18 files changed, 178 insertions, 223 deletions
diff --git a/CMake/AbseilDll.cmake b/CMake/AbseilDll.cmake
index 518c469b..4f7a287c 100644
--- a/CMake/AbseilDll.cmake
+++ b/CMake/AbseilDll.cmake
@@ -90,7 +90,6 @@ set(ABSL_INTERNAL_DLL_FILES
   "debugging/failure_signal_handler.cc"
   "debugging/failure_signal_handler.h"
   "debugging/leak_check.h"
-  "debugging/leak_check_disable.cc"
   "debugging/stacktrace.cc"
   "debugging/stacktrace.h"
   "debugging/symbolize.cc"
@@ -345,6 +344,7 @@ set(ABSL_INTERNAL_DLL_FILES
   "types/internal/span.h"
   "types/variant.h"
   "utility/utility.h"
+  "debugging/leak_check.cc"
 )
 
 set(ABSL_INTERNAL_DLL_TARGETS
@@ -355,7 +355,6 @@ set(ABSL_INTERNAL_DLL_TARGETS
   "debugging_internal"
   "demangle_internal"
   "leak_check"
-  "leak_check_disable"
   "stack_consumption"
   "debugging"
   "hash"
diff --git a/absl/base/config.h b/absl/base/config.h
index 429dd353..3f5ace3f 100644
--- a/absl/base/config.h
+++ b/absl/base/config.h
@@ -797,10 +797,27 @@ static_assert(ABSL_INTERNAL_INLINE_NAMESPACE_STR[0] != 'h' ||
 // ABSL_HAVE_LEAK_SANITIZER
 //
 // LeakSanitizer (or lsan) is a detector of memory leaks.
+// https://clang.llvm.org/docs/LeakSanitizer.html
+// https://github.com/google/sanitizers/wiki/AddressSanitizerLeakSanitizer
+//
+// The macro ABSL_HAVE_LEAK_SANITIZER can be used to detect at compile-time
+// whether the LeakSanitizer is potentially available. However, just because the
+// LeakSanitizer is available does not mean it is active. Use the
+// always-available run-time interface in //absl/debugging/leak_check.h for
+// interacting with LeakSanitizer.
 #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
+// LeakSanitizer (-fsanitize=leak), so GCC users of -fsanitize=leak should also
+// use -DLEAK_SANITIZER.
+#define ABSL_HAVE_LEAK_SANITIZER 1
+// Clang standalone LeakSanitizer (-fsanitize=leak)
 #elif ABSL_HAVE_FEATURE(leak_sanitizer)
 #define ABSL_HAVE_LEAK_SANITIZER 1
+#elif defined(ABSL_HAVE_ADDRESS_SANITIZER)
+// GCC or Clang using the LeakSanitizer integrated into AddressSanitizer.
+#define ABSL_HAVE_LEAK_SANITIZER 1
 #endif
 
 // ABSL_HAVE_CLASS_TEMPLATE_ARGUMENT_DEDUCTION
diff --git a/absl/base/internal/sysinfo.cc b/absl/base/internal/sysinfo.cc
index a7cfb461..c8366df1 100644
--- a/absl/base/internal/sysinfo.cc
+++ b/absl/base/internal/sysinfo.cc
@@ -124,7 +124,6 @@ int Win32NumCPUs() {
 
 }  // namespace
 
-
 static int GetNumCPUs() {
 #if defined(__myriad2__)
   return 1;
diff --git a/absl/copts/AbseilConfigureCopts.cmake b/absl/copts/AbseilConfigureCopts.cmake
index 15d6c895..73435e99 100644
--- a/absl/copts/AbseilConfigureCopts.cmake
+++ b/absl/copts/AbseilConfigureCopts.cmake
@@ -1,8 +1,6 @@
 # See absl/copts/copts.py and absl/copts/generate_copts.py
 include(GENERATED_AbseilCopts)
 
