d, refcount_t refcount) {
@@ -183,6 +201,10 @@ size_t GetEstimatedFairShareMemoryUsage(const CordRep* rep) {
   return GetEstimatedUsage<Mode::kFairShare>(rep);
 }
 
+size_t GetMorePreciseMemoryUsage(const CordRep* rep) {
+  return GetEstimatedUsage<Mode::kTotalMorePrecise>(rep);
+}
+
 }  // namespace cord_internal
 ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/strings/cord_analysis.h b/absl/strings/cord_analysis.h
index 7041ad1a..9b9527a5 100644
--- a/absl/strings/cord_analysis.h
+++ b/absl/strings/cord_analysis.h
@@ -31,6 +31,24 @@ namespace cord_internal {
 size_t GetEstimatedMemoryUsage(const CordRep* rep);
 
 // Returns the *approximate* number of bytes held in full or in part by this
+// Cord for the distinct memory held by this cord. This is similar to
+// `GetEstimatedMemoryUsage()`, except that if the cord has multiple references
+// to the same memory, that memory is only counted once.
+//
+// For example:
+//   absl::Cord cord;
+//   cord.append(some_other_cord);
+//   cord.append(some_other_cord);
+//    // Calls GetEstimatedMemoryUsage() and counts `other_cord` twice:
+//   cord.EstimatedMemoryUsage(kTotal);
+//    // Calls GetMorePreciseMemoryUsage() and counts `other_cord` once:
+//   cord.EstimatedMemoryUsage(kTotalMorePrecise);
+//
+// This is more expensive than `GetEstimatedMemoryUsage()` as it requires
+// deduplicating all memory references.
+size_t GetMorePreciseMemoryUsage(const CordRep* rep);
+
+// Returns the *approximate* number of bytes held in full or in part by this
 // CordRep weighted by the sharing ratio of that data. For example, if some data
 // edge is shared by 4 different Cords, then each cord is attribute 1/4th of
 // the total memory usage as a 'fair share' of the total memory usage.
diff --git a/absl/strings/cord_buffer.h b/absl/strings/cord_buffer.h
index 15494b31..bc0e4e45 100644
--- a/absl/strings/cord_buffer.h
+++ b/absl/strings/cord_buffer.h
@@ -160,7 +160,6 @@ class CordBuffer {
   // for more information on buffer capacities and intended usage.
   static CordBuffer CreateWithDefaultLimit(size_t capacity);
 
-
   // CordBuffer::CreateWithCustomLimit()
   //
   // Creates a CordBuffer instance of the desired `capacity` rounded to an
@@ -336,7 +335,7 @@ class CordBuffer {
     }
 
     // Returns the available area of the internal SSO data
-    absl::Span<char> long_available() {
+    absl::Span<char> long_available() const {
       assert(!is_short());
       const size_t length = long_rep.rep->length;
       return absl::Span<char>(long_rep.rep->Data() + length,
@@ -460,9 +459,7 @@ inline constexpr size_t CordBuffer::MaximumPayload() {
 }
 
 inline constexpr size_t CordBuffer::MaximumPayload(size_t block_size) {
-  // TODO(absl-team): Use std::min when C++11 support is dropped.
-  return (kCustomLimit < block_size ? kCustomLimit : block_size) -
-         cord_internal::kFlatOverhead;
+  return (std::min)(kCustomLimit, block_size) - cord_internal::kFlatOverhead;
 }
 
 inline CordBuffer CordBuffer::CreateWithDefaultLimit(size_t capacity) {
diff --git a/absl/strings/cord_test.cc b/absl/strings/cord_test.cc
index 5603e94c..36e397ed 100644
--- a/absl/strings/cord_test.cc
+++ b/absl/strings/cord_test.cc
@@ -30,10 +30,11 @@
 #include "gtest/gtest.h"
 #include "absl/base/config.h"
 #include "absl/base/internal/endian.h"
-#include "absl/base/internal/raw_logging.h"
 #include "absl/base/macros.h"
 #include "absl/container/fixed_array.h"
 #include "absl/hash/hash.h"
+#include "absl/log/check.h"
+#include "absl/log/log.h"
 #include "absl/random/random.h"
 #include "absl/strings/cord_test_helpers.h"
 #include "absl/strings/cordz_test_helpers.h"
@@ -58,6 +59,8 @@ using absl::cord_internal::CordRepSubstring;
 using absl::cord_internal::CordzUpdateTracker;
 using absl::cord_internal::kFlatOverhead;
 using absl::cord_internal::kMaxFlatLength;
+using ::testing::ElementsAre;
+using ::testing::Le;
 
 static std::string RandomLowercaseString(RandomEngine* rng);
 static std::string RandomLowercaseString(RandomEngine* rng, size_t length);
@@ -208,9 +211,8 @@ class CordTestPeer {
   }
 
   static Cord MakeSubstring(Cord src, size_t offset, size_t length) {
-    ABSL_RAW_CHECK(src.contents_.is_tree(), "Can not be inlined");
-    ABSL_RAW_CHECK(src.ExpectedChecksum() == absl::nullopt,
-                   "Can not be hardened");
+    CHECK(src.contents_.is_tree()) << "Can not be inlined";
+    CHECK(!src.ExpectedChecksum().has_value()) << "Can not be hardened";
     Cord cord;
     auto* tree = cord_internal::SkipCrcNode(src.contents_.tree());
     auto* rep = CordRepSubstring::Create(CordRep::Ref(tree), offset, length);
@@ -372,7 +374,7 @@ TEST_P(CordTest, GigabyteCordFromExternal) {
   for (int i = 0; i < 1024; ++i) {
     c.Append(from);
   }
-  ABSL_RAW_LOG(INFO, "Made a Cord with %zu bytes!", c.size());
+  LOG(INFO) << "Made a Cord with " << c.size() << " bytes!";
   // Note: on a 32-bit build, this comes out to   2,818,048,000 bytes.
   // Note: on a 64-bit build, this comes out to 171,932,385,280 bytes.
 }
@@ -618,7 +620,7 @@ TEST_P(CordTest, AppendEmptyBufferToTree) {
 TEST_P(CordTest, AppendSmallBuffer) {
   absl::Cord cord;
   absl::CordBuffer buffer = absl::CordBuffer::CreateWithDefaultLimit(3);
-  ASSERT_THAT(buffer.capacity(), ::testing::Le(15));
+  ASSERT_THAT(buffer.capacity(), Le(15));
   memcpy(buffer.data(), "Abc", 3);
   buffer.SetLength(3);
   cord.Append(std::move(buffer));
@@ -632,7 +634,7 @@ TEST_P(CordTest, AppendSmallBuffer) {
   EXPECT_EQ(buffer.length(), 0);    // NOLINT
   EXPECT_GT(buffer.capacity(), 0);  // NOLINT
 
-  EXPECT_THAT(cord.Chunks(), ::testing::ElementsAre("Abcdefgh"));
+  EXPECT_THAT(cord.Chunks(), ElementsAre("Abcdefgh"));
 }
 
 TEST_P(CordTest, AppendAndPrependBufferArePrecise) {
@@ -671,7 +673,7 @@ TEST_P(CordTest, AppendAndPrependBufferArePrecise) {
 TEST_P(CordTest, PrependSmallBuffer) {
   absl::Cord cord;
   absl::CordBuffer buffer = absl::CordBuffer::CreateWithDefaultLimit(3);
-  ASSERT_THAT(buffer.capacity(), ::testing::Le(15));
+  ASSERT_THAT(buffer.capacity(), Le(15));
   memcpy(buffer.data(), "Abc", 3);
   buffer.SetLength(3);
   cord.Prepend(std::move(buffer));
@@ -685,7 +687,7 @@ TEST_P(CordTest, PrependSmallBuffer) {
   EXPECT_EQ(buffer.length(), 0);    // NOLINT
   EXPECT_GT(buffer.capacity(), 0);  // NOLINT
 
-  EXPECT_THAT(cord.Chunks(), ::testing::ElementsAre("defghAbc"));
+  EXPECT_THAT(cord.Chunks(), ElementsAre("defghAbc"));
 }
 
 TEST_P(CordTest, AppendLargeBuffer) {
@@ -707,7 +709,7 @@ TEST_P(CordTest, AppendLargeBuffer) {
   EXPECT_EQ(buffer.length(), 0);    // NOLINT
   EXPECT_GT(buffer.capacity(), 0);  // NOLINT
 
-  EXPECT_THAT(cord.Chunks(), ::testing::ElementsAre(s1, s2));
+  EXPECT_THAT(cord.Chunks(), ElementsAre(s1, s2));
 }
 
 TEST_P(CordTest, PrependLargeBuffer) {
@@ -729,7 +731,7 @@ TEST_P(CordTest, PrependLargeBuffer) {
   EXPECT_EQ(buffer.length(), 0);    // NOLINT
   EXPECT_GT(buffer.capacity(), 0);  // NOLINT
 
-  EXPECT_THAT(cord.Chunks(), ::testing::ElementsAre(s2, s1));
+  EXPECT_THAT(cord.Chunks(), ElementsAre(s2, s1));
 }
 
 class CordAppendBufferTest : public testing::TestWithParam<bool> {
@@ -1245,15 +1247,15 @@ absl::Cord BigCord(size_t len, char v) {
 // Splice block into cord.
 absl::Cord SpliceCord(const absl::Cord& blob, int64_t offset,
                       const absl::Cord& block) {
-  ABSL_RAW_CHECK(offset >= 0, "");
-  ABSL_RAW_CHECK(offset + block.size() <= blob.size(), "");
+  CHECK_GE(offset, 0);
+  CHECK_LE(static_cast<size_t>(offset) + block.size(), blob.size());
   absl::Cord result(blob);
   result.RemoveSuffix(blob.size() - offset);
   result.Append(block);
   absl::Cord suffix(blob);
   suffix.RemovePrefix(offset + block.size());
   result.Append(suffix);
-  ABSL_RAW_CHECK(blob.size() == result.size(), "");
+  CHECK_EQ(blob.size(), result.size());
   return result;
 }
 
@@ -1763,6 +1765,8 @@ TEST_P(CordTest, ExternalMemoryGet) {
 // of empty and inlined cords, and flat nodes.
 
 constexpr auto kFairShare = absl::CordMemoryAccounting::kFairShare;
+constexpr auto kTotalMorePrecise =
+    absl::CordMemoryAccounting::kTotalMorePrecise;
 
 // Creates a cord of `n` `c` values, making sure no string stealing occurs.
 absl::Cord MakeCord(size_t n, char c) {
@@ -1774,12 +1778,14 @@ TEST(CordTest, CordMemoryUsageEmpty) {
   absl::Cord cord;
   EXPECT_EQ(sizeof(absl::Cord), cord.EstimatedMemoryUsage());
   EXPECT_EQ(sizeof(absl::Cord), cord.EstimatedMemoryUsage(kFairShare));
+  EXPECT_EQ(sizeof(absl::Cord), cord.EstimatedMemoryUsage(kTotalMorePrecise));
 }
 
 TEST(CordTest, CordMemoryUsageInlined) {
   absl::Cord a("hello");
   EXPECT_EQ(a.EstimatedMemoryUsage(), sizeof(absl::Cord));
   EXPECT_EQ(a.EstimatedMemoryUsage(kFairShare), sizeof(absl::Cord));
+  EXPECT_EQ(a.EstimatedMemoryUsage(kTotalMorePrecise), sizeof(absl::Cord));
 }
 
 TEST(CordTest, CordMemoryUsageExternalMemory) {
@@ -1789,6 +1795,7 @@ TEST(CordTest, CordMemoryUsageExternalMemory) {
       sizeof(absl::Cord) + 1000 + sizeof(CordRepExternal) + sizeof(intptr_t);
   EXPECT_EQ(cord.EstimatedMemoryUsage(), expected);
   EXPECT_EQ(cord.EstimatedMemoryUsage(kFairShare), expected);
+  EXPECT_EQ(cord.EstimatedMemoryUsage(kTotalMorePrecise), expected);
 }
 
 TEST(CordTest, CordMemoryUsageFlat) {
@@ -1798,6 +1805,8 @@ TEST(CordTest, CordMemoryUsageFlat) {
   EXPECT_EQ(cord.EstimatedMemoryUsage(), sizeof(absl::Cord) + flat_size);
   EXPECT_EQ(cord.EstimatedMemoryUsage(kFairShare),
             sizeof(absl::Cord) + flat_size);
+  EXPECT_EQ(cord.EstimatedMemoryUsage(kTotalMorePrecise),
+            sizeof(absl::Cord) + flat_size);
 }
 
 TEST(CordTest, CordMemoryUsageSubStringSharedFlat) {
@@ -1807,6 +1816,8 @@ TEST(CordTest, CordMemoryUsageSubStringSharedFlat) {
   absl::Cord cord = flat.Subcord(500, 1000);
   EXPECT_EQ(cord.EstimatedMemoryUsage(),
             sizeof(absl::Cord) + sizeof(CordRepSubstring) + flat_size);
+  EXPECT_EQ(cord.EstimatedMemoryUsage(kTotalMorePrecise),
+            sizeof(absl::Cord) + sizeof(CordRepSubstring) + flat_size);
   EXPECT_EQ(cord.EstimatedMemoryUsage(kFairShare),
             sizeof(absl::Cord) + sizeof(CordRepSubstring) + flat_size / 2);
 }
@@ -1817,6 +1828,8 @@ TEST(CordTest, CordMemoryUsageFlatShared) {
   const size_t flat_size =
       absl::CordTestPeer::Tree(cord)->flat()->AllocatedSize();
   EXPECT_EQ(cord.EstimatedMemoryUsage(), sizeof(absl::Cord) + flat_size);
+  EXPECT_EQ(cord.EstimatedMemoryUsage(kTotalMorePrecise),
+            sizeof(absl::Cord) + flat_size);
   EXPECT_EQ(cord.EstimatedMemoryUsage(kFairShare),
             sizeof(absl::Cord) + flat_size / 2);
 }
@@ -1835,6 +1848,8 @@ TEST(CordTest, CordMemoryUsageFlatHardenedAndShared) {
   absl::Cord cord2(cord);
   EXPECT_EQ(cord2.EstimatedMemoryUsage(),
             sizeof(absl::Cord) + sizeof(CordRepCrc) + flat_size);
+  EXPECT_EQ(cord2.EstimatedMemoryUsage(kTotalMorePrecise),
+            sizeof(absl::Cord) + sizeof(CordRepCrc) + flat_size);
   EXPECT_EQ(cord2.EstimatedMemoryUsage(kFairShare),
             sizeof(absl::Cord) + (sizeof(CordRepCrc) + flat_size / 2) / 2);
 }
@@ -1853,7 +1868,7 @@ TEST(CordTest, CordMemoryUsageBTree) {
   // windows DLL, we may have ODR like effects on the flag, meaning the DLL
   // code will run with the picked up default.
   if (!absl::CordTestPeer::Tree(cord1)->IsBtree()) {
-    ABSL_RAW_LOG(WARNING, "Cord library code not respecting btree flag");
+    LOG(WARNING) << "Cord library code not respecting btree flag";
     return;
   }
 
@@ -1861,6 +1876,8 @@ TEST(CordTest, CordMemoryUsageBTree) {
   size_t rep1_shared_size = sizeof(CordRepBtree) + flats1_size / 2;
 
   EXPECT_EQ(cord1.EstimatedMemoryUsage(), sizeof(absl::Cord) + rep1_size);
+  EXPECT_EQ(cord1.EstimatedMemoryUsage(kTotalMorePrecise),
+            sizeof(absl::Cord) + rep1_size);
   EXPECT_EQ(cord1.EstimatedMemoryUsage(kFairShare),
             sizeof(absl::Cord) + rep1_shared_size);
 
@@ -1875,6 +1892,8 @@ TEST(CordTest, CordMemoryUsageBTree) {
   size_t rep2_size = sizeof(CordRepBtree) + flats2_size;
 
   EXPECT_EQ(cord2.EstimatedMemoryUsage(), sizeof(absl::Cord) + rep2_size);
+  EXPECT_EQ(cord2.EstimatedMemoryUsage(kTotalMorePrecise),
+            sizeof(absl::Cord) + rep2_size);
   EXPECT_EQ(cord2.EstimatedMemoryUsage(kFairShare),
             sizeof(absl::Cord) + rep2_size);
 
@@ -1883,6 +1902,8 @@ TEST(CordTest, CordMemoryUsageBTree) {
 
   EXPECT_EQ(cord.EstimatedMemoryUsage(),
             sizeof(absl::Cord) + sizeof(CordRepBtree) + rep1_size + rep2_size);
+  EXPECT_EQ(cord.EstimatedMemoryUsage(kTotalMorePrecise),
+            sizeof(absl::Cord) + sizeof(CordRepBtree) + rep1_size + rep2_size);
   EXPECT_EQ(cord.EstimatedMemoryUsage(kFairShare),
             sizeof(absl::Cord) + sizeof(CordRepBtree) + rep1_shared_size / 2 +
                 rep2_size);
@@ -1901,6 +1922,66 @@ TEST_P(CordTest, CordMemoryUsageInlineRep) {
   EXPECT_EQ(c1.EstimatedMemoryUsage(), c2.EstimatedMemoryUsage());
 }
 
+TEST_P(CordTest, CordMemoryUsageTotalMorePreciseMode) {
+  constexpr size_t kChunkSize = 2000;
+  std::string tmp_str(kChunkSize, 'x');
+  const absl::Cord flat(std::move(tmp_str));
+
+  // Construct `fragmented` with two references into the same
+  // underlying buffer shared with `flat`:
+  absl::Cord fragmented(flat);
+  fragmented.Append(flat);
+
+  // Memory usage of `flat`, minus the top-level Cord object:
+  const size_t flat_internal_usage =
+      flat.EstimatedMemoryUsage() - sizeof(absl::Cord);
+
+  // `fragmented` holds a Cord and a CordRepBtree. That tree points to two
+  // copies of flat's internals, which we expect to dedup:
+  EXPECT_EQ(fragmented.EstimatedMemoryUsage(kTotalMorePrecise),
+            sizeof(absl::Cord) +
+            sizeof(CordRepBtree) +
+            flat_internal_usage);
+
+  // This is a case where kTotal produces an overestimate:
+  EXPECT_EQ(fragmented.EstimatedMemoryUsage(),
+            sizeof(absl::Cord) +
+            sizeof(CordRepBtree) +
+            2 * flat_internal_usage);
+}
+
+TEST_P(CordTest, CordMemoryUsageTotalMorePreciseModeWithSubstring) {
+  constexpr size_t kChunkSize = 2000;
+  std::string tmp_str(kChunkSize, 'x');
+  const absl::Cord flat(std::move(tmp_str));
+
+  // Construct `fragmented` with two references into the same
+  // underlying buffer shared with `flat`.
+  //
+  // This time, each reference is through a Subcord():
+  absl::Cord fragmented;
+  fragmented.Append(flat.Subcord(1, kChunkSize - 2));
+  fragmented.Append(flat.Subcord(1, kChunkSize - 2));
+
+  // Memory usage of `flat`, minus the top-level Cord object:
+  const size_t flat_internal_usage =
+      flat.EstimatedMemoryUsage() - sizeof(absl::Cord);
+
+  // `fragmented` holds a Cord and a CordRepBtree. That tree points to two
+  // CordRepSubstrings, each pointing at flat's internals.
+  EXPECT_EQ(fragmented.EstimatedMemoryUsage(kTotalMorePrecise),
+            sizeof(absl::Cord) +
+            sizeof(CordRepBtree) +
+            2 * sizeof(CordRepSubstring) +
+            flat_internal_usage);
+
+  // This is a case where kTotal produces an overestimate:
+  EXPECT_EQ(fragmented.EstimatedMemoryUsage(),
+            sizeof(absl::Cord) +
+            sizeof(CordRepBtree) +
+            2 * sizeof(CordRepSubstring) +
+            2 * flat_internal_usage);
+}
 }  // namespace
 
 // Regtest for 7510292 (fix a bug introduced by 7465150)
@@ -1938,8 +2019,7 @@ TEST_P(CordTest, DiabolicalGrowth) {
   std::string value;
   absl::CopyCordToString(cord, &value);
   EXPECT_EQ(value, expected);
-  ABSL_RAW_LOG(INFO, "Diabolical size allocated = %zu",
-               cord.EstimatedMemoryUsage());
+  LOG(INFO) << "Diabolical size allocated = " << cord.EstimatedMemoryUsage();
 }
 
 // The following tests check support for >4GB cords in 64-bit binaries, and
diff --git a/absl/strings/cord_test_helpers.h b/absl/strings/cord_test_helpers.h
index 31a1dc89..ca52240a 100644
--- a/absl/strings/cord_test_helpers.h
+++ b/absl/strings/cord_test_helpers.h
@@ -51,7 +51,7 @@ enum class TestCordSize {
   // existing inputs rather than copying contents of the input.
   kMedium = cord_internal::kMaxFlatLength / 2 + 1,
 
-  // A string value large enough to cause it to be stored in mutliple flats.
+  // A string value large enough to cause it to be stored in multiple flats.
   kLarge = cord_internal::kMaxFlatLength * 4
 };
 
diff --git a/absl/strings/escaping.cc b/absl/strings/escaping.cc
index 93966846..2827fbaa 100644
--- a/absl/strings/escaping.cc
+++ b/absl/strings/escaping.cc
@@ -443,6 +443,8 @@ void CEscapeAndAppendInternal(absl::string_view src, std::string* dest) {
   }
 }
 
+// Reverses the mapping in Base64EscapeInternal; see that method's
+// documentation for details of the mapping.
 bool Base64UnescapeInternal(const char* src_param, size_t szsrc, char* dest,
                             size_t szdest, const signed char* unbase64,
                             size_t* len) {
@@ -676,7 +678,10 @@ bool Base64UnescapeInternal(const char* src_param, size_t szsrc, char* dest,
   return ok;
 }
 
-// The arrays below were generated by the following code
+// The arrays below map base64-escaped characters back to their original values.
+// For the inverse case, see k(WebSafe)Base64Chars in the internal
+// escaping.cc.
+// These arrays were generated by the following inversion code:
 // #include <sys/time.h>
 // #include <stdlib.h>
 // #include <string.h>
@@ -703,8 +708,8 @@ bool Base64UnescapeInternal(const char* src_param, size_t szsrc, char* dest,
 //   }
 // }
 //
-// where the value of "Base64[]" was replaced by one of the base-64 conversion
-// tables from the functions below.
+// where the value of "Base64[]" was replaced by one of k(WebSafe)Base64Chars
+// in the internal escaping.cc.
 /* clang-format off */
 constexpr signed char kUnBase64[] = {
     -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
@@ -777,9 +782,6 @@ constexpr signed char kUnWebSafeBase64[] = {
 };
 /* clang-format on */
 
-constexpr char kWebSafeBase64Chars[] =
-    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_";
-
 template <typename String>
 bool Base64UnescapeInternal(const char* src, size_t slen, String* dest,
                             const signed char* unbase64) {
@@ -880,30 +882,6 @@ std::string Utf8SafeCHexEscape(absl::string_view src) {
   return CEscapeInternal(src, true, true);
 }
 
-// ----------------------------------------------------------------------
-// Base64Unescape() - base64 decoder
-// Base64Escape() - base64 encoder
-// WebSafeBase64Unescape() - Google's variation of base64 decoder
-// WebSafeBase64Escape() - Google's variation of base64 encoder
-//
-// Check out
-// https://datatracker.ietf.org/doc/html/rfc2045 for formal description, but
-// what we care about is that...
-//   Take the encoded stuff in groups of 4 characters and turn each
-//   character into a code 0 to 63 thus:
-//           A-Z map to 0 to 25
-//           a-z map to 26 to 51
-//           0-9 map to 52 to 61
-//           +(- for WebSafe) maps to 62
-//           /(_ for WebSafe) maps to 63
-//   There will be four numbers, all less than 64 which can be represented
-//   by a 6 digit binary number (aaaaaa, bbbbbb, cccccc, dddddd respectively).
-//   Arrange the 6 digit binary numbers into three bytes as such:
-//   aaaaaabb bbbbcccc ccdddddd
-//   Equals signs (one or two) are used at the end of the encoded block to
-//   indicate that the text was not an integer multiple of three bytes long.
-// ----------------------------------------------------------------------
-
 bool Base64Unescape(absl::string_view src, std::string* dest) {
   return Base64UnescapeInternal(src.data(), src.size(), dest, kUnBase64);
 }
@@ -921,7 +899,7 @@ void Base64Escape(absl::string_view src, std::string* dest) {
 void WebSafeBase64Escape(absl::string_view src, std::string* dest) {
   strings_internal::Base64EscapeInternal(
       reinterpret_cast<const unsigned char*>(src.data()), src.size(), dest,
-      false, kWebSafeBase64Chars);
+      false, strings_internal::kWebSafeBase64Chars);
 }
 
 std::string Base64Escape(absl::string_view src) {
@@ -936,7 +914,7 @@ std::string WebSafeBase64Escape(absl::string_view src) {
   std::string dest;
   strings_internal::Base64EscapeInternal(
       reinterpret_cast<const unsigned char*>(src.data()), src.size(), &dest,
-      false, kWebSafeBase64Chars);
+      false, strings_internal::kWebSafeBase64Chars);
   return dest;
 }
 
diff --git a/absl/strings/escaping.h b/absl/strings/escaping.h
index 7c082fef..bf2a5898 100644
--- a/absl/strings/escaping.h
+++ b/absl/strings/escaping.h
@@ -121,7 +121,7 @@ std::string Utf8SafeCHexEscape(absl::string_view src);
 //
 // Encodes a `src` string into a base64-encoded 'dest' string with padding
 // characters. This function conforms with RFC 4648 section 4 (base64) and RFC
-// 2045. See also CalculateBase64EscapedLen().
+// 2045.
 void Base64Escape(absl::string_view src, std::string* dest);
 std::string Base64Escape(absl::string_view src);
 
diff --git a/absl/strings/escaping_test.cc b/absl/strings/escaping_test.cc
index 44ffcba7..9f62c1ee 100644
--- a/absl/strings/escaping_test.cc
+++ b/absl/strings/escaping_test.cc
@@ -562,6 +562,7 @@ template <typename StringType>
 void TestEscapeAndUnescape() {
   // Check the short strings; this tests the math (and boundaries)
   for (const auto& tc : base64_tests) {
+    // Test plain base64.
     StringType encoded("this junk should be ignored");
     absl::Base64Escape(tc.plaintext, &encoded);
     EXPECT_EQ(encoded, tc.cyphertext);
@@ -571,22 +572,26 @@ void TestEscapeAndUnescape() {
     EXPECT_TRUE(absl::Base64Unescape(encoded, &decoded));
     EXPECT_EQ(decoded, tc.plaintext);
 
-    StringType websafe(tc.cyphertext);
-    for (int c = 0; c < websafe.size(); ++c) {
-      if ('+' == websafe[c]) websafe[c] = '-';
-      if ('/' == websafe[c]) websafe[c] = '_';
+    StringType websafe_with_padding(tc.cyphertext);
+    for (unsigned int c = 0; c < websafe_with_padding.size(); ++c) {
+      if ('+' == websafe_with_padding[c]) websafe_with_padding[c] = '-';
+      if ('/' == websafe_with_padding[c]) websafe_with_padding[c] = '_';
+      // Intentionally keeping padding aka '='.
+    }
+
+    // Test plain websafe (aka without padding).
+    StringType websafe(websafe_with_padding);
+    for (unsigned int c = 0; c < websafe.size(); ++c) {
       if ('=' == websafe[c]) {
         websafe.resize(c);
         break;
       }
     }
-
     encoded = "this junk should be ignored";
     absl::WebSafeBase64Escape(tc.plaintext, &encoded);
     EXPECT_EQ(encoded, websafe);
     EXPECT_EQ(absl::WebSafeBase64Escape(tc.plaintext), websafe);
 
-    // Let's try the string version of the decoder
     decoded = "this junk should be ignored";
     EXPECT_TRUE(absl::WebSafeBase64Unescape(websafe, &decoded));
     EXPECT_EQ(decoded, tc.plaintext);
diff --git a/absl/strings/internal/charconv_bigint.cc b/absl/strings/internal/charconv_bigint.cc
index 282b639e..46b5289a 100644
--- a/absl/strings/internal/charconv_bigint.cc
+++ b/absl/strings/internal/charconv_bigint.cc
@@ -296,10 +296,8 @@ template <int max_words>
         std::min(n / kLargePowerOfFiveStep, kLargestPowerOfFiveIndex);
     if (first_pass) {
       // just copy, rather than multiplying by 1
-      std::copy(
-          LargePowerOfFiveData(big_power),
-          LargePowerOfFiveData(big_power) + LargePowerOfFiveSize(big_power),
-          answer.words_);
+      std::copy_n(LargePowerOfFiveData(big_power),
+                  LargePowerOfFiveSize(big_power), answer.words_);
       answer.size_ = LargePowerOfFiveSize(big_power);
       first_pass = false;
     } else {
diff --git a/absl/strings/internal/charconv_bigint.h b/absl/strings/internal/charconv_bigint.h
index 8f702976..5c0c375d 100644
--- a/absl/strings/internal/charconv_bigint.h
+++ b/absl/strings/internal/charconv_bigint.h
@@ -92,7 +92,7 @@ class BigUnsigned {
   // numbers with this many decimal digits or fewer are representable by this
   // type.
   //
-  // Analagous to std::numeric_limits<BigUnsigned>::digits10.
+  // Analogous to std::numeric_limits<BigUnsigned>::digits10.
   static constexpr int Digits10() {
     // 9975007/1035508 is very slightly less than log10(2**32).
     return static_cast<uint64_t>(max_words) * 9975007 / 1035508;
@@ -121,7 +121,7 @@ class BigUnsigned {
           ++size_;
         }
       }
-      std::fill(words_, words_ + word_shift, 0u);
+      std::fill_n(words_, word_shift, 0u);
     }
   }
 
@@ -197,7 +197,7 @@ class BigUnsigned {
   }
 
   void SetToZero() {
-    std::fill(words_, words_ + size_, 0u);
+    std::fill_n(words_, size_, 0u);
     size_ = 0;
   }
 
diff --git a/absl/strings/internal/charconv_parse_test.cc b/absl/strings/internal/charconv_parse_test.cc
index bc2d1118..2b7b0821 100644
--- a/absl/strings/internal/charconv_parse_test.cc
+++ b/absl/strings/internal/charconv_parse_test.cc
@@ -19,7 +19,7 @@
 
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
-#include "absl/base/internal/raw_logging.h"
+#include "absl/log/check.h"
 #include "absl/strings/str_cat.h"
 
 using absl::chars_format;
@@ -56,14 +56,14 @@ void ExpectParsedFloat(std::string s, absl::chars_format format_flags,
     begin_subrange = static_cast<int>(open_bracket_pos);
     s.replace(open_bracket_pos, 1, "");
     std::string::size_type close_bracket_pos = s.find(']');
-    ABSL_RAW_CHECK(close_bracket_pos != absl::string_view::npos,
-                   "Test input contains [ without matching ]");
+    CHECK_NE(close_bracket_pos, absl::string_view::npos)
+        << "Test input contains [ without matching ]";
     end_subrange = static_cast<int>(close_bracket_pos);
     s.replace(close_bracket_pos, 1, "");
   }
   const std::string::size_type expected_characters_matched = s.find('$');
-  ABSL_RAW_CHECK(expected_characters_matched != std::string::npos,
-                 "Input string must contain $");
+  CHECK_NE(expected_characters_matched, std::string::npos)
+      << "Input string must contain $";
   s.replace(expected_characters_matched, 1, "");
 
   ParsedFloat parsed =
diff --git a/absl/strings/internal/cord_internal.cc b/absl/strings/internal/cord_internal.cc
index b6b06cfa..b7874385 100644
--- a/absl/strings/internal/cord_internal.cc
+++ b/absl/strings/internal/cord_internal.cc
@@ -33,7 +33,6 @@ ABSL_CONST_INIT std::atomic<bool> cord_ring_buffer_enabled(
     kCordEnableRingBufferDefault);
 ABSL_CONST_INIT std::atomic<bool> shallow_subcords_enabled(
     kCordShallowSubcordsDefault);
-ABSL_CONST_INIT std::atomic<bool> cord_btree_exhaustive_validation(false);
 
 void LogFatalNodeType(CordRep* rep) {
   ABSL_INTERNAL_LOG(FATAL, absl::StrCat("Unexpected node type: ",
diff --git a/absl/strings/internal/cord_internal.h b/absl/strings/internal/cord_internal.h
index e6f0d544..20dd008c 100644
--- a/absl/strings/internal/cord_internal.h
+++ b/absl/strings/internal/cord_internal.h
@@ -69,12 +69,6 @@ enum CordFeatureDefaults {
 extern std::atomic<bool> cord_ring_buffer_enabled;
 extern std::atomic<bool> shallow_subcords_enabled;
 
-// `cord_btree_exhaustive_validation` can be set to force exhaustive validation
-// in debug assertions, and code that calls `IsValid()` explicitly. By default,
-// assertions should be relatively cheap and AssertValid() can easily lead to
-// O(n^2) complexity as recursive / full tree validation is O(n).
-extern std::atomic<bool> cord_btree_exhaustive_validation;
-
 inline void enable_cord_ring_buffer(bool enable) {
   cord_ring_buffer_enabled.store(enable, std::memory_order_relaxed);
 }
@@ -163,20 +157,19 @@ class RefcountAndFlags {
   // false will be visible to a thread that just observed this method returning
   // false.  Always returns false when the immortal bit is set.
   inline bool Decrement() {
-    int32_t refcount = count_.load(std::memory_order_acquire) & kRefcountMask;
-    assert(refcount > 0 || refcount & kImmortalFlag);
+    int32_t refcount = count_.load(std::memory_order_acquire);
+    assert((refcount & kRefcountMask) > 0 || refcount & kImmortalFlag);
     return refcount != kRefIncrement &&
            (count_.fetch_sub(kRefIncrement, std::memory_order_acq_rel) &
-            kRefcountMask) != kRefIncrement;
+            kHighRefcountMask) != 0;
   }
 
   // Same as Decrement but expect that refcount is greater than 1.
   inline bool DecrementExpectHighRefcount() {
     int32_t refcount =
-        count_.fetch_sub(kRefIncrement, std::memory_order_acq_rel) &
-        kRefcountMask;
-    assert(refcount > 0 || refcount & kImmortalFlag);
-    return refcount != kRefIncrement;
+        count_.fetch_sub(kRefIncrement, std::memory_order_acq_rel);
+    assert((refcount & kRefcountMask) > 0 || refcount & kImmortalFlag);
+    return (refcount & kHighRefcountMask) != 0;
   }
 
   // Returns the current reference count using acquire semantics.
@@ -220,6 +213,15 @@ class RefcountAndFlags {
     // purposes of equality.  (A refcount of 0 or 1 does not count as 0 or 1
     // if the immortal bit is set.)
     kRefcountMask = ~kReservedFlag,
+
+    // Bitmask to use when checking if refcount is equal to 1 and not
+    // immortal when decrementing the refcount. This masks out kRefIncrement and
+    // all flags except kImmortalFlag. If the masked RefcountAndFlags is 0, we
+    // assume the refcount is equal to 1, since we know it's not immortal and
+    // not greater than 1. If the masked RefcountAndFlags is not 0, we can
+    // assume the refcount is not equal to 1 since either a higher bit in the
+    // refcount is set, or kImmortal is set.
+    kHighRefcountMask = kRefcountMask & ~kRefIncrement,
   };
 
   std::atomic<int32_t> count_;
diff --git a/absl/strings/internal/cord_rep_btree.cc b/absl/strings/internal/cord_rep_btree.cc
index a86fdc0b..05bd0e20 100644
--- a/absl/strings/internal/cord_rep_btree.cc
+++ b/absl/strings/internal/cord_rep_btree.cc
@@ -14,6 +14,7 @@
 
 #include "absl/strings/internal/cord_rep_btree.h"
 
+#include <atomic>
 #include <cassert>
 #include <cstdint>
 #include <iostream>
@@ -49,9 +50,7 @@ using CopyResult = CordRepBtree::CopyResult;
 constexpr auto kFront = CordRepBtree::kFront;
 constexpr auto kBack = CordRepBtree::kBack;
 
-inline bool exhaustive_validation() {
-  return cord_btree_exhaustive_validation.load(std::memory_order_relaxed);
-}
+ABSL_CONST_INIT std::atomic<bool> cord_btree_exhaustive_validation(false);
 
 // Implementation of the various 'Dump' functions.
 // Prints the entire tree structure or 'rep'. External callers should
@@ -362,6 +361,15 @@ struct StackOperations {
 
 }  // namespace
 
+void SetCordBtreeExhaustiveValidation(bool do_exaustive_validation) {
+  cord_btree_exhaustive_validation.store(do_exaustive_validation,
+                                         std::memory_order_relaxed);
+}
+
+bool IsCordBtreeExhaustiveValidationEnabled() {
+  return cord_btree_exhaustive_validation.load(std::memory_order_relaxed);
+}
+
 void CordRepBtree::Dump(const CordRep* rep, absl::string_view label,
                         bool include_contents, std::ostream& stream) {
   stream << "===================================\n";
@@ -450,7 +458,8 @@ bool CordRepBtree::IsValid(const CordRepBtree* tree, bool shallow) {
     child_length += edge->length;
   }
   NODE_CHECK_EQ(child_length, tree->length);
-  if ((!shallow || exhaustive_validation()) && tree->height() > 0) {
+  if ((!shallow || IsCordBtreeExhaustiveValidationEnabled()) &&
+      tree->height() > 0) {
     for (CordRep* edge : tree->Edges()) {
       if (!IsValid(edge->btree(), shallow)) return false;
     }
diff --git a/absl/strings/internal/cord_rep_btree.h b/absl/strings/internal/cord_rep_btree.h
index 4209e512..be94b62e 100644
--- a/absl/strings/internal/cord_rep_btree.h
+++ b/absl/strings/internal/cord_rep_btree.h
@@ -32,6 +32,14 @@ namespace absl {
 ABSL_NAMESPACE_BEGIN
 namespace cord_internal {
 
+// `SetCordBtreeExhaustiveValidation()` can be set to force exhaustive
+// validation in debug assertions, and code that calls `IsValid()`
+// explicitly. By default, assertions should be relatively cheap and
+// AssertValid() can easily lead to O(n^2) complexity as recursive / full tree
+// validation is O(n).
+void SetCordBtreeExhaustiveValidation(bool do_exaustive_validation);
+bool IsCordBtreeExhaustiveValidationEnabled();
+
 class CordRepBtreeNavigator;
 
 // CordRepBtree is as the name implies a btree implementation of a Cordrep tree.
diff --git a/absl/strings/internal/cord_rep_btree_test.cc b/absl/strings/internal/cord_rep_btree_test.cc
index 9d6ce484..840acf9f 100644
--- a/absl/strings/internal/cord_rep_btree_test.cc
+++ b/absl/strings/internal/cord_rep_btree_test.cc
@@ -507,7 +507,7 @@ TEST_P(CordRepBtreeTest, AppendToTreeTwoDeep) {
   for (size_t i = max_cap * max_cap + 1; i < max_cap * max_cap * max_cap; ++i) {
     // Ref top level tree based on param.
     // Ref child node once every 16 iterations, and leaf node every 4
-    // iterrations which  which should not have an observable effect other than
+    // iterations which  which should not have an observable effect other than
     //  the node and/or the leaf below it being copied.
     refs.RefIf(shared(), tree);
     refs.RefIf(i % 16 == 0, tree->Edges().back());
@@ -568,7 +568,7 @@ TEST_P(CordRepBtreeTest, PrependToTreeTwoDeep) {
   for (size_t i = max_cap * max_cap + 1; i < max_cap * max_cap * max_cap; ++i) {
     // Ref top level tree based on param.
     // Ref child node once every 16 iterations, and leaf node every 4
-    // iterrations which  which should not have an observable effect other than
+    // iterations which  which should not have an observable effect other than
     //  the node and/or the leaf below it being copied.
     refs.RefIf(shared(), tree);
     refs.RefIf(i % 16 == 0, tree->Edges().back());
@@ -1355,9 +1355,9 @@ TEST(CordRepBtreeTest, AssertValid) {
 
 TEST(CordRepBtreeTest, CheckAssertValidShallowVsDeep) {
   // Restore exhaustive validation on any exit.
-  const bool exhaustive_validation = cord_btree_exhaustive_validation.load();
+  const bool exhaustive_validation = IsCordBtreeExhaustiveValidationEnabled();
   auto cleanup = absl::MakeCleanup([exhaustive_validation] {
-    cord_btree_exhaustive_validation.store(exhaustive_validation);
+    SetCordBtreeExhaustiveValidation(exhaustive_validation);
   });
 
   // Create a tree of at least 2 levels, and mess with the original flat, which
@@ -1372,7 +1372,7 @@ TEST(CordRepBtreeTest, CheckAssertValidShallowVsDeep) {
   }
   flat->length = 100;
 
-  cord_btree_exhaustive_validation.store(false);
+  SetCordBtreeExhaustiveValidation(false);
   EXPECT_FALSE(CordRepBtree::IsValid(tree));
   EXPECT_TRUE(CordRepBtree::IsValid(tree, true));
   EXPECT_FALSE(CordRepBtree::IsValid(tree, false));
@@ -1382,7 +1382,7 @@ TEST(CordRepBtreeTest, CheckAssertValidShallowVsDeep) {
   EXPECT_DEBUG_DEATH(CordRepBtree::AssertValid(tree, false), ".*");
 #endif
 
-  cord_btree_exhaustive_validation.store(true);
+  SetCordBtreeExhaustiveValidation(true);
   EXPECT_FALSE(CordRepBtree::IsValid(tree));
   EXPECT_FALSE(CordRepBtree::IsValid(tree, true));
   EXPECT_FALSE(CordRepBtree::IsValid(tree, false));
diff --git a/absl/strings/internal/cord_rep_consume.cc b/absl/strings/internal/cord_rep_consume.cc
index 20a55797..db7d4fef 100644
--- a/absl/strings/internal/cord_rep_consume.cc
+++ b/absl/strings/internal/cord_rep_consume.cc
@@ -42,7 +42,8 @@ CordRep* ClipSubstring(CordRepSubstring* substring) {
 
 }  // namespace
 
-void Consume(CordRep* rep, ConsumeFn consume_fn) {
+void Consume(CordRep* rep,
+             FunctionRef<void(CordRep*, size_t, size_t)> consume_fn) {
   size_t offset = 0;
   size_t length = rep->length;
 
@@ -53,8 +54,9 @@ void Consume(CordRep* rep, ConsumeFn consume_fn) {
   consume_fn(rep, offset, length);
 }
 
-void ReverseConsume(CordRep* rep, ConsumeFn consume_fn) {
-  return Consume(rep, std::move(consume_fn));
+void ReverseConsume(CordRep* rep,
+                    FunctionRef<void(CordRep*, size_t, size_t)> consume_fn) {
+  return Consume(rep, consume_fn);
 }
 
 }  // namespace cord_internal
diff --git a/absl/strings/internal/cord_rep_consume.h b/absl/strings/internal/cord_rep_consume.h
index d46fca2b..bece1874 100644
--- a/absl/strings/internal/cord_rep_consume.h
+++ b/absl/strings/internal/cord_rep_consume.h
@@ -24,11 +24,6 @@ namespace absl {
 ABSL_NAMESPACE_BEGIN
 namespace cord_internal {
 
-// Functor for the Consume() and ReverseConsume() functions:
-//   void ConsumeFunc(CordRep* rep, size_t offset, size_t length);
-// See the Consume() and ReverseConsume() function comments for documentation.
-using ConsumeFn = FunctionRef<void(CordRep*, size_t, size_t)>;
-
 // Consume() and ReverseConsume() consume CONCAT based trees and invoke the
 // provided functor with the contained nodes in the proper forward or reverse
 // order, which is used to convert CONCAT trees into other tree or cord data.
@@ -40,8 +35,10 @@ using ConsumeFn = FunctionRef<void(CordRep*, size_t, size_t)>;
 // violations, we can not 100% guarantee that all code respects 'new format'
 // settings and flags, so we need to be able to parse old data on the fly until
 // all old code is deprecated / no longer the default format.
-void Consume(CordRep* rep, ConsumeFn consume_fn);
-void ReverseConsume(CordRep* rep, ConsumeFn consume_fn);
+void Consume(CordRep* rep,
+             FunctionRef<void(CordRep*, size_t, size_t)> consume_fn);
+void ReverseConsume(CordRep* rep,
+                    FunctionRef<void(CordRep*, size_t, size_t)> consume_fn);
 
 }  // namespace cord_internal
 ABSL_NAMESPACE_END
diff --git a/absl/strings/internal/cord_rep_flat.h b/absl/strings/internal/cord_rep_flat.h
index e3e27fcd..27c4b21e 100644
--- a/absl/strings/internal/cord_rep_flat.h
+++ b/absl/strings/internal/cord_rep_flat.h
@@ -120,8 +120,16 @@ struct CordRepFlat : public CordRep {
     // Round size up so it matches a size we can exactly express in a tag.
     const size_t size = RoundUpForTag(len + kFlatOverhead);
     void* const raw_rep = ::operator new(size);
+    // GCC 13 has a false-positive -Wstringop-overflow warning here.
+    #if ABSL_INTERNAL_HAVE_MIN_GNUC_VERSION(13, 0)
+    #pragma GCC diagnostic push
+    #pragma GCC diagnostic ignored "-Wstringop-overflow"
+    #endif
     CordRepFlat* rep = new (raw_rep) CordRepFlat();
     rep->tag = AllocatedSizeToTag(size);
+    #if ABSL_INTERNAL_HAVE_MIN_GNUC_VERSION(13, 0)
+    #pragma GCC diagnostic pop
+    #endif
     return rep;
   }
 
diff --git a/absl/strings/internal/cord_rep_ring.h b/absl/strings/internal/cord_rep_ring.h
index 2000e21e..79a2fdb1 100644
--- a/absl/strings/internal/cord_rep_ring.h
+++ b/absl/strings/internal/cord_rep_ring.h
@@ -430,7 +430,7 @@ class CordRepRing : public CordRep {
   // capacity to satisfy `extra` extra nodes, and unref the old `rep` instance.
   //
   // If a new CordRepRing can not be allocated, or the new capacity would exceed
-  // the maxmimum capacity, then the input is consumed only, and an exception is
+  // the maximum capacity, then the input is consumed only, and an exception is
   // thrown.
   static CordRepRing* Mutable(CordRepRing* rep, size_t extra);
 
@@ -472,7 +472,7 @@ class CordRepRing : public CordRep {
   // Increases the data offset for entry `index` by `n`.
   void AddDataOffset(index_type index, size_t n);
 
-  // Descreases the length for entry `index` by `n`.
+  // Decreases the length for entry `index` by `n`.
   void SubLength(index_type index, size_t n);
 
   index_type head_;
diff --git a/absl/strings/internal/cordz_functions_test.cc b/absl/strings/internal/cordz_functions_test.cc
index 350623c1..b70a685e 100644
--- a/absl/strings/internal/cordz_functions_test.cc
+++ b/absl/strings/internal/cordz_functions_test.cc
@@ -38,7 +38,7 @@ TEST(CordzFunctionsTest, SampleRate) {
 }
 
 // Cordz is disabled when we don't have thread_local. All calls to
-// should_profile will return false when cordz is diabled, so we might want to
+// should_profile will return false when cordz is disabled, so we might want to
 // avoid those tests.
 #ifdef ABSL_INTERNAL_CORDZ_ENABLED
 
diff --git a/absl/strings/internal/cordz_handle.cc b/absl/strings/internal/cordz_handle.cc
index a73fefed..a7061dbe 100644
--- a/absl/strings/internal/cordz_handle.cc
+++ b/absl/strings/internal/cordz_handle.cc
@@ -16,34 +16,60 @@
 #include <atomic>
 
 #include "absl/base/internal/raw_logging.h"  // For ABSL_RAW_CHECK
-#include "absl/base/internal/spinlock.h"
+#include "absl/synchronization/mutex.h"
 
 namespace absl {
 ABSL_NAMESPACE_BEGIN
 namespace cord_internal {
 
-using ::absl::base_internal::SpinLockHolder;
+namespace {
 
-ABSL_CONST_INIT CordzHandle::Queue CordzHandle::global_queue_(absl::kConstInit);
+struct Queue {
+  Queue() = default;
+
+  absl::Mutex mutex;
+  std::atomic<CordzHandle*> dq_tail ABSL_GUARDED_BY(mutex){nullptr};
+
+  // Returns true if this delete queue is empty. This method does not acquire
+  // the lock, but does a 'load acquire' observation on the delete queue tail.
+  // It is used inside Delete() to check for the presence of a delete queue
+  // without holding the lock. The assumption is that the caller is in the
+  // state of 'being deleted', and can not be newly discovered by a concurrent
+  // 'being constructed' snapshot instance. Practically, this means that any
+  // such discovery (`find`, 'first' or 'next', etc) must have proper 'happens
+  // before / after' semantics and atomic fences.
+  bool IsEmpty() const ABSL_NO_THREAD_SAFETY_ANALYSIS {
+    return dq_tail.load(std::memory_order_acquire) == nullptr;
+  }
+};
+
+static Queue* GlobalQueue() {
+  static Queue* global_queue = new Queue;
+  return global_queue;
+}
+
+}  // namespace
 
 CordzHandle::CordzHandle(bool is_snapshot) : is_snapshot_(is_snapshot) {
+  Queue* global_queue = GlobalQueue();
   if (is_snapshot) {
-    SpinLockHolder lock(&queue_->mutex);
-    CordzHandle* dq_tail = queue_->dq_tail.load(std::memory_order_acquire);
+    MutexLock lock(&global_queue->mutex);
+    CordzHandle* dq_tail =
+        global_queue->dq_tail.load(std::memory_order_acquire);
     if (dq_tail != nullptr) {
       dq_prev_ = dq_tail;
       dq_tail->dq_next_ = this;
     }
-    queue_->dq_tail.store(this, std::memory_order_release);
+    global_queue->dq_tail.store(this, std::memory_order_release);
   }
 }
 
 CordzHandle::~CordzHandle() {
-  ODRCheck();
+  Queue* global_queue = GlobalQueue();
   if (is_snapshot_) {
     std::vector<CordzHandle*> to_delete;
     {
-      SpinLockHolder lock(&queue_->mutex);
+      MutexLock lock(&global_queue->mutex);
       CordzHandle* next = dq_next_;
       if (dq_prev_ == nullptr) {
         // We were head of the queue, delete every CordzHandle until we reach
@@ -59,7 +85,7 @@ CordzHandle::~CordzHandle() {
       if (next) {
         next->dq_prev_ = dq_prev_;
       } else {
-        queue_->dq_tail.store(dq_prev_, std::memory_order_release);
+        global_queue->dq_tail.store(dq_prev_, std::memory_order_release);
       }
     }
     for (CordzHandle* handle : to_delete) {
@@ -69,16 +95,15 @@ CordzHandle::~CordzHandle() {
 }
 
 bool CordzHandle::SafeToDelete() const {
-  return is_snapshot_ || queue_->IsEmpty();
+  return is_snapshot_ || GlobalQueue()->IsEmpty();
 }
 
 void CordzHandle::Delete(CordzHandle* handle) {
   assert(handle);
   if (handle) {
-    handle->ODRCheck();
-    Queue* const queue = handle->queue_;
+    Queue* const queue = GlobalQueue();
     if (!handle->SafeToDelete()) {
-      SpinLockHolder lock(&queue->mutex);
+      MutexLock lock(&queue->mutex);
       CordzHandle* dq_tail = queue->dq_tail.load(std::memory_order_acquire);
       if (dq_tail != nullptr) {
         handle->dq_prev_ = dq_tail;
@@ -93,8 +118,9 @@ void CordzHandle::Delete(CordzHandle* handle) {
 
 std::vector<const CordzHandle*> CordzHandle::DiagnosticsGetDeleteQueue() {
   std::vector<const CordzHandle*> handles;
-  SpinLockHolder lock(&global_queue_.mutex);
-  CordzHandle* dq_tail = global_queue_.dq_tail.load(std::memory_order_acquire);
+  Queue* global_queue = GlobalQueue();
+  MutexLock lock(&global_queue->mutex);
+  CordzHandle* dq_tail = global_queue->dq_tail.load(std::memory_order_acquire);
   for (const CordzHandle* p = dq_tail; p; p = p->dq_prev_) {
     handles.push_back(p);
   }
@@ -103,13 +129,13 @@ std::vector<const CordzHandle*> CordzHandle::DiagnosticsGetDeleteQueue() {
 
 bool CordzHandle::DiagnosticsHandleIsSafeToInspect(
     const CordzHandle* handle) const {
-  ODRCheck();
   if (!is_snapshot_) return false;
   if (handle == nullptr) return true;
   if (handle->is_snapshot_) return false;
   bool snapshot_found = false;
-  SpinLockHolder lock(&queue_->mutex);
-  for (const CordzHandle* p = queue_->dq_tail; p; p = p->dq_prev_) {
+  Queue* global_queue = GlobalQueue();
+  MutexLock lock(&global_queue->mutex);
+  for (const CordzHandle* p = global_queue->dq_tail; p; p = p->dq_prev_) {
     if (p == handle) return !snapshot_found;
     if (p == this) snapshot_found = true;
   }
@@ -119,13 +145,13 @@ bool CordzHandle::DiagnosticsHandleIsSafeToInspect(
 
 std::vector<const CordzHandle*>
 CordzHandle::DiagnosticsGetSafeToInspectDeletedHandles() {
-  ODRCheck();
   std::vector<const CordzHandle*> handles;
   if (!is_snapshot()) {
     return handles;
   }
 
-  SpinLockHolder lock(&queue_->mutex);
+  Queue* global_queue = GlobalQueue();
+  MutexLock lock(&global_queue->mutex);
   for (const CordzHandle* p = dq_next_; p != nullptr; p = p->dq_next_) {
     if (!p->is_snapshot()) {
       handles.push_back(p);
diff --git a/absl/strings/internal/cordz_handle.h b/absl/strings/internal/cordz_handle.h
index 3c800b43..08e3f0d3 100644
--- a/absl/strings/internal/cordz_handle.h
+++ b/absl/strings/internal/cordz_handle.h
@@ -20,8 +20,6 @@
 
 #include "absl/base/config.h"
 #include "absl/base/internal/raw_logging.h"
-#include "absl/base/internal/spinlock.h"
-#include "absl/synchronization/mutex.h"
 
 namespace absl {
 ABSL_NAMESPACE_BEGIN
@@ -34,7 +32,7 @@ namespace cord_internal {
 // has gained visibility into a CordzInfo object, that CordzInfo object will not
 // be deleted prematurely. This allows the profiler to inspect all CordzInfo
 // objects that are alive without needing to hold a global lock.
-class CordzHandle {
+class ABSL_DLL CordzHandle {
  public:
   CordzHandle() : CordzHandle(false) {}
 
@@ -79,37 +77,6 @@ class CordzHandle {
   virtual ~CordzHandle();
 
  private:
-  // Global queue data. CordzHandle stores a pointer to the global queue
-  // instance to harden against ODR violations.
-  struct Queue {
-    constexpr explicit Queue(absl::ConstInitType)
-        : mutex(absl::kConstInit,
-                absl::base_internal::SCHEDULE_COOPERATIVE_AND_KERNEL) {}
-
-    absl::base_internal::SpinLock mutex;
-    std::atomic<CordzHandle*> dq_tail ABSL_GUARDED_BY(mutex){nullptr};
-
-    // Returns true if this delete queue is empty. This method does not acquire
-    // the lock, but does a 'load acquire' observation on the delete queue tail.
-    // It is used inside Delete() to check for the presence of a delete queue
-    // without holding the lock. The assumption is that the caller is in the
-    // state of 'being deleted', and can not be newly discovered by a concurrent
-    // 'being constructed' snapshot instance. Practically, this means that any
-    // such discovery (`find`, 'first' or 'next', etc) must have proper 'happens
-    // before / after' semantics and atomic fences.
-    bool IsEmpty() const ABSL_NO_THREAD_SAFETY_ANALYSIS {
-      return dq_tail.load(std::memory_order_acquire) == nullptr;
-    }
-  };
-
-  void ODRCheck() const {
-#ifndef NDEBUG
-    ABSL_RAW_CHECK(queue_ == &global_queue_, "ODR violation in Cord");
-#endif
-  }
-
-  ABSL_CONST_INIT static Queue global_queue_;
-  Queue* const queue_ = &global_queue_;
   const bool is_snapshot_;
 
   // dq_prev_ and dq_next_ require the global queue mutex to be held.
diff --git a/absl/strings/internal/cordz_info.cc b/absl/strings/internal/cordz_info.cc
index 530f33be..515dfafb 100644
--- a/absl/strings/internal/cordz_info.cc
+++ b/absl/strings/internal/cordz_info.cc
@@ -26,6 +26,7 @@
 #include "absl/strings/internal/cordz_statistics.h"
 #include "absl/strings/internal/cordz_update_tracker.h"
 #include "absl/synchronization/mutex.h"
+#include "absl/time/clock.h"
 #include "absl/types/span.h"
 
 namespace absl {
@@ -53,7 +54,7 @@ namespace {
 // The top level node is treated specially: we assume the current thread
 // (typically called from the CordzHandler) to hold a reference purely to
 // perform a safe analysis, and not being part of the application. So we
-// substract 1 from the reference count of the top node to compute the
+// subtract 1 from the reference count of the top node to compute the
 // 'application fair share' excluding the reference of the current thread.
 //
 // An example of fair sharing, and why we multiply reference counts:
diff --git a/absl/strings/internal/cordz_sample_token.h b/absl/strings/internal/cordz_sample_token.h
index b58022c3..2a86bc3b 100644
--- a/absl/strings/internal/cordz_sample_token.h
+++ b/absl/strings/internal/cordz_sample_token.h
@@ -33,11 +33,11 @@ namespace cord_internal {
 //   ST1 <- CH1 <- CH2 <- ST2 <- CH3 <- global_delete_queue_tail
 //
 // This list tracks that CH1 and CH2 were created after ST1, so the thread
-// holding ST1 might have a referece to CH1, CH2, ST2, and CH3. However, ST2 was
-// created later, so the thread holding the ST2 token cannot have a reference to
-// ST1, CH1, or CH2. If ST1 is cleaned up first, that thread will delete ST1,
-// CH1, and CH2. If instead ST2 is cleaned up first, that thread will only
-// delete ST2.
+// holding ST1 might have a reference to CH1, CH2, ST2, and CH3. However, ST2
+// was created later, so the thread holding the ST2 token cannot have a
+// reference to ST1, CH1, or CH2. If ST1 is cleaned up first, that thread will
+// delete ST1, CH1, and CH2. If instead ST2 is cleaned up first, that thread
+// will only delete ST2.
 //
 // If ST1 is cleaned up first, the new list will be:
 //   ST2 <- CH3 <- global_delete_queue_tail
diff --git a/absl/strings/internal/damerau_levenshtein_distance_test.cc b/absl/strings/internal/damerau_levenshtein_distance_test.cc
index a342b7db..49dd105b 100644
--- a/absl/strings/internal/damerau_levenshtein_distance_test.cc
+++ b/absl/strings/internal/damerau_levenshtein_distance_test.cc
@@ -54,7 +54,7 @@ TEST(Distance, TestDistances) {
 }
 
 TEST(Distance, TestCutoff) {
-  // Returing cutoff + 1 if the value is larger than cutoff or string longer
+  // Returning cutoff + 1 if the value is larger than cutoff or string longer
   // than MAX_SIZE.
   EXPECT_THAT(CappedDamerauLevenshteinDistance("abcd", "a", 3), uint8_t{3});
   EXPECT_THAT(CappedDamerauLevenshteinDistance("abcd", "a", 2), uint8_t{3});
diff --git a/absl/strings/internal/escaping.cc b/absl/strings/internal/escaping.cc
index 8bd0890d..56a4cbed 100644
--- a/absl/strings/internal/escaping.cc
+++ b/absl/strings/internal/escaping.cc
@@ -21,9 +21,17 @@ namespace absl {
 ABSL_NAMESPACE_BEGIN
 namespace strings_internal {
 
+// The two strings below provide maps from normal 6-bit characters to their
+// base64-escaped equivalent.
+// For the inverse case, see kUn(WebSafe)Base64 in the external
+// escaping.cc.
 ABSL_CONST_INIT const char kBase64Chars[] =
     "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
 
+ABSL_CONST_INIT const char kWebSafeBase64Chars[] =
+    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_";
+
+
 size_t CalculateBase64EscapedLenInternal(size_t input_len, bool do_padding) {
   // Base64 encodes three bytes of input at a time. If the input is not
   // divisible by three, we pad as appropriate.
@@ -62,6 +70,21 @@ size_t CalculateBase64EscapedLenInternal(size_t input_len, bool do_padding) {
   return len;
 }
 
+// ----------------------------------------------------------------------
+//   Take the input in groups of 4 characters and turn each
+//   character into a code 0 to 63 thus:
+//           A-Z map to 0 to 25
+//           a-z map to 26 to 51
+//           0-9 map to 52 to 61
+//           +(- for WebSafe) maps to 62
+//           /(_ for WebSafe) maps to 63
+//   There will be four numbers, all less than 64 which can be represented
+//   by a 6 digit binary number (aaaaaa, bbbbbb, cccccc, dddddd respectively).
+//   Arrange the 6 digit binary numbers into three bytes as such:
+//   aaaaaabb bbbbcccc ccdddddd
+//   Equals signs (one or two) are used at the end of the encoded block to
+//   indicate that the text was not an integer multiple of three bytes long.
+// ----------------------------------------------------------------------
 size_t Base64EscapeInternal(const unsigned char* src, size_t szsrc, char* dest,
                             size_t szdest, const char* base64,
                             bool do_padding) {
diff --git a/absl/strings/internal/escaping.h b/absl/strings/internal/escaping.h
index b04033ff..2186f778 100644
--- a/absl/strings/internal/escaping.h
+++ b/absl/strings/internal/escaping.h
@@ -24,6 +24,7 @@ ABSL_NAMESPACE_BEGIN
 namespace strings_internal {
 
 ABSL_CONST_INIT extern const char kBase64Chars[];
+ABSL_CONST_INIT extern const char kWebSafeBase64Chars[];
 
 // Calculates the length of a Base64 encoding (RFC 4648) of a string of length
 // `input_len`, with or without padding per `do_padding`. Note that 'web-safe'
diff --git a/absl/strings/internal/memutil.cc b/absl/strings/internal/memutil.cc
index 44996a75..e2e7347c 100644
--- a/absl/strings/internal/memutil.cc
+++ b/absl/strings/internal/memutil.cc
@@ -16,6 +16,8 @@
 
 #include <cstdlib>
 
+#include "absl/strings/ascii.h"
+
 namespace absl {
 ABSL_NAMESPACE_BEGIN
 namespace strings_internal {
@@ -33,83 +35,6 @@ int memcasecmp(const char* s1, const char* s2, size_t len) {
   return 0;
 }
 
-char* memdup(const char* s, size_t slen) {
-  void* copy;
-  if ((copy = malloc(slen)) == nullptr) return nullptr;
-  memcpy(copy, s, slen);
-  return reinterpret_cast<char*>(copy);
-}
-
-char* memrchr(const char* s, int c, size_t slen) {
-  for (const char* e = s + slen - 1; e >= s; e--) {
-    if (*e == c) return const_cast<char*>(e);
-  }
-  return nullptr;
-}
-
-size_t memspn(const char* s, size_t slen, const char* accept) {
-  const char* p = s;
-  const char* spanp;
-  char c, sc;
-
-cont:
-  c = *p++;
-  if (slen-- == 0)
-    return static_cast<size_t>(p - 1 - s);
-  for (spanp = accept; (sc = *spanp++) != '\0';)
-    if (sc == c) goto cont;
-  return static_cast<size_t>(p - 1 - s);
-}
-
-size_t memcspn(const char* s, size_t slen, const char* reject) {
-  const char* p = s;
-  const char* spanp;
-  char c, sc;
-
-  while (slen-- != 0) {
-    c = *p++;
-    for (spanp = reject; (sc = *spanp++) != '\0';)
-      if (sc == c)
-        return static_cast<size_t>(p - 1 - s);
-  }
-  return static_cast<size_t>(p - s);
-}
-
-char* mempbrk(const char* s, size_t slen, const char* accept) {
-  const char* scanp;
-  int sc;
-
-  for (; slen; ++s, --slen) {
-    for (scanp = accept; (sc = *scanp++) != '\0';)
-      if (sc == *s) return const_cast<char*>(s);
-  }
-  return nullptr;
-}
-
-// This is significantly faster for case-sensitive matches with very
-// few possible matches.  See unit test for benchmarks.
-const char* memmatch(const char* phaystack, size_t haylen, const char* pneedle,
-                     size_t neelen) {
-  if (0 == neelen) {
-    return phaystack;  // even if haylen is 0
-  }
-  if (haylen < neelen) return nullptr;
-
-  const char* match;
-  const char* hayend = phaystack + haylen - neelen + 1;
-  // A static cast is used here to work around the fact that memchr returns
-  // a void* on Posix-compliant systems and const void* on Windows.
-  while (
-      (match = static_cast<const char*>(memchr(
-           phaystack, pneedle[0], static_cast<size_t>(hayend - phaystack))))) {
-    if (memcmp(match, pneedle, neelen) == 0)
-      return match;
-    else
-      phaystack = match + 1;
-  }
-  return nullptr;
-}
-
 }  // namespace strings_internal
 ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/strings/internal/memutil.h b/absl/strings/internal/memutil.h
index 9ad05358..b5911a01 100644
--- a/absl/strings/internal/memutil.h
+++ b/absl/strings/internal/memutil.h
@@ -14,51 +14,6 @@
 // limitations under the License.
 //
 
-// These routines provide mem versions of standard C string routines,
-// such as strpbrk.  They function exactly the same as the str versions,
-// so if you wonder what they are, replace the word "mem" by
-// "str" and check out the man page.  I could return void*, as the
-// strutil.h mem*() routines tend to do, but I return char* instead
-// since this is by far the most common way these functions are called.
-//
-// The difference between the mem and str versions is the mem version
-// takes a pointer and a length, rather than a '\0'-terminated string.
-// The memcase* routines defined here assume the locale is "C"
-// (they use absl::ascii_tolower instead of tolower).
-//
-// These routines are based on the BSD library.
-//
-// Here's a list of routines from string.h, and their mem analogues.
-// Functions in lowercase are defined in string.h; those in UPPERCASE
-// are defined here:
-//
-// strlen                  --
-// strcat strncat          MEMCAT
-// strcpy strncpy          memcpy
-// --                      memccpy   (very cool function, btw)
-// --                      memmove
-// --                      memset
-// strcmp strncmp          memcmp
-// strcasecmp strncasecmp  MEMCASECMP
-// strchr                  memchr
-// strcoll                 --
-// strxfrm                 --
-// strdup strndup          MEMDUP
-// strrchr                 MEMRCHR
-// strspn                  MEMSPN
-// strcspn                 MEMCSPN
-// strpbrk                 MEMPBRK
-// strstr                  MEMSTR MEMMEM
-// (g)strcasestr           MEMCASESTR MEMCASEMEM
-// strtok                  --
-// strprefix               MEMPREFIX      (strprefix is from strutil.h)
-// strcaseprefix           MEMCASEPREFIX  (strcaseprefix is from strutil.h)
-// strsuffix               MEMSUFFIX      (strsuffix is from strutil.h)
-// strcasesuffix           MEMCASESUFFIX  (strcasesuffix is from strutil.h)
-// --                      MEMIS
-// --                      MEMCASEIS
-// strcount                MEMCOUNT       (strcount is from strutil.h)
-
 #ifndef ABSL_STRINGS_INTERNAL_MEMUTIL_H_
 #define ABSL_STRINGS_INTERNAL_MEMUTIL_H_
 
@@ -72,74 +27,11 @@ namespace absl {
 ABSL_NAMESPACE_BEGIN
 namespace strings_internal {
 
-inline char* memcat(char* dest, size_t destlen, const char* src,
-                    size_t srclen) {
-  return reinterpret_cast<char*>(memcpy(dest + destlen, src, srclen));
-}
-
+// Performs a byte-by-byte comparison of `len` bytes of the strings `s1` and
+// `s2`, ignoring the case of the characters. It returns an integer less than,
+// equal to, or greater than zero if `s1` is found, respectively, to be less
+// than, to match, or be greater than `s2`.
 int memcasecmp(const char* s1, const char* s2, size_t len);
-char* memdup(const char* s, size_t slen);
-char* memrchr(const char* s, int c, size_t slen);
-size_t memspn(const char* s, size_t slen, const char* accept);
-size_t memcspn(const char* s, size_t slen, const char* reject);
-char* mempbrk(const char* s, size_t slen, const char* accept);
-
-// This is for internal use only.  Don't call this directly
-template <bool case_sensitive>
-const char* int_memmatch(const char* haystack, size_t haylen,
-                         const char* needle, size_t neelen) {
-  if (0 == neelen) {
-    return haystack;  // even if haylen is 0
-  }
-  const char* hayend = haystack + haylen;
-  const char* needlestart = needle;
-  const char* needleend = needlestart + neelen;
-
-  for (; haystack < hayend; ++haystack) {
-    char hay = case_sensitive
-                   ? *haystack
-                   : absl::ascii_tolower(static_cast<unsigned char>(*haystack));
-    char nee = case_sensitive
-                   ? *needle
-                   : absl::ascii_tolower(static_cast<unsigned char>(*needle));
-    if (hay == nee) {
-      if (++needle == needleend) {
-        return haystack + 1 - neelen;
-      }
-    } else if (needle != needlestart) {
-      // must back up haystack in case a prefix matched (find "aab" in "aaab")
-      haystack -= needle - needlestart;  // for loop will advance one more
-      needle = needlestart;
-    }
-  }
-  return nullptr;
-}
-
-// These are the guys you can call directly
-inline const char* memstr(const char* phaystack, size_t haylen,
-                          const char* pneedle) {
-  return int_memmatch<true>(phaystack, haylen, pneedle, strlen(pneedle));
-}
-
-inline const char* memcasestr(const char* phaystack, size_t haylen,
-                              const char* pneedle) {
-  return int_memmatch<false>(phaystack, haylen, pneedle, strlen(pneedle));
-}
-
-inline const char* memmem(const char* phaystack, size_t haylen,
-                          const char* pneedle, size_t needlelen) {
-  return int_memmatch<true>(phaystack, haylen, pneedle, needlelen);
-}
-
-inline const char* memcasemem(const char* phaystack, size_t haylen,
-                              const char* pneedle, size_t needlelen) {
-  return int_memmatch<false>(phaystack, haylen, pneedle, needlelen);
-}
-
-// This is significantly faster for case-sensitive matches with very
-// few possible matches.  See unit test for benchmarks.
-const char* memmatch(const char* phaystack, size_t haylen, const char* pneedle,
-                     size_t neelen);
 
 }  // namespace strings_internal
 ABSL_NAMESPACE_END
diff --git a/absl/strings/internal/memutil_benchmark.cc b/absl/strings/internal/memutil_benchmark.cc
index dc95c3e5..61e323a4 100644
--- a/absl/strings/internal/memutil_benchmark.cc
+++ b/absl/strings/internal/memutil_benchmark.cc
@@ -25,62 +25,6 @@
 // - an easy search: 'b'
 // - a medium search: 'ab'.  That means every letter is a possible match.
 // - a pathological search: 'aaaaaa.......aaaaab' (half as many a's as haytack)
-// We benchmark case-sensitive and case-insensitive versions of
-// three memmem implementations:
-// - memmem() from memutil.h
-// - search() from STL
-// - memmatch(), a custom implementation using memchr and memcmp.
-// Here are sample results:
-//
-// Run on (12 X 3800 MHz CPU s)
-// CPU Caches:
-//   L1 Data 32K (x6)
-//   L1 Instruction 32K (x6)
-//   L2 Unified 256K (x6)
-//   L3 Unified 15360K (x1)
-// ----------------------------------------------------------------
-// Benchmark                           Time          CPU Iterations
-// ----------------------------------------------------------------
-// BM_Memmem                        3583 ns      3582 ns     196469  2.59966GB/s
-// BM_MemmemMedium                 13743 ns     13742 ns      50901  693.986MB/s
-// BM_MemmemPathological        13695030 ns  13693977 ns         51  713.133kB/s
-// BM_Memcasemem                    3299 ns      3299 ns     212942  2.82309GB/s
-// BM_MemcasememMedium             16407 ns     16406 ns      42170  581.309MB/s
-// BM_MemcasememPathological    17267745 ns  17266030 ns         41  565.598kB/s
-// BM_Search                        1610 ns      1609 ns     431321  5.78672GB/s
-// BM_SearchMedium                 11111 ns     11110 ns      63001  858.414MB/s
-// BM_SearchPathological        12117390 ns  12116397 ns         58  805.984kB/s
-// BM_Searchcase                    3081 ns      3081 ns     229949  3.02313GB/s
-// BM_SearchcaseMedium             16003 ns     16001 ns      44170  595.998MB/s
-// BM_SearchcasePathological    15823413 ns  15821909 ns         44  617.222kB/s
-// BM_Memmatch                       197 ns       197 ns    3584225  47.2951GB/s
-// BM_MemmatchMedium               52333 ns     52329 ns      13280  182.244MB/s
-// BM_MemmatchPathological        659799 ns    659727 ns       1058  14.4556MB/s
-// BM_Memcasematch                  5460 ns      5460 ns     127606  1.70586GB/s
-// BM_MemcasematchMedium           32861 ns     32857 ns      21258  290.248MB/s
-// BM_MemcasematchPathological  15154243 ns  15153089 ns         46  644.464kB/s
-// BM_MemmemStartup                    5 ns         5 ns  150821500
-// BM_SearchStartup                    5 ns         5 ns  150644203
-// BM_MemmatchStartup                  7 ns         7 ns   97068802
-//
-// Conclusions:
-//
-// The following recommendations are based on the sample results above. However,
-// we have found that the performance of STL search can vary significantly
-// depending on compiler and standard library implementation. We recommend you
-// run the benchmarks for yourself on relevant platforms.
-//
-// If you need case-insensitive, STL search is slightly better than memmem for
-// all cases.
-//
-// Case-sensitive is more subtle:
-// Custom memmatch is _very_ fast at scanning, so if you have very few possible
-// matches in your haystack, that's the way to go. Performance drops
-// significantly with more matches.
-//
-// STL search is slightly faster than memmem in the medium and pathological
-// benchmarks. However, the performance of memmem is currently more dependable
-// across platforms and build configurations.
 
 namespace {
 
@@ -94,96 +38,10 @@ const char* MakeHaystack() {
 }
 const char* const kHaystack = MakeHaystack();
 
-void BM_Memmem(benchmark::State& state) {
-  for (auto _ : state) {
-    benchmark::DoNotOptimize(
-        absl::strings_internal::memmem(kHaystack, kHaystackSize, "b", 1));
-  }
-  state.SetBytesProcessed(kHaystackSize64 * state.iterations());
-}
-BENCHMARK(BM_Memmem);
-
-void BM_MemmemMedium(benchmark::State& state) {
-  for (auto _ : state) {
-    benchmark::DoNotOptimize(
-        absl::strings_internal::memmem(kHaystack, kHaystackSize, "ab", 2));
-  }
-  state.SetBytesProcessed(kHaystackSize64 * state.iterations());
-}
-BENCHMARK(BM_MemmemMedium);
-
-void BM_MemmemPathological(benchmark::State& state) {
-  for (auto _ : state) {
-    benchmark::DoNotOptimize(absl::strings_internal::memmem(
-        kHaystack, kHaystackSize, kHaystack + kHaystackSize / 2,
-        kHaystackSize - kHaystackSize / 2));
-  }
-  state.SetBytesProcessed(kHaystackSize64 * state.iterations());
-}
-BENCHMARK(BM_MemmemPathological);
-
-void BM_Memcasemem(benchmark::State& state) {
-  for (auto _ : state) {
-    benchmark::DoNotOptimize(
-        absl::strings_internal::memcasemem(kHaystack, kHaystackSize, "b", 1));
-  }
-  state.SetBytesProcessed(kHaystackSize64 * state.iterations());
-}
-BENCHMARK(BM_Memcasemem);
-
-void BM_MemcasememMedium(benchmark::State& state) {
-  for (auto _ : state) {
-    benchmark::DoNotOptimize(
-        absl::strings_internal::memcasemem(kHaystack, kHaystackSize, "ab", 2));
-  }
-  state.SetBytesProcessed(kHaystackSize64 * state.iterations());
-}
-BENCHMARK(BM_MemcasememMedium);
-
-void BM_MemcasememPathological(benchmark::State& state) {
-  for (auto _ : state) {
-    benchmark::DoNotOptimize(absl::strings_internal::memcasemem(
-        kHaystack, kHaystackSize, kHaystack + kHaystackSize / 2,
-        kHaystackSize - kHaystackSize / 2));
-  }
-  state.SetBytesProcessed(kHaystackSize64 * state.iterations());
-}
-BENCHMARK(BM_MemcasememPathological);
-
 bool case_eq(const char a, const char b) {
   return absl::ascii_tolower(a) == absl::ascii_tolower(b);
 }
 
-void BM_Search(benchmark::State& state) {
-  for (auto _ : state) {
-    benchmark::DoNotOptimize(std::search(kHaystack, kHaystack + kHaystackSize,
-                                         kHaystack + kHaystackSize - 1,
-                                         kHaystack + kHaystackSize));
-  }
-  state.SetBytesProcessed(kHaystackSize64 * state.iterations());
-}
-BENCHMARK(BM_Search);
-
-void BM_SearchMedium(benchmark::State& state) {
-  for (auto _ : state) {
-    benchmark::DoNotOptimize(std::search(kHaystack, kHaystack + kHaystackSize,
-                                         kHaystack + kHaystackSize - 2,
-                                         kHaystack + kHaystackSize));
-  }
-  state.SetBytesProcessed(kHaystackSize64 * state.iterations());
-}
-BENCHMARK(BM_SearchMedium);
-
-void BM_SearchPathological(benchmark::State& state) {
-  for (auto _ : state) {
-    benchmark::DoNotOptimize(std::search(kHaystack, kHaystack + kHaystackSize,
-                                         kHaystack + kHaystackSize / 2,
-                                         kHaystack + kHaystackSize));
-  }
-  state.SetBytesProcessed(kHaystackSize64 * state.iterations());
-}
-BENCHMARK(BM_SearchPathological);
-
 void BM_Searchcase(benchmark::State& state) {
   for (auto _ : state) {
     benchmark::DoNotOptimize(std::search(kHaystack, kHaystack + kHaystackSize,
@@ -241,34 +99,6 @@ const char* memcasematch(const char* phaystack, size_t haylen,
   return nullptr;
 }
 
-void BM_Memmatch(benchmark::State& state) {
-  for (auto _ : state) {
-    benchmark::DoNotOptimize(
-        absl::strings_internal::memmatch(kHaystack, kHaystackSize, "b", 1));
-  }
-  state.SetBytesProcessed(kHaystackSize64 * state.iterations());
-}
-BENCHMARK(BM_Memmatch);
-
-void BM_MemmatchMedium(benchmark::State& state) {
-  for (auto _ : state) {
-    benchmark::DoNotOptimize(
-        absl::strings_internal::memmatch(kHaystack, kHaystackSize, "ab", 2));
-  }
-  state.SetBytesProcessed(kHaystackSize64 * state.iterations());
-}
-BENCHMARK(BM_MemmatchMedium);
-
-void BM_MemmatchPathological(benchmark::State& state) {
-  for (auto _ : state) {
-    benchmark::DoNotOptimize(absl::strings_internal::memmatch(
-        kHaystack, kHaystackSize, kHaystack + kHaystackSize / 2,
-        kHaystackSize - kHaystackSize / 2));
-  }
-  state.SetBytesProcessed(kHaystackSize64 * state.iterations());
-}
-BENCHMARK(BM_MemmatchPathological);
-
 void BM_Memcasematch(benchmark::State& state) {
   for (auto _ : state) {
     benchmark::DoNotOptimize(memcasematch(kHaystack, kHaystackSize, "b", 1));
@@ -295,29 +125,4 @@ void BM_MemcasematchPathological(benchmark::State& state) {
 }
 BENCHMARK(BM_MemcasematchPathological);
 
-void BM_MemmemStartup(benchmark::State& state) {
-  for (auto _ : state) {
-    benchmark::DoNotOptimize(absl::strings_internal::memmem(
-        kHaystack + kHaystackSize - 10, 10, kHaystack + kHaystackSize - 1, 1));
-  }
-}
-BENCHMARK(BM_MemmemStartup);
-
-void BM_SearchStartup(benchmark::State& state) {
-  for (auto _ : state) {
-    benchmark::DoNotOptimize(
-        std::search(kHaystack + kHaystackSize - 10, kHaystack + kHaystackSize,
-                    kHaystack + kHaystackSize - 1, kHaystack + kHaystackSize));
-  }
-}
-BENCHMARK(BM_SearchStartup);
-
-void BM_MemmatchStartup(benchmark::State& state) {
-  for (auto _ : state) {
-    benchmark::DoNotOptimize(absl::strings_internal::memmatch(
-        kHaystack + kHaystackSize - 10, 10, kHaystack + kHaystackSize - 1, 1));
-  }
-}
-BENCHMARK(BM_MemmatchStartup);
-
 }  // namespace
diff --git a/absl/strings/internal/memutil_test.cc b/absl/strings/internal/memutil_test.cc
index d8681ddf..277be2c4 100644
--- a/absl/strings/internal/memutil_test.cc
+++ b/absl/strings/internal/memutil_test.cc
@@ -19,42 +19,12 @@
 #include <cstdlib>
 
 #include "gtest/gtest.h"
-#include "absl/strings/ascii.h"
 
 namespace {
 
-static char* memcasechr(const char* s, int c, size_t slen) {
-  c = absl::ascii_tolower(c);
-  for (; slen; ++s, --slen) {
-    if (absl::ascii_tolower(*s) == c) return const_cast<char*>(s);
-  }
-  return nullptr;
-}
-
-static const char* memcasematch(const char* phaystack, size_t haylen,
-                                const char* pneedle, size_t neelen) {
-  if (0 == neelen) {
-    return phaystack;  // even if haylen is 0
-  }
-  if (haylen < neelen) return nullptr;
-
-  const char* match;
-  const char* hayend = phaystack + haylen - neelen + 1;
-  while ((match = static_cast<char*>(
-              memcasechr(phaystack, pneedle[0], hayend - phaystack)))) {
-    if (absl::strings_internal::memcasecmp(match, pneedle, neelen) == 0)
-      return match;
-    else
-      phaystack = match + 1;
-  }
-  return nullptr;
-}
-
-TEST(MemUtilTest, AllTests) {
+TEST(MemUtil, memcasecmp) {
   // check memutil functions
-  char a[1000];
-  absl::strings_internal::memcat(a, 0, "hello", sizeof("hello") - 1);
-  absl::strings_internal::memcat(a, 5, " there", sizeof(" there") - 1);
+  const char a[] = "hello there";
 
   EXPECT_EQ(absl::strings_internal::memcasecmp(a, "heLLO there",
                                                sizeof("hello there") - 1),
@@ -66,114 +36,6 @@ TEST(MemUtilTest, AllTests) {
                                                sizeof("hello there") - 2),
             0);
   EXPECT_EQ(absl::strings_internal::memcasecmp(a, "whatever", 0), 0);
-
-  char* p = absl::strings_internal::memdup("hello", 5);
-  free(p);
-
-  p = absl::strings_internal::memrchr("hello there", 'e',
-                                      sizeof("hello there") - 1);
-  EXPECT_TRUE(p && p[-1] == 'r');
-  p = absl::strings_internal::memrchr("hello there", 'e',
-                                      sizeof("hello there") - 2);
-  EXPECT_TRUE(p && p[-1] == 'h');
-  p = absl::strings_internal::memrchr("hello there", 'u',
-                                      sizeof("hello there") - 1);
-  EXPECT_TRUE(p == nullptr);
-
-  int len = absl::strings_internal::memspn("hello there",
-                                           sizeof("hello there") - 1, "hole");
-  EXPECT_EQ(len, sizeof("hello") - 1);
-  len = absl::strings_internal::memspn("hello there", sizeof("hello there") - 1,
-                                       "u");
-  EXPECT_EQ(len, 0);
-  len = absl::strings_internal::memspn("hello there", sizeof("hello there") - 1,
-                                       "");
-  EXPECT_EQ(len, 0);
-  len = absl::strings_internal::memspn("hello there", sizeof("hello there") - 1,
-                                       "trole h");
-  EXPECT_EQ(len, sizeof("hello there") - 1);
-  len = absl::strings_internal::memspn("hello there!",
-                                       sizeof("hello there!") - 1, "trole h");
-  EXPECT_EQ(len, sizeof("hello there") - 1);
-  len = absl::strings_internal::memspn("hello there!",
-                                       sizeof("hello there!") - 2, "trole h!");
-  EXPECT_EQ(len, sizeof("hello there!") - 2);
-
-  len = absl::strings_internal::memcspn("hello there",
-                                        sizeof("hello there") - 1, "leho");
-  EXPECT_EQ(len, 0);
-  len = absl::strings_internal::memcspn("hello there",
-                                        sizeof("hello there") - 1, "u");
-  EXPECT_EQ(len, sizeof("hello there") - 1);
-  len = absl::strings_internal::memcspn("hello there",
-                                        sizeof("hello there") - 1, "");
-  EXPECT_EQ(len, sizeof("hello there") - 1);
-  len = absl::strings_internal::memcspn("hello there",
-                                        sizeof("hello there") - 1, " ");
-  EXPECT_EQ(len, 5);
-
-  p = absl::strings_internal::mempbrk("hello there", sizeof("hello there") - 1,
-                                      "leho");
-  EXPECT_TRUE(p && p[1] == 'e' && p[2] == 'l');
-  p = absl::strings_internal::mempbrk("hello there", sizeof("hello there") - 1,
-                                      "nu");
-  EXPECT_TRUE(p == nullptr);
-  p = absl::strings_internal::mempbrk("hello there!",
-                                      sizeof("hello there!") - 2, "!");
-  EXPECT_TRUE(p == nullptr);
-  p = absl::strings_internal::mempbrk("hello there", sizeof("hello there") - 1,
-                                      " t ");
-  EXPECT_TRUE(p && p[-1] == 'o' && p[1] == 't');
-
-  {
-    const char kHaystack[] = "0123456789";
-    EXPECT_EQ(absl::strings_internal::memmem(kHaystack, 0, "", 0), kHaystack);
-    EXPECT_EQ(absl::strings_internal::memmem(kHaystack, 10, "012", 3),
-              kHaystack);
-    EXPECT_EQ(absl::strings_internal::memmem(kHaystack, 10, "0xx", 1),
-              kHaystack);
-    EXPECT_EQ(absl::strings_internal::memmem(kHaystack, 10, "789", 3),
-              kHaystack + 7);
-    EXPECT_EQ(absl::strings_internal::memmem(kHaystack, 10, "9xx", 1),
-              kHaystack + 9);
-    EXPECT_TRUE(absl::strings_internal::memmem(kHaystack, 10, "9xx", 3) ==
-                nullptr);
-    EXPECT_TRUE(absl::strings_internal::memmem(kHaystack, 10, "xxx", 1) ==
-                nullptr);
-  }
-  {
-    const char kHaystack[] = "aBcDeFgHiJ";
-    EXPECT_EQ(absl::strings_internal::memcasemem(kHaystack, 0, "", 0),
-              kHaystack);
-    EXPECT_EQ(absl::strings_internal::memcasemem(kHaystack, 10, "Abc", 3),
-              kHaystack);
-    EXPECT_EQ(absl::strings_internal::memcasemem(kHaystack, 10, "Axx", 1),
-              kHaystack);
-    EXPECT_EQ(absl::strings_internal::memcasemem(kHaystack, 10, "hIj", 3),
-              kHaystack + 7);
-    EXPECT_EQ(absl::strings_internal::memcasemem(kHaystack, 10, "jxx", 1),
-              kHaystack + 9);
-    EXPECT_TRUE(absl::strings_internal::memcasemem(kHaystack, 10, "jxx", 3) ==
-                nullptr);
-    EXPECT_TRUE(absl::strings_internal::memcasemem(kHaystack, 10, "xxx", 1) ==
-                nullptr);
-  }
-  {
-    const char kHaystack[] = "0123456789";
-    EXPECT_EQ(absl::strings_internal::memmatch(kHaystack, 0, "", 0), kHaystack);
-    EXPECT_EQ(absl::strings_internal::memmatch(kHaystack, 10, "012", 3),
-              kHaystack);
-    EXPECT_EQ(absl::strings_internal::memmatch(kHaystack, 10, "0xx", 1),
-              kHaystack);
-    EXPECT_EQ(absl::strings_internal::memmatch(kHaystack, 10, "789", 3),
-              kHaystack + 7);
-    EXPECT_EQ(absl::strings_internal::memmatch(kHaystack, 10, "9xx", 1),
-              kHaystack + 9);
-    EXPECT_TRUE(absl::strings_internal::memmatch(kHaystack, 10, "9xx", 3) ==
-                nullptr);
-    EXPECT_TRUE(absl::strings_internal::memmatch(kHaystack, 10, "xxx", 1) ==
-                nullptr);
-  }
 }
 