-set(ABSL_LSAN_LINKOPTS "")
-set(ABSL_HAVE_LSAN OFF)
 set(ABSL_DEFAULT_LINKOPTS "")
 
 if (BUILD_SHARED_LIBS AND MSVC)
@@ -85,14 +83,6 @@ elseif(CMAKE_CXX_COMPILER_ID MATCHES "Clang")  # MATCHES so we get both Clang an
   else()
     set(ABSL_DEFAULT_COPTS "${ABSL_LLVM_FLAGS}")
     set(ABSL_TEST_COPTS "${ABSL_LLVM_FLAGS};${ABSL_LLVM_TEST_FLAGS}")
-    if(CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
-      # AppleClang doesn't have lsan
-      # https://developer.apple.com/documentation/code_diagnostics
-      if(NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 3.5)
-        set(ABSL_LSAN_LINKOPTS "-fsanitize=leak")
-        set(ABSL_HAVE_LSAN ON)
-      endif()
-    endif()
   endif()
 elseif(CMAKE_CXX_COMPILER_ID STREQUAL "MSVC")
   set(ABSL_DEFAULT_COPTS "${ABSL_MSVC_FLAGS}")
diff --git a/absl/debugging/BUILD.bazel b/absl/debugging/BUILD.bazel
index 3c4ea8dc..7f5c1cad 100644
--- a/absl/debugging/BUILD.bazel
+++ b/absl/debugging/BUILD.bazel
@@ -225,6 +225,7 @@ cc_library(
     name = "leak_check",
     srcs = ["leak_check.cc"],
     hdrs = ["leak_check.h"],
+    copts = ABSL_DEFAULT_COPTS,
     linkopts = ABSL_DEFAULT_LINKOPTS,
     deps = [
         "//absl/base:config",
@@ -232,98 +233,33 @@ cc_library(
     ],
 )
 
-# Adding a dependency to leak_check_disable will disable
-# sanitizer leak checking (asan/lsan) in a test without
-# the need to mess around with build features.
-cc_library(
-    name = "leak_check_disable",
-    srcs = ["leak_check_disable.cc"],
-    linkopts = ABSL_DEFAULT_LINKOPTS,
-    linkstatic = 1,
-    deps = ["//absl/base:config"],
-    alwayslink = 1,
-)
-
-# These targets exists for use in tests only, explicitly configuring the
-# LEAK_SANITIZER macro. It must be linked with -fsanitize=leak for lsan.
-ABSL_LSAN_LINKOPTS = select({
-    "//absl:clang_compiler": ["-fsanitize=leak"],
-    "//conditions:default": [],
-})
-
-cc_library(
-    name = "leak_check_api_enabled_for_testing",
-    testonly = 1,
-    srcs = ["leak_check.cc"],
-    hdrs = ["leak_check.h"],
-    copts = select({
-        "//absl:clang_compiler": ["-DLEAK_SANITIZER"],
-        "//conditions:default": [],
-    }),
-    linkopts = ABSL_DEFAULT_LINKOPTS,
-    visibility = ["//visibility:private"],
-    deps = [
-        "//absl/base:config",
-        "//absl/base:core_headers",
-    ],
-)
-
-cc_library(
-    name = "leak_check_api_disabled_for_testing",
-    testonly = 1,
-    srcs = ["leak_check.cc"],
-    hdrs = ["leak_check.h"],
-    copts = ["-ULEAK_SANITIZER"],
-    linkopts = ABSL_DEFAULT_LINKOPTS,
-    visibility = ["//visibility:private"],
-    deps = [
-        "//absl/base:config",
-        "//absl/base:core_headers",
-    ],
-)
-
 cc_test(
     name = "leak_check_test",
     srcs = ["leak_check_test.cc"],
-    copts = select({
-        "//absl:clang_compiler": ["-DABSL_EXPECT_LEAK_SANITIZER"],
-        "//conditions:default": [],
-    }),
-    linkopts = ABSL_LSAN_LINKOPTS + ABSL_DEFAULT_LINKOPTS,
-    tags = ["notsan"],
-    deps = [
-        ":leak_check_api_enabled_for_testing",
-        "//absl/base",
-        "@com_google_googletest//:gtest_main",
-    ],
-)
-
-cc_test(
-    name = "leak_check_no_lsan_test",
-    srcs = ["leak_check_test.cc"],
-    copts = ["-UABSL_EXPECT_LEAK_SANITIZER"],
+    copts = ABSL_TEST_COPTS,
     linkopts = ABSL_DEFAULT_LINKOPTS,
-    tags = ["noasan"],
+    tags = ["notsan"],
     deps = [
-        ":leak_check_api_disabled_for_testing",
-        "//absl/base",  # for raw_logging
+        ":leak_check",
+        "//absl/base:config",
+        "//absl/base:raw_logging_internal",
         "@com_google_googletest//:gtest_main",
     ],
 )
 