 }  // namespace
diff --git a/absl/strings/internal/stl_type_traits.h b/absl/strings/internal/stl_type_traits.h
index 6035ca45..e50468b0 100644
--- a/absl/strings/internal/stl_type_traits.h
+++ b/absl/strings/internal/stl_type_traits.h
@@ -13,7 +13,7 @@
 // limitations under the License.
 //
 
-// Thie file provides the IsStrictlyBaseOfAndConvertibleToSTLContainer type
+// The file provides the IsStrictlyBaseOfAndConvertibleToSTLContainer type
 // trait metafunction to assist in working with the _GLIBCXX_DEBUG debug
 // wrappers of STL containers.
 //
diff --git a/absl/strings/internal/str_format/arg.cc b/absl/strings/internal/str_format/arg.cc
index 018dd052..c0a9a28e 100644
--- a/absl/strings/internal/str_format/arg.cc
+++ b/absl/strings/internal/str_format/arg.cc
@@ -106,7 +106,7 @@ class IntDigits {
     char *p = storage_ + sizeof(storage_);
     do {
       p -= 2;
-      numbers_internal::PutTwoDigits(static_cast<size_t>(v % 100), p);
+      numbers_internal::PutTwoDigits(static_cast<uint32_t>(v % 100), p);
       v /= 100;
     } while (v);
     if (p[0] == '0') {
@@ -278,24 +278,6 @@ bool ConvertIntImplInnerSlow(const IntDigits &as_digits,
   return true;
 }
 
-template <typename T,
-          typename std::enable_if<(std::is_integral<T>::value &&
-                                   std::is_signed<T>::value) ||
-                                      std::is_same<T, int128>::value,
-                                  int>::type = 0>
-constexpr auto ConvertV(T) {
-  return FormatConversionCharInternal::d;
-}
-
-template <typename T,
-          typename std::enable_if<(std::is_integral<T>::value &&
-                                   std::is_unsigned<T>::value) ||
-                                      std::is_same<T, uint128>::value,
-                                  int>::type = 0>
-constexpr auto ConvertV(T) {
-  return FormatConversionCharInternal::u;
-}
-
 template <typename T>
 bool ConvertFloatArg(T v, FormatConversionSpecImpl conv, FormatSinkImpl *sink) {
   if (conv.conversion_char() == FormatConversionCharInternal::v) {
@@ -332,10 +314,6 @@ bool ConvertIntArg(T v, FormatConversionSpecImpl conv, FormatSinkImpl *sink) {
   using U = typename MakeUnsigned<T>::type;
   IntDigits as_digits;
 
-  if (conv.conversion_char() == FormatConversionCharInternal::v) {
-    conv.set_conversion_char(ConvertV(T{}));
-  }
-
   // This odd casting is due to a bug in -Wswitch behavior in gcc49 which causes
   // it to complain about a switch/case type mismatch, even though both are
   // FormatConverionChar.  Likely this is because at this point
@@ -361,6 +339,7 @@ bool ConvertIntArg(T v, FormatConversionSpecImpl conv, FormatSinkImpl *sink) {
 
     case static_cast<uint8_t>(FormatConversionCharInternal::d):
     case static_cast<uint8_t>(FormatConversionCharInternal::i):
+    case static_cast<uint8_t>(FormatConversionCharInternal::v):
       as_digits.PrintAsDec(v);
       break;
 
@@ -482,18 +461,18 @@ CharConvertResult FormatConvertImpl(char v, const FormatConversionSpecImpl conv,
                                     FormatSinkImpl *sink) {
   return {ConvertIntArg(v, conv, sink)};
 }
-CharConvertResult FormatConvertImpl(signed char v,
-                                    const FormatConversionSpecImpl conv,
-                                    FormatSinkImpl *sink) {
+
+// ==================== Ints ====================
+IntegralConvertResult FormatConvertImpl(signed char v,
+                                        const FormatConversionSpecImpl conv,
+                                        FormatSinkImpl *sink) {
   return {ConvertIntArg(v, conv, sink)};
 }
-CharConvertResult FormatConvertImpl(unsigned char v,
-                                    const FormatConversionSpecImpl conv,
-                                    FormatSinkImpl *sink) {
+IntegralConvertResult FormatConvertImpl(unsigned char v,
+                                        const FormatConversionSpecImpl conv,
+                                        FormatSinkImpl *sink) {
   return {ConvertIntArg(v, conv, sink)};
 }
-
-// ==================== Ints ====================
 IntegralConvertResult FormatConvertImpl(short v,  // NOLINT
                                         const FormatConversionSpecImpl conv,
                                         FormatSinkImpl *sink) {
diff --git a/absl/strings/internal/str_format/arg.h b/absl/strings/internal/str_format/arg.h
index e4b16628..3ce30feb 100644
--- a/absl/strings/internal/str_format/arg.h
+++ b/absl/strings/internal/str_format/arg.h
@@ -279,14 +279,14 @@ FloatingConvertResult FormatConvertImpl(long double v,
 // Chars.
 CharConvertResult FormatConvertImpl(char v, FormatConversionSpecImpl conv,
                                     FormatSinkImpl* sink);
-CharConvertResult FormatConvertImpl(signed char v,
-                                    FormatConversionSpecImpl conv,
-                                    FormatSinkImpl* sink);
-CharConvertResult FormatConvertImpl(unsigned char v,
-                                    FormatConversionSpecImpl conv,
-                                    FormatSinkImpl* sink);
 
 // Ints.
+IntegralConvertResult FormatConvertImpl(signed char v,
+                                        FormatConversionSpecImpl conv,
+                                        FormatSinkImpl* sink);
+IntegralConvertResult FormatConvertImpl(unsigned char v,
+                                        FormatConversionSpecImpl conv,
+                                        FormatSinkImpl* sink);
 IntegralConvertResult FormatConvertImpl(short v,  // NOLINT
                                         FormatConversionSpecImpl conv,
                                         FormatSinkImpl* sink);
@@ -441,7 +441,7 @@ class FormatArgImpl {
   // For everything else:
   //   - Decay char* and char arrays into `const char*`
   //   - Decay any other pointer to `const void*`
-  //   - Decay all enums to their underlying type.
+  //   - Decay all enums to the integral promotion of their underlying type.
   //   - Decay function pointers to void*.
   template <typename T, typename = void>
   struct DecayType {
@@ -461,7 +461,7 @@ class FormatArgImpl {
                        !str_format_internal::HasUserDefinedConvert<T>::value &&
                        !strings_internal::HasAbslStringify<T>::value &&
                        std::is_enum<T>::value>::type> {
-    using type = typename std::underlying_type<T>::type;
+    using type = decltype(+typename std::underlying_type<T>::type());
   };
 
  public:
diff --git a/absl/strings/internal/str_format/bind.h b/absl/strings/internal/str_format/bind.h
index b73c5028..5e2a43d5 100644
--- a/absl/strings/internal/str_format/bind.h
+++ b/absl/strings/internal/str_format/bind.h
@@ -21,6 +21,7 @@
 #include <string>
 
 #include "absl/base/port.h"
+#include "absl/container/inlined_vector.h"
 #include "absl/strings/internal/str_format/arg.h"
 #include "absl/strings/internal/str_format/checker.h"
 #include "absl/strings/internal/str_format/parser.h"
@@ -177,17 +178,7 @@ class Streamable {
  public:
   Streamable(const UntypedFormatSpecImpl& format,
              absl::Span<const FormatArgImpl> args)
-      : format_(format) {
-    if (args.size() <= ABSL_ARRAYSIZE(few_args_)) {
-      for (size_t i = 0; i < args.size(); ++i) {
-        few_args_[i] = args[i];
-      }
-      args_ = absl::MakeSpan(few_args_, args.size());
-    } else {
-      many_args_.assign(args.begin(), args.end());
-      args_ = many_args_;
-    }
-  }
+      : format_(format), args_(args.begin(), args.end()) {}
 
   std::ostream& Print(std::ostream& os) const;
 
@@ -197,12 +188,7 @@ class Streamable {
 
  private:
   const UntypedFormatSpecImpl& format_;
-  absl::Span<const FormatArgImpl> args_;
-  // if args_.size() is 4 or less:
-  FormatArgImpl few_args_[4] = {FormatArgImpl(0), FormatArgImpl(0),
-                                FormatArgImpl(0), FormatArgImpl(0)};
-  // if args_.size() is more than 4:
-  std::vector<FormatArgImpl> many_args_;
+  absl::InlinedVector<FormatArgImpl, 4> args_;
 };
 
 // for testing
@@ -211,8 +197,7 @@ std::string Summarize(UntypedFormatSpecImpl format,
 bool BindWithPack(const UnboundConversion* props,
                   absl::Span<const FormatArgImpl> pack, BoundConversion* bound);
 
-bool FormatUntyped(FormatRawSinkImpl raw_sink,
-                   UntypedFormatSpecImpl format,
+bool FormatUntyped(FormatRawSinkImpl raw_sink, UntypedFormatSpecImpl format,
                    absl::Span<const FormatArgImpl> args);
 
 std::string& AppendPack(std::string* out, UntypedFormatSpecImpl format,
@@ -231,7 +216,7 @@ int SnprintF(char* output, size_t size, UntypedFormatSpecImpl format,
 template <typename T>
 class StreamedWrapper {
  public:
-  explicit StreamedWrapper(const T& v) : v_(v) { }
+  explicit StreamedWrapper(const T& v) : v_(v) {}
 
  private:
   template <typename S>
diff --git a/absl/strings/internal/str_format/constexpr_parser.h b/absl/strings/internal/str_format/constexpr_parser.h
index 3dc1776b..b70a16e4 100644
--- a/absl/strings/internal/str_format/constexpr_parser.h
+++ b/absl/strings/internal/str_format/constexpr_parser.h
@@ -323,6 +323,7 @@ constexpr const char* ConsumeConversion(const char* pos, const char* const end,
     if (ABSL_PREDICT_FALSE(c == 'v')) return nullptr;
     if (ABSL_PREDICT_FALSE(!tag.is_conv())) return nullptr;
   }
+#undef ABSL_FORMAT_PARSER_INTERNAL_GET_CHAR
 
   assert(CheckFastPathSetting(*conv));
   (void)(&CheckFastPathSetting);
diff --git a/absl/strings/internal/str_format/convert_test.cc b/absl/strings/internal/str_format/convert_test.cc
index 300612b7..16ff9879 100644
--- a/absl/strings/internal/str_format/convert_test.cc
+++ b/absl/strings/internal/str_format/convert_test.cc
@@ -26,6 +26,7 @@
 #include "gtest/gtest.h"
 #include "absl/base/attributes.h"
 #include "absl/base/internal/raw_logging.h"
+#include "absl/log/log.h"
 #include "absl/strings/internal/str_format/bind.h"
 #include "absl/strings/match.h"
 #include "absl/types/optional.h"
@@ -264,7 +265,7 @@ MATCHER_P(MatchesPointerString, ptr, "") {
   }
   void* parsed = nullptr;
   if (sscanf(arg.c_str(), "%p", &parsed) != 1) {
-    ABSL_RAW_LOG(FATAL, "Could not parse %s", arg.c_str());
+    LOG(FATAL) << "Could not parse " << arg;
   }
   return ptr == parsed;
 }
@@ -1241,9 +1242,9 @@ TEST_F(FormatConvertTest, GlibcHasCorrectTraits) {
   const NativePrintfTraits &native_traits = VerifyNativeImplementation();
   // If one of the following tests break then it is either because the above PP
   // macro guards failed to exclude a new platform (likely) or because something
-  // has changed in the implemention of glibc sprintf float formatting behavior.
-  // If the latter, then the code that computes these flags needs to be
-  // revisited and/or possibly the StrFormat implementation.
+  // has changed in the implementation of glibc sprintf float formatting
+  // behavior.  If the latter, then the code that computes these flags needs to
+  // be revisited and/or possibly the StrFormat implementation.
   EXPECT_TRUE(native_traits.hex_float_has_glibc_rounding);
   EXPECT_TRUE(native_traits.hex_float_prefers_denormal_repr);
   EXPECT_TRUE(
diff --git a/absl/strings/internal/str_format/extension.h b/absl/strings/internal/str_format/extension.h
index 603bd49d..8de42d2c 100644
--- a/absl/strings/internal/str_format/extension.h
+++ b/absl/strings/internal/str_format/extension.h
@@ -273,7 +273,7 @@ struct FormatConversionSpecImplFriend;
 
 class FormatConversionSpecImpl {
  public:
-  // Width and precison are not specified, no flags are set.
+  // Width and precision are not specified, no flags are set.
   bool is_basic() const { return flags_ == Flags::kBasic; }
   bool has_left_flag() const { return FlagsContains(flags_, Flags::kLeft); }
   bool has_show_pos_flag() const {
diff --git a/absl/strings/internal/str_format/float_conversion.cc b/absl/strings/internal/str_format/float_conversion.cc
index 8e497852..8edf520d 100644
--- a/absl/strings/internal/str_format/float_conversion.cc
+++ b/absl/strings/internal/str_format/float_conversion.cc
@@ -711,12 +711,12 @@ bool IncrementNibble(size_t nibble_index, Int* n) {
   constexpr size_t kShift = sizeof(Int) * 8 - 1;
   constexpr size_t kNumNibbles = sizeof(Int) * 8 / 4;
   Int before = *n >> kShift;
-  // Here we essentially want to take the number 1 and move it into the requsted
-  // nibble, then add it to *n to effectively increment the nibble. However,
-  // ASan will complain if we try to shift the 1 beyond the limits of the Int,
-  // i.e., if the nibble_index is out of range. So therefore we check for this
-  // and if we are out of range we just add 0 which leaves *n unchanged, which
-  // seems like the reasonable thing to do in that case.
+  // Here we essentially want to take the number 1 and move it into the
+  // requested nibble, then add it to *n to effectively increment the nibble.
+  // However, ASan will complain if we try to shift the 1 beyond the limits of
+  // the Int, i.e., if the nibble_index is out of range. So therefore we check
+  // for this and if we are out of range we just add 0 which leaves *n
+  // unchanged, which seems like the reasonable thing to do in that case.
   *n += ((nibble_index >= kNumNibbles)
              ? 0
              : (Int{1} << static_cast<int>(nibble_index * 4)));
@@ -937,7 +937,7 @@ void FormatA(const HexFloatTypeParams float_traits, Int mantissa, int exp,
 
   // =============== Exponent ==================
   constexpr size_t kBufSizeForExpDecRepr =
-      numbers_internal::kFastToBufferSize  // requred for FastIntToBuffer
+      numbers_internal::kFastToBufferSize  // required for FastIntToBuffer
       + 1                                  // 'p' or 'P'
       + 1;                                 // '+' or '-'
   char exp_buffer[kBufSizeForExpDecRepr];
@@ -1015,7 +1015,7 @@ struct Buffer {
     --end;
   }
 
-  char &back() {
+  char &back() const {
     assert(begin < end);
     return end[-1];
   }
@@ -1102,7 +1102,7 @@ void PrintExponent(int exp, char e, Buffer *out) {
 template <typename Float, typename Int>
 constexpr bool CanFitMantissa() {
   return
-#if defined(__clang__) && !defined(__SSE3__)
+#if defined(__clang__) && (__clang_major__ < 9) && !defined(__SSE3__)
       // Workaround for clang bug: https://bugs.llvm.org/show_bug.cgi?id=38289
       // Casting from long double to uint64_t is miscompiled and drops bits.
       (!std::is_same<Float, long double>::value ||
diff --git a/absl/strings/internal/str_split_internal.h b/absl/strings/internal/str_split_internal.h
index 35edf3aa..081ad85a 100644
--- a/absl/strings/internal/str_split_internal.h
+++ b/absl/strings/internal/str_split_internal.h
@@ -235,6 +235,24 @@ struct SplitterIsConvertibleTo
           HasMappedType<C>::value> {
 };
 
+template <typename StringType, typename Container, typename = void>
+struct ShouldUseLifetimeBound : std::false_type {};
+
+template <typename StringType, typename Container>
+struct ShouldUseLifetimeBound<
+    StringType, Container,
+    std::enable_if_t<
+        std::is_same<StringType, std::string>::value &&
+        std::is_same<typename Container::value_type, absl::string_view>::value>>
+    : std::true_type {};
+
+template <typename StringType, typename First, typename Second>
+using ShouldUseLifetimeBoundForPair = std::integral_constant<
+    bool, std::is_same<StringType, std::string>::value &&
+              (std::is_same<First, absl::string_view>::value ||
+               std::is_same<Second, absl::string_view>::value)>;
+
+
 // This class implements the range that is returned by absl::StrSplit(). This
 // class has templated conversion operators that allow it to be implicitly
 // converted to a variety of types that the caller may have specified on the
@@ -281,10 +299,24 @@ class Splitter {
 
   // An implicit conversion operator that is restricted to only those containers
   // that the splitter is convertible to.
-  template <typename Container,
-            typename = typename std::enable_if<
-                SplitterIsConvertibleTo<Container>::value>::type>
-  operator Container() const {  // NOLINT(runtime/explicit)
+  template <
+      typename Container,
+      std::enable_if_t<ShouldUseLifetimeBound<StringType, Container>::value &&
+                           SplitterIsConvertibleTo<Container>::value,
+                       std::nullptr_t> = nullptr>
+  // NOLINTNEXTLINE(google-explicit-constructor)
+  operator Container() const ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return ConvertToContainer<Container, typename Container::value_type,
+                              HasMappedType<Container>::value>()(*this);
+  }
+
+  template <
+      typename Container,
+      std::enable_if_t<!ShouldUseLifetimeBound<StringType, Container>::value &&
+                           SplitterIsConvertibleTo<Container>::value,
+                       std::nullptr_t> = nullptr>
+  // NOLINTNEXTLINE(google-explicit-constructor)
+  operator Container() const {
     return ConvertToContainer<Container, typename Container::value_type,
                               HasMappedType<Container>::value>()(*this);
   }
@@ -293,8 +325,27 @@ class Splitter {
   // strings returned by the begin() iterator. Either/both of .first and .second
   // will be constructed with empty strings if the iterator doesn't have a
   // corresponding value.
+  template <typename First, typename Second,
+            std::enable_if_t<
+                ShouldUseLifetimeBoundForPair<StringType, First, Second>::value,
+                std::nullptr_t> = nullptr>
+  // NOLINTNEXTLINE(google-explicit-constructor)
+  operator std::pair<First, Second>() const ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return ConvertToPair<First, Second>();
+  }
+
+  template <typename First, typename Second,
+            std::enable_if_t<!ShouldUseLifetimeBoundForPair<StringType, First,
+                                                            Second>::value,
+                             std::nullptr_t> = nullptr>
+  // NOLINTNEXTLINE(google-explicit-constructor)
+  operator std::pair<First, Second>() const {
+    return ConvertToPair<First, Second>();
+  }
+
+ private:
   template <typename First, typename Second>
-  operator std::pair<First, Second>() const {  // NOLINT(runtime/explicit)
+  std::pair<First, Second> ConvertToPair() const {
     absl::string_view first, second;
     auto it = begin();
     if (it != end()) {
@@ -306,7 +357,6 @@ class Splitter {
     return {First(first), Second(second)};
   }
 
- private:
   // ConvertToContainer is a functor converting a Splitter to the requested
   // Container of ValueType. It is specialized below to optimize splitting to
   // certain combinations of Container and ValueType.
diff --git a/absl/strings/match.cc b/absl/strings/match.cc
index 2d672509..3b81b2c0 100644
--- a/absl/strings/match.cc
+++ b/absl/strings/match.cc
@@ -14,6 +14,12 @@
 
 #include "absl/strings/match.h"
 
+#include <algorithm>
+#include <cstdint>
+
+#include "absl/base/internal/endian.h"
+#include "absl/numeric/bits.h"
+#include "absl/strings/ascii.h"
 #include "absl/strings/internal/memutil.h"
 
 namespace absl {
@@ -27,6 +33,27 @@ bool EqualsIgnoreCase(absl::string_view piece1,
   // memcasecmp uses absl::ascii_tolower().
 }
 
+bool StrContainsIgnoreCase(absl::string_view haystack,
+                           absl::string_view needle) noexcept {
+  while (haystack.size() >= needle.size()) {
+    if (StartsWithIgnoreCase(haystack, needle)) return true;
+    haystack.remove_prefix(1);
+  }
+  return false;
+}
+
+bool StrContainsIgnoreCase(absl::string_view haystack,
+                           char needle) noexcept {
+  char upper_needle = absl::ascii_toupper(static_cast<unsigned char>(needle));
+  char lower_needle = absl::ascii_tolower(static_cast<unsigned char>(needle));
+  if (upper_needle == lower_needle) {
+    return StrContains(haystack, needle);
+  } else {
+    const char both_cstr[3] = {lower_needle, upper_needle, '\0'};
+    return haystack.find_first_of(both_cstr) != absl::string_view::npos;
+  }
+}
+
 bool StartsWithIgnoreCase(absl::string_view text,
                           absl::string_view prefix) noexcept {
   return (text.size() >= prefix.size()) &&
@@ -39,5 +66,65 @@ bool EndsWithIgnoreCase(absl::string_view text,
          EqualsIgnoreCase(text.substr(text.size() - suffix.size()), suffix);
 }
 
+absl::string_view FindLongestCommonPrefix(absl::string_view a,
+                                          absl::string_view b) {
+  const absl::string_view::size_type limit = std::min(a.size(), b.size());
+  const char* const pa = a.data();
+  const char* const pb = b.data();
+  absl::string_view::size_type count = (unsigned) 0;
+
+  if (ABSL_PREDICT_FALSE(limit < 8)) {
+    while (ABSL_PREDICT_TRUE(count + 2 <= limit)) {
+      uint16_t xor_bytes = absl::little_endian::Load16(pa + count) ^
+                           absl::little_endian::Load16(pb + count);
+      if (ABSL_PREDICT_FALSE(xor_bytes != 0)) {
+        if (ABSL_PREDICT_TRUE((xor_bytes & 0xff) == 0)) ++count;
+        return absl::string_view(pa, count);
+      }
+      count += 2;
+    }
+    if (ABSL_PREDICT_TRUE(count != limit)) {
+      if (ABSL_PREDICT_TRUE(pa[count] == pb[count])) ++count;
+    }
+    return absl::string_view(pa, count);
+  }
+
+  do {
+    uint64_t xor_bytes = absl::little_endian::Load64(pa + count) ^
+                         absl::little_endian::Load64(pb + count);
+    if (ABSL_PREDICT_FALSE(xor_bytes != 0)) {
+      count += static_cast<uint64_t>(absl::countr_zero(xor_bytes) >> 3);
+      return absl::string_view(pa, count);
+    }
+    count += 8;
+  } while (ABSL_PREDICT_TRUE(count + 8 < limit));
+
+  count = limit - 8;
+  uint64_t xor_bytes = absl::little_endian::Load64(pa + count) ^
+                       absl::little_endian::Load64(pb + count);
+  if (ABSL_PREDICT_TRUE(xor_bytes != 0)) {
+    count += static_cast<uint64_t>(absl::countr_zero(xor_bytes) >> 3);
+    return absl::string_view(pa, count);
+  }
+  return absl::string_view(pa, limit);
+}
+
+absl::string_view FindLongestCommonSuffix(absl::string_view a,
+                                          absl::string_view b) {
+  const absl::string_view::size_type limit = std::min(a.size(), b.size());
+  if (limit == 0) return absl::string_view();
+
+  const char* pa = a.data() + a.size() - 1;
+  const char* pb = b.data() + b.size() - 1;
+  absl::string_view::size_type count = (unsigned) 0;
+  while (count < limit && *pa == *pb) {
+    --pa;
+    --pb;
+    ++count;
+  }
+
+  return absl::string_view(++pa, count);
+}
+
 ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/strings/match.h b/absl/strings/match.h
index 038cbb3f..1eeafbbf 100644
--- a/absl/strings/match.h
+++ b/absl/strings/match.h
@@ -72,6 +72,15 @@ inline bool EndsWith(absl::string_view text,
           memcmp(text.data() + (text.size() - suffix.size()), suffix.data(),
                  suffix.size()) == 0);
 }
+// StrContainsIgnoreCase()
+//
+// Returns whether a given ASCII string `haystack` contains the ASCII substring
+// `needle`, ignoring case in the comparison.
+bool StrContainsIgnoreCase(absl::string_view haystack,
+                           absl::string_view needle) noexcept;
+
+bool StrContainsIgnoreCase(absl::string_view haystack,
+                           char needle) noexcept;
 
 // EqualsIgnoreCase()
 //
@@ -94,6 +103,16 @@ bool StartsWithIgnoreCase(absl::string_view text,
 bool EndsWithIgnoreCase(absl::string_view text,
                         absl::string_view suffix) noexcept;
 
+// Yields the longest prefix in common between both input strings.
+// Pointer-wise, the returned result is a subset of input "a".
+absl::string_view FindLongestCommonPrefix(absl::string_view a,
+                                          absl::string_view b);
+
+// Yields the longest suffix in common between both input strings.
+// Pointer-wise, the returned result is a subset of input "a".
+absl::string_view FindLongestCommonSuffix(absl::string_view a,
+                                          absl::string_view b);
+
 ABSL_NAMESPACE_END
 }  // namespace absl
 
diff --git a/absl/strings/match_test.cc b/absl/strings/match_test.cc
index 5841bc1b..71618f71 100644
--- a/absl/strings/match_test.cc
+++ b/absl/strings/match_test.cc
@@ -124,4 +124,165 @@ TEST(MatchTest, EndsWithIgnoreCase) {
   EXPECT_FALSE(absl::EndsWithIgnoreCase("", "fo"));
 }
 
+TEST(MatchTest, ContainsIgnoreCase) {
+  EXPECT_TRUE(absl::StrContainsIgnoreCase("foo", "foo"));
+  EXPECT_TRUE(absl::StrContainsIgnoreCase("FOO", "Foo"));
+  EXPECT_TRUE(absl::StrContainsIgnoreCase("--FOO", "Foo"));
+  EXPECT_TRUE(absl::StrContainsIgnoreCase("FOO--", "Foo"));
+  EXPECT_FALSE(absl::StrContainsIgnoreCase("BAR", "Foo"));
+  EXPECT_FALSE(absl::StrContainsIgnoreCase("BAR", "Foo"));
+  EXPECT_TRUE(absl::StrContainsIgnoreCase("123456", "123456"));
+  EXPECT_TRUE(absl::StrContainsIgnoreCase("123456", "234"));
+  EXPECT_TRUE(absl::StrContainsIgnoreCase("", ""));
+  EXPECT_TRUE(absl::StrContainsIgnoreCase("abc", ""));
+  EXPECT_FALSE(absl::StrContainsIgnoreCase("", "a"));
+}
+
+TEST(MatchTest, ContainsCharIgnoreCase) {
+  absl::string_view a("AaBCdefg!");
+  absl::string_view b("AaBCd!");
+  EXPECT_TRUE(absl::StrContainsIgnoreCase(a, 'a'));
+  EXPECT_TRUE(absl::StrContainsIgnoreCase(a, 'A'));
+  EXPECT_TRUE(absl::StrContainsIgnoreCase(a, 'b'));
+  EXPECT_TRUE(absl::StrContainsIgnoreCase(a, 'B'));
+  EXPECT_TRUE(absl::StrContainsIgnoreCase(a, 'e'));
+  EXPECT_TRUE(absl::StrContainsIgnoreCase(a, 'E'));
+  EXPECT_FALSE(absl::StrContainsIgnoreCase(a, 'h'));
+  EXPECT_FALSE(absl::StrContainsIgnoreCase(a, 'H'));
+  EXPECT_TRUE(absl::StrContainsIgnoreCase(a, '!'));
+  EXPECT_FALSE(absl::StrContainsIgnoreCase(a, '?'));
+
+  EXPECT_TRUE(absl::StrContainsIgnoreCase(b, 'a'));
+  EXPECT_TRUE(absl::StrContainsIgnoreCase(b, 'A'));
+  EXPECT_TRUE(absl::StrContainsIgnoreCase(b, 'b'));
+  EXPECT_TRUE(absl::StrContainsIgnoreCase(b, 'B'));
+  EXPECT_FALSE(absl::StrContainsIgnoreCase(b, 'e'));
+  EXPECT_FALSE(absl::StrContainsIgnoreCase(b, 'E'));
+  EXPECT_FALSE(absl::StrContainsIgnoreCase(b, 'h'));
+  EXPECT_FALSE(absl::StrContainsIgnoreCase(b, 'H'));
+  EXPECT_TRUE(absl::StrContainsIgnoreCase(b, '!'));
+  EXPECT_FALSE(absl::StrContainsIgnoreCase(b, '?'));
+
+  EXPECT_FALSE(absl::StrContainsIgnoreCase("", 'a'));
+  EXPECT_FALSE(absl::StrContainsIgnoreCase("", 'A'));
+  EXPECT_FALSE(absl::StrContainsIgnoreCase("", '0'));
+}
+
+TEST(MatchTest, FindLongestCommonPrefix) {
+  EXPECT_EQ(absl::FindLongestCommonPrefix("", ""), "");
+  EXPECT_EQ(absl::FindLongestCommonPrefix("", "abc"), "");
+  EXPECT_EQ(absl::FindLongestCommonPrefix("abc", ""), "");
+  EXPECT_EQ(absl::FindLongestCommonPrefix("ab", "abc"), "ab");
+  EXPECT_EQ(absl::FindLongestCommonPrefix("abc", "ab"), "ab");
+  EXPECT_EQ(absl::FindLongestCommonPrefix("abc", "abd"), "ab");
+  EXPECT_EQ(absl::FindLongestCommonPrefix("abc", "abcd"), "abc");
+  EXPECT_EQ(absl::FindLongestCommonPrefix("abcd", "abcd"), "abcd");
+  EXPECT_EQ(absl::FindLongestCommonPrefix("abcd", "efgh"), "");
+
+  // "abcde" v. "abc" but in the middle of other data
+  EXPECT_EQ(absl::FindLongestCommonPrefix(
+                absl::string_view("1234 abcdef").substr(5, 5),
+                absl::string_view("5678 abcdef").substr(5, 3)),
+            "abc");
+}
+
+// Since the little-endian implementation involves a bit of if-else and various
+// return paths, the following tests aims to provide full test coverage of the
+// implementation.
+TEST(MatchTest, FindLongestCommonPrefixLoad16Mismatch) {
+  const std::string x1 = "abcdefgh";
+  const std::string x2 = "abcde_";
+  EXPECT_EQ(absl::FindLongestCommonPrefix(x1, x2), "abcde");
+  EXPECT_EQ(absl::FindLongestCommonPrefix(x2, x1), "abcde");
+}
+
+TEST(MatchTest, FindLongestCommonPrefixLoad16MatchesNoLast) {
+  const std::string x1 = "abcdef";
+  const std::string x2 = "abcdef";
+  EXPECT_EQ(absl::FindLongestCommonPrefix(x1, x2), "abcdef");
+  EXPECT_EQ(absl::FindLongestCommonPrefix(x2, x1), "abcdef");
+}
+
+TEST(MatchTest, FindLongestCommonPrefixLoad16MatchesLastCharMismatches) {
+  const std::string x1 = "abcdefg";
+  const std::string x2 = "abcdef_h";
+  EXPECT_EQ(absl::FindLongestCommonPrefix(x1, x2), "abcdef");
+  EXPECT_EQ(absl::FindLongestCommonPrefix(x2, x1), "abcdef");
+}
+
+TEST(MatchTest, FindLongestCommonPrefixLoad16MatchesLastMatches) {
+  const std::string x1 = "abcde";
+  const std::string x2 = "abcdefgh";
+  EXPECT_EQ(absl::FindLongestCommonPrefix(x1, x2), "abcde");
+  EXPECT_EQ(absl::FindLongestCommonPrefix(x2, x1), "abcde");
+}
+
+TEST(MatchTest, FindLongestCommonPrefixSize8Load64Mismatches) {
+  const std::string x1 = "abcdefghijk";
+  const std::string x2 = "abcde_g_";
+  EXPECT_EQ(absl::FindLongestCommonPrefix(x1, x2), "abcde");
+  EXPECT_EQ(absl::FindLongestCommonPrefix(x2, x1), "abcde");
+}
+
+TEST(MatchTest, FindLongestCommonPrefixSize8Load64Matches) {
+  const std::string x1 = "abcdefgh";
+  const std::string x2 = "abcdefgh";
+  EXPECT_EQ(absl::FindLongestCommonPrefix(x1, x2), "abcdefgh");
+  EXPECT_EQ(absl::FindLongestCommonPrefix(x2, x1), "abcdefgh");
+}
+
+TEST(MatchTest, FindLongestCommonPrefixSize15Load64Mismatches) {
+  const std::string x1 = "012345670123456";
+  const std::string x2 = "0123456701_34_6";
+  EXPECT_EQ(absl::FindLongestCommonPrefix(x1, x2), "0123456701");
+  EXPECT_EQ(absl::FindLongestCommonPrefix(x2, x1), "0123456701");
+}
+
+TEST(MatchTest, FindLongestCommonPrefixSize15Load64Matches) {
+  const std::string x1 = "012345670123456";
+  const std::string x2 = "0123456701234567";
+  EXPECT_EQ(absl::FindLongestCommonPrefix(x1, x2), "012345670123456");
+  EXPECT_EQ(absl::FindLongestCommonPrefix(x2, x1), "012345670123456");
+}
+
+TEST(MatchTest, FindLongestCommonPrefixSizeFirstByteOfLast8BytesMismatch) {
+  const std::string x1 = "012345670123456701234567";
+  const std::string x2 = "0123456701234567_1234567";
+  EXPECT_EQ(absl::FindLongestCommonPrefix(x1, x2), "0123456701234567");
+  EXPECT_EQ(absl::FindLongestCommonPrefix(x2, x1), "0123456701234567");
+}
+
+TEST(MatchTest, FindLongestCommonPrefixLargeLastCharMismatches) {
+  const std::string x1(300, 'x');
+  std::string x2 = x1;
+  x2.back() = '#';
+  EXPECT_EQ(absl::FindLongestCommonPrefix(x1, x2), std::string(299, 'x'));
+  EXPECT_EQ(absl::FindLongestCommonPrefix(x2, x1), std::string(299, 'x'));
+}
+
+TEST(MatchTest, FindLongestCommonPrefixLargeFullMatch) {
+  const std::string x1(300, 'x');
+  const std::string x2 = x1;
+  EXPECT_EQ(absl::FindLongestCommonPrefix(x1, x2), std::string(300, 'x'));
+  EXPECT_EQ(absl::FindLongestCommonPrefix(x2, x1), std::string(300, 'x'));
+}
+
+TEST(MatchTest, FindLongestCommonSuffix) {
+  EXPECT_EQ(absl::FindLongestCommonSuffix("", ""), "");
+  EXPECT_EQ(absl::FindLongestCommonSuffix("", "abc"), "");
+  EXPECT_EQ(absl::FindLongestCommonSuffix("abc", ""), "");
+  EXPECT_EQ(absl::FindLongestCommonSuffix("bc", "abc"), "bc");
+  EXPECT_EQ(absl::FindLongestCommonSuffix("abc", "bc"), "bc");
+  EXPECT_EQ(absl::FindLongestCommonSuffix("abc", "dbc"), "bc");
+  EXPECT_EQ(absl::FindLongestCommonSuffix("bcd", "abcd"), "bcd");
+  EXPECT_EQ(absl::FindLongestCommonSuffix("abcd", "abcd"), "abcd");
+  EXPECT_EQ(absl::FindLongestCommonSuffix("abcd", "efgh"), "");
+
+  // "abcde" v. "cde" but in the middle of other data
+  EXPECT_EQ(absl::FindLongestCommonSuffix(
+                absl::string_view("1234 abcdef").substr(5, 5),
+                absl::string_view("5678 abcdef").substr(7, 3)),
+            "cde");
+}
+
 }  // namespace
diff --git a/absl/strings/numbers.cc b/absl/strings/numbers.cc
index 2987158e..c43c6bcc 100644
--- a/absl/strings/numbers.cc
+++ b/absl/strings/numbers.cc
@@ -31,7 +31,9 @@
 #include <utility>
 
 #include "absl/base/attributes.h"
+#include "absl/base/internal/endian.h"
 #include "absl/base/internal/raw_logging.h"
+#include "absl/base/optimization.h"
 #include "absl/numeric/bits.h"
 #include "absl/strings/ascii.h"
 #include "absl/strings/charconv.h"
@@ -136,82 +138,132 @@ bool SimpleAtob(absl::string_view str, bool* out) {
 
 namespace {
 
-// Used to optimize printing a decimal number's final digit.
-const char one_ASCII_final_digits[10][2] {
-  {'0', 0}, {'1', 0}, {'2', 0}, {'3', 0}, {'4', 0},
-  {'5', 0}, {'6', 0}, {'7', 0}, {'8', 0}, {'9', 0},
-};
+// Various routines to encode integers to strings.
+
+// We split data encodings into a group of 2 digits, 4 digits, 8 digits as
+// it's easier to combine powers of two into scalar arithmetic.
+
+// Previous implementation used a lookup table of 200 bytes for every 2 bytes
+// and it was memory bound, any L1 cache miss would result in a much slower
+// result. When benchmarking with a cache eviction rate of several percent,
+// this implementation proved to be better.
+
+// These constants represent '00', '0000' and '00000000' as ascii strings in
+// integers. We can add these numbers if we encode to bytes from 0 to 9. as
+// 'i' = '0' + i for 0 <= i <= 9.
+constexpr uint32_t kTwoZeroBytes = 0x0101 * '0';
+constexpr uint64_t kFourZeroBytes = 0x01010101 * '0';
+constexpr uint64_t kEightZeroBytes = 0x0101010101010101ull * '0';
+
+// * 103 / 1024 is a division by 10 for values from 0 to 99. It's also a
+// division of a structure [k takes 2 bytes][m takes 2 bytes], then * 103 / 1024
+// will be [k / 10][m / 10]. It allows parallel division.
+constexpr uint64_t kDivisionBy10Mul = 103u;
+constexpr uint64_t kDivisionBy10Div = 1 << 10;
+
+// * 10486 / 1048576 is a division by 100 for values from 0 to 9999.
+constexpr uint64_t kDivisionBy100Mul = 10486u;
+constexpr uint64_t kDivisionBy100Div = 1 << 20;
+
+// Encode functions write the ASCII output of input `n` to `out_str`.
+inline char* EncodeHundred(uint32_t n, char* out_str) {
+  int num_digits = static_cast<int>(n - 10) >> 8;
+  uint32_t base = kTwoZeroBytes;
+  uint32_t div10 = (n * kDivisionBy10Mul) / kDivisionBy10Div;
+  uint32_t mod10 = n - 10u * div10;
+  base += div10 + (mod10 << 8);
+  base >>= num_digits & 8;
+  little_endian::Store16(out_str, static_cast<uint16_t>(base));
+  return out_str + 2 + num_digits;
+}
 
-}  // namespace
+inline char* EncodeTenThousand(uint32_t n, char* out_str) {
+  // We split lower 2 digits and upper 2 digits of n into 2 byte consecutive
+  // blocks. 123 ->  [\0\1][\0\23]. We divide by 10 both blocks
+  // (it's 1 division + zeroing upper bits), and compute modulo 10 as well "in
+  // parallel". Then we combine both results to have both ASCII digits,
+  // strip trailing zeros, add ASCII '0000' and return.
+  uint32_t div100 = (n * kDivisionBy100Mul) / kDivisionBy100Div;
+  uint32_t mod100 = n - 100ull * div100;
+  uint32_t hundreds = (mod100 << 16) + div100;
+  uint32_t tens = (hundreds * kDivisionBy10Mul) / kDivisionBy10Div;
+  tens &= (0xFull << 16) | 0xFull;
+  tens += (hundreds - 10ull * tens) << 8;
+  ABSL_ASSUME(tens != 0);
+  // The result can contain trailing zero bits, we need to strip them to a first
+  // significant byte in a final representation. For example, for n = 123, we
+  // have tens to have representation \0\1\2\3. We do `& -8` to round
+  // to a multiple to 8 to strip zero bytes, not all zero bits.
+  // countr_zero to help.
+  // 0 minus 8 to make MSVC happy.
+  uint32_t zeroes = static_cast<uint32_t>(absl::countr_zero(tens)) & (0 - 8ull);
+  tens += kFourZeroBytes;
+  tens >>= zeroes;
+  little_endian::Store32(out_str, tens);
+  return out_str + sizeof(tens) - zeroes / 8;
+}
 
-char* numbers_internal::FastIntToBuffer(uint32_t i, char* buffer) {
-  uint32_t digits;
-  // The idea of this implementation is to trim the number of divides to as few
-  // as possible, and also reducing memory stores and branches, by going in
-  // steps of two digits at a time rather than one whenever possible.
-  // The huge-number case is first, in the hopes that the compiler will output
-  // that case in one branch-free block of code, and only output conditional
-  // branches into it from below.
-  if (i >= 1000000000) {     // >= 1,000,000,000
-    digits = i / 100000000;  //      100,000,000
-    i -= digits * 100000000;
-    PutTwoDigits(digits, buffer);
-    buffer += 2;
-  lt100_000_000:
-    digits = i / 1000000;  // 1,000,000
-    i -= digits * 1000000;
-    PutTwoDigits(digits, buffer);
-    buffer += 2;
-  lt1_000_000:
-    digits = i / 10000;  // 10,000
-    i -= digits * 10000;
-    PutTwoDigits(digits, buffer);
-    buffer += 2;
-  lt10_000:
-    digits = i / 100;
-    i -= digits * 100;
-    PutTwoDigits(digits, buffer);
-    buffer += 2;
- lt100:
-    digits = i;
-    PutTwoDigits(digits, buffer);
-    buffer += 2;
-    *buffer = 0;
-    return buffer;
-  }
+// Prepare functions return an integer that should be written to out_str
+// (but possibly include trailing zeros).
+// For hi < 10000, lo < 10000 returns uint64_t as encoded in ASCII with
+// possibly trailing zeroes of the number hi * 10000 + lo.
+inline uint64_t PrepareTenThousands(uint64_t hi, uint64_t lo) {
+  uint64_t merged = hi | (lo << 32);
+  uint64_t div100 = ((merged * kDivisionBy100Mul) / kDivisionBy100Div) &
+                    ((0x7Full << 32) | 0x7Full);
+  uint64_t mod100 = merged - 100ull * div100;
+  uint64_t hundreds = (mod100 << 16) + div100;
+  uint64_t tens = (hundreds * kDivisionBy10Mul) / kDivisionBy10Div;
+  tens &= (0xFull << 48) | (0xFull << 32) | (0xFull << 16) | 0xFull;
+  tens += (hundreds - 10ull * tens) << 8;
+  return tens;
+}
 
-  if (i < 100) {
-    digits = i;
-    if (i >= 10) goto lt100;
-    memcpy(buffer, one_ASCII_final_digits[i], 2);
-    return buffer + 1;
+inline char* EncodeFullU32(uint32_t n, char* out_str) {
+  if (n < 100'000'000) {
+    uint64_t bottom = PrepareTenThousands(n / 10000, n % 10000);
+    ABSL_ASSUME(bottom != 0);
+    // 0 minus 8 to make MSVC happy.
+    uint32_t zeroes = static_cast<uint32_t>(absl::countr_zero(bottom))
+        & (0 - 8ull);
+    uint64_t bottom_res = bottom + kEightZeroBytes;
+    bottom_res >>= zeroes;
+    little_endian::Store64(out_str, bottom_res);
+    return out_str + sizeof(bottom) - zeroes / 8;
   }
-  if (i < 10000) {  //    10,000
-    if (i >= 1000) goto lt10_000;
-    digits = i / 100;
-    i -= digits * 100;
-    *buffer++ = '0' + static_cast<char>(digits);
-    goto lt100;
-  }
-  if (i < 1000000) {  //    1,000,000
-    if (i >= 100000) goto lt1_000_000;
-    digits = i / 10000;  //    10,000
-    i -= digits * 10000;
-    *buffer++ = '0' + static_cast<char>(digits);
-    goto lt10_000;
+  uint32_t top = n / 100'000'000;
+  n %= 100'000'000;
+  uint64_t bottom = PrepareTenThousands(n / 10000, n % 10000);
+  uint64_t bottom_res = bottom + kEightZeroBytes;
+  out_str = EncodeHundred(top, out_str);
+  little_endian::Store64(out_str, bottom_res);
+  return out_str + sizeof(bottom);
+}
+
+}  // namespace
+
+void numbers_internal::PutTwoDigits(uint32_t i, char* buf) {
+  assert(i < 100);
+  uint32_t base = kTwoZeroBytes;
+  uint32_t div10 = (i * kDivisionBy10Mul) / kDivisionBy10Div;
+  uint32_t mod10 = i - 10u * div10;
+  base += div10 + (mod10 << 8);
+  little_endian::Store16(buf, static_cast<uint16_t>(base));
+}
+
+char* numbers_internal::FastIntToBuffer(uint32_t n, char* out_str) {
+  if (n < 100) {
+    out_str = EncodeHundred(n, out_str);
+    goto set_last_zero;
   }
-  if (i < 100000000) {  //    100,000,000
-    if (i >= 10000000) goto lt100_000_000;
-    digits = i / 1000000;  //   1,000,000
-    i -= digits * 1000000;
-    *buffer++ = '0' + static_cast<char>(digits);
-    goto lt1_000_000;
+  if (n < 10000) {
+    out_str = EncodeTenThousand(n, out_str);
+    goto set_last_zero;
   }
-  // we already know that i < 1,000,000,000
-  digits = i / 100000000;  //   100,000,000
-  i -= digits * 100000000;
-  *buffer++ = '0' + static_cast<char>(digits);
-  goto lt100_000_000;
+  out_str = EncodeFullU32(n, out_str);
+set_last_zero:
+  *out_str = '\0';
+  return out_str;
 }
 
 char* numbers_internal::FastIntToBuffer(int32_t i, char* buffer) {
@@ -219,7 +271,7 @@ char* numbers_internal::FastIntToBuffer(int32_t i, char* buffer) {
   if (i < 0) {
     *buffer++ = '-';
     // We need to do the negation in modular (i.e., "unsigned")
-    // arithmetic; MSVC++ apprently warns for plain "-u", so
+    // arithmetic; MSVC++ apparently warns for plain "-u", so
     // we write the equivalent expression "0 - u" instead.
     u = 0 - u;
   }
@@ -230,41 +282,40 @@ char* numbers_internal::FastIntToBuffer(uint64_t i, char* buffer) {
   uint32_t u32 = static_cast<uint32_t>(i);
   if (u32 == i) return numbers_internal::FastIntToBuffer(u32, buffer);
 
-  // Here we know i has at least 10 decimal digits.
-  uint64_t top_1to11 = i / 1000000000;
-  u32 = static_cast<uint32_t>(i - top_1to11 * 1000000000);
-  uint32_t top_1to11_32 = static_cast<uint32_t>(top_1to11);
+  // 10**9 < 2**32 <= i < 10**10, we can do 2+8
+  uint64_t div08 = i / 100'000'000ull;
+  uint64_t mod08 = i % 100'000'000ull;
+  uint64_t mod_result =
+      PrepareTenThousands(mod08 / 10000, mod08 % 10000) + kEightZeroBytes;
+  if (i < 10'000'000'000ull) {
+    buffer = EncodeHundred(static_cast<uint32_t>(div08), buffer);
+    little_endian::Store64(buffer, mod_result);
+    buffer += 8;
+    goto set_last_zero;
+  }
 
-  if (top_1to11_32 == top_1to11) {
-    buffer = numbers_internal::FastIntToBuffer(top_1to11_32, buffer);
+  // i < 10**16, in this case 8+8
+  if (i < 10'000'000'000'000'000ull) {
+    buffer = EncodeFullU32(static_cast<uint32_t>(div08), buffer);
+    little_endian::Store64(buffer, mod_result);
+    buffer += 8;
+    goto set_last_zero;
   } else {
-    // top_1to11 has more than 32 bits too; print it in two steps.
-    uint32_t top_8to9 = static_cast<uint32_t>(top_1to11 / 100);
-    uint32_t mid_2 = static_cast<uint32_t>(top_1to11 - top_8to9 * 100);
-    buffer = numbers_internal::FastIntToBuffer(top_8to9, buffer);
-    PutTwoDigits(mid_2, buffer);
-    buffer += 2;
+    // 4 + 8 + 8
+    uint64_t div016 = i / 10'000'000'000'000'000ull;
+    buffer = EncodeTenThousand(static_cast<uint32_t>(div016), buffer);
+    uint64_t mid_result = div08 - div016 * 100'000'000ull;
+    mid_result = PrepareTenThousands(mid_result / 10000, mid_result % 10000) +
+                 kEightZeroBytes;
+    little_endian::Store64(buffer, mid_result);
+    buffer += 8;
+    little_endian::Store64(buffer, mod_result);
+    buffer += 8;
+    goto set_last_zero;
   }
-
-  // We have only 9 digits now, again the maximum uint32_t can handle fully.
-  uint32_t digits = u32 / 10000000;  // 10,000,000
-  u32 -= digits * 10000000;
-  PutTwoDigits(digits, buffer);
-  buffer += 2;
-  digits = u32 / 100000;  // 100,000
-  u32 -= digits * 100000;
-  PutTwoDigits(digits, buffer);
-  buffer += 2;
-  digits = u32 / 1000;  // 1,000
-  u32 -= digits * 1000;
-  PutTwoDigits(digits, buffer);
-  buffer += 2;
-  digits = u32 / 10;
-  u32 -= digits * 10;
-  PutTwoDigits(digits, buffer);
-  buffer += 2;
-  memcpy(buffer, one_ASCII_final_digits[u32], 2);
-  return buffer + 1;
+set_last_zero:
+  *buffer = '\0';
+  return buffer;
 }
 
 char* numbers_internal::FastIntToBuffer(int64_t i, char* buffer) {
@@ -1048,25 +1099,6 @@ ABSL_CONST_INIT ABSL_DLL const char kHexTable[513] =
     "e0e1e2e3e4e5e6e7e8e9eaebecedeeef"
     "f0f1f2f3f4f5f6f7f8f9fafbfcfdfeff";
 
-ABSL_CONST_INIT ABSL_DLL const char two_ASCII_digits[100][2] = {
-    {'0', '0'}, {'0', '1'}, {'0', '2'}, {'0', '3'}, {'0', '4'}, {'0', '5'},
-    {'0', '6'}, {'0', '7'}, {'0', '8'}, {'0', '9'}, {'1', '0'}, {'1', '1'},
-    {'1', '2'}, {'1', '3'}, {'1', '4'}, {'1', '5'}, {'1', '6'}, {'1', '7'},
-    {'1', '8'}, {'1', '9'}, {'2', '0'}, {'2', '1'}, {'2', '2'}, {'2', '3'},
-    {'2', '4'}, {'2', '5'}, {'2', '6'}, {'2', '7'}, {'2', '8'}, {'2', '9'},
-    {'3', '0'}, {'3', '1'}, {'3', '2'}, {'3', '3'}, {'3', '4'}, {'3', '5'},
-    {'3', '6'}, {'3', '7'}, {'3', '8'}, {'3', '9'}, {'4', '0'}, {'4', '1'},
-    {'4', '2'}, {'4', '3'}, {'4', '4'}, {'4', '5'}, {'4', '6'}, {'4', '7'},
-    {'4', '8'}, {'4', '9'}, {'5', '0'}, {'5', '1'}, {'5', '2'}, {'5', '3'},
-    {'5', '4'}, {'5', '5'}, {'5', '6'}, {'5', '7'}, {'5', '8'}, {'5', '9'},
-    {'6', '0'}, {'6', '1'}, {'6', '2'}, {'6', '3'}, {'6', '4'}, {'6', '5'},
-    {'6', '6'}, {'6', '7'}, {'6', '8'}, {'6', '9'}, {'7', '0'}, {'7', '1'},
-    {'7', '2'}, {'7', '3'}, {'7', '4'}, {'7', '5'}, {'7', '6'}, {'7', '7'},
-    {'7', '8'}, {'7', '9'}, {'8', '0'}, {'8', '1'}, {'8', '2'}, {'8', '3'},
-    {'8', '4'}, {'8', '5'}, {'8', '6'}, {'8', '7'}, {'8', '8'}, {'8', '9'},
-    {'9', '0'}, {'9', '1'}, {'9', '2'}, {'9', '3'}, {'9', '4'}, {'9', '5'},
-    {'9', '6'}, {'9', '7'}, {'9', '8'}, {'9', '9'}};
-
 bool safe_strto32_base(absl::string_view text, int32_t* value, int base) {
   return safe_int_internal<int32_t>(text, value, base);
 }
diff --git a/absl/strings/numbers.h b/absl/strings/numbers.h
index 86c84ed3..d7630cef 100644
--- a/absl/strings/numbers.h
+++ b/absl/strings/numbers.h
@@ -125,8 +125,6 @@ namespace numbers_internal {
 ABSL_DLL extern const char kHexChar[17];  // 0123456789abcdef
 ABSL_DLL extern const char
     kHexTable[513];  // 000102030405060708090a0b0c0d0e0f1011...
-ABSL_DLL extern const char
-    two_ASCII_digits[100][2];  // 00, 01, 02, 03...
 
 // Writes a two-character representation of 'i' to 'buf'. 'i' must be in the
 // range 0 <= i < 100, and buf must have space for two characters. Example:
@@ -134,10 +132,7 @@ ABSL_DLL extern const char
 //   PutTwoDigits(42, buf);
 //   // buf[0] == '4'
 //   // buf[1] == '2'
-inline void PutTwoDigits(size_t i, char* buf) {
-  assert(i < 100);
-  memcpy(buf, two_ASCII_digits[i], 2);
-}
+void PutTwoDigits(uint32_t i, char* buf);
 
 // safe_strto?() functions for implementing SimpleAtoi()
 
diff --git a/absl/strings/numbers_test.cc b/absl/strings/numbers_test.cc
index b3c098d1..2864bda2 100644
--- a/absl/strings/numbers_test.cc
+++ b/absl/strings/numbers_test.cc
@@ -37,7 +37,7 @@
 
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
-#include "absl/base/internal/raw_logging.h"
+#include "absl/log/log.h"
 #include "absl/random/distributions.h"
 #include "absl/random/random.h"
 #include "absl/strings/internal/numbers_test_common.h"
@@ -1337,11 +1337,9 @@ TEST_F(SimpleDtoaTest, ExhaustiveDoubleToSixDigits) {
     if (strcmp(sixdigitsbuf, snprintfbuf) != 0) {
       mismatches.push_back(d);
       if (mismatches.size() < 10) {
-        ABSL_RAW_LOG(ERROR, "%s",
-                     absl::StrCat("Six-digit failure with double.  ", "d=", d,
-                                  "=", d, " sixdigits=", sixdigitsbuf,
-                                  " printf(%g)=", snprintfbuf)
-                         .c_str());
+        LOG(ERROR) << "Six-digit failure with double.  d=" << d
+                   << " sixdigits=" << sixdigitsbuf
+                   << " printf(%g)=" << snprintfbuf;
       }
     }
   };
@@ -1389,12 +1387,10 @@ TEST_F(SimpleDtoaTest, ExhaustiveDoubleToSixDigits) {
       if (kFloatNumCases >= 1e9) {
         // The exhaustive test takes a very long time, so log progress.
         char buf[kSixDigitsToBufferSize];
-        ABSL_RAW_LOG(
-            INFO, "%s",
-            absl::StrCat("Exp ", exponent, " powten=", powten, "(", powten,
-                         ") (",
-                         std::string(buf, SixDigitsToBuffer(powten, buf)), ")")
-                .c_str());
+        LOG(INFO) << "Exp " << exponent << " powten=" << powten << "(" << powten
+                  << ") ("
+                  << absl::string_view(buf, SixDigitsToBuffer(powten, buf))
+                  << ")";
       }
       for (int digits : digit_testcases) {
         if (exponent == 308 && digits >= 179769) break;  // don't overflow!
@@ -1419,20 +1415,17 @@ TEST_F(SimpleDtoaTest, ExhaustiveDoubleToSixDigits) {
       double before = nextafter(d, 0.0);
       double after = nextafter(d, 1.7976931348623157e308);
       char b1[32], b2[kSixDigitsToBufferSize];
-      ABSL_RAW_LOG(
-          ERROR, "%s",
-          absl::StrCat(
-              "Mismatch #", i, "  d=", d, " (", ToNineDigits(d), ")",
-              " sixdigits='", sixdigitsbuf, "'", " snprintf='", snprintfbuf,
-              "'", " Before.=", PerfectDtoa(before), " ",
-              (SixDigitsToBuffer(before, b2), b2),
-              " vs snprintf=", (snprintf(b1, sizeof(b1), "%g", before), b1),
-              " Perfect=", PerfectDtoa(d), " ", (SixDigitsToBuffer(d, b2), b2),
-              " vs snprintf=", (snprintf(b1, sizeof(b1), "%g", d), b1),
-              " After.=.", PerfectDtoa(after), " ",
-              (SixDigitsToBuffer(after, b2), b2),
-              " vs snprintf=", (snprintf(b1, sizeof(b1), "%g", after), b1))
-              .c_str());
+      LOG(ERROR) << "Mismatch #" << i << "  d=" << d << " (" << ToNineDigits(d)
+                 << ") sixdigits='" << sixdigitsbuf << "' snprintf='"
+                 << snprintfbuf << "' Before.=" << PerfectDtoa(before) << " "
+                 << (SixDigitsToBuffer(before, b2), b2) << " vs snprintf="
+                 << (snprintf(b1, sizeof(b1), "%g", before), b1)
+                 << " Perfect=" << PerfectDtoa(d) << " "
+                 << (SixDigitsToBuffer(d, b2), b2)
+                 << " vs snprintf=" << (snprintf(b1, sizeof(b1), "%g", d), b1)
+                 << " After.=." << PerfectDtoa(after) << " "
+                 << (SixDigitsToBuffer(after, b2), b2) << " vs snprintf="
+                 << (snprintf(b1, sizeof(b1), "%g", after), b1);
     }
   }
 }
diff --git a/absl/strings/str_cat.cc b/absl/strings/str_cat.cc
index 114a2ff2..2e49c31b 100644
--- a/absl/strings/str_cat.cc
+++ b/absl/strings/str_cat.cc
@@ -30,55 +30,6 @@
 namespace absl {
 ABSL_NAMESPACE_BEGIN
 
-AlphaNum::AlphaNum(Hex hex) {
-  static_assert(numbers_internal::kFastToBufferSize >= 32,
-                "This function only works when output buffer >= 32 bytes long");
-  char* const end = &digits_[numbers_internal::kFastToBufferSize];
-  auto real_width =
-      absl::numbers_internal::FastHexToBufferZeroPad16(hex.value, end - 16);
-  if (real_width >= hex.width) {
-    piece_ = absl::string_view(end - real_width, real_width);
-  } else {
-    // Pad first 16 chars because FastHexToBufferZeroPad16 pads only to 16 and
-    // max pad width can be up to 20.
-    std::memset(end - 32, hex.fill, 16);
-    // Patch up everything else up to the real_width.
-    std::memset(end - real_width - 16, hex.fill, 16);
-    piece_ = absl::string_view(end - hex.width, hex.width);
-  }
-}
-
-AlphaNum::AlphaNum(Dec dec) {
-  assert(dec.width <= numbers_internal::kFastToBufferSize);
-  char* const end = &digits_[numbers_internal::kFastToBufferSize];
-  char* const minfill = end - dec.width;
-  char* writer = end;
-  uint64_t value = dec.value;
-  bool neg = dec.neg;
-  while (value > 9) {
-    *--writer = '0' + (value % 10);
-    value /= 10;
-  }
-  *--writer = '0' + static_cast<char>(value);
-  if (neg) *--writer = '-';
-
-  ptrdiff_t fillers = writer - minfill;
-  if (fillers > 0) {
-    // Tricky: if the fill character is ' ', then it's <fill><+/-><digits>
-    // But...: if the fill character is '0', then it's <+/-><fill><digits>
-    bool add_sign_again = false;
-    if (neg && dec.fill == '0') {  // If filling with '0',
-      ++writer;                    // ignore the sign we just added
-      add_sign_again = true;       // and re-add the sign later.
-    }
-    writer -= fillers;
-    std::fill_n(writer, fillers, dec.fill);
-    if (add_sign_again) *--writer = '-';
-  }
-
-  piece_ = absl::string_view(writer, static_cast<size_t>(end - writer));
-}
-
 // ----------------------------------------------------------------------
 // StrCat()
 //    This merges the given strings or integers, with no delimiter. This
@@ -195,7 +146,13 @@ void AppendPieces(std::string* dest,
 
 void StrAppend(std::string* dest, const AlphaNum& a) {
   ASSERT_NO_OVERLAP(*dest, a);
-  dest->append(a.data(), a.size());
+  std::string::size_type old_size = dest->size();
+  strings_internal::STLStringResizeUninitializedAmortized(dest,
+                                                          old_size + a.size());
+  char* const begin = &(*dest)[0];
+  char* out = begin + old_size;
+  out = Append(out, a);
+  assert(out == begin + dest->size());
 }
 
 void StrAppend(std::string* dest, const AlphaNum& a, const AlphaNum& b) {
diff --git a/absl/strings/str_cat.h b/absl/strings/str_cat.h
index 730b4d8c..d5f71ff0 100644
--- a/absl/strings/str_cat.h
+++ b/absl/strings/str_cat.h
@@ -87,13 +87,16 @@
 #ifndef ABSL_STRINGS_STR_CAT_H_
 #define ABSL_STRINGS_STR_CAT_H_
 
+#include <algorithm>
 #include <array>
 #include <cstdint>
+#include <cstring>
 #include <string>
 #include <type_traits>
 #include <utility>
 #include <vector>
 
+#include "absl/base/attributes.h"
 #include "absl/base/port.h"
 #include "absl/strings/internal/has_absl_stringify.h"
 #include "absl/strings/internal/stringify_sink.h"
@@ -201,6 +204,27 @@ struct Hex {
   explicit Hex(Pointee* v, PadSpec spec = absl::kNoPad)
       : Hex(spec, reinterpret_cast<uintptr_t>(v)) {}
 
+  template <typename S>
+  friend void AbslStringify(S& sink, Hex hex) {
+    static_assert(
+        numbers_internal::kFastToBufferSize >= 32,
+        "This function only works when output buffer >= 32 bytes long");
+    char buffer[numbers_internal::kFastToBufferSize];
+    char* const end = &buffer[numbers_internal::kFastToBufferSize];
+    auto real_width =
+        absl::numbers_internal::FastHexToBufferZeroPad16(hex.value, end - 16);
+    if (real_width >= hex.width) {
+      sink.Append(absl::string_view(end - real_width, real_width));
+    } else {
+      // Pad first 16 chars because FastHexToBufferZeroPad16 pads only to 16 and
+      // max pad width can be up to 20.
+      std::memset(end - 32, hex.fill, 16);
+      // Patch up everything else up to the real_width.
+      std::memset(end - real_width - 16, hex.fill, 16);
+      sink.Append(absl::string_view(end - hex.width, hex.width));
+    }
+  }
+
  private:
   Hex(PadSpec spec, uint64_t v)
       : value(v),
@@ -235,6 +259,38 @@ struct Dec {
                                              : spec - absl::kZeroPad2 + 2),
         fill(spec >= absl::kSpacePad2 ? ' ' : '0'),
         neg(v < 0) {}
+
+  template <typename S>
+  friend void AbslStringify(S& sink, Dec dec) {
+    assert(dec.width <= numbers_internal::kFastToBufferSize);
+    char buffer[numbers_internal::kFastToBufferSize];
+    char* const end = &buffer[numbers_internal::kFastToBufferSize];
+    char* const minfill = end - dec.width;
+    char* writer = end;
+    uint64_t val = dec.value;
+    while (val > 9) {
+      *--writer = '0' + (val % 10);
+      val /= 10;
+    }
+    *--writer = '0' + static_cast<char>(val);
+    if (dec.neg) *--writer = '-';
+
+    ptrdiff_t fillers = writer - minfill;
+    if (fillers > 0) {
+      // Tricky: if the fill character is ' ', then it's <fill><+/-><digits>
+      // But...: if the fill character is '0', then it's <+/-><fill><digits>
+      bool add_sign_again = false;
+      if (dec.neg && dec.fill == '0') {  // If filling with '0',
+        ++writer;                    // ignore the sign we just added
+        add_sign_again = true;       // and re-add the sign later.
+      }
+      writer -= fillers;
+      std::fill_n(writer, fillers, dec.fill);
+      if (add_sign_again) *--writer = '-';
+    }
+
+    sink.Append(absl::string_view(writer, static_cast<size_t>(end - writer)));
+  }
 };
 
 // -----------------------------------------------------------------------------
@@ -282,28 +338,30 @@ class AlphaNum {
   AlphaNum(double f)  // NOLINT(runtime/explicit)
       : piece_(digits_, numbers_internal::SixDigitsToBuffer(f, digits_)) {}
 
-  AlphaNum(Hex hex);  // NOLINT(runtime/explicit)
-  AlphaNum(Dec dec);  // NOLINT(runtime/explicit)
-
   template <size_t size>
   AlphaNum(  // NOLINT(runtime/explicit)
-      const strings_internal::AlphaNumBuffer<size>& buf)
+      const strings_internal::AlphaNumBuffer<size>& buf
+          ABSL_ATTRIBUTE_LIFETIME_BOUND)
       : piece_(&buf.data[0], buf.size) {}
 
-  AlphaNum(const char* c_str)                     // NOLINT(runtime/explicit)
-      : piece_(NullSafeStringView(c_str)) {}      // NOLINT(runtime/explicit)
-  AlphaNum(absl::string_view pc) : piece_(pc) {}  // NOLINT(runtime/explicit)
+  AlphaNum(const char* c_str  // NOLINT(runtime/explicit)
+               ABSL_ATTRIBUTE_LIFETIME_BOUND)
+      : piece_(NullSafeStringView(c_str)) {}
+  AlphaNum(absl::string_view pc  // NOLINT(runtime/explicit)
+               ABSL_ATTRIBUTE_LIFETIME_BOUND)
+      : piece_(pc) {}
 
   template <typename T, typename = typename std::enable_if<
                             strings_internal::HasAbslStringify<T>::value>::type>
-  AlphaNum(                                         // NOLINT(runtime/explicit)
-      const T& v,                                   // NOLINT(runtime/explicit)
-      strings_internal::StringifySink&& sink = {})  // NOLINT(runtime/explicit)
+  AlphaNum(  // NOLINT(runtime/explicit)
+      const T& v ABSL_ATTRIBUTE_LIFETIME_BOUND,
+      strings_internal::StringifySink&& sink ABSL_ATTRIBUTE_LIFETIME_BOUND = {})
       : piece_(strings_internal::ExtractStringification(sink, v)) {}
 
   template <typename Allocator>
   AlphaNum(  // NOLINT(runtime/explicit)
-      const std::basic_string<char, std::char_traits<char>, Allocator>& str)
+      const std::basic_string<char, std::char_traits<char>, Allocator>& str
+          ABSL_ATTRIBUTE_LIFETIME_BOUND)
       : piece_(str) {}
 
   // Use string literals ":" instead of character literals ':'.
@@ -316,14 +374,24 @@ class AlphaNum {
   const char* data() const { return piece_.data(); }
   absl::string_view Piece() const { return piece_; }
 
-  // Normal enums are already handled by the integer formatters.
-  // This overload matches only scoped enums.
+  // Match unscoped enums.  Use integral promotion so that a `char`-backed
+  // enum becomes a wider integral type AlphaNum will accept.
   template <typename T,
             typename = typename std::enable_if<
-                std::is_enum<T>{} && !std::is_convertible<T, int>{} &&
+                std::is_enum<T>{} && std::is_convertible<T, int>{} &&
                 !strings_internal::HasAbslStringify<T>::value>::type>
   AlphaNum(T e)  // NOLINT(runtime/explicit)
-      : AlphaNum(static_cast<typename std::underlying_type<T>::type>(e)) {}
+      : AlphaNum(+e) {}
+
+  // This overload matches scoped enums.  We must explicitly cast to the
+  // underlying type, but use integral promotion for the same reason as above.
+  template <typename T,
+            typename std::enable_if<
+                std::is_enum<T>{} && !std::is_convertible<T, int>{} &&
+                    !strings_internal::HasAbslStringify<T>::value,
+                char*>::type = nullptr>
+  AlphaNum(T e)  // NOLINT(runtime/explicit)
+      : AlphaNum(+static_cast<typename std::underlying_type<T>::type>(e)) {}
 
   // vector<bool>::reference and const_reference require special help to
   // convert to `AlphaNum` because it requires two user defined conversions.
diff --git a/absl/strings/str_format.h b/absl/strings/str_format.h
index 3536b70e..023e4350 100644
--- a/absl/strings/str_format.h
+++ b/absl/strings/str_format.h
@@ -36,10 +36,12 @@
 //   * `absl::StreamFormat()` to more efficiently write a format string to a
 //     stream, such as`std::cout`.
 //   * `absl::PrintF()`, `absl::FPrintF()` and `absl::SNPrintF()` as
-//     replacements for `std::printf()`, `std::fprintf()` and `std::snprintf()`.
+//     drop-in replacements for `std::printf()`, `std::fprintf()` and
+//     `std::snprintf()`.
 //
-//     Note: a version of `std::sprintf()` is not supported as it is
-//     generally unsafe due to buffer overflows.
+//     Note: An `absl::SPrintF()` drop-in replacement is not supported as it
+//     is generally unsafe due to buffer overflows. Use `absl::StrFormat` which
+//     returns the string as output instead of expecting a pre-allocated buffer.
 //
 // Additionally, you can provide a format string (and its associated arguments)
 // using one of the following abstractions:
@@ -257,6 +259,7 @@ class FormatCountCapture {
 // *   Characters: `char`, `signed char`, `unsigned char`
 // *   Integers: `int`, `short`, `unsigned short`, `unsigned`, `long`,
 //         `unsigned long`, `long long`, `unsigned long long`
+// *   Enums: printed as their underlying integral value
 // *   Floating-point: `float`, `double`, `long double`
 //
 // However, in the `str_format` library, a format conversion specifies a broader
diff --git a/absl/strings/str_format_test.cc b/absl/strings/str_format_test.cc
index 5198fb33..20fd0289 100644
--- a/absl/strings/str_format_test.cc
+++ b/absl/strings/str_format_test.cc
@@ -638,6 +638,8 @@ TEST(StrFormat, BehavesAsDocumented) {
   EXPECT_EQ(StrFormat("%#o", 10), "012");
   EXPECT_EQ(StrFormat("%#x", 15), "0xf");
   EXPECT_EQ(StrFormat("%04d", 8), "0008");
+  EXPECT_EQ(StrFormat("%#04x", 0), "0000");
+  EXPECT_EQ(StrFormat("%#04x", 1), "0x01");
   // Posix positional substitution.
   EXPECT_EQ(absl::StrFormat("%2$s, %3$s, %1$s!", "vici", "veni", "vidi"),
             "veni, vidi, vici!");
diff --git a/absl/strings/str_split.cc b/absl/strings/str_split.cc
index e08c26b6..72ba7c02 100644
--- a/absl/strings/str_split.cc
+++ b/absl/strings/str_split.cc
@@ -60,19 +60,23 @@ absl::string_view GenericFind(absl::string_view text,
 // Finds using absl::string_view::find(), therefore the length of the found
 // delimiter is delimiter.length().
 struct LiteralPolicy {
-  size_t Find(absl::string_view text, absl::string_view delimiter, size_t pos) {
+  static size_t Find(absl::string_view text, absl::string_view delimiter,
+                     size_t pos) {
     return text.find(delimiter, pos);
   }
-  size_t Length(absl::string_view delimiter) { return delimiter.length(); }
+  static size_t Length(absl::string_view delimiter) {
+    return delimiter.length();
+  }
 };
 
 // Finds using absl::string_view::find_first_of(), therefore the length of the
 // found delimiter is 1.
 struct AnyOfPolicy {
-  size_t Find(absl::string_view text, absl::string_view delimiter, size_t pos) {
+  static size_t Find(absl::string_view text, absl::string_view delimiter,
+                     size_t pos) {
     return text.find_first_of(delimiter, pos);
   }
-  size_t Length(absl::string_view /* delimiter */) { return 1; }
+  static size_t Length(absl::string_view /* delimiter */) { return 1; }
 };
 
 }  // namespace
@@ -123,8 +127,7 @@ ByLength::ByLength(ptrdiff_t length) : length_(length) {
   ABSL_RAW_CHECK(length > 0, "");
 }
 
-absl::string_view ByLength::Find(absl::string_view text,
-                                      size_t pos) const {
+absl::string_view ByLength::Find(absl::string_view text, size_t pos) const {
   pos = std::min(pos, text.size());  // truncate `pos`
   absl::string_view substr = text.substr(pos);
   // If the string is shorter than the chunk size we say we
diff --git a/absl/strings/string_view.cc b/absl/strings/string_view.cc
index e2261625..f20ff530 100644
--- a/absl/strings/string_view.cc
+++ b/absl/strings/string_view.cc
@@ -21,12 +21,35 @@
 #include <cstring>
 #include <ostream>
 
-#include "absl/strings/internal/memutil.h"
-
 namespace absl {
 ABSL_NAMESPACE_BEGIN
 
 namespace {
+
+// This is significantly faster for case-sensitive matches with very
+// few possible matches.
+const char* memmatch(const char* phaystack, size_t haylen, const char* pneedle,
+                     size_t neelen) {
+  if (0 == neelen) {
+    return phaystack;  // even if haylen is 0
+  }
+  if (haylen < neelen) return nullptr;
+
+  const char* match;
+  const char* hayend = phaystack + haylen - neelen + 1;
+  // A static cast is used here to work around the fact that memchr returns
+  // a void* on Posix-compliant systems and const void* on Windows.
+  while (
+      (match = static_cast<const char*>(memchr(
+           phaystack, pneedle[0], static_cast<size_t>(hayend - phaystack))))) {
+    if (memcmp(match, pneedle, neelen) == 0)
+      return match;
+    else
+      phaystack = match + 1;
+  }
+  return nullptr;
+}
+
 void WritePadding(std::ostream& o, size_t pad) {
   char fill_buf[32];
   memset(fill_buf, o.fill(), sizeof(fill_buf));
@@ -84,8 +107,7 @@ string_view::size_type string_view::find(string_view s,
     if (empty() && pos == 0 && s.empty()) return 0;
     return npos;
   }
-  const char* result =
-      strings_internal::memmatch(ptr_ + pos, length_ - pos, s.ptr_, s.length_);
+  const char* result = memmatch(ptr_ + pos, length_ - pos, s.ptr_, s.length_);
   return result ? static_cast<size_type>(result - ptr_) : npos;
 }
 
diff --git a/absl/synchronization/BUILD.bazel b/absl/synchronization/BUILD.bazel
index ccaee796..0ca94e01 100644
--- a/absl/synchronization/BUILD.bazel
+++ b/absl/synchronization/BUILD.bazel
@@ -21,7 +21,7 @@ load(
     "ABSL_TEST_COPTS",
 )
 
-package(default_visibility = ["//visibility:public"])
+package(default_visibility = ["//visibility:private"])
 
 licenses(["notice"])
 
@@ -38,9 +38,6 @@ cc_library(
         "//conditions:default": [],
     }),
     linkopts = ABSL_DEFAULT_LINKOPTS,
-    visibility = [
-        "//absl:__subpackages__",
-    ],
     deps = [
         "//absl/base",
         "//absl/base:base_internal",
@@ -53,27 +50,49 @@ cc_library(
 
 cc_library(
     name = "kernel_timeout_internal",
+    srcs = ["internal/kernel_timeout.cc"],
     hdrs = ["internal/kernel_timeout.h"],
     copts = ABSL_DEFAULT_COPTS,
     linkopts = ABSL_DEFAULT_LINKOPTS,
     visibility = [
-        "//absl/synchronization:__pkg__",
     ],
     deps = [
+        "//absl/base",
+        "//absl/base:config",
         "//absl/base:core_headers",
         "//absl/base:raw_logging_internal",
         "//absl/time",
     ],
 )
 
+cc_test(
+    name = "kernel_timeout_internal_test",
+    srcs = ["internal/kernel_timeout_test.cc"],
+    copts = ABSL_TEST_COPTS,
+    flaky = 1,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":kernel_timeout_internal",
+        "//absl/base:config",
+        "//absl/random",
+        "//absl/time",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
 cc_library(
     name = "synchronization",
     srcs = [
         "barrier.cc",
         "blocking_counter.cc",
         "internal/create_thread_identity.cc",
+        "internal/futex_waiter.cc",
         "internal/per_thread_sem.cc",
-        "internal/waiter.cc",
+        "internal/pthread_waiter.cc",
+        "internal/sem_waiter.cc",
+        "internal/stdcpp_waiter.cc",
+        "internal/waiter_base.cc",
+        "internal/win32_waiter.cc",
         "mutex.cc",
         "notification.cc",
     ],
@@ -82,8 +101,14 @@ cc_library(
         "blocking_counter.h",
         "internal/create_thread_identity.h",
         "internal/futex.h",
+        "internal/futex_waiter.h",
         "internal/per_thread_sem.h",
+        "internal/pthread_waiter.h",
+        "internal/sem_waiter.h",
+        "internal/stdcpp_waiter.h",
         "internal/waiter.h",
+        "internal/waiter_base.h",
+        "internal/win32_waiter.h",
         "mutex.h",
         "notification.h",
     ],
@@ -94,11 +119,12 @@ cc_library(
         "//absl:wasm": [],
         "//conditions:default": ["-pthread"],
     }) + ABSL_DEFAULT_LINKOPTS,
+    visibility = ["//visibility:public"],
     deps = [
         ":graphcycles_internal",
         ":kernel_timeout_internal",
-        "//absl/base:atomic_hook",
         "//absl/base",
+        "//absl/base:atomic_hook",
         "//absl/base:base_internal",
         "//absl/base:config",
         "//absl/base:core_headers",
@@ -120,7 +146,7 @@ cc_test(
     copts = ABSL_TEST_COPTS,
     linkopts = ABSL_DEFAULT_LINKOPTS,
     tags = [
-        "no_test_wasm",
+        "no_test_wasm",  # b/122473323
     ],
     deps = [
         ":synchronization",
@@ -136,7 +162,7 @@ cc_test(
     copts = ABSL_TEST_COPTS,
     linkopts = ABSL_DEFAULT_LINKOPTS,
     tags = [
-        "no_test_wasm",
+        "no_test_wasm",  # b/122473323
     ],
     deps = [
         ":synchronization",
@@ -152,7 +178,6 @@ cc_binary(
     copts = ABSL_TEST_COPTS,
     linkopts = ABSL_DEFAULT_LINKOPTS,
     tags = ["benchmark"],
-    visibility = ["//visibility:private"],
     deps = [
         ":synchronization",
         ":thread_pool",
@@ -169,7 +194,8 @@ cc_test(
     deps = [
         ":graphcycles_internal",
         "//absl/base:core_headers",
-        "//absl/base:raw_logging_internal",
+        "//absl/log",
+        "//absl/log:check",
         "@com_google_googletest//:gtest_main",
     ],
 )
@@ -209,6 +235,7 @@ cc_test(
     size = "large",
     srcs = ["mutex_test.cc"],
     copts = ABSL_TEST_COPTS,
+    flaky = 1,
     linkopts = ABSL_DEFAULT_LINKOPTS,
     shard_count = 25,
     deps = [
@@ -217,7 +244,8 @@ cc_test(
         "//absl/base",
         "//absl/base:config",
         "//absl/base:core_headers",
-        "//absl/base:raw_logging_internal",
+        "//absl/log",
+        "//absl/log:check",
         "//absl/memory",
         "//absl/time",
         "@com_google_googletest//:gtest_main",
@@ -243,7 +271,6 @@ cc_library(
     copts = ABSL_TEST_COPTS,
     linkopts = ABSL_DEFAULT_LINKOPTS,
     visibility = [
-        "//absl/synchronization:__pkg__",
     ],
     deps = [
         ":synchronization",
@@ -260,7 +287,6 @@ cc_binary(
     testonly = 1,
     copts = ABSL_DEFAULT_COPTS,
     linkopts = ABSL_DEFAULT_LINKOPTS,
-    visibility = ["//visibility:private"],
     deps = [
         ":mutex_benchmark_common",
     ],
@@ -271,6 +297,7 @@ cc_test(
     size = "small",
     srcs = ["notification_test.cc"],
     copts = ABSL_TEST_COPTS,
+    flaky = 1,
     linkopts = ABSL_DEFAULT_LINKOPTS,
     tags = ["no_test_lexan"],
     deps = [
@@ -286,6 +313,8 @@ cc_library(
     srcs = ["internal/per_thread_sem_test.cc"],
     copts = ABSL_TEST_COPTS,
     linkopts = ABSL_DEFAULT_LINKOPTS,
+    visibility = [
+    ],
     deps = [
         ":synchronization",
         "//absl/base",
@@ -315,6 +344,23 @@ cc_test(
 )
 
 cc_test(
+    name = "waiter_test",
+    srcs = ["internal/waiter_test.cc"],
+    copts = ABSL_TEST_COPTS,
+    flaky = 1,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":kernel_timeout_internal",
+        ":synchronization",
+        ":thread_pool",
+        "//absl/base:config",
+        "//absl/random",
+        "//absl/time",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_test(
     name = "lifetime_test",
     srcs = [
         "lifetime_test.cc",
@@ -328,6 +374,6 @@ cc_test(
     deps = [
         ":synchronization",
         "//absl/base:core_headers",
-        "//absl/base:raw_logging_internal",
+        "//absl/log:check",
     ],
 )
diff --git a/absl/synchronization/CMakeLists.txt b/absl/synchronization/CMakeLists.txt
index f64653bb..a0f64e5c 100644
--- a/absl/synchronization/CMakeLists.txt
+++ b/absl/synchronization/CMakeLists.txt
@@ -39,14 +39,33 @@ absl_cc_library(
     kernel_timeout_internal
   HDRS
     "internal/kernel_timeout.h"
+  SRCS
+    "internal/kernel_timeout.cc"
   COPTS
     ${ABSL_DEFAULT_COPTS}
   DEPS
+    absl::base
+    absl::config
     absl::core_headers
     absl::raw_logging_internal
     absl::time
 )
 
+absl_cc_test(
+  NAME
+    kernel_timeout_internal_test
+  SRCS
+    "internal/kernel_timeout_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  DEPS
+    absl::kernel_timeout_internal
+    absl::config
+    absl::random_random
+    absl::time
+    GTest::gmock_main
+)
+
 absl_cc_library(
   NAME
     synchronization
@@ -55,16 +74,27 @@ absl_cc_library(
     "blocking_counter.h"
     "internal/create_thread_identity.h"
     "internal/futex.h"
+    "internal/futex_waiter.h"
     "internal/per_thread_sem.h"
+    "internal/pthread_waiter.h"
+    "internal/sem_waiter.h"
+    "internal/stdcpp_waiter.h"
     "internal/waiter.h"
+    "internal/waiter_base.h"
+    "internal/win32_waiter.h"
     "mutex.h"
     "notification.h"
   SRCS
     "barrier.cc"
     "blocking_counter.cc"
     "internal/create_thread_identity.cc"
+    "internal/futex_waiter.cc"
     "internal/per_thread_sem.cc"
-    "internal/waiter.cc"
+    "internal/pthread_waiter.cc"
+    "internal/sem_waiter.cc"
+    "internal/stdcpp_waiter.cc"
+    "internal/waiter_base.cc"
+    "internal/win32_waiter.cc"
     "notification.cc"
     "mutex.cc"
   COPTS
@@ -121,9 +151,10 @@ absl_cc_test(
   COPTS
     ${ABSL_TEST_COPTS}
   DEPS
-    absl::graphcycles_internal
+    absl::check
     absl::core_headers
-    absl::raw_logging_internal
+    absl::graphcycles_internal
+    absl::log
     GTest::gmock_main
 )
 
@@ -153,10 +184,11 @@ absl_cc_test(
     absl::synchronization
     absl::thread_pool
     absl::base
+    absl::check
     absl::config
     absl::core_headers
+    absl::log
     absl::memory
-    absl::raw_logging_internal
     absl::time
     GTest::gmock_main
 )
@@ -223,6 +255,23 @@ absl_cc_test(
 
 absl_cc_test(
   NAME
+    waiter_test
+  SRCS
+    "internal/waiter_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  DEPS
+    absl::config
+    absl::kernel_timeout_internal
+    absl::random_random
+    absl::synchronization
+    absl::thread_pool
+    absl::time
+    GTest::gmock_main
+)
+
+absl_cc_test(
+  NAME
     lifetime_test
   SRCS
     "lifetime_test.cc"
@@ -231,5 +280,5 @@ absl_cc_test(
   DEPS
     absl::synchronization
     absl::core_headers
-    absl::raw_logging_internal
+    absl::check
 )
diff --git a/absl/synchronization/internal/create_thread_identity.cc b/absl/synchronization/internal/create_thread_identity.cc
index 44e6129b..eacaa28d 100644
--- a/absl/synchronization/internal/create_thread_identity.cc
+++ b/absl/synchronization/internal/create_thread_identity.cc
@@ -13,10 +13,12 @@
 // limitations under the License.
 