-# Test that leak checking is skipped when lsan is enabled but
-# ":leak_check_disable" is linked in.
-#
-# This test should fail in the absence of a dependency on ":leak_check_disable"
-cc_test(
-    name = "disabled_leak_check_test",
+# Binary that leaks memory and expects to fail on exit.  This isn't a
+# test that expected to pass on its own; it exists to be called by a
+# script that checks exit status and output.
+# TODO(absl-team): Write a test to run this with a script that
+# verifies that it correctly fails.
+cc_binary(
+    name = "leak_check_fail_test_binary",
     srcs = ["leak_check_fail_test.cc"],
-    linkopts = ABSL_LSAN_LINKOPTS + ABSL_DEFAULT_LINKOPTS,
-    tags = ["notsan"],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
     deps = [
-        ":leak_check_api_enabled_for_testing",
-        ":leak_check_disable",
-        "//absl/base",
+        ":leak_check",
+        "//absl/base:raw_logging_internal",
         "@com_google_googletest//:gtest_main",
     ],
 )
@@ -356,3 +292,18 @@ cc_test(
         "@com_google_googletest//:gtest_main",
     ],
 )
+
+cc_binary(
+    name = "stacktrace_benchmark",
+    testonly = 1,
+    srcs = ["stacktrace_benchmark.cc"],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    tags = ["benchmark"],
+    deps = [
+        ":stacktrace",
+        "//absl/base:config",
+        "//absl/base:core_headers",
+        "@com_github_google_benchmark//:benchmark_main",
+    ],
+)
diff --git a/absl/debugging/CMakeLists.txt b/absl/debugging/CMakeLists.txt
index 5850bdd0..7507ff3b 100644
--- a/absl/debugging/CMakeLists.txt
+++ b/absl/debugging/CMakeLists.txt
@@ -218,42 +218,6 @@ absl_cc_library(
   PUBLIC
 )
 
-absl_cc_library(
-  NAME
-    leak_check_disable
-  SRCS
-    "leak_check_disable.cc"
-  COPTS
-    ${ABSL_DEFAULT_COPTS}
-  PUBLIC
-)
-
-absl_cc_library(
-  NAME
-    leak_check_api_enabled_for_testing
-  HDRS
-    "leak_check.h"
-  SRCS
-    "leak_check.cc"
-  COPTS
-    ${ABSL_DEFAULT_COPTS}
-    $<$<BOOL:${ABSL_HAVE_LSAN}>:-DLEAK_SANITIZER>
-  TESTONLY
-)
-
-absl_cc_library(
-  NAME
-    leak_check_api_disabled_for_testing
-  HDRS
-    "leak_check.h"
-  SRCS
-    "leak_check.cc"
-  COPTS
-    ${ABSL_DEFAULT_COPTS}
-    "-ULEAK_SANITIZER"
-  TESTONLY
-)
-
 absl_cc_test(
   NAME
     leak_check_test
@@ -261,43 +225,11 @@ absl_cc_test(
     "leak_check_test.cc"
   COPTS
     ${ABSL_TEST_COPTS}
-    "$<$<BOOL:${ABSL_HAVE_LSAN}>:-DABSL_EXPECT_LEAK_SANITIZER>"
   LINKOPTS
-    "${ABSL_LSAN_LINKOPTS}"
-  DEPS
-    absl::leak_check_api_enabled_for_testing
-    absl::base
-    GTest::gmock_main
-)
-
-absl_cc_test(
-  NAME
-    leak_check_no_lsan_test
-  SRCS
-    "leak_check_test.cc"
-  COPTS
-    ${ABSL_TEST_COPTS}
-    "-UABSL_EXPECT_LEAK_SANITIZER"
-  DEPS
-    absl::leak_check_api_disabled_for_testing
-    absl::base
-    GTest::gmock_main
-)
-
-absl_cc_test(
-  NAME
-    disabled_leak_check_test
-  SRCS
-    "leak_check_fail_test.cc"
-  COPTS
-    ${ABSL_TEST_COPTS}
-  LINKOPTS
-    "${ABSL_LSAN_LINKOPTS}"
+    ${ABSL_DEFAULT_LINKOPTS}
   DEPS
-    absl::leak_check_api_enabled_for_testing
-    absl::leak_check_disable
+    absl::leak_check
     absl::base
-    absl::raw_logging_internal
     GTest::gmock_main
 )
 
diff --git a/absl/debugging/leak_check.cc b/absl/debugging/leak_check.cc
index 764ca0ad..195e82bf 100644
--- a/absl/debugging/leak_check.cc
+++ b/absl/debugging/leak_check.cc
@@ -11,29 +11,19 @@
 // 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.
-
+//
 // Wrappers around lsan_interface functions.
-// When lsan is not linked in, these functions are not available,
-// therefore Abseil code which depends on these functions is conditioned on the
-// definition of LEAK_SANITIZER.
-#include "absl/base/attributes.h"
-#include "absl/debugging/leak_check.h"
+//
+// These are always-available run-time functions manipulating the LeakSanitizer,
+// even when the lsan_interface (and LeakSanitizer) is not available. When
+// LeakSanitizer is not linked in, these functions become no-op stubs.
 
-#ifndef LEAK_SANITIZER
+#include "absl/debugging/leak_check.h"
 
-namespace absl {
-ABSL_NAMESPACE_BEGIN
-bool HaveLeakSanitizer() { return false; }
-bool LeakCheckerIsActive() { return false; }
-void DoIgnoreLeak(const void*) { }
-void RegisterLivePointers(const void*, size_t) { }
-void UnRegisterLivePointers(const void*, size_t) { }
-LeakCheckDisabler::LeakCheckDisabler() { }
-LeakCheckDisabler::~LeakCheckDisabler() { }
-ABSL_NAMESPACE_END
-}  // namespace absl
+#include "absl/base/attributes.h"
+#include "absl/base/config.h"
 
-#else
+#if defined(ABSL_HAVE_LEAK_SANITIZER)
 
 #include <sanitizer/lsan_interface.h>
 
@@ -66,4 +56,18 @@ LeakCheckDisabler::~LeakCheckDisabler() { __lsan_enable(); }
 ABSL_NAMESPACE_END
 }  // namespace absl
 