 #include <stdint.h>
+
 #include <new>
 
 // This file is a no-op if the required LowLevelAlloc support is missing.
 #include "absl/base/internal/low_level_alloc.h"
+#include "absl/synchronization/internal/waiter.h"
 #ifndef ABSL_LOW_LEVEL_ALLOC_MISSING
 
 #include <string.h>
@@ -71,6 +73,9 @@ static intptr_t RoundUp(intptr_t addr, intptr_t align) {
 
 void OneTimeInitThreadIdentity(base_internal::ThreadIdentity* identity) {
   PerThreadSem::Init(identity);
+  identity->ticker.store(0, std::memory_order_relaxed);
+  identity->wait_start.store(0, std::memory_order_relaxed);
+  identity->is_idle.store(false, std::memory_order_relaxed);
 }
 
 static void ResetThreadIdentityBetweenReuse(
diff --git a/absl/synchronization/internal/futex.h b/absl/synchronization/internal/futex.h
index cb97da09..573c01b7 100644
--- a/absl/synchronization/internal/futex.h
+++ b/absl/synchronization/internal/futex.h
@@ -16,9 +16,7 @@
 
 #include "absl/base/config.h"
 
-#ifdef _WIN32
-#include <windows.h>
-#else
+#ifndef _WIN32
 #include <sys/time.h>
 #include <unistd.h>
 #endif
@@ -34,6 +32,7 @@
 
 #include <atomic>
 #include <cstdint>
+#include <limits>
 
 #include "absl/base/optimization.h"
 #include "absl/synchronization/internal/kernel_timeout.h"
@@ -81,51 +80,64 @@ namespace synchronization_internal {
 
 #if defined(SYS_futex_time64) && !defined(SYS_futex)
 #define SYS_futex SYS_futex_time64
+using FutexTimespec = struct timespec;
+#else
+// Some libc implementations have switched to an unconditional 64-bit `time_t`
+// definition. This means that `struct timespec` may not match the layout
+// expected by the kernel ABI on 32-bit platforms. So we define the
+// FutexTimespec that matches the kernel timespec definition. It should be safe
+// to use this struct for 64-bit userspace builds too, since it will use another
+// SYS_futex kernel call with 64-bit tv_sec inside timespec.
+struct FutexTimespec {
+  long tv_sec;   // NOLINT
+  long tv_nsec;  // NOLINT
+};
 #endif
 
 class FutexImpl {
  public:
-  static int WaitUntil(std::atomic<int32_t> *v, int32_t val,
-                       KernelTimeout t) {
-    long err = 0;  // NOLINT(runtime/int)
-    if (t.has_timeout()) {
-      // https://locklessinc.com/articles/futex_cheat_sheet/
-      // Unlike FUTEX_WAIT, FUTEX_WAIT_BITSET uses absolute time.
-      struct timespec abs_timeout = t.MakeAbsTimespec();
-      // Atomically check that the futex value is still 0, and if it
-      // is, sleep until abs_timeout or until woken by FUTEX_WAKE.
-      err = syscall(
-          SYS_futex, reinterpret_cast<int32_t *>(v),
-          FUTEX_WAIT_BITSET | FUTEX_PRIVATE_FLAG | FUTEX_CLOCK_REALTIME, val,
-          &abs_timeout, nullptr, FUTEX_BITSET_MATCH_ANY);
-    } else {
-      // Atomically check that the futex value is still 0, and if it
-      // is, sleep until woken by FUTEX_WAKE.
-      err = syscall(SYS_futex, reinterpret_cast<int32_t *>(v),
-                    FUTEX_WAIT | FUTEX_PRIVATE_FLAG, val, nullptr);
-    }
-    if (ABSL_PREDICT_FALSE(err != 0)) {
+  // Atomically check that `*v == val`, and if it is, then sleep until the until
+  // woken by `Wake()`.
+  static int Wait(std::atomic<int32_t>* v, int32_t val) {
+    return WaitAbsoluteTimeout(v, val, nullptr);
+  }
+
+  // Atomically check that `*v == val`, and if it is, then sleep until
+  // CLOCK_REALTIME reaches `*abs_timeout`, or until woken by `Wake()`.
+  static int WaitAbsoluteTimeout(std::atomic<int32_t>* v, int32_t val,
+                                 const struct timespec* abs_timeout) {
+    FutexTimespec ts;
+    // https://locklessinc.com/articles/futex_cheat_sheet/
+    // Unlike FUTEX_WAIT, FUTEX_WAIT_BITSET uses absolute time.
+    auto err = syscall(
+        SYS_futex, reinterpret_cast<int32_t*>(v),
+        FUTEX_WAIT_BITSET | FUTEX_PRIVATE_FLAG | FUTEX_CLOCK_REALTIME, val,
+        ToFutexTimespec(abs_timeout, &ts), nullptr, FUTEX_BITSET_MATCH_ANY);
+    if (err != 0) {
       return -errno;
     }
     return 0;
   }
 
-  static int WaitBitsetAbsoluteTimeout(std::atomic<int32_t> *v, int32_t val,
-                                       int32_t bits,
-                                       const struct timespec *abstime) {
-    // NOLINTNEXTLINE(runtime/int)
-    long err = syscall(SYS_futex, reinterpret_cast<int32_t*>(v),
-                       FUTEX_WAIT_BITSET | FUTEX_PRIVATE_FLAG, val, abstime,
-                       nullptr, bits);
-    if (ABSL_PREDICT_FALSE(err != 0)) {
+  // Atomically check that `*v == val`, and if it is, then sleep until
+  // `*rel_timeout` has elapsed, or until woken by `Wake()`.
+  static int WaitRelativeTimeout(std::atomic<int32_t>* v, int32_t val,
+                                 const struct timespec* rel_timeout) {
+    FutexTimespec ts;
+    // Atomically check that the futex value is still 0, and if it
+    // is, sleep until abs_timeout or until woken by FUTEX_WAKE.
+    auto err =
+        syscall(SYS_futex, reinterpret_cast<int32_t*>(v), FUTEX_PRIVATE_FLAG,
+                val, ToFutexTimespec(rel_timeout, &ts));
+    if (err != 0) {
       return -errno;
     }
     return 0;
   }
 
-  static int Wake(std::atomic<int32_t> *v, int32_t count) {
-    // NOLINTNEXTLINE(runtime/int)
-    long err = syscall(SYS_futex, reinterpret_cast<int32_t*>(v),
+  // Wakes at most `count` waiters that have entered the sleep state on `v`.
+  static int Wake(std::atomic<int32_t>* v, int32_t count) {
+    auto err = syscall(SYS_futex, reinterpret_cast<int32_t*>(v),
                        FUTEX_WAKE | FUTEX_PRIVATE_FLAG, count);
     if (ABSL_PREDICT_FALSE(err < 0)) {
       return -errno;
@@ -133,16 +145,24 @@ class FutexImpl {
     return 0;
   }
 
-  // FUTEX_WAKE_BITSET
-  static int WakeBitset(std::atomic<int32_t> *v, int32_t count, int32_t bits) {
-    // NOLINTNEXTLINE(runtime/int)
-    long err = syscall(SYS_futex, reinterpret_cast<int32_t*>(v),
-                       FUTEX_WAKE_BITSET | FUTEX_PRIVATE_FLAG, count, nullptr,
-                       nullptr, bits);
-    if (ABSL_PREDICT_FALSE(err < 0)) {
-      return -errno;
+ private:
+  static FutexTimespec* ToFutexTimespec(const struct timespec* userspace_ts,
+                                        FutexTimespec* futex_ts) {
+    if (userspace_ts == nullptr) {
+      return nullptr;
     }
-    return 0;
+
+    using FutexSeconds = decltype(futex_ts->tv_sec);
+    using FutexNanoseconds = decltype(futex_ts->tv_nsec);
+
+    constexpr auto kMaxSeconds{(std::numeric_limits<FutexSeconds>::max)()};
+    if (userspace_ts->tv_sec > kMaxSeconds) {
+      futex_ts->tv_sec = kMaxSeconds;
+    } else {
+      futex_ts->tv_sec = static_cast<FutexSeconds>(userspace_ts->tv_sec);
+    }
+    futex_ts->tv_nsec = static_cast<FutexNanoseconds>(userspace_ts->tv_nsec);
+    return futex_ts;
   }
 };
 
diff --git a/absl/synchronization/internal/futex_waiter.cc b/absl/synchronization/internal/futex_waiter.cc
new file mode 100644
index 00000000..87eb3b23
--- /dev/null
+++ b/absl/synchronization/internal/futex_waiter.cc
@@ -0,0 +1,111 @@
+// Copyright 2023 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/synchronization/internal/futex_waiter.h"
+
+#ifdef ABSL_INTERNAL_HAVE_FUTEX_WAITER
+
+#include <atomic>
+#include <cstdint>
+#include <cerrno>
+
+#include "absl/base/config.h"
+#include "absl/base/internal/raw_logging.h"
+#include "absl/base/internal/thread_identity.h"
+#include "absl/base/optimization.h"
+#include "absl/synchronization/internal/kernel_timeout.h"
+#include "absl/synchronization/internal/futex.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace synchronization_internal {
+
+#ifdef ABSL_INTERNAL_NEED_REDUNDANT_CONSTEXPR_DECL
+constexpr char FutexWaiter::kName[];
+#endif
+
+int FutexWaiter::WaitUntil(std::atomic<int32_t>* v, int32_t val,
+                           KernelTimeout t) {
+#ifdef CLOCK_MONOTONIC
+  constexpr bool kHasClockMonotonic = true;
+#else
+  constexpr bool kHasClockMonotonic = false;
+#endif
+
+  // We can't call Futex::WaitUntil() here because the prodkernel implementation
+  // does not know about KernelTimeout::SupportsSteadyClock().
+  if (!t.has_timeout()) {
+    return Futex::Wait(v, val);
+  } else if (kHasClockMonotonic && KernelTimeout::SupportsSteadyClock() &&
+             t.is_relative_timeout()) {
+    auto rel_timespec = t.MakeRelativeTimespec();
+    return Futex::WaitRelativeTimeout(v, val, &rel_timespec);
+  } else {
+    auto abs_timespec = t.MakeAbsTimespec();
+    return Futex::WaitAbsoluteTimeout(v, val, &abs_timespec);
+  }
+}
+
+bool FutexWaiter::Wait(KernelTimeout t) {
+  // Loop until we can atomically decrement futex from a positive
+  // value, waiting on a futex while we believe it is zero.
+  // Note that, since the thread ticker is just reset, we don't need to check
+  // whether the thread is idle on the very first pass of the loop.
+  bool first_pass = true;
+  while (true) {
+    int32_t x = futex_.load(std::memory_order_relaxed);
+    while (x != 0) {
+      if (!futex_.compare_exchange_weak(x, x - 1,
+                                        std::memory_order_acquire,
+                                        std::memory_order_relaxed)) {
+        continue;  // Raced with someone, retry.
+      }
+      return true;  // Consumed a wakeup, we are done.
+    }
+
+    if (!first_pass) MaybeBecomeIdle();
+    const int err = WaitUntil(&futex_, 0, t);
+    if (err != 0) {
+      if (err == -EINTR || err == -EWOULDBLOCK) {
+        // Do nothing, the loop will retry.
+      } else if (err == -ETIMEDOUT) {
+        return false;
+      } else {
+        ABSL_RAW_LOG(FATAL, "Futex operation failed with error %d\n", err);
+      }
+    }
+    first_pass = false;
+  }
+}
+
+void FutexWaiter::Post() {
+  if (futex_.fetch_add(1, std::memory_order_release) == 0) {
+    // We incremented from 0, need to wake a potential waiter.
+    Poke();
+  }
+}
+
+void FutexWaiter::Poke() {
+  // Wake one thread waiting on the futex.
+  const int err = Futex::Wake(&futex_, 1);
+  if (ABSL_PREDICT_FALSE(err < 0)) {
+    ABSL_RAW_LOG(FATAL, "Futex operation failed with error %d\n", err);
+  }
+}
+
+}  // namespace synchronization_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_INTERNAL_HAVE_FUTEX_WAITER
diff --git a/absl/synchronization/internal/futex_waiter.h b/absl/synchronization/internal/futex_waiter.h
new file mode 100644
index 00000000..11dfa93b
--- /dev/null
+++ b/absl/synchronization/internal/futex_waiter.h
@@ -0,0 +1,63 @@
+// Copyright 2023 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+#ifndef ABSL_SYNCHRONIZATION_INTERNAL_FUTEX_WAITER_H_
+#define ABSL_SYNCHRONIZATION_INTERNAL_FUTEX_WAITER_H_
+
+#include <atomic>
+#include <cstdint>
+
+#include "absl/base/config.h"
+#include "absl/synchronization/internal/kernel_timeout.h"
+#include "absl/synchronization/internal/futex.h"
+#include "absl/synchronization/internal/waiter_base.h"
+
+#ifdef ABSL_INTERNAL_HAVE_FUTEX
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace synchronization_internal {
+
+#define ABSL_INTERNAL_HAVE_FUTEX_WAITER 1
+
+class FutexWaiter : public WaiterCrtp<FutexWaiter> {
+ public:
+  FutexWaiter() : futex_(0) {}
+
+  bool Wait(KernelTimeout t);
+  void Post();
+  void Poke();
+
+  static constexpr char kName[] = "FutexWaiter";
+
+ private:
+  // Atomically check that `*v == val`, and if it is, then sleep until the
+  // timeout `t` has been reached, or until woken by `Wake()`.
+  static int WaitUntil(std::atomic<int32_t>* v, int32_t val,
+                       KernelTimeout t);
+
+  // Futexes are defined by specification to be 32-bits.
+  // Thus std::atomic<int32_t> must be just an int32_t with lockfree methods.
+  std::atomic<int32_t> futex_;
+  static_assert(sizeof(int32_t) == sizeof(futex_), "Wrong size for futex");
+};
+
+}  // namespace synchronization_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_INTERNAL_HAVE_FUTEX
+
+#endif  // ABSL_SYNCHRONIZATION_INTERNAL_FUTEX_WAITER_H_
diff --git a/absl/synchronization/internal/graphcycles.cc b/absl/synchronization/internal/graphcycles.cc
index feec4581..39b18482 100644
--- a/absl/synchronization/internal/graphcycles.cc
+++ b/absl/synchronization/internal/graphcycles.cc
@@ -37,6 +37,7 @@
 
 #include <algorithm>
 #include <array>
+#include <cinttypes>
 #include <limits>
 #include "absl/base/internal/hide_ptr.h"
 #include "absl/base/internal/raw_logging.h"
@@ -114,7 +115,7 @@ class Vec {
     if (src->ptr_ == src->space_) {
       // Need to actually copy
       resize(src->size_);
-      std::copy(src->ptr_, src->ptr_ + src->size_, ptr_);
+      std::copy_n(src->ptr_, src->size_, ptr_);
       src->size_ = 0;
     } else {
       Discard();
@@ -148,7 +149,7 @@ class Vec {
     size_t request = static_cast<size_t>(capacity_) * sizeof(T);
     T* copy = static_cast<T*>(
         base_internal::LowLevelAlloc::AllocWithArena(request, arena));
-    std::copy(ptr_, ptr_ + size_, copy);
+    std::copy_n(ptr_, size_, copy);
     Discard();
     ptr_ = copy;
   }
@@ -386,19 +387,22 @@ bool GraphCycles::CheckInvariants() const {
     Node* nx = r->nodes_[x];
     void* ptr = base_internal::UnhidePtr<void>(nx->masked_ptr);
     if (ptr != nullptr && static_cast<uint32_t>(r->ptrmap_.Find(ptr)) != x) {
-      ABSL_RAW_LOG(FATAL, "Did not find live node in hash table %u %p", x, ptr);
+      ABSL_RAW_LOG(FATAL, "Did not find live node in hash table %" PRIu32 " %p",
+                   x, ptr);
     }
     if (nx->visited) {
-      ABSL_RAW_LOG(FATAL, "Did not clear visited marker on node %u", x);
+      ABSL_RAW_LOG(FATAL, "Did not clear visited marker on node %" PRIu32, x);
     }
     if (!ranks.insert(nx->rank)) {
-      ABSL_RAW_LOG(FATAL, "Duplicate occurrence of rank %d", nx->rank);
+      ABSL_RAW_LOG(FATAL, "Duplicate occurrence of rank %" PRId32, nx->rank);
     }
     HASH_FOR_EACH(y, nx->out) {
       Node* ny = r->nodes_[static_cast<uint32_t>(y)];
       if (nx->rank >= ny->rank) {
-        ABSL_RAW_LOG(FATAL, "Edge %u->%d has bad rank assignment %d->%d", x, y,
-                     nx->rank, ny->rank);
+        ABSL_RAW_LOG(FATAL,
+                     "Edge %" PRIu32 " ->%" PRId32
+                     " has bad rank assignment %" PRId32 "->%" PRId32,
+                     x, y, nx->rank, ny->rank);
       }
     }
   }
diff --git a/absl/synchronization/internal/graphcycles_test.cc b/absl/synchronization/internal/graphcycles_test.cc
index 74eaffe7..3c6ef798 100644
--- a/absl/synchronization/internal/graphcycles_test.cc
+++ b/absl/synchronization/internal/graphcycles_test.cc
@@ -21,8 +21,9 @@
 #include <vector>
 
 #include "gtest/gtest.h"
-#include "absl/base/internal/raw_logging.h"
 #include "absl/base/macros.h"
+#include "absl/log/check.h"
+#include "absl/log/log.h"
 
 namespace absl {
 ABSL_NAMESPACE_BEGIN
@@ -65,51 +66,51 @@ static bool IsReachable(Edges *edges, int from, int to,
 }
 
 static void PrintEdges(Edges *edges) {
-  ABSL_RAW_LOG(INFO, "EDGES (%zu)", edges->size());
+  LOG(INFO) << "EDGES (" << edges->size() << ")";
   for (const auto &edge : *edges) {
     int a = edge.from;
     int b = edge.to;
-    ABSL_RAW_LOG(INFO, "%d %d", a, b);
+    LOG(INFO) << a << " " << b;
   }
-  ABSL_RAW_LOG(INFO, "---");
+  LOG(INFO) << "---";
 }
 
 static void PrintGCEdges(Nodes *nodes, const IdMap &id, GraphCycles *gc) {
-  ABSL_RAW_LOG(INFO, "GC EDGES");
+  LOG(INFO) << "GC EDGES";
   for (int a : *nodes) {
     for (int b : *nodes) {
       if (gc->HasEdge(Get(id, a), Get(id, b))) {
-        ABSL_RAW_LOG(INFO, "%d %d", a, b);
+        LOG(INFO) << a << " " << b;
       }
     }
   }
-  ABSL_RAW_LOG(INFO, "---");
+  LOG(INFO) << "---";
 }
 
 static void PrintTransitiveClosure(Nodes *nodes, Edges *edges) {
-  ABSL_RAW_LOG(INFO, "Transitive closure");
+  LOG(INFO) << "Transitive closure";
   for (int a : *nodes) {
     for (int b : *nodes) {
       std::unordered_set<int> seen;
       if (IsReachable(edges, a, b, &seen)) {
-        ABSL_RAW_LOG(INFO, "%d %d", a, b);
+        LOG(INFO) << a << " " << b;
       }
     }
   }
-  ABSL_RAW_LOG(INFO, "---");
+  LOG(INFO) << "---";
 }
 
 static void PrintGCTransitiveClosure(Nodes *nodes, const IdMap &id,
                                      GraphCycles *gc) {
-  ABSL_RAW_LOG(INFO, "GC Transitive closure");
+  LOG(INFO) << "GC Transitive closure";
   for (int a : *nodes) {
     for (int b : *nodes) {
       if (gc->IsReachable(Get(id, a), Get(id, b))) {
-        ABSL_RAW_LOG(INFO, "%d %d", a, b);
+        LOG(INFO) << a << " " << b;
       }
     }
   }
-  ABSL_RAW_LOG(INFO, "---");
+  LOG(INFO) << "---";
 }
 
 static void CheckTransitiveClosure(Nodes *nodes, Edges *edges, const IdMap &id,
@@ -125,9 +126,8 @@ static void CheckTransitiveClosure(Nodes *nodes, Edges *edges, const IdMap &id,
         PrintGCEdges(nodes, id, gc);
         PrintTransitiveClosure(nodes, edges);
         PrintGCTransitiveClosure(nodes, id, gc);
-        ABSL_RAW_LOG(FATAL, "gc_reachable %s reachable %s a %d b %d",
-                     gc_reachable ? "true" : "false",
-                     reachable ? "true" : "false", a, b);
+        LOG(FATAL) << "gc_reachable " << gc_reachable << " reachable "
+                   << reachable << " a " << a << " b " << b;
       }
     }
   }
@@ -142,7 +142,7 @@ static void CheckEdges(Nodes *nodes, Edges *edges, const IdMap &id,
     if (!gc->HasEdge(Get(id, a), Get(id, b))) {
       PrintEdges(edges);
       PrintGCEdges(nodes, id, gc);
-      ABSL_RAW_LOG(FATAL, "!gc->HasEdge(%d, %d)", a, b);
+      LOG(FATAL) << "!gc->HasEdge(" << a << ", " << b << ")";
     }
   }
   for (const auto &a : *nodes) {
@@ -155,13 +155,12 @@ static void CheckEdges(Nodes *nodes, Edges *edges, const IdMap &id,
   if (count != edges->size()) {
     PrintEdges(edges);
     PrintGCEdges(nodes, id, gc);
-    ABSL_RAW_LOG(FATAL, "edges->size() %zu  count %d", edges->size(), count);
+    LOG(FATAL) << "edges->size() " << edges->size() << "  count " << count;
   }
 }
 
 static void CheckInvariants(const GraphCycles &gc) {
-  if (ABSL_PREDICT_FALSE(!gc.CheckInvariants()))
-    ABSL_RAW_LOG(FATAL, "CheckInvariants");
+  CHECK(gc.CheckInvariants()) << "CheckInvariants";
 }
 
 // Returns the index of a randomly chosen node in *nodes.
@@ -309,7 +308,7 @@ TEST(GraphCycles, RandomizedTest) {
       break;
 
     default:
-      ABSL_RAW_LOG(FATAL, "op %d", op);
+      LOG(FATAL) << "op " << op;
     }
 
     // Very rarely, test graph expansion by adding then removing many nodes.
diff --git a/absl/synchronization/internal/kernel_timeout.cc b/absl/synchronization/internal/kernel_timeout.cc
new file mode 100644
index 00000000..48ea6287
--- /dev/null
+++ b/absl/synchronization/internal/kernel_timeout.cc
@@ -0,0 +1,225 @@
+// Copyright 2023 The Abseil Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/synchronization/internal/kernel_timeout.h"
+
+#ifndef _WIN32
+#include <sys/types.h>
+#endif
+
+#include <algorithm>
+#include <chrono>  // NOLINT(build/c++11)
+#include <cstdint>
+#include <cstdlib>
+#include <cstring>
+#include <ctime>
+#include <limits>
+
+#include "absl/base/attributes.h"
+#include "absl/base/call_once.h"
+#include "absl/base/config.h"
+#include "absl/time/time.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace synchronization_internal {
+
+#ifdef ABSL_INTERNAL_NEED_REDUNDANT_CONSTEXPR_DECL
+constexpr uint64_t KernelTimeout::kNoTimeout;
+constexpr int64_t KernelTimeout::kMaxNanos;
+#endif
+
+int64_t KernelTimeout::SteadyClockNow() {
+  if (!SupportsSteadyClock()) {
+    return absl::GetCurrentTimeNanos();
+  }
+  return std::chrono::duration_cast<std::chrono::nanoseconds>(
+             std::chrono::steady_clock::now().time_since_epoch())
+      .count();
+}
+
+KernelTimeout::KernelTimeout(absl::Time t) {
+  // `absl::InfiniteFuture()` is a common "no timeout" value and cheaper to
+  // compare than convert.
+  if (t == absl::InfiniteFuture()) {
+    rep_ = kNoTimeout;
+    return;
+  }
+
+  int64_t unix_nanos = absl::ToUnixNanos(t);
+
+  // A timeout that lands before the unix epoch is converted to 0.
+  // In theory implementations should expire these timeouts immediately.
+  if (unix_nanos < 0) {
+    unix_nanos = 0;
+  }
+
+  // Values greater than or equal to kMaxNanos are converted to infinite.
+  if (unix_nanos >= kMaxNanos) {
+    rep_ = kNoTimeout;
+    return;
+  }
+
+  rep_ = static_cast<uint64_t>(unix_nanos) << 1;
+}
+
+KernelTimeout::KernelTimeout(absl::Duration d) {
+  // `absl::InfiniteDuration()` is a common "no timeout" value and cheaper to
+  // compare than convert.
+  if (d == absl::InfiniteDuration()) {
+    rep_ = kNoTimeout;
+    return;
+  }
+
+  int64_t nanos = absl::ToInt64Nanoseconds(d);
+
+  // Negative durations are normalized to 0.
+  // In theory implementations should expire these timeouts immediately.
+  if (nanos < 0) {
+    nanos = 0;
+  }
+
+  int64_t now = SteadyClockNow();
+  if (nanos > kMaxNanos - now) {
+    // Durations that would be greater than kMaxNanos are converted to infinite.
+    rep_ = kNoTimeout;
+    return;
+  }
+
+  nanos += now;
+  rep_ = (static_cast<uint64_t>(nanos) << 1) | uint64_t{1};
+}
+
+int64_t KernelTimeout::MakeAbsNanos() const {
+  if (!has_timeout()) {
+    return kMaxNanos;
+  }
+
+  int64_t nanos = RawAbsNanos();
+
+  if (is_relative_timeout()) {
+    // We need to change epochs, because the relative timeout might be
+    // represented by an absolute timestamp from another clock.
+    nanos = std::max<int64_t>(nanos - SteadyClockNow(), 0);
+    int64_t now = absl::GetCurrentTimeNanos();
+    if (nanos > kMaxNanos - now) {
+      // Overflow.
+      nanos = kMaxNanos;
+    } else {
+      nanos += now;
+    }
+  } else if (nanos == 0) {
+    // Some callers have assumed that 0 means no timeout, so instead we return a
+    // time of 1 nanosecond after the epoch.
+    nanos = 1;
+  }
+
+  return nanos;
+}
+
+int64_t KernelTimeout::InNanosecondsFromNow() const {
+  if (!has_timeout()) {
+    return kMaxNanos;
+  }
+
+  int64_t nanos = RawAbsNanos();
+  if (is_absolute_timeout()) {
+    return std::max<int64_t>(nanos - absl::GetCurrentTimeNanos(), 0);
+  }
+  return std::max<int64_t>(nanos - SteadyClockNow(), 0);
+}
+
+struct timespec KernelTimeout::MakeAbsTimespec() const {
+  return absl::ToTimespec(absl::Nanoseconds(MakeAbsNanos()));
+}
+
+struct timespec KernelTimeout::MakeRelativeTimespec() const {
+  return absl::ToTimespec(absl::Nanoseconds(InNanosecondsFromNow()));
+}
+
+#ifndef _WIN32
+struct timespec KernelTimeout::MakeClockAbsoluteTimespec(clockid_t c) const {
+  if (!has_timeout()) {
+    return absl::ToTimespec(absl::Nanoseconds(kMaxNanos));
+  }
+
+  int64_t nanos = RawAbsNanos();
+  if (is_absolute_timeout()) {
+    nanos -= absl::GetCurrentTimeNanos();
+  } else {
+    nanos -= SteadyClockNow();
+  }
+
+  struct timespec now;
+  ABSL_RAW_CHECK(clock_gettime(c, &now) == 0, "clock_gettime() failed");
+  absl::Duration from_clock_epoch =
+      absl::DurationFromTimespec(now) + absl::Nanoseconds(nanos);
+  if (from_clock_epoch <= absl::ZeroDuration()) {
+    // Some callers have assumed that 0 means no timeout, so instead we return a
+    // time of 1 nanosecond after the epoch. For safety we also do not return
+    // negative values.
+    return absl::ToTimespec(absl::Nanoseconds(1));
+  }
+  return absl::ToTimespec(from_clock_epoch);
+}
+#endif
+
+KernelTimeout::DWord KernelTimeout::InMillisecondsFromNow() const {
+  constexpr DWord kInfinite = std::numeric_limits<DWord>::max();
+
+  if (!has_timeout()) {
+    return kInfinite;
+  }
+
+  constexpr uint64_t kNanosInMillis = uint64_t{1'000'000};
+  constexpr uint64_t kMaxValueNanos =
+      std::numeric_limits<int64_t>::max() - kNanosInMillis + 1;
+
+  uint64_t ns_from_now = static_cast<uint64_t>(InNanosecondsFromNow());
+  if (ns_from_now >= kMaxValueNanos) {
+    // Rounding up would overflow.
+    return kInfinite;
+  }
+  // Convert to milliseconds, always rounding up.
+  uint64_t ms_from_now = (ns_from_now + kNanosInMillis - 1) / kNanosInMillis;
+  if (ms_from_now > kInfinite) {
+    return kInfinite;
+  }
+  return static_cast<DWord>(ms_from_now);
+}
+
+std::chrono::time_point<std::chrono::system_clock>
+KernelTimeout::ToChronoTimePoint() const {
+  if (!has_timeout()) {
+    return std::chrono::time_point<std::chrono::system_clock>::max();
+  }
+
+  // The cast to std::microseconds is because (on some platforms) the
+  // std::ratio used by std::chrono::steady_clock doesn't convert to
+  // std::nanoseconds, so it doesn't compile.
+  auto micros = std::chrono::duration_cast<std::chrono::microseconds>(
+      std::chrono::nanoseconds(MakeAbsNanos()));
+  return std::chrono::system_clock::from_time_t(0) + micros;
+}
+
+std::chrono::nanoseconds KernelTimeout::ToChronoDuration() const {
+  if (!has_timeout()) {
+    return std::chrono::nanoseconds::max();
+  }
+  return std::chrono::nanoseconds(InNanosecondsFromNow());
+}
+
+}  // namespace synchronization_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/absl/synchronization/internal/kernel_timeout.h b/absl/synchronization/internal/kernel_timeout.h
index f5c2c0ef..06404a75 100644
--- a/absl/synchronization/internal/kernel_timeout.h
+++ b/absl/synchronization/internal/kernel_timeout.h
@@ -11,26 +11,21 @@
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
-//
-
-// An optional absolute timeout, with nanosecond granularity,
-// compatible with absl::Time. Suitable for in-register
-// parameter-passing (e.g. syscalls.)
-// Constructible from a absl::Time (for a timeout to be respected) or {}
-// (for "no timeout".)
-// This is a private low-level API for use by a handful of low-level
-// components. Higher-level components should build APIs based on
-// absl::Time and absl::Duration.
 
 #ifndef ABSL_SYNCHRONIZATION_INTERNAL_KERNEL_TIMEOUT_H_
 #define ABSL_SYNCHRONIZATION_INTERNAL_KERNEL_TIMEOUT_H_
 
-#include <time.h>
+#ifndef _WIN32
+#include <sys/types.h>
+#endif
 
 #include <algorithm>
+#include <chrono>  // NOLINT(build/c++11)
 #include <cstdint>
+#include <ctime>
 #include <limits>
 
+#include "absl/base/config.h"
 #include "absl/base/internal/raw_logging.h"
 #include "absl/time/clock.h"
 #include "absl/time/time.h"
@@ -39,58 +34,73 @@ namespace absl {
 ABSL_NAMESPACE_BEGIN
 namespace synchronization_internal {
 
-class Waiter;
-
+// An optional timeout, with nanosecond granularity.
+//
+// This is a private low-level API for use by a handful of low-level
+// components. Higher-level components should build APIs based on
+// absl::Time and absl::Duration.
 class KernelTimeout {
  public:
-  // A timeout that should expire at <t>.  Any value, in the full
-  // InfinitePast() to InfiniteFuture() range, is valid here and will be
-  // respected.
-  explicit KernelTimeout(absl::Time t) : ns_(MakeNs(t)) {}
-  // No timeout.
-  KernelTimeout() : ns_(0) {}
+  // Construct an absolute timeout that should expire at `t`.
+  explicit KernelTimeout(absl::Time t);
 
-  // A more explicit factory for those who prefer it.  Equivalent to {}.
-  static KernelTimeout Never() { return {}; }
+  // Construct a relative timeout that should expire after `d`.
+  explicit KernelTimeout(absl::Duration d);
 
-  // We explicitly do not support other custom formats: timespec, int64_t nanos.
-  // Unify on this and absl::Time, please.
+  // Infinite timeout.
+  constexpr KernelTimeout() : rep_(kNoTimeout) {}
 
-  bool has_timeout() const { return ns_ != 0; }
+  // A more explicit factory for those who prefer it.
+  // Equivalent to `KernelTimeout()`.
+  static constexpr KernelTimeout Never() { return KernelTimeout(); }
 
-  // Convert to parameter for sem_timedwait/futex/similar.  Only for approved
-  // users.  Do not call if !has_timeout.
+  // Returns true if there is a timeout that will eventually expire.
+  // Returns false if the timeout is infinite.
+  bool has_timeout() const { return rep_ != kNoTimeout; }
+
+  // If `has_timeout()` is true, returns true if the timeout was provided as an
+  // `absl::Time`. The return value is undefined if `has_timeout()` is false
+  // because all indefinite timeouts are equivalent.
+  bool is_absolute_timeout() const { return (rep_ & 1) == 0; }
+
+  // If `has_timeout()` is true, returns true if the timeout was provided as an
+  // `absl::Duration`. The return value is undefined if `has_timeout()` is false
+  // because all indefinite timeouts are equivalent.
+  bool is_relative_timeout() const { return (rep_ & 1) == 1; }
+
+  // Convert to `struct timespec` for interfaces that expect an absolute
+  // timeout. If !has_timeout() or is_relative_timeout(), attempts to convert to
+  // a reasonable absolute timeout, but callers should to test has_timeout() and
+  // is_relative_timeout() and prefer to use a more appropriate interface.
   struct timespec MakeAbsTimespec() const;
 
-  // Convert to unix epoch nanos.  Do not call if !has_timeout.
+  // Convert to `struct timespec` for interfaces that expect a relative
+  // timeout. If !has_timeout() or is_absolute_timeout(), attempts to convert to
+  // a reasonable relative timeout, but callers should to test has_timeout() and
+  // is_absolute_timeout() and prefer to use a more appropriate interface. Since
+  // the return value is a relative duration, it should be recomputed by calling
+  // this method in the case of a spurious wakeup.
+  struct timespec MakeRelativeTimespec() const;
+
+#ifndef _WIN32
+  // Convert to `struct timespec` for interfaces that expect an absolute timeout
+  // on a specific clock `c`. This is similar to `MakeAbsTimespec()`, but
+  // callers usually want to use this method with `CLOCK_MONOTONIC` when
+  // relative timeouts are requested, and when the appropriate interface expects
+  // an absolute timeout relative to a specific clock (for example,
+  // pthread_cond_clockwait() or sem_clockwait()). If !has_timeout(), attempts
+  // to convert to a reasonable absolute timeout, but callers should to test
+  // has_timeout() prefer to use a more appropriate interface.
+  struct timespec MakeClockAbsoluteTimespec(clockid_t c) const;
+#endif
+
+  // Convert to unix epoch nanos for interfaces that expect an absolute timeout
+  // in nanoseconds. If !has_timeout() or is_relative_timeout(), attempts to
+  // convert to a reasonable absolute timeout, but callers should to test
+  // has_timeout() and is_relative_timeout() and prefer to use a more
+  // appropriate interface.
   int64_t MakeAbsNanos() const;
 
- private:
-  // internal rep, not user visible: ns after unix epoch.
-  // zero = no timeout.
-  // Negative we treat as an unlikely (and certainly expired!) but valid
-  // timeout.
-  int64_t ns_;
-
-  static int64_t MakeNs(absl::Time t) {
-    // optimization--InfiniteFuture is common "no timeout" value
-    // and cheaper to compare than convert.
-    if (t == absl::InfiniteFuture()) return 0;
-    int64_t x = ToUnixNanos(t);
-
-    // A timeout that lands exactly on the epoch (x=0) needs to be respected,
-    // so we alter it unnoticably to 1.  Negative timeouts are in
-    // theory supported, but handled poorly by the kernel (long
-    // delays) so push them forward too; since all such times have
-    // already passed, it's indistinguishable.
-    if (x <= 0) x = 1;
-    // A time larger than what can be represented to the kernel is treated
-    // as no timeout.
-    if (x == (std::numeric_limits<int64_t>::max)()) x = 0;
-    return x;
-  }
-
-#ifdef _WIN32
   // Converts to milliseconds from now, or INFINITE when
   // !has_timeout(). For use by SleepConditionVariableSRW on
   // Windows. Callers should recognize that the return value is a
@@ -100,68 +110,66 @@ class KernelTimeout {
   // so we define our own DWORD and INFINITE instead of getting them from
   // <intsafe.h> and <WinBase.h>.
   typedef unsigned long DWord;  // NOLINT
-  DWord InMillisecondsFromNow() const {
-    constexpr DWord kInfinite = (std::numeric_limits<DWord>::max)();
-    if (!has_timeout()) {
-      return kInfinite;
-    }
-    // The use of absl::Now() to convert from absolute time to
-    // relative time means that absl::Now() cannot use anything that
-    // depends on KernelTimeout (for example, Mutex) on Windows.
-    int64_t now = ToUnixNanos(absl::Now());
-    if (ns_ >= now) {
-      // Round up so that Now() + ms_from_now >= ns_.
-      constexpr uint64_t max_nanos =
-          (std::numeric_limits<int64_t>::max)() - 999999u;
-      uint64_t ms_from_now =
-          ((std::min)(max_nanos, static_cast<uint64_t>(ns_ - now)) + 999999u) /
-          1000000u;
-      if (ms_from_now > kInfinite) {
-        return kInfinite;
-      }
-      return static_cast<DWord>(ms_from_now);
-    }
-    return 0;
-  }
-
-  friend class Waiter;
-#endif
-};
+  DWord InMillisecondsFromNow() const;
+
+  // Convert to std::chrono::time_point for interfaces that expect an absolute
+  // timeout, like std::condition_variable::wait_until(). If !has_timeout() or
+  // is_relative_timeout(), attempts to convert to a reasonable absolute
+  // timeout, but callers should test has_timeout() and is_relative_timeout()
+  // and prefer to use a more appropriate interface.
+  std::chrono::time_point<std::chrono::system_clock> ToChronoTimePoint() const;
+
+  // Convert to std::chrono::time_point for interfaces that expect a relative
+  // timeout, like std::condition_variable::wait_for(). If !has_timeout() or
+  // is_absolute_timeout(), attempts to convert to a reasonable relative
+  // timeout, but callers should test has_timeout() and is_absolute_timeout()
+  // and prefer to use a more appropriate interface. Since the return value is a
+  // relative duration, it should be recomputed by calling this method in the
+  // case of a spurious wakeup.
+  std::chrono::nanoseconds ToChronoDuration() const;
+
+  // Returns true if steady (aka monotonic) clocks are supported by the system.
+  // This method exists because go/btm requires synchronized clocks, and
+  // thus requires we use the system (aka walltime) clock.
+  static constexpr bool SupportsSteadyClock() { return true; }
 
-inline struct timespec KernelTimeout::MakeAbsTimespec() const {
-  int64_t n = ns_;
-  static const int64_t kNanosPerSecond = 1000 * 1000 * 1000;
-  if (n == 0) {
-    ABSL_RAW_LOG(
-        ERROR, "Tried to create a timespec from a non-timeout; never do this.");
-    // But we'll try to continue sanely.  no-timeout ~= saturated timeout.
-    n = (std::numeric_limits<int64_t>::max)();
-  }
-
-  // Kernel APIs validate timespecs as being at or after the epoch,
-  // despite the kernel time type being signed.  However, no one can
-  // tell the difference between a timeout at or before the epoch (since
-  // all such timeouts have expired!)
-  if (n < 0) n = 0;
-
-  struct timespec abstime;
-  int64_t seconds = (std::min)(n / kNanosPerSecond,
-                               int64_t{(std::numeric_limits<time_t>::max)()});
-  abstime.tv_sec = static_cast<time_t>(seconds);
-  abstime.tv_nsec = static_cast<decltype(abstime.tv_nsec)>(n % kNanosPerSecond);
-  return abstime;
-}
-
-inline int64_t KernelTimeout::MakeAbsNanos() const {
-  if (ns_ == 0) {
-    ABSL_RAW_LOG(
-        ERROR, "Tried to create a timeout from a non-timeout; never do this.");
-    // But we'll try to continue sanely.  no-timeout ~= saturated timeout.
-    return (std::numeric_limits<int64_t>::max)();
-  }
-
-  return ns_;
-}
+ private:
+  // Returns the current time, expressed as a count of nanoseconds since the
+  // epoch used by an arbitrary clock. The implementation tries to use a steady
+  // (monotonic) clock if one is available.
+  static int64_t SteadyClockNow();
+
+  // Internal representation.
+  //   - If the value is kNoTimeout, then the timeout is infinite, and
+  //     has_timeout() will return true.
+  //   - If the low bit is 0, then the high 63 bits is the number of nanoseconds
+  //     after the unix epoch.
+  //   - If the low bit is 1, then the high 63 bits is the number of nanoseconds
+  //     after the epoch used by SteadyClockNow().
+  //
+  // In all cases the time is stored as an absolute time, the only difference is
+  // the clock epoch. The use of absolute times is important since in the case
+  // of a relative timeout with a spurious wakeup, the program would have to
+  // restart the wait, and thus needs a way of recomputing the remaining time.
+  uint64_t rep_;
+
+  // Returns the number of nanoseconds stored in the internal representation.
+  // When combined with the clock epoch indicated by the low bit (which is
+  // accessed through is_absolute_timeout() and is_relative_timeout()), the
+  // return value is used to compute when the timeout should occur.
+  int64_t RawAbsNanos() const { return static_cast<int64_t>(rep_ >> 1); }
+
+  // Converts to nanoseconds from now. Since the return value is a relative
+  // duration, it should be recomputed by calling this method in the case of a
+  // spurious wakeup.
+  int64_t InNanosecondsFromNow() const;
+
+  // A value that represents no timeout (or an infinite timeout).
+  static constexpr uint64_t kNoTimeout = (std::numeric_limits<uint64_t>::max)();
+
+  // The maximum value that can be stored in the high 63 bits.
+  static constexpr int64_t kMaxNanos = (std::numeric_limits<int64_t>::max)();
+};
 
 }  // namespace synchronization_internal
 ABSL_NAMESPACE_END
diff --git a/absl/synchronization/internal/kernel_timeout_test.cc b/absl/synchronization/internal/kernel_timeout_test.cc
new file mode 100644
index 00000000..92ed2691
--- /dev/null
+++ b/absl/synchronization/internal/kernel_timeout_test.cc
@@ -0,0 +1,394 @@
+// Copyright 2023 The Abseil Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/synchronization/internal/kernel_timeout.h"
+
+#include <ctime>
+#include <chrono>  // NOLINT(build/c++11)
+#include <limits>
+
+#include "absl/base/config.h"
+#include "absl/random/random.h"
+#include "absl/time/clock.h"
+#include "absl/time/time.h"
+#include "gtest/gtest.h"
+
+// Test go/btm support by randomizing the value of clock_gettime() for
+// CLOCK_MONOTONIC. This works by overriding a weak symbol in glibc.
+// We should be resistant to this randomization when !SupportsSteadyClock().
+#if defined(__GOOGLE_GRTE_VERSION__) &&      \
+    !defined(ABSL_HAVE_ADDRESS_SANITIZER) && \
+    !defined(ABSL_HAVE_MEMORY_SANITIZER) &&  \
+    !defined(ABSL_HAVE_THREAD_SANITIZER)
+extern "C" int __clock_gettime(clockid_t c, struct timespec* ts);
+
+extern "C" int clock_gettime(clockid_t c, struct timespec* ts) {
+  if (c == CLOCK_MONOTONIC &&
+      !absl::synchronization_internal::KernelTimeout::SupportsSteadyClock()) {
+    absl::SharedBitGen gen;
+    ts->tv_sec = absl::Uniform(gen, 0, 1'000'000'000);
+    ts->tv_nsec = absl::Uniform(gen, 0, 1'000'000'000);
+    return 0;
+  }
+  return __clock_gettime(c, ts);
+}
+#endif
+
+namespace {
+
+#if defined(ABSL_HAVE_ADDRESS_SANITIZER) || \
+    defined(ABSL_HAVE_MEMORY_SANITIZER) ||  \
+    defined(ABSL_HAVE_THREAD_SANITIZER) || \
+    defined(__ANDROID__) || \
+    defined(_WIN32) || defined(_WIN64)
+constexpr absl::Duration kTimingBound = absl::Milliseconds(5);
+#else
+constexpr absl::Duration kTimingBound = absl::Microseconds(250);
+#endif
+
+using absl::synchronization_internal::KernelTimeout;
+
+TEST(KernelTimeout, FiniteTimes) {
+  constexpr absl::Duration kDurationsToTest[] = {
+    absl::ZeroDuration(),
+    absl::Nanoseconds(1),
+    absl::Microseconds(1),
+    absl::Milliseconds(1),
+    absl::Seconds(1),
+    absl::Minutes(1),
+    absl::Hours(1),
+    absl::Hours(1000),
+    -absl::Nanoseconds(1),
+    -absl::Microseconds(1),
+    -absl::Milliseconds(1),
+    -absl::Seconds(1),
+    -absl::Minutes(1),
+    -absl::Hours(1),
+    -absl::Hours(1000),
+  };
+
+  for (auto duration : kDurationsToTest) {
+    const absl::Time now = absl::Now();
+    const absl::Time when = now + duration;
+    SCOPED_TRACE(duration);
+    KernelTimeout t(when);
+    EXPECT_TRUE(t.has_timeout());
+    EXPECT_TRUE(t.is_absolute_timeout());
+    EXPECT_FALSE(t.is_relative_timeout());
+    EXPECT_EQ(absl::TimeFromTimespec(t.MakeAbsTimespec()), when);
+#ifndef _WIN32
+    EXPECT_LE(
+        absl::AbsDuration(absl::Now() + duration -
+                          absl::TimeFromTimespec(
+                              t.MakeClockAbsoluteTimespec(CLOCK_REALTIME))),
+        absl::Milliseconds(10));
+#endif
+    EXPECT_LE(
+        absl::AbsDuration(absl::DurationFromTimespec(t.MakeRelativeTimespec()) -
+                          std::max(duration, absl::ZeroDuration())),
+        kTimingBound);
+    EXPECT_EQ(absl::FromUnixNanos(t.MakeAbsNanos()), when);
+    EXPECT_LE(absl::AbsDuration(absl::Milliseconds(t.InMillisecondsFromNow()) -
+                                std::max(duration, absl::ZeroDuration())),
+              absl::Milliseconds(5));
+    EXPECT_LE(absl::AbsDuration(absl::FromChrono(t.ToChronoTimePoint()) - when),
+              absl::Microseconds(1));
+    EXPECT_LE(absl::AbsDuration(absl::FromChrono(t.ToChronoDuration()) -
+                                std::max(duration, absl::ZeroDuration())),
+              kTimingBound);
+  }
+}
+
+TEST(KernelTimeout, InfiniteFuture) {
+  KernelTimeout t(absl::InfiniteFuture());
+  EXPECT_FALSE(t.has_timeout());
+  // Callers are expected to check has_timeout() instead of using the methods
+  // below, but we do try to do something reasonable if they don't. We may not
+  // be able to round-trip back to absl::InfiniteDuration() or
+  // absl::InfiniteFuture(), but we should return a very large value.
+  EXPECT_GT(absl::TimeFromTimespec(t.MakeAbsTimespec()),
+            absl::Now() + absl::Hours(100000));
+#ifndef _WIN32
+  EXPECT_GT(absl::TimeFromTimespec(t.MakeClockAbsoluteTimespec(CLOCK_REALTIME)),
+            absl::Now() + absl::Hours(100000));
+#endif
+  EXPECT_GT(absl::DurationFromTimespec(t.MakeRelativeTimespec()),
+            absl::Hours(100000));
+  EXPECT_GT(absl::FromUnixNanos(t.MakeAbsNanos()),
+            absl::Now() + absl::Hours(100000));
+  EXPECT_EQ(t.InMillisecondsFromNow(),
+            std::numeric_limits<KernelTimeout::DWord>::max());
+  EXPECT_EQ(t.ToChronoTimePoint(),
+            std::chrono::time_point<std::chrono::system_clock>::max());
+  EXPECT_GE(t.ToChronoDuration(), std::chrono::nanoseconds::max());
+}
+
+TEST(KernelTimeout, DefaultConstructor) {
+  // The default constructor is equivalent to absl::InfiniteFuture().
+  KernelTimeout t;
+  EXPECT_FALSE(t.has_timeout());
+  // Callers are expected to check has_timeout() instead of using the methods
+  // below, but we do try to do something reasonable if they don't. We may not
+  // be able to round-trip back to absl::InfiniteDuration() or
+  // absl::InfiniteFuture(), but we should return a very large value.
+  EXPECT_GT(absl::TimeFromTimespec(t.MakeAbsTimespec()),
+            absl::Now() + absl::Hours(100000));
+#ifndef _WIN32
+  EXPECT_GT(absl::TimeFromTimespec(t.MakeClockAbsoluteTimespec(CLOCK_REALTIME)),
+            absl::Now() + absl::Hours(100000));
+#endif
+  EXPECT_GT(absl::DurationFromTimespec(t.MakeRelativeTimespec()),
+            absl::Hours(100000));
+  EXPECT_GT(absl::FromUnixNanos(t.MakeAbsNanos()),
+            absl::Now() + absl::Hours(100000));
+  EXPECT_EQ(t.InMillisecondsFromNow(),
+            std::numeric_limits<KernelTimeout::DWord>::max());
+  EXPECT_EQ(t.ToChronoTimePoint(),
+            std::chrono::time_point<std::chrono::system_clock>::max());
+  EXPECT_GE(t.ToChronoDuration(), std::chrono::nanoseconds::max());
+}
+
+TEST(KernelTimeout, TimeMaxNanos) {
+  // Time >= kMaxNanos should behave as no timeout.
+  KernelTimeout t(absl::FromUnixNanos(std::numeric_limits<int64_t>::max()));
+  EXPECT_FALSE(t.has_timeout());
+  // Callers are expected to check has_timeout() instead of using the methods
+  // below, but we do try to do something reasonable if they don't. We may not
+  // be able to round-trip back to absl::InfiniteDuration() or
+  // absl::InfiniteFuture(), but we should return a very large value.
+  EXPECT_GT(absl::TimeFromTimespec(t.MakeAbsTimespec()),
+            absl::Now() + absl::Hours(100000));
+#ifndef _WIN32
+  EXPECT_GT(absl::TimeFromTimespec(t.MakeClockAbsoluteTimespec(CLOCK_REALTIME)),
+            absl::Now() + absl::Hours(100000));
+#endif
+  EXPECT_GT(absl::DurationFromTimespec(t.MakeRelativeTimespec()),
+            absl::Hours(100000));
+  EXPECT_GT(absl::FromUnixNanos(t.MakeAbsNanos()),
+            absl::Now() + absl::Hours(100000));
+  EXPECT_EQ(t.InMillisecondsFromNow(),
+            std::numeric_limits<KernelTimeout::DWord>::max());
+  EXPECT_EQ(t.ToChronoTimePoint(),
+            std::chrono::time_point<std::chrono::system_clock>::max());
+  EXPECT_GE(t.ToChronoDuration(), std::chrono::nanoseconds::max());
+}
+
+TEST(KernelTimeout, Never) {
+  // KernelTimeout::Never() is equivalent to absl::InfiniteFuture().
+  KernelTimeout t = KernelTimeout::Never();
+  EXPECT_FALSE(t.has_timeout());
+  // Callers are expected to check has_timeout() instead of using the methods
+  // below, but we do try to do something reasonable if they don't. We may not
+  // be able to round-trip back to absl::InfiniteDuration() or
+  // absl::InfiniteFuture(), but we should return a very large value.
+  EXPECT_GT(absl::TimeFromTimespec(t.MakeAbsTimespec()),
+            absl::Now() + absl::Hours(100000));
+#ifndef _WIN32
+  EXPECT_GT(absl::TimeFromTimespec(t.MakeClockAbsoluteTimespec(CLOCK_REALTIME)),
+            absl::Now() + absl::Hours(100000));
+#endif
+  EXPECT_GT(absl::DurationFromTimespec(t.MakeRelativeTimespec()),
+            absl::Hours(100000));
+  EXPECT_GT(absl::FromUnixNanos(t.MakeAbsNanos()),
+            absl::Now() + absl::Hours(100000));
+  EXPECT_EQ(t.InMillisecondsFromNow(),
+            std::numeric_limits<KernelTimeout::DWord>::max());
+  EXPECT_EQ(t.ToChronoTimePoint(),
+            std::chrono::time_point<std::chrono::system_clock>::max());
+  EXPECT_GE(t.ToChronoDuration(), std::chrono::nanoseconds::max());
+}
+
+TEST(KernelTimeout, InfinitePast) {
+  KernelTimeout t(absl::InfinitePast());
+  EXPECT_TRUE(t.has_timeout());
+  EXPECT_TRUE(t.is_absolute_timeout());
+  EXPECT_FALSE(t.is_relative_timeout());
+  EXPECT_LE(absl::TimeFromTimespec(t.MakeAbsTimespec()),
+            absl::FromUnixNanos(1));
+#ifndef _WIN32
+  EXPECT_LE(absl::TimeFromTimespec(t.MakeClockAbsoluteTimespec(CLOCK_REALTIME)),
+            absl::FromUnixSeconds(1));
+#endif
+  EXPECT_EQ(absl::DurationFromTimespec(t.MakeRelativeTimespec()),
+            absl::ZeroDuration());
+  EXPECT_LE(absl::FromUnixNanos(t.MakeAbsNanos()), absl::FromUnixNanos(1));
+  EXPECT_EQ(t.InMillisecondsFromNow(), KernelTimeout::DWord{0});
+  EXPECT_LT(t.ToChronoTimePoint(), std::chrono::system_clock::from_time_t(0) +
+                                       std::chrono::seconds(1));
+  EXPECT_EQ(t.ToChronoDuration(), std::chrono::nanoseconds(0));
+}
+
+TEST(KernelTimeout, FiniteDurations) {
+  constexpr absl::Duration kDurationsToTest[] = {
+    absl::ZeroDuration(),
+    absl::Nanoseconds(1),
+    absl::Microseconds(1),
+    absl::Milliseconds(1),
+    absl::Seconds(1),
+    absl::Minutes(1),
+    absl::Hours(1),
+    absl::Hours(1000),
+  };
+
+  for (auto duration : kDurationsToTest) {
+    SCOPED_TRACE(duration);
+    KernelTimeout t(duration);
+    EXPECT_TRUE(t.has_timeout());
+    EXPECT_FALSE(t.is_absolute_timeout());
+    EXPECT_TRUE(t.is_relative_timeout());
+    EXPECT_LE(absl::AbsDuration(absl::Now() + duration -
+                                absl::TimeFromTimespec(t.MakeAbsTimespec())),
+              absl::Milliseconds(5));
+#ifndef _WIN32
+    EXPECT_LE(
+        absl::AbsDuration(absl::Now() + duration -
+                          absl::TimeFromTimespec(
+                              t.MakeClockAbsoluteTimespec(CLOCK_REALTIME))),
+        absl::Milliseconds(5));
+#endif
+    EXPECT_LE(
+        absl::AbsDuration(absl::DurationFromTimespec(t.MakeRelativeTimespec()) -
+                          duration),
+        kTimingBound);
+    EXPECT_LE(absl::AbsDuration(absl::Now() + duration -
+                                absl::FromUnixNanos(t.MakeAbsNanos())),
+              absl::Milliseconds(5));
+    EXPECT_LE(absl::Milliseconds(t.InMillisecondsFromNow()) - duration,
+              absl::Milliseconds(5));
+    EXPECT_LE(absl::AbsDuration(absl::Now() + duration -
+                                absl::FromChrono(t.ToChronoTimePoint())),
+              kTimingBound);
+    EXPECT_LE(
+        absl::AbsDuration(absl::FromChrono(t.ToChronoDuration()) - duration),
+        kTimingBound);
+  }
+}
+
+TEST(KernelTimeout, NegativeDurations) {
+  constexpr absl::Duration kDurationsToTest[] = {
+    -absl::ZeroDuration(),
+    -absl::Nanoseconds(1),
+    -absl::Microseconds(1),
+    -absl::Milliseconds(1),
+    -absl::Seconds(1),
+    -absl::Minutes(1),
+    -absl::Hours(1),
+    -absl::Hours(1000),
+    -absl::InfiniteDuration(),
+  };
+
+  for (auto duration : kDurationsToTest) {
+    // Negative durations should all be converted to zero durations or "now".
+    SCOPED_TRACE(duration);
+    KernelTimeout t(duration);
+    EXPECT_TRUE(t.has_timeout());
+    EXPECT_FALSE(t.is_absolute_timeout());
+    EXPECT_TRUE(t.is_relative_timeout());
+    EXPECT_LE(absl::AbsDuration(absl::Now() -
+                                absl::TimeFromTimespec(t.MakeAbsTimespec())),
+              absl::Milliseconds(5));
+#ifndef _WIN32
+    EXPECT_LE(absl::AbsDuration(absl::Now() - absl::TimeFromTimespec(
+                                                  t.MakeClockAbsoluteTimespec(
+                                                      CLOCK_REALTIME))),
+              absl::Milliseconds(5));
+#endif
+    EXPECT_EQ(absl::DurationFromTimespec(t.MakeRelativeTimespec()),
+              absl::ZeroDuration());
+    EXPECT_LE(
+        absl::AbsDuration(absl::Now() - absl::FromUnixNanos(t.MakeAbsNanos())),
+        absl::Milliseconds(5));
+    EXPECT_EQ(t.InMillisecondsFromNow(), KernelTimeout::DWord{0});
+    EXPECT_LE(absl::AbsDuration(absl::Now() -
+                                absl::FromChrono(t.ToChronoTimePoint())),
+              absl::Milliseconds(5));
+    EXPECT_EQ(t.ToChronoDuration(), std::chrono::nanoseconds(0));
+  }
+}
+
+TEST(KernelTimeout, InfiniteDuration) {
+  KernelTimeout t(absl::InfiniteDuration());
+  EXPECT_FALSE(t.has_timeout());
+  // Callers are expected to check has_timeout() instead of using the methods
+  // below, but we do try to do something reasonable if they don't. We may not
+  // be able to round-trip back to absl::InfiniteDuration() or
+  // absl::InfiniteFuture(), but we should return a very large value.
+  EXPECT_GT(absl::TimeFromTimespec(t.MakeAbsTimespec()),
+            absl::Now() + absl::Hours(100000));
+#ifndef _WIN32
+  EXPECT_GT(absl::TimeFromTimespec(t.MakeClockAbsoluteTimespec(CLOCK_REALTIME)),
+            absl::Now() + absl::Hours(100000));
+#endif
+  EXPECT_GT(absl::DurationFromTimespec(t.MakeRelativeTimespec()),
+            absl::Hours(100000));
+  EXPECT_GT(absl::FromUnixNanos(t.MakeAbsNanos()),
+            absl::Now() + absl::Hours(100000));
+  EXPECT_EQ(t.InMillisecondsFromNow(),
+            std::numeric_limits<KernelTimeout::DWord>::max());
+  EXPECT_EQ(t.ToChronoTimePoint(),
+            std::chrono::time_point<std::chrono::system_clock>::max());
+  EXPECT_GE(t.ToChronoDuration(), std::chrono::nanoseconds::max());
+}
+
+TEST(KernelTimeout, DurationMaxNanos) {
+  // Duration >= kMaxNanos should behave as no timeout.
+  KernelTimeout t(absl::Nanoseconds(std::numeric_limits<int64_t>::max()));
+  EXPECT_FALSE(t.has_timeout());
+  // Callers are expected to check has_timeout() instead of using the methods
+  // below, but we do try to do something reasonable if they don't. We may not
+  // be able to round-trip back to absl::InfiniteDuration() or
+  // absl::InfiniteFuture(), but we should return a very large value.
+  EXPECT_GT(absl::TimeFromTimespec(t.MakeAbsTimespec()),
+            absl::Now() + absl::Hours(100000));
+#ifndef _WIN32
+  EXPECT_GT(absl::TimeFromTimespec(t.MakeClockAbsoluteTimespec(CLOCK_REALTIME)),
+            absl::Now() + absl::Hours(100000));
+#endif
+  EXPECT_GT(absl::DurationFromTimespec(t.MakeRelativeTimespec()),
+            absl::Hours(100000));
+  EXPECT_GT(absl::FromUnixNanos(t.MakeAbsNanos()),
+            absl::Now() + absl::Hours(100000));
+  EXPECT_EQ(t.InMillisecondsFromNow(),
+            std::numeric_limits<KernelTimeout::DWord>::max());
+  EXPECT_EQ(t.ToChronoTimePoint(),
+            std::chrono::time_point<std::chrono::system_clock>::max());
+  EXPECT_GE(t.ToChronoDuration(), std::chrono::nanoseconds::max());
+}
+
+TEST(KernelTimeout, OverflowNanos) {
+  // Test what happens when KernelTimeout is constructed with an absl::Duration
+  // that would overflow now_nanos + duration.
+  int64_t now_nanos = absl::ToUnixNanos(absl::Now());
+  int64_t limit = std::numeric_limits<int64_t>::max() - now_nanos;
+  absl::Duration duration = absl::Nanoseconds(limit) + absl::Seconds(1);
+  KernelTimeout t(duration);
+  // Timeouts should still be far in the future.
+  EXPECT_GT(absl::TimeFromTimespec(t.MakeAbsTimespec()),
+            absl::Now() + absl::Hours(100000));
+#ifndef _WIN32
+  EXPECT_GT(absl::TimeFromTimespec(t.MakeClockAbsoluteTimespec(CLOCK_REALTIME)),
+            absl::Now() + absl::Hours(100000));
+#endif
+  EXPECT_GT(absl::DurationFromTimespec(t.MakeRelativeTimespec()),
+            absl::Hours(100000));
+  EXPECT_GT(absl::FromUnixNanos(t.MakeAbsNanos()),
+            absl::Now() + absl::Hours(100000));
+  EXPECT_LE(absl::Milliseconds(t.InMillisecondsFromNow()) - duration,
+            absl::Milliseconds(5));
+  EXPECT_GT(t.ToChronoTimePoint(),
+            std::chrono::system_clock::now() + std::chrono::hours(100000));
+  EXPECT_GT(t.ToChronoDuration(), std::chrono::hours(100000));
+}
+
+}  // namespace
diff --git a/absl/synchronization/internal/per_thread_sem.cc b/absl/synchronization/internal/per_thread_sem.cc
index 469e8f32..c9b8dc1e 100644
--- a/absl/synchronization/internal/per_thread_sem.cc
+++ b/absl/synchronization/internal/per_thread_sem.cc
@@ -40,13 +40,6 @@ std::atomic<int> *PerThreadSem::GetThreadBlockedCounter() {
   return identity->blocked_count_ptr;
 }
 
-void PerThreadSem::Init(base_internal::ThreadIdentity *identity) {
-  new (Waiter::GetWaiter(identity)) Waiter();
-  identity->ticker.store(0, std::memory_order_relaxed);
-  identity->wait_start.store(0, std::memory_order_relaxed);
-  identity->is_idle.store(false, std::memory_order_relaxed);
-}
-
 void PerThreadSem::Tick(base_internal::ThreadIdentity *identity) {
   const int ticker =
       identity->ticker.fetch_add(1, std::memory_order_relaxed) + 1;
@@ -54,7 +47,7 @@ void PerThreadSem::Tick(base_internal::ThreadIdentity *identity) {
   const bool is_idle = identity->is_idle.load(std::memory_order_relaxed);
   if (wait_start && (ticker - wait_start > Waiter::kIdlePeriods) && !is_idle) {
     // Wakeup the waiting thread since it is time for it to become idle.
-    Waiter::GetWaiter(identity)->Poke();
+    ABSL_INTERNAL_C_SYMBOL(AbslInternalPerThreadSemPoke)(identity);
   }
 }
 
@@ -64,11 +57,22 @@ ABSL_NAMESPACE_END
 
 extern "C" {
 
+ABSL_ATTRIBUTE_WEAK void ABSL_INTERNAL_C_SYMBOL(AbslInternalPerThreadSemInit)(
+    absl::base_internal::ThreadIdentity *identity) {
+  new (absl::synchronization_internal::Waiter::GetWaiter(identity))
+      absl::synchronization_internal::Waiter();
+}
+
 ABSL_ATTRIBUTE_WEAK void ABSL_INTERNAL_C_SYMBOL(AbslInternalPerThreadSemPost)(
     absl::base_internal::ThreadIdentity *identity) {
   absl::synchronization_internal::Waiter::GetWaiter(identity)->Post();
 }
 
+ABSL_ATTRIBUTE_WEAK void ABSL_INTERNAL_C_SYMBOL(AbslInternalPerThreadSemPoke)(
+    absl::base_internal::ThreadIdentity *identity) {
+  absl::synchronization_internal::Waiter::GetWaiter(identity)->Poke();
+}
+
 ABSL_ATTRIBUTE_WEAK bool ABSL_INTERNAL_C_SYMBOL(AbslInternalPerThreadSemWait)(
     absl::synchronization_internal::KernelTimeout t) {
   bool timeout = false;
diff --git a/absl/synchronization/internal/per_thread_sem.h b/absl/synchronization/internal/per_thread_sem.h
index 90a88809..144ab3cd 100644
--- a/absl/synchronization/internal/per_thread_sem.h
+++ b/absl/synchronization/internal/per_thread_sem.h
@@ -64,7 +64,7 @@ class PerThreadSem {
  private:
   // Create the PerThreadSem associated with "identity".  Initializes count=0.
   // REQUIRES: May only be called by ThreadIdentity.
-  static void Init(base_internal::ThreadIdentity* identity);
+  static inline void Init(base_internal::ThreadIdentity* identity);
 
   // Increments "identity"'s count.
   static inline void Post(base_internal::ThreadIdentity* identity);
@@ -91,12 +91,21 @@ ABSL_NAMESPACE_END
 // By changing our extension points to be extern "C", we dodge this
 // check.
 extern "C" {
+void ABSL_INTERNAL_C_SYMBOL(AbslInternalPerThreadSemInit)(
+    absl::base_internal::ThreadIdentity* identity);
 void ABSL_INTERNAL_C_SYMBOL(AbslInternalPerThreadSemPost)(
     absl::base_internal::ThreadIdentity* identity);
 bool ABSL_INTERNAL_C_SYMBOL(AbslInternalPerThreadSemWait)(
     absl::synchronization_internal::KernelTimeout t);
+void ABSL_INTERNAL_C_SYMBOL(AbslInternalPerThreadSemPoke)(
+    absl::base_internal::ThreadIdentity* identity);
 }  // extern "C"
 
+void absl::synchronization_internal::PerThreadSem::Init(
+    absl::base_internal::ThreadIdentity* identity) {
+  ABSL_INTERNAL_C_SYMBOL(AbslInternalPerThreadSemInit)(identity);
+}
+
 void absl::synchronization_internal::PerThreadSem::Post(
     absl::base_internal::ThreadIdentity* identity) {
   ABSL_INTERNAL_C_SYMBOL(AbslInternalPerThreadSemPost)(identity);
diff --git a/absl/synchronization/internal/pthread_waiter.cc b/absl/synchronization/internal/pthread_waiter.cc
new file mode 100644
index 00000000..bf700e95
--- /dev/null
+++ b/absl/synchronization/internal/pthread_waiter.cc
@@ -0,0 +1,167 @@
+// Copyright 2023 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/synchronization/internal/pthread_waiter.h"
+
+#ifdef ABSL_INTERNAL_HAVE_PTHREAD_WAITER
+
+#include <pthread.h>
+#include <sys/time.h>
+#include <unistd.h>
+
+#include <cassert>
+#include <cerrno>
+
+#include "absl/base/config.h"
+#include "absl/base/internal/raw_logging.h"
+#include "absl/base/internal/thread_identity.h"
+#include "absl/base/optimization.h"
+#include "absl/synchronization/internal/kernel_timeout.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace synchronization_internal {
+
+namespace {
+class PthreadMutexHolder {
+ public:
+  explicit PthreadMutexHolder(pthread_mutex_t *mu) : mu_(mu) {
+    const int err = pthread_mutex_lock(mu_);
+    if (err != 0) {
+      ABSL_RAW_LOG(FATAL, "pthread_mutex_lock failed: %d", err);
+    }
+  }
+
+  PthreadMutexHolder(const PthreadMutexHolder &rhs) = delete;
+  PthreadMutexHolder &operator=(const PthreadMutexHolder &rhs) = delete;
+
+  ~PthreadMutexHolder() {
+    const int err = pthread_mutex_unlock(mu_);
+    if (err != 0) {
+      ABSL_RAW_LOG(FATAL, "pthread_mutex_unlock failed: %d", err);
+    }
+  }
+
+ private:
+  pthread_mutex_t *mu_;
+};
+}  // namespace
+
+#ifdef ABSL_INTERNAL_NEED_REDUNDANT_CONSTEXPR_DECL
+constexpr char PthreadWaiter::kName[];
+#endif
+
+PthreadWaiter::PthreadWaiter() : waiter_count_(0), wakeup_count_(0) {
+  const int err = pthread_mutex_init(&mu_, 0);
+  if (err != 0) {
+    ABSL_RAW_LOG(FATAL, "pthread_mutex_init failed: %d", err);
+  }
+
+  const int err2 = pthread_cond_init(&cv_, 0);
+  if (err2 != 0) {
+    ABSL_RAW_LOG(FATAL, "pthread_cond_init failed: %d", err2);
+  }
+}
+
+#ifdef __APPLE__
+#define ABSL_INTERNAL_HAS_PTHREAD_COND_TIMEDWAIT_RELATIVE_NP 1
+#endif
+
+#if defined(__GLIBC__) && \
+    (__GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 30))
+#define ABSL_INTERNAL_HAVE_PTHREAD_COND_CLOCKWAIT 1
+#elif defined(__ANDROID_API__) && __ANDROID_API__ >= 30
+#define ABSL_INTERNAL_HAVE_PTHREAD_COND_CLOCKWAIT 1
+#endif
+
+// Calls pthread_cond_timedwait() or possibly something else like
+// pthread_cond_timedwait_relative_np() depending on the platform and
+// KernelTimeout requested. The return value is the same as the return
+// value of pthread_cond_timedwait().
+int PthreadWaiter::TimedWait(KernelTimeout t) {
+  assert(t.has_timeout());
+  if (KernelTimeout::SupportsSteadyClock() && t.is_relative_timeout()) {
+#ifdef ABSL_INTERNAL_HAS_PTHREAD_COND_TIMEDWAIT_RELATIVE_NP
+    const auto rel_timeout = t.MakeRelativeTimespec();
+    return pthread_cond_timedwait_relative_np(&cv_, &mu_, &rel_timeout);
+#elif defined(ABSL_INTERNAL_HAVE_PTHREAD_COND_CLOCKWAIT) && \
+    defined(CLOCK_MONOTONIC)
+    const auto abs_clock_timeout = t.MakeClockAbsoluteTimespec(CLOCK_MONOTONIC);
+    return pthread_cond_clockwait(&cv_, &mu_, CLOCK_MONOTONIC,
+                                  &abs_clock_timeout);
+#endif
+  }
+
+  const auto abs_timeout = t.MakeAbsTimespec();
+  return pthread_cond_timedwait(&cv_, &mu_, &abs_timeout);
+}
+
+bool PthreadWaiter::Wait(KernelTimeout t) {
+  PthreadMutexHolder h(&mu_);
+  ++waiter_count_;
+  // Loop until we find a wakeup to consume or timeout.
+  // Note that, since the thread ticker is just reset, we don't need to check
+  // whether the thread is idle on the very first pass of the loop.
+  bool first_pass = true;
+  while (wakeup_count_ == 0) {
+    if (!first_pass) MaybeBecomeIdle();
+    // No wakeups available, time to wait.
+    if (!t.has_timeout()) {
+      const int err = pthread_cond_wait(&cv_, &mu_);
+      if (err != 0) {
+        ABSL_RAW_LOG(FATAL, "pthread_cond_wait failed: %d", err);
+      }
+    } else {
+      const int err = TimedWait(t);
+      if (err == ETIMEDOUT) {
+        --waiter_count_;
+        return false;
+      }
+      if (err != 0) {
+        ABSL_RAW_LOG(FATAL, "PthreadWaiter::TimedWait() failed: %d", err);
+      }
+    }
+    first_pass = false;
+  }
+  // Consume a wakeup and we're done.
+  --wakeup_count_;
+  --waiter_count_;
+  return true;
+}
+
+void PthreadWaiter::Post() {
+  PthreadMutexHolder h(&mu_);
+  ++wakeup_count_;
+  InternalCondVarPoke();
+}
+
+void PthreadWaiter::Poke() {
+  PthreadMutexHolder h(&mu_);
+  InternalCondVarPoke();
+}
+
+void PthreadWaiter::InternalCondVarPoke() {
+  if (waiter_count_ != 0) {
+    const int err = pthread_cond_signal(&cv_);
+    if (ABSL_PREDICT_FALSE(err != 0)) {
+      ABSL_RAW_LOG(FATAL, "pthread_cond_signal failed: %d", err);
+    }
+  }
+}
+
+}  // namespace synchronization_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_INTERNAL_HAVE_PTHREAD_WAITER
diff --git a/absl/synchronization/internal/pthread_waiter.h b/absl/synchronization/internal/pthread_waiter.h
new file mode 100644
index 00000000..206aefa4
--- /dev/null
+++ b/absl/synchronization/internal/pthread_waiter.h
@@ -0,0 +1,60 @@
+// Copyright 2023 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+#ifndef ABSL_SYNCHRONIZATION_INTERNAL_PTHREAD_WAITER_H_
+#define ABSL_SYNCHRONIZATION_INTERNAL_PTHREAD_WAITER_H_
+
+#ifndef _WIN32
+#include <pthread.h>
+
+#include "absl/base/config.h"
+#include "absl/synchronization/internal/kernel_timeout.h"
+#include "absl/synchronization/internal/waiter_base.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace synchronization_internal {
+
+#define ABSL_INTERNAL_HAVE_PTHREAD_WAITER 1
+
+class PthreadWaiter : public WaiterCrtp<PthreadWaiter> {
+ public:
+  PthreadWaiter();
+
+  bool Wait(KernelTimeout t);
+  void Post();
+  void Poke();
+
+  static constexpr char kName[] = "PthreadWaiter";
+
+ private:
+  int TimedWait(KernelTimeout t);
+
+  // REQUIRES: mu_ must be held.
+  void InternalCondVarPoke();
+
+  pthread_mutex_t mu_;
+  pthread_cond_t cv_;
+  int waiter_count_;
+  int wakeup_count_;  // Unclaimed wakeups.
+};
+
+}  // namespace synchronization_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ndef _WIN32
+
+#endif  // ABSL_SYNCHRONIZATION_INTERNAL_PTHREAD_WAITER_H_
diff --git a/absl/synchronization/internal/sem_waiter.cc b/absl/synchronization/internal/sem_waiter.cc
new file mode 100644
index 00000000..d62dbdc7
--- /dev/null
+++ b/absl/synchronization/internal/sem_waiter.cc
@@ -0,0 +1,122 @@
+// Copyright 2023 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/synchronization/internal/sem_waiter.h"
+
+#ifdef ABSL_INTERNAL_HAVE_SEM_WAITER
+
+#include <semaphore.h>
+
+#include <atomic>
+#include <cassert>
+#include <cstdint>
+#include <cerrno>
+
+#include "absl/base/config.h"
+#include "absl/base/internal/raw_logging.h"
+#include "absl/base/internal/thread_identity.h"
+#include "absl/base/optimization.h"
+#include "absl/synchronization/internal/kernel_timeout.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace synchronization_internal {
+
+#ifdef ABSL_INTERNAL_NEED_REDUNDANT_CONSTEXPR_DECL
+constexpr char SemWaiter::kName[];
+#endif
+
+SemWaiter::SemWaiter() : wakeups_(0) {
+  if (sem_init(&sem_, 0, 0) != 0) {
+    ABSL_RAW_LOG(FATAL, "sem_init failed with errno %d\n", errno);
+  }
+}
+
+#if defined(__GLIBC__) && \
+    (__GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 30))
+#define ABSL_INTERNAL_HAVE_SEM_CLOCKWAIT 1
+#elif defined(__ANDROID_API__) && __ANDROID_API__ >= 30
+#define ABSL_INTERNAL_HAVE_SEM_CLOCKWAIT 1
+#endif
+
+// Calls sem_timedwait() or possibly something else like
+// sem_clockwait() depending on the platform and
+// KernelTimeout requested. The return value is the same as a call to the return
+// value to a call to sem_timedwait().
+int SemWaiter::TimedWait(KernelTimeout t) {
+  if (KernelTimeout::SupportsSteadyClock() && t.is_relative_timeout()) {
+#if defined(ABSL_INTERNAL_HAVE_SEM_CLOCKWAIT) && defined(CLOCK_MONOTONIC)
+    const auto abs_clock_timeout = t.MakeClockAbsoluteTimespec(CLOCK_MONOTONIC);
+    return sem_clockwait(&sem_, CLOCK_MONOTONIC, &abs_clock_timeout);
+#endif
+  }
+
+  const auto abs_timeout = t.MakeAbsTimespec();
+  return sem_timedwait(&sem_, &abs_timeout);
+}
+
+bool SemWaiter::Wait(KernelTimeout t) {
+  // Loop until we timeout or consume a wakeup.
+  // Note that, since the thread ticker is just reset, we don't need to check
+  // whether the thread is idle on the very first pass of the loop.
+  bool first_pass = true;
+  while (true) {
+    int x = wakeups_.load(std::memory_order_relaxed);
+    while (x != 0) {
+      if (!wakeups_.compare_exchange_weak(x, x - 1,
+                                          std::memory_order_acquire,
+                                          std::memory_order_relaxed)) {
+        continue;  // Raced with someone, retry.
+      }
+      // Successfully consumed a wakeup, we're done.
+      return true;
+    }
+
+    if (!first_pass) MaybeBecomeIdle();
+    // Nothing to consume, wait (looping on EINTR).
+    while (true) {
+      if (!t.has_timeout()) {
+        if (sem_wait(&sem_) == 0) break;
+        if (errno == EINTR) continue;
+        ABSL_RAW_LOG(FATAL, "sem_wait failed: %d", errno);
+      } else {
+        if (TimedWait(t) == 0) break;
+        if (errno == EINTR) continue;
+        if (errno == ETIMEDOUT) return false;
+        ABSL_RAW_LOG(FATAL, "SemWaiter::TimedWait() failed: %d", errno);
+      }
+    }
+    first_pass = false;
+  }
+}
+
+void SemWaiter::Post() {
+  // Post a wakeup.
+  if (wakeups_.fetch_add(1, std::memory_order_release) == 0) {
+    // We incremented from 0, need to wake a potential waiter.
+    Poke();
+  }
+}
+
+void SemWaiter::Poke() {
+  if (sem_post(&sem_) != 0) {  // Wake any semaphore waiter.
+    ABSL_RAW_LOG(FATAL, "sem_post failed with errno %d\n", errno);
+  }
+}
+
+}  // namespace synchronization_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_INTERNAL_HAVE_SEM_WAITER
diff --git a/absl/synchronization/internal/sem_waiter.h b/absl/synchronization/internal/sem_waiter.h
new file mode 100644
index 00000000..c22746f9
--- /dev/null
+++ b/absl/synchronization/internal/sem_waiter.h
@@ -0,0 +1,65 @@
+// Copyright 2023 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+#ifndef ABSL_SYNCHRONIZATION_INTERNAL_SEM_WAITER_H_
+#define ABSL_SYNCHRONIZATION_INTERNAL_SEM_WAITER_H_
+
+#include "absl/base/config.h"
+
+#ifdef ABSL_HAVE_SEMAPHORE_H
+#include <semaphore.h>
+
+#include <atomic>
+#include <cstdint>
+
+#include "absl/base/internal/thread_identity.h"
+#include "absl/synchronization/internal/futex.h"
+#include "absl/synchronization/internal/kernel_timeout.h"
+#include "absl/synchronization/internal/waiter_base.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace synchronization_internal {
+
+#define ABSL_INTERNAL_HAVE_SEM_WAITER 1
+
+class SemWaiter : public WaiterCrtp<SemWaiter> {
+ public:
+  SemWaiter();
+
+  bool Wait(KernelTimeout t);
+  void Post();
+  void Poke();
+
+  static constexpr char kName[] = "SemWaiter";
+
+ private:
+  int TimedWait(KernelTimeout t);
+
+  sem_t sem_;
+
+  // This seems superfluous, but for Poke() we need to cause spurious
+  // wakeups on the semaphore. Hence we can't actually use the
+  // semaphore's count.
+  std::atomic<int> wakeups_;
+};
+
+}  // namespace synchronization_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_HAVE_SEMAPHORE_H
+
+#endif  // ABSL_SYNCHRONIZATION_INTERNAL_SEM_WAITER_H_
diff --git a/absl/synchronization/internal/stdcpp_waiter.cc b/absl/synchronization/internal/stdcpp_waiter.cc
new file mode 100644
index 00000000..355718a7
--- /dev/null
+++ b/absl/synchronization/internal/stdcpp_waiter.cc
@@ -0,0 +1,91 @@
+// Copyright 2023 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/synchronization/internal/stdcpp_waiter.h"
+
+#ifdef ABSL_INTERNAL_HAVE_STDCPP_WAITER
+
+#include <chrono>  // NOLINT(build/c++11)
+#include <condition_variable>  // NOLINT(build/c++11)
+#include <mutex>  // NOLINT(build/c++11)
+
+#include "absl/base/config.h"
+#include "absl/base/internal/raw_logging.h"
+#include "absl/base/internal/thread_identity.h"
+#include "absl/base/optimization.h"
+#include "absl/synchronization/internal/kernel_timeout.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace synchronization_internal {
+
+#ifdef ABSL_INTERNAL_NEED_REDUNDANT_CONSTEXPR_DECL
+constexpr char StdcppWaiter::kName[];
+#endif
+
+StdcppWaiter::StdcppWaiter() : waiter_count_(0), wakeup_count_(0) {}
+
+bool StdcppWaiter::Wait(KernelTimeout t) {
+  std::unique_lock<std::mutex> lock(mu_);
+  ++waiter_count_;
+
+  // Loop until we find a wakeup to consume or timeout.
+  // Note that, since the thread ticker is just reset, we don't need to check
+  // whether the thread is idle on the very first pass of the loop.
+  bool first_pass = true;
+  while (wakeup_count_ == 0) {
+    if (!first_pass) MaybeBecomeIdle();
+    // No wakeups available, time to wait.
+    if (!t.has_timeout()) {
+      cv_.wait(lock);
+    } else {
+      auto wait_result = t.SupportsSteadyClock() && t.is_relative_timeout()
+                             ? cv_.wait_for(lock, t.ToChronoDuration())
+                             : cv_.wait_until(lock, t.ToChronoTimePoint());
+      if (wait_result == std::cv_status::timeout) {
+        --waiter_count_;
+        return false;
+      }
+    }
+    first_pass = false;
+  }
+
+  // Consume a wakeup and we're done.
+  --wakeup_count_;
+  --waiter_count_;
+  return true;
+}
+
+void StdcppWaiter::Post() {
+  std::lock_guard<std::mutex> lock(mu_);
+  ++wakeup_count_;
+  InternalCondVarPoke();
+}
+
+void StdcppWaiter::Poke() {
+  std::lock_guard<std::mutex> lock(mu_);
+  InternalCondVarPoke();
+}
+
+void StdcppWaiter::InternalCondVarPoke() {
+  if (waiter_count_ != 0) {
+    cv_.notify_one();
+  }
+}
+
+}  // namespace synchronization_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_INTERNAL_HAVE_STDCPP_WAITER
diff --git a/absl/synchronization/internal/stdcpp_waiter.h b/absl/synchronization/internal/stdcpp_waiter.h
new file mode 100644
index 00000000..e592a27b
--- /dev/null
+++ b/absl/synchronization/internal/stdcpp_waiter.h
@@ -0,0 +1,56 @@
+// Copyright 2023 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+#ifndef ABSL_SYNCHRONIZATION_INTERNAL_STDCPP_WAITER_H_
+#define ABSL_SYNCHRONIZATION_INTERNAL_STDCPP_WAITER_H_
+
+#include <condition_variable>  // NOLINT(build/c++11)
+#include <mutex>  // NOLINT(build/c++11)
+
+#include "absl/base/config.h"
+#include "absl/synchronization/internal/kernel_timeout.h"
+#include "absl/synchronization/internal/waiter_base.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace synchronization_internal {
+
+#define ABSL_INTERNAL_HAVE_STDCPP_WAITER 1
+
+class StdcppWaiter : public WaiterCrtp<StdcppWaiter> {
+ public:
+  StdcppWaiter();
+
+  bool Wait(KernelTimeout t);
+  void Post();
+  void Poke();
+
+  static constexpr char kName[] = "StdcppWaiter";
+
+ private:
+  // REQUIRES: mu_ must be held.
+  void InternalCondVarPoke();
+
+  std::mutex mu_;
+  std::condition_variable cv_;
+  int waiter_count_;
+  int wakeup_count_;  // Unclaimed wakeups.
+};
+
+}  // namespace synchronization_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_SYNCHRONIZATION_INTERNAL_STDCPP_WAITER_H_
diff --git a/absl/synchronization/internal/waiter.cc b/absl/synchronization/internal/waiter.cc
deleted file mode 100644
index f2051d67..00000000
--- a/absl/synchronization/internal/waiter.cc
+++ /dev/null
@@ -1,403 +0,0 @@
-// Copyright 2017 The Abseil Authors.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//      https://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-#include "absl/synchronization/internal/waiter.h"
-
-#include "absl/base/config.h"
-
-#ifdef _WIN32
-#include <windows.h>
-#else
-#include <pthread.h>
-#include <sys/time.h>
-#include <unistd.h>
-#endif
-
-#ifdef __linux__
-#include <linux/futex.h>
-#include <sys/syscall.h>
-#endif
-
-#ifdef ABSL_HAVE_SEMAPHORE_H
-#include <semaphore.h>
-#endif
-
-#include <errno.h>
-#include <stdio.h>
-#include <time.h>
-
-#include <atomic>
-#include <cassert>
-#include <cstdint>
-#include <new>
-#include <type_traits>
-
-#include "absl/base/internal/raw_logging.h"
-#include "absl/base/internal/thread_identity.h"
-#include "absl/base/optimization.h"
-#include "absl/synchronization/internal/kernel_timeout.h"
-
-
-namespace absl {
-ABSL_NAMESPACE_BEGIN
-namespace synchronization_internal {
-
-static void MaybeBecomeIdle() {
-  base_internal::ThreadIdentity *identity =
-      base_internal::CurrentThreadIdentityIfPresent();
-  assert(identity != nullptr);
-  const bool is_idle = identity->is_idle.load(std::memory_order_relaxed);
-  const int ticker = identity->ticker.load(std::memory_order_relaxed);
-  const int wait_start = identity->wait_start.load(std::memory_order_relaxed);
-  if (!is_idle && ticker - wait_start > Waiter::kIdlePeriods) {
-    identity->is_idle.store(true, std::memory_order_relaxed);
-  }
-}
-
-#if ABSL_WAITER_MODE == ABSL_WAITER_MODE_FUTEX
-
-Waiter::Waiter() {
-  futex_.store(0, std::memory_order_relaxed);
-}
-
-bool Waiter::Wait(KernelTimeout t) {
-  // Loop until we can atomically decrement futex from a positive
-  // value, waiting on a futex while we believe it is zero.
-  // Note that, since the thread ticker is just reset, we don't need to check
-  // whether the thread is idle on the very first pass of the loop.
-  bool first_pass = true;
-
-  while (true) {
-    int32_t x = futex_.load(std::memory_order_relaxed);
-    while (x != 0) {
-      if (!futex_.compare_exchange_weak(x, x - 1,
-                                        std::memory_order_acquire,
-                                        std::memory_order_relaxed)) {
-        continue;  // Raced with someone, retry.
-      }
-      return true;  // Consumed a wakeup, we are done.
-    }
-
-    if (!first_pass) MaybeBecomeIdle();
-    const int err = Futex::WaitUntil(&futex_, 0, t);
-    if (err != 0) {
-      if (err == -EINTR || err == -EWOULDBLOCK) {
-        // Do nothing, the loop will retry.
-      } else if (err == -ETIMEDOUT) {
-        return false;
-      } else {
-        ABSL_RAW_LOG(FATAL, "Futex operation failed with error %d\n", err);
-      }
-    }
-    first_pass = false;
-  }
-}
-
-void Waiter::Post() {
-  if (futex_.fetch_add(1, std::memory_order_release) == 0) {
-    // We incremented from 0, need to wake a potential waiter.
-    Poke();
-  }
-}
-
-void Waiter::Poke() {
-  // Wake one thread waiting on the futex.
-  const int err = Futex::Wake(&futex_, 1);
-  if (ABSL_PREDICT_FALSE(err < 0)) {
-    ABSL_RAW_LOG(FATAL, "Futex operation failed with error %d\n", err);
-  }
-}
-
-#elif ABSL_WAITER_MODE == ABSL_WAITER_MODE_CONDVAR
-
-class PthreadMutexHolder {
- public:
-  explicit PthreadMutexHolder(pthread_mutex_t *mu) : mu_(mu) {
-    const int err = pthread_mutex_lock(mu_);
-    if (err != 0) {
-      ABSL_RAW_LOG(FATAL, "pthread_mutex_lock failed: %d", err);
-    }
-  }
-
-  PthreadMutexHolder(const PthreadMutexHolder &rhs) = delete;
-  PthreadMutexHolder &operator=(const PthreadMutexHolder &rhs) = delete;
-
-  ~PthreadMutexHolder() {
-    const int err = pthread_mutex_unlock(mu_);
-    if (err != 0) {
-      ABSL_RAW_LOG(FATAL, "pthread_mutex_unlock failed: %d", err);
-    }
-  }
-
- private:
-  pthread_mutex_t *mu_;
-};
-
-Waiter::Waiter() {
-  const int err = pthread_mutex_init(&mu_, 0);
-  if (err != 0) {
-    ABSL_RAW_LOG(FATAL, "pthread_mutex_init failed: %d", err);
-  }
-
-  const int err2 = pthread_cond_init(&cv_, 0);
-  if (err2 != 0) {
-    ABSL_RAW_LOG(FATAL, "pthread_cond_init failed: %d", err2);
-  }
-
-  waiter_count_ = 0;
-  wakeup_count_ = 0;
-}
-
-bool Waiter::Wait(KernelTimeout t) {
-  struct timespec abs_timeout;
-  if (t.has_timeout()) {
-    abs_timeout = t.MakeAbsTimespec();
-  }
-
-  PthreadMutexHolder h(&mu_);
-  ++waiter_count_;
-  // Loop until we find a wakeup to consume or timeout.
-  // Note that, since the thread ticker is just reset, we don't need to check
-  // whether the thread is idle on the very first pass of the loop.
-  bool first_pass = true;
-  while (wakeup_count_ == 0) {
-    if (!first_pass) MaybeBecomeIdle();
-    // No wakeups available, time to wait.
-    if (!t.has_timeout()) {
-      const int err = pthread_cond_wait(&cv_, &mu_);
-      if (err != 0) {
-        ABSL_RAW_LOG(FATAL, "pthread_cond_wait failed: %d", err);
-      }
-    } else {
-      const int err = pthread_cond_timedwait(&cv_, &mu_, &abs_timeout);
-      if (err == ETIMEDOUT) {
-        --waiter_count_;
-        return false;
-      }
-      if (err != 0) {
-        ABSL_RAW_LOG(FATAL, "pthread_cond_timedwait failed: %d", err);
-      }
-    }
-    first_pass = false;
-  }
-  // Consume a wakeup and we're done.
-  --wakeup_count_;
-  --waiter_count_;
-  return true;
-}
-
-void Waiter::Post() {
-  PthreadMutexHolder h(&mu_);
-  ++wakeup_count_;
-  InternalCondVarPoke();
-}
-
-void Waiter::Poke() {
-  PthreadMutexHolder h(&mu_);
-  InternalCondVarPoke();
-}
-
-void Waiter::InternalCondVarPoke() {
-  if (waiter_count_ != 0) {
-    const int err = pthread_cond_signal(&cv_);
-    if (ABSL_PREDICT_FALSE(err != 0)) {
-      ABSL_RAW_LOG(FATAL, "pthread_cond_signal failed: %d", err);
-    }
-  }
-}
-
-#elif ABSL_WAITER_MODE == ABSL_WAITER_MODE_SEM
-
-Waiter::Waiter() {
-  if (sem_init(&sem_, 0, 0) != 0) {
-    ABSL_RAW_LOG(FATAL, "sem_init failed with errno %d\n", errno);
-  }
-  wakeups_.store(0, std::memory_order_relaxed);
-}
-
-bool Waiter::Wait(KernelTimeout t) {
-  struct timespec abs_timeout;
-  if (t.has_timeout()) {
-    abs_timeout = t.MakeAbsTimespec();
-  }
-
-  // Loop until we timeout or consume a wakeup.
-  // Note that, since the thread ticker is just reset, we don't need to check
-  // whether the thread is idle on the very first pass of the loop.
-  bool first_pass = true;
-  while (true) {
-    int x = wakeups_.load(std::memory_order_relaxed);
-    while (x != 0) {
-      if (!wakeups_.compare_exchange_weak(x, x - 1,
-                                          std::memory_order_acquire,
-                                          std::memory_order_relaxed)) {
-        continue;  // Raced with someone, retry.
-      }
-      // Successfully consumed a wakeup, we're done.
-      return true;
-    }
-
-    if (!first_pass) MaybeBecomeIdle();
-    // Nothing to consume, wait (looping on EINTR).
-    while (true) {
-      if (!t.has_timeout()) {
-        if (sem_wait(&sem_) == 0) break;
-        if (errno == EINTR) continue;
-        ABSL_RAW_LOG(FATAL, "sem_wait failed: %d", errno);
-      } else {
-        if (sem_timedwait(&sem_, &abs_timeout) == 0) break;
-        if (errno == EINTR) continue;
-        if (errno == ETIMEDOUT) return false;
-        ABSL_RAW_LOG(FATAL, "sem_timedwait failed: %d", errno);
-      }
-    }
-    first_pass = false;
-  }
-}
-
-void Waiter::Post() {
-  // Post a wakeup.
-  if (wakeups_.fetch_add(1, std::memory_order_release) == 0) {
-    // We incremented from 0, need to wake a potential waiter.
-    Poke();
-  }
-}
-
-void Waiter::Poke() {
-  if (sem_post(&sem_) != 0) {  // Wake any semaphore waiter.
-    ABSL_RAW_LOG(FATAL, "sem_post failed with errno %d\n", errno);
-  }
-}
-
-#elif ABSL_WAITER_MODE == ABSL_WAITER_MODE_WIN32
-
-class Waiter::WinHelper {
- public:
-  static SRWLOCK *GetLock(Waiter *w) {
-    return reinterpret_cast<SRWLOCK *>(&w->mu_storage_);
-  }
-
-  static CONDITION_VARIABLE *GetCond(Waiter *w) {
-    return reinterpret_cast<CONDITION_VARIABLE *>(&w->cv_storage_);
-  }
-
-  static_assert(sizeof(SRWLOCK) == sizeof(void *),
-                "`mu_storage_` does not have the same size as SRWLOCK");
-  static_assert(alignof(SRWLOCK) == alignof(void *),
-                "`mu_storage_` does not have the same alignment as SRWLOCK");
-
-  static_assert(sizeof(CONDITION_VARIABLE) == sizeof(void *),
-                "`ABSL_CONDITION_VARIABLE_STORAGE` does not have the same size "
-                "as `CONDITION_VARIABLE`");
-  static_assert(
-      alignof(CONDITION_VARIABLE) == alignof(void *),
-      "`cv_storage_` does not have the same alignment as `CONDITION_VARIABLE`");
-
-  // The SRWLOCK and CONDITION_VARIABLE types must be trivially constructible
-  // and destructible because we never call their constructors or destructors.
-  static_assert(std::is_trivially_constructible<SRWLOCK>::value,
-                "The `SRWLOCK` type must be trivially constructible");
-  static_assert(
-      std::is_trivially_constructible<CONDITION_VARIABLE>::value,
-      "The `CONDITION_VARIABLE` type must be trivially constructible");
-  static_assert(std::is_trivially_destructible<SRWLOCK>::value,
-                "The `SRWLOCK` type must be trivially destructible");
-  static_assert(std::is_trivially_destructible<CONDITION_VARIABLE>::value,
-                "The `CONDITION_VARIABLE` type must be trivially destructible");
-};
-
-class LockHolder {
- public:
-  explicit LockHolder(SRWLOCK* mu) : mu_(mu) {
-    AcquireSRWLockExclusive(mu_);
-  }
-
-  LockHolder(const LockHolder&) = delete;
-  LockHolder& operator=(const LockHolder&) = delete;
-
-  ~LockHolder() {
-    ReleaseSRWLockExclusive(mu_);
-  }
-
- private:
-  SRWLOCK* mu_;
-};
-
-Waiter::Waiter() {
-  auto *mu = ::new (static_cast<void *>(&mu_storage_)) SRWLOCK;
-  auto *cv = ::new (static_cast<void *>(&cv_storage_)) CONDITION_VARIABLE;
-  InitializeSRWLock(mu);
-  InitializeConditionVariable(cv);
-  waiter_count_ = 0;
-  wakeup_count_ = 0;
-}
-
-bool Waiter::Wait(KernelTimeout t) {
-  SRWLOCK *mu = WinHelper::GetLock(this);
-  CONDITION_VARIABLE *cv = WinHelper::GetCond(this);
-
-  LockHolder h(mu);
-  ++waiter_count_;
-
-  // Loop until we find a wakeup to consume or timeout.
-  // Note that, since the thread ticker is just reset, we don't need to check
-  // whether the thread is idle on the very first pass of the loop.
-  bool first_pass = true;
-  while (wakeup_count_ == 0) {
-    if (!first_pass) MaybeBecomeIdle();
-    // No wakeups available, time to wait.
-    if (!SleepConditionVariableSRW(cv, mu, t.InMillisecondsFromNow(), 0)) {
-      // GetLastError() returns a Win32 DWORD, but we assign to
-      // unsigned long to simplify the ABSL_RAW_LOG case below.  The uniform
-      // initialization guarantees this is not a narrowing conversion.
-      const unsigned long err{GetLastError()};  // NOLINT(runtime/int)
-      if (err == ERROR_TIMEOUT) {
-        --waiter_count_;
-        return false;
-      } else {
-        ABSL_RAW_LOG(FATAL, "SleepConditionVariableSRW failed: %lu", err);
-      }
-    }
-    first_pass = false;
-  }
-  // Consume a wakeup and we're done.
-  --wakeup_count_;
-  --waiter_count_;
-  return true;
-}
-
-void Waiter::Post() {
-  LockHolder h(WinHelper::GetLock(this));
-  ++wakeup_count_;
-  InternalCondVarPoke();
-}
-
-void Waiter::Poke() {
-  LockHolder h(WinHelper::GetLock(this));
-  InternalCondVarPoke();
-}
-
-void Waiter::InternalCondVarPoke() {
-  if (waiter_count_ != 0) {
-    WakeConditionVariable(WinHelper::GetCond(this));
-  }
-}
-
-#else
-#error Unknown ABSL_WAITER_MODE
-#endif
-
-}  // namespace synchronization_internal
-ABSL_NAMESPACE_END
-}  // namespace absl
diff --git a/absl/synchronization/internal/waiter.h b/absl/synchronization/internal/waiter.h
index b8adfeb5..1a8b0b83 100644
--- a/absl/synchronization/internal/waiter.h
+++ b/absl/synchronization/internal/waiter.h
@@ -17,142 +17,48 @@
 #define ABSL_SYNCHRONIZATION_INTERNAL_WAITER_H_
 