-#endif  // LEAK_SANITIZER
+#else  // defined(ABSL_HAVE_LEAK_SANITIZER)
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+bool HaveLeakSanitizer() { return false; }
+bool LeakCheckerIsActive() { return false; }
+void DoIgnoreLeak(const void*) { }
+void RegisterLivePointers(const void*, size_t) { }
+void UnRegisterLivePointers(const void*, size_t) { }
+LeakCheckDisabler::LeakCheckDisabler() { }
+LeakCheckDisabler::~LeakCheckDisabler() { }
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // defined(ABSL_HAVE_LEAK_SANITIZER)
diff --git a/absl/debugging/leak_check.h b/absl/debugging/leak_check.h
index 5fc2b052..eff162f6 100644
--- a/absl/debugging/leak_check.h
+++ b/absl/debugging/leak_check.h
@@ -24,7 +24,24 @@
 // Note: this leak checking API is not yet supported in MSVC.
 // Leak checking is enabled by default in all ASan builds.
 //
-// See https://github.com/google/sanitizers/wiki/AddressSanitizerLeakSanitizer
+// https://clang.llvm.org/docs/LeakSanitizer.html
+// https://github.com/google/sanitizers/wiki/AddressSanitizerLeakSanitizer
+//
+// GCC and Clang both automatically enable LeakSanitizer when AddressSanitizer
+// is enabled. To use the mode, simply pass `-fsanitize=address` to both the
+// compiler and linker. An example Bazel command could be
+//
+//   $ bazel test --copt=-fsanitize=address --linkopt=-fsanitize=address ...
+//
+// GCC and Clang auto support a standalone LeakSanitizer mode (a mode which does
+// not also use AddressSanitizer). To use the mode, simply pass
+// `-fsanitize=leak` to both the compiler and linker. Since GCC does not
+// currently provide a way of detecting this mode at compile-time, GCC users
+// must also pass -DLEAK_SANIITIZER to the compiler. An example Bazel command
+// could be
+//
+//   $ bazel test --copt=-DLEAK_SANITIZER --copt=-fsanitize=leak
+//     --linkopt=-fsanitize=leak ...
 //
 // -----------------------------------------------------------------------------
 #ifndef ABSL_DEBUGGING_LEAK_CHECK_H_
diff --git a/absl/debugging/leak_check_disable.cc b/absl/debugging/leak_check_disable.cc
deleted file mode 100644
index 924d6e3d..00000000
--- a/absl/debugging/leak_check_disable.cc
+++ /dev/null
@@ -1,20 +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.
-
-// Disable LeakSanitizer when this file is linked in.
-// This function overrides __lsan_is_turned_off from sanitizer/lsan_interface.h
-extern "C" int __lsan_is_turned_off();
-extern "C" int __lsan_is_turned_off() {
-  return 1;
-}
diff --git a/absl/debugging/leak_check_test.cc b/absl/debugging/leak_check_test.cc
index 9fcfc8e5..6a42e31b 100644
--- a/absl/debugging/leak_check_test.cc
+++ b/absl/debugging/leak_check_test.cc
@@ -15,27 +15,24 @@
 #include <string>
 
 #include "gtest/gtest.h"
+#include "absl/base/config.h"
 #include "absl/base/internal/raw_logging.h"
 #include "absl/debugging/leak_check.h"
 
 namespace {
 
-TEST(LeakCheckTest, DetectLeakSanitizer) {
-#ifdef ABSL_EXPECT_LEAK_SANITIZER
-  EXPECT_TRUE(absl::HaveLeakSanitizer());
-  EXPECT_TRUE(absl::LeakCheckerIsActive());
-#else
-  EXPECT_FALSE(absl::HaveLeakSanitizer());
-  EXPECT_FALSE(absl::LeakCheckerIsActive());
-#endif
-}
-
 TEST(LeakCheckTest, IgnoreLeakSuppressesLeakedMemoryErrors) {
+  if (!absl::LeakCheckerIsActive()) {
+    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());
 }
 