 #include "absl/base/config.h"
-
-#ifdef _WIN32
-#include <sdkddkver.h>
-#else
-#include <pthread.h>
-#endif
-
-#ifdef __linux__
-#include <linux/futex.h>
-#endif
-
-#ifdef ABSL_HAVE_SEMAPHORE_H
-#include <semaphore.h>
-#endif
-
-#include <atomic>
-#include <cstdint>
-
-#include "absl/base/internal/thread_identity.h"
-#include "absl/synchronization/internal/futex.h"
-#include "absl/synchronization/internal/kernel_timeout.h"
+#include "absl/synchronization/internal/futex_waiter.h"
+#include "absl/synchronization/internal/pthread_waiter.h"
+#include "absl/synchronization/internal/sem_waiter.h"
+#include "absl/synchronization/internal/stdcpp_waiter.h"
+#include "absl/synchronization/internal/win32_waiter.h"
 
 // May be chosen at compile time via -DABSL_FORCE_WAITER_MODE=<index>
 #define ABSL_WAITER_MODE_FUTEX 0
 #define ABSL_WAITER_MODE_SEM 1
 #define ABSL_WAITER_MODE_CONDVAR 2
 #define ABSL_WAITER_MODE_WIN32 3
+#define ABSL_WAITER_MODE_STDCPP 4
 
 #if defined(ABSL_FORCE_WAITER_MODE)
 #define ABSL_WAITER_MODE ABSL_FORCE_WAITER_MODE
-#elif defined(_WIN32) && _WIN32_WINNT >= _WIN32_WINNT_VISTA
+#elif defined(ABSL_INTERNAL_HAVE_WIN32_WAITER)
 #define ABSL_WAITER_MODE ABSL_WAITER_MODE_WIN32
-#elif defined(ABSL_INTERNAL_HAVE_FUTEX)
+#elif defined(ABSL_INTERNAL_HAVE_FUTEX_WAITER)
 #define ABSL_WAITER_MODE ABSL_WAITER_MODE_FUTEX
-#elif defined(ABSL_HAVE_SEMAPHORE_H)
+#elif defined(ABSL_INTERNAL_HAVE_SEM_WAITER)
 #define ABSL_WAITER_MODE ABSL_WAITER_MODE_SEM
-#else
+#elif defined(ABSL_INTERNAL_HAVE_PTHREAD_WAITER)
 #define ABSL_WAITER_MODE ABSL_WAITER_MODE_CONDVAR
+#else
+#error ABSL_WAITER_MODE is undefined
 #endif
 
 namespace absl {
 ABSL_NAMESPACE_BEGIN
 namespace synchronization_internal {
 
-// Waiter is an OS-specific semaphore.
-class Waiter {
- public:
-  // Prepare any data to track waits.
-  Waiter();
-
-  // Not copyable or movable
-  Waiter(const Waiter&) = delete;
-  Waiter& operator=(const Waiter&) = delete;
-
-  // Blocks the calling thread until a matching call to `Post()` or
-  // `t` has passed. Returns `true` if woken (`Post()` called),
-  // `false` on timeout.
-  bool Wait(KernelTimeout t);
-
-  // Restart the caller of `Wait()` as with a normal semaphore.
-  void Post();
-
-  // If anyone is waiting, wake them up temporarily and cause them to
-  // call `MaybeBecomeIdle()`. They will then return to waiting for a
-  // `Post()` or timeout.
-  void Poke();
-
-  // Returns the Waiter associated with the identity.
-  static Waiter* GetWaiter(base_internal::ThreadIdentity* identity) {
-    static_assert(
-        sizeof(Waiter) <= sizeof(base_internal::ThreadIdentity::WaiterState),
-        "Insufficient space for Waiter");
-    return reinterpret_cast<Waiter*>(identity->waiter_state.data);
-  }
-
-  // How many periods to remain idle before releasing resources
-#ifndef ABSL_HAVE_THREAD_SANITIZER
-  static constexpr int kIdlePeriods = 60;
-#else
-  // Memory consumption under ThreadSanitizer is a serious concern,
-  // so we release resources sooner. The value of 1 leads to 1 to 2 second
-  // delay before marking a thread as idle.
-  static const int kIdlePeriods = 1;
-#endif
-
- private:
-  // The destructor must not be called since Mutex/CondVar
-  // can use PerThreadSem/Waiter after the thread exits.
-  // Waiter objects are embedded in ThreadIdentity objects,
-  // which are reused via a freelist and are never destroyed.
-  ~Waiter() = delete;
-
 #if ABSL_WAITER_MODE == ABSL_WAITER_MODE_FUTEX
-  // Futexes are defined by specification to be 32-bits.
-  // Thus std::atomic<int32_t> must be just an int32_t with lockfree methods.
-  std::atomic<int32_t> futex_;
-  static_assert(sizeof(int32_t) == sizeof(futex_), "Wrong size for futex");
-
-#elif ABSL_WAITER_MODE == ABSL_WAITER_MODE_CONDVAR
-  // REQUIRES: mu_ must be held.
-  void InternalCondVarPoke();
-
-  pthread_mutex_t mu_;
-  pthread_cond_t cv_;
-  int waiter_count_;
-  int wakeup_count_;  // Unclaimed wakeups.
-
+using Waiter = FutexWaiter;
 #elif ABSL_WAITER_MODE == ABSL_WAITER_MODE_SEM
-  sem_t sem_;
-  // This seems superfluous, but for Poke() we need to cause spurious
-  // wakeups on the semaphore. Hence we can't actually use the
-  // semaphore's count.
-  std::atomic<int> wakeups_;
-
+using Waiter = SemWaiter;
+#elif ABSL_WAITER_MODE == ABSL_WAITER_MODE_CONDVAR
+using Waiter = PthreadWaiter;
 #elif ABSL_WAITER_MODE == ABSL_WAITER_MODE_WIN32
-  // WinHelper - Used to define utilities for accessing the lock and
-  // condition variable storage once the types are complete.
-  class WinHelper;
-
-  // REQUIRES: WinHelper::GetLock(this) must be held.
-  void InternalCondVarPoke();
-
-  // We can't include Windows.h in our headers, so we use aligned character
-  // buffers to define the storage of SRWLOCK and CONDITION_VARIABLE.
-  // SRW locks and condition variables do not need to be explicitly destroyed.
-  // https://docs.microsoft.com/en-us/windows/win32/api/synchapi/nf-synchapi-initializesrwlock
-  // https://stackoverflow.com/questions/28975958/why-does-windows-have-no-deleteconditionvariable-function-to-go-together-with
-  alignas(void*) unsigned char mu_storage_[sizeof(void*)];
-  alignas(void*) unsigned char cv_storage_[sizeof(void*)];
-  int waiter_count_;
-  int wakeup_count_;
-
-#else
-  #error Unknown ABSL_WAITER_MODE
+using Waiter = Win32Waiter;
+#elif ABSL_WAITER_MODE == ABSL_WAITER_MODE_STDCPP
+using Waiter = StdcppWaiter;
 #endif
-};
 
 }  // namespace synchronization_internal
 ABSL_NAMESPACE_END
diff --git a/absl/synchronization/internal/waiter_base.cc b/absl/synchronization/internal/waiter_base.cc
new file mode 100644
index 00000000..46928b40
--- /dev/null
+++ b/absl/synchronization/internal/waiter_base.cc
@@ -0,0 +1,42 @@
+// Copyright 2023 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/synchronization/internal/waiter_base.h"
+
+#include "absl/base/config.h"
+#include "absl/base/internal/thread_identity.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace synchronization_internal {
+
+#ifdef ABSL_INTERNAL_NEED_REDUNDANT_CONSTEXPR_DECL
+constexpr int WaiterBase::kIdlePeriods;
+#endif
+
+void WaiterBase::MaybeBecomeIdle() {
+  base_internal::ThreadIdentity *identity =
+      base_internal::CurrentThreadIdentityIfPresent();
+  assert(identity != nullptr);
+  const bool is_idle = identity->is_idle.load(std::memory_order_relaxed);
+  const int ticker = identity->ticker.load(std::memory_order_relaxed);
+  const int wait_start = identity->wait_start.load(std::memory_order_relaxed);
+  if (!is_idle && ticker - wait_start > kIdlePeriods) {
+    identity->is_idle.store(true, std::memory_order_relaxed);
+  }
+}
+
+}  // namespace synchronization_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/absl/synchronization/internal/waiter_base.h b/absl/synchronization/internal/waiter_base.h
new file mode 100644
index 00000000..cf175481
--- /dev/null
+++ b/absl/synchronization/internal/waiter_base.h
@@ -0,0 +1,90 @@
+// Copyright 2023 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+#ifndef ABSL_SYNCHRONIZATION_INTERNAL_WAITER_BASE_H_
+#define ABSL_SYNCHRONIZATION_INTERNAL_WAITER_BASE_H_
+
+#include "absl/base/config.h"
+#include "absl/base/internal/thread_identity.h"
+#include "absl/synchronization/internal/kernel_timeout.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace synchronization_internal {
+
+// `Waiter` is a platform specific semaphore implementation that `PerThreadSem`
+// waits on to implement blocking in `absl::Mutex`.  Implementations should
+// inherit from `WaiterCrtp` and must implement `Wait()`, `Post()`, and `Poke()`
+// as described in `WaiterBase`.  `waiter.h` selects the implementation and uses
+// static-dispatch for performance.
+class WaiterBase {
+ public:
+  WaiterBase() = default;
+
+  // Not copyable or movable
+  WaiterBase(const WaiterBase&) = delete;
+  WaiterBase& operator=(const WaiterBase&) = delete;
+
+  // Blocks the calling thread until a matching call to `Post()` or
+  // `t` has passed. Returns `true` if woken (`Post()` called),
+  // `false` on timeout.
+  //
+  // bool Wait(KernelTimeout t);
+
+  // Restart the caller of `Wait()` as with a normal semaphore.
+  //
+  // void Post();
+
+  // If anyone is waiting, wake them up temporarily and cause them to
+  // call `MaybeBecomeIdle()`. They will then return to waiting for a
+  // `Post()` or timeout.
+  //
+  // void Poke();
+
+  // Returns the name of this implementation. Used only for debugging.
+  //
+  // static constexpr char kName[];
+
+  // How many periods to remain idle before releasing resources
+#ifndef ABSL_HAVE_THREAD_SANITIZER
+  static constexpr int kIdlePeriods = 60;
+#else
+  // Memory consumption under ThreadSanitizer is a serious concern,
+  // so we release resources sooner. The value of 1 leads to 1 to 2 second
+  // delay before marking a thread as idle.
+  static constexpr int kIdlePeriods = 1;
+#endif
+
+ protected:
+  static void MaybeBecomeIdle();
+};
+
+template <typename T>
+class WaiterCrtp : public WaiterBase {
+ public:
+  // Returns the Waiter associated with the identity.
+  static T* GetWaiter(base_internal::ThreadIdentity* identity) {
+    static_assert(
+        sizeof(T) <= sizeof(base_internal::ThreadIdentity::WaiterState),
+        "Insufficient space for Waiter");
+    return reinterpret_cast<T*>(identity->waiter_state.data);
+  }
+};
+
+}  // namespace synchronization_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_SYNCHRONIZATION_INTERNAL_WAITER_BASE_H_
diff --git a/absl/synchronization/internal/waiter_test.cc b/absl/synchronization/internal/waiter_test.cc
new file mode 100644
index 00000000..992db29b
--- /dev/null
+++ b/absl/synchronization/internal/waiter_test.cc
@@ -0,0 +1,180 @@
+// Copyright 2023 The Abseil Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/synchronization/internal/waiter.h"
+
+#include <ctime>
+#include <iostream>
+#include <ostream>
+
+#include "absl/base/config.h"
+#include "absl/random/random.h"
+#include "absl/synchronization/internal/create_thread_identity.h"
+#include "absl/synchronization/internal/futex_waiter.h"
+#include "absl/synchronization/internal/kernel_timeout.h"
+#include "absl/synchronization/internal/pthread_waiter.h"
+#include "absl/synchronization/internal/sem_waiter.h"
+#include "absl/synchronization/internal/stdcpp_waiter.h"
+#include "absl/synchronization/internal/thread_pool.h"
+#include "absl/synchronization/internal/win32_waiter.h"
+#include "absl/time/clock.h"
+#include "absl/time/time.h"
+#include "gtest/gtest.h"
+
+// Test go/btm support by randomizing the value of clock_gettime() for
+// CLOCK_MONOTONIC. This works by overriding a weak symbol in glibc.
+// We should be resistant to this randomization when !SupportsSteadyClock().
+#if defined(__GOOGLE_GRTE_VERSION__) &&      \
+    !defined(ABSL_HAVE_ADDRESS_SANITIZER) && \
+    !defined(ABSL_HAVE_MEMORY_SANITIZER) &&  \
+    !defined(ABSL_HAVE_THREAD_SANITIZER)
+extern "C" int __clock_gettime(clockid_t c, struct timespec* ts);
+
+extern "C" int clock_gettime(clockid_t c, struct timespec* ts) {
+  if (c == CLOCK_MONOTONIC &&
+      !absl::synchronization_internal::KernelTimeout::SupportsSteadyClock()) {
+    absl::SharedBitGen gen;
+    ts->tv_sec = absl::Uniform(gen, 0, 1'000'000'000);
+    ts->tv_nsec = absl::Uniform(gen, 0, 1'000'000'000);
+    return 0;
+  }
+  return __clock_gettime(c, ts);
+}
+#endif
+
+namespace {
+
+TEST(Waiter, PrintPlatformImplementation) {
+  // Allows us to verify that the platform is using the expected implementation.
+  std::cout << absl::synchronization_internal::Waiter::kName << std::endl;
+}
+
+template <typename T>
+class WaiterTest : public ::testing::Test {
+ public:
+  // Waiter implementations assume that a ThreadIdentity has already been
+  // created.
+  WaiterTest() {
+    absl::synchronization_internal::GetOrCreateCurrentThreadIdentity();
+  }
+};
+
+TYPED_TEST_SUITE_P(WaiterTest);
+
+absl::Duration WithTolerance(absl::Duration d) { return d * 0.95; }
+
+TYPED_TEST_P(WaiterTest, WaitNoTimeout) {
+  absl::synchronization_internal::ThreadPool tp(1);
+  TypeParam waiter;
+  tp.Schedule([&]() {
+    // Include some `Poke()` calls to ensure they don't cause `waiter` to return
+    // from `Wait()`.
+    waiter.Poke();
+    absl::SleepFor(absl::Seconds(1));
+    waiter.Poke();
+    absl::SleepFor(absl::Seconds(1));
+    waiter.Post();
+  });
+  absl::Time start = absl::Now();
+  EXPECT_TRUE(
+      waiter.Wait(absl::synchronization_internal::KernelTimeout::Never()));
+  absl::Duration waited = absl::Now() - start;
+  EXPECT_GE(waited, WithTolerance(absl::Seconds(2)));
+}
+
+TYPED_TEST_P(WaiterTest, WaitDurationWoken) {
+  absl::synchronization_internal::ThreadPool tp(1);
+  TypeParam waiter;
+  tp.Schedule([&]() {
+    // Include some `Poke()` calls to ensure they don't cause `waiter` to return
+    // from `Wait()`.
+    waiter.Poke();
+    absl::SleepFor(absl::Milliseconds(500));
+    waiter.Post();
+  });
+  absl::Time start = absl::Now();
+  EXPECT_TRUE(waiter.Wait(
+      absl::synchronization_internal::KernelTimeout(absl::Seconds(10))));
+  absl::Duration waited = absl::Now() - start;
+  EXPECT_GE(waited, WithTolerance(absl::Milliseconds(500)));
+  EXPECT_LT(waited, absl::Seconds(2));
+}
+
+TYPED_TEST_P(WaiterTest, WaitTimeWoken) {
+  absl::synchronization_internal::ThreadPool tp(1);
+  TypeParam waiter;
+  tp.Schedule([&]() {
+    // Include some `Poke()` calls to ensure they don't cause `waiter` to return
+    // from `Wait()`.
+    waiter.Poke();
+    absl::SleepFor(absl::Milliseconds(500));
+    waiter.Post();
+  });
+  absl::Time start = absl::Now();
+  EXPECT_TRUE(waiter.Wait(absl::synchronization_internal::KernelTimeout(
+      start + absl::Seconds(10))));
+  absl::Duration waited = absl::Now() - start;
+  EXPECT_GE(waited, WithTolerance(absl::Milliseconds(500)));
+  EXPECT_LT(waited, absl::Seconds(2));
+}
+
+TYPED_TEST_P(WaiterTest, WaitDurationReached) {
+  TypeParam waiter;
+  absl::Time start = absl::Now();
+  EXPECT_FALSE(waiter.Wait(
+      absl::synchronization_internal::KernelTimeout(absl::Milliseconds(500))));
+  absl::Duration waited = absl::Now() - start;
+  EXPECT_GE(waited, WithTolerance(absl::Milliseconds(500)));
+  EXPECT_LT(waited, absl::Seconds(1));
+}
+
+TYPED_TEST_P(WaiterTest, WaitTimeReached) {
+  TypeParam waiter;
+  absl::Time start = absl::Now();
+  EXPECT_FALSE(waiter.Wait(absl::synchronization_internal::KernelTimeout(
+      start + absl::Milliseconds(500))));
+  absl::Duration waited = absl::Now() - start;
+  EXPECT_GE(waited, WithTolerance(absl::Milliseconds(500)));
+  EXPECT_LT(waited, absl::Seconds(1));
+}
+
+REGISTER_TYPED_TEST_SUITE_P(WaiterTest,
+                            WaitNoTimeout,
+                            WaitDurationWoken,
+                            WaitTimeWoken,
+                            WaitDurationReached,
+                            WaitTimeReached);
+
+#ifdef ABSL_INTERNAL_HAVE_FUTEX_WAITER
+INSTANTIATE_TYPED_TEST_SUITE_P(Futex, WaiterTest,
+                               absl::synchronization_internal::FutexWaiter);
+#endif
+#ifdef ABSL_INTERNAL_HAVE_PTHREAD_WAITER
+INSTANTIATE_TYPED_TEST_SUITE_P(Pthread, WaiterTest,
+                               absl::synchronization_internal::PthreadWaiter);
+#endif
+#ifdef ABSL_INTERNAL_HAVE_SEM_WAITER
+INSTANTIATE_TYPED_TEST_SUITE_P(Sem, WaiterTest,
+                               absl::synchronization_internal::SemWaiter);
+#endif
+#ifdef ABSL_INTERNAL_HAVE_WIN32_WAITER
+INSTANTIATE_TYPED_TEST_SUITE_P(Win32, WaiterTest,
+                               absl::synchronization_internal::Win32Waiter);
+#endif
+#ifdef ABSL_INTERNAL_HAVE_STDCPP_WAITER
+INSTANTIATE_TYPED_TEST_SUITE_P(Stdcpp, WaiterTest,
+                               absl::synchronization_internal::StdcppWaiter);
+#endif
+
+}  // namespace
diff --git a/absl/synchronization/internal/win32_waiter.cc b/absl/synchronization/internal/win32_waiter.cc
new file mode 100644
index 00000000..bd95ff08
--- /dev/null
+++ b/absl/synchronization/internal/win32_waiter.cc
@@ -0,0 +1,151 @@
+// Copyright 2023 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/synchronization/internal/win32_waiter.h"
+
+#ifdef ABSL_INTERNAL_HAVE_WIN32_WAITER
+
+#include <windows.h>
+
+#include "absl/base/config.h"
+#include "absl/base/internal/raw_logging.h"
+#include "absl/base/internal/thread_identity.h"
+#include "absl/base/optimization.h"
+#include "absl/synchronization/internal/kernel_timeout.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace synchronization_internal {
+
+#ifdef ABSL_INTERNAL_NEED_REDUNDANT_CONSTEXPR_DECL
+constexpr char Win32Waiter::kName[];
+#endif
+
+class Win32Waiter::WinHelper {
+ public:
+  static SRWLOCK *GetLock(Win32Waiter *w) {
+    return reinterpret_cast<SRWLOCK *>(&w->mu_storage_);
+  }
+
+  static CONDITION_VARIABLE *GetCond(Win32Waiter *w) {
+    return reinterpret_cast<CONDITION_VARIABLE *>(&w->cv_storage_);
+  }
+
+  static_assert(sizeof(SRWLOCK) == sizeof(void *),
+                "`mu_storage_` does not have the same size as SRWLOCK");
+  static_assert(alignof(SRWLOCK) == alignof(void *),
+                "`mu_storage_` does not have the same alignment as SRWLOCK");
+
+  static_assert(sizeof(CONDITION_VARIABLE) == sizeof(void *),
+                "`ABSL_CONDITION_VARIABLE_STORAGE` does not have the same size "
+                "as `CONDITION_VARIABLE`");
+  static_assert(
+      alignof(CONDITION_VARIABLE) == alignof(void *),
+      "`cv_storage_` does not have the same alignment as `CONDITION_VARIABLE`");
+
+  // The SRWLOCK and CONDITION_VARIABLE types must be trivially constructible
+  // and destructible because we never call their constructors or destructors.
+  static_assert(std::is_trivially_constructible<SRWLOCK>::value,
+                "The `SRWLOCK` type must be trivially constructible");
+  static_assert(
+      std::is_trivially_constructible<CONDITION_VARIABLE>::value,
+      "The `CONDITION_VARIABLE` type must be trivially constructible");
+  static_assert(std::is_trivially_destructible<SRWLOCK>::value,
+                "The `SRWLOCK` type must be trivially destructible");
+  static_assert(std::is_trivially_destructible<CONDITION_VARIABLE>::value,
+                "The `CONDITION_VARIABLE` type must be trivially destructible");
+};
+
+class LockHolder {
+ public:
+  explicit LockHolder(SRWLOCK* mu) : mu_(mu) {
+    AcquireSRWLockExclusive(mu_);
+  }
+
+  LockHolder(const LockHolder&) = delete;
+  LockHolder& operator=(const LockHolder&) = delete;
+
+  ~LockHolder() {
+    ReleaseSRWLockExclusive(mu_);
+  }
+
+ private:
+  SRWLOCK* mu_;
+};
+
+Win32Waiter::Win32Waiter() {
+  auto *mu = ::new (static_cast<void *>(&mu_storage_)) SRWLOCK;
+  auto *cv = ::new (static_cast<void *>(&cv_storage_)) CONDITION_VARIABLE;
+  InitializeSRWLock(mu);
+  InitializeConditionVariable(cv);
+  waiter_count_ = 0;
+  wakeup_count_ = 0;
+}
+
+bool Win32Waiter::Wait(KernelTimeout t) {
+  SRWLOCK *mu = WinHelper::GetLock(this);
+  CONDITION_VARIABLE *cv = WinHelper::GetCond(this);
+
+  LockHolder h(mu);
+  ++waiter_count_;
+
+  // Loop until we find a wakeup to consume or timeout.
+  // Note that, since the thread ticker is just reset, we don't need to check
+  // whether the thread is idle on the very first pass of the loop.
+  bool first_pass = true;
+  while (wakeup_count_ == 0) {
+    if (!first_pass) MaybeBecomeIdle();
+    // No wakeups available, time to wait.
+    if (!SleepConditionVariableSRW(cv, mu, t.InMillisecondsFromNow(), 0)) {
+      // GetLastError() returns a Win32 DWORD, but we assign to
+      // unsigned long to simplify the ABSL_RAW_LOG case below.  The uniform
+      // initialization guarantees this is not a narrowing conversion.
+      const unsigned long err{GetLastError()};  // NOLINT(runtime/int)
+      if (err == ERROR_TIMEOUT) {
+        --waiter_count_;
+        return false;
+      } else {
+        ABSL_RAW_LOG(FATAL, "SleepConditionVariableSRW failed: %lu", err);
+      }
+    }
+    first_pass = false;
+  }
+  // Consume a wakeup and we're done.
+  --wakeup_count_;
+  --waiter_count_;
+  return true;
+}
+
+void Win32Waiter::Post() {
+  LockHolder h(WinHelper::GetLock(this));
+  ++wakeup_count_;
+  InternalCondVarPoke();
+}
+
+void Win32Waiter::Poke() {
+  LockHolder h(WinHelper::GetLock(this));
+  InternalCondVarPoke();
+}
+
+void Win32Waiter::InternalCondVarPoke() {
+  if (waiter_count_ != 0) {
+    WakeConditionVariable(WinHelper::GetCond(this));
+  }
+}
+
+}  // namespace synchronization_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_INTERNAL_HAVE_WIN32_WAITER
diff --git a/absl/synchronization/internal/win32_waiter.h b/absl/synchronization/internal/win32_waiter.h
new file mode 100644
index 00000000..87eb617c
--- /dev/null
+++ b/absl/synchronization/internal/win32_waiter.h
@@ -0,0 +1,70 @@
+// Copyright 2023 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+#ifndef ABSL_SYNCHRONIZATION_INTERNAL_WIN32_WAITER_H_
+#define ABSL_SYNCHRONIZATION_INTERNAL_WIN32_WAITER_H_
+
+#ifdef _WIN32
+#include <sdkddkver.h>
+#endif
+
+#if defined(_WIN32) && _WIN32_WINNT >= _WIN32_WINNT_VISTA
+
+#include "absl/base/config.h"
+#include "absl/synchronization/internal/kernel_timeout.h"
+#include "absl/synchronization/internal/waiter_base.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace synchronization_internal {
+
+#define ABSL_INTERNAL_HAVE_WIN32_WAITER 1
+
+class Win32Waiter : public WaiterCrtp<Win32Waiter> {
+ public:
+  Win32Waiter();
+
+  bool Wait(KernelTimeout t);
+  void Post();
+  void Poke();
+
+  static constexpr char kName[] = "Win32Waiter";
+
+ private:
+  // WinHelper - Used to define utilities for accessing the lock and
+  // condition variable storage once the types are complete.
+  class WinHelper;
+
+  // REQUIRES: WinHelper::GetLock(this) must be held.
+  void InternalCondVarPoke();
+
+  // We can't include Windows.h in our headers, so we use aligned character
+  // buffers to define the storage of SRWLOCK and CONDITION_VARIABLE.
+  // SRW locks and condition variables do not need to be explicitly destroyed.
+  // https://docs.microsoft.com/en-us/windows/win32/api/synchapi/nf-synchapi-initializesrwlock
+  // https://stackoverflow.com/questions/28975958/why-does-windows-have-no-deleteconditionvariable-function-to-go-together-with
+  alignas(void*) unsigned char mu_storage_[sizeof(void*)];
+  alignas(void*) unsigned char cv_storage_[sizeof(void*)];
+  int waiter_count_;
+  int wakeup_count_;
+};
+
+}  // namespace synchronization_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // defined(_WIN32) && _WIN32_WINNT >= _WIN32_WINNT_VISTA
+
+#endif  // ABSL_SYNCHRONIZATION_INTERNAL_WIN32_WAITER_H_
diff --git a/absl/synchronization/lifetime_test.cc b/absl/synchronization/lifetime_test.cc
index e6274232..d5ce35a1 100644
--- a/absl/synchronization/lifetime_test.cc
+++ b/absl/synchronization/lifetime_test.cc
@@ -18,8 +18,8 @@
 
 #include "absl/base/attributes.h"
 #include "absl/base/const_init.h"
-#include "absl/base/internal/raw_logging.h"
 #include "absl/base/thread_annotations.h"
+#include "absl/log/check.h"
 #include "absl/synchronization/mutex.h"
 #include "absl/synchronization/notification.h"
 
@@ -35,20 +35,20 @@ namespace {
 // Thread two waits on 'notification', then sets 'state' inside the 'mutex',
 // signalling the change via 'condvar'.
 //
-// These tests use ABSL_RAW_CHECK to validate invariants, rather than EXPECT or
-// ASSERT from gUnit, because we need to invoke them during global destructors,
-// when gUnit teardown would have already begun.
+// These tests use CHECK to validate invariants, rather than EXPECT or ASSERT
+// from gUnit, because we need to invoke them during global destructors, when
+// gUnit teardown would have already begun.
 void ThreadOne(absl::Mutex* mutex, absl::CondVar* condvar,
                absl::Notification* notification, bool* state) {
   // Test that the notification is in a valid initial state.
-  ABSL_RAW_CHECK(!notification->HasBeenNotified(), "invalid Notification");
-  ABSL_RAW_CHECK(*state == false, "*state not initialized");
+  CHECK(!notification->HasBeenNotified()) << "invalid Notification";
+  CHECK(!*state) << "*state not initialized";
 
   {
     absl::MutexLock lock(mutex);
 
     notification->Notify();
-    ABSL_RAW_CHECK(notification->HasBeenNotified(), "invalid Notification");
+    CHECK(notification->HasBeenNotified()) << "invalid Notification";
 
     while (*state == false) {
       condvar->Wait(mutex);
@@ -58,11 +58,11 @@ void ThreadOne(absl::Mutex* mutex, absl::CondVar* condvar,
 
 void ThreadTwo(absl::Mutex* mutex, absl::CondVar* condvar,
                absl::Notification* notification, bool* state) {
-  ABSL_RAW_CHECK(*state == false, "*state not initialized");
+  CHECK(!*state) << "*state not initialized";
 
   // Wake thread one
   notification->WaitForNotification();
-  ABSL_RAW_CHECK(notification->HasBeenNotified(), "invalid Notification");
+  CHECK(notification->HasBeenNotified()) << "invalid Notification";
   {
     absl::MutexLock lock(mutex);
     *state = true;
diff --git a/absl/synchronization/mutex.cc b/absl/synchronization/mutex.cc
index 064ccb74..3aa5560a 100644
--- a/absl/synchronization/mutex.cc
+++ b/absl/synchronization/mutex.cc
@@ -35,10 +35,9 @@
 
 #include <algorithm>
 #include <atomic>
-#include <cinttypes>
 #include <cstddef>
+#include <cstdlib>
 #include <cstring>
-#include <iterator>
 #include <thread>  // NOLINT(build/c++11)
 
 #include "absl/base/attributes.h"
@@ -55,7 +54,6 @@
 #include "absl/base/internal/thread_identity.h"
 #include "absl/base/internal/tsan_mutex_interface.h"
 #include "absl/base/optimization.h"
-#include "absl/base/port.h"
 #include "absl/debugging/stacktrace.h"
 #include "absl/debugging/symbolize.h"
 #include "absl/synchronization/internal/graphcycles.h"
@@ -63,6 +61,7 @@
 #include "absl/time/time.h"
 
 using absl::base_internal::CurrentThreadIdentityIfPresent;
+using absl::base_internal::CycleClock;
 using absl::base_internal::PerThreadSynch;
 using absl::base_internal::SchedulingGuard;
 using absl::base_internal::ThreadIdentity;
@@ -98,18 +97,15 @@ ABSL_INTERNAL_ATOMIC_HOOK_ATTRIBUTES
 absl::base_internal::AtomicHook<void (*)(int64_t wait_cycles)>
     submit_profile_data;
 ABSL_INTERNAL_ATOMIC_HOOK_ATTRIBUTES absl::base_internal::AtomicHook<void (*)(
-    const char *msg, const void *obj, int64_t wait_cycles)>
+    const char* msg, const void* obj, int64_t wait_cycles)>
     mutex_tracer;
 ABSL_INTERNAL_ATOMIC_HOOK_ATTRIBUTES
-    absl::base_internal::AtomicHook<void (*)(const char *msg, const void *cv)>
-        cond_var_tracer;
-ABSL_INTERNAL_ATOMIC_HOOK_ATTRIBUTES absl::base_internal::AtomicHook<
-    bool (*)(const void *pc, char *out, int out_size)>
-    symbolizer(absl::Symbolize);
+absl::base_internal::AtomicHook<void (*)(const char* msg, const void* cv)>
+    cond_var_tracer;
 
 }  // namespace
 
-static inline bool EvalConditionAnnotated(const Condition *cond, Mutex *mu,
+static inline bool EvalConditionAnnotated(const Condition* cond, Mutex* mu,
                                           bool locking, bool trylock,
                                           bool read_lock);
 
@@ -117,19 +113,15 @@ void RegisterMutexProfiler(void (*fn)(int64_t wait_cycles)) {
   submit_profile_data.Store(fn);
 }
 
-void RegisterMutexTracer(void (*fn)(const char *msg, const void *obj,
+void RegisterMutexTracer(void (*fn)(const char* msg, const void* obj,
                                     int64_t wait_cycles)) {
   mutex_tracer.Store(fn);
 }
 
-void RegisterCondVarTracer(void (*fn)(const char *msg, const void *cv)) {
+void RegisterCondVarTracer(void (*fn)(const char* msg, const void* cv)) {
   cond_var_tracer.Store(fn);
 }
 
-void RegisterSymbolizer(bool (*fn)(const void *pc, char *out, int out_size)) {
-  symbolizer.Store(fn);
-}
-
 namespace {
 // Represents the strategy for spin and yield.
 // See the comment in GetMutexGlobals() for more information.
@@ -148,25 +140,24 @@ absl::Duration MeasureTimeToYield() {
   return absl::Now() - before;
 }
 
-const MutexGlobals &GetMutexGlobals() {
+const MutexGlobals& GetMutexGlobals() {
   ABSL_CONST_INIT static MutexGlobals data;
   absl::base_internal::LowLevelCallOnce(&data.once, [&]() {
-    const int num_cpus = absl::base_internal::NumCPUs();
-    data.spinloop_iterations = num_cpus > 1 ? 1500 : 0;
-    // If this a uniprocessor, only yield/sleep.
-    // Real-time threads are often unable to yield, so the sleep time needs
-    // to be long enough to keep the calling thread asleep until scheduling
-    // happens.
-    // If this is multiprocessor, allow spinning. If the mode is
-    // aggressive then spin many times before yielding.  If the mode is
-    // gentle then spin only a few times before yielding.  Aggressive spinning
-    // is used to ensure that an Unlock() call, which must get the spin lock
-    // for any thread to make progress gets it without undue delay.
-    if (num_cpus > 1) {
+    if (absl::base_internal::NumCPUs() > 1) {
+      // If this is multiprocessor, allow spinning. If the mode is
+      // aggressive then spin many times before yielding. If the mode is
+      // gentle then spin only a few times before yielding. Aggressive spinning
+      // is used to ensure that an Unlock() call, which must get the spin lock
+      // for any thread to make progress gets it without undue delay.
+      data.spinloop_iterations = 1500;
       data.mutex_sleep_spins[AGGRESSIVE] = 5000;
       data.mutex_sleep_spins[GENTLE] = 250;
       data.mutex_sleep_time = absl::Microseconds(10);
     } else {
+      // If this a uniprocessor, only yield/sleep. Real-time threads are often
+      // unable to yield, so the sleep time needs to be long enough to keep
+      // the calling thread asleep until scheduling happens.
+      data.spinloop_iterations = 0;
       data.mutex_sleep_spins[AGGRESSIVE] = 0;
       data.mutex_sleep_spins[GENTLE] = 0;
       data.mutex_sleep_time = MeasureTimeToYield() * 5;
@@ -219,8 +210,7 @@ static void AtomicSetBits(std::atomic<intptr_t>* pv, intptr_t bits,
     v = pv->load(std::memory_order_relaxed);
   } while ((v & bits) != bits &&
            ((v & wait_until_clear) != 0 ||
-            !pv->compare_exchange_weak(v, v | bits,
-                                       std::memory_order_release,
+            !pv->compare_exchange_weak(v, v | bits, std::memory_order_release,
                                        std::memory_order_relaxed)));
 }
 
@@ -235,8 +225,7 @@ static void AtomicClearBits(std::atomic<intptr_t>* pv, intptr_t bits,
     v = pv->load(std::memory_order_relaxed);
   } while ((v & bits) != 0 &&
            ((v & wait_until_clear) != 0 ||
-            !pv->compare_exchange_weak(v, v & ~bits,
-                                       std::memory_order_release,
+            !pv->compare_exchange_weak(v, v & ~bits, std::memory_order_release,
                                        std::memory_order_relaxed)));
 }
 
@@ -247,7 +236,7 @@ ABSL_CONST_INIT static absl::base_internal::SpinLock deadlock_graph_mu(
     absl::kConstInit, base_internal::SCHEDULE_KERNEL_ONLY);
 
 // Graph used to detect deadlocks.
-ABSL_CONST_INIT static GraphCycles *deadlock_graph
+ABSL_CONST_INIT static GraphCycles* deadlock_graph
     ABSL_GUARDED_BY(deadlock_graph_mu) ABSL_PT_GUARDED_BY(deadlock_graph_mu);
 
 //------------------------------------------------------------------
@@ -291,7 +280,7 @@ enum {                    // Event flags
 // Properties of the events.
 static const struct {
   int flags;
-  const char *msg;
+  const char* msg;
 } event_properties[] = {
     {SYNCH_F_LCK_W | SYNCH_F_TRY, "TryLock succeeded "},
     {0, "TryLock failed "},
@@ -316,12 +305,12 @@ ABSL_CONST_INIT static absl::base_internal::SpinLock synch_event_mu(
 // Can't be too small, as it's used for deadlock detection information.
 static constexpr uint32_t kNSynchEvent = 1031;
 
-static struct SynchEvent {     // this is a trivial hash table for the events
+static struct SynchEvent {  // this is a trivial hash table for the events
   // struct is freed when refcount reaches 0
   int refcount ABSL_GUARDED_BY(synch_event_mu);
 
   // buckets have linear, 0-terminated  chains
-  SynchEvent *next ABSL_GUARDED_BY(synch_event_mu);
+  SynchEvent* next ABSL_GUARDED_BY(synch_event_mu);
 
   // Constant after initialization
   uintptr_t masked_addr;  // object at this address is called "name"
@@ -329,13 +318,13 @@ static struct SynchEvent {     // this is a trivial hash table for the events
   // No explicit synchronization used.  Instead we assume that the
   // client who enables/disables invariants/logging on a Mutex does so
   // while the Mutex is not being concurrently accessed by others.
-  void (*invariant)(void *arg);  // called on each event
-  void *arg;            // first arg to (*invariant)()
-  bool log;             // logging turned on
+  void (*invariant)(void* arg);  // called on each event
+  void* arg;                     // first arg to (*invariant)()
+  bool log;                      // logging turned on
 
   // Constant after initialization
-  char name[1];         // actually longer---NUL-terminated string
-} * synch_event[kNSynchEvent] ABSL_GUARDED_BY(synch_event_mu);
+  char name[1];  // actually longer---NUL-terminated string
+}* synch_event[kNSynchEvent] ABSL_GUARDED_BY(synch_event_mu);
 
 // Ensure that the object at "addr" has a SynchEvent struct associated with it,
 // set "bits" in the word there (waiting until lockbit is clear before doing
@@ -344,11 +333,11 @@ static struct SynchEvent {     // this is a trivial hash table for the events
 // the string name is copied into it.
 // When used with a mutex, the caller should also ensure that kMuEvent
 // is set in the mutex word, and similarly for condition variables and kCVEvent.
-static SynchEvent *EnsureSynchEvent(std::atomic<intptr_t> *addr,
-                                    const char *name, intptr_t bits,
+static SynchEvent* EnsureSynchEvent(std::atomic<intptr_t>* addr,
+                                    const char* name, intptr_t bits,
                                     intptr_t lockbit) {
   uint32_t h = reinterpret_cast<uintptr_t>(addr) % kNSynchEvent;
-  SynchEvent *e;
+  SynchEvent* e;
   // first look for existing SynchEvent struct..
   synch_event_mu.Lock();
   for (e = synch_event[h];
@@ -360,9 +349,9 @@ static SynchEvent *EnsureSynchEvent(std::atomic<intptr_t> *addr,
       name = "";
     }
     size_t l = strlen(name);
-    e = reinterpret_cast<SynchEvent *>(
+    e = reinterpret_cast<SynchEvent*>(
         base_internal::LowLevelAlloc::Alloc(sizeof(*e) + l));
-    e->refcount = 2;    // one for return value, one for linked list
+    e->refcount = 2;  // one for return value, one for linked list
     e->masked_addr = base_internal::HidePtr(addr);
     e->invariant = nullptr;
     e->arg = nullptr;
@@ -372,19 +361,19 @@ static SynchEvent *EnsureSynchEvent(std::atomic<intptr_t> *addr,
     AtomicSetBits(addr, bits, lockbit);
     synch_event[h] = e;
   } else {
-    e->refcount++;      // for return value
+    e->refcount++;  // for return value
   }
   synch_event_mu.Unlock();
   return e;
 }
 
 // Deallocate the SynchEvent *e, whose refcount has fallen to zero.
-static void DeleteSynchEvent(SynchEvent *e) {
+static void DeleteSynchEvent(SynchEvent* e) {
   base_internal::LowLevelAlloc::Free(e);
 }
 
 // Decrement the reference count of *e, or do nothing if e==null.
-static void UnrefSynchEvent(SynchEvent *e) {
+static void UnrefSynchEvent(SynchEvent* e) {
   if (e != nullptr) {
     synch_event_mu.Lock();
     bool del = (--(e->refcount) == 0);
@@ -398,11 +387,11 @@ static void UnrefSynchEvent(SynchEvent *e) {
 // Forget the mapping from the object (Mutex or CondVar) at address addr
 // to SynchEvent object, and clear "bits" in its word (waiting until lockbit
 // is clear before doing so).
-static void ForgetSynchEvent(std::atomic<intptr_t> *addr, intptr_t bits,
+static void ForgetSynchEvent(std::atomic<intptr_t>* addr, intptr_t bits,
                              intptr_t lockbit) {
   uint32_t h = reinterpret_cast<uintptr_t>(addr) % kNSynchEvent;
-  SynchEvent **pe;
-  SynchEvent *e;
+  SynchEvent** pe;
+  SynchEvent* e;
   synch_event_mu.Lock();
   for (pe = &synch_event[h];
        (e = *pe) != nullptr && e->masked_addr != base_internal::HidePtr(addr);
@@ -423,9 +412,9 @@ static void ForgetSynchEvent(std::atomic<intptr_t> *addr, intptr_t bits,
 // Return a refcounted reference to the SynchEvent of the object at address
 // "addr", if any.  The pointer returned is valid until the UnrefSynchEvent() is
 // called.
-static SynchEvent *GetSynchEvent(const void *addr) {
+static SynchEvent* GetSynchEvent(const void* addr) {
   uint32_t h = reinterpret_cast<uintptr_t>(addr) % kNSynchEvent;
-  SynchEvent *e;
+  SynchEvent* e;
   synch_event_mu.Lock();
   for (e = synch_event[h];
        e != nullptr && e->masked_addr != base_internal::HidePtr(addr);
@@ -440,17 +429,17 @@ static SynchEvent *GetSynchEvent(const void *addr) {
 
 // Called when an event "ev" occurs on a Mutex of CondVar "obj"
 // if event recording is on
-static void PostSynchEvent(void *obj, int ev) {
-  SynchEvent *e = GetSynchEvent(obj);
+static void PostSynchEvent(void* obj, int ev) {
+  SynchEvent* e = GetSynchEvent(obj);
   // logging is on if event recording is on and either there's no event struct,
   // or it explicitly says to log
   if (e == nullptr || e->log) {
-    void *pcs[40];
+    void* pcs[40];
     int n = absl::GetStackTrace(pcs, ABSL_ARRAYSIZE(pcs), 1);
     // A buffer with enough space for the ASCII for all the PCs, even on a
     // 64-bit machine.
     char buffer[ABSL_ARRAYSIZE(pcs) * 24];
-    int pos = snprintf(buffer, sizeof (buffer), " @");
+    int pos = snprintf(buffer, sizeof(buffer), " @");
     for (int i = 0; i != n; i++) {
       int b = snprintf(&buffer[pos], sizeof(buffer) - static_cast<size_t>(pos),
                        " %p", pcs[i]);
@@ -472,13 +461,13 @@ static void PostSynchEvent(void *obj, int ev) {
     // get false positive race reports later.
     // Reuse EvalConditionAnnotated to properly call into user code.
     struct local {
-      static bool pred(SynchEvent *ev) {
+      static bool pred(SynchEvent* ev) {
         (*ev->invariant)(ev->arg);
         return false;
       }
     };
     Condition cond(&local::pred, e);
-    Mutex *mu = static_cast<Mutex *>(obj);
+    Mutex* mu = static_cast<Mutex*>(obj);
     const bool locking = (flags & SYNCH_F_UNLOCK) == 0;
     const bool trylock = (flags & SYNCH_F_TRY) != 0;
     const bool read_lock = (flags & SYNCH_F_R) != 0;
@@ -504,32 +493,32 @@ static void PostSynchEvent(void *obj, int ev) {
 // PerThreadSynch struct points at the most recent SynchWaitParams struct when
 // the thread is on a Mutex's waiter queue.
 struct SynchWaitParams {
-  SynchWaitParams(Mutex::MuHow how_arg, const Condition *cond_arg,
-                  KernelTimeout timeout_arg, Mutex *cvmu_arg,
-                  PerThreadSynch *thread_arg,
-                  std::atomic<intptr_t> *cv_word_arg)
+  SynchWaitParams(Mutex::MuHow how_arg, const Condition* cond_arg,
+                  KernelTimeout timeout_arg, Mutex* cvmu_arg,
+                  PerThreadSynch* thread_arg,
+                  std::atomic<intptr_t>* cv_word_arg)
       : how(how_arg),
         cond(cond_arg),
         timeout(timeout_arg),
         cvmu(cvmu_arg),
         thread(thread_arg),
         cv_word(cv_word_arg),
-        contention_start_cycles(base_internal::CycleClock::Now()),
+        contention_start_cycles(CycleClock::Now()),
         should_submit_contention_data(false) {}
 
   const Mutex::MuHow how;  // How this thread needs to wait.
-  const Condition *cond;  // The condition that this thread is waiting for.
-                          // In Mutex, this field is set to zero if a timeout
-                          // expires.
+  const Condition* cond;   // The condition that this thread is waiting for.
+                           // In Mutex, this field is set to zero if a timeout
+                           // expires.
   KernelTimeout timeout;  // timeout expiry---absolute time
                           // In Mutex, this field is set to zero if a timeout
                           // expires.
-  Mutex *const cvmu;      // used for transfer from cond var to mutex
-  PerThreadSynch *const thread;  // thread that is waiting
+  Mutex* const cvmu;      // used for transfer from cond var to mutex
+  PerThreadSynch* const thread;  // thread that is waiting
 
   // If not null, thread should be enqueued on the CondVar whose state
   // word is cv_word instead of queueing normally on the Mutex.
-  std::atomic<intptr_t> *cv_word;
+  std::atomic<intptr_t>* cv_word;
 
   int64_t contention_start_cycles;  // Time (in cycles) when this thread started
                                     // to contend for the mutex.
@@ -537,12 +526,12 @@ struct SynchWaitParams {
 };
 
 struct SynchLocksHeld {
-  int n;              // number of valid entries in locks[]
-  bool overflow;      // true iff we overflowed the array at some point
+  int n;          // number of valid entries in locks[]
+  bool overflow;  // true iff we overflowed the array at some point
   struct {
-    Mutex *mu;        // lock acquired
-    int32_t count;      // times acquired
-    GraphId id;       // deadlock_graph id of acquired lock
+    Mutex* mu;      // lock acquired
+    int32_t count;  // times acquired
+    GraphId id;     // deadlock_graph id of acquired lock
   } locks[40];
   // If a thread overfills the array during deadlock detection, we
   // continue, discarding information as needed.  If no overflow has
@@ -552,11 +541,11 @@ struct SynchLocksHeld {
 
 // A sentinel value in lists that is not 0.
 // A 0 value is used to mean "not on a list".
-static PerThreadSynch *const kPerThreadSynchNull =
-  reinterpret_cast<PerThreadSynch *>(1);
+static PerThreadSynch* const kPerThreadSynchNull =
+    reinterpret_cast<PerThreadSynch*>(1);
 
-static SynchLocksHeld *LocksHeldAlloc() {
-  SynchLocksHeld *ret = reinterpret_cast<SynchLocksHeld *>(
+static SynchLocksHeld* LocksHeldAlloc() {
+  SynchLocksHeld* ret = reinterpret_cast<SynchLocksHeld*>(
       base_internal::LowLevelAlloc::Alloc(sizeof(SynchLocksHeld)));
   ret->n = 0;
   ret->overflow = false;
@@ -564,24 +553,24 @@ static SynchLocksHeld *LocksHeldAlloc() {
 }
 
 // Return the PerThreadSynch-struct for this thread.
-static PerThreadSynch *Synch_GetPerThread() {
-  ThreadIdentity *identity = GetOrCreateCurrentThreadIdentity();
+static PerThreadSynch* Synch_GetPerThread() {
+  ThreadIdentity* identity = GetOrCreateCurrentThreadIdentity();
   return &identity->per_thread_synch;
 }
 
-static PerThreadSynch *Synch_GetPerThreadAnnotated(Mutex *mu) {
+static PerThreadSynch* Synch_GetPerThreadAnnotated(Mutex* mu) {
   if (mu) {
     ABSL_TSAN_MUTEX_PRE_DIVERT(mu, 0);
   }
-  PerThreadSynch *w = Synch_GetPerThread();
+  PerThreadSynch* w = Synch_GetPerThread();
   if (mu) {
     ABSL_TSAN_MUTEX_POST_DIVERT(mu, 0);
   }
   return w;
 }
 
-static SynchLocksHeld *Synch_GetAllLocks() {
-  PerThreadSynch *s = Synch_GetPerThread();
+static SynchLocksHeld* Synch_GetAllLocks() {
+  PerThreadSynch* s = Synch_GetPerThread();
   if (s->all_locks == nullptr) {
     s->all_locks = LocksHeldAlloc();  // Freed by ReclaimThreadIdentity.
   }
@@ -589,7 +578,7 @@ static SynchLocksHeld *Synch_GetAllLocks() {
 }
 
 // Post on "w"'s associated PerThreadSem.
-void Mutex::IncrementSynchSem(Mutex *mu, PerThreadSynch *w) {
+void Mutex::IncrementSynchSem(Mutex* mu, PerThreadSynch* w) {
   if (mu) {
     ABSL_TSAN_MUTEX_PRE_DIVERT(mu, 0);
     // We miss synchronization around passing PerThreadSynch between threads
@@ -605,7 +594,7 @@ void Mutex::IncrementSynchSem(Mutex *mu, PerThreadSynch *w) {
 }
 
 // Wait on "w"'s associated PerThreadSem; returns false if timeout expired.
-bool Mutex::DecrementSynchSem(Mutex *mu, PerThreadSynch *w, KernelTimeout t) {
+bool Mutex::DecrementSynchSem(Mutex* mu, PerThreadSynch* w, KernelTimeout t) {
   if (mu) {
     ABSL_TSAN_MUTEX_PRE_DIVERT(mu, 0);
   }
@@ -626,7 +615,7 @@ bool Mutex::DecrementSynchSem(Mutex *mu, PerThreadSynch *w, KernelTimeout t) {
 // Mutex code checking that the "waitp" field has not been reused.
 void Mutex::InternalAttemptToUseMutexInFatalSignalHandler() {
   // Fix the per-thread state only if it exists.
-  ThreadIdentity *identity = CurrentThreadIdentityIfPresent();
+  ThreadIdentity* identity = CurrentThreadIdentityIfPresent();
   if (identity != nullptr) {
     identity->per_thread_synch.suppress_fatal_errors = true;
   }
@@ -635,21 +624,6 @@ void Mutex::InternalAttemptToUseMutexInFatalSignalHandler() {
                                  std::memory_order_release);
 }
 
-// --------------------------time support
-
-// Return the current time plus the timeout.  Use the same clock as
-// PerThreadSem::Wait() for consistency.  Unfortunately, we don't have
-// such a choice when a deadline is given directly.
-static absl::Time DeadlineFromTimeout(absl::Duration timeout) {
-#ifndef _WIN32
-  struct timeval tv;
-  gettimeofday(&tv, nullptr);
-  return absl::TimeFromTimeval(tv) + timeout;
-#else
-  return absl::Now() + timeout;
-#endif
-}
-
 // --------------------------Mutexes
 
 // In the layout below, the msb of the bottom byte is currently unused.  Also,
@@ -660,24 +634,29 @@ static absl::Time DeadlineFromTimeout(absl::Duration timeout) {
 //    bit-twiddling trick in Mutex::Unlock().
 //  o kMuWriter / kMuReader == kMuWrWait / kMuWait,
 //    to enable the bit-twiddling trick in CheckForMutexCorruption().
-static const intptr_t kMuReader      = 0x0001L;  // a reader holds the lock
-static const intptr_t kMuDesig       = 0x0002L;  // there's a designated waker
-static const intptr_t kMuWait        = 0x0004L;  // threads are waiting
-static const intptr_t kMuWriter      = 0x0008L;  // a writer holds the lock
-static const intptr_t kMuEvent       = 0x0010L;  // record this mutex's events
+static const intptr_t kMuReader = 0x0001L;  // a reader holds the lock
+// There's a designated waker.
 // INVARIANT1:  there's a thread that was blocked on the mutex, is
 // no longer, yet has not yet acquired the mutex.  If there's a
 // designated waker, all threads can avoid taking the slow path in
 // unlock because the designated waker will subsequently acquire
 // the lock and wake someone.  To maintain INVARIANT1 the bit is
 // set when a thread is unblocked(INV1a), and threads that were
-// unblocked reset the bit when they either acquire or re-block
-// (INV1b).
-static const intptr_t kMuWrWait      = 0x0020L;  // runnable writer is waiting
-                                                 // for a reader
-static const intptr_t kMuSpin        = 0x0040L;  // spinlock protects wait list
-static const intptr_t kMuLow         = 0x00ffL;  // mask all mutex bits
-static const intptr_t kMuHigh        = ~kMuLow;  // mask pointer/reader count
+// unblocked reset the bit when they either acquire or re-block (INV1b).
+static const intptr_t kMuDesig = 0x0002L;
+static const intptr_t kMuWait = 0x0004L;    // threads are waiting
+static const intptr_t kMuWriter = 0x0008L;  // a writer holds the lock
+static const intptr_t kMuEvent = 0x0010L;   // record this mutex's events
+// Runnable writer is waiting for a reader.
+// If set, new readers will not lock the mutex to avoid writer starvation.
+// Note: if a reader has higher priority than the writer, it will still lock
+// the mutex ahead of the waiting writer, but in a very inefficient manner:
+// the reader will first queue itself and block, but then the last unlocking
+// reader will wake it.
+static const intptr_t kMuWrWait = 0x0020L;
+static const intptr_t kMuSpin = 0x0040L;  // spinlock protects wait list
+static const intptr_t kMuLow = 0x00ffL;   // mask all mutex bits
+static const intptr_t kMuHigh = ~kMuLow;  // mask pointer/reader count
 
 // Hack to make constant values available to gdb pretty printer
 enum {
@@ -773,8 +752,8 @@ Mutex::~Mutex() {
   ABSL_TSAN_MUTEX_DESTROY(this, __tsan_mutex_not_static);
 }
 
-void Mutex::EnableDebugLog(const char *name) {
-  SynchEvent *e = EnsureSynchEvent(&this->mu_, name, kMuEvent, kMuSpin);
+void Mutex::EnableDebugLog(const char* name) {
+  SynchEvent* e = EnsureSynchEvent(&this->mu_, name, kMuEvent, kMuSpin);
   e->log = true;
   UnrefSynchEvent(e);
 }
@@ -783,11 +762,10 @@ void EnableMutexInvariantDebugging(bool enabled) {
   synch_check_invariants.store(enabled, std::memory_order_release);
 }
 
-void Mutex::EnableInvariantDebugging(void (*invariant)(void *),
-                                     void *arg) {
+void Mutex::EnableInvariantDebugging(void (*invariant)(void*), void* arg) {
   if (synch_check_invariants.load(std::memory_order_acquire) &&
       invariant != nullptr) {
-    SynchEvent *e = EnsureSynchEvent(&this->mu_, nullptr, kMuEvent, kMuSpin);
+    SynchEvent* e = EnsureSynchEvent(&this->mu_, nullptr, kMuEvent, kMuSpin);
     e->invariant = invariant;
     e->arg = arg;
     UnrefSynchEvent(e);
@@ -803,15 +781,15 @@ void SetMutexDeadlockDetectionMode(OnDeadlockCycle mode) {
 // waiters with the same condition, type of lock, and thread priority.
 //
 // Requires that x and y be waiting on the same Mutex queue.
-static bool MuEquivalentWaiter(PerThreadSynch *x, PerThreadSynch *y) {
+static bool MuEquivalentWaiter(PerThreadSynch* x, PerThreadSynch* y) {
   return x->waitp->how == y->waitp->how && x->priority == y->priority &&
          Condition::GuaranteedEqual(x->waitp->cond, y->waitp->cond);
 }
 
 // Given the contents of a mutex word containing a PerThreadSynch pointer,
 // return the pointer.
-static inline PerThreadSynch *GetPerThreadSynch(intptr_t v) {
-  return reinterpret_cast<PerThreadSynch *>(v & kMuHigh);
+static inline PerThreadSynch* GetPerThreadSynch(intptr_t v) {
+  return reinterpret_cast<PerThreadSynch*>(v & kMuHigh);
 }
 
 // The next several routines maintain the per-thread next and skip fields
@@ -869,17 +847,17 @@ static inline PerThreadSynch *GetPerThreadSynch(intptr_t v) {
 // except those in the added node and the former "head" node.  This implies
 // that the new node is added after head, and so must be the new head or the
 // new front of the queue.
-static PerThreadSynch *Skip(PerThreadSynch *x) {
-  PerThreadSynch *x0 = nullptr;
-  PerThreadSynch *x1 = x;
-  PerThreadSynch *x2 = x->skip;
+static PerThreadSynch* Skip(PerThreadSynch* x) {
+  PerThreadSynch* x0 = nullptr;
+  PerThreadSynch* x1 = x;
+  PerThreadSynch* x2 = x->skip;
   if (x2 != nullptr) {
     // Each iteration attempts to advance sequence (x0,x1,x2) to next sequence
     // such that   x1 == x0->skip && x2 == x1->skip
     while ((x0 = x1, x1 = x2, x2 = x2->skip) != nullptr) {
-      x0->skip = x2;      // short-circuit skip from x0 to x2
+      x0->skip = x2;  // short-circuit skip from x0 to x2
     }
-    x->skip = x1;         // short-circuit skip from x to result
+    x->skip = x1;  // short-circuit skip from x to result
   }
   return x1;
 }
@@ -888,7 +866,7 @@ static PerThreadSynch *Skip(PerThreadSynch *x) {
 // The latter is going to be removed out of order, because of a timeout.
 // Check whether "ancestor" has a skip field pointing to "to_be_removed",
 // and fix it if it does.
-static void FixSkip(PerThreadSynch *ancestor, PerThreadSynch *to_be_removed) {
+static void FixSkip(PerThreadSynch* ancestor, PerThreadSynch* to_be_removed) {
   if (ancestor->skip == to_be_removed) {  // ancestor->skip left dangling
     if (to_be_removed->skip != nullptr) {
       ancestor->skip = to_be_removed->skip;  // can skip past to_be_removed
@@ -900,7 +878,7 @@ static void FixSkip(PerThreadSynch *ancestor, PerThreadSynch *to_be_removed) {
   }
 }
 
-static void CondVarEnqueue(SynchWaitParams *waitp);
+static void CondVarEnqueue(SynchWaitParams* waitp);
 
 // Enqueue thread "waitp->thread" on a waiter queue.
 // Called with mutex spinlock held if head != nullptr
@@ -921,8 +899,8 @@ static void CondVarEnqueue(SynchWaitParams *waitp);
 // returned. This mechanism is used by CondVar to queue a thread on the
 // condition variable queue instead of the mutex queue in implementing Wait().
 // In this case, Enqueue() can return nullptr (if head==nullptr).
-static PerThreadSynch *Enqueue(PerThreadSynch *head,
-                               SynchWaitParams *waitp, intptr_t mu, int flags) {
+static PerThreadSynch* Enqueue(PerThreadSynch* head, SynchWaitParams* waitp,
+                               intptr_t mu, int flags) {
   // If we have been given a cv_word, call CondVarEnqueue() and return
   // the previous head of the Mutex waiter queue.
   if (waitp->cv_word != nullptr) {
@@ -930,42 +908,43 @@ static PerThreadSynch *Enqueue(PerThreadSynch *head,
     return head;
   }
 
-  PerThreadSynch *s = waitp->thread;
+  PerThreadSynch* s = waitp->thread;
   ABSL_RAW_CHECK(
       s->waitp == nullptr ||    // normal case
           s->waitp == waitp ||  // Fer()---transfer from condition variable
           s->suppress_fatal_errors,
       "detected illegal recursion into Mutex code");
   s->waitp = waitp;
-  s->skip = nullptr;             // maintain skip invariant (see above)
-  s->may_skip = true;            // always true on entering queue
-  s->wake = false;               // not being woken
+  s->skip = nullptr;   // maintain skip invariant (see above)
+  s->may_skip = true;  // always true on entering queue
+  s->wake = false;     // not being woken
   s->cond_waiter = ((flags & kMuIsCond) != 0);
+#ifdef ABSL_HAVE_PTHREAD_GETSCHEDPARAM
+  int64_t now_cycles = CycleClock::Now();
+  if (s->next_priority_read_cycles < now_cycles) {
+    // Every so often, update our idea of the thread's priority.
+    // pthread_getschedparam() is 5% of the block/wakeup time;
+    // CycleClock::Now() is 0.5%.
+    int policy;
+    struct sched_param param;
+    const int err = pthread_getschedparam(pthread_self(), &policy, &param);
+    if (err != 0) {
+      ABSL_RAW_LOG(ERROR, "pthread_getschedparam failed: %d", err);
+    } else {
+      s->priority = param.sched_priority;
+      s->next_priority_read_cycles =
+          now_cycles + static_cast<int64_t>(CycleClock::Frequency());
+    }
+  }
+#endif
   if (head == nullptr) {         // s is the only waiter
     s->next = s;                 // it's the only entry in the cycle
     s->readers = mu;             // reader count is from mu word
     s->maybe_unlocking = false;  // no one is searching an empty list
     head = s;                    // s is new head
   } else {
-    PerThreadSynch *enqueue_after = nullptr;  // we'll put s after this element
+    PerThreadSynch* enqueue_after = nullptr;  // we'll put s after this element
 #ifdef ABSL_HAVE_PTHREAD_GETSCHEDPARAM
-    int64_t now_cycles = base_internal::CycleClock::Now();
-    if (s->next_priority_read_cycles < now_cycles) {
-      // Every so often, update our idea of the thread's priority.
-      // pthread_getschedparam() is 5% of the block/wakeup time;
-      // base_internal::CycleClock::Now() is 0.5%.
-      int policy;
-      struct sched_param param;
-      const int err = pthread_getschedparam(pthread_self(), &policy, &param);
-      if (err != 0) {
-        ABSL_RAW_LOG(ERROR, "pthread_getschedparam failed: %d", err);
-      } else {
-        s->priority = param.sched_priority;
-        s->next_priority_read_cycles =
-            now_cycles +
-            static_cast<int64_t>(base_internal::CycleClock::Frequency());
-      }
-    }
     if (s->priority > head->priority) {  // s's priority is above head's
       // try to put s in priority-fifo order, or failing that at the front.
       if (!head->maybe_unlocking) {
@@ -975,20 +954,20 @@ static PerThreadSynch *Enqueue(PerThreadSynch *head,
         // Within a skip chain, all waiters have the same priority, so we can
         // skip forward through the chains until we find one with a lower
         // priority than the waiter to be enqueued.
-        PerThreadSynch *advance_to = head;    // next value of enqueue_after
+        PerThreadSynch* advance_to = head;  // next value of enqueue_after
         do {
           enqueue_after = advance_to;
           // (side-effect: optimizes skip chain)
           advance_to = Skip(enqueue_after->next);
         } while (s->priority <= advance_to->priority);
-              // termination guaranteed because s->priority > head->priority
-              // and head is the end of a skip chain
+        // termination guaranteed because s->priority > head->priority
+        // and head is the end of a skip chain
       } else if (waitp->how == kExclusive &&
                  Condition::GuaranteedEqual(waitp->cond, nullptr)) {
         // An unlocker could be scanning the queue, but we know it will recheck
         // the queue front for writers that have no condition, which is what s
         // is, so an insert at front is safe.
-        enqueue_after = head;       // add after head, at front
+        enqueue_after = head;  // add after head, at front
       }
     }
 #endif
@@ -1013,12 +992,12 @@ static PerThreadSynch *Enqueue(PerThreadSynch *head,
         enqueue_after->skip = enqueue_after->next;
       }
       if (MuEquivalentWaiter(s, s->next)) {  // s->may_skip is known to be true
-        s->skip = s->next;                // s may skip to its successor
+        s->skip = s->next;                   // s may skip to its successor
       }
-    } else {   // enqueue not done any other way, so
-               // we're inserting s at the back
+    } else {  // enqueue not done any other way, so
+              // we're inserting s at the back
       // s will become new head; copy data from head into it
-      s->next = head->next;        // add s after head
+      s->next = head->next;  // add s after head
       head->next = s;
       s->readers = head->readers;  // reader count is from previous head
       s->maybe_unlocking = head->maybe_unlocking;  // same for unlock hint
@@ -1037,17 +1016,17 @@ static PerThreadSynch *Enqueue(PerThreadSynch *head,
 // whose last element is head.  The new head element is returned, or null
 // if the list is made empty.
 // Dequeue is called with both spinlock and Mutex held.
-static PerThreadSynch *Dequeue(PerThreadSynch *head, PerThreadSynch *pw) {
-  PerThreadSynch *w = pw->next;
-  pw->next = w->next;         // snip w out of list
-  if (head == w) {            // we removed the head
+static PerThreadSynch* Dequeue(PerThreadSynch* head, PerThreadSynch* pw) {
+  PerThreadSynch* w = pw->next;
+  pw->next = w->next;                 // snip w out of list
+  if (head == w) {                    // we removed the head
     head = (pw == w) ? nullptr : pw;  // either emptied list, or pw is new head
   } else if (pw != head && MuEquivalentWaiter(pw, pw->next)) {
     // pw can skip to its new successor
     if (pw->next->skip !=
         nullptr) {  // either skip to its successors skip target
       pw->skip = pw->next->skip;
-    } else {                   // or to pw's successor
+    } else {  // or to pw's successor
       pw->skip = pw->next;
     }
   }
@@ -1060,27 +1039,27 @@ static PerThreadSynch *Dequeue(PerThreadSynch *head, PerThreadSynch *pw) {
 // singly-linked list wake_list in the order found.   Assumes that
 // there is only one such element if the element has how == kExclusive.
 // Return the new head.
-static PerThreadSynch *DequeueAllWakeable(PerThreadSynch *head,
-                                          PerThreadSynch *pw,
-                                          PerThreadSynch **wake_tail) {
-  PerThreadSynch *orig_h = head;
-  PerThreadSynch *w = pw->next;
+static PerThreadSynch* DequeueAllWakeable(PerThreadSynch* head,
+                                          PerThreadSynch* pw,
+                                          PerThreadSynch** wake_tail) {
+  PerThreadSynch* orig_h = head;
+  PerThreadSynch* w = pw->next;
   bool skipped = false;
   do {
-    if (w->wake) {                    // remove this element
+    if (w->wake) {  // remove this element
       ABSL_RAW_CHECK(pw->skip == nullptr, "bad skip in DequeueAllWakeable");
       // we're removing pw's successor so either pw->skip is zero or we should
       // already have removed pw since if pw->skip!=null, pw has the same
       // condition as w.
       head = Dequeue(head, pw);
-      w->next = *wake_tail;           // keep list terminated
-      *wake_tail = w;                 // add w to wake_list;
-      wake_tail = &w->next;           // next addition to end
+      w->next = *wake_tail;               // keep list terminated
+      *wake_tail = w;                     // add w to wake_list;
+      wake_tail = &w->next;               // next addition to end
       if (w->waitp->how == kExclusive) {  // wake at most 1 writer
         break;
       }
-    } else {                // not waking this one; skip
-      pw = Skip(w);       // skip as much as possible
+    } else {         // not waking this one; skip
+      pw = Skip(w);  // skip as much as possible
       skipped = true;
     }
     w = pw->next;
@@ -1098,7 +1077,7 @@ static PerThreadSynch *DequeueAllWakeable(PerThreadSynch *head,
 
 // Try to remove thread s from the list of waiters on this mutex.
 // Does nothing if s is not on the waiter list.
-void Mutex::TryRemove(PerThreadSynch *s) {
+void Mutex::TryRemove(PerThreadSynch* s) {
   SchedulingGuard::ScopedDisable disable_rescheduling;
   intptr_t v = mu_.load(std::memory_order_relaxed);
   // acquire spinlock & lock
@@ -1106,16 +1085,16 @@ void Mutex::TryRemove(PerThreadSynch *s) {
       mu_.compare_exchange_strong(v, v | kMuSpin | kMuWriter,
                                   std::memory_order_acquire,
                                   std::memory_order_relaxed)) {
-    PerThreadSynch *h = GetPerThreadSynch(v);
+    PerThreadSynch* h = GetPerThreadSynch(v);
     if (h != nullptr) {
-      PerThreadSynch *pw = h;   // pw is w's predecessor
-      PerThreadSynch *w;
+      PerThreadSynch* pw = h;  // pw is w's predecessor
+      PerThreadSynch* w;
       if ((w = pw->next) != s) {  // search for thread,
         do {                      // processing at least one element
           // If the current element isn't equivalent to the waiter to be
           // removed, we can skip the entire chain.
           if (!MuEquivalentWaiter(s, w)) {
-            pw = Skip(w);                // so skip all that won't match
+            pw = Skip(w);  // so skip all that won't match
             // we don't have to worry about dangling skip fields
             // in the threads we skipped; none can point to s
             // because they are in a different equivalence class.
@@ -1127,7 +1106,7 @@ void Mutex::TryRemove(PerThreadSynch *s) {
           // process the first thread again.
         } while ((w = pw->next) != s && pw != h);
       }
-      if (w == s) {                 // found thread; remove it
+      if (w == s) {  // found thread; remove it
         // pw->skip may be non-zero here; the loop above ensured that
         // no ancestor of s can skip to s, so removal is safe anyway.
         h = Dequeue(h, pw);
@@ -1136,16 +1115,15 @@ void Mutex::TryRemove(PerThreadSynch *s) {
       }
     }
     intptr_t nv;
-    do {                        // release spinlock and lock
+    do {  // release spinlock and lock
       v = mu_.load(std::memory_order_relaxed);
       nv = v & (kMuDesig | kMuEvent);
       if (h != nullptr) {
         nv |= kMuWait | reinterpret_cast<intptr_t>(h);
-        h->readers = 0;            // we hold writer lock
+        h->readers = 0;              // we hold writer lock
         h->maybe_unlocking = false;  // finished unlocking
       }
-    } while (!mu_.compare_exchange_weak(v, nv,
-                                        std::memory_order_release,
+    } while (!mu_.compare_exchange_weak(v, nv, std::memory_order_release,
                                         std::memory_order_relaxed));
   }
 }
@@ -1155,7 +1133,7 @@ void Mutex::TryRemove(PerThreadSynch *s) {
 // if the wait extends past the absolute time specified, even if "s" is still
 // on the mutex queue.  In this case, remove "s" from the queue and return
 // true, otherwise return false.
-void Mutex::Block(PerThreadSynch *s) {
+void Mutex::Block(PerThreadSynch* s) {
   while (s->state.load(std::memory_order_acquire) == PerThreadSynch::kQueued) {
     if (!DecrementSynchSem(this, s, s->waitp->timeout)) {
       // After a timeout, we go into a spin loop until we remove ourselves
@@ -1174,7 +1152,7 @@ void Mutex::Block(PerThreadSynch *s) {
         // is not on the queue.
         this->TryRemove(s);
       }
-      s->waitp->timeout = KernelTimeout::Never();      // timeout is satisfied
+      s->waitp->timeout = KernelTimeout::Never();  // timeout is satisfied
       s->waitp->cond = nullptr;  // condition no longer relevant for wakeups
     }
   }
@@ -1184,8 +1162,8 @@ void Mutex::Block(PerThreadSynch *s) {
 }
 
 // Wake thread w, and return the next thread in the list.
-PerThreadSynch *Mutex::Wakeup(PerThreadSynch *w) {
-  PerThreadSynch *next = w->next;
+PerThreadSynch* Mutex::Wakeup(PerThreadSynch* w) {
+  PerThreadSynch* next = w->next;
   w->next = nullptr;
   w->state.store(PerThreadSynch::kAvailable, std::memory_order_release);
   IncrementSynchSem(this, w);
@@ -1193,7 +1171,7 @@ PerThreadSynch *Mutex::Wakeup(PerThreadSynch *w) {
   return next;
 }
 
-static GraphId GetGraphIdLocked(Mutex *mu)
+static GraphId GetGraphIdLocked(Mutex* mu)
     ABSL_EXCLUSIVE_LOCKS_REQUIRED(deadlock_graph_mu) {
   if (!deadlock_graph) {  // (re)create the deadlock graph.
     deadlock_graph =
@@ -1203,7 +1181,7 @@ static GraphId GetGraphIdLocked(Mutex *mu)
   return deadlock_graph->GetId(mu);
 }
 
-static GraphId GetGraphId(Mutex *mu) ABSL_LOCKS_EXCLUDED(deadlock_graph_mu) {
+static GraphId GetGraphId(Mutex* mu) ABSL_LOCKS_EXCLUDED(deadlock_graph_mu) {
   deadlock_graph_mu.Lock();
   GraphId id = GetGraphIdLocked(mu);
   deadlock_graph_mu.Unlock();
@@ -1213,7 +1191,7 @@ static GraphId GetGraphId(Mutex *mu) ABSL_LOCKS_EXCLUDED(deadlock_graph_mu) {
 // Record a lock acquisition.  This is used in debug mode for deadlock
 // detection.  The held_locks pointer points to the relevant data
 // structure for each case.
-static void LockEnter(Mutex* mu, GraphId id, SynchLocksHeld *held_locks) {
+static void LockEnter(Mutex* mu, GraphId id, SynchLocksHeld* held_locks) {
   int n = held_locks->n;
   int i = 0;
   while (i != n && held_locks->locks[i].id != id) {
@@ -1237,7 +1215,7 @@ static void LockEnter(Mutex* mu, GraphId id, SynchLocksHeld *held_locks) {
 // eventually followed by a call to LockLeave(mu, id, x) by the same thread.
 // It does not process the event if is not needed when deadlock detection is
 // disabled.
-static void LockLeave(Mutex* mu, GraphId id, SynchLocksHeld *held_locks) {
+static void LockLeave(Mutex* mu, GraphId id, SynchLocksHeld* held_locks) {
   int n = held_locks->n;
   int i = 0;
   while (i != n && held_locks->locks[i].id != id) {
@@ -1252,11 +1230,11 @@ static void LockLeave(Mutex* mu, GraphId id, SynchLocksHeld *held_locks) {
         i++;
       }
       if (i == n) {  // mu missing means releasing unheld lock
-        SynchEvent *mu_events = GetSynchEvent(mu);
+        SynchEvent* mu_events = GetSynchEvent(mu);
         ABSL_RAW_LOG(FATAL,
                      "thread releasing lock it does not hold: %p %s; "
                      ,
-                     static_cast<void *>(mu),
+                     static_cast<void*>(mu),
                      mu_events == nullptr ? "" : mu_events->name);
       }
     }
@@ -1273,7 +1251,7 @@ static void LockLeave(Mutex* mu, GraphId id, SynchLocksHeld *held_locks) {
 }
 
 // Call LockEnter() if in debug mode and deadlock detection is enabled.
-static inline void DebugOnlyLockEnter(Mutex *mu) {
+static inline void DebugOnlyLockEnter(Mutex* mu) {
   if (kDebugMode) {
     if (synch_deadlock_detection.load(std::memory_order_acquire) !=
         OnDeadlockCycle::kIgnore) {
@@ -1283,7 +1261,7 @@ static inline void DebugOnlyLockEnter(Mutex *mu) {
 }
 
 // Call LockEnter() if in debug mode and deadlock detection is enabled.
-static inline void DebugOnlyLockEnter(Mutex *mu, GraphId id) {
+static inline void DebugOnlyLockEnter(Mutex* mu, GraphId id) {
   if (kDebugMode) {
     if (synch_deadlock_detection.load(std::memory_order_acquire) !=
         OnDeadlockCycle::kIgnore) {
@@ -1293,7 +1271,7 @@ static inline void DebugOnlyLockEnter(Mutex *mu, GraphId id) {
 }
 
 // Call LockLeave() if in debug mode and deadlock detection is enabled.
-static inline void DebugOnlyLockLeave(Mutex *mu) {
+static inline void DebugOnlyLockLeave(Mutex* mu) {
   if (kDebugMode) {
     if (synch_deadlock_detection.load(std::memory_order_acquire) !=
         OnDeadlockCycle::kIgnore) {
@@ -1302,9 +1280,9 @@ static inline void DebugOnlyLockLeave(Mutex *mu) {
   }
 }
 
-static char *StackString(void **pcs, int n, char *buf, int maxlen,
+static char* StackString(void** pcs, int n, char* buf, int maxlen,
                          bool symbolize) {
-  static const int kSymLen = 200;
+  static constexpr int kSymLen = 200;
   char sym[kSymLen];
   int len = 0;
   for (int i = 0; i != n; i++) {
@@ -1312,7 +1290,7 @@ static char *StackString(void **pcs, int n, char *buf, int maxlen,
       return buf;
     size_t count = static_cast<size_t>(maxlen - len);
     if (symbolize) {
-      if (!symbolizer(pcs[i], sym, kSymLen)) {
+      if (!absl::Symbolize(pcs[i], sym, kSymLen)) {
         sym[0] = '\0';
       }
       snprintf(buf + len, count, "%s\t@ %p %s\n", (i == 0 ? "\n" : ""), pcs[i],
@@ -1325,15 +1303,17 @@ static char *StackString(void **pcs, int n, char *buf, int maxlen,
   return buf;
 }
 
-static char *CurrentStackString(char *buf, int maxlen, bool symbolize) {
-  void *pcs[40];
+static char* CurrentStackString(char* buf, int maxlen, bool symbolize) {
+  void* pcs[40];
   return StackString(pcs, absl::GetStackTrace(pcs, ABSL_ARRAYSIZE(pcs), 2), buf,
                      maxlen, symbolize);
 }
 
 namespace {
-enum { kMaxDeadlockPathLen = 10 };  // maximum length of a deadlock cycle;
-                                    // a path this long would be remarkable
+enum {
+  kMaxDeadlockPathLen = 10
+};  // maximum length of a deadlock cycle;
+    // a path this long would be remarkable
 // Buffers required to report a deadlock.
 // We do not allocate them on stack to avoid large stack frame.
 struct DeadlockReportBuffers {
@@ -1343,11 +1323,11 @@ struct DeadlockReportBuffers {
 
 struct ScopedDeadlockReportBuffers {
   ScopedDeadlockReportBuffers() {
-    b = reinterpret_cast<DeadlockReportBuffers *>(
+    b = reinterpret_cast<DeadlockReportBuffers*>(
         base_internal::LowLevelAlloc::Alloc(sizeof(*b)));
   }
   ~ScopedDeadlockReportBuffers() { base_internal::LowLevelAlloc::Free(b); }
-  DeadlockReportBuffers *b;
+  DeadlockReportBuffers* b;
 };
 
 // Helper to pass to GraphCycles::UpdateStackTrace.
@@ -1358,13 +1338,13 @@ int GetStack(void** stack, int max_depth) {
 
 // Called in debug mode when a thread is about to acquire a lock in a way that
 // may block.
-static GraphId DeadlockCheck(Mutex *mu) {
+static GraphId DeadlockCheck(Mutex* mu) {
   if (synch_deadlock_detection.load(std::memory_order_acquire) ==
       OnDeadlockCycle::kIgnore) {
     return InvalidGraphId();
   }
 
-  SynchLocksHeld *all_locks = Synch_GetAllLocks();
+  SynchLocksHeld* all_locks = Synch_GetAllLocks();
 
   absl::base_internal::SpinLockHolder lock(&deadlock_graph_mu);
   const GraphId mu_id = GetGraphIdLocked(mu);
@@ -1386,8 +1366,8 @@ static GraphId DeadlockCheck(Mutex *mu) {
   // For each other mutex already held by this thread:
   for (int i = 0; i != all_locks->n; i++) {
     const GraphId other_node_id = all_locks->locks[i].id;
-    const Mutex *other =
-        static_cast<const Mutex *>(deadlock_graph->Ptr(other_node_id));
+    const Mutex* other =
+        static_cast<const Mutex*>(deadlock_graph->Ptr(other_node_id));
     if (other == nullptr) {
       // Ignore stale lock
       continue;
@@ -1396,7 +1376,7 @@ static GraphId DeadlockCheck(Mutex *mu) {
     // Add the acquired-before edge to the graph.
     if (!deadlock_graph->InsertEdge(other_node_id, mu_id)) {
       ScopedDeadlockReportBuffers scoped_buffers;
-      DeadlockReportBuffers *b = scoped_buffers.b;
+      DeadlockReportBuffers* b = scoped_buffers.b;
       static int number_of_reported_deadlocks = 0;
       number_of_reported_deadlocks++;
       // Symbolize only 2 first deadlock report to avoid huge slowdowns.
@@ -1407,37 +1387,40 @@ static GraphId DeadlockCheck(Mutex *mu) {
       for (int j = 0; j != all_locks->n; j++) {
         void* pr = deadlock_graph->Ptr(all_locks->locks[j].id);
         if (pr != nullptr) {
-          snprintf(b->buf + len, sizeof (b->buf) - len, " %p", pr);
+          snprintf(b->buf + len, sizeof(b->buf) - len, " %p", pr);
           len += strlen(&b->buf[len]);
         }
       }
       ABSL_RAW_LOG(ERROR,
                    "Acquiring absl::Mutex %p while holding %s; a cycle in the "
                    "historical lock ordering graph has been observed",
-                   static_cast<void *>(mu), b->buf);
+                   static_cast<void*>(mu), b->buf);
       ABSL_RAW_LOG(ERROR, "Cycle: ");
-      int path_len = deadlock_graph->FindPath(
-          mu_id, other_node_id, ABSL_ARRAYSIZE(b->path), b->path);
-      for (int j = 0; j != path_len; j++) {
+      int path_len = deadlock_graph->FindPath(mu_id, other_node_id,
+                                              ABSL_ARRAYSIZE(b->path), b->path);
+      for (int j = 0; j != path_len && j != ABSL_ARRAYSIZE(b->path); j++) {
         GraphId id = b->path[j];
-        Mutex *path_mu = static_cast<Mutex *>(deadlock_graph->Ptr(id));
+        Mutex* path_mu = static_cast<Mutex*>(deadlock_graph->Ptr(id));
         if (path_mu == nullptr) continue;
         void** stack;
         int depth = deadlock_graph->GetStackTrace(id, &stack);
         snprintf(b->buf, sizeof(b->buf),
-                 "mutex@%p stack: ", static_cast<void *>(path_mu));
+                 "mutex@%p stack: ", static_cast<void*>(path_mu));
         StackString(stack, depth, b->buf + strlen(b->buf),
                     static_cast<int>(sizeof(b->buf) - strlen(b->buf)),
                     symbolize);
         ABSL_RAW_LOG(ERROR, "%s", b->buf);
       }
+      if (path_len > static_cast<int>(ABSL_ARRAYSIZE(b->path))) {
+        ABSL_RAW_LOG(ERROR, "(long cycle; list truncated)");
+      }
       if (synch_deadlock_detection.load(std::memory_order_acquire) ==
           OnDeadlockCycle::kAbort) {
         deadlock_graph_mu.Unlock();  // avoid deadlock in fatal sighandler
         ABSL_RAW_LOG(FATAL, "dying due to potential deadlock");
         return mu_id;
       }
-      break;   // report at most one potential deadlock per acquisition
+      break;  // report at most one potential deadlock per acquisition
     }
   }
 
@@ -1446,7 +1429,7 @@ static GraphId DeadlockCheck(Mutex *mu) {
 
 // Invoke DeadlockCheck() iff we're in debug mode and
 // deadlock checking has been enabled.
-static inline GraphId DebugOnlyDeadlockCheck(Mutex *mu) {
+static inline GraphId DebugOnlyDeadlockCheck(Mutex* mu) {
   if (kDebugMode && synch_deadlock_detection.load(std::memory_order_acquire) !=
                         OnDeadlockCycle::kIgnore) {
     return DeadlockCheck(mu);
@@ -1473,13 +1456,13 @@ void Mutex::AssertNotHeld() const {
       (mu_.load(std::memory_order_relaxed) & (kMuWriter | kMuReader)) != 0 &&
       synch_deadlock_detection.load(std::memory_order_acquire) !=
           OnDeadlockCycle::kIgnore) {
-    GraphId id = GetGraphId(const_cast<Mutex *>(this));
-    SynchLocksHeld *locks = Synch_GetAllLocks();
+    GraphId id = GetGraphId(const_cast<Mutex*>(this));
+    SynchLocksHeld* locks = Synch_GetAllLocks();
     for (int i = 0; i != locks->n; i++) {
       if (locks->locks[i].id == id) {
-        SynchEvent *mu_events = GetSynchEvent(this);
+        SynchEvent* mu_events = GetSynchEvent(this);
         ABSL_RAW_LOG(FATAL, "thread should not hold mutex %p %s",
-                     static_cast<const void *>(this),
+                     static_cast<const void*>(this),
                      (mu_events == nullptr ? "" : mu_events->name));
       }
     }
@@ -1492,8 +1475,8 @@ static bool TryAcquireWithSpinning(std::atomic<intptr_t>* mu) {
   int c = GetMutexGlobals().spinloop_iterations;
   do {  // do/while somewhat faster on AMD
     intptr_t v = mu->load(std::memory_order_relaxed);
-    if ((v & (kMuReader|kMuEvent)) != 0) {
-      return false;  // a reader or tracing -> give up
+    if ((v & (kMuReader | kMuEvent)) != 0) {
+      return false;                       // a reader or tracing -> give up
     } else if (((v & kMuWriter) == 0) &&  // no holder -> try to acquire
                mu->compare_exchange_strong(v, kMuWriter | v,
                                            std::memory_order_acquire,
@@ -1510,8 +1493,7 @@ void Mutex::Lock() {
   intptr_t v = mu_.load(std::memory_order_relaxed);
   // try fast acquire, then spin loop
   if ((v & (kMuWriter | kMuReader | kMuEvent)) != 0 ||
-      !mu_.compare_exchange_strong(v, kMuWriter | v,
-                                   std::memory_order_acquire,
+      !mu_.compare_exchange_strong(v, kMuWriter | v, std::memory_order_acquire,
                                    std::memory_order_relaxed)) {
     // try spin acquire, then slow loop
     if (!TryAcquireWithSpinning(&this->mu_)) {
@@ -1537,7 +1519,7 @@ void Mutex::ReaderLock() {
   ABSL_TSAN_MUTEX_POST_LOCK(this, __tsan_mutex_read_lock, 0);
 }
 
-void Mutex::LockWhen(const Condition &cond) {
+void Mutex::LockWhen(const Condition& cond) {
   ABSL_TSAN_MUTEX_PRE_LOCK(this, 0);
   GraphId id = DebugOnlyDeadlockCheck(this);
   this->LockSlow(kExclusive, &cond, 0);
@@ -1545,21 +1527,26 @@ void Mutex::LockWhen(const Condition &cond) {
   ABSL_TSAN_MUTEX_POST_LOCK(this, 0, 0);
 }
 
-bool Mutex::LockWhenWithTimeout(const Condition &cond, absl::Duration timeout) {
-  return LockWhenWithDeadline(cond, DeadlineFromTimeout(timeout));
+bool Mutex::LockWhenWithTimeout(const Condition& cond, absl::Duration timeout) {
+  ABSL_TSAN_MUTEX_PRE_LOCK(this, 0);
+  GraphId id = DebugOnlyDeadlockCheck(this);
+  bool res = LockSlowWithDeadline(kExclusive, &cond, KernelTimeout(timeout), 0);
+  DebugOnlyLockEnter(this, id);
+  ABSL_TSAN_MUTEX_POST_LOCK(this, 0, 0);
+  return res;
 }
 
-bool Mutex::LockWhenWithDeadline(const Condition &cond, absl::Time deadline) {
+bool Mutex::LockWhenWithDeadline(const Condition& cond, absl::Time deadline) {
   ABSL_TSAN_MUTEX_PRE_LOCK(this, 0);
   GraphId id = DebugOnlyDeadlockCheck(this);
-  bool res = LockSlowWithDeadline(kExclusive, &cond,
-                                  KernelTimeout(deadline), 0);
+  bool res =
+      LockSlowWithDeadline(kExclusive, &cond, KernelTimeout(deadline), 0);
   DebugOnlyLockEnter(this, id);
   ABSL_TSAN_MUTEX_POST_LOCK(this, 0, 0);
   return res;
 }
 
-void Mutex::ReaderLockWhen(const Condition &cond) {
+void Mutex::ReaderLockWhen(const Condition& cond) {
   ABSL_TSAN_MUTEX_PRE_LOCK(this, __tsan_mutex_read_lock);
   GraphId id = DebugOnlyDeadlockCheck(this);
   this->LockSlow(kShared, &cond, 0);
@@ -1567,12 +1554,17 @@ void Mutex::ReaderLockWhen(const Condition &cond) {
   ABSL_TSAN_MUTEX_POST_LOCK(this, __tsan_mutex_read_lock, 0);
 }
 
-bool Mutex::ReaderLockWhenWithTimeout(const Condition &cond,
+bool Mutex::ReaderLockWhenWithTimeout(const Condition& cond,
                                       absl::Duration timeout) {
-  return ReaderLockWhenWithDeadline(cond, DeadlineFromTimeout(timeout));
+  ABSL_TSAN_MUTEX_PRE_LOCK(this, __tsan_mutex_read_lock);
+  GraphId id = DebugOnlyDeadlockCheck(this);
+  bool res = LockSlowWithDeadline(kShared, &cond, KernelTimeout(timeout), 0);
+  DebugOnlyLockEnter(this, id);
+  ABSL_TSAN_MUTEX_POST_LOCK(this, __tsan_mutex_read_lock, 0);
+  return res;
 }
 
-bool Mutex::ReaderLockWhenWithDeadline(const Condition &cond,
+bool Mutex::ReaderLockWhenWithDeadline(const Condition& cond,
                                        absl::Time deadline) {
   ABSL_TSAN_MUTEX_PRE_LOCK(this, __tsan_mutex_read_lock);
   GraphId id = DebugOnlyDeadlockCheck(this);
@@ -1582,23 +1574,34 @@ bool Mutex::ReaderLockWhenWithDeadline(const Condition &cond,
   return res;
 }
 
-void Mutex::Await(const Condition &cond) {
-  if (cond.Eval()) {    // condition already true; nothing to do
+void Mutex::Await(const Condition& cond) {
+  if (cond.Eval()) {  // condition already true; nothing to do
     if (kDebugMode) {
       this->AssertReaderHeld();
     }
-  } else {              // normal case
+  } else {  // normal case
     ABSL_RAW_CHECK(this->AwaitCommon(cond, KernelTimeout::Never()),
                    "condition untrue on return from Await");
   }
 }
 
-bool Mutex::AwaitWithTimeout(const Condition &cond, absl::Duration timeout) {
-  return AwaitWithDeadline(cond, DeadlineFromTimeout(timeout));
+bool Mutex::AwaitWithTimeout(const Condition& cond, absl::Duration timeout) {
+  if (cond.Eval()) {  // condition already true; nothing to do
+    if (kDebugMode) {
+      this->AssertReaderHeld();
+    }
+    return true;
+  }
+
+  KernelTimeout t{timeout};
+  bool res = this->AwaitCommon(cond, t);
+  ABSL_RAW_CHECK(res || t.has_timeout(),
+                 "condition untrue on return from Await");
+  return res;
 }
 
-bool Mutex::AwaitWithDeadline(const Condition &cond, absl::Time deadline) {
-  if (cond.Eval()) {      // condition already true; nothing to do
+bool Mutex::AwaitWithDeadline(const Condition& cond, absl::Time deadline) {
+  if (cond.Eval()) {  // condition already true; nothing to do
     if (kDebugMode) {
       this->AssertReaderHeld();
     }
@@ -1612,14 +1615,14 @@ bool Mutex::AwaitWithDeadline(const Condition &cond, absl::Time deadline) {
   return res;
 }
 
-bool Mutex::AwaitCommon(const Condition &cond, KernelTimeout t) {
+bool Mutex::AwaitCommon(const Condition& cond, KernelTimeout t) {
   this->AssertReaderHeld();
   MuHow how =
       (mu_.load(std::memory_order_relaxed) & kMuWriter) ? kExclusive : kShared;
   ABSL_TSAN_MUTEX_PRE_UNLOCK(this, TsanFlags(how));
-  SynchWaitParams waitp(
-      how, &cond, t, nullptr /*no cvmu*/, Synch_GetPerThreadAnnotated(this),
-      nullptr /*no cv_word*/);
+  SynchWaitParams waitp(how, &cond, t, nullptr /*no cvmu*/,
+                        Synch_GetPerThreadAnnotated(this),
+                        nullptr /*no cv_word*/);
   int flags = kMuHasBlocked;
   if (!Condition::GuaranteedEqual(&cond, nullptr)) {
     flags |= kMuIsCond;
@@ -1639,14 +1642,13 @@ bool Mutex::TryLock() {
   ABSL_TSAN_MUTEX_PRE_LOCK(this, __tsan_mutex_try_lock);
   intptr_t v = mu_.load(std::memory_order_relaxed);
   if ((v & (kMuWriter | kMuReader | kMuEvent)) == 0 &&  // try fast acquire
-      mu_.compare_exchange_strong(v, kMuWriter | v,
-                                  std::memory_order_acquire,
+      mu_.compare_exchange_strong(v, kMuWriter | v, std::memory_order_acquire,
                                   std::memory_order_relaxed)) {
     DebugOnlyLockEnter(this);
     ABSL_TSAN_MUTEX_POST_LOCK(this, __tsan_mutex_try_lock, 0);
     return true;
   }
-  if ((v & kMuEvent) != 0) {              // we're recording events
+  if ((v & kMuEvent) != 0) {                      // we're recording events
     if ((v & kExclusive->slow_need_zero) == 0 &&  // try fast acquire
         mu_.compare_exchange_strong(
             v, (kExclusive->fast_or | v) + kExclusive->fast_add,
@@ -1672,7 +1674,7 @@ bool Mutex::ReaderTryLock() {
   // changing (typically because the reader count changes) under the CAS.  We
   // limit the number of attempts to avoid having to think about livelock.
   int loop_limit = 5;
-  while ((v & (kMuWriter|kMuWait|kMuEvent)) == 0 && loop_limit != 0) {
+  while ((v & (kMuWriter | kMuWait | kMuEvent)) == 0 && loop_limit != 0) {
     if (mu_.compare_exchange_strong(v, (kMuReader | v) + kMuOne,
                                     std::memory_order_acquire,
                                     std::memory_order_relaxed)) {
@@ -1684,7 +1686,7 @@ bool Mutex::ReaderTryLock() {
     loop_limit--;
     v = mu_.load(std::memory_order_relaxed);
   }
-  if ((v & kMuEvent) != 0) {   // we're recording events
+  if ((v & kMuEvent) != 0) {  // we're recording events
     loop_limit = 5;
     while ((v & kShared->slow_need_zero) == 0 && loop_limit != 0) {
       if (mu_.compare_exchange_strong(v, (kMuReader | v) + kMuOne,
@@ -1723,7 +1725,7 @@ void Mutex::Unlock() {
   // should_try_cas is whether we'll try a compare-and-swap immediately.
   // NOTE: optimized out when kDebugMode is false.
   bool should_try_cas = ((v & (kMuEvent | kMuWriter)) == kMuWriter &&
-                          (v & (kMuWait | kMuDesig)) != kMuWait);
+                         (v & (kMuWait | kMuDesig)) != kMuWait);
   // But, we can use an alternate computation of it, that compilers
   // currently don't find on their own.  When that changes, this function
   // can be simplified.
@@ -1740,10 +1742,9 @@ void Mutex::Unlock() {
                  static_cast<long long>(v), static_cast<long long>(x),
                  static_cast<long long>(y));
   }
-  if (x < y &&
-      mu_.compare_exchange_strong(v, v & ~(kMuWrWait | kMuWriter),
-                                  std::memory_order_release,
-                                  std::memory_order_relaxed)) {
+  if (x < y && mu_.compare_exchange_strong(v, v & ~(kMuWrWait | kMuWriter),
+                                           std::memory_order_release,
+                                           std::memory_order_relaxed)) {
     // fast writer release (writer with no waiters or with designated waker)
   } else {
     this->UnlockSlow(nullptr /*no waitp*/);  // take slow path
@@ -1753,7 +1754,7 @@ void Mutex::Unlock() {
 
 // Requires v to represent a reader-locked state.
 static bool ExactlyOneReader(intptr_t v) {
-  assert((v & (kMuWriter|kMuReader)) == kMuReader);
+  assert((v & (kMuWriter | kMuReader)) == kMuReader);
   assert((v & kMuHigh) != 0);
   // The more straightforward "(v & kMuHigh) == kMuOne" also works, but
   // on some architectures the following generates slightly smaller code.
@@ -1766,12 +1767,11 @@ void Mutex::ReaderUnlock() {
   ABSL_TSAN_MUTEX_PRE_UNLOCK(this, __tsan_mutex_read_lock);
   DebugOnlyLockLeave(this);
   intptr_t v = mu_.load(std::memory_order_relaxed);
-  assert((v & (kMuWriter|kMuReader)) == kMuReader);
-  if ((v & (kMuReader|kMuWait|kMuEvent)) == kMuReader) {
+  assert((v & (kMuWriter | kMuReader)) == kMuReader);
+  if ((v & (kMuReader | kMuWait | kMuEvent)) == kMuReader) {
     // fast reader release (reader with no waiters)
-    intptr_t clear = ExactlyOneReader(v) ? kMuReader|kMuOne : kMuOne;
-    if (mu_.compare_exchange_strong(v, v - clear,
-                                    std::memory_order_release,
+    intptr_t clear = ExactlyOneReader(v) ? kMuReader | kMuOne : kMuOne;
+    if (mu_.compare_exchange_strong(v, v - clear, std::memory_order_release,
                                     std::memory_order_relaxed)) {
       ABSL_TSAN_MUTEX_POST_UNLOCK(this, __tsan_mutex_read_lock);
       return;
@@ -1810,7 +1810,7 @@ static intptr_t IgnoreWaitingWritersMask(int flag) {
 }
 
 // Internal version of LockWhen().  See LockSlowWithDeadline()
-ABSL_ATTRIBUTE_NOINLINE void Mutex::LockSlow(MuHow how, const Condition *cond,
+ABSL_ATTRIBUTE_NOINLINE void Mutex::LockSlow(MuHow how, const Condition* cond,
                                              int flags) {
   ABSL_RAW_CHECK(
       this->LockSlowWithDeadline(how, cond, KernelTimeout::Never(), flags),
@@ -1818,7 +1818,7 @@ ABSL_ATTRIBUTE_NOINLINE void Mutex::LockSlow(MuHow how, const Condition *cond,
 }
 
 // Compute cond->Eval() and tell race detectors that we do it under mutex mu.
-static inline bool EvalConditionAnnotated(const Condition *cond, Mutex *mu,
+static inline bool EvalConditionAnnotated(const Condition* cond, Mutex* mu,
                                           bool locking, bool trylock,
                                           bool read_lock) {
   // Delicate annotation dance.
@@ -1868,7 +1868,7 @@ static inline bool EvalConditionAnnotated(const Condition *cond, Mutex *mu,
 // tsan). As the result there is no tsan-visible synchronization between the
 // addition and this thread. So if we would enable race detection here,
 // it would race with the predicate initialization.
-static inline bool EvalConditionIgnored(Mutex *mu, const Condition *cond) {
+static inline bool EvalConditionIgnored(Mutex* mu, const Condition* cond) {
   // Memory accesses are already ignored inside of lock/unlock operations,
   // but synchronization operations are also ignored. When we evaluate the
   // predicate we must ignore only memory accesses but not synchronization,
@@ -1893,7 +1893,7 @@ static inline bool EvalConditionIgnored(Mutex *mu, const Condition *cond) {
 //   obstruct this call
 // - kMuIsCond indicates that this is a conditional acquire (condition variable,
 //   Await,  LockWhen) so contention profiling should be suppressed.
-bool Mutex::LockSlowWithDeadline(MuHow how, const Condition *cond,
+bool Mutex::LockSlowWithDeadline(MuHow how, const Condition* cond,
                                  KernelTimeout t, int flags) {
   intptr_t v = mu_.load(std::memory_order_relaxed);
   bool unlock = false;
@@ -1910,9 +1910,9 @@ bool Mutex::LockSlowWithDeadline(MuHow how, const Condition *cond,
     }
     unlock = true;
   }
-  SynchWaitParams waitp(
-      how, cond, t, nullptr /*no cvmu*/, Synch_GetPerThreadAnnotated(this),
-      nullptr /*no cv_word*/);
+  SynchWaitParams waitp(how, cond, t, nullptr /*no cvmu*/,
+                        Synch_GetPerThreadAnnotated(this),
+                        nullptr /*no cv_word*/);
   if (!Condition::GuaranteedEqual(cond, nullptr)) {
     flags |= kMuIsCond;
   }
@@ -1953,20 +1953,20 @@ static void CheckForMutexCorruption(intptr_t v, const char* label) {
   if (ABSL_PREDICT_TRUE((w & (w << 3) & (kMuWriter | kMuWrWait)) == 0)) return;
   RAW_CHECK_FMT((v & (kMuWriter | kMuReader)) != (kMuWriter | kMuReader),
                 "%s: Mutex corrupt: both reader and writer lock held: %p",
-                label, reinterpret_cast<void *>(v));
+                label, reinterpret_cast<void*>(v));
   RAW_CHECK_FMT((v & (kMuWait | kMuWrWait)) != kMuWrWait,
-                "%s: Mutex corrupt: waiting writer with no waiters: %p",
-                label, reinterpret_cast<void *>(v));
+                "%s: Mutex corrupt: waiting writer with no waiters: %p", label,
+                reinterpret_cast<void*>(v));
   assert(false);
 }
 
-void Mutex::LockSlowLoop(SynchWaitParams *waitp, int flags) {
+void Mutex::LockSlowLoop(SynchWaitParams* waitp, int flags) {
   SchedulingGuard::ScopedDisable disable_rescheduling;
   int c = 0;
   intptr_t v = mu_.load(std::memory_order_relaxed);
   if ((v & kMuEvent) != 0) {
-    PostSynchEvent(this,
-         waitp->how == kExclusive?  SYNCH_EV_LOCK: SYNCH_EV_READERLOCK);
+    PostSynchEvent(
+        this, waitp->how == kExclusive ? SYNCH_EV_LOCK : SYNCH_EV_READERLOCK);
   }
   ABSL_RAW_CHECK(
       waitp->thread->waitp == nullptr || waitp->thread->suppress_fatal_errors,
@@ -1991,11 +1991,11 @@ void Mutex::LockSlowLoop(SynchWaitParams *waitp, int flags) {
         flags |= kMuHasBlocked;
         c = 0;
       }
-    } else {                      // need to access waiter list
+    } else {  // need to access waiter list
       bool dowait = false;
-      if ((v & (kMuSpin|kMuWait)) == 0) {   // no waiters
+      if ((v & (kMuSpin | kMuWait)) == 0) {  // no waiters
         // This thread tries to become the one and only waiter.
-        PerThreadSynch *new_h = Enqueue(nullptr, waitp, v, flags);
+        PerThreadSynch* new_h = Enqueue(nullptr, waitp, v, flags);
         intptr_t nv =
             (v & ClearDesignatedWakerMask(flags & kMuHasBlocked) & kMuLow) |
             kMuWait;
@@ -2007,7 +2007,7 @@ void Mutex::LockSlowLoop(SynchWaitParams *waitp, int flags) {
                 v, reinterpret_cast<intptr_t>(new_h) | nv,
                 std::memory_order_release, std::memory_order_relaxed)) {
           dowait = true;
-        } else {            // attempted Enqueue() failed
+        } else {  // attempted Enqueue() failed
           // zero out the waitp field set by Enqueue()
           waitp->thread->waitp = nullptr;
         }
@@ -2020,9 +2020,9 @@ void Mutex::LockSlowLoop(SynchWaitParams *waitp, int flags) {
                 (v & ClearDesignatedWakerMask(flags & kMuHasBlocked)) |
                     kMuSpin | kMuReader,
                 std::memory_order_acquire, std::memory_order_relaxed)) {
-          PerThreadSynch *h = GetPerThreadSynch(v);
-          h->readers += kMuOne;       // inc reader count in waiter
-          do {                        // release spinlock
+          PerThreadSynch* h = GetPerThreadSynch(v);
+          h->readers += kMuOne;  // inc reader count in waiter
+          do {                   // release spinlock
             v = mu_.load(std::memory_order_relaxed);
           } while (!mu_.compare_exchange_weak(v, (v & ~kMuSpin) | kMuReader,
                                               std::memory_order_release,
@@ -2032,7 +2032,7 @@ void Mutex::LockSlowLoop(SynchWaitParams *waitp, int flags) {
                                      waitp->how == kShared)) {
             break;  // we timed out, or condition true, so return
           }
-          this->UnlockSlow(waitp);           // got lock but condition false
+          this->UnlockSlow(waitp);  // got lock but condition false
           this->Block(waitp->thread);
           flags |= kMuHasBlocked;
           c = 0;
@@ -2043,18 +2043,19 @@ void Mutex::LockSlowLoop(SynchWaitParams *waitp, int flags) {
                      (v & ClearDesignatedWakerMask(flags & kMuHasBlocked)) |
                          kMuSpin | kMuWait,
                      std::memory_order_acquire, std::memory_order_relaxed)) {
-        PerThreadSynch *h = GetPerThreadSynch(v);
-        PerThreadSynch *new_h = Enqueue(h, waitp, v, flags);
+        PerThreadSynch* h = GetPerThreadSynch(v);
+        PerThreadSynch* new_h = Enqueue(h, waitp, v, flags);
         intptr_t wr_wait = 0;
         ABSL_RAW_CHECK(new_h != nullptr, "Enqueue to list failed");
         if (waitp->how == kExclusive && (v & kMuReader) != 0) {
-          wr_wait = kMuWrWait;      // give priority to a waiting writer
+          wr_wait = kMuWrWait;  // give priority to a waiting writer
         }
-        do {                        // release spinlock
+        do {  // release spinlock
           v = mu_.load(std::memory_order_relaxed);
         } while (!mu_.compare_exchange_weak(
-            v, (v & (kMuLow & ~kMuSpin)) | kMuWait | wr_wait |
-            reinterpret_cast<intptr_t>(new_h),
+            v,
+            (v & (kMuLow & ~kMuSpin)) | kMuWait | wr_wait |
+                reinterpret_cast<intptr_t>(new_h),
             std::memory_order_release, std::memory_order_relaxed));
         dowait = true;
       }
@@ -2074,9 +2075,9 @@ void Mutex::LockSlowLoop(SynchWaitParams *waitp, int flags) {
       waitp->thread->waitp == nullptr || waitp->thread->suppress_fatal_errors,
       "detected illegal recursion into Mutex code");
   if ((v & kMuEvent) != 0) {
-    PostSynchEvent(this,
-                   waitp->how == kExclusive? SYNCH_EV_LOCK_RETURNING :
-                                      SYNCH_EV_READERLOCK_RETURNING);
+    PostSynchEvent(this, waitp->how == kExclusive
+                             ? SYNCH_EV_LOCK_RETURNING
+                             : SYNCH_EV_READERLOCK_RETURNING);
   }
 }
 
@@ -2085,28 +2086,28 @@ void Mutex::LockSlowLoop(SynchWaitParams *waitp, int flags) {
 // which holds the lock but is not runnable because its condition is false
 // or it is in the process of blocking on a condition variable; it must requeue
 // itself on the mutex/condvar to wait for its condition to become true.
-ABSL_ATTRIBUTE_NOINLINE void Mutex::UnlockSlow(SynchWaitParams *waitp) {
+ABSL_ATTRIBUTE_NOINLINE void Mutex::UnlockSlow(SynchWaitParams* waitp) {
   SchedulingGuard::ScopedDisable disable_rescheduling;
   intptr_t v = mu_.load(std::memory_order_relaxed);
   this->AssertReaderHeld();
   CheckForMutexCorruption(v, "Unlock");
   if ((v & kMuEvent) != 0) {
-    PostSynchEvent(this,
-                (v & kMuWriter) != 0? SYNCH_EV_UNLOCK: SYNCH_EV_READERUNLOCK);
+    PostSynchEvent(
+        this, (v & kMuWriter) != 0 ? SYNCH_EV_UNLOCK : SYNCH_EV_READERUNLOCK);
   }
   int c = 0;
   // the waiter under consideration to wake, or zero
-  PerThreadSynch *w = nullptr;
+  PerThreadSynch* w = nullptr;
   // the predecessor to w or zero
-  PerThreadSynch *pw = nullptr;
+  PerThreadSynch* pw = nullptr;
   // head of the list searched previously, or zero
-  PerThreadSynch *old_h = nullptr;
+  PerThreadSynch* old_h = nullptr;
   // a condition that's known to be false.
-  const Condition *known_false = nullptr;
-  PerThreadSynch *wake_list = kPerThreadSynchNull;   // list of threads to wake
-  intptr_t wr_wait = 0;        // set to kMuWrWait if we wake a reader and a
-                               // later writer could have acquired the lock
-                               // (starvation avoidance)
+  const Condition* known_false = nullptr;
+  PerThreadSynch* wake_list = kPerThreadSynchNull;  // list of threads to wake
+  intptr_t wr_wait = 0;  // set to kMuWrWait if we wake a reader and a
+                         // later writer could have acquired the lock
+                         // (starvation avoidance)
   ABSL_RAW_CHECK(waitp == nullptr || waitp->thread->waitp == nullptr ||
                      waitp->thread->suppress_fatal_errors,
                  "detected illegal recursion into Mutex code");
@@ -2126,8 +2127,7 @@ ABSL_ATTRIBUTE_NOINLINE void Mutex::UnlockSlow(SynchWaitParams *waitp) {
     } else if ((v & (kMuReader | kMuWait)) == kMuReader && waitp == nullptr) {
       // fast reader release (reader with no waiters)
       intptr_t clear = ExactlyOneReader(v) ? kMuReader | kMuOne : kMuOne;
-      if (mu_.compare_exchange_strong(v, v - clear,
-                                      std::memory_order_release,
+      if (mu_.compare_exchange_strong(v, v - clear, std::memory_order_release,
                                       std::memory_order_relaxed)) {
         return;
       }
@@ -2135,16 +2135,16 @@ ABSL_ATTRIBUTE_NOINLINE void Mutex::UnlockSlow(SynchWaitParams *waitp) {
                mu_.compare_exchange_strong(v, v | kMuSpin,
                                            std::memory_order_acquire,
                                            std::memory_order_relaxed)) {
-      if ((v & kMuWait) == 0) {       // no one to wake
+      if ((v & kMuWait) == 0) {  // no one to wake
         intptr_t nv;
         bool do_enqueue = true;  // always Enqueue() the first time
         ABSL_RAW_CHECK(waitp != nullptr,
                        "UnlockSlow is confused");  // about to sleep
-        do {    // must loop to release spinlock as reader count may change
+        do {  // must loop to release spinlock as reader count may change
           v = mu_.load(std::memory_order_relaxed);
           // decrement reader count if there are readers
-          intptr_t new_readers = (v >= kMuOne)?  v - kMuOne : v;
-          PerThreadSynch *new_h = nullptr;
+          intptr_t new_readers = (v >= kMuOne) ? v - kMuOne : v;
+          PerThreadSynch* new_h = nullptr;
           if (do_enqueue) {
             // If we are enqueuing on a CondVar (waitp->cv_word != nullptr) then
             // we must not retry here.  The initial attempt will always have
@@ -2168,21 +2168,20 @@ ABSL_ATTRIBUTE_NOINLINE void Mutex::UnlockSlow(SynchWaitParams *waitp) {
           }
           // release spinlock & our lock; retry if reader-count changed
           // (writer count cannot change since we hold lock)
-        } while (!mu_.compare_exchange_weak(v, nv,
-                                            std::memory_order_release,
+        } while (!mu_.compare_exchange_weak(v, nv, std::memory_order_release,
                                             std::memory_order_relaxed));
         break;
       }
 
       // There are waiters.
       // Set h to the head of the circular waiter list.
-      PerThreadSynch *h = GetPerThreadSynch(v);
+      PerThreadSynch* h = GetPerThreadSynch(v);
       if ((v & kMuReader) != 0 && (h->readers & kMuHigh) > kMuOne) {
         // a reader but not the last
-        h->readers -= kMuOne;  // release our lock
-        intptr_t nv = v;       // normally just release spinlock
+        h->readers -= kMuOne;    // release our lock
+        intptr_t nv = v;         // normally just release spinlock
         if (waitp != nullptr) {  // but waitp!=nullptr => must queue ourselves
-          PerThreadSynch *new_h = Enqueue(h, waitp, v, kMuIsCond);
+          PerThreadSynch* new_h = Enqueue(h, waitp, v, kMuIsCond);
           ABSL_RAW_CHECK(new_h != nullptr,
                          "waiters disappeared during Enqueue()!");
           nv &= kMuLow;
@@ -2200,8 +2199,8 @@ ABSL_ATTRIBUTE_NOINLINE void Mutex::UnlockSlow(SynchWaitParams *waitp) {
 
       // The lock is becoming free, and there's a waiter
       if (old_h != nullptr &&
-          !old_h->may_skip) {                  // we used old_h as a terminator
-        old_h->may_skip = true;                // allow old_h to skip once more
+          !old_h->may_skip) {    // we used old_h as a terminator
+        old_h->may_skip = true;  // allow old_h to skip once more
         ABSL_RAW_CHECK(old_h->skip == nullptr, "illegal skip from head");
         if (h != old_h && MuEquivalentWaiter(old_h, old_h->next)) {
           old_h->skip = old_h->next;  // old_h not head & can skip to successor
@@ -2210,7 +2209,7 @@ ABSL_ATTRIBUTE_NOINLINE void Mutex::UnlockSlow(SynchWaitParams *waitp) {
       if (h->next->waitp->how == kExclusive &&
           Condition::GuaranteedEqual(h->next->waitp->cond, nullptr)) {
         // easy case: writer with no condition; no need to search
-        pw = h;                       // wake w, the successor of h (=pw)
+        pw = h;  // wake w, the successor of h (=pw)
         w = h->next;
         w->wake = true;
         // We are waking up a writer.  This writer may be racing against
@@ -2233,13 +2232,13 @@ ABSL_ATTRIBUTE_NOINLINE void Mutex::UnlockSlow(SynchWaitParams *waitp) {
         // waiter has a condition or is a reader.  We avoid searching over
         // waiters we've searched on previous iterations by starting at
         // old_h if it's set.  If old_h==h, there's no one to wakeup at all.
-        if (old_h == h) {      // we've searched before, and nothing's new
-                               // so there's no one to wake.
-          intptr_t nv = (v & ~(kMuReader|kMuWriter|kMuWrWait));
+        if (old_h == h) {  // we've searched before, and nothing's new
+                           // so there's no one to wake.
+          intptr_t nv = (v & ~(kMuReader | kMuWriter | kMuWrWait));
           h->readers = 0;
-          h->maybe_unlocking = false;   // finished unlocking
-          if (waitp != nullptr) {       // we must queue ourselves and sleep
-            PerThreadSynch *new_h = Enqueue(h, waitp, v, kMuIsCond);
+          h->maybe_unlocking = false;  // finished unlocking
+          if (waitp != nullptr) {      // we must queue ourselves and sleep
+            PerThreadSynch* new_h = Enqueue(h, waitp, v, kMuIsCond);
             nv &= kMuLow;
             if (new_h != nullptr) {
               nv |= kMuWait | reinterpret_cast<intptr_t>(new_h);
@@ -2253,12 +2252,12 @@ ABSL_ATTRIBUTE_NOINLINE void Mutex::UnlockSlow(SynchWaitParams *waitp) {
         }
 
         // set up to walk the list
-        PerThreadSynch *w_walk;   // current waiter during list walk
-        PerThreadSynch *pw_walk;  // previous waiter during list walk
+        PerThreadSynch* w_walk;   // current waiter during list walk
+        PerThreadSynch* pw_walk;  // previous waiter during list walk
         if (old_h != nullptr) {  // we've searched up to old_h before
           pw_walk = old_h;
           w_walk = old_h->next;
-        } else {            // no prior search, start at beginning
+        } else {  // no prior search, start at beginning
           pw_walk =
               nullptr;  // h->next's predecessor may change; don't record it
           w_walk = h->next;
@@ -2284,7 +2283,7 @@ ABSL_ATTRIBUTE_NOINLINE void Mutex::UnlockSlow(SynchWaitParams *waitp) {
         // to walk the path from w_walk to h inclusive. (TryRemove() can remove
         // a waiter anywhere, but it acquires both the spinlock and the Mutex)
 
-        old_h = h;        // remember we searched to here
+        old_h = h;  // remember we searched to here
 
         // Walk the path upto and including h looking for waiters we can wake.
         while (pw_walk != h) {
@@ -2296,24 +2295,24 @@ ABSL_ATTRIBUTE_NOINLINE void Mutex::UnlockSlow(SynchWaitParams *waitp) {
                //  is in fact true
                EvalConditionIgnored(this, w_walk->waitp->cond))) {
             if (w == nullptr) {
-              w_walk->wake = true;    // can wake this waiter
+              w_walk->wake = true;  // can wake this waiter
               w = w_walk;
               pw = pw_walk;
               if (w_walk->waitp->how == kExclusive) {
                 wr_wait = kMuWrWait;
-                break;                // bail if waking this writer
+                break;  // bail if waking this writer
               }
             } else if (w_walk->waitp->how == kShared) {  // wake if a reader
               w_walk->wake = true;
-            } else {   // writer with true condition
+            } else {  // writer with true condition
               wr_wait = kMuWrWait;
             }
-          } else {                  // can't wake; condition false
+          } else {                              // can't wake; condition false
             known_false = w_walk->waitp->cond;  // remember last false condition
           }
-          if (w_walk->wake) {   // we're waking reader w_walk
-            pw_walk = w_walk;   // don't skip similar waiters
-          } else {              // not waking; skip as much as possible
+          if (w_walk->wake) {  // we're waking reader w_walk
+            pw_walk = w_walk;  // don't skip similar waiters
+          } else {             // not waking; skip as much as possible
             pw_walk = Skip(w_walk);
           }
           // If pw_walk == h, then load of pw_walk->next can race with
@@ -2340,8 +2339,8 @@ ABSL_ATTRIBUTE_NOINLINE void Mutex::UnlockSlow(SynchWaitParams *waitp) {
       h = DequeueAllWakeable(h, pw, &wake_list);
 
       intptr_t nv = (v & kMuEvent) | kMuDesig;
-                                             // assume no waiters left,
-                                             // set kMuDesig for INV1a
+      // assume no waiters left,
+      // set kMuDesig for INV1a
 
       if (waitp != nullptr) {  // we must queue ourselves and sleep
         h = Enqueue(h, waitp, v, kMuIsCond);
@@ -2354,7 +2353,7 @@ ABSL_ATTRIBUTE_NOINLINE void Mutex::UnlockSlow(SynchWaitParams *waitp) {
 
       if (h != nullptr) {  // there are waiters left
         h->readers = 0;
-        h->maybe_unlocking = false;     // finished unlocking
+        h->maybe_unlocking = false;  // finished unlocking
         nv |= wr_wait | kMuWait | reinterpret_cast<intptr_t>(h);
       }
 
@@ -2365,12 +2364,12 @@ ABSL_ATTRIBUTE_NOINLINE void Mutex::UnlockSlow(SynchWaitParams *waitp) {
     }
     // aggressive here; no one can proceed till we do
     c = synchronization_internal::MutexDelay(c, AGGRESSIVE);
-  }                            // end of for(;;)-loop
+  }  // end of for(;;)-loop
 
   if (wake_list != kPerThreadSynchNull) {
     int64_t total_wait_cycles = 0;
     int64_t max_wait_cycles = 0;
-    int64_t now = base_internal::CycleClock::Now();
+    int64_t now = CycleClock::Now();
     do {
       // Profile lock contention events only if the waiter was trying to acquire
       // the lock, not waiting on a condition variable or Condition.
@@ -2382,7 +2381,7 @@ ABSL_ATTRIBUTE_NOINLINE void Mutex::UnlockSlow(SynchWaitParams *waitp) {
         wake_list->waitp->contention_start_cycles = now;
         wake_list->waitp->should_submit_contention_data = true;
       }
-      wake_list = Wakeup(wake_list);              // wake waiters
+      wake_list = Wakeup(wake_list);  // wake waiters
     } while (wake_list != kPerThreadSynchNull);
     if (total_wait_cycles > 0) {
       mutex_tracer("slow release", this, total_wait_cycles);
@@ -2410,7 +2409,7 @@ void Mutex::Trans(MuHow how) {
 // condition variable.  If this mutex is free, we simply wake the thread.
 // It will later acquire the mutex with high probability.  Otherwise, we
 // enqueue thread w on this mutex.
-void Mutex::Fer(PerThreadSynch *w) {
+void Mutex::Fer(PerThreadSynch* w) {
   SchedulingGuard::ScopedDisable disable_rescheduling;
   int c = 0;
   ABSL_RAW_CHECK(w->waitp->cond == nullptr,
@@ -2435,9 +2434,9 @@ void Mutex::Fer(PerThreadSynch *w) {
       IncrementSynchSem(this, w);
       return;
     } else {
-      if ((v & (kMuSpin|kMuWait)) == 0) {       // no waiters
+      if ((v & (kMuSpin | kMuWait)) == 0) {  // no waiters
         // This thread tries to become the one and only waiter.
-        PerThreadSynch *new_h = Enqueue(nullptr, w->waitp, v, kMuIsCond);
+        PerThreadSynch* new_h = Enqueue(nullptr, w->waitp, v, kMuIsCond);
         ABSL_RAW_CHECK(new_h != nullptr,
                        "Enqueue failed");  // we must queue ourselves
         if (mu_.compare_exchange_strong(
@@ -2447,8 +2446,8 @@ void Mutex::Fer(PerThreadSynch *w) {
         }
       } else if ((v & kMuSpin) == 0 &&
                  mu_.compare_exchange_strong(v, v | kMuSpin | kMuWait)) {
-        PerThreadSynch *h = GetPerThreadSynch(v);
-        PerThreadSynch *new_h = Enqueue(h, w->waitp, v, kMuIsCond);
+        PerThreadSynch* h = GetPerThreadSynch(v);
+        PerThreadSynch* new_h = Enqueue(h, w->waitp, v, kMuIsCond);
         ABSL_RAW_CHECK(new_h != nullptr,
                        "Enqueue failed");  // we must queue ourselves
         do {
@@ -2467,19 +2466,18 @@ void Mutex::Fer(PerThreadSynch *w) {
 
 void Mutex::AssertHeld() const {
   if ((mu_.load(std::memory_order_relaxed) & kMuWriter) == 0) {
-    SynchEvent *e = GetSynchEvent(this);
+    SynchEvent* e = GetSynchEvent(this);
     ABSL_RAW_LOG(FATAL, "thread should hold write lock on Mutex %p %s",
-                 static_cast<const void *>(this),
-                 (e == nullptr ? "" : e->name));
+                 static_cast<const void*>(this), (e == nullptr ? "" : e->name));
   }
 }
 
 void Mutex::AssertReaderHeld() const {
   if ((mu_.load(std::memory_order_relaxed) & (kMuReader | kMuWriter)) == 0) {
-    SynchEvent *e = GetSynchEvent(this);
-    ABSL_RAW_LOG(
-        FATAL, "thread should hold at least a read lock on Mutex %p %s",
-        static_cast<const void *>(this), (e == nullptr ? "" : e->name));
+    SynchEvent* e = GetSynchEvent(this);
+    ABSL_RAW_LOG(FATAL,
+                 "thread should hold at least a read lock on Mutex %p %s",
+                 static_cast<const void*>(this), (e == nullptr ? "" : e->name));
   }
 }
 
@@ -2490,13 +2488,17 @@ static const intptr_t kCvEvent = 0x0002L;  // record events
 static const intptr_t kCvLow = 0x0003L;  // low order bits of CV
 
 // Hack to make constant values available to gdb pretty printer
-enum { kGdbCvSpin = kCvSpin, kGdbCvEvent = kCvEvent, kGdbCvLow = kCvLow, };
+enum {
+  kGdbCvSpin = kCvSpin,
+  kGdbCvEvent = kCvEvent,
+  kGdbCvLow = kCvLow,
+};
 
 static_assert(PerThreadSynch::kAlignment > kCvLow,
               "PerThreadSynch::kAlignment must be greater than kCvLow");
 
-void CondVar::EnableDebugLog(const char *name) {
-  SynchEvent *e = EnsureSynchEvent(&this->cv_, name, kCvEvent, kCvSpin);
+void CondVar::EnableDebugLog(const char* name) {
+  SynchEvent* e = EnsureSynchEvent(&this->cv_, name, kCvEvent, kCvSpin);
   e->log = true;
   UnrefSynchEvent(e);
 }
@@ -2507,25 +2509,23 @@ CondVar::~CondVar() {
   }
 }
 
-
 // Remove thread s from the list of waiters on this condition variable.
-void CondVar::Remove(PerThreadSynch *s) {
+void CondVar::Remove(PerThreadSynch* s) {
   SchedulingGuard::ScopedDisable disable_rescheduling;
   intptr_t v;
   int c = 0;
   for (v = cv_.load(std::memory_order_relaxed);;
        v = cv_.load(std::memory_order_relaxed)) {
     if ((v & kCvSpin) == 0 &&  // attempt to acquire spinlock
-        cv_.compare_exchange_strong(v, v | kCvSpin,
-                                    std::memory_order_acquire,
+        cv_.compare_exchange_strong(v, v | kCvSpin, std::memory_order_acquire,
                                     std::memory_order_relaxed)) {
-      PerThreadSynch *h = reinterpret_cast<PerThreadSynch *>(v & ~kCvLow);
+      PerThreadSynch* h = reinterpret_cast<PerThreadSynch*>(v & ~kCvLow);
       if (h != nullptr) {
-        PerThreadSynch *w = h;
+        PerThreadSynch* w = h;
         while (w->next != s && w->next != h) {  // search for thread
           w = w->next;
         }
-        if (w->next == s) {           // found thread; remove it
+        if (w->next == s) {  // found thread; remove it
           w->next = s->next;
           if (h == s) {
             h = (w == s) ? nullptr : w;
@@ -2534,7 +2534,7 @@ void CondVar::Remove(PerThreadSynch *s) {
           s->state.store(PerThreadSynch::kAvailable, std::memory_order_release);
         }
       }
-                                      // release spinlock
+      // release spinlock
       cv_.store((v & kCvEvent) | reinterpret_cast<intptr_t>(h),
                 std::memory_order_release);
       return;
@@ -2557,14 +2557,14 @@ void CondVar::Remove(PerThreadSynch *s) {
 // variable queue just before the mutex is to be unlocked, and (most
 // importantly) after any call to an external routine that might re-enter the
 // mutex code.
-static void CondVarEnqueue(SynchWaitParams *waitp) {
+static void CondVarEnqueue(SynchWaitParams* waitp) {
   // This thread might be transferred to the Mutex queue by Fer() when
   // we are woken.  To make sure that is what happens, Enqueue() doesn't
   // call CondVarEnqueue() again but instead uses its normal code.  We
   // must do this before we queue ourselves so that cv_word will be null
   // when seen by the dequeuer, who may wish immediately to requeue
   // this thread on another queue.
-  std::atomic<intptr_t> *cv_word = waitp->cv_word;
+  std::atomic<intptr_t>* cv_word = waitp->cv_word;
   waitp->cv_word = nullptr;
 
   intptr_t v = cv_word->load(std::memory_order_relaxed);
@@ -2577,8 +2577,8 @@ static void CondVarEnqueue(SynchWaitParams *waitp) {
     v = cv_word->load(std::memory_order_relaxed);
   }
   ABSL_RAW_CHECK(waitp->thread->waitp == nullptr, "waiting when shouldn't be");
-  waitp->thread->waitp = waitp;      // prepare ourselves for waiting
-  PerThreadSynch *h = reinterpret_cast<PerThreadSynch *>(v & ~kCvLow);
+  waitp->thread->waitp = waitp;  // prepare ourselves for waiting
+  PerThreadSynch* h = reinterpret_cast<PerThreadSynch*>(v & ~kCvLow);
   if (h == nullptr) {  // add this thread to waiter list
     waitp->thread->next = waitp->thread;
   } else {
@@ -2591,8 +2591,8 @@ static void CondVarEnqueue(SynchWaitParams *waitp) {
                  std::memory_order_release);
 }
 
-bool CondVar::WaitCommon(Mutex *mutex, KernelTimeout t) {
-  bool rc = false;          // return value; true iff we timed-out
+bool CondVar::WaitCommon(Mutex* mutex, KernelTimeout t) {
+  bool rc = false;  // return value; true iff we timed-out
 
   intptr_t mutex_v = mutex->mu_.load(std::memory_order_relaxed);
   Mutex::MuHow mutex_how = ((mutex_v & kMuWriter) != 0) ? kExclusive : kShared;
@@ -2659,27 +2659,25 @@ bool CondVar::WaitCommon(Mutex *mutex, KernelTimeout t) {
   return rc;
 }
 
-bool CondVar::WaitWithTimeout(Mutex *mu, absl::Duration timeout) {
-  return WaitWithDeadline(mu, DeadlineFromTimeout(timeout));
+bool CondVar::WaitWithTimeout(Mutex* mu, absl::Duration timeout) {
+  return WaitCommon(mu, KernelTimeout(timeout));
 }
 
-bool CondVar::WaitWithDeadline(Mutex *mu, absl::Time deadline) {
+bool CondVar::WaitWithDeadline(Mutex* mu, absl::Time deadline) {
   return WaitCommon(mu, KernelTimeout(deadline));
 }
 
-void CondVar::Wait(Mutex *mu) {
-  WaitCommon(mu, KernelTimeout::Never());
-}
+void CondVar::Wait(Mutex* mu) { WaitCommon(mu, KernelTimeout::Never()); }
 
 // Wake thread w
 // If it was a timed wait, w will be waiting on w->cv
 // Otherwise, if it was not a Mutex mutex, w will be waiting on w->sem
 // Otherwise, w is transferred to the Mutex mutex via Mutex::Fer().
-void CondVar::Wakeup(PerThreadSynch *w) {
+void CondVar::Wakeup(PerThreadSynch* w) {
   if (w->waitp->timeout.has_timeout() || w->waitp->cvmu == nullptr) {
     // The waiting thread only needs to observe "w->state == kAvailable" to be
     // released, we must cache "cvmu" before clearing "next".
-    Mutex *mu = w->waitp->cvmu;
+    Mutex* mu = w->waitp->cvmu;
     w->next = nullptr;
     w->state.store(PerThreadSynch::kAvailable, std::memory_order_release);
     Mutex::IncrementSynchSem(mu, w);
@@ -2696,11 +2694,10 @@ void CondVar::Signal() {
   for (v = cv_.load(std::memory_order_relaxed); v != 0;
        v = cv_.load(std::memory_order_relaxed)) {
     if ((v & kCvSpin) == 0 &&  // attempt to acquire spinlock
-        cv_.compare_exchange_strong(v, v | kCvSpin,
-                                    std::memory_order_acquire,
+        cv_.compare_exchange_strong(v, v | kCvSpin, std::memory_order_acquire,
                                     std::memory_order_relaxed)) {
-      PerThreadSynch *h = reinterpret_cast<PerThreadSynch *>(v & ~kCvLow);
-      PerThreadSynch *w = nullptr;
+      PerThreadSynch* h = reinterpret_cast<PerThreadSynch*>(v & ~kCvLow);
+      PerThreadSynch* w = nullptr;
       if (h != nullptr) {  // remove first waiter
         w = h->next;
         if (w == h) {
@@ -2709,11 +2706,11 @@ void CondVar::Signal() {
           h->next = w->next;
         }
       }
-                                      // release spinlock
+      // release spinlock
       cv_.store((v & kCvEvent) | reinterpret_cast<intptr_t>(h),
                 std::memory_order_release);
       if (w != nullptr) {
-        CondVar::Wakeup(w);                // wake waiter, if there was one
+        CondVar::Wakeup(w);  // wake waiter, if there was one
         cond_var_tracer("Signal wakeup", this);
       }
       if ((v & kCvEvent) != 0) {
@@ -2728,7 +2725,7 @@ void CondVar::Signal() {
   ABSL_TSAN_MUTEX_POST_SIGNAL(nullptr, 0);
 }
 
-void CondVar::SignalAll () {
+void CondVar::SignalAll() {
   ABSL_TSAN_MUTEX_PRE_SIGNAL(nullptr, 0);
   intptr_t v;
   int c = 0;
@@ -2742,11 +2739,11 @@ void CondVar::SignalAll () {
     if ((v & kCvSpin) == 0 &&
         cv_.compare_exchange_strong(v, v & kCvEvent, std::memory_order_acquire,
                                     std::memory_order_relaxed)) {
-      PerThreadSynch *h = reinterpret_cast<PerThreadSynch *>(v & ~kCvLow);
+      PerThreadSynch* h = reinterpret_cast<PerThreadSynch*>(v & ~kCvLow);
       if (h != nullptr) {
-        PerThreadSynch *w;
-        PerThreadSynch *n = h->next;
-        do {                          // for every thread, wake it up
+        PerThreadSynch* w;
+        PerThreadSynch* n = h->next;
+        do {  // for every thread, wake it up
           w = n;
           n = n->next;
           CondVar::Wakeup(w);
@@ -2774,42 +2771,41 @@ void ReleasableMutexLock::Release() {
 }
 
 #ifdef ABSL_HAVE_THREAD_SANITIZER
-extern "C" void __tsan_read1(void *addr);
+extern "C" void __tsan_read1(void* addr);
 #else
 #define __tsan_read1(addr)  // do nothing if TSan not enabled
 #endif
 
 // A function that just returns its argument, dereferenced
-static bool Dereference(void *arg) {
+static bool Dereference(void* arg) {
   // ThreadSanitizer does not instrument this file for memory accesses.
   // This function dereferences a user variable that can participate
   // in a data race, so we need to manually tell TSan about this memory access.
   __tsan_read1(arg);
-  return *(static_cast<bool *>(arg));
+  return *(static_cast<bool*>(arg));
 }
 
 ABSL_CONST_INIT const Condition Condition::kTrue;
 
-Condition::Condition(bool (*func)(void *), void *arg)
-    : eval_(&CallVoidPtrFunction),
-      arg_(arg) {
+Condition::Condition(bool (*func)(void*), void* arg)
+    : eval_(&CallVoidPtrFunction), arg_(arg) {
   static_assert(sizeof(&func) <= sizeof(callback_),
                 "An overlarge function pointer passed to Condition.");
   StoreCallback(func);
 }
 
-bool Condition::CallVoidPtrFunction(const Condition *c) {
-  using FunctionPointer = bool (*)(void *);
+bool Condition::CallVoidPtrFunction(const Condition* c) {
+  using FunctionPointer = bool (*)(void*);
   FunctionPointer function_pointer;
   std::memcpy(&function_pointer, c->callback_, sizeof(function_pointer));
   return (*function_pointer)(c->arg_);
 }
 
-Condition::Condition(const bool *cond)
+Condition::Condition(const bool* cond)
     : eval_(CallVoidPtrFunction),
       // const_cast is safe since Dereference does not modify arg
-      arg_(const_cast<bool *>(cond)) {
-  using FunctionPointer = bool (*)(void *);
+      arg_(const_cast<bool*>(cond)) {
+  using FunctionPointer = bool (*)(void*);
   const FunctionPointer dereference = Dereference;
   StoreCallback(dereference);
 }
@@ -2819,7 +2815,7 @@ bool Condition::Eval() const {
   return (this->eval_ == nullptr) || (*this->eval_)(this);
 }
 
-bool Condition::GuaranteedEqual(const Condition *a, const Condition *b) {
+bool Condition::GuaranteedEqual(const Condition* a, const Condition* b) {
   // kTrue logic.
   if (a == nullptr || a->eval_ == nullptr) {
     return b == nullptr || b->eval_ == nullptr;
diff --git a/absl/synchronization/mutex.h b/absl/synchronization/mutex.h
index f793cc0e..645c26d9 100644
--- a/absl/synchronization/mutex.h
+++ b/absl/synchronization/mutex.h
@@ -92,26 +92,42 @@ struct SynchWaitParams;
 //
 // A `Mutex` has two basic operations: `Mutex::Lock()` and `Mutex::Unlock()`.
 // The `Lock()` operation *acquires* a `Mutex` (in a state known as an
-// *exclusive* -- or write -- lock), while the `Unlock()` operation *releases* a
+// *exclusive* -- or *write* -- lock), and the `Unlock()` operation *releases* a
 // Mutex. During the span of time between the Lock() and Unlock() operations,
-// a mutex is said to be *held*. By design all mutexes support exclusive/write
+// a mutex is said to be *held*. By design, all mutexes support exclusive/write
 // locks, as this is the most common way to use a mutex.
 //
+// Mutex operations are only allowed under certain conditions; otherwise an
+// operation is "invalid", and disallowed by the API. The conditions concern
+// both the current state of the mutex and the identity of the threads that
+// are performing the operations.
+//
 // The `Mutex` state machine for basic lock/unlock operations is quite simple:
 //
-// |                | Lock()     | Unlock() |
-// |----------------+------------+----------|
-// | Free           | Exclusive  | invalid  |
-// | Exclusive      | blocks     | Free     |
+// |                | Lock()                 | Unlock() |
+// |----------------+------------------------+----------|
+// | Free           | Exclusive              | invalid  |
+// | Exclusive      | blocks, then exclusive | Free     |
+//
+// The full conditions are as follows.
+//
+// * Calls to `Unlock()` require that the mutex be held, and must be made in the
+//   same thread that performed the corresponding `Lock()` operation which
+//   acquired the mutex; otherwise the call is invalid.
+//
+// * The mutex being non-reentrant (or non-recursive) means that a call to
+//   `Lock()` or `TryLock()` must not be made in a thread that already holds the
+//   mutex; such a call is invalid.
 //
-// Attempts to `Unlock()` must originate from the thread that performed the
-// corresponding `Lock()` operation.
+// * In other words, the state of being "held" has both a temporal component
+//   (from `Lock()` until `Unlock()`) as well as a thread identity component:
+//   the mutex is held *by a particular thread*.
 //
-// An "invalid" operation is disallowed by the API. The `Mutex` implementation
-// is allowed to do anything on an invalid call, including but not limited to
+// An "invalid" operation has undefined behavior. The `Mutex` implementation
+// is allowed to do anything on an invalid call, including, but not limited to,
 // crashing with a useful error message, silently succeeding, or corrupting
-// data structures. In debug mode, the implementation attempts to crash with a
-// useful error message.
+// data structures. In debug mode, the implementation may crash with a useful
+// error message.
 //
 // `Mutex` is not guaranteed to be "fair" in prioritizing waiting threads; it
 // is, however, approximately fair over long periods, and starvation-free for
@@ -125,8 +141,9 @@ struct SynchWaitParams;
 // issues that could potentially result in race conditions and deadlocks.
 //
 // For more information about the lock annotations, please see
-// [Thread Safety Analysis](http://clang.llvm.org/docs/ThreadSafetyAnalysis.html)
-// in the Clang documentation.
+// [Thread Safety
+// Analysis](http://clang.llvm.org/docs/ThreadSafetyAnalysis.html) in the Clang
+// documentation.
 //
 // See also `MutexLock`, below, for scoped `Mutex` acquisition.
 
@@ -257,7 +274,7 @@ class ABSL_LOCKABLE Mutex {
   // Aliases for `Mutex::Lock()`, `Mutex::Unlock()`, and `Mutex::TryLock()`.
   //
   // These methods may be used (along with the complementary `Reader*()`
-  // methods) to distingish simple exclusive `Mutex` usage (`Lock()`,
+  // methods) to distinguish simple exclusive `Mutex` usage (`Lock()`,
   // etc.) from reader/writer lock usage.
   void WriterLock() ABSL_EXCLUSIVE_LOCK_FUNCTION() { this->Lock(); }
 
@@ -307,7 +324,7 @@ class ABSL_LOCKABLE Mutex {
   // `true`, `Await()` *may* skip the release/re-acquire step.
   //
   // `Await()` requires that this thread holds this `Mutex` in some mode.
-  void Await(const Condition &cond);
+  void Await(const Condition& cond);
 
   // Mutex::LockWhen()
   // Mutex::ReaderLockWhen()
@@ -317,11 +334,11 @@ class ABSL_LOCKABLE Mutex {
   // be acquired, then atomically acquires this `Mutex`. `LockWhen()` is
   // logically equivalent to `*Lock(); Await();` though they may have different
   // performance characteristics.
-  void LockWhen(const Condition &cond) ABSL_EXCLUSIVE_LOCK_FUNCTION();
+  void LockWhen(const Condition& cond) ABSL_EXCLUSIVE_LOCK_FUNCTION();
 
-  void ReaderLockWhen(const Condition &cond) ABSL_SHARED_LOCK_FUNCTION();
+  void ReaderLockWhen(const Condition& cond) ABSL_SHARED_LOCK_FUNCTION();
 
-  void WriterLockWhen(const Condition &cond) ABSL_EXCLUSIVE_LOCK_FUNCTION() {
+  void WriterLockWhen(const Condition& cond) ABSL_EXCLUSIVE_LOCK_FUNCTION() {
     this->LockWhen(cond);
   }
 
@@ -346,9 +363,9 @@ class ABSL_LOCKABLE Mutex {
   // Negative timeouts are equivalent to a zero timeout.
   //
   // This method requires that this thread holds this `Mutex` in some mode.
-  bool AwaitWithTimeout(const Condition &cond, absl::Duration timeout);
+  bool AwaitWithTimeout(const Condition& cond, absl::Duration timeout);
 
-  bool AwaitWithDeadline(const Condition &cond, absl::Time deadline);
+  bool AwaitWithDeadline(const Condition& cond, absl::Time deadline);
 
   // Mutex::LockWhenWithTimeout()
   // Mutex::ReaderLockWhenWithTimeout()
@@ -361,11 +378,11 @@ class ABSL_LOCKABLE Mutex {
   // `true` on return.
   //
   // Negative timeouts are equivalent to a zero timeout.
-  bool LockWhenWithTimeout(const Condition &cond, absl::Duration timeout)
+  bool LockWhenWithTimeout(const Condition& cond, absl::Duration timeout)
       ABSL_EXCLUSIVE_LOCK_FUNCTION();
-  bool ReaderLockWhenWithTimeout(const Condition &cond, absl::Duration timeout)
+  bool ReaderLockWhenWithTimeout(const Condition& cond, absl::Duration timeout)
       ABSL_SHARED_LOCK_FUNCTION();
-  bool WriterLockWhenWithTimeout(const Condition &cond, absl::Duration timeout)
+  bool WriterLockWhenWithTimeout(const Condition& cond, absl::Duration timeout)
       ABSL_EXCLUSIVE_LOCK_FUNCTION() {
     return this->LockWhenWithTimeout(cond, timeout);
   }
@@ -381,11 +398,11 @@ class ABSL_LOCKABLE Mutex {
   // on return.
   //
   // Deadlines in the past are equivalent to an immediate deadline.
-  bool LockWhenWithDeadline(const Condition &cond, absl::Time deadline)
+  bool LockWhenWithDeadline(const Condition& cond, absl::Time deadline)
       ABSL_EXCLUSIVE_LOCK_FUNCTION();
-  bool ReaderLockWhenWithDeadline(const Condition &cond, absl::Time deadline)
+  bool ReaderLockWhenWithDeadline(const Condition& cond, absl::Time deadline)
       ABSL_SHARED_LOCK_FUNCTION();
-  bool WriterLockWhenWithDeadline(const Condition &cond, absl::Time deadline)
+  bool WriterLockWhenWithDeadline(const Condition& cond, absl::Time deadline)
       ABSL_EXCLUSIVE_LOCK_FUNCTION() {
     return this->LockWhenWithDeadline(cond, deadline);
   }
@@ -407,7 +424,7 @@ class ABSL_LOCKABLE Mutex {
   // substantially reduce `Mutex` performance; it should be set only for
   // non-production runs.  Optimization options may also disable invariant
   // checks.
-  void EnableInvariantDebugging(void (*invariant)(void *), void *arg);
+  void EnableInvariantDebugging(void (*invariant)(void*), void* arg);
 
   // Mutex::EnableDebugLog()
   //
@@ -416,7 +433,7 @@ class ABSL_LOCKABLE Mutex {
   // call to `EnableInvariantDebugging()` or `EnableDebugLog()` has been made.
   //
   // Note: This method substantially reduces `Mutex` performance.
-  void EnableDebugLog(const char *name);
+  void EnableDebugLog(const char* name);
 
   // Deadlock detection
 
@@ -444,7 +461,7 @@ class ABSL_LOCKABLE Mutex {
 
   // A `MuHow` is a constant that indicates how a lock should be acquired.
   // Internal implementation detail.  Clients should ignore.
-  typedef const struct MuHowS *MuHow;
+  typedef const struct MuHowS* MuHow;
 
   // Mutex::InternalAttemptToUseMutexInFatalSignalHandler()
   //
@@ -466,37 +483,37 @@ class ABSL_LOCKABLE Mutex {
 
   // Post()/Wait() versus associated PerThreadSem; in class for required
   // friendship with PerThreadSem.
-  static void IncrementSynchSem(Mutex *mu, base_internal::PerThreadSynch *w);
-  static bool DecrementSynchSem(Mutex *mu, base_internal::PerThreadSynch *w,
+  static void IncrementSynchSem(Mutex* mu, base_internal::PerThreadSynch* w);
+  static bool DecrementSynchSem(Mutex* mu, base_internal::PerThreadSynch* w,
                                 synchronization_internal::KernelTimeout t);
 
   // slow path acquire
-  void LockSlowLoop(SynchWaitParams *waitp, int flags);
+  void LockSlowLoop(SynchWaitParams* waitp, int flags);
   // wrappers around LockSlowLoop()
-  bool LockSlowWithDeadline(MuHow how, const Condition *cond,
+  bool LockSlowWithDeadline(MuHow how, const Condition* cond,
                             synchronization_internal::KernelTimeout t,
                             int flags);
-  void LockSlow(MuHow how, const Condition *cond,
+  void LockSlow(MuHow how, const Condition* cond,
                 int flags) ABSL_ATTRIBUTE_COLD;
   // slow path release
-  void UnlockSlow(SynchWaitParams *waitp) ABSL_ATTRIBUTE_COLD;
+  void UnlockSlow(SynchWaitParams* waitp) ABSL_ATTRIBUTE_COLD;
   // Common code between Await() and AwaitWithTimeout/Deadline()
-  bool AwaitCommon(const Condition &cond,
+  bool AwaitCommon(const Condition& cond,
                    synchronization_internal::KernelTimeout t);
   // Attempt to remove thread s from queue.
-  void TryRemove(base_internal::PerThreadSynch *s);
+  void TryRemove(base_internal::PerThreadSynch* s);
   // Block a thread on mutex.
-  void Block(base_internal::PerThreadSynch *s);
+  void Block(base_internal::PerThreadSynch* s);
   // Wake a thread; return successor.
-  base_internal::PerThreadSynch *Wakeup(base_internal::PerThreadSynch *w);
+  base_internal::PerThreadSynch* Wakeup(base_internal::PerThreadSynch* w);
 
   friend class CondVar;   // for access to Trans()/Fer().
   void Trans(MuHow how);  // used for CondVar->Mutex transfer
   void Fer(
-      base_internal::PerThreadSynch *w);  // used for CondVar->Mutex transfer
+      base_internal::PerThreadSynch* w);  // used for CondVar->Mutex transfer
 
   // Catch the error of writing Mutex when intending MutexLock.
-  Mutex(const volatile Mutex * /*ignored*/) {}  // NOLINT(runtime/explicit)
+  explicit Mutex(const volatile Mutex* /*ignored*/) {}
 
   Mutex(const Mutex&) = delete;
   Mutex& operator=(const Mutex&) = delete;
@@ -531,28 +548,28 @@ class ABSL_SCOPED_LOCKABLE MutexLock {
   // Calls `mu->Lock()` and returns when that call returns. That is, `*mu` is
   // guaranteed to be locked when this object is constructed. Requires that
   // `mu` be dereferenceable.
-  explicit MutexLock(Mutex *mu) ABSL_EXCLUSIVE_LOCK_FUNCTION(mu) : mu_(mu) {
+  explicit MutexLock(Mutex* mu) ABSL_EXCLUSIVE_LOCK_FUNCTION(mu) : mu_(mu) {
     this->mu_->Lock();
   }
 
   // Like above, but calls `mu->LockWhen(cond)` instead. That is, in addition to
   // the above, the condition given by `cond` is also guaranteed to hold when
   // this object is constructed.
-  explicit MutexLock(Mutex *mu, const Condition &cond)
+  explicit MutexLock(Mutex* mu, const Condition& cond)
       ABSL_EXCLUSIVE_LOCK_FUNCTION(mu)
       : mu_(mu) {
     this->mu_->LockWhen(cond);
   }
 
-  MutexLock(const MutexLock &) = delete;  // NOLINT(runtime/mutex)
-  MutexLock(MutexLock&&) = delete;  // NOLINT(runtime/mutex)
+  MutexLock(const MutexLock&) = delete;  // NOLINT(runtime/mutex)
+  MutexLock(MutexLock&&) = delete;       // NOLINT(runtime/mutex)
   MutexLock& operator=(const MutexLock&) = delete;
   MutexLock& operator=(MutexLock&&) = delete;
 
   ~MutexLock() ABSL_UNLOCK_FUNCTION() { this->mu_->Unlock(); }
 
  private:
-  Mutex *const mu_;
+  Mutex* const mu_;
 };
 
 // ReaderMutexLock
@@ -561,11 +578,11 @@ class ABSL_SCOPED_LOCKABLE MutexLock {
 // releases a shared lock on a `Mutex` via RAII.
 class ABSL_SCOPED_LOCKABLE ReaderMutexLock {
  public:
-  explicit ReaderMutexLock(Mutex *mu) ABSL_SHARED_LOCK_FUNCTION(mu) : mu_(mu) {
+  explicit ReaderMutexLock(Mutex* mu) ABSL_SHARED_LOCK_FUNCTION(mu) : mu_(mu) {
     mu->ReaderLock();
   }
 
-  explicit ReaderMutexLock(Mutex *mu, const Condition &cond)
+  explicit ReaderMutexLock(Mutex* mu, const Condition& cond)
       ABSL_SHARED_LOCK_FUNCTION(mu)
       : mu_(mu) {
     mu->ReaderLockWhen(cond);
@@ -579,7 +596,7 @@ class ABSL_SCOPED_LOCKABLE ReaderMutexLock {
   ~ReaderMutexLock() ABSL_UNLOCK_FUNCTION() { this->mu_->ReaderUnlock(); }
 
  private:
-  Mutex *const mu_;
+  Mutex* const mu_;
 };
 
 // WriterMutexLock
@@ -588,12 +605,12 @@ class ABSL_SCOPED_LOCKABLE ReaderMutexLock {
 // releases a write (exclusive) lock on a `Mutex` via RAII.
 class ABSL_SCOPED_LOCKABLE WriterMutexLock {
  public:
-  explicit WriterMutexLock(Mutex *mu) ABSL_EXCLUSIVE_LOCK_FUNCTION(mu)
+  explicit WriterMutexLock(Mutex* mu) ABSL_EXCLUSIVE_LOCK_FUNCTION(mu)
       : mu_(mu) {
     mu->WriterLock();
   }
 
-  explicit WriterMutexLock(Mutex *mu, const Condition &cond)
+  explicit WriterMutexLock(Mutex* mu, const Condition& cond)
       ABSL_EXCLUSIVE_LOCK_FUNCTION(mu)
       : mu_(mu) {
     mu->WriterLockWhen(cond);
@@ -607,7 +624,7 @@ class ABSL_SCOPED_LOCKABLE WriterMutexLock {
   ~WriterMutexLock() ABSL_UNLOCK_FUNCTION() { this->mu_->WriterUnlock(); }
 
  private:
-  Mutex *const mu_;
+  Mutex* const mu_;
 };
 
 // -----------------------------------------------------------------------------
@@ -665,7 +682,7 @@ class ABSL_SCOPED_LOCKABLE WriterMutexLock {
 class Condition {
  public:
   // A Condition that returns the result of "(*func)(arg)"
-  Condition(bool (*func)(void *), void *arg);
+  Condition(bool (*func)(void*), void* arg);
 
   // Templated version for people who are averse to casts.
   //
@@ -676,8 +693,22 @@ class Condition {
   // Note: lambdas in this case must contain no bound variables.
   //
   // See class comment for performance advice.
-  template<typename T>
-  Condition(bool (*func)(T *), T *arg);
+  template <typename T>
+  Condition(bool (*func)(T*), T* arg);
+
+  // Same as above, but allows for cases where `arg` comes from a pointer that
+  // is convertible to the function parameter type `T*` but not an exact match.
+  //
+  // For example, the argument might be `X*` but the function takes `const X*`,
+  // or the argument might be `Derived*` while the function takes `Base*`, and
+  // so on for cases where the argument pointer can be implicitly converted.
+  //
+  // Implementation notes: This constructor overload is required in addition to
+  // the one above to allow deduction of `T` from `arg` for cases such as where
+  // a function template is passed as `func`. Also, the dummy `typename = void`
+  // template parameter exists just to work around a MSVC mangling bug.
+  template <typename T, typename = void>
+  Condition(bool (*func)(T*), typename absl::internal::identity<T>::type* arg);
 
   // Templated version for invoking a method that returns a `bool`.
   //
@@ -687,16 +718,16 @@ class Condition {
   // Implementation Note: `absl::internal::identity` is used to allow methods to
   // come from base classes. A simpler signature like
   // `Condition(T*, bool (T::*)())` does not suffice.
-  template<typename T>
-  Condition(T *object, bool (absl::internal::identity<T>::type::* method)());
+  template <typename T>
+  Condition(T* object, bool (absl::internal::identity<T>::type::*method)());
 
   // Same as above, for const members
-  template<typename T>
-  Condition(const T *object,
-            bool (absl::internal::identity<T>::type::* method)() const);
+  template <typename T>
+  Condition(const T* object,
+            bool (absl::internal::identity<T>::type::*method)() const);
 
   // A Condition that returns the value of `*cond`
-  explicit Condition(const bool *cond);
+  explicit Condition(const bool* cond);
 
   // Templated version for invoking a functor that returns a `bool`.
   // This approach accepts pointers to non-mutable lambdas, `std::function`,
@@ -723,12 +754,22 @@ class Condition {
   // Implementation note: The second template parameter ensures that this
   // constructor doesn't participate in overload resolution if T doesn't have
   // `bool operator() const`.
-  template <typename T, typename E = decltype(
-      static_cast<bool (T::*)() const>(&T::operator()))>
-  explicit Condition(const T *obj)
+  template <typename T, typename E = decltype(static_cast<bool (T::*)() const>(
+                            &T::operator()))>
+  explicit Condition(const T* obj)
       : Condition(obj, static_cast<bool (T::*)() const>(&T::operator())) {}
 
   // A Condition that always returns `true`.
+  // kTrue is only useful in a narrow set of circumstances, mostly when
+  // it's passed conditionally. For example:
+  //
+  //   mu.LockWhen(some_flag ? kTrue : SomeOtherCondition);
+  //
+  // Note: {LockWhen,Await}With{Deadline,Timeout} methods with kTrue condition
+  // don't return immediately when the timeout happens, they still block until
+  // the Mutex becomes available. The return value of these methods does
+  // not indicate if the timeout was reached; rather it indicates whether or
+  // not the condition is true.
   ABSL_CONST_INIT static const Condition kTrue;
 
   // Evaluates the condition.
@@ -741,7 +782,7 @@ class Condition {
   // Two `Condition` values are guaranteed equal if both their `func` and `arg`
   // components are the same. A null pointer is equivalent to a `true`
   // condition.
-  static bool GuaranteedEqual(const Condition *a, const Condition *b);
+  static bool GuaranteedEqual(const Condition* a, const Condition* b);
 
  private:
   // Sizing an allocation for a method pointer can be subtle. In the Itanium
@@ -769,12 +810,14 @@ class Condition {
   bool (*eval_)(const Condition*) = nullptr;
 
   // Either an argument for a function call or an object for a method call.
-  void *arg_ = nullptr;
+  void* arg_ = nullptr;
 
   // Various functions eval_ can point to:
   static bool CallVoidPtrFunction(const Condition*);
-  template <typename T> static bool CastAndCallFunction(const Condition* c);
-  template <typename T> static bool CastAndCallMethod(const Condition* c);
+  template <typename T>
+  static bool CastAndCallFunction(const Condition* c);
+  template <typename T>
+  static bool CastAndCallMethod(const Condition* c);
 
   // Helper methods for storing, validating, and reading callback arguments.
   template <typename T>
@@ -786,7 +829,7 @@ class Condition {
   }
 
   template <typename T>
-  inline void ReadCallback(T *callback) const {
+  inline void ReadCallback(T* callback) const {
     std::memcpy(callback, callback_, sizeof(*callback));
   }
 
@@ -843,7 +886,7 @@ class CondVar {
   // spurious wakeup), then reacquires the `Mutex` and returns.
   //
   // Requires and ensures that the current thread holds the `Mutex`.
-  void Wait(Mutex *mu);
+  void Wait(Mutex* mu);
 
   // CondVar::WaitWithTimeout()
   //
@@ -858,7 +901,7 @@ class CondVar {
   // to return `true` or `false`.
   //
   // Requires and ensures that the current thread holds the `Mutex`.
-  bool WaitWithTimeout(Mutex *mu, absl::Duration timeout);
+  bool WaitWithTimeout(Mutex* mu, absl::Duration timeout);
 
   // CondVar::WaitWithDeadline()
   //
@@ -875,7 +918,7 @@ class CondVar {
   // to return `true` or `false`.
   //
   // Requires and ensures that the current thread holds the `Mutex`.
-  bool WaitWithDeadline(Mutex *mu, absl::Time deadline);
+  bool WaitWithDeadline(Mutex* mu, absl::Time deadline);
 
   // CondVar::Signal()
   //
@@ -892,18 +935,17 @@ class CondVar {
   // Causes all subsequent uses of this `CondVar` to be logged via
   // `ABSL_RAW_LOG(INFO)`. Log entries are tagged with `name` if `name != 0`.
   // Note: this method substantially reduces `CondVar` performance.
-  void EnableDebugLog(const char *name);
+  void EnableDebugLog(const char* name);
 
  private:
-  bool WaitCommon(Mutex *mutex, synchronization_internal::KernelTimeout t);
-  void Remove(base_internal::PerThreadSynch *s);
-  void Wakeup(base_internal::PerThreadSynch *w);
+  bool WaitCommon(Mutex* mutex, synchronization_internal::KernelTimeout t);
+  void Remove(base_internal::PerThreadSynch* s);
+  void Wakeup(base_internal::PerThreadSynch* w);
   std::atomic<intptr_t> cv_;  // Condition variable state.
   CondVar(const CondVar&) = delete;
   CondVar& operator=(const CondVar&) = delete;
 };
 
-
 // Variants of MutexLock.
 //
 // If you find yourself using one of these, consider instead using
@@ -914,14 +956,14 @@ class CondVar {
 // MutexLockMaybe is like MutexLock, but is a no-op when mu is null.
 class ABSL_SCOPED_LOCKABLE MutexLockMaybe {
  public:
-  explicit MutexLockMaybe(Mutex *mu) ABSL_EXCLUSIVE_LOCK_FUNCTION(mu)
+  explicit MutexLockMaybe(Mutex* mu) ABSL_EXCLUSIVE_LOCK_FUNCTION(mu)
       : mu_(mu) {
     if (this->mu_ != nullptr) {
       this->mu_->Lock();
     }
   }
 
-  explicit MutexLockMaybe(Mutex *mu, const Condition &cond)
+  explicit MutexLockMaybe(Mutex* mu, const Condition& cond)
       ABSL_EXCLUSIVE_LOCK_FUNCTION(mu)
       : mu_(mu) {
     if (this->mu_ != nullptr) {
@@ -930,11 +972,13 @@ class ABSL_SCOPED_LOCKABLE MutexLockMaybe {
   }
 
   ~MutexLockMaybe() ABSL_UNLOCK_FUNCTION() {
-    if (this->mu_ != nullptr) { this->mu_->Unlock(); }
+    if (this->mu_ != nullptr) {
+      this->mu_->Unlock();
+    }
   }
 
  private:
-  Mutex *const mu_;
+  Mutex* const mu_;
   MutexLockMaybe(const MutexLockMaybe&) = delete;
   MutexLockMaybe(MutexLockMaybe&&) = delete;
   MutexLockMaybe& operator=(const MutexLockMaybe&) = delete;
@@ -947,25 +991,27 @@ class ABSL_SCOPED_LOCKABLE MutexLockMaybe {
 // mutex before destruction. `Release()` may be called at most once.
 class ABSL_SCOPED_LOCKABLE ReleasableMutexLock {
  public:
-  explicit ReleasableMutexLock(Mutex *mu) ABSL_EXCLUSIVE_LOCK_FUNCTION(mu)
+  explicit ReleasableMutexLock(Mutex* mu) ABSL_EXCLUSIVE_LOCK_FUNCTION(mu)
       : mu_(mu) {
     this->mu_->Lock();
   }
 
-  explicit ReleasableMutexLock(Mutex *mu, const Condition &cond)
+  explicit ReleasableMutexLock(Mutex* mu, const Condition& cond)
       ABSL_EXCLUSIVE_LOCK_FUNCTION(mu)
       : mu_(mu) {
     this->mu_->LockWhen(cond);
   }
 
   ~ReleasableMutexLock() ABSL_UNLOCK_FUNCTION() {
-    if (this->mu_ != nullptr) { this->mu_->Unlock(); }
+    if (this->mu_ != nullptr) {
+      this->mu_->Unlock();
+    }
   }
 
   void Release() ABSL_UNLOCK_FUNCTION();
 
  private:
-  Mutex *mu_;
+  Mutex* mu_;
   ReleasableMutexLock(const ReleasableMutexLock&) = delete;
   ReleasableMutexLock(ReleasableMutexLock&&) = delete;
   ReleasableMutexLock& operator=(const ReleasableMutexLock&) = delete;
@@ -982,8 +1028,8 @@ inline CondVar::CondVar() : cv_(0) {}
 
 // static
 template <typename T>
-bool Condition::CastAndCallMethod(const Condition *c) {
-  T *object = static_cast<T *>(c->arg_);
+bool Condition::CastAndCallMethod(const Condition* c) {
+  T* object = static_cast<T*>(c->arg_);
   bool (T::*method_pointer)();
   c->ReadCallback(&method_pointer);
   return (object->*method_pointer)();
@@ -991,38 +1037,43 @@ bool Condition::CastAndCallMethod(const Condition *c) {
 
 // static
 template <typename T>
-bool Condition::CastAndCallFunction(const Condition *c) {
-  bool (*function)(T *);
+bool Condition::CastAndCallFunction(const Condition* c) {
+  bool (*function)(T*);
   c->ReadCallback(&function);
-  T *argument = static_cast<T *>(c->arg_);
+  T* argument = static_cast<T*>(c->arg_);
   return (*function)(argument);
 }
 
 template <typename T>
-inline Condition::Condition(bool (*func)(T *), T *arg)
+inline Condition::Condition(bool (*func)(T*), T* arg)
     : eval_(&CastAndCallFunction<T>),
-      arg_(const_cast<void *>(static_cast<const void *>(arg))) {
+      arg_(const_cast<void*>(static_cast<const void*>(arg))) {
   static_assert(sizeof(&func) <= sizeof(callback_),
                 "An overlarge function pointer was passed to Condition.");
   StoreCallback(func);
 }
 
+template <typename T, typename>
+inline Condition::Condition(bool (*func)(T*),
+                            typename absl::internal::identity<T>::type* arg)
+    // Just delegate to the overload above.
+    : Condition(func, arg) {}
+
 template <typename T>
-inline Condition::Condition(T *object,
+inline Condition::Condition(T* object,
                             bool (absl::internal::identity<T>::type::*method)())
-    : eval_(&CastAndCallMethod<T>),
-      arg_(object) {
+    : eval_(&CastAndCallMethod<T>), arg_(object) {
   static_assert(sizeof(&method) <= sizeof(callback_),
                 "An overlarge method pointer was passed to Condition.");
   StoreCallback(method);
 }
 
 template <typename T>
-inline Condition::Condition(const T *object,
+inline Condition::Condition(const T* object,
                             bool (absl::internal::identity<T>::type::*method)()
                                 const)
     : eval_(&CastAndCallMethod<T>),
-      arg_(reinterpret_cast<void *>(const_cast<T *>(object))) {
+      arg_(reinterpret_cast<void*>(const_cast<T*>(object))) {
   StoreCallback(method);
 }
 
@@ -1052,7 +1103,7 @@ void RegisterMutexProfiler(void (*fn)(int64_t wait_cycles));
 //
 // This has the same ordering and single-use limitations as
 // RegisterMutexProfiler() above.
-void RegisterMutexTracer(void (*fn)(const char *msg, const void *obj,
+void RegisterMutexTracer(void (*fn)(const char* msg, const void* obj,
                                     int64_t wait_cycles));
 
 // Register a hook for CondVar tracing.
@@ -1067,24 +1118,7 @@ void RegisterMutexTracer(void (*fn)(const char *msg, const void *obj,
 //
 // This has the same ordering and single-use limitations as
 // RegisterMutexProfiler() above.
-void RegisterCondVarTracer(void (*fn)(const char *msg, const void *cv));
-
-// Register a hook for symbolizing stack traces in deadlock detector reports.
-//
-// 'pc' is the program counter being symbolized, 'out' is the buffer to write
-// into, and 'out_size' is the size of the buffer.  This function can return
-// false if symbolizing failed, or true if a NUL-terminated symbol was written
-// to 'out.'
-//
-// This has the same ordering and single-use limitations as
-// RegisterMutexProfiler() above.
-//
-// DEPRECATED: The default symbolizer function is absl::Symbolize() and the
-// ability to register a different hook for symbolizing stack traces will be
-// removed on or after 2023-05-01.
-ABSL_DEPRECATED("absl::RegisterSymbolizer() is deprecated and will be removed "
-                "on or after 2023-05-01")
-void RegisterSymbolizer(bool (*fn)(const void *pc, char *out, int out_size));
+void RegisterCondVarTracer(void (*fn)(const char* msg, const void* cv));
 
 // EnableMutexInvariantDebugging()
 //
@@ -1101,7 +1135,7 @@ void EnableMutexInvariantDebugging(bool enabled);
 enum class OnDeadlockCycle {
   kIgnore,  // Neither report on nor attempt to track cycles in lock ordering
   kReport,  // Report lock cycles to stderr when detected
-  kAbort,  // Report lock cycles to stderr when detected, then abort
+  kAbort,   // Report lock cycles to stderr when detected, then abort
 };
 
 // SetMutexDeadlockDetectionMode()
diff --git a/absl/synchronization/mutex_method_pointer_test.cc b/absl/synchronization/mutex_method_pointer_test.cc
index 1ec801a0..f4c82d27 100644
--- a/absl/synchronization/mutex_method_pointer_test.cc
+++ b/absl/synchronization/mutex_method_pointer_test.cc
@@ -26,8 +26,8 @@ class IncompleteClass;
 
 #ifdef _MSC_VER
 // These tests verify expectations about sizes of MSVC pointers to methods.
-// Pointers to methods are distinguished by whether their class hierachies
-// contain single inheritance, multiple inheritance, or virtual inheritence.
+// Pointers to methods are distinguished by whether their class hierarchies
+// contain single inheritance, multiple inheritance, or virtual inheritance.
 