 TEST(LeakCheckTest, LeakCheckDisablerIgnoresLeak) {
+  if (!absl::LeakCheckerIsActive()) {
+    GTEST_SKIP() << "LeakChecker is not active";
+  }
   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());
diff --git a/absl/debugging/stacktrace_benchmark.cc b/absl/debugging/stacktrace_benchmark.cc
new file mode 100644
index 00000000..9360bafe
--- /dev/null
+++ b/absl/debugging/stacktrace_benchmark.cc
@@ -0,0 +1,55 @@
+// Copyright 2022 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/attributes.h"
+#include "absl/base/config.h"
+#include "absl/base/optimization.h"
+#include "absl/debugging/stacktrace.h"
+#include "benchmark/benchmark.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace {
+
+static constexpr int kMaxStackDepth = 100;
+static constexpr int kCacheSize = (1 << 16);
+void* pcs[kMaxStackDepth];
+
+ABSL_ATTRIBUTE_NOINLINE void func(benchmark::State& state, int x, int depth) {
+  if (x <= 0) {
+    // Touch a significant amount of memory so that the stack is likely to be
+    // not cached in the L1 cache.
+    state.PauseTiming();
+    int* arr = new int[kCacheSize];
+    for (int i = 0; i < kCacheSize; ++i) benchmark::DoNotOptimize(arr[i] = 100);
+    delete[] arr;
+    state.ResumeTiming();
+    benchmark::DoNotOptimize(absl::GetStackTrace(pcs, depth, 0));
+    return;
+  }
+  ABSL_BLOCK_TAIL_CALL_OPTIMIZATION();
+  func(state, --x, depth);
+}
+
+void BM_GetStackTrace(benchmark::State& state) {
+  int depth = state.range(0);
+  for (auto s : state) {
+    func(state, depth, depth);
+  }
+}
+
+BENCHMARK(BM_GetStackTrace)->DenseRange(10, kMaxStackDepth, 10);
+}  // namespace
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/absl/flags/flag_test.cc b/absl/flags/flag_test.cc
index 05ec79e8..845b4eba 100644
--- a/absl/flags/flag_test.cc
+++ b/absl/flags/flag_test.cc
@@ -854,7 +854,9 @@ ABSL_RETIRED_FLAG(bool, old_bool_flag, true, "old descr");
 ABSL_RETIRED_FLAG(int, old_int_flag, (int)std::sqrt(10), "old descr");
 ABSL_RETIRED_FLAG(std::string, old_str_flag, "", absl::StrCat("old ", "descr"));
 
-bool initializaion_order_fiasco_test = [] {
+namespace {
+
+bool initialization_order_fiasco_test ABSL_ATTRIBUTE_UNUSED = [] {
   // Iterate over all the flags during static initialization.
   // This should not trigger ASan's initialization-order-fiasco.
   auto* handle1 = absl::FindCommandLineFlag("flag_on_separate_file");
@@ -865,8 +867,6 @@ bool initializaion_order_fiasco_test = [] {
   return true;
 }();
 
-namespace {
-
 TEST_F(FlagTest, TestRetiredFlagRegistration) {
   auto* handle = absl::FindCommandLineFlag("old_bool_flag");
   EXPECT_TRUE(handle->IsOfType<bool>());
diff --git a/absl/flags/internal/usage_test.cc b/absl/flags/internal/usage_test.cc
index 044d71c8..6a65a1a3 100644
--- a/absl/flags/internal/usage_test.cc
+++ b/absl/flags/internal/usage_test.cc
@@ -47,8 +47,10 @@ struct UDT {
   UDT(const UDT&) = default;
   UDT& operator=(const UDT&) = default;
 };
-bool AbslParseFlag(absl::string_view, UDT*, std::string*) { return true; }
-std::string AbslUnparseFlag(const UDT&) { return "UDT{}"; }
+static bool AbslParseFlag(absl::string_view, UDT*, std::string*) {
+  return true;
+}
+static std::string AbslUnparseFlag(const UDT&) { return "UDT{}"; }
 