 // Declare classes of the various MSVC inheritance types.
 class __single_inheritance SingleInheritance{};
diff --git a/absl/synchronization/mutex_test.cc b/absl/synchronization/mutex_test.cc
index 34751cb1..b585c342 100644
--- a/absl/synchronization/mutex_test.cc
+++ b/absl/synchronization/mutex_test.cc
@@ -32,8 +32,9 @@
 #include "gtest/gtest.h"
 #include "absl/base/attributes.h"
 #include "absl/base/config.h"
-#include "absl/base/internal/raw_logging.h"
 #include "absl/base/internal/sysinfo.h"
+#include "absl/log/check.h"
+#include "absl/log/log.h"
 #include "absl/memory/memory.h"
 #include "absl/synchronization/internal/thread_pool.h"
 #include "absl/time/clock.h"
@@ -87,7 +88,7 @@ static void SetInvariantChecked(bool new_value) {
 
 static void CheckSumG0G1(void *v) {
   TestContext *cxt = static_cast<TestContext *>(v);
-  ABSL_RAW_CHECK(cxt->g0 == -cxt->g1, "Error in CheckSumG0G1");
+  CHECK_EQ(cxt->g0, -cxt->g1) << "Error in CheckSumG0G1";
   SetInvariantChecked(true);
 }
 
@@ -132,7 +133,7 @@ static void TestRW(TestContext *cxt, int c) {
   } else {
     for (int i = 0; i != cxt->iterations; i++) {
       absl::ReaderMutexLock l(&cxt->mu);
-      ABSL_RAW_CHECK(cxt->g0 == -cxt->g1, "Error in TestRW");
+      CHECK_EQ(cxt->g0, -cxt->g1) << "Error in TestRW";
       cxt->mu.AssertReaderHeld();
     }
   }
@@ -157,7 +158,7 @@ static void TestAwait(TestContext *cxt, int c) {
   cxt->mu.AssertHeld();
   while (cxt->g0 < cxt->iterations) {
     cxt->mu.Await(absl::Condition(&mc, &MyContext::MyTurn));
-    ABSL_RAW_CHECK(mc.MyTurn(), "Error in TestAwait");
+    CHECK(mc.MyTurn()) << "Error in TestAwait";
     cxt->mu.AssertHeld();
     if (cxt->g0 < cxt->iterations) {
       int a = cxt->g0 + 1;
@@ -185,7 +186,7 @@ static void TestSignalAll(TestContext *cxt, int c) {
 }
 
 static void TestSignal(TestContext *cxt, int c) {
-  ABSL_RAW_CHECK(cxt->threads == 2, "TestSignal should use 2 threads");
+  CHECK_EQ(cxt->threads, 2) << "TestSignal should use 2 threads";
   int target = c;
   absl::MutexLock l(&cxt->mu);
   cxt->mu.AssertHeld();
@@ -222,8 +223,8 @@ static void TestCVTimeout(TestContext *cxt, int c) {
 static bool G0GE2(TestContext *cxt) { return cxt->g0 >= 2; }
 
 static void TestTime(TestContext *cxt, int c, bool use_cv) {
-  ABSL_RAW_CHECK(cxt->iterations == 1, "TestTime should only use 1 iteration");
-  ABSL_RAW_CHECK(cxt->threads > 2, "TestTime should use more than 2 threads");
+  CHECK_EQ(cxt->iterations, 1) << "TestTime should only use 1 iteration";
+  CHECK_GT(cxt->threads, 2) << "TestTime should use more than 2 threads";
   const bool kFalse = false;
   absl::Condition false_cond(&kFalse);
   absl::Condition g0ge2(G0GE2, cxt);
@@ -234,26 +235,24 @@ static void TestTime(TestContext *cxt, int c, bool use_cv) {
     if (use_cv) {
       cxt->cv.WaitWithTimeout(&cxt->mu, absl::Seconds(1));
     } else {
-      ABSL_RAW_CHECK(!cxt->mu.AwaitWithTimeout(false_cond, absl::Seconds(1)),
-                     "TestTime failed");
+      CHECK(!cxt->mu.AwaitWithTimeout(false_cond, absl::Seconds(1)))
+          << "TestTime failed";
     }
     absl::Duration elapsed = absl::Now() - start;
-    ABSL_RAW_CHECK(
-        absl::Seconds(0.9) <= elapsed && elapsed <= absl::Seconds(2.0),
-        "TestTime failed");
-    ABSL_RAW_CHECK(cxt->g0 == 1, "TestTime failed");
+    CHECK(absl::Seconds(0.9) <= elapsed && elapsed <= absl::Seconds(2.0))
+        << "TestTime failed";
+    CHECK_EQ(cxt->g0, 1) << "TestTime failed";
 
     start = absl::Now();
     if (use_cv) {
       cxt->cv.WaitWithTimeout(&cxt->mu, absl::Seconds(1));
     } else {
-      ABSL_RAW_CHECK(!cxt->mu.AwaitWithTimeout(false_cond, absl::Seconds(1)),
-                     "TestTime failed");
+      CHECK(!cxt->mu.AwaitWithTimeout(false_cond, absl::Seconds(1)))
+          << "TestTime failed";
     }
     elapsed = absl::Now() - start;
-    ABSL_RAW_CHECK(
-        absl::Seconds(0.9) <= elapsed && elapsed <= absl::Seconds(2.0),
-        "TestTime failed");
+    CHECK(absl::Seconds(0.9) <= elapsed && elapsed <= absl::Seconds(2.0))
+        << "TestTime failed";
     cxt->g0++;
     if (use_cv) {
       cxt->cv.Signal();
@@ -263,26 +262,24 @@ static void TestTime(TestContext *cxt, int c, bool use_cv) {
     if (use_cv) {
       cxt->cv.WaitWithTimeout(&cxt->mu, absl::Seconds(4));
     } else {
-      ABSL_RAW_CHECK(!cxt->mu.AwaitWithTimeout(false_cond, absl::Seconds(4)),
-                     "TestTime failed");
+      CHECK(!cxt->mu.AwaitWithTimeout(false_cond, absl::Seconds(4)))
+          << "TestTime failed";
     }
     elapsed = absl::Now() - start;
-    ABSL_RAW_CHECK(
-        absl::Seconds(3.9) <= elapsed && elapsed <= absl::Seconds(6.0),
-        "TestTime failed");
-    ABSL_RAW_CHECK(cxt->g0 >= 3, "TestTime failed");
+    CHECK(absl::Seconds(3.9) <= elapsed && elapsed <= absl::Seconds(6.0))
+        << "TestTime failed";
+    CHECK_GE(cxt->g0, 3) << "TestTime failed";
 
     start = absl::Now();
     if (use_cv) {
       cxt->cv.WaitWithTimeout(&cxt->mu, absl::Seconds(1));
     } else {
-      ABSL_RAW_CHECK(!cxt->mu.AwaitWithTimeout(false_cond, absl::Seconds(1)),
-                     "TestTime failed");
+      CHECK(!cxt->mu.AwaitWithTimeout(false_cond, absl::Seconds(1)))
+          << "TestTime failed";
     }
     elapsed = absl::Now() - start;
-    ABSL_RAW_CHECK(
-        absl::Seconds(0.9) <= elapsed && elapsed <= absl::Seconds(2.0),
-        "TestTime failed");
+    CHECK(absl::Seconds(0.9) <= elapsed && elapsed <= absl::Seconds(2.0))
+        << "TestTime failed";
     if (use_cv) {
       cxt->cv.SignalAll();
     }
@@ -291,14 +288,13 @@ static void TestTime(TestContext *cxt, int c, bool use_cv) {
     if (use_cv) {
       cxt->cv.WaitWithTimeout(&cxt->mu, absl::Seconds(1));
     } else {
-      ABSL_RAW_CHECK(!cxt->mu.AwaitWithTimeout(false_cond, absl::Seconds(1)),
-                     "TestTime failed");
+      CHECK(!cxt->mu.AwaitWithTimeout(false_cond, absl::Seconds(1)))
+          << "TestTime failed";
     }
     elapsed = absl::Now() - start;
-    ABSL_RAW_CHECK(
-        absl::Seconds(0.9) <= elapsed && elapsed <= absl::Seconds(2.0),
-        "TestTime failed");
-    ABSL_RAW_CHECK(cxt->g0 == cxt->threads, "TestTime failed");
+    CHECK(absl::Seconds(0.9) <= elapsed && elapsed <= absl::Seconds(2.0))
+        << "TestTime failed";
+    CHECK_EQ(cxt->g0, cxt->threads) << "TestTime failed";
 
   } else if (c == 1) {
     absl::MutexLock l(&cxt->mu);
@@ -306,14 +302,12 @@ static void TestTime(TestContext *cxt, int c, bool use_cv) {
     if (use_cv) {
       cxt->cv.WaitWithTimeout(&cxt->mu, absl::Milliseconds(500));
     } else {
-      ABSL_RAW_CHECK(
-          !cxt->mu.AwaitWithTimeout(false_cond, absl::Milliseconds(500)),
-          "TestTime failed");
+      CHECK(!cxt->mu.AwaitWithTimeout(false_cond, absl::Milliseconds(500)))
+          << "TestTime failed";
     }
     const absl::Duration elapsed = absl::Now() - start;
-    ABSL_RAW_CHECK(
-        absl::Seconds(0.4) <= elapsed && elapsed <= absl::Seconds(0.9),
-        "TestTime failed");
+    CHECK(absl::Seconds(0.4) <= elapsed && elapsed <= absl::Seconds(0.9))
+        << "TestTime failed";
     cxt->g0++;
   } else if (c == 2) {
     absl::MutexLock l(&cxt->mu);
@@ -322,8 +316,8 @@ static void TestTime(TestContext *cxt, int c, bool use_cv) {
         cxt->cv.WaitWithTimeout(&cxt->mu, absl::Seconds(100));
       }
     } else {
-      ABSL_RAW_CHECK(cxt->mu.AwaitWithTimeout(g0ge2, absl::Seconds(100)),
-                     "TestTime failed");
+      CHECK(cxt->mu.AwaitWithTimeout(g0ge2, absl::Seconds(100)))
+          << "TestTime failed";
     }
     cxt->g0++;
   } else {
@@ -400,7 +394,7 @@ static int RunTestWithInvariantDebugging(void (*test)(TestContext *cxt, int),
   TestContext cxt;
   cxt.mu.EnableInvariantDebugging(invariant, &cxt);
   int ret = RunTestCommon(&cxt, test, threads, iterations, operations);
-  ABSL_RAW_CHECK(GetInvariantChecked(), "Invariant not checked");
+  CHECK(GetInvariantChecked()) << "Invariant not checked";
   absl::EnableMutexInvariantDebugging(false);  // Restore.
   return ret;
 }
@@ -872,6 +866,111 @@ TEST(Mutex, LockedMutexDestructionBug) ABSL_NO_THREAD_SAFETY_ANALYSIS {
   }
 }
 
+// Some functions taking pointers to non-const.
+bool Equals42(int *p) { return *p == 42; }
+bool Equals43(int *p) { return *p == 43; }
+
+// Some functions taking pointers to const.
+bool ConstEquals42(const int *p) { return *p == 42; }
+bool ConstEquals43(const int *p) { return *p == 43; }
+
+// Some function templates taking pointers. Note it's possible for `T` to be
+// deduced as non-const or const, which creates the potential for ambiguity,
+// but which the implementation is careful to avoid.
+template <typename T>
+bool TemplateEquals42(T *p) {
+  return *p == 42;
+}
+template <typename T>
+bool TemplateEquals43(T *p) {
+  return *p == 43;
+}
+
+TEST(Mutex, FunctionPointerCondition) {
+  // Some arguments.
+  int x = 42;
+  const int const_x = 42;
+
+  // Parameter non-const, argument non-const.
+  EXPECT_TRUE(absl::Condition(Equals42, &x).Eval());
+  EXPECT_FALSE(absl::Condition(Equals43, &x).Eval());
+
+  // Parameter const, argument non-const.
+  EXPECT_TRUE(absl::Condition(ConstEquals42, &x).Eval());
+  EXPECT_FALSE(absl::Condition(ConstEquals43, &x).Eval());
+
+  // Parameter const, argument const.
+  EXPECT_TRUE(absl::Condition(ConstEquals42, &const_x).Eval());
+  EXPECT_FALSE(absl::Condition(ConstEquals43, &const_x).Eval());
+
+  // Parameter type deduced, argument non-const.
+  EXPECT_TRUE(absl::Condition(TemplateEquals42, &x).Eval());
+  EXPECT_FALSE(absl::Condition(TemplateEquals43, &x).Eval());
+
+  // Parameter type deduced, argument const.
+  EXPECT_TRUE(absl::Condition(TemplateEquals42, &const_x).Eval());
+  EXPECT_FALSE(absl::Condition(TemplateEquals43, &const_x).Eval());
+
+  // Parameter non-const, argument const is not well-formed.
+  EXPECT_FALSE((std::is_constructible<absl::Condition, decltype(Equals42),
+                                      decltype(&const_x)>::value));
+  // Validate use of is_constructible by contrasting to a well-formed case.
+  EXPECT_TRUE((std::is_constructible<absl::Condition, decltype(ConstEquals42),
+                                     decltype(&const_x)>::value));
+}
+
+// Example base and derived class for use in predicates and test below. Not a
+// particularly realistic example, but it suffices for testing purposes.
+struct Base {
+  explicit Base(int v) : value(v) {}
+  int value;
+};
+struct Derived : Base {
+  explicit Derived(int v) : Base(v) {}
+};
+
+// Some functions taking pointer to non-const `Base`.
+bool BaseEquals42(Base *p) { return p->value == 42; }
+bool BaseEquals43(Base *p) { return p->value == 43; }
+
+// Some functions taking pointer to const `Base`.
+bool ConstBaseEquals42(const Base *p) { return p->value == 42; }
+bool ConstBaseEquals43(const Base *p) { return p->value == 43; }
+
+TEST(Mutex, FunctionPointerConditionWithDerivedToBaseConversion) {
+  // Some arguments.
+  Derived derived(42);
+  const Derived const_derived(42);
+
+  // Parameter non-const base, argument derived non-const.
+  EXPECT_TRUE(absl::Condition(BaseEquals42, &derived).Eval());
+  EXPECT_FALSE(absl::Condition(BaseEquals43, &derived).Eval());
+
+  // Parameter const base, argument derived non-const.
+  EXPECT_TRUE(absl::Condition(ConstBaseEquals42, &derived).Eval());
+  EXPECT_FALSE(absl::Condition(ConstBaseEquals43, &derived).Eval());
+
+  // Parameter const base, argument derived const.
+  EXPECT_TRUE(absl::Condition(ConstBaseEquals42, &const_derived).Eval());
+  EXPECT_FALSE(absl::Condition(ConstBaseEquals43, &const_derived).Eval());
+
+  // Parameter const base, argument derived const.
+  EXPECT_TRUE(absl::Condition(ConstBaseEquals42, &const_derived).Eval());
+  EXPECT_FALSE(absl::Condition(ConstBaseEquals43, &const_derived).Eval());
+
+  // Parameter derived, argument base is not well-formed.
+  bool (*derived_pred)(const Derived *) = [](const Derived *) { return true; };
+  EXPECT_FALSE((std::is_constructible<absl::Condition, decltype(derived_pred),
+                                      Base *>::value));
+  EXPECT_FALSE((std::is_constructible<absl::Condition, decltype(derived_pred),
+                                      const Base *>::value));
+  // Validate use of is_constructible by contrasting to well-formed cases.
+  EXPECT_TRUE((std::is_constructible<absl::Condition, decltype(derived_pred),
+                                     Derived *>::value));
+  EXPECT_TRUE((std::is_constructible<absl::Condition, decltype(derived_pred),
+                                     const Derived *>::value));
+}
+
 struct True {
   template <class... Args>
   bool operator()(Args...) const {
@@ -988,7 +1087,7 @@ static bool ConditionWithAcquire(AcquireFromConditionStruct *x) {
                                absl::Milliseconds(100));
     x->mu1.Unlock();
   }
-  ABSL_RAW_CHECK(x->value < 4, "should not be invoked a fourth time");
+  CHECK_LT(x->value, 4) << "should not be invoked a fourth time";
 
   // We arrange for the condition to return true on only the 2nd and 3rd calls.
   return x->value == 2 || x->value == 3;
@@ -1131,6 +1230,25 @@ TEST(Mutex, DeadlockDetectorBazelWarning) {
   absl::SetMutexDeadlockDetectionMode(absl::OnDeadlockCycle::kAbort);
 }
 
+TEST(Mutex, DeadlockDetectorLongCycle) {
+  absl::SetMutexDeadlockDetectionMode(absl::OnDeadlockCycle::kReport);
+
+  // This test generates a warning if it passes, and crashes otherwise.
+  // Cause bazel to ignore the warning.
+  ScopedDisableBazelTestWarnings disable_bazel_test_warnings;
+
+  // Check that we survive a deadlock with a lock cycle.
+  std::vector<absl::Mutex> mutex(100);
+  for (size_t i = 0; i != mutex.size(); i++) {
+    mutex[i].Lock();
+    mutex[(i + 1) % mutex.size()].Lock();
+    mutex[i].Unlock();
+    mutex[(i + 1) % mutex.size()].Unlock();
+  }
+
+  absl::SetMutexDeadlockDetectionMode(absl::OnDeadlockCycle::kAbort);
+}
+
 // This test is tagged with NO_THREAD_SAFETY_ANALYSIS because the
 // annotation-based static thread-safety analysis is not currently
 // predicate-aware and cannot tell if the two for-loops that acquire and
@@ -1216,11 +1334,9 @@ static bool DelayIsWithinBounds(absl::Duration expected_delay,
   // different clock than absl::Now(), but these cases should be handled by the
   // the retry mechanism in each TimeoutTest.
   if (actual_delay < expected_delay) {
-    ABSL_RAW_LOG(WARNING,
-                 "Actual delay %s was too short, expected %s (difference %s)",
-                 absl::FormatDuration(actual_delay).c_str(),
-                 absl::FormatDuration(expected_delay).c_str(),
-                 absl::FormatDuration(actual_delay - expected_delay).c_str());
+    LOG(WARNING) << "Actual delay " << actual_delay
+                 << " was too short, expected " << expected_delay
+                 << " (difference " << actual_delay - expected_delay << ")";
     pass = false;
   }
   // If the expected delay is <= zero then allow a small error tolerance, since
@@ -1231,11 +1347,9 @@ static bool DelayIsWithinBounds(absl::Duration expected_delay,
                                  ? absl::Milliseconds(10)
                                  : TimeoutTestAllowedSchedulingDelay();
   if (actual_delay > expected_delay + tolerance) {
-    ABSL_RAW_LOG(WARNING,
-                 "Actual delay %s was too long, expected %s (difference %s)",
-                 absl::FormatDuration(actual_delay).c_str(),
-                 absl::FormatDuration(expected_delay).c_str(),
-                 absl::FormatDuration(actual_delay - expected_delay).c_str());
+    LOG(WARNING) << "Actual delay " << actual_delay
+                 << " was too long, expected " << expected_delay
+                 << " (difference " << actual_delay - expected_delay << ")";
     pass = false;
   }
   return pass;
@@ -1285,12 +1399,6 @@ std::ostream &operator<<(std::ostream &os, const TimeoutTestParam &param) {
             << " expected_delay: " << param.expected_delay;
 }
 
-std::string FormatString(const TimeoutTestParam &param) {
-  std::ostringstream os;
-  os << param;
-  return os.str();
-}
-
 // Like `thread::Executor::ScheduleAt` except:
 // a) Delays zero or negative are executed immediately in the current thread.
 // b) Infinite delays are never scheduled.
@@ -1420,13 +1528,13 @@ INSTANTIATE_TEST_SUITE_P(All, TimeoutTest,
 
 TEST_P(TimeoutTest, Await) {
   const TimeoutTestParam params = GetParam();
-  ABSL_RAW_LOG(INFO, "Params: %s", FormatString(params).c_str());
+  LOG(INFO) << "Params: " << params;
 
   // Because this test asserts bounds on scheduling delays it is flaky.  To
   // compensate it loops forever until it passes.  Failures express as test
   // timeouts, in which case the test log can be used to diagnose the issue.
   for (int attempt = 1;; ++attempt) {
-    ABSL_RAW_LOG(INFO, "Attempt %d", attempt);
+    LOG(INFO) << "Attempt " << attempt;
 
     absl::Mutex mu;
     bool value = false;  // condition value (under mu)
@@ -1454,13 +1562,13 @@ TEST_P(TimeoutTest, Await) {
 
 TEST_P(TimeoutTest, LockWhen) {
   const TimeoutTestParam params = GetParam();
-  ABSL_RAW_LOG(INFO, "Params: %s", FormatString(params).c_str());
+  LOG(INFO) << "Params: " << params;
 
   // Because this test asserts bounds on scheduling delays it is flaky.  To
   // compensate it loops forever until it passes.  Failures express as test
   // timeouts, in which case the test log can be used to diagnose the issue.
   for (int attempt = 1;; ++attempt) {
-    ABSL_RAW_LOG(INFO, "Attempt %d", attempt);
+    LOG(INFO) << "Attempt " << attempt;
 
     absl::Mutex mu;
     bool value = false;  // condition value (under mu)
@@ -1489,13 +1597,13 @@ TEST_P(TimeoutTest, LockWhen) {
 
 TEST_P(TimeoutTest, ReaderLockWhen) {
   const TimeoutTestParam params = GetParam();
-  ABSL_RAW_LOG(INFO, "Params: %s", FormatString(params).c_str());
+  LOG(INFO) << "Params: " << params;
 
   // Because this test asserts bounds on scheduling delays it is flaky.  To
   // compensate it loops forever until it passes.  Failures express as test
   // timeouts, in which case the test log can be used to diagnose the issue.
   for (int attempt = 0;; ++attempt) {
-    ABSL_RAW_LOG(INFO, "Attempt %d", attempt);
+    LOG(INFO) << "Attempt " << attempt;
 
     absl::Mutex mu;
     bool value = false;  // condition value (under mu)
@@ -1525,13 +1633,13 @@ TEST_P(TimeoutTest, ReaderLockWhen) {
 
 TEST_P(TimeoutTest, Wait) {
   const TimeoutTestParam params = GetParam();
-  ABSL_RAW_LOG(INFO, "Params: %s", FormatString(params).c_str());
+  LOG(INFO) << "Params: " << params;
 
   // Because this test asserts bounds on scheduling delays it is flaky.  To
   // compensate it loops forever until it passes.  Failures express as test
   // timeouts, in which case the test log can be used to diagnose the issue.
   for (int attempt = 0;; ++attempt) {
-    ABSL_RAW_LOG(INFO, "Attempt %d", attempt);
+    LOG(INFO) << "Attempt " << attempt;
 
     absl::Mutex mu;
     bool value = false;  // condition value (under mu)
@@ -1730,4 +1838,59 @@ TEST(Mutex, SignalExitedThread) {
   for (auto &th : top) th.join();
 }
 
+TEST(Mutex, WriterPriority) {
+  absl::Mutex mu;
+  bool wrote = false;
+  std::atomic<bool> saw_wrote{false};
+  auto readfunc = [&]() {
+    for (size_t i = 0; i < 10; ++i) {
+      absl::ReaderMutexLock lock(&mu);
+      if (wrote) {
+        saw_wrote = true;
+        break;
+      }
+      absl::SleepFor(absl::Seconds(1));
+    }
+  };
+  std::thread t1(readfunc);
+  absl::SleepFor(absl::Milliseconds(500));
+  std::thread t2(readfunc);
+  // Note: this test guards against a bug that was related to an uninit
+  // PerThreadSynch::priority, so the writer intentionally runs on a new thread.
+  std::thread t3([&]() {
+    // The writer should be able squeeze between the two alternating readers.
+    absl::MutexLock lock(&mu);
+    wrote = true;
+  });
+  t1.join();
+  t2.join();
+  t3.join();
+  EXPECT_TRUE(saw_wrote.load());
+}
+
+TEST(Mutex, LockWhenWithTimeoutResult) {
+  // Check various corner cases for Await/LockWhen return value
+  // with always true/always false conditions.
+  absl::Mutex mu;
+  const bool kAlwaysTrue = true, kAlwaysFalse = false;
+  const absl::Condition kTrueCond(&kAlwaysTrue), kFalseCond(&kAlwaysFalse);
+  EXPECT_TRUE(mu.LockWhenWithTimeout(kTrueCond, absl::Milliseconds(1)));
+  mu.Unlock();
+  EXPECT_FALSE(mu.LockWhenWithTimeout(kFalseCond, absl::Milliseconds(1)));
+  EXPECT_TRUE(mu.AwaitWithTimeout(kTrueCond, absl::Milliseconds(1)));
+  EXPECT_FALSE(mu.AwaitWithTimeout(kFalseCond, absl::Milliseconds(1)));
+  std::thread th1([&]() {
+    EXPECT_TRUE(mu.LockWhenWithTimeout(kTrueCond, absl::Milliseconds(1)));
+    mu.Unlock();
+  });
+  std::thread th2([&]() {
+    EXPECT_FALSE(mu.LockWhenWithTimeout(kFalseCond, absl::Milliseconds(1)));
+    mu.Unlock();
+  });
+  absl::SleepFor(absl::Milliseconds(100));
+  mu.Unlock();
+  th1.join();
+  th2.join();
+}
+
 }  // namespace
diff --git a/absl/synchronization/notification_test.cc b/absl/synchronization/notification_test.cc
index 100ea76f..49ce61a5 100644
--- a/absl/synchronization/notification_test.cc
+++ b/absl/synchronization/notification_test.cc
@@ -79,7 +79,7 @@ static void BasicTests(bool notify_before_waiting, Notification* notification) {
 
   // Allow for a slight early return, to account for quality of implementation
   // issues on various platforms.
-  const absl::Duration slop = absl::Microseconds(200);
+  const absl::Duration slop = absl::Milliseconds(5);
   EXPECT_LE(delay - slop, elapsed)
       << "WaitForNotificationWithTimeout returned " << delay - elapsed
       << " early (with " << slop << " slop), start time was " << start;
diff --git a/absl/time/BUILD.bazel b/absl/time/BUILD.bazel
index c7b07c2f..88d20887 100644
--- a/absl/time/BUILD.bazel
+++ b/absl/time/BUILD.bazel
@@ -91,6 +91,7 @@ cc_test(
         "//absl/base:config",
         "//absl/base:core_headers",
         "//absl/numeric:int128",
+        "//absl/strings:str_format",
         "//absl/time/internal/cctz:time_zone",
         "@com_google_googletest//:gtest_main",
     ],
diff --git a/absl/time/CMakeLists.txt b/absl/time/CMakeLists.txt
index 7b720540..e1ade7a3 100644
--- a/absl/time/CMakeLists.txt
+++ b/absl/time/CMakeLists.txt
@@ -54,10 +54,6 @@ absl_cc_library(
     ${ABSL_DEFAULT_COPTS}
 )
 
-if(APPLE)
-  find_library(CoreFoundation CoreFoundation)
-endif()
-
 absl_cc_library(
   NAME
     time_zone
@@ -84,7 +80,10 @@ absl_cc_library(
   COPTS
     ${ABSL_DEFAULT_COPTS}
   DEPS
-    $<$<PLATFORM_ID:Darwin>:${CoreFoundation}>
+    Threads::Threads
+    # TODO(#1495): Use $<LINK_LIBRARY:FRAMEWORK,CoreFoundation> once our
+    # minimum CMake version >= 3.24
+    $<$<PLATFORM_ID:Darwin>:-Wl,-framework,CoreFoundation>
 )
 
 # Internal-only target, do not depend on directly.
@@ -122,6 +121,8 @@ absl_cc_test(
     absl::time
     absl::config
     absl::core_headers
+    absl::strings
+    absl::str_format
     absl::time_zone
     GTest::gmock_main
 )
diff --git a/absl/time/civil_time_test.cc b/absl/time/civil_time_test.cc
index 0ebd97ad..ec435ac7 100644
--- a/absl/time/civil_time_test.cc
+++ b/absl/time/civil_time_test.cc
@@ -1228,7 +1228,7 @@ TEST(CivilTime, DocumentationExample) {
   EXPECT_EQ(0, day_floor.hour());  // 09:09:09 is floored
   EXPECT_EQ(absl::CivilDay(2015, 1, 2), day_floor);
 
-  // Unspecified fields default to their minium value
+  // Unspecified fields default to their minimum value
   absl::CivilDay day_default(2015);  // Defaults to Jan 1
   EXPECT_EQ(absl::CivilDay(2015, 1, 1), day_default);
 
diff --git a/absl/time/clock.cc b/absl/time/clock.cc
index 2bf53d9c..aa74367b 100644
--- a/absl/time/clock.cc
+++ b/absl/time/clock.cc
@@ -48,17 +48,16 @@ Time Now() {
 ABSL_NAMESPACE_END
 }  // namespace absl
 
-// Decide if we should use the fast GetCurrentTimeNanos() algorithm
-// based on the cyclecounter, otherwise just get the time directly
-// from the OS on every call. This can be chosen at compile-time via
+// Decide if we should use the fast GetCurrentTimeNanos() algorithm based on the
+// cyclecounter, otherwise just get the time directly from the OS on every call.
+// By default, the fast algorithm based on the cyclecount is disabled because in
+// certain situations, for example, if the OS enters a "sleep" mode, it may
+// produce incorrect values immediately upon waking.
+// This can be chosen at compile-time via
 // -DABSL_USE_CYCLECLOCK_FOR_GET_CURRENT_TIME_NANOS=[0|1]
 #ifndef ABSL_USE_CYCLECLOCK_FOR_GET_CURRENT_TIME_NANOS
-#if ABSL_USE_UNSCALED_CYCLECLOCK
-#define ABSL_USE_CYCLECLOCK_FOR_GET_CURRENT_TIME_NANOS 1
-#else
 #define ABSL_USE_CYCLECLOCK_FOR_GET_CURRENT_TIME_NANOS 0
 #endif
-#endif
 
 #if defined(__APPLE__) || defined(_WIN32)
 #include "absl/time/internal/get_current_time_chrono.inc"
diff --git a/absl/time/duration.cc b/absl/time/duration.cc
index 911e80f8..634e5d58 100644
--- a/absl/time/duration.cc
+++ b/absl/time/duration.cc
@@ -96,13 +96,6 @@ inline bool IsValidDivisor(double d) {
   return d != 0.0;
 }
 
-// Can't use std::round() because it is only available in C++11.
-// Note that we ignore the possibility of floating-point over/underflow.
-template <typename Double>
-inline double Round(Double d) {
-  return d < 0 ? std::ceil(d - 0.5) : std::floor(d + 0.5);
-}
-
 // *sec may be positive or negative.  *ticks must be in the range
 // -kTicksPerSecond < *ticks < kTicksPerSecond.  If *ticks is negative it
 // will be normalized to a positive value by adjusting *sec accordingly.
@@ -260,7 +253,7 @@ inline Duration ScaleDouble(Duration d, double r) {
   double lo_frac = std::modf(lo_doub, &lo_int);
 
   // Rolls lo into hi if necessary.
-  int64_t lo64 = Round(lo_frac * kTicksPerSecond);
+  int64_t lo64 = std::round(lo_frac * kTicksPerSecond);
 
   Duration ans;
   if (!SafeAddRepHi(hi_int, lo_int, &ans)) return ans;
@@ -407,16 +400,18 @@ int64_t IDivDuration(bool satq, const Duration num, const Duration den,
 Duration& Duration::operator+=(Duration rhs) {
   if (time_internal::IsInfiniteDuration(*this)) return *this;
   if (time_internal::IsInfiniteDuration(rhs)) return *this = rhs;
-  const int64_t orig_rep_hi = rep_hi_;
-  rep_hi_ =
-      DecodeTwosComp(EncodeTwosComp(rep_hi_) + EncodeTwosComp(rhs.rep_hi_));
+  const int64_t orig_rep_hi = rep_hi_.Get();
+  rep_hi_ = DecodeTwosComp(EncodeTwosComp(rep_hi_.Get()) +
+                           EncodeTwosComp(rhs.rep_hi_.Get()));
   if (rep_lo_ >= kTicksPerSecond - rhs.rep_lo_) {
-    rep_hi_ = DecodeTwosComp(EncodeTwosComp(rep_hi_) + 1);
+    rep_hi_ = DecodeTwosComp(EncodeTwosComp(rep_hi_.Get()) + 1);
     rep_lo_ -= kTicksPerSecond;
   }
   rep_lo_ += rhs.rep_lo_;
-  if (rhs.rep_hi_ < 0 ? rep_hi_ > orig_rep_hi : rep_hi_ < orig_rep_hi) {
-    return *this = rhs.rep_hi_ < 0 ? -InfiniteDuration() : InfiniteDuration();
+  if (rhs.rep_hi_.Get() < 0 ? rep_hi_.Get() > orig_rep_hi
+                            : rep_hi_.Get() < orig_rep_hi) {
+    return *this =
+               rhs.rep_hi_.Get() < 0 ? -InfiniteDuration() : InfiniteDuration();
   }
   return *this;
 }
@@ -424,18 +419,21 @@ Duration& Duration::operator+=(Duration rhs) {
 Duration& Duration::operator-=(Duration rhs) {
   if (time_internal::IsInfiniteDuration(*this)) return *this;
   if (time_internal::IsInfiniteDuration(rhs)) {
-    return *this = rhs.rep_hi_ >= 0 ? -InfiniteDuration() : InfiniteDuration();
+    return *this = rhs.rep_hi_.Get() >= 0 ? -InfiniteDuration()
+                                          : InfiniteDuration();
   }
-  const int64_t orig_rep_hi = rep_hi_;
-  rep_hi_ =
-      DecodeTwosComp(EncodeTwosComp(rep_hi_) - EncodeTwosComp(rhs.rep_hi_));
+  const int64_t orig_rep_hi = rep_hi_.Get();
+  rep_hi_ = DecodeTwosComp(EncodeTwosComp(rep_hi_.Get()) -
+                           EncodeTwosComp(rhs.rep_hi_.Get()));
   if (rep_lo_ < rhs.rep_lo_) {
-    rep_hi_ = DecodeTwosComp(EncodeTwosComp(rep_hi_) - 1);
+    rep_hi_ = DecodeTwosComp(EncodeTwosComp(rep_hi_.Get()) - 1);
     rep_lo_ += kTicksPerSecond;
   }
   rep_lo_ -= rhs.rep_lo_;
-  if (rhs.rep_hi_ < 0 ? rep_hi_ < orig_rep_hi : rep_hi_ > orig_rep_hi) {
-    return *this = rhs.rep_hi_ >= 0 ? -InfiniteDuration() : InfiniteDuration();
+  if (rhs.rep_hi_.Get() < 0 ? rep_hi_.Get() < orig_rep_hi
+                            : rep_hi_.Get() > orig_rep_hi) {
+    return *this = rhs.rep_hi_.Get() >= 0 ? -InfiniteDuration()
+                                          : InfiniteDuration();
   }
   return *this;
 }
@@ -446,7 +444,7 @@ Duration& Duration::operator-=(Duration rhs) {
 
 Duration& Duration::operator*=(int64_t r) {
   if (time_internal::IsInfiniteDuration(*this)) {
-    const bool is_neg = (r < 0) != (rep_hi_ < 0);
+    const bool is_neg = (r < 0) != (rep_hi_.Get() < 0);
     return *this = is_neg ? -InfiniteDuration() : InfiniteDuration();
   }
   return *this = ScaleFixed<SafeMultiply>(*this, r);
@@ -454,7 +452,7 @@ Duration& Duration::operator*=(int64_t r) {
 
 Duration& Duration::operator*=(double r) {
   if (time_internal::IsInfiniteDuration(*this) || !IsFinite(r)) {
-    const bool is_neg = (std::signbit(r) != 0) != (rep_hi_ < 0);
+    const bool is_neg = std::signbit(r) != (rep_hi_.Get() < 0);
     return *this = is_neg ? -InfiniteDuration() : InfiniteDuration();
   }
   return *this = ScaleDouble<std::multiplies>(*this, r);
@@ -462,7 +460,7 @@ Duration& Duration::operator*=(double r) {
 
 Duration& Duration::operator/=(int64_t r) {
   if (time_internal::IsInfiniteDuration(*this) || r == 0) {
-    const bool is_neg = (r < 0) != (rep_hi_ < 0);
+    const bool is_neg = (r < 0) != (rep_hi_.Get() < 0);
     return *this = is_neg ? -InfiniteDuration() : InfiniteDuration();
   }
   return *this = ScaleFixed<std::divides>(*this, r);
@@ -470,7 +468,7 @@ Duration& Duration::operator/=(int64_t r) {
 
 Duration& Duration::operator/=(double r) {
   if (time_internal::IsInfiniteDuration(*this) || !IsValidDivisor(r)) {
-    const bool is_neg = (std::signbit(r) != 0) != (rep_hi_ < 0);
+    const bool is_neg = std::signbit(r) != (rep_hi_.Get() < 0);
     return *this = is_neg ? -InfiniteDuration() : InfiniteDuration();
   }
   return *this = ScaleDouble<std::divides>(*this, r);
@@ -741,7 +739,7 @@ void AppendNumberUnit(std::string* out, double n, DisplayUnit unit) {
   char buf[kBufferSize];  // also large enough to hold integer part
   char* ep = buf + sizeof(buf);
   double d = 0;
-  int64_t frac_part = Round(std::modf(n, &d) * unit.pow10);
+  int64_t frac_part = std::round(std::modf(n, &d) * unit.pow10);
   int64_t int_part = d;
   if (int_part != 0 || frac_part != 0) {
     char* bp = Format64(ep, 0, int_part);  // always < 1000
diff --git a/absl/time/duration_test.cc b/absl/time/duration_test.cc
index b7abf4ba..dcf7aad6 100644
--- a/absl/time/duration_test.cc
+++ b/absl/time/duration_test.cc
@@ -16,8 +16,9 @@
 #include <winsock2.h>  // for timeval
 #endif
 
-#include <chrono>  // NOLINT(build/c++11)
+#include <array>
 #include <cfloat>
+#include <chrono>  // NOLINT(build/c++11)
 #include <cmath>
 #include <cstdint>
 #include <ctime>
@@ -28,6 +29,7 @@
 
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
+#include "absl/strings/str_format.h"
 #include "absl/time/time.h"
 
 namespace {
@@ -349,11 +351,6 @@ TEST(Duration, ToChrono) {
 }
 
 TEST(Duration, FactoryOverloads) {
-#if defined(ABSL_SKIP_TIME_TESTS_BROKEN_ON_MSVC_OPT) && \
-    ABSL_SKIP_TIME_TESTS_BROKEN_ON_MSVC_OPT
-  GTEST_SKIP();
-#endif
-
   enum E { kOne = 1 };
 #define TEST_FACTORY_OVERLOADS(NAME)                                          \
   EXPECT_EQ(1, NAME(kOne) / NAME(kOne));                                      \
@@ -884,11 +881,6 @@ TEST(Duration, RelationalOperators) {
 }
 
 TEST(Duration, Addition) {
-#if defined(ABSL_SKIP_TIME_TESTS_BROKEN_ON_MSVC_OPT) && \
-    ABSL_SKIP_TIME_TESTS_BROKEN_ON_MSVC_OPT
-  GTEST_SKIP();
-#endif
-
 #define TEST_ADD_OPS(UNIT)                  \
   do {                                      \
     EXPECT_EQ(UNIT(2), UNIT(1) + UNIT(1));  \
@@ -982,11 +974,6 @@ TEST(Duration, Negation) {
 }
 
 TEST(Duration, AbsoluteValue) {
-#if defined(ABSL_SKIP_TIME_TESTS_BROKEN_ON_MSVC_OPT) && \
-    ABSL_SKIP_TIME_TESTS_BROKEN_ON_MSVC_OPT
-  GTEST_SKIP();
-#endif
-
   EXPECT_EQ(absl::ZeroDuration(), AbsDuration(absl::ZeroDuration()));
   EXPECT_EQ(absl::Seconds(1), AbsDuration(absl::Seconds(1)));
   EXPECT_EQ(absl::Seconds(1), AbsDuration(absl::Seconds(-1)));
@@ -1004,11 +991,6 @@ TEST(Duration, AbsoluteValue) {
 }
 
 TEST(Duration, Multiplication) {
-#if defined(ABSL_SKIP_TIME_TESTS_BROKEN_ON_MSVC_OPT) && \
-    ABSL_SKIP_TIME_TESTS_BROKEN_ON_MSVC_OPT
-  GTEST_SKIP();
-#endif
-
 #define TEST_MUL_OPS(UNIT)                                    \
   do {                                                        \
     EXPECT_EQ(UNIT(5), UNIT(2) * 2.5);                        \
@@ -1261,11 +1243,6 @@ TEST(Duration, RoundTripUnits) {
 }
 
 TEST(Duration, TruncConversions) {
-#if defined(ABSL_SKIP_TIME_TESTS_BROKEN_ON_MSVC_OPT) && \
-    ABSL_SKIP_TIME_TESTS_BROKEN_ON_MSVC_OPT
-  GTEST_SKIP();
-#endif
-
   // Tests ToTimespec()/DurationFromTimespec()
   const struct {
     absl::Duration d;
@@ -1562,11 +1539,6 @@ TEST(Duration, ConversionSaturation) {
 }
 
 TEST(Duration, FormatDuration) {
-#if defined(ABSL_SKIP_TIME_TESTS_BROKEN_ON_MSVC_OPT) && \
-    ABSL_SKIP_TIME_TESTS_BROKEN_ON_MSVC_OPT
-  GTEST_SKIP();
-#endif
-
   // Example from Go's docs.
   EXPECT_EQ("72h3m0.5s",
             absl::FormatDuration(absl::Hours(72) + absl::Minutes(3) +
@@ -1701,11 +1673,6 @@ TEST(Duration, FormatDuration) {
 }
 
 TEST(Duration, ParseDuration) {
-#if defined(ABSL_SKIP_TIME_TESTS_BROKEN_ON_MSVC_OPT) && \
-    ABSL_SKIP_TIME_TESTS_BROKEN_ON_MSVC_OPT
-  GTEST_SKIP();
-#endif
-
   absl::Duration d;
 
   // No specified unit. Should only work for zero and infinity.
@@ -1853,4 +1820,18 @@ TEST(Duration, FormatParseRoundTrip) {
 #undef TEST_PARSE_ROUNDTRIP
 }
 
+TEST(Duration, AbslStringify) {
+  // FormatDuration is already well tested, so just use one test case here to
+  // verify that StrFormat("%v", d) works as expected.
+  absl::Duration d = absl::Seconds(1);
+  EXPECT_EQ(absl::StrFormat("%v", d), absl::FormatDuration(d));
+}
+
+TEST(Duration, NoPadding) {
+  // Should match the size of a struct with uint32_t alignment and no padding.
+  using NoPadding = std::array<uint32_t, 3>;
+  EXPECT_EQ(sizeof(NoPadding), sizeof(absl::Duration));
+  EXPECT_EQ(alignof(NoPadding), alignof(absl::Duration));
+}
+
 }  // namespace
diff --git a/absl/time/internal/cctz/BUILD.bazel b/absl/time/internal/cctz/BUILD.bazel
index edeabd81..4c5ad075 100644
--- a/absl/time/internal/cctz/BUILD.bazel
+++ b/absl/time/internal/cctz/BUILD.bazel
@@ -53,10 +53,11 @@ cc_library(
         "include/cctz/time_zone.h",
         "include/cctz/zone_info_source.h",
     ],
-    # OS X and iOS no longer use `linkopts = ["-framework CoreFoundation"]`
-    # as (1) bazel adds it automatically, and (2) it caused problems when
-    # cross-compiling for Android.
-    # See https://github.com/abseil/abseil-cpp/issues/326 for details.
+    linkopts = select({
+        "@platforms//os:osx": ["-Wl,-framework,CoreFoundation"],
+        "@platforms//os:ios": ["-Wl,-framework,CoreFoundation"],
+        "//conditions:default": [],
+    }),
     visibility = ["//visibility:public"],
     deps = [
         ":civil_time",
diff --git a/absl/time/internal/cctz/include/cctz/time_zone.h b/absl/time/internal/cctz/include/cctz/time_zone.h
index 6e382dc6..b2b0cf6f 100644
--- a/absl/time/internal/cctz/include/cctz/time_zone.h
+++ b/absl/time/internal/cctz/include/cctz/time_zone.h
@@ -23,6 +23,7 @@
 #include <chrono>
 #include <cstdint>
 #include <limits>
+#include <ratio>  // NOLINT: We use std::ratio in this header
 #include <string>
 #include <utility>
 
diff --git a/absl/time/internal/cctz/src/time_zone_fixed.cc b/absl/time/internal/cctz/src/time_zone_fixed.cc
index f2b3294e..e09654ea 100644
--- a/absl/time/internal/cctz/src/time_zone_fixed.cc
+++ b/absl/time/internal/cctz/src/time_zone_fixed.cc
@@ -105,7 +105,7 @@ std::string FixedOffsetToName(const seconds& offset) {
   offset_minutes %= 60;
   const std::size_t prefix_len = sizeof(kFixedZonePrefix) - 1;
   char buf[prefix_len + sizeof("-24:00:00")];
-  char* ep = std::copy(kFixedZonePrefix, kFixedZonePrefix + prefix_len, buf);
+  char* ep = std::copy_n(kFixedZonePrefix, prefix_len, buf);
   *ep++ = sign;
   ep = Format02d(ep, offset_hours);
   *ep++ = ':';
diff --git a/absl/time/internal/cctz/src/time_zone_format.cc b/absl/time/internal/cctz/src/time_zone_format.cc
index 2e5f5329..9b91f61c 100644
--- a/absl/time/internal/cctz/src/time_zone_format.cc
+++ b/absl/time/internal/cctz/src/time_zone_format.cc
@@ -13,14 +13,14 @@
 //   limitations under the License.
 
 #if !defined(HAS_STRPTIME)
-#if !defined(_MSC_VER) && !defined(__MINGW32__)
-#define HAS_STRPTIME 1  // assume everyone has strptime() except windows
+#if !defined(_MSC_VER) && !defined(__MINGW32__) && !defined(__VXWORKS__)
+#define HAS_STRPTIME 1  // Assume everyone else has strptime().
 #endif
 #endif
 
 #if defined(HAS_STRPTIME) && HAS_STRPTIME
 #if !defined(_XOPEN_SOURCE) && !defined(__OpenBSD__)
-#define _XOPEN_SOURCE  // Definedness suffices for strptime.
+#define _XOPEN_SOURCE 500  // Exposes definitions for SUSv2 (UNIX 98).
 #endif
 #endif
 
diff --git a/absl/time/internal/cctz/src/time_zone_format_test.cc b/absl/time/internal/cctz/src/time_zone_format_test.cc
index f1f79a20..4a6c71f1 100644
--- a/absl/time/internal/cctz/src/time_zone_format_test.cc
+++ b/absl/time/internal/cctz/src/time_zone_format_test.cc
@@ -64,10 +64,13 @@ const char RFC1123_no_wday[] = "%d %b %Y %H:%M:%S %z";
 template <typename D>
 void TestFormatSpecifier(time_point<D> tp, time_zone tz, const std::string& fmt,
                          const std::string& ans) {
-  EXPECT_EQ(ans, format(fmt, tp, tz)) << fmt;
-  EXPECT_EQ("xxx " + ans, format("xxx " + fmt, tp, tz));
-  EXPECT_EQ(ans + " yyy", format(fmt + " yyy", tp, tz));
-  EXPECT_EQ("xxx " + ans + " yyy", format("xxx " + fmt + " yyy", tp, tz));
+  EXPECT_EQ(ans, absl::time_internal::cctz::format(fmt, tp, tz)) << fmt;
+  EXPECT_EQ("xxx " + ans,
+            absl::time_internal::cctz::format("xxx " + fmt, tp, tz));
+  EXPECT_EQ(ans + " yyy",
+            absl::time_internal::cctz::format(fmt + " yyy", tp, tz));
+  EXPECT_EQ("xxx " + ans + " yyy",
+            absl::time_internal::cctz::format("xxx " + fmt + " yyy", tp, tz));
 }
 
 }  // namespace
@@ -83,26 +86,29 @@ TEST(Format, TimePointResolution) {
       chrono::system_clock::from_time_t(1420167845) +
       chrono::milliseconds(123) + chrono::microseconds(456) +
       chrono::nanoseconds(789);
-  EXPECT_EQ(
-      "03:04:05.123456789",
-      format(kFmt, chrono::time_point_cast<chrono::nanoseconds>(t0), utc));
-  EXPECT_EQ(
-      "03:04:05.123456",
-      format(kFmt, chrono::time_point_cast<chrono::microseconds>(t0), utc));
-  EXPECT_EQ(
-      "03:04:05.123",
-      format(kFmt, chrono::time_point_cast<chrono::milliseconds>(t0), utc));
+  EXPECT_EQ("03:04:05.123456789",
+            absl::time_internal::cctz::format(
+                kFmt, chrono::time_point_cast<chrono::nanoseconds>(t0), utc));
+  EXPECT_EQ("03:04:05.123456",
+            absl::time_internal::cctz::format(
+                kFmt, chrono::time_point_cast<chrono::microseconds>(t0), utc));
+  EXPECT_EQ("03:04:05.123",
+            absl::time_internal::cctz::format(
+                kFmt, chrono::time_point_cast<chrono::milliseconds>(t0), utc));
   EXPECT_EQ("03:04:05",
-            format(kFmt, chrono::time_point_cast<chrono::seconds>(t0), utc));
+            absl::time_internal::cctz::format(
+                kFmt, chrono::time_point_cast<chrono::seconds>(t0), utc));
   EXPECT_EQ(
       "03:04:05",
-      format(kFmt,
-             chrono::time_point_cast<absl::time_internal::cctz::seconds>(t0),
-             utc));
+      absl::time_internal::cctz::format(
+          kFmt, chrono::time_point_cast<absl::time_internal::cctz::seconds>(t0),
+          utc));
   EXPECT_EQ("03:04:00",
-            format(kFmt, chrono::time_point_cast<chrono::minutes>(t0), utc));
+            absl::time_internal::cctz::format(
+                kFmt, chrono::time_point_cast<chrono::minutes>(t0), utc));
   EXPECT_EQ("03:00:00",
-            format(kFmt, chrono::time_point_cast<chrono::hours>(t0), utc));
+            absl::time_internal::cctz::format(
+                kFmt, chrono::time_point_cast<chrono::hours>(t0), utc));
 }
 
 TEST(Format, TimePointExtendedResolution) {
@@ -137,24 +143,28 @@ TEST(Format, Basics) {
   time_point<chrono::nanoseconds> tp = chrono::system_clock::from_time_t(0);
 
   // Starts with a couple basic edge cases.
-  EXPECT_EQ("", format("", tp, tz));
-  EXPECT_EQ(" ", format(" ", tp, tz));
-  EXPECT_EQ("  ", format("  ", tp, tz));
-  EXPECT_EQ("xxx", format("xxx", tp, tz));
+  EXPECT_EQ("", absl::time_internal::cctz::format("", tp, tz));
+  EXPECT_EQ(" ", absl::time_internal::cctz::format(" ", tp, tz));
+  EXPECT_EQ("  ", absl::time_internal::cctz::format("  ", tp, tz));
+  EXPECT_EQ("xxx", absl::time_internal::cctz::format("xxx", tp, tz));
   std::string big(128, 'x');
-  EXPECT_EQ(big, format(big, tp, tz));
+  EXPECT_EQ(big, absl::time_internal::cctz::format(big, tp, tz));
   // Cause the 1024-byte buffer to grow.
   std::string bigger(100000, 'x');
-  EXPECT_EQ(bigger, format(bigger, tp, tz));
+  EXPECT_EQ(bigger, absl::time_internal::cctz::format(bigger, tp, tz));
 
   tp += chrono::hours(13) + chrono::minutes(4) + chrono::seconds(5);
   tp += chrono::milliseconds(6) + chrono::microseconds(7) +
         chrono::nanoseconds(8);
-  EXPECT_EQ("1970-01-01", format("%Y-%m-%d", tp, tz));
-  EXPECT_EQ("13:04:05", format("%H:%M:%S", tp, tz));
-  EXPECT_EQ("13:04:05.006", format("%H:%M:%E3S", tp, tz));
-  EXPECT_EQ("13:04:05.006007", format("%H:%M:%E6S", tp, tz));
-  EXPECT_EQ("13:04:05.006007008", format("%H:%M:%E9S", tp, tz));
+  EXPECT_EQ("1970-01-01",
+            absl::time_internal::cctz::format("%Y-%m-%d", tp, tz));
+  EXPECT_EQ("13:04:05", absl::time_internal::cctz::format("%H:%M:%S", tp, tz));
+  EXPECT_EQ("13:04:05.006",
+            absl::time_internal::cctz::format("%H:%M:%E3S", tp, tz));
+  EXPECT_EQ("13:04:05.006007",
+            absl::time_internal::cctz::format("%H:%M:%E6S", tp, tz));
+  EXPECT_EQ("13:04:05.006007008",
+            absl::time_internal::cctz::format("%H:%M:%E9S", tp, tz));
 }
 
 TEST(Format, PosixConversions) {
@@ -211,7 +221,8 @@ TEST(Format, LocaleSpecific) {
   TestFormatSpecifier(tp, tz, "%B", "January");
 
   // %c should at least produce the numeric year and time-of-day.
-  const std::string s = format("%c", tp, utc_time_zone());
+  const std::string s =
+      absl::time_internal::cctz::format("%c", tp, utc_time_zone());
   EXPECT_THAT(s, testing::HasSubstr("1970"));
   EXPECT_THAT(s, testing::HasSubstr("00:00:00"));
 
@@ -277,49 +288,61 @@ TEST(Format, ExtendedSeconds) {
   // No subseconds.
   time_point<chrono::nanoseconds> tp = chrono::system_clock::from_time_t(0);
   tp += chrono::seconds(5);
-  EXPECT_EQ("05", format("%E*S", tp, tz));
-  EXPECT_EQ("05", format("%E0S", tp, tz));
-  EXPECT_EQ("05.0", format("%E1S", tp, tz));
-  EXPECT_EQ("05.00", format("%E2S", tp, tz));
-  EXPECT_EQ("05.000", format("%E3S", tp, tz));
-  EXPECT_EQ("05.0000", format("%E4S", tp, tz));
-  EXPECT_EQ("05.00000", format("%E5S", tp, tz));
-  EXPECT_EQ("05.000000", format("%E6S", tp, tz));
-  EXPECT_EQ("05.0000000", format("%E7S", tp, tz));
-  EXPECT_EQ("05.00000000", format("%E8S", tp, tz));
-  EXPECT_EQ("05.000000000", format("%E9S", tp, tz));
-  EXPECT_EQ("05.0000000000", format("%E10S", tp, tz));
-  EXPECT_EQ("05.00000000000", format("%E11S", tp, tz));
-  EXPECT_EQ("05.000000000000", format("%E12S", tp, tz));
-  EXPECT_EQ("05.0000000000000", format("%E13S", tp, tz));
-  EXPECT_EQ("05.00000000000000", format("%E14S", tp, tz));
-  EXPECT_EQ("05.000000000000000", format("%E15S", tp, tz));
+  EXPECT_EQ("05", absl::time_internal::cctz::format("%E*S", tp, tz));
+  EXPECT_EQ("05", absl::time_internal::cctz::format("%E0S", tp, tz));
+  EXPECT_EQ("05.0", absl::time_internal::cctz::format("%E1S", tp, tz));
+  EXPECT_EQ("05.00", absl::time_internal::cctz::format("%E2S", tp, tz));
+  EXPECT_EQ("05.000", absl::time_internal::cctz::format("%E3S", tp, tz));
+  EXPECT_EQ("05.0000", absl::time_internal::cctz::format("%E4S", tp, tz));
+  EXPECT_EQ("05.00000", absl::time_internal::cctz::format("%E5S", tp, tz));
+  EXPECT_EQ("05.000000", absl::time_internal::cctz::format("%E6S", tp, tz));
+  EXPECT_EQ("05.0000000", absl::time_internal::cctz::format("%E7S", tp, tz));
+  EXPECT_EQ("05.00000000", absl::time_internal::cctz::format("%E8S", tp, tz));
+  EXPECT_EQ("05.000000000", absl::time_internal::cctz::format("%E9S", tp, tz));
+  EXPECT_EQ("05.0000000000",
+            absl::time_internal::cctz::format("%E10S", tp, tz));
+  EXPECT_EQ("05.00000000000",
+            absl::time_internal::cctz::format("%E11S", tp, tz));
+  EXPECT_EQ("05.000000000000",
+            absl::time_internal::cctz::format("%E12S", tp, tz));
+  EXPECT_EQ("05.0000000000000",
+            absl::time_internal::cctz::format("%E13S", tp, tz));
+  EXPECT_EQ("05.00000000000000",
+            absl::time_internal::cctz::format("%E14S", tp, tz));
+  EXPECT_EQ("05.000000000000000",
+            absl::time_internal::cctz::format("%E15S", tp, tz));
 
   // With subseconds.
   tp += chrono::milliseconds(6) + chrono::microseconds(7) +
         chrono::nanoseconds(8);
-  EXPECT_EQ("05.006007008", format("%E*S", tp, tz));
-  EXPECT_EQ("05", format("%E0S", tp, tz));
-  EXPECT_EQ("05.0", format("%E1S", tp, tz));
-  EXPECT_EQ("05.00", format("%E2S", tp, tz));
-  EXPECT_EQ("05.006", format("%E3S", tp, tz));
-  EXPECT_EQ("05.0060", format("%E4S", tp, tz));
-  EXPECT_EQ("05.00600", format("%E5S", tp, tz));
-  EXPECT_EQ("05.006007", format("%E6S", tp, tz));
-  EXPECT_EQ("05.0060070", format("%E7S", tp, tz));
-  EXPECT_EQ("05.00600700", format("%E8S", tp, tz));
-  EXPECT_EQ("05.006007008", format("%E9S", tp, tz));
-  EXPECT_EQ("05.0060070080", format("%E10S", tp, tz));
-  EXPECT_EQ("05.00600700800", format("%E11S", tp, tz));
-  EXPECT_EQ("05.006007008000", format("%E12S", tp, tz));
-  EXPECT_EQ("05.0060070080000", format("%E13S", tp, tz));
-  EXPECT_EQ("05.00600700800000", format("%E14S", tp, tz));
-  EXPECT_EQ("05.006007008000000", format("%E15S", tp, tz));
+  EXPECT_EQ("05.006007008", absl::time_internal::cctz::format("%E*S", tp, tz));
+  EXPECT_EQ("05", absl::time_internal::cctz::format("%E0S", tp, tz));
+  EXPECT_EQ("05.0", absl::time_internal::cctz::format("%E1S", tp, tz));
+  EXPECT_EQ("05.00", absl::time_internal::cctz::format("%E2S", tp, tz));
+  EXPECT_EQ("05.006", absl::time_internal::cctz::format("%E3S", tp, tz));
+  EXPECT_EQ("05.0060", absl::time_internal::cctz::format("%E4S", tp, tz));
+  EXPECT_EQ("05.00600", absl::time_internal::cctz::format("%E5S", tp, tz));
+  EXPECT_EQ("05.006007", absl::time_internal::cctz::format("%E6S", tp, tz));
+  EXPECT_EQ("05.0060070", absl::time_internal::cctz::format("%E7S", tp, tz));
+  EXPECT_EQ("05.00600700", absl::time_internal::cctz::format("%E8S", tp, tz));
+  EXPECT_EQ("05.006007008", absl::time_internal::cctz::format("%E9S", tp, tz));
+  EXPECT_EQ("05.0060070080",
+            absl::time_internal::cctz::format("%E10S", tp, tz));
+  EXPECT_EQ("05.00600700800",
+            absl::time_internal::cctz::format("%E11S", tp, tz));
+  EXPECT_EQ("05.006007008000",
+            absl::time_internal::cctz::format("%E12S", tp, tz));
+  EXPECT_EQ("05.0060070080000",
+            absl::time_internal::cctz::format("%E13S", tp, tz));
+  EXPECT_EQ("05.00600700800000",
+            absl::time_internal::cctz::format("%E14S", tp, tz));
+  EXPECT_EQ("05.006007008000000",
+            absl::time_internal::cctz::format("%E15S", tp, tz));
 
   // Times before the Unix epoch.
   tp = chrono::system_clock::from_time_t(0) + chrono::microseconds(-1);
   EXPECT_EQ("1969-12-31 23:59:59.999999",
-            format("%Y-%m-%d %H:%M:%E*S", tp, tz));
+            absl::time_internal::cctz::format("%Y-%m-%d %H:%M:%E*S", tp, tz));
 
   // Here is a "%E*S" case we got wrong for a while.  While the first
   // instant below is correctly rendered as "...:07.333304", the second
@@ -327,10 +350,10 @@ TEST(Format, ExtendedSeconds) {
   tp = chrono::system_clock::from_time_t(0) +
        chrono::microseconds(1395024427333304);
   EXPECT_EQ("2014-03-17 02:47:07.333304",
-            format("%Y-%m-%d %H:%M:%E*S", tp, tz));
+            absl::time_internal::cctz::format("%Y-%m-%d %H:%M:%E*S", tp, tz));
   tp += chrono::microseconds(1);
   EXPECT_EQ("2014-03-17 02:47:07.333305",
-            format("%Y-%m-%d %H:%M:%E*S", tp, tz));
+            absl::time_internal::cctz::format("%Y-%m-%d %H:%M:%E*S", tp, tz));
 }
 
 TEST(Format, ExtendedSubeconds) {
@@ -339,60 +362,69 @@ TEST(Format, ExtendedSubeconds) {
   // No subseconds.
   time_point<chrono::nanoseconds> tp = chrono::system_clock::from_time_t(0);
   tp += chrono::seconds(5);
-  EXPECT_EQ("0", format("%E*f", tp, tz));
-  EXPECT_EQ("", format("%E0f", tp, tz));
-  EXPECT_EQ("0", format("%E1f", tp, tz));
-  EXPECT_EQ("00", format("%E2f", tp, tz));
-  EXPECT_EQ("000", format("%E3f", tp, tz));
-  EXPECT_EQ("0000", format("%E4f", tp, tz));
-  EXPECT_EQ("00000", format("%E5f", tp, tz));
-  EXPECT_EQ("000000", format("%E6f", tp, tz));
-  EXPECT_EQ("0000000", format("%E7f", tp, tz));
-  EXPECT_EQ("00000000", format("%E8f", tp, tz));
-  EXPECT_EQ("000000000", format("%E9f", tp, tz));
-  EXPECT_EQ("0000000000", format("%E10f", tp, tz));
-  EXPECT_EQ("00000000000", format("%E11f", tp, tz));
-  EXPECT_EQ("000000000000", format("%E12f", tp, tz));
-  EXPECT_EQ("0000000000000", format("%E13f", tp, tz));
-  EXPECT_EQ("00000000000000", format("%E14f", tp, tz));
-  EXPECT_EQ("000000000000000", format("%E15f", tp, tz));
+  EXPECT_EQ("0", absl::time_internal::cctz::format("%E*f", tp, tz));
+  EXPECT_EQ("", absl::time_internal::cctz::format("%E0f", tp, tz));
+  EXPECT_EQ("0", absl::time_internal::cctz::format("%E1f", tp, tz));
+  EXPECT_EQ("00", absl::time_internal::cctz::format("%E2f", tp, tz));
+  EXPECT_EQ("000", absl::time_internal::cctz::format("%E3f", tp, tz));
+  EXPECT_EQ("0000", absl::time_internal::cctz::format("%E4f", tp, tz));
+  EXPECT_EQ("00000", absl::time_internal::cctz::format("%E5f", tp, tz));
+  EXPECT_EQ("000000", absl::time_internal::cctz::format("%E6f", tp, tz));
+  EXPECT_EQ("0000000", absl::time_internal::cctz::format("%E7f", tp, tz));
+  EXPECT_EQ("00000000", absl::time_internal::cctz::format("%E8f", tp, tz));
+  EXPECT_EQ("000000000", absl::time_internal::cctz::format("%E9f", tp, tz));
+  EXPECT_EQ("0000000000", absl::time_internal::cctz::format("%E10f", tp, tz));
+  EXPECT_EQ("00000000000", absl::time_internal::cctz::format("%E11f", tp, tz));
+  EXPECT_EQ("000000000000", absl::time_internal::cctz::format("%E12f", tp, tz));
+  EXPECT_EQ("0000000000000",
+            absl::time_internal::cctz::format("%E13f", tp, tz));
+  EXPECT_EQ("00000000000000",
+            absl::time_internal::cctz::format("%E14f", tp, tz));
+  EXPECT_EQ("000000000000000",
+            absl::time_internal::cctz::format("%E15f", tp, tz));
 
   // With subseconds.
   tp += chrono::milliseconds(6) + chrono::microseconds(7) +
         chrono::nanoseconds(8);
-  EXPECT_EQ("006007008", format("%E*f", tp, tz));
-  EXPECT_EQ("", format("%E0f", tp, tz));
-  EXPECT_EQ("0", format("%E1f", tp, tz));
-  EXPECT_EQ("00", format("%E2f", tp, tz));
-  EXPECT_EQ("006", format("%E3f", tp, tz));
-  EXPECT_EQ("0060", format("%E4f", tp, tz));
-  EXPECT_EQ("00600", format("%E5f", tp, tz));
-  EXPECT_EQ("006007", format("%E6f", tp, tz));
-  EXPECT_EQ("0060070", format("%E7f", tp, tz));
-  EXPECT_EQ("00600700", format("%E8f", tp, tz));
-  EXPECT_EQ("006007008", format("%E9f", tp, tz));
-  EXPECT_EQ("0060070080", format("%E10f", tp, tz));
-  EXPECT_EQ("00600700800", format("%E11f", tp, tz));
-  EXPECT_EQ("006007008000", format("%E12f", tp, tz));
-  EXPECT_EQ("0060070080000", format("%E13f", tp, tz));
-  EXPECT_EQ("00600700800000", format("%E14f", tp, tz));
-  EXPECT_EQ("006007008000000", format("%E15f", tp, tz));
+  EXPECT_EQ("006007008", absl::time_internal::cctz::format("%E*f", tp, tz));
+  EXPECT_EQ("", absl::time_internal::cctz::format("%E0f", tp, tz));
+  EXPECT_EQ("0", absl::time_internal::cctz::format("%E1f", tp, tz));
+  EXPECT_EQ("00", absl::time_internal::cctz::format("%E2f", tp, tz));
+  EXPECT_EQ("006", absl::time_internal::cctz::format("%E3f", tp, tz));
+  EXPECT_EQ("0060", absl::time_internal::cctz::format("%E4f", tp, tz));
+  EXPECT_EQ("00600", absl::time_internal::cctz::format("%E5f", tp, tz));
+  EXPECT_EQ("006007", absl::time_internal::cctz::format("%E6f", tp, tz));
+  EXPECT_EQ("0060070", absl::time_internal::cctz::format("%E7f", tp, tz));
+  EXPECT_EQ("00600700", absl::time_internal::cctz::format("%E8f", tp, tz));
+  EXPECT_EQ("006007008", absl::time_internal::cctz::format("%E9f", tp, tz));
+  EXPECT_EQ("0060070080", absl::time_internal::cctz::format("%E10f", tp, tz));
+  EXPECT_EQ("00600700800", absl::time_internal::cctz::format("%E11f", tp, tz));
+  EXPECT_EQ("006007008000", absl::time_internal::cctz::format("%E12f", tp, tz));
+  EXPECT_EQ("0060070080000",
+            absl::time_internal::cctz::format("%E13f", tp, tz));
+  EXPECT_EQ("00600700800000",
+            absl::time_internal::cctz::format("%E14f", tp, tz));
+  EXPECT_EQ("006007008000000",
+            absl::time_internal::cctz::format("%E15f", tp, tz));
 
   // Times before the Unix epoch.
   tp = chrono::system_clock::from_time_t(0) + chrono::microseconds(-1);
-  EXPECT_EQ("1969-12-31 23:59:59.999999",
-            format("%Y-%m-%d %H:%M:%S.%E*f", tp, tz));
+  EXPECT_EQ(
+      "1969-12-31 23:59:59.999999",
+      absl::time_internal::cctz::format("%Y-%m-%d %H:%M:%S.%E*f", tp, tz));
 
   // Here is a "%E*S" case we got wrong for a while.  While the first
   // instant below is correctly rendered as "...:07.333304", the second
   // one used to appear as "...:07.33330499999999999".
   tp = chrono::system_clock::from_time_t(0) +
        chrono::microseconds(1395024427333304);
-  EXPECT_EQ("2014-03-17 02:47:07.333304",
-            format("%Y-%m-%d %H:%M:%S.%E*f", tp, tz));
+  EXPECT_EQ(
+      "2014-03-17 02:47:07.333304",
+      absl::time_internal::cctz::format("%Y-%m-%d %H:%M:%S.%E*f", tp, tz));
   tp += chrono::microseconds(1);
-  EXPECT_EQ("2014-03-17 02:47:07.333305",
-            format("%Y-%m-%d %H:%M:%S.%E*f", tp, tz));
+  EXPECT_EQ(
+      "2014-03-17 02:47:07.333305",
+      absl::time_internal::cctz::format("%Y-%m-%d %H:%M:%S.%E*f", tp, tz));
 }
 
 TEST(Format, CompareExtendSecondsVsSubseconds) {
@@ -408,15 +440,17 @@ TEST(Format, CompareExtendSecondsVsSubseconds) {
   time_point<chrono::nanoseconds> tp = chrono::system_clock::from_time_t(0);
   tp += chrono::seconds(5);
   // ... %E*S and %S.%E*f are different.
-  EXPECT_EQ("05", format(fmt_A("*"), tp, tz));
-  EXPECT_EQ("05.0", format(fmt_B("*"), tp, tz));
+  EXPECT_EQ("05", absl::time_internal::cctz::format(fmt_A("*"), tp, tz));
+  EXPECT_EQ("05.0", absl::time_internal::cctz::format(fmt_B("*"), tp, tz));
   // ... %E0S and %S.%E0f are different.
-  EXPECT_EQ("05", format(fmt_A("0"), tp, tz));
-  EXPECT_EQ("05.", format(fmt_B("0"), tp, tz));
+  EXPECT_EQ("05", absl::time_internal::cctz::format(fmt_A("0"), tp, tz));
+  EXPECT_EQ("05.", absl::time_internal::cctz::format(fmt_B("0"), tp, tz));
   // ... %E<prec>S and %S.%E<prec>f are the same for prec in [1:15].
   for (int prec = 1; prec <= 15; ++prec) {
-    const std::string a = format(fmt_A(std::to_string(prec)), tp, tz);
-    const std::string b = format(fmt_B(std::to_string(prec)), tp, tz);
+    const std::string a =
+        absl::time_internal::cctz::format(fmt_A(std::to_string(prec)), tp, tz);
+    const std::string b =
+        absl::time_internal::cctz::format(fmt_B(std::to_string(prec)), tp, tz);
     EXPECT_EQ(a, b) << "prec=" << prec;
   }
 
@@ -424,15 +458,19 @@ TEST(Format, CompareExtendSecondsVsSubseconds) {
   // ... %E*S and %S.%E*f are the same.
   tp += chrono::milliseconds(6) + chrono::microseconds(7) +
         chrono::nanoseconds(8);
-  EXPECT_EQ("05.006007008", format(fmt_A("*"), tp, tz));
-  EXPECT_EQ("05.006007008", format(fmt_B("*"), tp, tz));
+  EXPECT_EQ("05.006007008",
+            absl::time_internal::cctz::format(fmt_A("*"), tp, tz));
+  EXPECT_EQ("05.006007008",
+            absl::time_internal::cctz::format(fmt_B("*"), tp, tz));
   // ... %E0S and %S.%E0f are different.
-  EXPECT_EQ("05", format(fmt_A("0"), tp, tz));
-  EXPECT_EQ("05.", format(fmt_B("0"), tp, tz));
+  EXPECT_EQ("05", absl::time_internal::cctz::format(fmt_A("0"), tp, tz));
+  EXPECT_EQ("05.", absl::time_internal::cctz::format(fmt_B("0"), tp, tz));
   // ... %E<prec>S and %S.%E<prec>f are the same for prec in [1:15].
   for (int prec = 1; prec <= 15; ++prec) {
-    const std::string a = format(fmt_A(std::to_string(prec)), tp, tz);
-    const std::string b = format(fmt_B(std::to_string(prec)), tp, tz);
+    const std::string a =
+        absl::time_internal::cctz::format(fmt_A(std::to_string(prec)), tp, tz);
+    const std::string b =
+        absl::time_internal::cctz::format(fmt_B(std::to_string(prec)), tp, tz);
     EXPECT_EQ(a, b) << "prec=" << prec;
   }
 }
@@ -605,31 +643,31 @@ TEST(Format, ExtendedYears) {
 
   // %E4Y zero-pads the year to produce at least 4 chars, including the sign.
   auto tp = convert(civil_second(-999, 11, 27, 0, 0, 0), utc);
-  EXPECT_EQ("-9991127", format(e4y_fmt, tp, utc));
+  EXPECT_EQ("-9991127", absl::time_internal::cctz::format(e4y_fmt, tp, utc));
   tp = convert(civil_second(-99, 11, 27, 0, 0, 0), utc);
-  EXPECT_EQ("-0991127", format(e4y_fmt, tp, utc));
+  EXPECT_EQ("-0991127", absl::time_internal::cctz::format(e4y_fmt, tp, utc));
   tp = convert(civil_second(-9, 11, 27, 0, 0, 0), utc);
-  EXPECT_EQ("-0091127", format(e4y_fmt, tp, utc));
+  EXPECT_EQ("-0091127", absl::time_internal::cctz::format(e4y_fmt, tp, utc));
   tp = convert(civil_second(-1, 11, 27, 0, 0, 0), utc);
-  EXPECT_EQ("-0011127", format(e4y_fmt, tp, utc));
+  EXPECT_EQ("-0011127", absl::time_internal::cctz::format(e4y_fmt, tp, utc));
   tp = convert(civil_second(0, 11, 27, 0, 0, 0), utc);
-  EXPECT_EQ("00001127", format(e4y_fmt, tp, utc));
+  EXPECT_EQ("00001127", absl::time_internal::cctz::format(e4y_fmt, tp, utc));
   tp = convert(civil_second(1, 11, 27, 0, 0, 0), utc);
-  EXPECT_EQ("00011127", format(e4y_fmt, tp, utc));
+  EXPECT_EQ("00011127", absl::time_internal::cctz::format(e4y_fmt, tp, utc));
   tp = convert(civil_second(9, 11, 27, 0, 0, 0), utc);
-  EXPECT_EQ("00091127", format(e4y_fmt, tp, utc));
+  EXPECT_EQ("00091127", absl::time_internal::cctz::format(e4y_fmt, tp, utc));
   tp = convert(civil_second(99, 11, 27, 0, 0, 0), utc);
-  EXPECT_EQ("00991127", format(e4y_fmt, tp, utc));
+  EXPECT_EQ("00991127", absl::time_internal::cctz::format(e4y_fmt, tp, utc));
   tp = convert(civil_second(999, 11, 27, 0, 0, 0), utc);
-  EXPECT_EQ("09991127", format(e4y_fmt, tp, utc));
+  EXPECT_EQ("09991127", absl::time_internal::cctz::format(e4y_fmt, tp, utc));
   tp = convert(civil_second(9999, 11, 27, 0, 0, 0), utc);
-  EXPECT_EQ("99991127", format(e4y_fmt, tp, utc));
+  EXPECT_EQ("99991127", absl::time_internal::cctz::format(e4y_fmt, tp, utc));
 
   // When the year is outside [-999:9999], more than 4 chars are produced.
   tp = convert(civil_second(-1000, 11, 27, 0, 0, 0), utc);
-  EXPECT_EQ("-10001127", format(e4y_fmt, tp, utc));
+  EXPECT_EQ("-10001127", absl::time_internal::cctz::format(e4y_fmt, tp, utc));
   tp = convert(civil_second(10000, 11, 27, 0, 0, 0), utc);
-  EXPECT_EQ("100001127", format(e4y_fmt, tp, utc));
+  EXPECT_EQ("100001127", absl::time_internal::cctz::format(e4y_fmt, tp, utc));
 }
 
 TEST(Format, RFC3339Format) {
@@ -638,45 +676,64 @@ TEST(Format, RFC3339Format) {
 
   time_point<chrono::nanoseconds> tp =
       convert(civil_second(1977, 6, 28, 9, 8, 7), tz);
-  EXPECT_EQ("1977-06-28T09:08:07-07:00", format(RFC3339_full, tp, tz));
-  EXPECT_EQ("1977-06-28T09:08:07-07:00", format(RFC3339_sec, tp, tz));
+  EXPECT_EQ("1977-06-28T09:08:07-07:00",
+            absl::time_internal::cctz::format(RFC3339_full, tp, tz));
+  EXPECT_EQ("1977-06-28T09:08:07-07:00",
+            absl::time_internal::cctz::format(RFC3339_sec, tp, tz));
 
   tp += chrono::milliseconds(100);
-  EXPECT_EQ("1977-06-28T09:08:07.1-07:00", format(RFC3339_full, tp, tz));
-  EXPECT_EQ("1977-06-28T09:08:07-07:00", format(RFC3339_sec, tp, tz));
+  EXPECT_EQ("1977-06-28T09:08:07.1-07:00",
+            absl::time_internal::cctz::format(RFC3339_full, tp, tz));
+  EXPECT_EQ("1977-06-28T09:08:07-07:00",
+            absl::time_internal::cctz::format(RFC3339_sec, tp, tz));
 
   tp += chrono::milliseconds(20);
-  EXPECT_EQ("1977-06-28T09:08:07.12-07:00", format(RFC3339_full, tp, tz));
-  EXPECT_EQ("1977-06-28T09:08:07-07:00", format(RFC3339_sec, tp, tz));
+  EXPECT_EQ("1977-06-28T09:08:07.12-07:00",
+            absl::time_internal::cctz::format(RFC3339_full, tp, tz));
+  EXPECT_EQ("1977-06-28T09:08:07-07:00",
+            absl::time_internal::cctz::format(RFC3339_sec, tp, tz));
 
   tp += chrono::milliseconds(3);
-  EXPECT_EQ("1977-06-28T09:08:07.123-07:00", format(RFC3339_full, tp, tz));
-  EXPECT_EQ("1977-06-28T09:08:07-07:00", format(RFC3339_sec, tp, tz));
+  EXPECT_EQ("1977-06-28T09:08:07.123-07:00",
+            absl::time_internal::cctz::format(RFC3339_full, tp, tz));
+  EXPECT_EQ("1977-06-28T09:08:07-07:00",
+            absl::time_internal::cctz::format(RFC3339_sec, tp, tz));
 
   tp += chrono::microseconds(400);
-  EXPECT_EQ("1977-06-28T09:08:07.1234-07:00", format(RFC3339_full, tp, tz));
-  EXPECT_EQ("1977-06-28T09:08:07-07:00", format(RFC3339_sec, tp, tz));
+  EXPECT_EQ("1977-06-28T09:08:07.1234-07:00",
+            absl::time_internal::cctz::format(RFC3339_full, tp, tz));
+  EXPECT_EQ("1977-06-28T09:08:07-07:00",
+            absl::time_internal::cctz::format(RFC3339_sec, tp, tz));
 
   tp += chrono::microseconds(50);
-  EXPECT_EQ("1977-06-28T09:08:07.12345-07:00", format(RFC3339_full, tp, tz));
-  EXPECT_EQ("1977-06-28T09:08:07-07:00", format(RFC3339_sec, tp, tz));
+  EXPECT_EQ("1977-06-28T09:08:07.12345-07:00",
+            absl::time_internal::cctz::format(RFC3339_full, tp, tz));
+  EXPECT_EQ("1977-06-28T09:08:07-07:00",
+            absl::time_internal::cctz::format(RFC3339_sec, tp, tz));
 
   tp += chrono::microseconds(6);
-  EXPECT_EQ("1977-06-28T09:08:07.123456-07:00", format(RFC3339_full, tp, tz));
-  EXPECT_EQ("1977-06-28T09:08:07-07:00", format(RFC3339_sec, tp, tz));
+  EXPECT_EQ("1977-06-28T09:08:07.123456-07:00",
+            absl::time_internal::cctz::format(RFC3339_full, tp, tz));
+  EXPECT_EQ("1977-06-28T09:08:07-07:00",
+            absl::time_internal::cctz::format(RFC3339_sec, tp, tz));
 
   tp += chrono::nanoseconds(700);
-  EXPECT_EQ("1977-06-28T09:08:07.1234567-07:00", format(RFC3339_full, tp, tz));
-  EXPECT_EQ("1977-06-28T09:08:07-07:00", format(RFC3339_sec, tp, tz));
+  EXPECT_EQ("1977-06-28T09:08:07.1234567-07:00",
+            absl::time_internal::cctz::format(RFC3339_full, tp, tz));
+  EXPECT_EQ("1977-06-28T09:08:07-07:00",
+            absl::time_internal::cctz::format(RFC3339_sec, tp, tz));
 
   tp += chrono::nanoseconds(80);
-  EXPECT_EQ("1977-06-28T09:08:07.12345678-07:00", format(RFC3339_full, tp, tz));
-  EXPECT_EQ("1977-06-28T09:08:07-07:00", format(RFC3339_sec, tp, tz));
+  EXPECT_EQ("1977-06-28T09:08:07.12345678-07:00",
+            absl::time_internal::cctz::format(RFC3339_full, tp, tz));
+  EXPECT_EQ("1977-06-28T09:08:07-07:00",
+            absl::time_internal::cctz::format(RFC3339_sec, tp, tz));
 
   tp += chrono::nanoseconds(9);
   EXPECT_EQ("1977-06-28T09:08:07.123456789-07:00",
-            format(RFC3339_full, tp, tz));
-  EXPECT_EQ("1977-06-28T09:08:07-07:00", format(RFC3339_sec, tp, tz));
+            absl::time_internal::cctz::format(RFC3339_full, tp, tz));
+  EXPECT_EQ("1977-06-28T09:08:07-07:00",
+            absl::time_internal::cctz::format(RFC3339_sec, tp, tz));
 }
 