 ABSL_FLAG(UDT, usage_reporting_test_flag_05, {},
           "usage_reporting_test_flag_05 help message");
diff --git a/absl/hash/internal/city_test.cc b/absl/hash/internal/city_test.cc
index 251d381d..1bbf02e0 100644
--- a/absl/hash/internal/city_test.cc
+++ b/absl/hash/internal/city_test.cc
@@ -22,6 +22,7 @@
 namespace absl {
 ABSL_NAMESPACE_BEGIN
 namespace hash_internal {
+namespace {
 
 static const uint64_t k0 = 0xc3a5c85c97cb3127ULL;
 static const uint64_t kSeed0 = 1234567;
@@ -590,6 +591,7 @@ TEST(CityHashTest, Unchanging) {
   TestUnchanging(testdata[i], 0, kDataSize);
 }
 
+}  // namespace
 }  // namespace hash_internal
 ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/profiling/internal/exponential_biased_test.cc b/absl/profiling/internal/exponential_biased_test.cc
index 5675001d..6a6c317e 100644
--- a/absl/profiling/internal/exponential_biased_test.cc
+++ b/absl/profiling/internal/exponential_biased_test.cc
@@ -29,6 +29,7 @@ using ::testing::Ge;
 namespace absl {
 ABSL_NAMESPACE_BEGIN
 namespace profiling_internal {
+namespace {
 
 MATCHER_P2(IsBetween, a, b,
            absl::StrCat(std::string(negation ? "isn't" : "is"), " between ", a,
@@ -194,6 +195,7 @@ TEST(ExponentialBiasedTest, InitializationModes) {
   EXPECT_THAT(eb_stack.GetSkipCount(2), Ge(0));
 }
 
+}  // namespace
 }  // namespace profiling_internal
 ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/strings/str_format_test.cc b/absl/strings/str_format_test.cc
index c60027ad..804e6c22 100644
--- a/absl/strings/str_format_test.cc
+++ b/absl/strings/str_format_test.cc
@@ -719,6 +719,7 @@ TEST_F(FormatWrapperTest, ParsedFormat) {
 ABSL_NAMESPACE_END
 }  // namespace absl
 
+namespace {
 using FormatExtensionTest = ::testing::Test;
 
 struct Point {
@@ -750,6 +751,7 @@ TEST_F(FormatExtensionTest, AbslFormatConvertExample) {
   // FormatUntyped will return false for bad character.
   EXPECT_FALSE(absl::FormatUntyped(&actual, f1, {absl::FormatArg(p)}));
 }
+}  // namespace
 
 // Some codegen thunks that we can use to easily dump the generated assembly for
 // different StrFormat calls.
diff --git a/absl/synchronization/BUILD.bazel b/absl/synchronization/BUILD.bazel
index a0492c55..4e175892 100644
--- a/absl/synchronization/BUILD.bazel
+++ b/absl/synchronization/BUILD.bazel
@@ -97,8 +97,8 @@ cc_library(
     deps = [
         ":graphcycles_internal",
         ":kernel_timeout_internal",
-        "//absl/base",
         "//absl/base:atomic_hook",
+        "//absl/base",
         "//absl/base:base_internal",
         "//absl/base:config",
         "//absl/base:core_headers",
@@ -108,7 +108,9 @@ cc_library(
         "//absl/debugging:stacktrace",
         "//absl/debugging:symbolize",
         "//absl/time",
-    ],
+    ] + select({
+        "//conditions:default": [],
+    }),
 )
 
 cc_test(
diff --git a/absl/time/internal/cctz/BUILD.bazel b/absl/time/internal/cctz/BUILD.bazel
index bdc2e309..f0e7ae13 100644
--- a/absl/time/internal/cctz/BUILD.bazel
+++ b/absl/time/internal/cctz/BUILD.bazel
@@ -85,7 +85,11 @@ cc_library(
     deps = [
         ":civil_time",
         "//absl/base:config",
-    ],
+    ] + select(
+        {
+            "//conditions:default": [],
+        },
+    ),
 )
 
 ### tests