 TEST(Format, RFC1123Format) {  // locale specific
@@ -684,36 +741,50 @@ TEST(Format, RFC1123Format) {  // locale specific
   EXPECT_TRUE(load_time_zone("America/Los_Angeles", &tz));
 
   auto tp = convert(civil_second(1977, 6, 28, 9, 8, 7), tz);
-  EXPECT_EQ("Tue, 28 Jun 1977 09:08:07 -0700", format(RFC1123_full, tp, tz));
-  EXPECT_EQ("28 Jun 1977 09:08:07 -0700", format(RFC1123_no_wday, tp, tz));
+  EXPECT_EQ("Tue, 28 Jun 1977 09:08:07 -0700",
+            absl::time_internal::cctz::format(RFC1123_full, tp, tz));
+  EXPECT_EQ("28 Jun 1977 09:08:07 -0700",
+            absl::time_internal::cctz::format(RFC1123_no_wday, tp, tz));
 }
 
 TEST(Format, Week) {
   const time_zone utc = utc_time_zone();
 
   auto tp = convert(civil_second(2017, 1, 1, 0, 0, 0), utc);
-  EXPECT_EQ("2017-01-7", format("%Y-%U-%u", tp, utc));
-  EXPECT_EQ("2017-00-0", format("%Y-%W-%w", tp, utc));
+  EXPECT_EQ("2017-01-7",
+            absl::time_internal::cctz::format("%Y-%U-%u", tp, utc));
+  EXPECT_EQ("2017-00-0",
+            absl::time_internal::cctz::format("%Y-%W-%w", tp, utc));
 
   tp = convert(civil_second(2017, 12, 31, 0, 0, 0), utc);
-  EXPECT_EQ("2017-53-7", format("%Y-%U-%u", tp, utc));
-  EXPECT_EQ("2017-52-0", format("%Y-%W-%w", tp, utc));
+  EXPECT_EQ("2017-53-7",
+            absl::time_internal::cctz::format("%Y-%U-%u", tp, utc));
+  EXPECT_EQ("2017-52-0",
+            absl::time_internal::cctz::format("%Y-%W-%w", tp, utc));
 
   tp = convert(civil_second(2018, 1, 1, 0, 0, 0), utc);
-  EXPECT_EQ("2018-00-1", format("%Y-%U-%u", tp, utc));
-  EXPECT_EQ("2018-01-1", format("%Y-%W-%w", tp, utc));
+  EXPECT_EQ("2018-00-1",
+            absl::time_internal::cctz::format("%Y-%U-%u", tp, utc));
+  EXPECT_EQ("2018-01-1",
+            absl::time_internal::cctz::format("%Y-%W-%w", tp, utc));
 
   tp = convert(civil_second(2018, 12, 31, 0, 0, 0), utc);
-  EXPECT_EQ("2018-52-1", format("%Y-%U-%u", tp, utc));
-  EXPECT_EQ("2018-53-1", format("%Y-%W-%w", tp, utc));
+  EXPECT_EQ("2018-52-1",
+            absl::time_internal::cctz::format("%Y-%U-%u", tp, utc));
+  EXPECT_EQ("2018-53-1",
+            absl::time_internal::cctz::format("%Y-%W-%w", tp, utc));
 
   tp = convert(civil_second(2019, 1, 1, 0, 0, 0), utc);
-  EXPECT_EQ("2019-00-2", format("%Y-%U-%u", tp, utc));
-  EXPECT_EQ("2019-00-2", format("%Y-%W-%w", tp, utc));
+  EXPECT_EQ("2019-00-2",
+            absl::time_internal::cctz::format("%Y-%U-%u", tp, utc));
+  EXPECT_EQ("2019-00-2",
+            absl::time_internal::cctz::format("%Y-%W-%w", tp, utc));
 
   tp = convert(civil_second(2019, 12, 31, 0, 0, 0), utc);
-  EXPECT_EQ("2019-52-2", format("%Y-%U-%u", tp, utc));
-  EXPECT_EQ("2019-52-2", format("%Y-%W-%w", tp, utc));
+  EXPECT_EQ("2019-52-2",
+            absl::time_internal::cctz::format("%Y-%U-%u", tp, utc));
+  EXPECT_EQ("2019-52-2",
+            absl::time_internal::cctz::format("%Y-%W-%w", tp, utc));
 }
 
 //
@@ -726,39 +797,46 @@ TEST(Parse, TimePointResolution) {
 
   time_point<chrono::nanoseconds> tp_ns;
   EXPECT_TRUE(parse(kFmt, "03:04:05.123456789", utc, &tp_ns));
-  EXPECT_EQ("03:04:05.123456789", format(kFmt, tp_ns, utc));
+  EXPECT_EQ("03:04:05.123456789",
+            absl::time_internal::cctz::format(kFmt, tp_ns, utc));
   EXPECT_TRUE(parse(kFmt, "03:04:05.123456", utc, &tp_ns));
-  EXPECT_EQ("03:04:05.123456", format(kFmt, tp_ns, utc));
+  EXPECT_EQ("03:04:05.123456",
+            absl::time_internal::cctz::format(kFmt, tp_ns, utc));
 
   time_point<chrono::microseconds> tp_us;
   EXPECT_TRUE(parse(kFmt, "03:04:05.123456789", utc, &tp_us));
-  EXPECT_EQ("03:04:05.123456", format(kFmt, tp_us, utc));
+  EXPECT_EQ("03:04:05.123456",
+            absl::time_internal::cctz::format(kFmt, tp_us, utc));
   EXPECT_TRUE(parse(kFmt, "03:04:05.123456", utc, &tp_us));
-  EXPECT_EQ("03:04:05.123456", format(kFmt, tp_us, utc));
+  EXPECT_EQ("03:04:05.123456",
+            absl::time_internal::cctz::format(kFmt, tp_us, utc));
   EXPECT_TRUE(parse(kFmt, "03:04:05.123", utc, &tp_us));
-  EXPECT_EQ("03:04:05.123", format(kFmt, tp_us, utc));
+  EXPECT_EQ("03:04:05.123",
+            absl::time_internal::cctz::format(kFmt, tp_us, utc));
 
   time_point<chrono::milliseconds> tp_ms;
   EXPECT_TRUE(parse(kFmt, "03:04:05.123456", utc, &tp_ms));
-  EXPECT_EQ("03:04:05.123", format(kFmt, tp_ms, utc));
+  EXPECT_EQ("03:04:05.123",
+            absl::time_internal::cctz::format(kFmt, tp_ms, utc));
   EXPECT_TRUE(parse(kFmt, "03:04:05.123", utc, &tp_ms));
-  EXPECT_EQ("03:04:05.123", format(kFmt, tp_ms, utc));
+  EXPECT_EQ("03:04:05.123",
+            absl::time_internal::cctz::format(kFmt, tp_ms, utc));
   EXPECT_TRUE(parse(kFmt, "03:04:05", utc, &tp_ms));
-  EXPECT_EQ("03:04:05", format(kFmt, tp_ms, utc));
+  EXPECT_EQ("03:04:05", absl::time_internal::cctz::format(kFmt, tp_ms, utc));
 
   time_point<chrono::seconds> tp_s;
   EXPECT_TRUE(parse(kFmt, "03:04:05.123", utc, &tp_s));
-  EXPECT_EQ("03:04:05", format(kFmt, tp_s, utc));
+  EXPECT_EQ("03:04:05", absl::time_internal::cctz::format(kFmt, tp_s, utc));
   EXPECT_TRUE(parse(kFmt, "03:04:05", utc, &tp_s));
-  EXPECT_EQ("03:04:05", format(kFmt, tp_s, utc));
+  EXPECT_EQ("03:04:05", absl::time_internal::cctz::format(kFmt, tp_s, utc));
 
   time_point<chrono::minutes> tp_m;
   EXPECT_TRUE(parse(kFmt, "03:04:05", utc, &tp_m));
-  EXPECT_EQ("03:04:00", format(kFmt, tp_m, utc));
+  EXPECT_EQ("03:04:00", absl::time_internal::cctz::format(kFmt, tp_m, utc));
 
   time_point<chrono::hours> tp_h;
   EXPECT_TRUE(parse(kFmt, "03:04:05", utc, &tp_h));
-  EXPECT_EQ("03:00:00", format(kFmt, tp_h, utc));
+  EXPECT_EQ("03:00:00", absl::time_internal::cctz::format(kFmt, tp_h, utc));
 }
 
 TEST(Parse, TimePointExtendedResolution) {
@@ -1550,7 +1628,7 @@ TEST(Parse, TimePointOverflow) {
       parse(RFC3339_full, "2262-04-11T23:47:16.8547758079+00:00", utc, &tp));
   EXPECT_EQ(tp, time_point<D>::max());
   EXPECT_EQ("2262-04-11T23:47:16.854775807+00:00",
-            format(RFC3339_full, tp, utc));
+            absl::time_internal::cctz::format(RFC3339_full, tp, utc));
 #if 0
   // TODO(#199): Will fail until cctz::parse() properly detects overflow.
   EXPECT_FALSE(
@@ -1559,7 +1637,7 @@ TEST(Parse, TimePointOverflow) {
       parse(RFC3339_full, "1677-09-21T00:12:43.1452241920+00:00", utc, &tp));
   EXPECT_EQ(tp, time_point<D>::min());
   EXPECT_EQ("1677-09-21T00:12:43.145224192+00:00",
-            format(RFC3339_full, tp, utc));
+            absl::time_internal::cctz::format(RFC3339_full, tp, utc));
   EXPECT_FALSE(
       parse(RFC3339_full, "1677-09-21T00:12:43.1452241919+00:00", utc, &tp));
 #endif
@@ -1569,12 +1647,14 @@ TEST(Parse, TimePointOverflow) {
 
   EXPECT_TRUE(parse(RFC3339_full, "1970-01-01T00:02:07.9+00:00", utc, &stp));
   EXPECT_EQ(stp, time_point<DS>::max());
-  EXPECT_EQ("1970-01-01T00:02:07+00:00", format(RFC3339_full, stp, utc));
+  EXPECT_EQ("1970-01-01T00:02:07+00:00",
+            absl::time_internal::cctz::format(RFC3339_full, stp, utc));
   EXPECT_FALSE(parse(RFC3339_full, "1970-01-01T00:02:08+00:00", utc, &stp));
 
   EXPECT_TRUE(parse(RFC3339_full, "1969-12-31T23:57:52+00:00", utc, &stp));
   EXPECT_EQ(stp, time_point<DS>::min());
-  EXPECT_EQ("1969-12-31T23:57:52+00:00", format(RFC3339_full, stp, utc));
+  EXPECT_EQ("1969-12-31T23:57:52+00:00",
+            absl::time_internal::cctz::format(RFC3339_full, stp, utc));
   EXPECT_FALSE(parse(RFC3339_full, "1969-12-31T23:57:51.9+00:00", utc, &stp));
 
   using DM = chrono::duration<std::int8_t, chrono::minutes::period>;
@@ -1582,12 +1662,14 @@ TEST(Parse, TimePointOverflow) {
 
   EXPECT_TRUE(parse(RFC3339_full, "1970-01-01T02:07:59+00:00", utc, &mtp));
   EXPECT_EQ(mtp, time_point<DM>::max());
-  EXPECT_EQ("1970-01-01T02:07:00+00:00", format(RFC3339_full, mtp, utc));
+  EXPECT_EQ("1970-01-01T02:07:00+00:00",
+            absl::time_internal::cctz::format(RFC3339_full, mtp, utc));
   EXPECT_FALSE(parse(RFC3339_full, "1970-01-01T02:08:00+00:00", utc, &mtp));
 
   EXPECT_TRUE(parse(RFC3339_full, "1969-12-31T21:52:00+00:00", utc, &mtp));
   EXPECT_EQ(mtp, time_point<DM>::min());
-  EXPECT_EQ("1969-12-31T21:52:00+00:00", format(RFC3339_full, mtp, utc));
+  EXPECT_EQ("1969-12-31T21:52:00+00:00",
+            absl::time_internal::cctz::format(RFC3339_full, mtp, utc));
   EXPECT_FALSE(parse(RFC3339_full, "1969-12-31T21:51:59+00:00", utc, &mtp));
 }
 
@@ -1601,7 +1683,7 @@ TEST(Parse, TimePointOverflowFloor) {
       parse(RFC3339_full, "294247-01-10T04:00:54.7758079+00:00", utc, &tp));
   EXPECT_EQ(tp, time_point<D>::max());
   EXPECT_EQ("294247-01-10T04:00:54.775807+00:00",
-            format(RFC3339_full, tp, utc));
+            absl::time_internal::cctz::format(RFC3339_full, tp, utc));
 #if 0
   // TODO(#199): Will fail until cctz::parse() properly detects overflow.
   EXPECT_FALSE(
@@ -1610,7 +1692,7 @@ TEST(Parse, TimePointOverflowFloor) {
       parse(RFC3339_full, "-290308-12-21T19:59:05.2241920+00:00", utc, &tp));
   EXPECT_EQ(tp, time_point<D>::min());
   EXPECT_EQ("-290308-12-21T19:59:05.224192+00:00",
-            format(RFC3339_full, tp, utc));
+            absl::time_internal::cctz::format(RFC3339_full, tp, utc));
   EXPECT_FALSE(
       parse(RFC3339_full, "-290308-12-21T19:59:05.2241919+00:00", utc, &tp));
 #endif
@@ -1629,7 +1711,8 @@ TEST(FormatParse, RoundTrip) {
   // RFC3339, which renders subseconds.
   {
     time_point<chrono::nanoseconds> out;
-    const std::string s = format(RFC3339_full, in + subseconds, lax);
+    const std::string s =
+        absl::time_internal::cctz::format(RFC3339_full, in + subseconds, lax);
     EXPECT_TRUE(parse(RFC3339_full, s, lax, &out)) << s;
     EXPECT_EQ(in + subseconds, out);  // RFC3339_full includes %Ez
   }
@@ -1637,7 +1720,8 @@ TEST(FormatParse, RoundTrip) {
   // RFC1123, which only does whole seconds.
   {
     time_point<chrono::nanoseconds> out;
-    const std::string s = format(RFC1123_full, in, lax);
+    const std::string s =
+        absl::time_internal::cctz::format(RFC1123_full, in, lax);
     EXPECT_TRUE(parse(RFC1123_full, s, lax, &out)) << s;
     EXPECT_EQ(in, out);  // RFC1123_full includes %z
   }
@@ -1655,7 +1739,7 @@ TEST(FormatParse, RoundTrip) {
   {
     time_point<chrono::nanoseconds> out;
     time_zone utc = utc_time_zone();
-    const std::string s = format("%c", in, utc);
+    const std::string s = absl::time_internal::cctz::format("%c", in, utc);
     EXPECT_TRUE(parse("%c", s, utc, &out)) << s;
     EXPECT_EQ(in, out);
   }
@@ -1666,7 +1750,8 @@ TEST(FormatParse, RoundTripDistantFuture) {
   const time_zone utc = utc_time_zone();
   const time_point<absl::time_internal::cctz::seconds> in =
       time_point<absl::time_internal::cctz::seconds>::max();
-  const std::string s = format(RFC3339_full, in, utc);
+  const std::string s =
+      absl::time_internal::cctz::format(RFC3339_full, in, utc);
   time_point<absl::time_internal::cctz::seconds> out;
   EXPECT_TRUE(parse(RFC3339_full, s, utc, &out)) << s;
   EXPECT_EQ(in, out);
@@ -1676,7 +1761,8 @@ TEST(FormatParse, RoundTripDistantPast) {
   const time_zone utc = utc_time_zone();
   const time_point<absl::time_internal::cctz::seconds> in =
       time_point<absl::time_internal::cctz::seconds>::min();
-  const std::string s = format(RFC3339_full, in, utc);
+  const std::string s =
+      absl::time_internal::cctz::format(RFC3339_full, in, utc);
   time_point<absl::time_internal::cctz::seconds> out;
   EXPECT_TRUE(parse(RFC3339_full, s, utc, &out)) << s;
   EXPECT_EQ(in, out);
diff --git a/absl/time/internal/cctz/src/time_zone_if.cc b/absl/time/internal/cctz/src/time_zone_if.cc
index 0319b2f9..0e65cd9e 100644
--- a/absl/time/internal/cctz/src/time_zone_if.cc
+++ b/absl/time/internal/cctz/src/time_zone_if.cc
@@ -23,17 +23,19 @@ ABSL_NAMESPACE_BEGIN
 namespace time_internal {
 namespace cctz {
 
-std::unique_ptr<TimeZoneIf> TimeZoneIf::Load(const std::string& name) {
+std::unique_ptr<TimeZoneIf> TimeZoneIf::UTC() { return TimeZoneInfo::UTC(); }
+
+std::unique_ptr<TimeZoneIf> TimeZoneIf::Make(const std::string& name) {
   // Support "libc:localtime" and "libc:*" to access the legacy
   // localtime and UTC support respectively from the C library.
+  // NOTE: The "libc:*" zones are internal, test-only interfaces, and
+  // are subject to change/removal without notice. Do not use them.
   if (name.compare(0, 5, "libc:") == 0) {
-    return std::unique_ptr<TimeZoneIf>(new TimeZoneLibC(name.substr(5)));
+    return TimeZoneLibC::Make(name.substr(5));
   }
 
-  // Otherwise use the "zoneinfo" implementation by default.
-  std::unique_ptr<TimeZoneInfo> tz(new TimeZoneInfo);
-  if (!tz->Load(name)) tz.reset();
-  return std::unique_ptr<TimeZoneIf>(tz.release());
+  // Otherwise use the "zoneinfo" implementation.
+  return TimeZoneInfo::Make(name);
 }
 
 // Defined out-of-line to avoid emitting a weak vtable in all TUs.
diff --git a/absl/time/internal/cctz/src/time_zone_if.h b/absl/time/internal/cctz/src/time_zone_if.h
index 7d3e42d3..bec9beb5 100644
--- a/absl/time/internal/cctz/src/time_zone_if.h
+++ b/absl/time/internal/cctz/src/time_zone_if.h
@@ -33,8 +33,9 @@ namespace cctz {
 // Subclasses implement the functions for civil-time conversions in the zone.
 class TimeZoneIf {
  public:
-  // A factory function for TimeZoneIf implementations.
-  static std::unique_ptr<TimeZoneIf> Load(const std::string& name);
+  // Factory functions for TimeZoneIf implementations.
+  static std::unique_ptr<TimeZoneIf> UTC();  // never fails
+  static std::unique_ptr<TimeZoneIf> Make(const std::string& name);
 
   virtual ~TimeZoneIf();
 
@@ -51,7 +52,9 @@ class TimeZoneIf {
   virtual std::string Description() const = 0;
 
  protected:
-  TimeZoneIf() {}
+  TimeZoneIf() = default;
+  TimeZoneIf(const TimeZoneIf&) = delete;
+  TimeZoneIf& operator=(const TimeZoneIf&) = delete;
 };
 
 // Convert between time_point<seconds> and a count of seconds since the
diff --git a/absl/time/internal/cctz/src/time_zone_impl.cc b/absl/time/internal/cctz/src/time_zone_impl.cc
index f34e3aec..aadbb77d 100644
--- a/absl/time/internal/cctz/src/time_zone_impl.cc
+++ b/absl/time/internal/cctz/src/time_zone_impl.cc
@@ -99,11 +99,13 @@ void time_zone::Impl::ClearTimeZoneMapTestOnly() {
   }
 }
 
+time_zone::Impl::Impl() : name_("UTC"), zone_(TimeZoneIf::UTC()) {}
+
 time_zone::Impl::Impl(const std::string& name)
-    : name_(name), zone_(TimeZoneIf::Load(name_)) {}
+    : name_(name), zone_(TimeZoneIf::Make(name_)) {}
 
 const time_zone::Impl* time_zone::Impl::UTCImpl() {
-  static const Impl* utc_impl = new Impl("UTC");  // never fails
+  static const Impl* utc_impl = new Impl;
   return utc_impl;
 }
 
diff --git a/absl/time/internal/cctz/src/time_zone_impl.h b/absl/time/internal/cctz/src/time_zone_impl.h
index 7d747ba9..8308a3b4 100644
--- a/absl/time/internal/cctz/src/time_zone_impl.h
+++ b/absl/time/internal/cctz/src/time_zone_impl.h
@@ -78,7 +78,11 @@ class time_zone::Impl {
   std::string Description() const { return zone_->Description(); }
 
  private:
+  Impl();
   explicit Impl(const std::string& name);
+  Impl(const Impl&) = delete;
+  Impl& operator=(const Impl&) = delete;
+
   static const Impl* UTCImpl();
 
   const std::string name_;
diff --git a/absl/time/internal/cctz/src/time_zone_info.cc b/absl/time/internal/cctz/src/time_zone_info.cc
index 787426f7..f46198ff 100644
--- a/absl/time/internal/cctz/src/time_zone_info.cc
+++ b/absl/time/internal/cctz/src/time_zone_info.cc
@@ -45,6 +45,7 @@
 #include <sstream>
 #include <string>
 #include <utility>
+#include <vector>
 
 #include "absl/base/config.h"
 #include "absl/time/internal/cctz/include/cctz/civil_time.h"
@@ -134,6 +135,49 @@ std::int_fast64_t Decode64(const char* cp) {
   return static_cast<std::int_fast64_t>(v - s64maxU - 1) - s64max - 1;
 }
 
+struct Header {            // counts of:
+  std::size_t timecnt;     // transition times
+  std::size_t typecnt;     // transition types
+  std::size_t charcnt;     // zone abbreviation characters
+  std::size_t leapcnt;     // leap seconds (we expect none)
+  std::size_t ttisstdcnt;  // UTC/local indicators (unused)
+  std::size_t ttisutcnt;   // standard/wall indicators (unused)
+
+  bool Build(const tzhead& tzh);
+  std::size_t DataLength(std::size_t time_len) const;
+};
+
+// Builds the in-memory header using the raw bytes from the file.
+bool Header::Build(const tzhead& tzh) {
+  std::int_fast32_t v;
+  if ((v = Decode32(tzh.tzh_timecnt)) < 0) return false;
+  timecnt = static_cast<std::size_t>(v);
+  if ((v = Decode32(tzh.tzh_typecnt)) < 0) return false;
+  typecnt = static_cast<std::size_t>(v);
+  if ((v = Decode32(tzh.tzh_charcnt)) < 0) return false;
+  charcnt = static_cast<std::size_t>(v);
+  if ((v = Decode32(tzh.tzh_leapcnt)) < 0) return false;
+  leapcnt = static_cast<std::size_t>(v);
+  if ((v = Decode32(tzh.tzh_ttisstdcnt)) < 0) return false;
+  ttisstdcnt = static_cast<std::size_t>(v);
+  if ((v = Decode32(tzh.tzh_ttisutcnt)) < 0) return false;
+  ttisutcnt = static_cast<std::size_t>(v);
+  return true;
+}
+
+// How many bytes of data are associated with this header. The result
+// depends upon whether this is a section with 4-byte or 8-byte times.
+std::size_t Header::DataLength(std::size_t time_len) const {
+  std::size_t len = 0;
+  len += (time_len + 1) * timecnt;  // unix_time + type_index
+  len += (4 + 1 + 1) * typecnt;     // utc_offset + is_dst + abbr_index
+  len += 1 * charcnt;               // abbreviations
+  len += (time_len + 4) * leapcnt;  // leap-time + TAI-UTC
+  len += 1 * ttisstdcnt;            // UTC/local indicators
+  len += 1 * ttisutcnt;             // standard/wall indicators
+  return len;
+}
+
 // Does the rule for future transitions call for year-round daylight time?
 // See tz/zic.c:stringzone() for the details on how such rules are encoded.
 bool AllYearDST(const PosixTimeZone& posix) {
@@ -217,98 +261,6 @@ inline civil_second YearShift(const civil_second& cs, year_t shift) {
 
 }  // namespace
 
-// What (no leap-seconds) UTC+seconds zoneinfo would look like.
-bool TimeZoneInfo::ResetToBuiltinUTC(const seconds& offset) {
-  transition_types_.resize(1);
-  TransitionType& tt(transition_types_.back());
-  tt.utc_offset = static_cast<std::int_least32_t>(offset.count());
-  tt.is_dst = false;
-  tt.abbr_index = 0;
-
-  // We temporarily add some redundant, contemporary (2015 through 2025)
-  // transitions for performance reasons.  See TimeZoneInfo::LocalTime().
-  // TODO: Fix the performance issue and remove the extra transitions.
-  transitions_.clear();
-  transitions_.reserve(12);
-  for (const std::int_fast64_t unix_time : {
-           -(1LL << 59),  // a "first half" transition
-           1420070400LL,  // 2015-01-01T00:00:00+00:00
-           1451606400LL,  // 2016-01-01T00:00:00+00:00
-           1483228800LL,  // 2017-01-01T00:00:00+00:00
-           1514764800LL,  // 2018-01-01T00:00:00+00:00
-           1546300800LL,  // 2019-01-01T00:00:00+00:00
-           1577836800LL,  // 2020-01-01T00:00:00+00:00
-           1609459200LL,  // 2021-01-01T00:00:00+00:00
-           1640995200LL,  // 2022-01-01T00:00:00+00:00
-           1672531200LL,  // 2023-01-01T00:00:00+00:00
-           1704067200LL,  // 2024-01-01T00:00:00+00:00
-           1735689600LL,  // 2025-01-01T00:00:00+00:00
-       }) {
-    Transition& tr(*transitions_.emplace(transitions_.end()));
-    tr.unix_time = unix_time;
-    tr.type_index = 0;
-    tr.civil_sec = LocalTime(tr.unix_time, tt).cs;
-    tr.prev_civil_sec = tr.civil_sec - 1;
-  }
-
-  default_transition_type_ = 0;
-  abbreviations_ = FixedOffsetToAbbr(offset);
-  abbreviations_.append(1, '\0');
-  future_spec_.clear();  // never needed for a fixed-offset zone
-  extended_ = false;
-
-  tt.civil_max = LocalTime(seconds::max().count(), tt).cs;
-  tt.civil_min = LocalTime(seconds::min().count(), tt).cs;
-
-  transitions_.shrink_to_fit();
-  return true;
-}
-
-// Builds the in-memory header using the raw bytes from the file.
-bool TimeZoneInfo::Header::Build(const tzhead& tzh) {
-  std::int_fast32_t v;
-  if ((v = Decode32(tzh.tzh_timecnt)) < 0) return false;
-  timecnt = static_cast<std::size_t>(v);
-  if ((v = Decode32(tzh.tzh_typecnt)) < 0) return false;
-  typecnt = static_cast<std::size_t>(v);
-  if ((v = Decode32(tzh.tzh_charcnt)) < 0) return false;
-  charcnt = static_cast<std::size_t>(v);
-  if ((v = Decode32(tzh.tzh_leapcnt)) < 0) return false;
-  leapcnt = static_cast<std::size_t>(v);
-  if ((v = Decode32(tzh.tzh_ttisstdcnt)) < 0) return false;
-  ttisstdcnt = static_cast<std::size_t>(v);
-  if ((v = Decode32(tzh.tzh_ttisutcnt)) < 0) return false;
-  ttisutcnt = static_cast<std::size_t>(v);
-  return true;
-}
-
-// How many bytes of data are associated with this header. The result
-// depends upon whether this is a section with 4-byte or 8-byte times.
-std::size_t TimeZoneInfo::Header::DataLength(std::size_t time_len) const {
-  std::size_t len = 0;
-  len += (time_len + 1) * timecnt;  // unix_time + type_index
-  len += (4 + 1 + 1) * typecnt;     // utc_offset + is_dst + abbr_index
-  len += 1 * charcnt;               // abbreviations
-  len += (time_len + 4) * leapcnt;  // leap-time + TAI-UTC
-  len += 1 * ttisstdcnt;            // UTC/local indicators
-  len += 1 * ttisutcnt;             // standard/wall indicators
-  return len;
-}
-
-// zic(8) can generate no-op transitions when a zone changes rules at an
-// instant when there is actually no discontinuity.  So we check whether
-// two transitions have equivalent types (same offset/is_dst/abbr).
-bool TimeZoneInfo::EquivTransitions(std::uint_fast8_t tt1_index,
-                                    std::uint_fast8_t tt2_index) const {
-  if (tt1_index == tt2_index) return true;
-  const TransitionType& tt1(transition_types_[tt1_index]);
-  const TransitionType& tt2(transition_types_[tt2_index]);
-  if (tt1.utc_offset != tt2.utc_offset) return false;
-  if (tt1.is_dst != tt2.is_dst) return false;
-  if (tt1.abbr_index != tt2.abbr_index) return false;
-  return true;
-}
-
 // Find/make a transition type with these attributes.
 bool TimeZoneInfo::GetTransitionType(std::int_fast32_t utc_offset, bool is_dst,
                                      const std::string& abbr,
@@ -341,6 +293,20 @@ bool TimeZoneInfo::GetTransitionType(std::int_fast32_t utc_offset, bool is_dst,
   return true;
 }
 
+// zic(8) can generate no-op transitions when a zone changes rules at an
+// instant when there is actually no discontinuity.  So we check whether
+// two transitions have equivalent types (same offset/is_dst/abbr).
+bool TimeZoneInfo::EquivTransitions(std::uint_fast8_t tt1_index,
+                                    std::uint_fast8_t tt2_index) const {
+  if (tt1_index == tt2_index) return true;
+  const TransitionType& tt1(transition_types_[tt1_index]);
+  const TransitionType& tt2(transition_types_[tt2_index]);
+  if (tt1.utc_offset != tt2.utc_offset) return false;
+  if (tt1.is_dst != tt2.is_dst) return false;
+  if (tt1.abbr_index != tt2.abbr_index) return false;
+  return true;
+}
+
 // Use the POSIX-TZ-environment-variable-style string to handle times
 // in years after the last transition stored in the zoneinfo data.
 bool TimeZoneInfo::ExtendTransitions() {
@@ -372,11 +338,13 @@ bool TimeZoneInfo::ExtendTransitions() {
     return EquivTransitions(transitions_.back().type_index, dst_ti);
   }
 
-  // Extend the transitions for an additional 400 years using the
-  // future specification. Years beyond those can be handled by
-  // mapping back to a cycle-equivalent year within that range.
-  // We may need two additional transitions for the current year.
-  transitions_.reserve(transitions_.size() + 400 * 2 + 2);
+  // Extend the transitions for an additional 401 years using the future
+  // specification. Years beyond those can be handled by mapping back to
+  // a cycle-equivalent year within that range. Note that we need 401
+  // (well, at least the first transition in the 401st year) so that the
+  // end of the 400th year is mapped back to an extended year. And first
+  // we may also need two additional transitions for the current year.
+  transitions_.reserve(transitions_.size() + 2 + 401 * 2);
   extended_ = true;
 
   const Transition& last(transitions_.back());
@@ -390,7 +358,7 @@ bool TimeZoneInfo::ExtendTransitions() {
 
   Transition dst = {0, dst_ti, civil_second(), civil_second()};
   Transition std = {0, std_ti, civil_second(), civil_second()};
-  for (const year_t limit = last_year_ + 400;; ++last_year_) {
+  for (const year_t limit = last_year_ + 401;; ++last_year_) {
     auto dst_trans_off = TransOffset(leap_year, jan1_weekday, posix.dst_start);
     auto std_trans_off = TransOffset(leap_year, jan1_weekday, posix.dst_end);
     dst.unix_time = jan1_time + dst_trans_off - posix.std_offset;
@@ -410,193 +378,6 @@ bool TimeZoneInfo::ExtendTransitions() {
   return true;
 }
 
-bool TimeZoneInfo::Load(ZoneInfoSource* zip) {
-  // Read and validate the header.
-  tzhead tzh;
-  if (zip->Read(&tzh, sizeof(tzh)) != sizeof(tzh)) return false;
-  if (strncmp(tzh.tzh_magic, TZ_MAGIC, sizeof(tzh.tzh_magic)) != 0)
-    return false;
-  Header hdr;
-  if (!hdr.Build(tzh)) return false;
-  std::size_t time_len = 4;
-  if (tzh.tzh_version[0] != '\0') {
-    // Skip the 4-byte data.
-    if (zip->Skip(hdr.DataLength(time_len)) != 0) return false;
-    // Read and validate the header for the 8-byte data.
-    if (zip->Read(&tzh, sizeof(tzh)) != sizeof(tzh)) return false;
-    if (strncmp(tzh.tzh_magic, TZ_MAGIC, sizeof(tzh.tzh_magic)) != 0)
-      return false;
-    if (tzh.tzh_version[0] == '\0') return false;
-    if (!hdr.Build(tzh)) return false;
-    time_len = 8;
-  }
-  if (hdr.typecnt == 0) return false;
-  if (hdr.leapcnt != 0) {
-    // This code assumes 60-second minutes so we do not want
-    // the leap-second encoded zoneinfo. We could reverse the
-    // compensation, but the "right" encoding is rarely used
-    // so currently we simply reject such data.
-    return false;
-  }
-  if (hdr.ttisstdcnt != 0 && hdr.ttisstdcnt != hdr.typecnt) return false;
-  if (hdr.ttisutcnt != 0 && hdr.ttisutcnt != hdr.typecnt) return false;
-
-  // Read the data into a local buffer.
-  std::size_t len = hdr.DataLength(time_len);
-  std::vector<char> tbuf(len);
-  if (zip->Read(tbuf.data(), len) != len) return false;
-  const char* bp = tbuf.data();
-
-  // Decode and validate the transitions.
-  transitions_.reserve(hdr.timecnt + 2);
-  transitions_.resize(hdr.timecnt);
-  for (std::size_t i = 0; i != hdr.timecnt; ++i) {
-    transitions_[i].unix_time = (time_len == 4) ? Decode32(bp) : Decode64(bp);
-    bp += time_len;
-    if (i != 0) {
-      // Check that the transitions are ordered by time (as zic guarantees).
-      if (!Transition::ByUnixTime()(transitions_[i - 1], transitions_[i]))
-        return false;  // out of order
-    }
-  }
-  bool seen_type_0 = false;
-  for (std::size_t i = 0; i != hdr.timecnt; ++i) {
-    transitions_[i].type_index = Decode8(bp++);
-    if (transitions_[i].type_index >= hdr.typecnt) return false;
-    if (transitions_[i].type_index == 0) seen_type_0 = true;
-  }
-
-  // Decode and validate the transition types.
-  transition_types_.reserve(hdr.typecnt + 2);
-  transition_types_.resize(hdr.typecnt);
-  for (std::size_t i = 0; i != hdr.typecnt; ++i) {
-    transition_types_[i].utc_offset =
-        static_cast<std::int_least32_t>(Decode32(bp));
-    if (transition_types_[i].utc_offset >= kSecsPerDay ||
-        transition_types_[i].utc_offset <= -kSecsPerDay)
-      return false;
-    bp += 4;
-    transition_types_[i].is_dst = (Decode8(bp++) != 0);
-    transition_types_[i].abbr_index = Decode8(bp++);
-    if (transition_types_[i].abbr_index >= hdr.charcnt) return false;
-  }
-
-  // Determine the before-first-transition type.
-  default_transition_type_ = 0;
-  if (seen_type_0 && hdr.timecnt != 0) {
-    std::uint_fast8_t index = 0;
-    if (transition_types_[0].is_dst) {
-      index = transitions_[0].type_index;
-      while (index != 0 && transition_types_[index].is_dst) --index;
-    }
-    while (index != hdr.typecnt && transition_types_[index].is_dst) ++index;
-    if (index != hdr.typecnt) default_transition_type_ = index;
-  }
-
-  // Copy all the abbreviations.
-  abbreviations_.reserve(hdr.charcnt + 10);
-  abbreviations_.assign(bp, hdr.charcnt);
-  bp += hdr.charcnt;
-
-  // Skip the unused portions. We've already dispensed with leap-second
-  // encoded zoneinfo. The ttisstd/ttisgmt indicators only apply when
-  // interpreting a POSIX spec that does not include start/end rules, and
-  // that isn't the case here (see "zic -p").
-  bp += (time_len + 4) * hdr.leapcnt;  // leap-time + TAI-UTC
-  bp += 1 * hdr.ttisstdcnt;            // UTC/local indicators
-  bp += 1 * hdr.ttisutcnt;             // standard/wall indicators
-  assert(bp == tbuf.data() + tbuf.size());
-
-  future_spec_.clear();
-  if (tzh.tzh_version[0] != '\0') {
-    // Snarf up the NL-enclosed future POSIX spec. Note
-    // that version '3' files utilize an extended format.
-    auto get_char = [](ZoneInfoSource* azip) -> int {
-      unsigned char ch;  // all non-EOF results are positive
-      return (azip->Read(&ch, 1) == 1) ? ch : EOF;
-    };
-    if (get_char(zip) != '\n') return false;
-    for (int c = get_char(zip); c != '\n'; c = get_char(zip)) {
-      if (c == EOF) return false;
-      future_spec_.push_back(static_cast<char>(c));
-    }
-  }
-
-  // We don't check for EOF so that we're forwards compatible.
-
-  // If we did not find version information during the standard loading
-  // process (as of tzh_version '3' that is unsupported), then ask the
-  // ZoneInfoSource for any out-of-bound version string it may be privy to.
-  if (version_.empty()) {
-    version_ = zip->Version();
-  }
-
-  // Trim redundant transitions. zic may have added these to work around
-  // differences between the glibc and reference implementations (see
-  // zic.c:dontmerge) or to avoid bugs in old readers. For us, they just
-  // get in the way when we do future_spec_ extension.
-  while (hdr.timecnt > 1) {
-    if (!EquivTransitions(transitions_[hdr.timecnt - 1].type_index,
-                          transitions_[hdr.timecnt - 2].type_index)) {
-      break;
-    }
-    hdr.timecnt -= 1;
-  }
-  transitions_.resize(hdr.timecnt);
-
-  // Ensure that there is always a transition in the first half of the
-  // time line (the second half is handled below) so that the signed
-  // difference between a civil_second and the civil_second of its
-  // previous transition is always representable, without overflow.
-  if (transitions_.empty() || transitions_.front().unix_time >= 0) {
-    Transition& tr(*transitions_.emplace(transitions_.begin()));
-    tr.unix_time = -(1LL << 59);  // -18267312070-10-26T17:01:52+00:00
-    tr.type_index = default_transition_type_;
-  }
-
-  // Extend the transitions using the future specification.
-  if (!ExtendTransitions()) return false;
-
-  // Ensure that there is always a transition in the second half of the
-  // time line (the first half is handled above) so that the signed
-  // difference between a civil_second and the civil_second of its
-  // previous transition is always representable, without overflow.
-  const Transition& last(transitions_.back());
-  if (last.unix_time < 0) {
-    const std::uint_fast8_t type_index = last.type_index;
-    Transition& tr(*transitions_.emplace(transitions_.end()));
-    tr.unix_time = 2147483647;  // 2038-01-19T03:14:07+00:00
-    tr.type_index = type_index;
-  }
-
-  // Compute the local civil time for each transition and the preceding
-  // second. These will be used for reverse conversions in MakeTime().
-  const TransitionType* ttp = &transition_types_[default_transition_type_];
-  for (std::size_t i = 0; i != transitions_.size(); ++i) {
-    Transition& tr(transitions_[i]);
-    tr.prev_civil_sec = LocalTime(tr.unix_time, *ttp).cs - 1;
-    ttp = &transition_types_[tr.type_index];
-    tr.civil_sec = LocalTime(tr.unix_time, *ttp).cs;
-    if (i != 0) {
-      // Check that the transitions are ordered by civil time. Essentially
-      // this means that an offset change cannot cross another such change.
-      // No one does this in practice, and we depend on it in MakeTime().
-      if (!Transition::ByCivilTime()(transitions_[i - 1], tr))
-        return false;  // out of order
-    }
-  }
-
-  // Compute the maximum/minimum civil times that can be converted to a
-  // time_point<seconds> for each of the zone's transition types.
-  for (auto& tt : transition_types_) {
-    tt.civil_max = LocalTime(seconds::max().count(), tt).cs;
-    tt.civil_min = LocalTime(seconds::min().count(), tt).cs;
-  }
-
-  transitions_.shrink_to_fit();
-  return true;
-}
-
 namespace {
 
 using FilePtr = std::unique_ptr<FILE, int (*)(FILE*)>;
@@ -795,6 +576,240 @@ std::unique_ptr<ZoneInfoSource> FuchsiaZoneInfoSource::Open(
 
 }  // namespace
 
+// What (no leap-seconds) UTC+seconds zoneinfo would look like.
+bool TimeZoneInfo::ResetToBuiltinUTC(const seconds& offset) {
+  transition_types_.resize(1);
+  TransitionType& tt(transition_types_.back());
+  tt.utc_offset = static_cast<std::int_least32_t>(offset.count());
+  tt.is_dst = false;
+  tt.abbr_index = 0;
+
+  // We temporarily add some redundant, contemporary (2015 through 2025)
+  // transitions for performance reasons.  See TimeZoneInfo::LocalTime().
+  // TODO: Fix the performance issue and remove the extra transitions.
+  transitions_.clear();
+  transitions_.reserve(12);
+  for (const std::int_fast64_t unix_time : {
+           -(1LL << 59),  // a "first half" transition
+           1420070400LL,  // 2015-01-01T00:00:00+00:00
+           1451606400LL,  // 2016-01-01T00:00:00+00:00
+           1483228800LL,  // 2017-01-01T00:00:00+00:00
+           1514764800LL,  // 2018-01-01T00:00:00+00:00
+           1546300800LL,  // 2019-01-01T00:00:00+00:00
+           1577836800LL,  // 2020-01-01T00:00:00+00:00
+           1609459200LL,  // 2021-01-01T00:00:00+00:00
+           1640995200LL,  // 2022-01-01T00:00:00+00:00
+           1672531200LL,  // 2023-01-01T00:00:00+00:00
+           1704067200LL,  // 2024-01-01T00:00:00+00:00
+           1735689600LL,  // 2025-01-01T00:00:00+00:00
+       }) {
+    Transition& tr(*transitions_.emplace(transitions_.end()));
+    tr.unix_time = unix_time;
+    tr.type_index = 0;
+    tr.civil_sec = LocalTime(tr.unix_time, tt).cs;
+    tr.prev_civil_sec = tr.civil_sec - 1;
+  }
+
+  default_transition_type_ = 0;
+  abbreviations_ = FixedOffsetToAbbr(offset);
+  abbreviations_.append(1, '\0');
+  future_spec_.clear();  // never needed for a fixed-offset zone
+  extended_ = false;
+
+  tt.civil_max = LocalTime(seconds::max().count(), tt).cs;
+  tt.civil_min = LocalTime(seconds::min().count(), tt).cs;
+
+  transitions_.shrink_to_fit();
+  return true;
+}
+
+bool TimeZoneInfo::Load(ZoneInfoSource* zip) {
+  // Read and validate the header.
+  tzhead tzh;
+  if (zip->Read(&tzh, sizeof(tzh)) != sizeof(tzh)) return false;
+  if (strncmp(tzh.tzh_magic, TZ_MAGIC, sizeof(tzh.tzh_magic)) != 0)
+    return false;
+  Header hdr;
+  if (!hdr.Build(tzh)) return false;
+  std::size_t time_len = 4;
+  if (tzh.tzh_version[0] != '\0') {
+    // Skip the 4-byte data.
+    if (zip->Skip(hdr.DataLength(time_len)) != 0) return false;
+    // Read and validate the header for the 8-byte data.
+    if (zip->Read(&tzh, sizeof(tzh)) != sizeof(tzh)) return false;
+    if (strncmp(tzh.tzh_magic, TZ_MAGIC, sizeof(tzh.tzh_magic)) != 0)
+      return false;
+    if (tzh.tzh_version[0] == '\0') return false;
+    if (!hdr.Build(tzh)) return false;
+    time_len = 8;
+  }
+  if (hdr.typecnt == 0) return false;
+  if (hdr.leapcnt != 0) {
+    // This code assumes 60-second minutes so we do not want
+    // the leap-second encoded zoneinfo. We could reverse the
+    // compensation, but the "right" encoding is rarely used
+    // so currently we simply reject such data.
+    return false;
+  }
+  if (hdr.ttisstdcnt != 0 && hdr.ttisstdcnt != hdr.typecnt) return false;
+  if (hdr.ttisutcnt != 0 && hdr.ttisutcnt != hdr.typecnt) return false;
+
+  // Read the data into a local buffer.
+  std::size_t len = hdr.DataLength(time_len);
+  std::vector<char> tbuf(len);
+  if (zip->Read(tbuf.data(), len) != len) return false;
+  const char* bp = tbuf.data();
+
+  // Decode and validate the transitions.
+  transitions_.reserve(hdr.timecnt + 2);
+  transitions_.resize(hdr.timecnt);
+  for (std::size_t i = 0; i != hdr.timecnt; ++i) {
+    transitions_[i].unix_time = (time_len == 4) ? Decode32(bp) : Decode64(bp);
+    bp += time_len;
+    if (i != 0) {
+      // Check that the transitions are ordered by time (as zic guarantees).
+      if (!Transition::ByUnixTime()(transitions_[i - 1], transitions_[i]))
+        return false;  // out of order
+    }
+  }
+  bool seen_type_0 = false;
+  for (std::size_t i = 0; i != hdr.timecnt; ++i) {
+    transitions_[i].type_index = Decode8(bp++);
+    if (transitions_[i].type_index >= hdr.typecnt) return false;
+    if (transitions_[i].type_index == 0) seen_type_0 = true;
+  }
+
+  // Decode and validate the transition types.
+  transition_types_.reserve(hdr.typecnt + 2);
+  transition_types_.resize(hdr.typecnt);
+  for (std::size_t i = 0; i != hdr.typecnt; ++i) {
+    transition_types_[i].utc_offset =
+        static_cast<std::int_least32_t>(Decode32(bp));
+    if (transition_types_[i].utc_offset >= kSecsPerDay ||
+        transition_types_[i].utc_offset <= -kSecsPerDay)
+      return false;
+    bp += 4;
+    transition_types_[i].is_dst = (Decode8(bp++) != 0);
+    transition_types_[i].abbr_index = Decode8(bp++);
+    if (transition_types_[i].abbr_index >= hdr.charcnt) return false;
+  }
+
+  // Determine the before-first-transition type.
+  default_transition_type_ = 0;
+  if (seen_type_0 && hdr.timecnt != 0) {
+    std::uint_fast8_t index = 0;
+    if (transition_types_[0].is_dst) {
+      index = transitions_[0].type_index;
+      while (index != 0 && transition_types_[index].is_dst) --index;
+    }
+    while (index != hdr.typecnt && transition_types_[index].is_dst) ++index;
+    if (index != hdr.typecnt) default_transition_type_ = index;
+  }
+
+  // Copy all the abbreviations.
+  abbreviations_.reserve(hdr.charcnt + 10);
+  abbreviations_.assign(bp, hdr.charcnt);
+  bp += hdr.charcnt;
+
+  // Skip the unused portions. We've already dispensed with leap-second
+  // encoded zoneinfo. The ttisstd/ttisgmt indicators only apply when
+  // interpreting a POSIX spec that does not include start/end rules, and
+  // that isn't the case here (see "zic -p").
+  bp += (time_len + 4) * hdr.leapcnt;  // leap-time + TAI-UTC
+  bp += 1 * hdr.ttisstdcnt;            // UTC/local indicators
+  bp += 1 * hdr.ttisutcnt;             // standard/wall indicators
+  assert(bp == tbuf.data() + tbuf.size());
+
+  future_spec_.clear();
+  if (tzh.tzh_version[0] != '\0') {
+    // Snarf up the NL-enclosed future POSIX spec. Note
+    // that version '3' files utilize an extended format.
+    auto get_char = [](ZoneInfoSource* azip) -> int {
+      unsigned char ch;  // all non-EOF results are positive
+      return (azip->Read(&ch, 1) == 1) ? ch : EOF;
+    };
+    if (get_char(zip) != '\n') return false;
+    for (int c = get_char(zip); c != '\n'; c = get_char(zip)) {
+      if (c == EOF) return false;
+      future_spec_.push_back(static_cast<char>(c));
+    }
+  }
+
+  // We don't check for EOF so that we're forwards compatible.
+
+  // If we did not find version information during the standard loading
+  // process (as of tzh_version '3' that is unsupported), then ask the
+  // ZoneInfoSource for any out-of-bound version string it may be privy to.
+  if (version_.empty()) {
+    version_ = zip->Version();
+  }
+
+  // Trim redundant transitions. zic may have added these to work around
+  // differences between the glibc and reference implementations (see
+  // zic.c:dontmerge) or to avoid bugs in old readers. For us, they just
+  // get in the way when we do future_spec_ extension.
+  while (hdr.timecnt > 1) {
+    if (!EquivTransitions(transitions_[hdr.timecnt - 1].type_index,
+                          transitions_[hdr.timecnt - 2].type_index)) {
+      break;
+    }
+    hdr.timecnt -= 1;
+  }
+  transitions_.resize(hdr.timecnt);
+
+  // Ensure that there is always a transition in the first half of the
+  // time line (the second half is handled below) so that the signed
+  // difference between a civil_second and the civil_second of its
+  // previous transition is always representable, without overflow.
+  if (transitions_.empty() || transitions_.front().unix_time >= 0) {
+    Transition& tr(*transitions_.emplace(transitions_.begin()));
+    tr.unix_time = -(1LL << 59);  // -18267312070-10-26T17:01:52+00:00
+    tr.type_index = default_transition_type_;
+  }
+
+  // Extend the transitions using the future specification.
+  if (!ExtendTransitions()) return false;
+
+  // Ensure that there is always a transition in the second half of the
+  // time line (the first half is handled above) so that the signed
+  // difference between a civil_second and the civil_second of its
+  // previous transition is always representable, without overflow.
+  const Transition& last(transitions_.back());
+  if (last.unix_time < 0) {
+    const std::uint_fast8_t type_index = last.type_index;
+    Transition& tr(*transitions_.emplace(transitions_.end()));
+    tr.unix_time = 2147483647;  // 2038-01-19T03:14:07+00:00
+    tr.type_index = type_index;
+  }
+
+  // Compute the local civil time for each transition and the preceding
+  // second. These will be used for reverse conversions in MakeTime().
+  const TransitionType* ttp = &transition_types_[default_transition_type_];
+  for (std::size_t i = 0; i != transitions_.size(); ++i) {
+    Transition& tr(transitions_[i]);
+    tr.prev_civil_sec = LocalTime(tr.unix_time, *ttp).cs - 1;
+    ttp = &transition_types_[tr.type_index];
+    tr.civil_sec = LocalTime(tr.unix_time, *ttp).cs;
+    if (i != 0) {
+      // Check that the transitions are ordered by civil time. Essentially
+      // this means that an offset change cannot cross another such change.
+      // No one does this in practice, and we depend on it in MakeTime().
+      if (!Transition::ByCivilTime()(transitions_[i - 1], tr))
+        return false;  // out of order
+    }
+  }
+
+  // Compute the maximum/minimum civil times that can be converted to a
+  // time_point<seconds> for each of the zone's transition types.
+  for (auto& tt : transition_types_) {
+    tt.civil_max = LocalTime(seconds::max().count(), tt).cs;
+    tt.civil_min = LocalTime(seconds::min().count(), tt).cs;
+  }
+
+  transitions_.shrink_to_fit();
+  return true;
+}
+
 bool TimeZoneInfo::Load(const std::string& name) {
   // We can ensure that the loading of UTC or any other fixed-offset
   // zone never fails because the simple, fixed-offset state can be
@@ -816,6 +831,18 @@ bool TimeZoneInfo::Load(const std::string& name) {
   return zip != nullptr && Load(zip.get());
 }
 
+std::unique_ptr<TimeZoneInfo> TimeZoneInfo::UTC() {
+  auto tz = std::unique_ptr<TimeZoneInfo>(new TimeZoneInfo);
+  tz->ResetToBuiltinUTC(seconds::zero());
+  return tz;
+}
+
+std::unique_ptr<TimeZoneInfo> TimeZoneInfo::Make(const std::string& name) {
+  auto tz = std::unique_ptr<TimeZoneInfo>(new TimeZoneInfo);
+  if (!tz->Load(name)) tz.reset();  // fallback to UTC
+  return tz;
+}
+
 // BreakTime() translation for a particular transition type.
 time_zone::absolute_lookup TimeZoneInfo::LocalTime(
     std::int_fast64_t unix_time, const TransitionType& tt) const {
diff --git a/absl/time/internal/cctz/src/time_zone_info.h b/absl/time/internal/cctz/src/time_zone_info.h
index 2467ff55..689df6f9 100644
--- a/absl/time/internal/cctz/src/time_zone_info.h
+++ b/absl/time/internal/cctz/src/time_zone_info.h
@@ -18,6 +18,7 @@
 #include <atomic>
 #include <cstddef>
 #include <cstdint>
+#include <memory>
 #include <string>
 #include <vector>
 
@@ -64,12 +65,9 @@ struct TransitionType {
 // A time zone backed by the IANA Time Zone Database (zoneinfo).
 class TimeZoneInfo : public TimeZoneIf {
  public:
-  TimeZoneInfo() = default;
-  TimeZoneInfo(const TimeZoneInfo&) = delete;
-  TimeZoneInfo& operator=(const TimeZoneInfo&) = delete;
-
-  // Loads the zoneinfo for the given name, returning true if successful.
-  bool Load(const std::string& name);
+  // Factories.
+  static std::unique_ptr<TimeZoneInfo> UTC();  // never fails
+  static std::unique_ptr<TimeZoneInfo> Make(const std::string& name);
 
   // TimeZoneIf implementations.
   time_zone::absolute_lookup BreakTime(
@@ -83,17 +81,9 @@ class TimeZoneInfo : public TimeZoneIf {
   std::string Description() const override;
 
  private:
-  struct Header {            // counts of:
-    std::size_t timecnt;     // transition times
-    std::size_t typecnt;     // transition types
-    std::size_t charcnt;     // zone abbreviation characters
-    std::size_t leapcnt;     // leap seconds (we expect none)
-    std::size_t ttisstdcnt;  // UTC/local indicators (unused)
-    std::size_t ttisutcnt;   // standard/wall indicators (unused)
-
-    bool Build(const tzhead& tzh);
-    std::size_t DataLength(std::size_t time_len) const;
-  };
+  TimeZoneInfo() = default;
+  TimeZoneInfo(const TimeZoneInfo&) = delete;
+  TimeZoneInfo& operator=(const TimeZoneInfo&) = delete;
 
   bool GetTransitionType(std::int_fast32_t utc_offset, bool is_dst,
                          const std::string& abbr, std::uint_least8_t* index);
@@ -102,6 +92,7 @@ class TimeZoneInfo : public TimeZoneIf {
   bool ExtendTransitions();
 
   bool ResetToBuiltinUTC(const seconds& offset);
+  bool Load(const std::string& name);
   bool Load(ZoneInfoSource* zip);
 
   // Helpers for BreakTime() and MakeTime().
diff --git a/absl/time/internal/cctz/src/time_zone_libc.cc b/absl/time/internal/cctz/src/time_zone_libc.cc
index 887dd097..d0146122 100644
--- a/absl/time/internal/cctz/src/time_zone_libc.cc
+++ b/absl/time/internal/cctz/src/time_zone_libc.cc
@@ -62,7 +62,7 @@ auto tm_zone(const std::tm& tm) -> decltype(tzname[0]) {
 }
 #elif defined(__native_client__) || defined(__myriad2__) || \
     defined(__EMSCRIPTEN__)
-// Uses the globals: 'timezone' and 'tzname'.
+// Uses the globals: '_timezone' and 'tzname'.
 auto tm_gmtoff(const std::tm& tm) -> decltype(_timezone + 0) {
   const bool is_dst = tm.tm_isdst > 0;
   return _timezone + (is_dst ? 60 * 60 : 0);
@@ -71,6 +71,16 @@ auto tm_zone(const std::tm& tm) -> decltype(tzname[0]) {
   const bool is_dst = tm.tm_isdst > 0;
   return tzname[is_dst];
 }
+#elif defined(__VXWORKS__)
+// Uses the globals: 'timezone' and 'tzname'.
+auto tm_gmtoff(const std::tm& tm) -> decltype(timezone + 0) {
+  const bool is_dst = tm.tm_isdst > 0;
+  return timezone + (is_dst ? 60 * 60 : 0);
+}
+auto tm_zone(const std::tm& tm) -> decltype(tzname[0]) {
+  const bool is_dst = tm.tm_isdst > 0;
+  return tzname[is_dst];
+}
 #else
 // Adapt to different spellings of the struct std::tm extension fields.
 #if defined(tm_gmtoff)
@@ -108,6 +118,7 @@ auto tm_zone(const T& tm) -> decltype(tm.__tm_zone) {
 }
 #endif  // tm_zone
 #endif
+using tm_gmtoff_t = decltype(tm_gmtoff(std::tm{}));
 
 inline std::tm* gm_time(const std::time_t* timep, std::tm* result) {
 #if defined(_WIN32) || defined(_WIN64)
@@ -125,37 +136,36 @@ inline std::tm* local_time(const std::time_t* timep, std::tm* result) {
 #endif
 }
 
-// Converts a civil second and "dst" flag into a time_t and UTC offset.
+// Converts a civil second and "dst" flag into a time_t and a struct tm.
 // Returns false if time_t cannot represent the requested civil second.
 // Caller must have already checked that cs.year() will fit into a tm_year.
-bool make_time(const civil_second& cs, int is_dst, std::time_t* t, int* off) {
-  std::tm tm;
-  tm.tm_year = static_cast<int>(cs.year() - year_t{1900});
-  tm.tm_mon = cs.month() - 1;
-  tm.tm_mday = cs.day();
-  tm.tm_hour = cs.hour();
-  tm.tm_min = cs.minute();
-  tm.tm_sec = cs.second();
-  tm.tm_isdst = is_dst;
-  *t = std::mktime(&tm);
+bool make_time(const civil_second& cs, int is_dst, std::time_t* t,
+               std::tm* tm) {
+  tm->tm_year = static_cast<int>(cs.year() - year_t{1900});
+  tm->tm_mon = cs.month() - 1;
+  tm->tm_mday = cs.day();
+  tm->tm_hour = cs.hour();
+  tm->tm_min = cs.minute();
+  tm->tm_sec = cs.second();
+  tm->tm_isdst = is_dst;
+  *t = std::mktime(tm);
   if (*t == std::time_t{-1}) {
     std::tm tm2;
     const std::tm* tmp = local_time(t, &tm2);
-    if (tmp == nullptr || tmp->tm_year != tm.tm_year ||
-        tmp->tm_mon != tm.tm_mon || tmp->tm_mday != tm.tm_mday ||
-        tmp->tm_hour != tm.tm_hour || tmp->tm_min != tm.tm_min ||
-        tmp->tm_sec != tm.tm_sec) {
+    if (tmp == nullptr || tmp->tm_year != tm->tm_year ||
+        tmp->tm_mon != tm->tm_mon || tmp->tm_mday != tm->tm_mday ||
+        tmp->tm_hour != tm->tm_hour || tmp->tm_min != tm->tm_min ||
+        tmp->tm_sec != tm->tm_sec) {
       // A true error (not just one second before the epoch).
       return false;
     }
   }
-  *off = static_cast<int>(tm_gmtoff(tm));
   return true;
 }
 
 // Find the least time_t in [lo:hi] where local time matches offset, given:
 // (1) lo doesn't match, (2) hi does, and (3) there is only one transition.
-std::time_t find_trans(std::time_t lo, std::time_t hi, int offset) {
+std::time_t find_trans(std::time_t lo, std::time_t hi, tm_gmtoff_t offset) {
   std::tm tm;
   while (lo + 1 != hi) {
     const std::time_t mid = lo + (hi - lo) / 2;
@@ -183,8 +193,9 @@ std::time_t find_trans(std::time_t lo, std::time_t hi, int offset) {
 
 }  // namespace
 
-TimeZoneLibC::TimeZoneLibC(const std::string& name)
-    : local_(name == "localtime") {}
+std::unique_ptr<TimeZoneLibC> TimeZoneLibC::Make(const std::string& name) {
+  return std::unique_ptr<TimeZoneLibC>(new TimeZoneLibC(name));
+}
 
 time_zone::absolute_lookup TimeZoneLibC::BreakTime(
     const time_point<seconds>& tp) const {
@@ -254,33 +265,37 @@ time_zone::civil_lookup TimeZoneLibC::MakeTime(const civil_second& cs) const {
   // We probe with "is_dst" values of 0 and 1 to try to distinguish unique
   // civil seconds from skipped or repeated ones.  This is not always possible
   // however, as the "dst" flag does not change over some offset transitions.
-  // We are also subject to the vagaries of mktime() implementations.
+  // We are also subject to the vagaries of mktime() implementations. For
+  // example, some implementations treat "tm_isdst" as a demand (useless),
+  // and some as a disambiguator (useful).
   std::time_t t0, t1;
-  int offset0, offset1;
-  if (make_time(cs, 0, &t0, &offset0) && make_time(cs, 1, &t1, &offset1)) {
-    if (t0 == t1) {
+  std::tm tm0, tm1;
+  if (make_time(cs, 0, &t0, &tm0) && make_time(cs, 1, &t1, &tm1)) {
+    if (tm0.tm_isdst == tm1.tm_isdst) {
       // The civil time was singular (pre == trans == post).
-      const time_point<seconds> tp = FromUnixSeconds(t0);
+      const time_point<seconds> tp = FromUnixSeconds(tm0.tm_isdst ? t1 : t0);
       return {time_zone::civil_lookup::UNIQUE, tp, tp, tp};
     }
 
-    if (t0 > t1) {
+    tm_gmtoff_t offset = tm_gmtoff(tm0);
+    if (t0 < t1) {  // negative DST
       std::swap(t0, t1);
-      std::swap(offset0, offset1);
+      offset = tm_gmtoff(tm1);
     }
-    const std::time_t tt = find_trans(t0, t1, offset1);
+
+    const std::time_t tt = find_trans(t1, t0, offset);
     const time_point<seconds> trans = FromUnixSeconds(tt);
 
-    if (offset0 < offset1) {
+    if (tm0.tm_isdst) {
       // The civil time did not exist (pre >= trans > post).
-      const time_point<seconds> pre = FromUnixSeconds(t1);
-      const time_point<seconds> post = FromUnixSeconds(t0);
+      const time_point<seconds> pre = FromUnixSeconds(t0);
+      const time_point<seconds> post = FromUnixSeconds(t1);
       return {time_zone::civil_lookup::SKIPPED, pre, trans, post};
     }
 
     // The civil time was ambiguous (pre < trans <= post).
-    const time_point<seconds> pre = FromUnixSeconds(t0);
-    const time_point<seconds> post = FromUnixSeconds(t1);
+    const time_point<seconds> pre = FromUnixSeconds(t1);
+    const time_point<seconds> post = FromUnixSeconds(t0);
     return {time_zone::civil_lookup::REPEATED, pre, trans, post};
   }
 
@@ -309,6 +324,9 @@ std::string TimeZoneLibC::Description() const {
   return local_ ? "localtime" : "UTC";
 }
 
+TimeZoneLibC::TimeZoneLibC(const std::string& name)
+    : local_(name == "localtime") {}
+
 }  // namespace cctz
 }  // namespace time_internal
 ABSL_NAMESPACE_END
diff --git a/absl/time/internal/cctz/src/time_zone_libc.h b/absl/time/internal/cctz/src/time_zone_libc.h
index 1da9039a..ae210737 100644
--- a/absl/time/internal/cctz/src/time_zone_libc.h
+++ b/absl/time/internal/cctz/src/time_zone_libc.h
@@ -15,6 +15,7 @@
 #ifndef ABSL_TIME_INTERNAL_CCTZ_TIME_ZONE_LIBC_H_
 #define ABSL_TIME_INTERNAL_CCTZ_TIME_ZONE_LIBC_H_
 
+#include <memory>
 #include <string>
 
 #include "absl/base/config.h"
@@ -27,10 +28,10 @@ namespace cctz {
 
 // A time zone backed by gmtime_r(3), localtime_r(3), and mktime(3),
 // and which therefore only supports UTC and the local time zone.
-// TODO: Add support for fixed offsets from UTC.
 class TimeZoneLibC : public TimeZoneIf {
  public:
-  explicit TimeZoneLibC(const std::string& name);
+  // Factory.
+  static std::unique_ptr<TimeZoneLibC> Make(const std::string& name);
 
   // TimeZoneIf implementations.
   time_zone::absolute_lookup BreakTime(
@@ -44,6 +45,10 @@ class TimeZoneLibC : public TimeZoneIf {
   std::string Description() const override;
 
  private:
+  explicit TimeZoneLibC(const std::string& name);
+  TimeZoneLibC(const TimeZoneLibC&) = delete;
+  TimeZoneLibC& operator=(const TimeZoneLibC&) = delete;
+
   const bool local_;  // localtime or UTC
 };
 
diff --git a/absl/time/internal/cctz/src/time_zone_lookup.cc b/absl/time/internal/cctz/src/time_zone_lookup.cc
index f6983aeb..d22691bd 100644
--- a/absl/time/internal/cctz/src/time_zone_lookup.cc
+++ b/absl/time/internal/cctz/src/time_zone_lookup.cc
@@ -35,6 +35,24 @@
 #include <zircon/types.h>
 #endif
 
+#if defined(_WIN32)
+#include <sdkddkver.h>
+// Include only when the SDK is for Windows 10 (and later), and the binary is
+// targeted for Windows XP and later.
+// Note: The Windows SDK added windows.globalization.h file for Windows 10, but
+// MinGW did not add it until NTDDI_WIN10_NI (SDK version 10.0.22621.0).
+#if ((defined(_WIN32_WINNT_WIN10) && !defined(__MINGW32__)) ||        \
+     (defined(NTDDI_WIN10_NI) && NTDDI_VERSION >= NTDDI_WIN10_NI)) && \
+    (_WIN32_WINNT >= _WIN32_WINNT_WINXP)
+#define USE_WIN32_LOCAL_TIME_ZONE
+#include <roapi.h>
+#include <tchar.h>
+#include <wchar.h>
+#include <windows.globalization.h>
+#include <windows.h>
+#endif
+#endif
+
 #include <cstdlib>
 #include <cstring>
 #include <string>
@@ -47,8 +65,8 @@ ABSL_NAMESPACE_BEGIN
 namespace time_internal {
 namespace cctz {
 
-#if defined(__ANDROID__) && defined(__ANDROID_API__) && __ANDROID_API__ >= 21
 namespace {
+#if defined(__ANDROID__) && defined(__ANDROID_API__) && __ANDROID_API__ >= 21
 // Android 'L' removes __system_property_get() from the NDK, however
 // it is still a hidden symbol in libc so we use dlsym() to access it.
 // See Chromium's base/sys_info_android.cc for a similar example.
@@ -72,9 +90,84 @@ int __system_property_get(const char* name, char* value) {
   static property_get_func system_property_get = LoadSystemPropertyGet();
   return system_property_get ? system_property_get(name, value) : -1;
 }
+#endif
 
-}  // namespace
+#if defined(USE_WIN32_LOCAL_TIME_ZONE)
+// Calls the WinRT Calendar.GetTimeZone method to obtain the IANA ID of the
+// local time zone. Returns an empty vector in case of an error.
+std::string win32_local_time_zone(const HMODULE combase) {
+  std::string result;
+  const auto ro_activate_instance =
+      reinterpret_cast<decltype(&RoActivateInstance)>(
+          GetProcAddress(combase, "RoActivateInstance"));
+  if (!ro_activate_instance) {
+    return result;
+  }
+  const auto windows_create_string_reference =
+      reinterpret_cast<decltype(&WindowsCreateStringReference)>(
+          GetProcAddress(combase, "WindowsCreateStringReference"));
+  if (!windows_create_string_reference) {
+    return result;
+  }
+  const auto windows_delete_string =
+      reinterpret_cast<decltype(&WindowsDeleteString)>(
+          GetProcAddress(combase, "WindowsDeleteString"));
+  if (!windows_delete_string) {
+    return result;
+  }
+  const auto windows_get_string_raw_buffer =
+      reinterpret_cast<decltype(&WindowsGetStringRawBuffer)>(
+          GetProcAddress(combase, "WindowsGetStringRawBuffer"));
+  if (!windows_get_string_raw_buffer) {
+    return result;
+  }
+
+  // The string returned by WindowsCreateStringReference doesn't need to be
+  // deleted.
+  HSTRING calendar_class_id;
+  HSTRING_HEADER calendar_class_id_header;
+  HRESULT hr = windows_create_string_reference(
+      RuntimeClass_Windows_Globalization_Calendar,
+      sizeof(RuntimeClass_Windows_Globalization_Calendar) / sizeof(wchar_t) - 1,
+      &calendar_class_id_header, &calendar_class_id);
+  if (FAILED(hr)) {
+    return result;
+  }
+
+  IInspectable* calendar;
+  hr = ro_activate_instance(calendar_class_id, &calendar);
+  if (FAILED(hr)) {
+    return result;
+  }
+
+  ABI::Windows::Globalization::ITimeZoneOnCalendar* time_zone;
+  hr = calendar->QueryInterface(IID_PPV_ARGS(&time_zone));
+  if (FAILED(hr)) {
+    calendar->Release();
+    return result;
+  }
+
+  HSTRING tz_hstr;
+  hr = time_zone->GetTimeZone(&tz_hstr);
+  if (SUCCEEDED(hr)) {
+    UINT32 wlen;
+    const PCWSTR tz_wstr = windows_get_string_raw_buffer(tz_hstr, &wlen);
+    if (tz_wstr) {
+      const int size =
+          WideCharToMultiByte(CP_UTF8, 0, tz_wstr, static_cast<int>(wlen),
+                              nullptr, 0, nullptr, nullptr);
+      result.resize(static_cast<size_t>(size));
+      WideCharToMultiByte(CP_UTF8, 0, tz_wstr, static_cast<int>(wlen),
+                          &result[0], size, nullptr, nullptr);
+    }
+    windows_delete_string(tz_hstr);
+  }
+  time_zone->Release();
+  calendar->Release();
+  return result;
+}
 #endif
+}  // namespace
 
 std::string time_zone::name() const { return effective_impl().Name(); }
 
@@ -190,6 +283,39 @@ time_zone local_time_zone() {
     zone = primary_tz.c_str();
   }
 #endif
+#if defined(USE_WIN32_LOCAL_TIME_ZONE)
+  // Use the WinRT Calendar class to get the local time zone. This feature is
+  // available on Windows 10 and later. The library is dynamically linked to
+  // maintain binary compatibility with Windows XP - Windows 7. On Windows 8,
+  // The combase.dll API functions are available but the RoActivateInstance
+  // call will fail for the Calendar class.
+  std::string winrt_tz;
+  const HMODULE combase =
+      LoadLibraryEx(_T("combase.dll"), nullptr, LOAD_LIBRARY_SEARCH_SYSTEM32);
+  if (combase) {
+    const auto ro_initialize = reinterpret_cast<decltype(&::RoInitialize)>(
+        GetProcAddress(combase, "RoInitialize"));
+    const auto ro_uninitialize = reinterpret_cast<decltype(&::RoUninitialize)>(
+        GetProcAddress(combase, "RoUninitialize"));
+    if (ro_initialize && ro_uninitialize) {
+      const HRESULT hr = ro_initialize(RO_INIT_MULTITHREADED);
+      // RPC_E_CHANGED_MODE means that a previous RoInitialize call specified
+      // a different concurrency model. The WinRT runtime is initialized and
+      // should work for our purpose here, but we should *not* call
+      // RoUninitialize because it's a failure.
+      if (SUCCEEDED(hr) || hr == RPC_E_CHANGED_MODE) {
+        winrt_tz = win32_local_time_zone(combase);
+        if (SUCCEEDED(hr)) {
+          ro_uninitialize();
+        }
+      }
+    }
+    FreeLibrary(combase);
+  }
+  if (!winrt_tz.empty()) {
+    zone = winrt_tz.c_str();
+  }
+#endif
 
   // Allow ${TZ} to override to default zone.
   char* tz_env = nullptr;
diff --git a/absl/time/internal/cctz/src/time_zone_lookup_test.cc b/absl/time/internal/cctz/src/time_zone_lookup_test.cc
index ab461f04..4884c32e 100644
--- a/absl/time/internal/cctz/src/time_zone_lookup_test.cc
+++ b/absl/time/internal/cctz/src/time_zone_lookup_test.cc
@@ -135,6 +135,7 @@ const char* const kTimeZoneNames[] = {"Africa/Abidjan",
                                       "America/Cayman",
                                       "America/Chicago",
                                       "America/Chihuahua",
+                                      "America/Ciudad_Juarez",
                                       "America/Coral_Harbour",
                                       "America/Cordoba",
                                       "America/Costa_Rica",
@@ -734,6 +735,10 @@ TEST(TimeZone, UTC) {
   time_zone loaded_utc0;
   EXPECT_TRUE(load_time_zone("UTC0", &loaded_utc0));
   EXPECT_EQ(loaded_utc0, utc);
+
+  time_zone loaded_bad;
+  EXPECT_FALSE(load_time_zone("Invalid/TimeZone", &loaded_bad));
+  EXPECT_EQ(loaded_bad, utc);
 }
 
 TEST(TimeZone, NamedTimeZones) {
@@ -911,19 +916,19 @@ TEST(MakeTime, TimePointResolution) {
   const time_zone utc = utc_time_zone();
   const time_point<chrono::nanoseconds> tp_ns =
       convert(civil_second(2015, 1, 2, 3, 4, 5), utc);
-  EXPECT_EQ("04:05", format("%M:%E*S", tp_ns, utc));
+  EXPECT_EQ("04:05", absl::time_internal::cctz::format("%M:%E*S", tp_ns, utc));
   const time_point<chrono::microseconds> tp_us =
       convert(civil_second(2015, 1, 2, 3, 4, 5), utc);
-  EXPECT_EQ("04:05", format("%M:%E*S", tp_us, utc));
+  EXPECT_EQ("04:05", absl::time_internal::cctz::format("%M:%E*S", tp_us, utc));
   const time_point<chrono::milliseconds> tp_ms =
       convert(civil_second(2015, 1, 2, 3, 4, 5), utc);
-  EXPECT_EQ("04:05", format("%M:%E*S", tp_ms, utc));
+  EXPECT_EQ("04:05", absl::time_internal::cctz::format("%M:%E*S", tp_ms, utc));
   const time_point<chrono::seconds> tp_s =
       convert(civil_second(2015, 1, 2, 3, 4, 5), utc);
-  EXPECT_EQ("04:05", format("%M:%E*S", tp_s, utc));
+  EXPECT_EQ("04:05", absl::time_internal::cctz::format("%M:%E*S", tp_s, utc));
   const time_point<absl::time_internal::cctz::seconds> tp_s64 =
       convert(civil_second(2015, 1, 2, 3, 4, 5), utc);
-  EXPECT_EQ("04:05", format("%M:%E*S", tp_s64, utc));
+  EXPECT_EQ("04:05", absl::time_internal::cctz::format("%M:%E*S", tp_s64, utc));
 
   // These next two require chrono::time_point_cast because the conversion
   // from a resolution of seconds (the return value of convert()) to a
@@ -931,10 +936,10 @@ TEST(MakeTime, TimePointResolution) {
   const time_point<chrono::minutes> tp_m =
       chrono::time_point_cast<chrono::minutes>(
           convert(civil_second(2015, 1, 2, 3, 4, 5), utc));
-  EXPECT_EQ("04:00", format("%M:%E*S", tp_m, utc));
+  EXPECT_EQ("04:00", absl::time_internal::cctz::format("%M:%E*S", tp_m, utc));
   const time_point<chrono::hours> tp_h = chrono::time_point_cast<chrono::hours>(
       convert(civil_second(2015, 1, 2, 3, 4, 5), utc));
-  EXPECT_EQ("00:00", format("%M:%E*S", tp_h, utc));
+  EXPECT_EQ("00:00", absl::time_internal::cctz::format("%M:%E*S", tp_h, utc));
 }
 
 TEST(MakeTime, Normalization) {
@@ -960,9 +965,11 @@ TEST(MakeTime, SysSecondsLimits) {
 
   // Approach the maximal time_point<cctz::seconds> value from below.
   tp = convert(civil_second(292277026596, 12, 4, 15, 30, 6), utc);
-  EXPECT_EQ("292277026596-12-04T15:30:06+00:00", format(RFC3339, tp, utc));
+  EXPECT_EQ("292277026596-12-04T15:30:06+00:00",
+            absl::time_internal::cctz::format(RFC3339, tp, utc));
   tp = convert(civil_second(292277026596, 12, 4, 15, 30, 7), utc);
-  EXPECT_EQ("292277026596-12-04T15:30:07+00:00", format(RFC3339, tp, utc));
+  EXPECT_EQ("292277026596-12-04T15:30:07+00:00",
+            absl::time_internal::cctz::format(RFC3339, tp, utc));
   EXPECT_EQ(time_point<absl::time_internal::cctz::seconds>::max(), tp);
   tp = convert(civil_second(292277026596, 12, 4, 15, 30, 8), utc);
   EXPECT_EQ(time_point<absl::time_internal::cctz::seconds>::max(), tp);
@@ -971,7 +978,8 @@ TEST(MakeTime, SysSecondsLimits) {
 
   // Checks that we can also get the maximal value for a far-east zone.
   tp = convert(civil_second(292277026596, 12, 5, 5, 30, 7), east);
-  EXPECT_EQ("292277026596-12-05T05:30:07+14:00", format(RFC3339, tp, east));
+  EXPECT_EQ("292277026596-12-05T05:30:07+14:00",
+            absl::time_internal::cctz::format(RFC3339, tp, east));
   EXPECT_EQ(time_point<absl::time_internal::cctz::seconds>::max(), tp);
   tp = convert(civil_second(292277026596, 12, 5, 5, 30, 8), east);
   EXPECT_EQ(time_point<absl::time_internal::cctz::seconds>::max(), tp);
@@ -980,7 +988,8 @@ TEST(MakeTime, SysSecondsLimits) {
 
   // Checks that we can also get the maximal value for a far-west zone.
   tp = convert(civil_second(292277026596, 12, 4, 1, 30, 7), west);
-  EXPECT_EQ("292277026596-12-04T01:30:07-14:00", format(RFC3339, tp, west));
+  EXPECT_EQ("292277026596-12-04T01:30:07-14:00",
+            absl::time_internal::cctz::format(RFC3339, tp, west));
   EXPECT_EQ(time_point<absl::time_internal::cctz::seconds>::max(), tp);
   tp = convert(civil_second(292277026596, 12, 4, 7, 30, 8), west);
   EXPECT_EQ(time_point<absl::time_internal::cctz::seconds>::max(), tp);
@@ -989,9 +998,11 @@ TEST(MakeTime, SysSecondsLimits) {
 
   // Approach the minimal time_point<cctz::seconds> value from above.
   tp = convert(civil_second(-292277022657, 1, 27, 8, 29, 53), utc);
-  EXPECT_EQ("-292277022657-01-27T08:29:53+00:00", format(RFC3339, tp, utc));
+  EXPECT_EQ("-292277022657-01-27T08:29:53+00:00",
+            absl::time_internal::cctz::format(RFC3339, tp, utc));
   tp = convert(civil_second(-292277022657, 1, 27, 8, 29, 52), utc);
-  EXPECT_EQ("-292277022657-01-27T08:29:52+00:00", format(RFC3339, tp, utc));
+  EXPECT_EQ("-292277022657-01-27T08:29:52+00:00",
+            absl::time_internal::cctz::format(RFC3339, tp, utc));
   EXPECT_EQ(time_point<absl::time_internal::cctz::seconds>::min(), tp);
   tp = convert(civil_second(-292277022657, 1, 27, 8, 29, 51), utc);
   EXPECT_EQ(time_point<absl::time_internal::cctz::seconds>::min(), tp);
@@ -1000,7 +1011,8 @@ TEST(MakeTime, SysSecondsLimits) {
 
   // Checks that we can also get the minimal value for a far-east zone.
   tp = convert(civil_second(-292277022657, 1, 27, 22, 29, 52), east);
-  EXPECT_EQ("-292277022657-01-27T22:29:52+14:00", format(RFC3339, tp, east));
+  EXPECT_EQ("-292277022657-01-27T22:29:52+14:00",
+            absl::time_internal::cctz::format(RFC3339, tp, east));
   EXPECT_EQ(time_point<absl::time_internal::cctz::seconds>::min(), tp);
   tp = convert(civil_second(-292277022657, 1, 27, 22, 29, 51), east);
   EXPECT_EQ(time_point<absl::time_internal::cctz::seconds>::min(), tp);
@@ -1009,7 +1021,8 @@ TEST(MakeTime, SysSecondsLimits) {
 
   // Checks that we can also get the minimal value for a far-west zone.
   tp = convert(civil_second(-292277022657, 1, 26, 18, 29, 52), west);
-  EXPECT_EQ("-292277022657-01-26T18:29:52-14:00", format(RFC3339, tp, west));
+  EXPECT_EQ("-292277022657-01-26T18:29:52-14:00",
+            absl::time_internal::cctz::format(RFC3339, tp, west));
   EXPECT_EQ(time_point<absl::time_internal::cctz::seconds>::min(), tp);
   tp = convert(civil_second(-292277022657, 1, 26, 18, 29, 51), west);
   EXPECT_EQ(time_point<absl::time_internal::cctz::seconds>::min(), tp);
@@ -1026,17 +1039,19 @@ TEST(MakeTime, SysSecondsLimits) {
     const time_zone cut = LoadZone("libc:UTC");
     const year_t max_tm_year = year_t{std::numeric_limits<int>::max()} + 1900;
     tp = convert(civil_second(max_tm_year, 12, 31, 23, 59, 59), cut);
-#if defined(__FreeBSD__) || defined(__OpenBSD__)
-    // The BSD gmtime_r() fails on extreme positive tm_year values.
+#if defined(__FreeBSD__) || defined(__OpenBSD__) || defined(__EMSCRIPTEN__)
+    // Some gmtime_r() impls fail on extreme positive values.
 #else
-    EXPECT_EQ("2147485547-12-31T23:59:59+00:00", format(RFC3339, tp, cut));
+    EXPECT_EQ("2147485547-12-31T23:59:59+00:00",
+              absl::time_internal::cctz::format(RFC3339, tp, cut));
 #endif
     const year_t min_tm_year = year_t{std::numeric_limits<int>::min()} + 1900;
     tp = convert(civil_second(min_tm_year, 1, 1, 0, 0, 0), cut);
-#if defined(__Fuchsia__)
-    // Fuchsia's gmtime_r() fails on extreme negative values (fxbug.dev/78527).
+#if defined(__Fuchsia__) || defined(__EMSCRIPTEN__)
+    // Some gmtime_r() impls fail on extreme negative values (fxbug.dev/78527).
 #else
-    EXPECT_EQ("-2147481748-01-01T00:00:00+00:00", format(RFC3339, tp, cut));
+    EXPECT_EQ("-2147481748-01-01T00:00:00+00:00",
+              absl::time_internal::cctz::format(RFC3339, tp, cut));
 #endif
 #endif
   }
@@ -1062,7 +1077,7 @@ TEST(MakeTime, LocalTimeLibC) {
          tp = zi.lookup(transition.to).trans) {
       const auto fcl = zi.lookup(transition.from);
       const auto tcl = zi.lookup(transition.to);
-      civil_second cs;  // compare cs in zi and lc
+      civil_second cs, us;  // compare cs and us in zi and lc
       if (fcl.kind == time_zone::civil_lookup::UNIQUE) {
         if (tcl.kind == time_zone::civil_lookup::UNIQUE) {
           // Both unique; must be an is_dst or abbr change.
@@ -1078,12 +1093,14 @@ TEST(MakeTime, LocalTimeLibC) {
         }
         ASSERT_EQ(time_zone::civil_lookup::REPEATED, tcl.kind);
         cs = transition.to;
+        us = transition.from;
       } else {
         ASSERT_EQ(time_zone::civil_lookup::UNIQUE, tcl.kind);
         ASSERT_EQ(time_zone::civil_lookup::SKIPPED, fcl.kind);
         cs = transition.from;
+        us = transition.to;
       }
-      if (cs.year() > 2037) break;  // limit test time (and to 32-bit time_t)
+      if (us.year() > 2037) break;  // limit test time (and to 32-bit time_t)
       const auto cl_zi = zi.lookup(cs);
       if (zi.lookup(cl_zi.pre).is_dst == zi.lookup(cl_zi.post).is_dst) {
         // The "libc" implementation cannot correctly classify transitions
@@ -1115,6 +1132,13 @@ TEST(MakeTime, LocalTimeLibC) {
       EXPECT_EQ(cl_zi.pre, cl_lc.pre);
       EXPECT_EQ(cl_zi.trans, cl_lc.trans);
       EXPECT_EQ(cl_zi.post, cl_lc.post);
+      const auto ucl_zi = zi.lookup(us);
+      const auto ucl_lc = lc.lookup(us);
+      SCOPED_TRACE(testing::Message() << "For " << us << " in " << *np);
+      EXPECT_EQ(ucl_zi.kind, ucl_lc.kind);
+      EXPECT_EQ(ucl_zi.pre, ucl_lc.pre);
+      EXPECT_EQ(ucl_zi.trans, ucl_lc.trans);
+      EXPECT_EQ(ucl_zi.post, ucl_lc.post);
     }
   }
   if (ep == nullptr) {
diff --git a/absl/time/internal/cctz/src/time_zone_posix.h b/absl/time/internal/cctz/src/time_zone_posix.h
index 0cf29055..7fd2b9ec 100644
--- a/absl/time/internal/cctz/src/time_zone_posix.h
+++ b/absl/time/internal/cctz/src/time_zone_posix.h
@@ -104,7 +104,7 @@ struct PosixTransition {
 
 // The entirety of a POSIX-string specified time-zone rule. The standard
 // abbreviation and offset are always given. If the time zone includes
-// daylight saving, then the daylight abbrevation is non-empty and the
+// daylight saving, then the daylight abbreviation is non-empty and the
 // remaining fields are also valid. Note that the start/end transitions
 // are not ordered---in the southern hemisphere the transition to end
 // daylight time occurs first in any particular year.
diff --git a/absl/time/internal/cctz/src/tzfile.h b/absl/time/internal/cctz/src/tzfile.h
index 31e85982..9613055d 100644
--- a/absl/time/internal/cctz/src/tzfile.h
+++ b/absl/time/internal/cctz/src/tzfile.h
@@ -102,20 +102,24 @@ struct tzhead {
 */
 
 #ifndef TZ_MAX_TIMES
+/* This must be at least 242 for Europe/London with 'zic -b fat'.  */
 #define TZ_MAX_TIMES 2000
 #endif /* !defined TZ_MAX_TIMES */
 
 #ifndef TZ_MAX_TYPES
-/* This must be at least 17 for Europe/Samara and Europe/Vilnius.  */
+/* This must be at least 18 for Europe/Vilnius with 'zic -b fat'.  */
 #define TZ_MAX_TYPES 256 /* Limited by what (unsigned char)'s can hold */
 #endif                   /* !defined TZ_MAX_TYPES */
 
 #ifndef TZ_MAX_CHARS
+/* This must be at least 40 for America/Anchorage.  */
 #define TZ_MAX_CHARS 50 /* Maximum number of abbreviation characters */
                         /* (limited by what unsigned chars can hold) */
 #endif                  /* !defined TZ_MAX_CHARS */
 
 #ifndef TZ_MAX_LEAPS
+/* This must be at least 27 for leap seconds from 1972 through mid-2023.
+   There's a plan to discontinue leap seconds by 2035.  */
 #define TZ_MAX_LEAPS 50 /* Maximum number of leap second corrections */
 #endif                  /* !defined TZ_MAX_LEAPS */
 
diff --git a/absl/time/internal/cctz/src/zone_info_source.cc b/absl/time/internal/cctz/src/zone_info_source.cc
index 1b162337..9bc8197b 100644
--- a/absl/time/internal/cctz/src/zone_info_source.cc
+++ b/absl/time/internal/cctz/src/zone_info_source.cc
@@ -67,41 +67,41 @@ extern ZoneInfoSourceFactory zone_info_source_factory;
 extern ZoneInfoSourceFactory default_factory;
 ZoneInfoSourceFactory default_factory = DefaultFactory;
 #if defined(_M_IX86) || defined(_M_ARM)
-#pragma comment(                                                                                                                 \
-        linker,                                                                                                                  \
-            "/alternatename:?zone_info_source_factory@cctz_extension@time_internal@" ABSL_INTERNAL_MANGLED_NS                    \
-            "@@3P6A?AV?$unique_ptr@VZoneInfoSource@cctz@time_internal@" ABSL_INTERNAL_MANGLED_NS                                 \
-            "@@U?$default_delete@VZoneInfoSource@cctz@time_internal@" ABSL_INTERNAL_MANGLED_NS                                   \
-            "@@@std@@@std@@ABV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@" ABSL_INTERNAL_MANGLED_BACKREFERENCE      \
-            "@ABV?$function@$$A6A?AV?$unique_ptr@VZoneInfoSource@cctz@time_internal@" ABSL_INTERNAL_MANGLED_NS                   \
-            "@@U?$default_delete@VZoneInfoSource@cctz@time_internal@" ABSL_INTERNAL_MANGLED_NS                                   \
-            "@@@std@@@std@@ABV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@2@@Z@" ABSL_INTERNAL_MANGLED_BACKREFERENCE \
-            "@@ZA=?default_factory@cctz_extension@time_internal@" ABSL_INTERNAL_MANGLED_NS                                       \
-            "@@3P6A?AV?$unique_ptr@VZoneInfoSource@cctz@time_internal@" ABSL_INTERNAL_MANGLED_NS                                 \
-            "@@U?$default_delete@VZoneInfoSource@cctz@time_internal@" ABSL_INTERNAL_MANGLED_NS                                   \
-            "@@@std@@@std@@ABV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@" ABSL_INTERNAL_MANGLED_BACKREFERENCE      \
-            "@ABV?$function@$$A6A?AV?$unique_ptr@VZoneInfoSource@cctz@time_internal@" ABSL_INTERNAL_MANGLED_NS                   \
-            "@@U?$default_delete@VZoneInfoSource@cctz@time_internal@" ABSL_INTERNAL_MANGLED_NS                                   \
-            "@@@std@@@std@@ABV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@2@@Z@" ABSL_INTERNAL_MANGLED_BACKREFERENCE \
-            "@@ZA")
+#pragma comment(                                                                                                         \
+    linker,                                                                                                              \
+    "/alternatename:?zone_info_source_factory@cctz_extension@time_internal@" ABSL_INTERNAL_MANGLED_NS                    \
+    "@@3P6A?AV?$unique_ptr@VZoneInfoSource@cctz@time_internal@" ABSL_INTERNAL_MANGLED_NS                                 \
+    "@@U?$default_delete@VZoneInfoSource@cctz@time_internal@" ABSL_INTERNAL_MANGLED_NS                                   \
+    "@@@std@@@std@@ABV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@" ABSL_INTERNAL_MANGLED_BACKREFERENCE      \
+    "@ABV?$function@$$A6A?AV?$unique_ptr@VZoneInfoSource@cctz@time_internal@" ABSL_INTERNAL_MANGLED_NS                   \
+    "@@U?$default_delete@VZoneInfoSource@cctz@time_internal@" ABSL_INTERNAL_MANGLED_NS                                   \
+    "@@@std@@@std@@ABV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@2@@Z@" ABSL_INTERNAL_MANGLED_BACKREFERENCE \
+    "@@ZA=?default_factory@cctz_extension@time_internal@" ABSL_INTERNAL_MANGLED_NS                                       \
+    "@@3P6A?AV?$unique_ptr@VZoneInfoSource@cctz@time_internal@" ABSL_INTERNAL_MANGLED_NS                                 \
+    "@@U?$default_delete@VZoneInfoSource@cctz@time_internal@" ABSL_INTERNAL_MANGLED_NS                                   \
+    "@@@std@@@std@@ABV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@" ABSL_INTERNAL_MANGLED_BACKREFERENCE      \
+    "@ABV?$function@$$A6A?AV?$unique_ptr@VZoneInfoSource@cctz@time_internal@" ABSL_INTERNAL_MANGLED_NS                   \
+    "@@U?$default_delete@VZoneInfoSource@cctz@time_internal@" ABSL_INTERNAL_MANGLED_NS                                   \
+    "@@@std@@@std@@ABV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@2@@Z@" ABSL_INTERNAL_MANGLED_BACKREFERENCE \
+    "@@ZA")
 #elif defined(_M_IA_64) || defined(_M_AMD64) || defined(_M_ARM64)
-#pragma comment(                                                                                                                  \
-        linker,                                                                                                                   \
-            "/alternatename:?zone_info_source_factory@cctz_extension@time_internal@" ABSL_INTERNAL_MANGLED_NS                     \
-            "@@3P6A?AV?$unique_ptr@VZoneInfoSource@cctz@time_internal@" ABSL_INTERNAL_MANGLED_NS                                  \
-            "@@U?$default_delete@VZoneInfoSource@cctz@time_internal@" ABSL_INTERNAL_MANGLED_NS                                    \
-            "@@@std@@@std@@AEBV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@" ABSL_INTERNAL_MANGLED_BACKREFERENCE      \
-            "@AEBV?$function@$$A6A?AV?$unique_ptr@VZoneInfoSource@cctz@time_internal@" ABSL_INTERNAL_MANGLED_NS                   \
-            "@@U?$default_delete@VZoneInfoSource@cctz@time_internal@" ABSL_INTERNAL_MANGLED_NS                                    \
-            "@@@std@@@std@@AEBV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@2@@Z@" ABSL_INTERNAL_MANGLED_BACKREFERENCE \
-            "@@ZEA=?default_factory@cctz_extension@time_internal@" ABSL_INTERNAL_MANGLED_NS                                       \
-            "@@3P6A?AV?$unique_ptr@VZoneInfoSource@cctz@time_internal@" ABSL_INTERNAL_MANGLED_NS                                  \
-            "@@U?$default_delete@VZoneInfoSource@cctz@time_internal@" ABSL_INTERNAL_MANGLED_NS                                    \
-            "@@@std@@@std@@AEBV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@" ABSL_INTERNAL_MANGLED_BACKREFERENCE      \
-            "@AEBV?$function@$$A6A?AV?$unique_ptr@VZoneInfoSource@cctz@time_internal@" ABSL_INTERNAL_MANGLED_NS                   \
-            "@@U?$default_delete@VZoneInfoSource@cctz@time_internal@" ABSL_INTERNAL_MANGLED_NS                                    \
-            "@@@std@@@std@@AEBV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@2@@Z@" ABSL_INTERNAL_MANGLED_BACKREFERENCE \
-            "@@ZEA")
+#pragma comment(                                                                                                          \
+    linker,                                                                                                               \
+    "/alternatename:?zone_info_source_factory@cctz_extension@time_internal@" ABSL_INTERNAL_MANGLED_NS                     \
+    "@@3P6A?AV?$unique_ptr@VZoneInfoSource@cctz@time_internal@" ABSL_INTERNAL_MANGLED_NS                                  \
+    "@@U?$default_delete@VZoneInfoSource@cctz@time_internal@" ABSL_INTERNAL_MANGLED_NS                                    \
+    "@@@std@@@std@@AEBV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@" ABSL_INTERNAL_MANGLED_BACKREFERENCE      \
+    "@AEBV?$function@$$A6A?AV?$unique_ptr@VZoneInfoSource@cctz@time_internal@" ABSL_INTERNAL_MANGLED_NS                   \
+    "@@U?$default_delete@VZoneInfoSource@cctz@time_internal@" ABSL_INTERNAL_MANGLED_NS                                    \
+    "@@@std@@@std@@AEBV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@2@@Z@" ABSL_INTERNAL_MANGLED_BACKREFERENCE \
+    "@@ZEA=?default_factory@cctz_extension@time_internal@" ABSL_INTERNAL_MANGLED_NS                                       \
+    "@@3P6A?AV?$unique_ptr@VZoneInfoSource@cctz@time_internal@" ABSL_INTERNAL_MANGLED_NS                                  \
+    "@@U?$default_delete@VZoneInfoSource@cctz@time_internal@" ABSL_INTERNAL_MANGLED_NS                                    \
+    "@@@std@@@std@@AEBV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@" ABSL_INTERNAL_MANGLED_BACKREFERENCE      \
+    "@AEBV?$function@$$A6A?AV?$unique_ptr@VZoneInfoSource@cctz@time_internal@" ABSL_INTERNAL_MANGLED_NS                   \
+    "@@U?$default_delete@VZoneInfoSource@cctz@time_internal@" ABSL_INTERNAL_MANGLED_NS                                    \
+    "@@@std@@@std@@AEBV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@2@@Z@" ABSL_INTERNAL_MANGLED_BACKREFERENCE \
+    "@@ZEA")
 #else
 #error Unsupported MSVC platform
 #endif  // _M_<PLATFORM>
diff --git a/absl/time/internal/cctz/testdata/version b/absl/time/internal/cctz/testdata/version
index b74fa117..7daa77e0 100644
--- a/absl/time/internal/cctz/testdata/version
+++ b/absl/time/internal/cctz/testdata/version
@@ -1 +1 @@
-2022g
+2023c
diff --git a/absl/time/internal/cctz/testdata/zoneinfo/Africa/Cairo b/absl/time/internal/cctz/testdata/zoneinfo/Africa/Cairo
index ea38c970..1e6d48d1 100644
--- a/absl/time/internal/cctz/testdata/zoneinfo/Africa/Cairo
+++ b/absl/time/internal/cctz/testdata/zoneinfo/Africa/Cairo
diff --git a/absl/time/internal/cctz/testdata/zoneinfo/Africa/Casablanca b/absl/time/internal/cctz/testdata/zoneinfo/Africa/Casablanca
index 0263c90b..240ebb2b 100644
--- a/absl/time/internal/cctz/testdata/zoneinfo/Africa/Casablanca
+++ b/absl/time/internal/cctz/testdata/zoneinfo/Africa/Casablanca
diff --git a/absl/time/internal/cctz/testdata/zoneinfo/Africa/El_Aaiun b/absl/time/internal/cctz/testdata/zoneinfo/Africa/El_Aaiun
index 772e23c4..909c5f96 100644
--- a/absl/time/internal/cctz/testdata/zoneinfo/Africa/El_Aaiun
+++ b/absl/time/internal/cctz/testdata/zoneinfo/Africa/El_Aaiun
diff --git a/absl/time/internal/cctz/testdata/zoneinfo/America/Godthab b/absl/time/internal/cctz/testdata/zoneinfo/America/Godthab
index 79d7a454..00b57bb1 100644
--- a/absl/time/internal/cctz/testdata/zoneinfo/America/Godthab
+++ b/absl/time/internal/cctz/testdata/zoneinfo/America/Godthab
diff --git a/absl/time/internal/cctz/testdata/zoneinfo/America/Nuuk b/absl/time/internal/cctz/testdata/zoneinfo/America/Nuuk
index 79d7a454..00b57bb1 100644
--- a/absl/time/internal/cctz/testdata/zoneinfo/America/Nuuk
+++ b/absl/time/internal/cctz/testdata/zoneinfo/America/Nuuk
diff --git a/absl/time/internal/cctz/testdata/zoneinfo/America/Yellowknife b/absl/time/internal/cctz/testdata/zoneinfo/America/Yellowknife
index ff3eb878..645ee945 100644
--- a/absl/time/internal/cctz/testdata/zoneinfo/America/Yellowknife
+++ b/absl/time/internal/cctz/testdata/zoneinfo/America/Yellowknife
diff --git a/absl/time/internal/cctz/testdata/zoneinfo/Asia/Gaza b/absl/time/internal/cctz/testdata/zoneinfo/Asia/Gaza
index bed968e7..7e833898 100644
--- a/absl/time/internal/cctz/testdata/zoneinfo/Asia/Gaza
+++ b/absl/time/internal/cctz/testdata/zoneinfo/Asia/Gaza
diff --git a/absl/time/internal/cctz/testdata/zoneinfo/Asia/Hebron b/absl/time/internal/cctz/testdata/zoneinfo/Asia/Hebron
index 3ce1bac6..fcf923bd 100644
--- a/absl/time/internal/cctz/testdata/zoneinfo/Asia/Hebron
+++ b/absl/time/internal/cctz/testdata/zoneinfo/Asia/Hebron
diff --git a/absl/time/internal/cctz/testdata/zoneinfo/Egypt b/absl/time/internal/cctz/testdata/zoneinfo/Egypt
index ea38c970..1e6d48d1 100644
--- a/absl/time/internal/cctz/testdata/zoneinfo/Egypt
+++ b/absl/time/internal/cctz/testdata/zoneinfo/Egypt
diff --git a/absl/time/internal/cctz/testdata/zoneinfo/Europe/Kirov b/absl/time/internal/cctz/testdata/zoneinfo/Europe/Kirov
index d1c93c54..bfac5611 100644
--- a/absl/time/internal/cctz/testdata/zoneinfo/Europe/Kirov
+++ b/absl/time/internal/cctz/testdata/zoneinfo/Europe/Kirov
diff --git a/absl/time/internal/cctz/testdata/zoneinfo/Europe/Volgograd b/absl/time/internal/cctz/testdata/zoneinfo/Europe/Volgograd
index c5170026..0715d58b 100644
--- a/absl/time/internal/cctz/testdata/zoneinfo/Europe/Volgograd
+++ b/absl/time/internal/cctz/testdata/zoneinfo/Europe/Volgograd
diff --git a/absl/time/internal/cctz/testdata/zoneinfo/iso3166.tab b/absl/time/internal/cctz/testdata/zoneinfo/iso3166.tab
index 911af5e8..be3348d1 100644
--- a/absl/time/internal/cctz/testdata/zoneinfo/iso3166.tab
+++ b/absl/time/internal/cctz/testdata/zoneinfo/iso3166.tab
@@ -238,7 +238,7 @@ SY	Syria
 SZ	Eswatini (Swaziland)
 TC	Turks & Caicos Is
 TD	Chad
-TF	French Southern Territories
+TF	French S. Terr.
 TG	Togo
 TH	Thailand
 TJ	Tajikistan
diff --git a/absl/time/internal/cctz/testdata/zoneinfo/zone1970.tab b/absl/time/internal/cctz/testdata/zoneinfo/zone1970.tab
index a9b36d36..1f1cecb8 100644
--- a/absl/time/internal/cctz/testdata/zoneinfo/zone1970.tab
+++ b/absl/time/internal/cctz/testdata/zoneinfo/zone1970.tab
@@ -18,7 +18,10 @@
 #     Please see the theory.html file for how these names are chosen.
 #     If multiple timezones overlap a country, each has a row in the
 #     table, with each column 1 containing the country code.
-# 4.  Comments; present if and only if a country has multiple timezones.
+# 4.  Comments; present if and only if countries have multiple timezones,
+#     and useful only for those countries.  For example, the comments
+#     for the row with countries CH,DE,LI and name Europe/Zurich
+#     are useful only for DE, since CH and LI have no other timezones.
 #
 # If a timezone covers multiple countries, the most-populous city is used,
 # and that country is listed first in column 1; any other countries
@@ -34,7 +37,7 @@
 #country-
 #codes	coordinates	TZ	comments
 AD	+4230+00131	Europe/Andorra
-AE,OM,RE,SC,TF	+2518+05518	Asia/Dubai	UAE, Oman, Réunion, Seychelles, Crozet, Scattered Is
+AE,OM,RE,SC,TF	+2518+05518	Asia/Dubai	Crozet, Scattered Is
 AF	+3431+06912	Asia/Kabul
 AL	+4120+01950	Europe/Tirane
 AM	+4011+04430	Asia/Yerevan
@@ -45,7 +48,7 @@ AQ	-6448-06406	Antarctica/Palmer	Palmer
 AQ	-6734-06808	Antarctica/Rothera	Rothera
 AQ	-720041+0023206	Antarctica/Troll	Troll
 AR	-3436-05827	America/Argentina/Buenos_Aires	Buenos Aires (BA, CF)
-AR	-3124-06411	America/Argentina/Cordoba	Argentina (most areas: CB, CC, CN, ER, FM, MN, SE, SF)
+AR	-3124-06411	America/Argentina/Cordoba	most areas: CB, CC, CN, ER, FM, MN, SE, SF
 AR	-2447-06525	America/Argentina/Salta	Salta (SA, LP, NQ, RN)
 AR	-2411-06518	America/Argentina/Jujuy	Jujuy (JY)
 AR	-2649-06513	America/Argentina/Tucuman	Tucumán (TM)
@@ -56,7 +59,7 @@ AR	-3253-06849	America/Argentina/Mendoza	Mendoza (MZ)
 AR	-3319-06621	America/Argentina/San_Luis	San Luis (SL)
 AR	-5138-06913	America/Argentina/Rio_Gallegos	Santa Cruz (SC)
 AR	-5448-06818	America/Argentina/Ushuaia	Tierra del Fuego (TF)
-AS,UM	-1416-17042	Pacific/Pago_Pago	Samoa, Midway
+AS,UM	-1416-17042	Pacific/Pago_Pago	Midway
 AT	+4813+01620	Europe/Vienna
 AU	-3133+15905	Australia/Lord_Howe	Lord Howe Island
 AU	-5430+15857	Antarctica/Macquarie	Macquarie Island
@@ -101,26 +104,25 @@ CA	+4439-06336	America/Halifax	Atlantic - NS (most areas); PE
 CA	+4612-05957	America/Glace_Bay	Atlantic - NS (Cape Breton)
 CA	+4606-06447	America/Moncton	Atlantic - New Brunswick
 CA	+5320-06025	America/Goose_Bay	Atlantic - Labrador (most areas)
-CA,BS	+4339-07923	America/Toronto	Eastern - ON, QC (most areas), Bahamas
+CA,BS	+4339-07923	America/Toronto	Eastern - ON, QC (most areas)
 CA	+6344-06828	America/Iqaluit	Eastern - NU (most areas)
 CA	+4953-09709	America/Winnipeg	Central - ON (west); Manitoba
 CA	+744144-0944945	America/Resolute	Central - NU (Resolute)
 CA	+624900-0920459	America/Rankin_Inlet	Central - NU (central)
 CA	+5024-10439	America/Regina	CST - SK (most areas)
 CA	+5017-10750	America/Swift_Current	CST - SK (midwest)
-CA	+5333-11328	America/Edmonton	Mountain - AB; BC (E); SK (W)
+CA	+5333-11328	America/Edmonton	Mountain - AB; BC (E); NT (E); SK (W)
 CA	+690650-1050310	America/Cambridge_Bay	Mountain - NU (west)
-CA	+6227-11421	America/Yellowknife	Mountain - NT (central)
 CA	+682059-1334300	America/Inuvik	Mountain - NT (west)
 CA	+5546-12014	America/Dawson_Creek	MST - BC (Dawson Cr, Ft St John)
 CA	+5848-12242	America/Fort_Nelson	MST - BC (Ft Nelson)
 CA	+6043-13503	America/Whitehorse	MST - Yukon (east)
 CA	+6404-13925	America/Dawson	MST - Yukon (west)
 CA	+4916-12307	America/Vancouver	Pacific - BC (most areas)
-CH,DE,LI	+4723+00832	Europe/Zurich	Swiss time
+CH,DE,LI	+4723+00832	Europe/Zurich	Büsingen
 CI,BF,GH,GM,GN,IS,ML,MR,SH,SL,SN,TG	+0519-00402	Africa/Abidjan
 CK	-2114-15946	Pacific/Rarotonga
-CL	-3327-07040	America/Santiago	Chile (most areas)
+CL	-3327-07040	America/Santiago	most of Chile
 CL	-5309-07055	America/Punta_Arenas	Region of Magallanes
 CL	-2709-10926	Pacific/Easter	Easter Island
 CN	+3114+12128	Asia/Shanghai	Beijing Time
@@ -129,10 +131,10 @@ CO	+0436-07405	America/Bogota
 CR	+0956-08405	America/Costa_Rica
 CU	+2308-08222	America/Havana
 CV	+1455-02331	Atlantic/Cape_Verde
-CY	+3510+03322	Asia/Nicosia	Cyprus (most areas)
+CY	+3510+03322	Asia/Nicosia	most of Cyprus
 CY	+3507+03357	Asia/Famagusta	Northern Cyprus
 CZ,SK	+5005+01426	Europe/Prague
-DE,DK,NO,SE,SJ	+5230+01322	Europe/Berlin	Germany (most areas), Scandinavia
+DE,DK,NO,SE,SJ	+5230+01322	Europe/Berlin	most of Germany
 DO	+1828-06954	America/Santo_Domingo
 DZ	+3647+00303	Africa/Algiers
 EC	-0210-07950	America/Guayaquil	Ecuador (mainland)
@@ -153,7 +155,7 @@ GB,GG,IM,JE	+513030-0000731	Europe/London
 GE	+4143+04449	Asia/Tbilisi
 GF	+0456-05220	America/Cayenne
 GI	+3608-00521	Europe/Gibraltar
-GL	+6411-05144	America/Nuuk	Greenland (most areas)
+GL	+6411-05144	America/Nuuk	most of Greenland
 GL	+7646-01840	America/Danmarkshavn	National Park (east coast)
 GL	+7029-02158	America/Scoresbysund	Scoresbysund/Ittoqqortoormiit
 GL	+7634-06847	America/Thule	Thule/Pituffik
@@ -183,12 +185,12 @@ JO	+3157+03556	Asia/Amman
 JP	+353916+1394441	Asia/Tokyo
 KE,DJ,ER,ET,KM,MG,SO,TZ,UG,YT	-0117+03649	Africa/Nairobi
 KG	+4254+07436	Asia/Bishkek
-KI,MH,TV,UM,WF	+0125+17300	Pacific/Tarawa	Gilberts, Marshalls, Tuvalu, Wallis & Futuna, Wake
+KI,MH,TV,UM,WF	+0125+17300	Pacific/Tarawa	Gilberts, Marshalls, Wake
 KI	-0247-17143	Pacific/Kanton	Phoenix Islands
 KI	+0152-15720	Pacific/Kiritimati	Line Islands
 KP	+3901+12545	Asia/Pyongyang
 KR	+3733+12658	Asia/Seoul
-KZ	+4315+07657	Asia/Almaty	Kazakhstan (most areas)
+KZ	+4315+07657	Asia/Almaty	most of Kazakhstan
 KZ	+4448+06528	Asia/Qyzylorda	Qyzylorda/Kyzylorda/Kzyl-Orda
 KZ	+5312+06337	Asia/Qostanay	Qostanay/Kostanay/Kustanay
 KZ	+5017+05710	Asia/Aqtobe	Aqtöbe/Aktobe
@@ -205,14 +207,14 @@ MA	+3339-00735	Africa/Casablanca
 MD	+4700+02850	Europe/Chisinau
 MH	+0905+16720	Pacific/Kwajalein	Kwajalein
 MM,CC	+1647+09610	Asia/Yangon
-MN	+4755+10653	Asia/Ulaanbaatar	Mongolia (most areas)
+MN	+4755+10653	Asia/Ulaanbaatar	most of Mongolia
 MN	+4801+09139	Asia/Hovd	Bayan-Ölgii, Govi-Altai, Hovd, Uvs, Zavkhan
 MN	+4804+11430	Asia/Choibalsan	Dornod, Sükhbaatar
 MO	+221150+1133230	Asia/Macau
 MQ	+1436-06105	America/Martinique
 MT	+3554+01431	Europe/Malta
 MU	-2010+05730	Indian/Mauritius
-MV,TF	+0410+07330	Indian/Maldives	Maldives, Kerguelen, St Paul I, Amsterdam I
+MV,TF	+0410+07330	Indian/Maldives	Kerguelen, St Paul I, Amsterdam I
 MX	+1924-09909	America/Mexico_City	Central Mexico
 MX	+2105-08646	America/Cancun	Quintana Roo
 MX	+2058-08937	America/Merida	Campeche, Yucatán
@@ -225,7 +227,7 @@ MX	+2313-10625	America/Mazatlan	Baja California Sur, Nayarit (most areas), Sinal
 MX	+2048-10515	America/Bahia_Banderas	Bahía de Banderas
 MX	+2904-11058	America/Hermosillo	Sonora
 MX	+3232-11701	America/Tijuana	Baja California
-MY,BN	+0133+11020	Asia/Kuching	Sabah, Sarawak, Brunei
+MY,BN	+0133+11020	Asia/Kuching	Sabah, Sarawak
 MZ,BI,BW,CD,MW,RW,ZM,ZW	-2558+03235	Africa/Maputo	Central Africa Time
 NA	-2234+01706	Africa/Windhoek
 NC	-2216+16627	Pacific/Noumea
@@ -237,7 +239,7 @@ NR	-0031+16655	Pacific/Nauru
 NU	-1901-16955	Pacific/Niue
 NZ,AQ	-3652+17446	Pacific/Auckland	New Zealand time
 NZ	-4357-17633	Pacific/Chatham	Chatham Islands
-PA,CA,KY	+0858-07932	America/Panama	EST - Panama, Cayman, ON (Atikokan), NU (Coral H)
+PA,CA,KY	+0858-07932	America/Panama	EST - ON (Atikokan), NU (Coral H)
 PE	-1203-07703	America/Lima
 PF	-1732-14934	Pacific/Tahiti	Society Islands
 PF	-0900-13930	Pacific/Marquesas	Marquesas Islands
@@ -285,13 +287,13 @@ RU	+4310+13156	Asia/Vladivostok	MSK+07 - Amur River
 RU	+643337+1431336	Asia/Ust-Nera	MSK+07 - Oymyakonsky
 RU	+5934+15048	Asia/Magadan	MSK+08 - Magadan
 RU	+4658+14242	Asia/Sakhalin	MSK+08 - Sakhalin Island
-RU	+6728+15343	Asia/Srednekolymsk	MSK+08 - Sakha (E); North Kuril Is
+RU	+6728+15343	Asia/Srednekolymsk	MSK+08 - Sakha (E); N Kuril Is
 RU	+5301+15839	Asia/Kamchatka	MSK+09 - Kamchatka
 RU	+6445+17729	Asia/Anadyr	MSK+09 - Bering Sea
-SA,AQ,KW,YE	+2438+04643	Asia/Riyadh	Arabia, Syowa
-SB,FM	-0932+16012	Pacific/Guadalcanal	Solomons, Pohnpei
+SA,AQ,KW,YE	+2438+04643	Asia/Riyadh	Syowa
+SB,FM	-0932+16012	Pacific/Guadalcanal	Pohnpei
 SD	+1536+03232	Africa/Khartoum
-SG,MY	+0117+10351	Asia/Singapore	Singapore, peninsular Malaysia
+SG,MY	+0117+10351	Asia/Singapore	peninsular Malaysia
 SR	+0550-05510	America/Paramaribo
 SS	+0451+03137	Africa/Juba
 ST	+0020+00644	Africa/Sao_Tome
@@ -299,7 +301,7 @@ SV	+1342-08912	America/El_Salvador
 SY	+3330+03618	Asia/Damascus
 TC	+2128-07108	America/Grand_Turk
 TD	+1207+01503	Africa/Ndjamena
-TH,CX,KH,LA,VN	+1345+10031	Asia/Bangkok	Indochina (most areas)
+TH,CX,KH,LA,VN	+1345+10031	Asia/Bangkok	north Vietnam
 TJ	+3835+06848	Asia/Dushanbe
 TK	-0922-17114	Pacific/Fakaofo
 TL	-0833+12535	Asia/Dili
@@ -308,7 +310,7 @@ TN	+3648+01011	Africa/Tunis
 TO	-210800-1751200	Pacific/Tongatapu
 TR	+4101+02858	Europe/Istanbul
 TW	+2503+12130	Asia/Taipei
-UA	+5026+03031	Europe/Kyiv	Ukraine (most areas)
+UA	+5026+03031	Europe/Kyiv	most of Ukraine
 US	+404251-0740023	America/New_York	Eastern (most areas)
 US	+421953-0830245	America/Detroit	Eastern - MI (most areas)
 US	+381515-0854534	America/Kentucky/Louisville	Eastern - KY (Louisville area)
@@ -328,7 +330,7 @@ US	+465042-1012439	America/North_Dakota/New_Salem	Central - ND (Morton rural)
 US	+471551-1014640	America/North_Dakota/Beulah	Central - ND (Mercer)
 US	+394421-1045903	America/Denver	Mountain (most areas)
 US	+433649-1161209	America/Boise	Mountain - ID (south); OR (east)
-US,CA	+332654-1120424	America/Phoenix	MST - Arizona (except Navajo), Creston BC
+US,CA	+332654-1120424	America/Phoenix	MST - AZ (most areas), Creston BC
 US	+340308-1181434	America/Los_Angeles	Pacific
 US	+611305-1495401	America/Anchorage	Alaska (most areas)
 US	+581807-1342511	America/Juneau	Alaska - Juneau area
@@ -336,13 +338,13 @@ US	+571035-1351807	America/Sitka	Alaska - Sitka area
 US	+550737-1313435	America/Metlakatla	Alaska - Annette Island
 US	+593249-1394338	America/Yakutat	Alaska - Yakutat
 US	+643004-1652423	America/Nome	Alaska (west)
-US	+515248-1763929	America/Adak	Aleutian Islands
-US,UM	+211825-1575130	Pacific/Honolulu	Hawaii
+US	+515248-1763929	America/Adak	Alaska - western Aleutians
+US	+211825-1575130	Pacific/Honolulu	Hawaii
 UY	-345433-0561245	America/Montevideo
 UZ	+3940+06648	Asia/Samarkand	Uzbekistan (west)
 UZ	+4120+06918	Asia/Tashkent	Uzbekistan (east)
 VE	+1030-06656	America/Caracas
-VN	+1045+10640	Asia/Ho_Chi_Minh	Vietnam (south)
+VN	+1045+10640	Asia/Ho_Chi_Minh	south Vietnam
 VU	-1740+16825	Pacific/Efate
 WS	-1350-17144	Pacific/Apia
 ZA,LS,SZ	-2615+02800	Africa/Johannesburg
diff --git a/absl/time/time.cc b/absl/time/time.cc
index 7256a699..d983c12b 100644
--- a/absl/time/time.cc
+++ b/absl/time/time.cc
@@ -66,6 +66,7 @@ inline int64_t FloorToUnit(absl::Duration d, absl::Duration unit) {
              : q - 1;
 }
 
+ABSL_INTERNAL_DISABLE_DEPRECATED_DECLARATION_WARNING
 inline absl::Time::Breakdown InfiniteFutureBreakdown() {
   absl::Time::Breakdown bd;
   bd.year = std::numeric_limits<int64_t>::max();
@@ -99,6 +100,7 @@ inline absl::Time::Breakdown InfinitePastBreakdown() {
   bd.zone_abbr = "-00";
   return bd;
 }
+ABSL_INTERNAL_RESTORE_DEPRECATED_DECLARATION_WARNING
 
 inline absl::TimeZone::CivilInfo InfiniteFutureCivilInfo() {
   TimeZone::CivilInfo ci;
@@ -120,6 +122,7 @@ inline absl::TimeZone::CivilInfo InfinitePastCivilInfo() {
   return ci;
 }
 
+ABSL_INTERNAL_DISABLE_DEPRECATED_DECLARATION_WARNING
 inline absl::TimeConversion InfiniteFutureTimeConversion() {
   absl::TimeConversion tc;
   tc.pre = tc.trans = tc.post = absl::InfiniteFuture();
@@ -135,9 +138,10 @@ inline TimeConversion InfinitePastTimeConversion() {
   tc.normalized = true;
   return tc;
 }
+ABSL_INTERNAL_RESTORE_DEPRECATED_DECLARATION_WARNING
 
 // Makes a Time from sec, overflowing to InfiniteFuture/InfinitePast as
-// necessary. If sec is min/max, then consult cs+tz to check for overlow.
+// necessary. If sec is min/max, then consult cs+tz to check for overflow.
 Time MakeTimeWithOverflow(const cctz::time_point<cctz::seconds>& sec,
                           const cctz::civil_second& cs,
                           const cctz::time_zone& tz,
@@ -203,6 +207,7 @@ bool FindTransition(const cctz::time_zone& tz,
 // Time
 //
 
+ABSL_INTERNAL_DISABLE_DEPRECATED_DECLARATION_WARNING
 absl::Time::Breakdown Time::In(absl::TimeZone tz) const {
   if (*this == absl::InfiniteFuture()) return InfiniteFutureBreakdown();
   if (*this == absl::InfinitePast()) return InfinitePastBreakdown();
@@ -227,6 +232,7 @@ absl::Time::Breakdown Time::In(absl::TimeZone tz) const {
   bd.zone_abbr = al.abbr;
   return bd;
 }
+ABSL_INTERNAL_RESTORE_DEPRECATED_DECLARATION_WARNING
 
 //
 // Conversions from/to other time types.
@@ -398,7 +404,7 @@ bool TimeZone::PrevTransition(Time t, CivilTransition* trans) const {
 //
 // Conversions involving time zones.
 //
-
+ABSL_INTERNAL_DISABLE_DEPRECATED_DECLARATION_WARNING
 absl::TimeConversion ConvertDateTime(int64_t year, int mon, int day, int hour,
                                      int min, int sec, TimeZone tz) {
   // Avoids years that are too extreme for CivilSecond to normalize.
@@ -430,6 +436,7 @@ absl::TimeConversion ConvertDateTime(int64_t year, int mon, int day, int hour,
   }
   return tc;
 }
+ABSL_INTERNAL_RESTORE_DEPRECATED_DECLARATION_WARNING
 
 absl::Time FromTM(const struct tm& tm, absl::TimeZone tz) {
   civil_year_t tm_year = tm.tm_year;
diff --git a/absl/time/time.h b/absl/time/time.h
index cc390082..37580805 100644
--- a/absl/time/time.h
+++ b/absl/time/time.h
@@ -84,6 +84,7 @@ struct timeval;
 #include <type_traits>
 #include <utility>
 
+#include "absl/base/config.h"
 #include "absl/base/macros.h"
 #include "absl/strings/string_view.h"
 #include "absl/time/civil_time.h"
@@ -187,7 +188,12 @@ class Duration {
   Duration& operator%=(Duration rhs);
 
   // Overloads that forward to either the int64_t or double overloads above.
-  // Integer operands must be representable as int64_t.
+  // Integer operands must be representable as int64_t. Integer division is
+  // truncating, so values less than the resolution will be returned as zero.
+  // Floating-point multiplication and division is rounding (halfway cases
+  // rounding away from zero), so values less than the resolution may be
+  // returned as either the resolution or zero.  In particular, `d / 2.0`
+  // can produce `d` when it is the resolution and "even".
   template <typename T, time_internal::EnableIfIntegral<T> = 0>
   Duration& operator*=(T r) {
     int64_t x = r;
@@ -214,7 +220,7 @@ class Duration {
 
   template <typename H>
   friend H AbslHashValue(H h, Duration d) {
-    return H::combine(std::move(h), d.rep_hi_, d.rep_lo_);
+    return H::combine(std::move(h), d.rep_hi_.Get(), d.rep_lo_);
   }
 
  private:
@@ -223,7 +229,79 @@ class Duration {
   friend constexpr Duration time_internal::MakeDuration(int64_t hi,
                                                         uint32_t lo);
   constexpr Duration(int64_t hi, uint32_t lo) : rep_hi_(hi), rep_lo_(lo) {}
-  int64_t rep_hi_;
+
+  // We store `rep_hi_` 4-byte rather than 8-byte aligned to avoid 4 bytes of
+  // tail padding.
+  class HiRep {
+   public:
+    // Default constructor default-initializes `hi_`, which has the same
+    // semantics as default-initializing an `int64_t` (undetermined value).
+    HiRep() = default;
+
+    HiRep(const HiRep&) = default;
+    HiRep& operator=(const HiRep&) = default;
+
+    explicit constexpr HiRep(const int64_t value)
+        :  // C++17 forbids default-initialization in constexpr contexts. We can
+           // remove this in C++20.
+#if defined(ABSL_IS_BIG_ENDIAN) && ABSL_IS_BIG_ENDIAN
+          hi_(0),
+          lo_(0)
+#else
+          lo_(0),
+          hi_(0)
+#endif
+    {
+      *this = value;
+    }
+
+    constexpr int64_t Get() const {
+      const uint64_t unsigned_value =
+          (static_cast<uint64_t>(hi_) << 32) | static_cast<uint64_t>(lo_);
+      // `static_cast<int64_t>(unsigned_value)` is implementation-defined
+      // before c++20. On all supported platforms the behaviour is that mandated
+      // by c++20, i.e. "If the destination type is signed, [...] the result is
+      // the unique value of the destination type equal to the source value
+      // modulo 2^n, where n is the number of bits used to represent the
+      // destination type."
+      static_assert(
+          (static_cast<int64_t>((std::numeric_limits<uint64_t>::max)()) ==
+           int64_t{-1}) &&
+              (static_cast<int64_t>(static_cast<uint64_t>(
+                                        (std::numeric_limits<int64_t>::max)()) +
+                                    1) ==
+               (std::numeric_limits<int64_t>::min)()),
+          "static_cast<int64_t>(uint64_t) does not have c++20 semantics");
+      return static_cast<int64_t>(unsigned_value);
+    }
+
+    constexpr HiRep& operator=(const int64_t value) {
+      // "If the destination type is unsigned, the resulting value is the
+      // smallest unsigned value equal to the source value modulo 2^n
+      // where `n` is the number of bits used to represent the destination
+      // type".
+      const auto unsigned_value = static_cast<uint64_t>(value);
+      hi_ = static_cast<uint32_t>(unsigned_value >> 32);
+      lo_ = static_cast<uint32_t>(unsigned_value);
+      return *this;
+    }
+
+   private:
+    // Notes:
+    //  - Ideally we would use a `char[]` and `std::bitcast`, but the latter
+    //    does not exist (and is not constexpr in `absl`) before c++20.
+    //  - Order is optimized depending on endianness so that the compiler can
+    //    turn `Get()` (resp. `operator=()`) into a single 8-byte load (resp.
+    //    store).
+#if defined(ABSL_IS_BIG_ENDIAN) && ABSL_IS_BIG_ENDIAN
+    uint32_t hi_;
+    uint32_t lo_;
+#else
+    uint32_t lo_;
+    uint32_t hi_;
+#endif
+  };
+  HiRep rep_hi_;
   uint32_t rep_lo_;
 };
 
@@ -609,6 +687,12 @@ inline std::ostream& operator<<(std::ostream& os, Duration d) {
   return os << FormatDuration(d);
 }
 
+// Support for StrFormat(), StrCat() etc.
+template <typename Sink>
+void AbslStringify(Sink& sink, Duration d) {
+  sink.Append(FormatDuration(d));
+}
+
 // ParseDuration()
 //
 // Parses a duration string consisting of a possibly signed sequence of
@@ -718,8 +802,7 @@ class Time {
   // `absl::TimeZone`.
   //
   // Deprecated. Use `absl::TimeZone::CivilInfo`.
-  struct
-      Breakdown {
+  struct ABSL_DEPRECATED("Use `absl::TimeZone::CivilInfo`.") Breakdown {
     int64_t year;        // year (e.g., 2013)
     int month;           // month of year [1:12]
     int day;             // day of month [1:31]
@@ -745,7 +828,10 @@ class Time {
   // Returns the breakdown of this instant in the given TimeZone.
   //
   // Deprecated. Use `absl::TimeZone::At(Time)`.
+  ABSL_INTERNAL_DISABLE_DEPRECATED_DECLARATION_WARNING
+  ABSL_DEPRECATED("Use `absl::TimeZone::At(Time)`.")
   Breakdown In(TimeZone tz) const;
+  ABSL_INTERNAL_RESTORE_DEPRECATED_DECLARATION_WARNING
 
   template <typename H>
   friend H AbslHashValue(H h, Time t) {
@@ -839,7 +925,8 @@ ABSL_ATTRIBUTE_CONST_FUNCTION constexpr Time InfinitePast() {
 // FromUDate()
 // FromUniversal()
 //
-// Creates an `absl::Time` from a variety of other representations.
+// Creates an `absl::Time` from a variety of other representations.  See
+// https://unicode-org.github.io/icu/userguide/datetime/universaltimescale.html
 ABSL_ATTRIBUTE_CONST_FUNCTION constexpr Time FromUnixNanos(int64_t ns);
 ABSL_ATTRIBUTE_CONST_FUNCTION constexpr Time FromUnixMicros(int64_t us);
 ABSL_ATTRIBUTE_CONST_FUNCTION constexpr Time FromUnixMillis(int64_t ms);
@@ -856,10 +943,12 @@ ABSL_ATTRIBUTE_CONST_FUNCTION Time FromUniversal(int64_t universal);
 // ToUDate()
 // ToUniversal()
 //
-// Converts an `absl::Time` to a variety of other representations.  Note that
-// these operations round down toward negative infinity where necessary to
-// adjust to the resolution of the result type.  Beware of possible time_t
-// over/underflow in ToTime{T,val,spec}() on 32-bit platforms.
+// Converts an `absl::Time` to a variety of other representations.  See
+// https://unicode-org.github.io/icu/userguide/datetime/universaltimescale.html
+//
+// Note that these operations round down toward negative infinity where
+// necessary to adjust to the resolution of the result type.  Beware of
+// possible time_t over/underflow in ToTime{T,val,spec}() on 32-bit platforms.
 ABSL_ATTRIBUTE_CONST_FUNCTION int64_t ToUnixNanos(Time t);
 ABSL_ATTRIBUTE_CONST_FUNCTION int64_t ToUnixMicros(Time t);
 ABSL_ATTRIBUTE_CONST_FUNCTION int64_t ToUnixMillis(Time t);
@@ -1236,8 +1325,7 @@ ABSL_ATTRIBUTE_PURE_FUNCTION inline Time FromCivil(CivilSecond ct,
 // `absl::ConvertDateTime()`. Legacy version of `absl::TimeZone::TimeInfo`.
 //
 // Deprecated. Use `absl::TimeZone::TimeInfo`.
-struct
-    TimeConversion {
+struct ABSL_DEPRECATED("Use `absl::TimeZone::TimeInfo`.") TimeConversion {
   Time pre;    // time calculated using the pre-transition offset
   Time trans;  // when the civil-time discontinuity occurred
   Time post;   // time calculated using the post-transition offset
@@ -1271,8 +1359,11 @@ struct
 //   // absl::ToCivilDay(tc.pre, tz).day() == 1
 //
 // Deprecated. Use `absl::TimeZone::At(CivilSecond)`.
+ABSL_INTERNAL_DISABLE_DEPRECATED_DECLARATION_WARNING
+ABSL_DEPRECATED("Use `absl::TimeZone::At(CivilSecond)`.")
 TimeConversion ConvertDateTime(int64_t year, int mon, int day, int hour,
                                int min, int sec, TimeZone tz);
+ABSL_INTERNAL_RESTORE_DEPRECATED_DECLARATION_WARNING
 
 // FromDateTime()
 //
@@ -1289,9 +1380,12 @@ TimeConversion ConvertDateTime(int64_t year, int mon, int day, int hour,
 // Deprecated. Use `absl::FromCivil(CivilSecond, TimeZone)`. Note that the
 // behavior of `FromCivil()` differs from `FromDateTime()` for skipped civil
 // times. If you care about that see `absl::TimeZone::At(absl::CivilSecond)`.
-inline Time FromDateTime(int64_t year, int mon, int day, int hour,
-                         int min, int sec, TimeZone tz) {
+ABSL_DEPRECATED("Use `absl::FromCivil(CivilSecond, TimeZone)`.")
+inline Time FromDateTime(int64_t year, int mon, int day, int hour, int min,
+                         int sec, TimeZone tz) {
+  ABSL_INTERNAL_DISABLE_DEPRECATED_DECLARATION_WARNING
   return ConvertDateTime(year, mon, day, hour, min, sec, tz).pre;
+  ABSL_INTERNAL_RESTORE_DEPRECATED_DECLARATION_WARNING
 }
 
 // FromTM()
@@ -1386,6 +1480,12 @@ inline std::ostream& operator<<(std::ostream& os, Time t) {
   return os << FormatTime(t);
 }
 
+// Support for StrFormat(), StrCat() etc.
+template <typename Sink>
+void AbslStringify(Sink& sink, Time t) {
+  sink.Append(FormatTime(t));
+}
+
 // ParseTime()
 //
 // Parses an input string according to the provided format string and
@@ -1491,7 +1591,7 @@ ABSL_ATTRIBUTE_CONST_FUNCTION constexpr Duration MakeNormalizedDuration(
 
 // Provide access to the Duration representation.
 ABSL_ATTRIBUTE_CONST_FUNCTION constexpr int64_t GetRepHi(Duration d) {
-  return d.rep_hi_;
+  return d.rep_hi_.Get();
 }
 ABSL_ATTRIBUTE_CONST_FUNCTION constexpr uint32_t GetRepLo(Duration d) {
   return d.rep_lo_;
diff --git a/absl/time/time_test.cc b/absl/time/time_test.cc
index d235e9ad..bcf4f2ad 100644
--- a/absl/time/time_test.cc
+++ b/absl/time/time_test.cc
@@ -28,6 +28,7 @@
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
 #include "absl/numeric/int128.h"
+#include "absl/strings/str_format.h"
 #include "absl/time/clock.h"
 #include "absl/time/internal/test_util.h"
 
@@ -377,11 +378,6 @@ TEST(Time, FloorConversion) {
 }
 
 TEST(Time, RoundtripConversion) {
-#if defined(ABSL_SKIP_TIME_TESTS_BROKEN_ON_MSVC_OPT) && \
-    ABSL_SKIP_TIME_TESTS_BROKEN_ON_MSVC_OPT
-  GTEST_SKIP();
-#endif
-
 #define TEST_CONVERSION_ROUND_TRIP(SOURCE, FROM, TO, MATCHER) \
   EXPECT_THAT(TO(FROM(SOURCE)), MATCHER(SOURCE))
 
@@ -563,11 +559,6 @@ TEST(Time, FromChrono) {
 }
 
 TEST(Time, ToChronoTime) {
-#if defined(ABSL_SKIP_TIME_TESTS_BROKEN_ON_MSVC_OPT) && \
-    ABSL_SKIP_TIME_TESTS_BROKEN_ON_MSVC_OPT
-  GTEST_SKIP();
-#endif
-
   EXPECT_EQ(std::chrono::system_clock::from_time_t(-1),
             absl::ToChronoTime(absl::FromTimeT(-1)));
   EXPECT_EQ(std::chrono::system_clock::from_time_t(0),
@@ -1287,4 +1278,11 @@ TEST(Time, PrevTransitionNYC) {
   // We have a transition but we don't know which one.
 }
 
+TEST(Time, AbslStringify) {
+  // FormatTime is already well tested, so just use one test case here to
+  // verify that StrFormat("%v", t) works as expected.
+  absl::Time t = absl::Now();
+  EXPECT_EQ(absl::StrFormat("%v", t), absl::FormatTime(t));
+}
+
 }  // namespace
diff --git a/absl/types/BUILD.bazel b/absl/types/BUILD.bazel
index bb801012..b57d3b9b 100644
--- a/absl/types/BUILD.bazel
+++ b/absl/types/BUILD.bazel
@@ -77,8 +77,8 @@ cc_test(
         ":any",
         "//absl/base:config",
         "//absl/base:exception_testing",
-        "//absl/base:raw_logging_internal",
         "//absl/container:test_instance_tracker",
+        "//absl/log",
         "@com_google_googletest//:gtest_main",
     ],
 )
@@ -185,7 +185,7 @@ cc_test(
     deps = [
         ":optional",
         "//absl/base:config",
-        "//absl/base:raw_logging_internal",
+        "//absl/log",
         "//absl/meta:type_traits",
         "//absl/strings",
         "@com_google_googletest//:gtest_main",
diff --git a/absl/types/CMakeLists.txt b/absl/types/CMakeLists.txt
index 830953ae..c0dcee79 100644
--- a/absl/types/CMakeLists.txt
+++ b/absl/types/CMakeLists.txt
@@ -68,7 +68,7 @@ absl_cc_test(
     absl::any
     absl::config
     absl::exception_testing
-    absl::raw_logging_internal
+    absl::log
     absl::test_instance_tracker
     GTest::gmock_main
 )
@@ -220,7 +220,7 @@ absl_cc_test(
   DEPS
     absl::optional
     absl::config
-    absl::raw_logging_internal
+    absl::log
     absl::strings
     absl::type_traits
     GTest::gmock_main
diff --git a/absl/types/any.h b/absl/types/any.h
index 204da26d..61f071f1 100644
--- a/absl/types/any.h
+++ b/absl/types/any.h
@@ -53,6 +53,7 @@
 #ifndef ABSL_TYPES_ANY_H_
 #define ABSL_TYPES_ANY_H_
 
+#include "absl/base/attributes.h"
 #include "absl/base/config.h"
 #include "absl/utility/utility.h"
 
@@ -288,7 +289,7 @@ class any {
       typename T, typename... Args, typename VT = absl::decay_t<T>,
       absl::enable_if_t<std::is_copy_constructible<VT>::value &&
                         std::is_constructible<VT, Args...>::value>* = nullptr>
-  VT& emplace(Args&&... args) {
+  VT& emplace(Args&&... args) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     reset();  // NOTE: reset() is required here even in the world of exceptions.
     Obj<VT>* const object_ptr =
         new Obj<VT>(in_place, std::forward<Args>(args)...);
@@ -312,7 +313,8 @@ class any {
       absl::enable_if_t<std::is_copy_constructible<VT>::value &&
                         std::is_constructible<VT, std::initializer_list<U>&,
                                               Args...>::value>* = nullptr>
-  VT& emplace(std::initializer_list<U> ilist, Args&&... args) {
+  VT& emplace(std::initializer_list<U> ilist,
+              Args&&... args) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     reset();  // NOTE: reset() is required here even in the world of exceptions.
     Obj<VT>* const object_ptr =
         new Obj<VT>(in_place, ilist, std::forward<Args>(args)...);
diff --git a/absl/types/any_test.cc b/absl/types/any_test.cc
index d382b927..666ea5b6 100644
--- a/absl/types/any_test.cc
+++ b/absl/types/any_test.cc
@@ -25,8 +25,8 @@
 #include "gtest/gtest.h"
 #include "absl/base/config.h"
 #include "absl/base/internal/exception_testing.h"
-#include "absl/base/internal/raw_logging.h"
 #include "absl/container/internal/test_instance_tracker.h"
+#include "absl/log/log.h"
 
 namespace {
 using absl::test_internal::CopyableOnlyInstance;
@@ -704,7 +704,7 @@ struct BadCopyable {
 #ifdef ABSL_HAVE_EXCEPTIONS
     throw BadCopy();
 #else
-    ABSL_RAW_LOG(FATAL, "Bad copy");
+    LOG(FATAL) << "Bad copy";
 #endif
   }
 };
diff --git a/absl/types/compare.h b/absl/types/compare.h
index 1a965e97..2b89b69c 100644
--- a/absl/types/compare.h
+++ b/absl/types/compare.h
@@ -36,6 +36,7 @@
 #include <type_traits>
 
 #include "absl/base/attributes.h"
+#include "absl/base/macros.h"
 #include "absl/meta/type_traits.h"
 
 namespace absl {
@@ -45,14 +46,23 @@ namespace compare_internal {
 using value_type = int8_t;
 
 class OnlyLiteralZero {
-  // A private type which cannot be named to explicitly cast to it.
-  struct MatchLiteralZero;
-
  public:
+#if ABSL_HAVE_ATTRIBUTE(enable_if)
+  // On clang, we can avoid triggering modernize-use-nullptr by only enabling
+  // this overload when the value is a compile time integer constant equal to 0.
+  //
+  // In c++20, this could be a static_assert in a consteval function.
+  constexpr OnlyLiteralZero(int n)  // NOLINT
+      __attribute__((enable_if(n == 0, "Only literal `0` is allowed."))) {}
+#else  // ABSL_HAVE_ATTRIBUTE(enable_if)
   // Accept only literal zero since it can be implicitly converted to a pointer
-  // type. nullptr constants will be caught by the other constructor which
-  // accepts a nullptr_t.
-  constexpr OnlyLiteralZero(MatchLiteralZero *) noexcept {}  // NOLINT
+  // to member type. nullptr constants will be caught by the other constructor
+  // which accepts a nullptr_t.
+  //
+  // This constructor is not used for clang since it triggers
+  // modernize-use-nullptr.
+  constexpr OnlyLiteralZero(int OnlyLiteralZero::*) noexcept {}  // NOLINT
+#endif
 
   // Fails compilation when `nullptr` or integral type arguments other than
   // `int` are passed. This constructor doesn't accept `int` because literal `0`
diff --git a/absl/types/internal/optional.h b/absl/types/internal/optional.h
index 6ed0c669..a96d260a 100644
--- a/absl/types/internal/optional.h
+++ b/absl/types/internal/optional.h
@@ -25,34 +25,6 @@
 #include "absl/meta/type_traits.h"
 #include "absl/utility/utility.h"
 
-// ABSL_OPTIONAL_USE_INHERITING_CONSTRUCTORS
-//
-// Inheriting constructors is supported in GCC 4.8+, Clang 3.3+ and MSVC 2015.
-// __cpp_inheriting_constructors is a predefined macro and a recommended way to
-// check for this language feature, but GCC doesn't support it until 5.0 and
-// Clang doesn't support it until 3.6.
-// Also, MSVC 2015 has a bug: it doesn't inherit the constexpr template
-// constructor. For example, the following code won't work on MSVC 2015 Update3:
-// struct Base {
-//   int t;
-//   template <typename T>
-//   constexpr Base(T t_) : t(t_) {}
-// };
-// struct Foo : Base {
-//   using Base::Base;
-// }
-// constexpr Foo foo(0);  // doesn't work on MSVC 2015
-#if defined(__clang__)
-#if __has_feature(cxx_inheriting_constructors)
-#define ABSL_OPTIONAL_USE_INHERITING_CONSTRUCTORS 1
-#endif
-#elif (defined(__GNUC__) &&                                       \
-       (__GNUC__ > 4 || __GNUC__ == 4 && __GNUC_MINOR__ >= 8)) || \
-    (__cpp_inheriting_constructors >= 200802) ||                  \
-    (defined(_MSC_VER) && _MSC_VER >= 1910)
-#define ABSL_OPTIONAL_USE_INHERITING_CONSTRUCTORS 1
-#endif
-
 namespace absl {
 ABSL_NAMESPACE_BEGIN
 
@@ -145,15 +117,7 @@ template <typename T>
 class optional_data_base : public optional_data_dtor_base<T> {
  protected:
   using base = optional_data_dtor_base<T>;
-#ifdef ABSL_OPTIONAL_USE_INHERITING_CONSTRUCTORS
   using base::base;
-#else
-  optional_data_base() = default;
-
-  template <typename... Args>
-  constexpr explicit optional_data_base(in_place_t t, Args&&... args)
-      : base(t, absl::forward<Args>(args)...) {}
-#endif
 
   template <typename... Args>
   void construct(Args&&... args) {
@@ -188,27 +152,13 @@ class optional_data;
 template <typename T>
 class optional_data<T, true> : public optional_data_base<T> {
  protected:
-#ifdef ABSL_OPTIONAL_USE_INHERITING_CONSTRUCTORS
   using optional_data_base<T>::optional_data_base;
-#else
-  optional_data() = default;
-
-  template <typename... Args>
-  constexpr explicit optional_data(in_place_t t, Args&&... args)
-      : optional_data_base<T>(t, absl::forward<Args>(args)...) {}
-#endif
 };
 
 template <typename T>
 class optional_data<T, false> : public optional_data_base<T> {
  protected:
-#ifdef ABSL_OPTIONAL_USE_INHERITING_CONSTRUCTORS
   using optional_data_base<T>::optional_data_base;
-#else
-  template <typename... Args>
-  constexpr explicit optional_data(in_place_t t, Args&&... args)
-      : optional_data_base<T>(t, absl::forward<Args>(args)...) {}
-#endif
 
   optional_data() = default;
 
@@ -399,6 +349,4 @@ struct optional_hash_base<T, decltype(std::hash<absl::remove_const_t<T> >()(
 ABSL_NAMESPACE_END
 }  // namespace absl
 
-#undef ABSL_OPTIONAL_USE_INHERITING_CONSTRUCTORS
-
 #endif  // ABSL_TYPES_INTERNAL_OPTIONAL_H_
diff --git a/absl/types/internal/span.h b/absl/types/internal/span.h
index 344ad4db..ab89ba3c 100644
--- a/absl/types/internal/span.h
+++ b/absl/types/internal/span.h
@@ -88,7 +88,7 @@ using EnableIfMutable =
 template <template <typename> class SpanT, typename T>
 bool EqualImpl(SpanT<T> a, SpanT<T> b) {
   static_assert(std::is_const<T>::value, "");
-  return absl::equal(a.begin(), a.end(), b.begin(), b.end());
+  return std::equal(a.begin(), a.end(), b.begin(), b.end());
 }
 
 template <template <typename> class SpanT, typename T>
@@ -125,7 +125,7 @@ struct IsView<
 };
 
 // These enablers result in 'int' so they can be used as typenames or defaults
-// in template paramters lists.
+// in template parameters lists.
 template <typename T>
 using EnableIfIsView = std::enable_if_t<IsView<T>::value, int>;
 
diff --git a/absl/types/internal/variant.h b/absl/types/internal/variant.h
index c82ded44..fc8829e5 100644
--- a/absl/types/internal/variant.h
+++ b/absl/types/internal/variant.h
@@ -877,8 +877,8 @@ struct IndexOfConstructedType<
 template <std::size_t... Is>
 struct ContainsVariantNPos
     : absl::negation<std::is_same<  // NOLINT
-          absl::integer_sequence<bool, 0 <= Is...>,
-          absl::integer_sequence<bool, Is != absl::variant_npos...>>> {};
+          std::integer_sequence<bool, 0 <= Is...>,
+          std::integer_sequence<bool, Is != absl::variant_npos...>>> {};
 
 template <class Op, class... QualifiedVariants>
 using RawVisitResult =
diff --git a/absl/types/optional.h b/absl/types/optional.h
index 134b2aff..0a8080dc 100644
--- a/absl/types/optional.h
+++ b/absl/types/optional.h
@@ -130,7 +130,7 @@ class optional : private optional_internal::optional_data<T>,
 
   // Constructs an `optional` holding an empty value, NOT a default constructed
   // `T`.
-  constexpr optional() noexcept {}
+  constexpr optional() noexcept = default;
 
   // Constructs an `optional` initialized with `nullopt` to hold an empty value.
   constexpr optional(nullopt_t) noexcept {}  // NOLINT(runtime/explicit)
@@ -357,7 +357,7 @@ class optional : private optional_internal::optional_data<T>,
   template <typename... Args,
             typename = typename std::enable_if<
                 std::is_constructible<T, Args&&...>::value>::type>
-  T& emplace(Args&&... args) {
+  T& emplace(Args&&... args) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     this->destruct();
     this->construct(std::forward<Args>(args)...);
     return reference();
@@ -377,7 +377,8 @@ class optional : private optional_internal::optional_data<T>,
   template <typename U, typename... Args,
             typename = typename std::enable_if<std::is_constructible<
                 T, std::initializer_list<U>&, Args&&...>::value>::type>
-  T& emplace(std::initializer_list<U> il, Args&&... args) {
+  T& emplace(std::initializer_list<U> il,
+             Args&&... args) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     this->destruct();
     this->construct(il, std::forward<Args>(args)...);
     return reference();
@@ -414,11 +415,11 @@ class optional : private optional_internal::optional_data<T>,
   // `optional` is empty, behavior is undefined.
   //
   // If you need myOpt->foo in constexpr, use (*myOpt).foo instead.
-  const T* operator->() const {
+  const T* operator->() const ABSL_ATTRIBUTE_LIFETIME_BOUND {
     ABSL_HARDENING_ASSERT(this->engaged_);
     return std::addressof(this->data_);
   }
-  T* operator->() {
+  T* operator->() ABSL_ATTRIBUTE_LIFETIME_BOUND {
     ABSL_HARDENING_ASSERT(this->engaged_);
     return std::addressof(this->data_);
   }
@@ -427,17 +428,17 @@ class optional : private optional_internal::optional_data<T>,
   //
   // Accesses the underlying `T` value of an `optional`. If the `optional` is
   // empty, behavior is undefined.
-  constexpr const T& operator*() const& {
+  constexpr const T& operator*() const& ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return ABSL_HARDENING_ASSERT(this->engaged_), reference();
   }
-  T& operator*() & {
+  T& operator*() & ABSL_ATTRIBUTE_LIFETIME_BOUND {
     ABSL_HARDENING_ASSERT(this->engaged_);
     return reference();
   }
-  constexpr const T&& operator*() const && {
+  constexpr const T&& operator*() const&& ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return ABSL_HARDENING_ASSERT(this->engaged_), absl::move(reference());
   }
-  T&& operator*() && {
+  T&& operator*() && ABSL_ATTRIBUTE_LIFETIME_BOUND {
     ABSL_HARDENING_ASSERT(this->engaged_);
     return std::move(reference());
   }
@@ -472,23 +473,24 @@ class optional : private optional_internal::optional_data<T>,
   // and lvalue/rvalue-ness of the `optional` is preserved to the view of
   // the `T` sub-object. Throws `absl::bad_optional_access` when the `optional`
   // is empty.
-  constexpr const T& value() const & {
+  constexpr const T& value() const& ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return static_cast<bool>(*this)
                ? reference()
                : (optional_internal::throw_bad_optional_access(), reference());
   }
-  T& value() & {
+  T& value() & ABSL_ATTRIBUTE_LIFETIME_BOUND {
     return static_cast<bool>(*this)
                ? reference()
                : (optional_internal::throw_bad_optional_access(), reference());
   }
-  T&& value() && {  // NOLINT(build/c++11)
+  T&& value() && ABSL_ATTRIBUTE_LIFETIME_BOUND {  // NOLINT(build/c++11)
     return std::move(
         static_cast<bool>(*this)
             ? reference()
             : (optional_internal::throw_bad_optional_access(), reference()));
   }
-  constexpr const T&& value() const && {  // NOLINT(build/c++11)
+  constexpr const T&& value()
+      const&& ABSL_ATTRIBUTE_LIFETIME_BOUND {  // NOLINT(build/c++11)
     return absl::move(
         static_cast<bool>(*this)
             ? reference()
diff --git a/absl/types/optional_test.cc b/absl/types/optional_test.cc
index 21653a90..5da297b0 100644
--- a/absl/types/optional_test.cc
+++ b/absl/types/optional_test.cc
@@ -23,7 +23,7 @@
 
 #include "gtest/gtest.h"
 #include "absl/base/config.h"
-#include "absl/base/internal/raw_logging.h"
+#include "absl/log/log.h"
 #include "absl/meta/type_traits.h"
 #include "absl/strings/string_view.h"
 
@@ -97,9 +97,9 @@ struct StructorListener {
 // 4522: multiple assignment operators specified
 // We wrote multiple of them to test that the correct overloads are selected.
 #ifdef _MSC_VER
-#pragma warning( push )
-#pragma warning( disable : 4521)
-#pragma warning( disable : 4522)
+#pragma warning(push)
+#pragma warning(disable : 4521)
+#pragma warning(disable : 4522)
 #endif
 struct Listenable {
   static StructorListener* listener;
@@ -133,20 +133,11 @@ struct Listenable {
   ~Listenable() { ++listener->destruct; }
 };
 #ifdef _MSC_VER
-#pragma warning( pop )
+#pragma warning(pop)
 #endif
 
 StructorListener* Listenable::listener = nullptr;
 
-// ABSL_HAVE_NO_CONSTEXPR_INITIALIZER_LIST is defined to 1 when the standard
-// library implementation doesn't marked initializer_list's default constructor
-// constexpr. The C++11 standard doesn't specify constexpr on it, but C++14
-// added it. However, libstdc++ 4.7 marked it constexpr.
-#if defined(_LIBCPP_VERSION) && \
-    (_LIBCPP_STD_VER <= 11 || defined(_LIBCPP_HAS_NO_CXX14_CONSTEXPR))
-#define ABSL_HAVE_NO_CONSTEXPR_INITIALIZER_LIST 1
-#endif
-
 struct ConstexprType {
   enum CtorTypes {
     kCtorDefault,
@@ -156,10 +147,8 @@ struct ConstexprType {
   };
   constexpr ConstexprType() : x(kCtorDefault) {}
   constexpr explicit ConstexprType(int i) : x(kCtorInt) {}
-#ifndef ABSL_HAVE_NO_CONSTEXPR_INITIALIZER_LIST
   constexpr ConstexprType(std::initializer_list<int> il)
       : x(kCtorInitializerList) {}
-#endif
   constexpr ConstexprType(const char*)  // NOLINT(runtime/explicit)
       : x(kCtorConstChar) {}
   int x;
@@ -352,11 +341,9 @@ TEST(optionalTest, InPlaceConstructor) {
   constexpr absl::optional<ConstexprType> opt1{absl::in_place_t(), 1};
   static_assert(opt1, "");
   static_assert((*opt1).x == ConstexprType::kCtorInt, "");
-#ifndef ABSL_HAVE_NO_CONSTEXPR_INITIALIZER_LIST
   constexpr absl::optional<ConstexprType> opt2{absl::in_place_t(), {1, 2}};
   static_assert(opt2, "");
   static_assert((*opt2).x == ConstexprType::kCtorInitializerList, "");
-#endif
 
   EXPECT_FALSE((std::is_constructible<absl::optional<ConvertsFromInPlaceT>,
                                       absl::in_place_t>::value));
@@ -1000,9 +987,8 @@ TEST(optionalTest, PointerStuff) {
 // Skip that test to make the build green again when using the old compiler.
 // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59296 is fixed in 4.9.1.
 #if defined(__GNUC__) && !defined(__clang__)
-#define GCC_VERSION (__GNUC__ * 10000 \
-                     + __GNUC_MINOR__ * 100 \
-                     + __GNUC_PATCHLEVEL__)
+#define GCC_VERSION \
+  (__GNUC__ * 10000 + __GNUC_MINOR__ * 100 + __GNUC_PATCHLEVEL__)
 #if GCC_VERSION < 40901
 #define ABSL_SKIP_OVERLOAD_TEST_DUE_TO_GCC_BUG
 #endif
@@ -1010,7 +996,7 @@ TEST(optionalTest, PointerStuff) {
 
 // MSVC has a bug with "cv-qualifiers in class construction", fixed in 2017. See
 // https://docs.microsoft.com/en-us/cpp/cpp-conformance-improvements-2017#bug-fixes
-// The compiler some incorrectly ingores the cv-qualifier when generating a
+// The compiler some incorrectly ignores the cv-qualifier when generating a
 // class object via a constructor call. For example:
 //
 // class optional {
@@ -1214,7 +1200,6 @@ void optionalTest_Comparisons_EXPECT_GREATER(T x, U y) {
   EXPECT_TRUE(x >= y);
 }
 
-
 template <typename T, typename U, typename V>
 void TestComparisons() {
   absl::optional<T> ae, a2{2}, a4{4};
@@ -1307,7 +1292,6 @@ TEST(optionalTest, Comparisons) {
   EXPECT_TRUE(e1 == e2);
 }
 
-
 TEST(optionalTest, SwapRegression) {
   StructorListener listener;
   Listenable::listener = &listener;
@@ -1558,8 +1542,7 @@ TEST(optionalTest, Hash) {
 struct MoveMeNoThrow {
   MoveMeNoThrow() : x(0) {}
   [[noreturn]] MoveMeNoThrow(const MoveMeNoThrow& other) : x(other.x) {
-    ABSL_RAW_LOG(FATAL, "Should not be called.");
-    abort();
+    LOG(FATAL) << "Should not be called.";
   }
   MoveMeNoThrow(MoveMeNoThrow&& other) noexcept : x(other.x) {}
   int x;
diff --git a/absl/types/span.h b/absl/types/span.h
index d7bdbb1f..70ed8eb6 100644
--- a/absl/types/span.h
+++ b/absl/types/span.h
@@ -296,8 +296,7 @@ class Span {
   //
   // Returns a reference to the i'th element of this span.
   constexpr reference operator[](size_type i) const noexcept {
-    // MSVC 2015 accepts this as constexpr, but not ptr_[i]
-    return ABSL_HARDENING_ASSERT(i < size()), *(data() + i);
+    return ABSL_HARDENING_ASSERT(i < size()), ptr_[i];
   }
 
   // Span::at()
diff --git a/absl/types/span_test.cc b/absl/types/span_test.cc
index 13264aae..29e8681f 100644
--- a/absl/types/span_test.cc
+++ b/absl/types/span_test.cc
@@ -191,7 +191,7 @@ TEST(IntSpan, SpanOfDerived) {
 }
 
 void TestInitializerList(absl::Span<const int> s, const std::vector<int>& v) {
-  EXPECT_TRUE(absl::equal(s.begin(), s.end(), v.begin(), v.end()));
+  EXPECT_TRUE(std::equal(s.begin(), s.end(), v.begin(), v.end()));
 }
 
 TEST(ConstIntSpan, InitializerListConversion) {
diff --git a/absl/utility/BUILD.bazel b/absl/utility/BUILD.bazel
index ca4bc0a6..061f4c5b 100644
--- a/absl/utility/BUILD.bazel
+++ b/absl/utility/BUILD.bazel
@@ -52,3 +52,26 @@ cc_test(
         "@com_google_googletest//:gtest_main",
     ],
 )
+
+cc_library(
+    name = "if_constexpr",
+    hdrs = [
+        "internal/if_constexpr.h",
+    ],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        "//absl/base:config",
+    ],
+)
+
+cc_test(
+    name = "if_constexpr_test",
+    srcs = ["internal/if_constexpr_test.cc"],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":if_constexpr",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
diff --git a/absl/utility/CMakeLists.txt b/absl/utility/CMakeLists.txt
index 865b758f..27ee0de5 100644
--- a/absl/utility/CMakeLists.txt
+++ b/absl/utility/CMakeLists.txt
@@ -42,3 +42,27 @@ absl_cc_test(
     absl::strings
     GTest::gmock_main
 )
+
+absl_cc_library(
+  NAME
+    if_constexpr
+  HDRS
+    "internal/if_constexpr.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  DEPS
+    absl::config
+  PUBLIC
+)
+
+absl_cc_test(
+  NAME
+    if_constexpr_test
+  SRCS
+    "internal/if_constexpr_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  DEPS
+    absl::if_constexpr
+    GTest::gmock_main
+)
diff --git a/absl/utility/internal/if_constexpr.h b/absl/utility/internal/if_constexpr.h
new file mode 100644
index 00000000..7a26311d
--- /dev/null
+++ b/absl/utility/internal/if_constexpr.h
@@ -0,0 +1,70 @@
+// Copyright 2023 The Abseil Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// The IfConstexpr and IfConstexprElse utilities in this file are meant to be
+// used to emulate `if constexpr` in pre-C++17 mode in library implementation.
+// The motivation is to allow for avoiding complex SFINAE.
+//
+// The functions passed in must depend on the type(s) of the object(s) that
+// require SFINAE. For example:
+// template<typename T>
+// int MaybeFoo(T& t) {
+//   if constexpr (HasFoo<T>::value) return t.foo();
+//   return 0;
+// }
+//
+// can be written in pre-C++17 as:
+//
+// template<typename T>
+// int MaybeFoo(T& t) {
+//   int i = 0;
+//   absl::utility_internal::IfConstexpr<HasFoo<T>::value>(
+//       [&](const auto& fooer) { i = fooer.foo(); }, t);
+//   return i;
+// }
+
+#ifndef ABSL_UTILITY_INTERNAL_IF_CONSTEXPR_H_
+#define ABSL_UTILITY_INTERNAL_IF_CONSTEXPR_H_
+
+#include <tuple>
+#include <utility>
+
+#include "absl/base/config.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+namespace utility_internal {
+
+template <bool condition, typename TrueFunc, typename FalseFunc,
+          typename... Args>
+auto IfConstexprElse(TrueFunc&& true_func, FalseFunc&& false_func,
+                     Args&&... args) {
+  return std::get<condition>(std::forward_as_tuple(
+      std::forward<FalseFunc>(false_func), std::forward<TrueFunc>(true_func)))(
+      std::forward<Args>(args)...);
+}
+
+template <bool condition, typename Func, typename... Args>
+void IfConstexpr(Func&& func, Args&&... args) {
+  IfConstexprElse<condition>(std::forward<Func>(func), [](auto&&...){},
+                             std::forward<Args>(args)...);
+}
+
+}  // namespace utility_internal
+
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_UTILITY_INTERNAL_IF_CONSTEXPR_H_
diff --git a/absl/utility/internal/if_constexpr_test.cc b/absl/utility/internal/if_constexpr_test.cc
new file mode 100644
index 00000000..d1ee7236
--- /dev/null
+++ b/absl/utility/internal/if_constexpr_test.cc
@@ -0,0 +1,79 @@
+// Copyright 2023 The Abseil Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/utility/internal/if_constexpr.h"
+
+#include <utility>
+
+#include "gtest/gtest.h"
+
+namespace {
+
+struct Empty {};
+struct HasFoo {
+  int foo() const { return 1; }
+};
+
+TEST(IfConstexpr, Basic) {
+  int i = 0;
+  absl::utility_internal::IfConstexpr<false>(
+      [&](const auto& t) { i = t.foo(); }, Empty{});
+  EXPECT_EQ(i, 0);
+
+  absl::utility_internal::IfConstexpr<false>(
+      [&](const auto& t) { i = t.foo(); }, HasFoo{});
+  EXPECT_EQ(i, 0);
+
+  absl::utility_internal::IfConstexpr<true>(
+      [&](const auto& t) { i = t.foo(); }, HasFoo{});
+  EXPECT_EQ(i, 1);
+}
+
+TEST(IfConstexprElse, Basic) {
+  EXPECT_EQ(absl::utility_internal::IfConstexprElse<false>(
+      [&](const auto& t) { return t.foo(); }, [&](const auto&) { return 2; },
+      Empty{}), 2);
+
+  EXPECT_EQ(absl::utility_internal::IfConstexprElse<false>(
+      [&](const auto& t) { return t.foo(); }, [&](const auto&) { return 2; },
+      HasFoo{}), 2);
+
+  EXPECT_EQ(absl::utility_internal::IfConstexprElse<true>(
+      [&](const auto& t) { return t.foo(); }, [&](const auto&) { return 2; },
+      HasFoo{}), 1);
+}
+
+struct HasFooRValue {
+  int foo() && { return 1; }
+};
+struct RValueFunc {
+  void operator()(HasFooRValue&& t) && { *i = std::move(t).foo(); }
+
+  int* i = nullptr;
+};
+
+TEST(IfConstexpr, RValues) {
+  int i = 0;
+  RValueFunc func = {&i};
+  absl::utility_internal::IfConstexpr<false>(
+      std::move(func), HasFooRValue{});
+  EXPECT_EQ(i, 0);
+
+  func = RValueFunc{&i};
+  absl::utility_internal::IfConstexpr<true>(
+      std::move(func), HasFooRValue{});
+  EXPECT_EQ(i, 1);
+}
+
+}  // namespace
diff --git a/ci/cmake_common.sh b/ci/cmake_common.sh
index 373aaa9c..051b70dc 100644
--- a/ci/cmake_common.sh
+++ b/ci/cmake_common.sh
@@ -14,7 +14,7 @@
 
 # The commit of GoogleTest to be used in the CMake tests in this directory.
 # Keep this in sync with the commit in the WORKSPACE file.
-readonly ABSL_GOOGLETEST_COMMIT="b796f7d44681514f58a683a3a71ff17c94edb0c1" # v1.13.0
+readonly ABSL_GOOGLETEST_COMMIT="f8d7d77c06936315286eb55f8de22cd23c188571"  # v1.14.0
 
 # Avoid depending on GitHub by looking for a cached copy of the commit first.
 if [[ -r "${KOKORO_GFILE_DIR:-}/distdir/${ABSL_GOOGLETEST_COMMIT}.zip" ]]; then
diff --git a/ci/linux_docker_containers.sh b/ci/linux_docker_containers.sh
index dcaf18b9..a07c64ce 100644
--- a/ci/linux_docker_containers.sh
+++ b/ci/linux_docker_containers.sh
@@ -15,7 +15,7 @@
 # The file contains Docker container identifiers currently used by test scripts.
 # Test scripts should source this file to get the identifiers.
 
-readonly LINUX_ALPINE_CONTAINER="gcr.io/google.com/absl-177019/alpine:20201026"
+readonly LINUX_ALPINE_CONTAINER="gcr.io/google.com/absl-177019/alpine:20230612"
 readonly LINUX_CLANG_LATEST_CONTAINER="gcr.io/google.com/absl-177019/linux_hybrid-latest:20230217"
-readonly LINUX_GCC_LATEST_CONTAINER="gcr.io/google.com/absl-177019/linux_hybrid-latest:20230217"
+readonly LINUX_GCC_LATEST_CONTAINER="gcr.io/google.com/absl-177019/linux_hybrid-latest:20230517"
 readonly LINUX_GCC_FLOOR_CONTAINER="gcr.io/google.com/absl-177019/linux_gcc-floor:20230120"
diff --git a/ci/windows_clangcl_bazel.bat b/ci/windows_clangcl_bazel.bat
new file mode 100755
index 00000000..21230e1f
--- /dev/null
+++ b/ci/windows_clangcl_bazel.bat
@@ -0,0 +1,59 @@
+:: Copyright 2023 The Abseil Authors
+::
+:: Licensed under the Apache License, Version 2.0 (the "License");
+:: you may not use this file except in compliance with the License.
+:: You may obtain a copy of the License at
+::
+::     https://www.apache.org/licenses/LICENSE-2.0
+::
+:: Unless required by applicable law or agreed to in writing, software
+:: distributed under the License is distributed on an "AS IS" BASIS,
+:: WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+:: See the License for the specific language governing permissions and
+:: limitations under the License.
+
+SETLOCAL ENABLEDELAYEDEXPANSION
+
+:: Set LLVM directory.
+SET BAZEL_LLVM=C:\Program Files\LLVM
+
+:: Change directory to the root of the project.
+CD %~dp0\..
+if %errorlevel% neq 0 EXIT /B 1
+
+:: Set the standard version, [c++14|c++17|c++20|c++latest]
+:: https://msdn.microsoft.com/en-us/library/mt490614.aspx
+:: The default is c++14 if not set on command line.
+IF "%STD%"=="" SET STD=c++14
+
+:: Set the compilation_mode (fastbuild|opt|dbg)
+:: https://docs.bazel.build/versions/master/user-manual.html#flag--compilation_mode
+:: The default is fastbuild
+IF "%COMPILATION_MODE%"=="" SET COMPILATION_MODE=fastbuild
+
+:: Copy the alternate option file, if specified.
+IF NOT "%ALTERNATE_OPTIONS%"=="" copy %ALTERNATE_OPTIONS% absl\base\options.h
+
+:: To upgrade Bazel, first download a new binary from
+:: https://github.com/bazelbuild/bazel/releases and copy it to
+:: /google/data/rw/teams/absl/kokoro/windows.
+::
+:: TODO(absl-team): Remove -Wno-microsoft-cast
+%KOKORO_GFILE_DIR%\bazel-5.1.1-windows-x86_64.exe ^
+  test ... ^
+  --compilation_mode=%COMPILATION_MODE% ^
+  --compiler=clang-cl ^
+  --copt=/std:%STD% ^
+  --copt=/WX ^
+  --copt=-Wno-microsoft-cast ^
+  --define=absl=1 ^
+  --distdir=%KOKORO_GFILE_DIR%\distdir ^
+  --features=external_include_paths ^
+  --keep_going ^
+  --test_env="GTEST_INSTALL_FAILURE_SIGNAL_HANDLER=1" ^
+  --test_env=TZDIR="%CD%\absl\time\internal\cctz\testdata\zoneinfo" ^
+  --test_output=errors ^
+  --test_tag_filters=-benchmark
+
+if %errorlevel% neq 0 EXIT /B 1
+EXIT /B 0
diff --git a/ci/windows_msvc_bazel.bat b/ci/windows_msvc_bazel.bat
new file mode 100755
index 00000000..11d9f350
--- /dev/null
+++ b/ci/windows_msvc_bazel.bat
@@ -0,0 +1,52 @@
+:: Copyright 2023 The Abseil Authors
+::
+:: Licensed under the Apache License, Version 2.0 (the "License");
+:: you may not use this file except in compliance with the License.
+:: You may obtain a copy of the License at
+::
+::     https://www.apache.org/licenses/LICENSE-2.0
+::
+:: Unless required by applicable law or agreed to in writing, software
+:: distributed under the License is distributed on an "AS IS" BASIS,
+:: WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+:: See the License for the specific language governing permissions and
+:: limitations under the License.
+
+SETLOCAL ENABLEDELAYEDEXPANSION
+
+:: Change directory to the root of the project.
+CD %~dp0\..
+if %errorlevel% neq 0 EXIT /B 1
+
+:: Set the standard version, [c++14|c++latest]
+:: https://msdn.microsoft.com/en-us/library/mt490614.aspx
+:: The default is c++14 if not set on command line.
+IF "%STD%"=="" SET STD=c++14
+
+:: Set the compilation_mode (fastbuild|opt|dbg)
+:: https://docs.bazel.build/versions/master/user-manual.html#flag--compilation_mode
+:: The default is fastbuild
+IF "%COMPILATION_MODE%"=="" SET COMPILATION_MODE=fastbuild
+
+:: Copy the alternate option file, if specified.
+IF NOT "%ALTERNATE_OPTIONS%"=="" copy %ALTERNATE_OPTIONS% absl\base\options.h
+
+:: To upgrade Bazel, first download a new binary from
+:: https://github.com/bazelbuild/bazel/releases and copy it to
+:: /google/data/rw/teams/absl/kokoro/windows.
+%KOKORO_GFILE_DIR%\bazel-5.1.1-windows-x86_64.exe ^
+  test ... ^
+  --compilation_mode=%COMPILATION_MODE% ^
+  --copt=/WX ^
+  --copt=/std:%STD% ^
+  --define=absl=1 ^
+  --distdir=%KOKORO_GFILE_DIR%\distdir ^
+  --features=external_include_paths ^
+  --keep_going ^
+  --test_env="GTEST_INSTALL_FAILURE_SIGNAL_HANDLER=1" ^
+  --test_env=TZDIR="%CD%\absl\time\internal\cctz\testdata\zoneinfo" ^
+  --test_output=errors ^
+  --test_tag_filters=-benchmark
+
+if %errorlevel% neq 0 EXIT /B 1
+EXIT /B 0
diff --git a/ci/windows_msvc_cmake.bat b/ci/windows_msvc_cmake.bat
new file mode 100755
index 00000000..743b6f79
--- /dev/null
+++ b/ci/windows_msvc_cmake.bat
@@ -0,0 +1,69 @@
+:: Copyright 2023 The Abseil Authors
+::
+:: Licensed under the Apache License, Version 2.0 (the "License");
+:: you may not use this file except in compliance with the License.
+:: You may obtain a copy of the License at
+::
+::     https://www.apache.org/licenses/LICENSE-2.0
+::
+:: Unless required by applicable law or agreed to in writing, software
+:: distributed under the License is distributed on an "AS IS" BASIS,
+:: WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+:: See the License for the specific language governing permissions and
+:: limitations under the License.
+
+SETLOCAL ENABLEDELAYEDEXPANSION
+
+:: Use GoogleTest v1.14.0
+SET ABSL_GOOGLETEST_COMMIT=f8d7d77c06936315286eb55f8de22cd23c188571
+
+IF EXIST %KOKORO_GFILE_DIR%\distdir\%ABSL_GOOGLETEST_COMMIT%.zip (
+  SET ABSL_GOOGLETEST_DOWNLOAD_URL=file://%KOKORO_GFILE_DIR%\distdir\%ABSL_GOOGLETEST_COMMIT%.zip
+) ELSE (
+  SET ABSL_GOOGLETEST_DOWNLOAD_URL=https://github.com/google/googletest/archive/%ABSL_GOOGLETEST_COMMIT%.zip
+)
+
+:: Replace '\' with '/' in Windows paths for CMake.
+:: Note that this cannot go inside the IF block above, because BAT files are weird.
+SET ABSL_GOOGLETEST_DOWNLOAD_URL=%ABSL_GOOGLETEST_DOWNLOAD_URL:\=/%
+
+IF EXIST "C:\Program Files\CMake\bin\" (
+  SET CMAKE_BIN="C:\Program Files\CMake\bin\cmake.exe"
+  SET CTEST_BIN="C:\Program Files\CMake\bin\ctest.exe"
+) ELSE (
+  SET CMAKE_BIN="cmake.exe"
+  SET CTEST_BIN="ctest.exe"
+)
+
+SET CTEST_OUTPUT_ON_FAILURE=1
+SET CMAKE_BUILD_PARALLEL_LEVEL=16
+SET CTEST_PARALLEL_LEVEL=16
+
+:: Change directory to the root of the project.
+CD %~dp0\..
+if %errorlevel% neq 0 EXIT /B 1
+
+SET TZDIR=%CD%\absl\time\internal\cctz\testdata\zoneinfo
+
+MKDIR "build"
+CD "build"
+
+SET CXXFLAGS="/WX"
+
+%CMAKE_BIN% ^
+  -DABSL_BUILD_TEST_HELPERS=ON ^
+  -DABSL_BUILD_TESTING=ON ^
+  -DABSL_GOOGLETEST_DOWNLOAD_URL=%ABSL_GOOGLETEST_DOWNLOAD_URL% ^
+  -DBUILD_SHARED_LIBS=%ABSL_CMAKE_BUILD_SHARED% ^
+  -DCMAKE_CXX_STANDARD=%ABSL_CMAKE_CXX_STANDARD% ^
+  -G "%ABSL_CMAKE_GENERATOR%" ^
+  ..
+IF %errorlevel% neq 0 EXIT /B 1
+
+%CMAKE_BIN% --build . --target ALL_BUILD --config %ABSL_CMAKE_BUILD_TYPE%
+IF %errorlevel% neq 0 EXIT /B 1
+
+%CTEST_BIN% -C %ABSL_CMAKE_BUILD_TYPE% -E "absl_lifetime_test|absl_symbolize_test"
+IF %errorlevel% neq 0 EXIT /B 1
+
+EXIT /B 0
diff --git a/create_lts.py b/create_lts.py
index 56170806..642b8847 100755
--- a/create_lts.py
+++ b/create_lts.py
@@ -33,7 +33,7 @@ def ReplaceStringsInFile(filename, replacement_dict):
       values
 
   Raises:
-    Exception: A failure occured
+    Exception: A failure occurred
   """
   f = open(filename, 'r')
   content = f.read()
@@ -62,7 +62,7 @@ def StripContentBetweenTags(filename, strip_begin_tag, strip_end_tag):
     strip_end_tag: the end of the content to be removed
 
   Raises:
-    Exception: A failure occured
+    Exception: A failure occurred
   """
   f = open(filename, 'r')
   content = f.read()
author	Benjamin Barenblat <bbaren@google.com>	2023-09-07 13:16:09 -0400
committer	Benjamin Barenblat <bbaren@google.com>	2023-09-07 13:16:09 -0400
commit	6fdbff8bbce2a1debdc060df381f39e3dcfb65af (patch)
tree	71f1ef38477a65d5cce472fc042c90087c2bb351
parent	8d4a80fe37176b1170d7dce0772dea9584ec3e32 (diff)
parent	29bf8085f3bf17b84d30e34b3d7ff8248fda404e (diff)