Export of internal Abseil changes.

--
cd076f55c1fa600131f6dda392533dfe61679fc0 by Abseil Team <absl-team@google.com>:

Internal change

PiperOrigin-RevId: 224008762

--
e05f62b01286d51044ff86ec6ef565749b9faf82 by Abseil Team <absl-team@google.com>:

Create a pow10() test helper function to compute guaranteed-precise double values of 10^x. Not all standard libraries ship bit-accurate pow() functions, causing tests to fail that rely on expected values generated by it.

PiperOrigin-RevId: 223883762

--
fd88e5e3f7ab80f7f5df9fd1488cd58b4573be69 by Abseil Team <absl-team@google.com>:

Remove some absl:: qualifications to work around inline namespace bugs on MSVC 2015.

PiperOrigin-RevId: 223869642

--
6276cfff969d596edd36a2bbaba65ee045808903 by Abseil Team <absl-team@google.com>:

Update absl/memory/CMakeLists.txt to use new functions
i.e. absl_cc_(library|test)

PiperOrigin-RevId: 223854224

--
359de9afc7a34c975fd3e0cbc52afd96637d97bd by Chris Kennelly <ckennelly@google.com>:

Mark spinlock_benchmark_common as alwayslink = 1.

PiperOrigin-RevId: 223844536

--
450cd8cbe2789a6d54ed1eb87170259bb334f8b9 by Abseil Team <absl-team@google.com>:

Support .* (pointer-to-member dereference) expressions in demangle.cc.

PiperOrigin-RevId: 223826797

--
772ca92179c3634f3e31a80bbc272ed8022e3572 by Abseil Team <absl-team@google.com>:

Fix misspellings in absl::variant comments and replace a ' with a `.

PiperOrigin-RevId: 223807911

--
35dcdc2fbf299d195658aac101887f6dcad1de2f by Abseil Team <absl-team@google.com>:

Bug fix in CMakeLists.txt file (SRCS --> HDRS).

The compressed_tuple header-only library is being defined
with the SRCS parameter instead of the HDRS parameter and
this has been observed to cause some builds on some platforms
to attempt to create a static library from it which fails
since there are no .cc sources.

PiperOrigin-RevId: 223805367

--
4a57a3d2045bb137c0c97958e45ce425190b8d3e by Chris Kennelly <ckennelly@google.com>:

Add test that absl::make_unique value initializes memory.

PiperOrigin-RevId: 223801819

--
dfe8289d7f4dcc6bb568a26aaf192a89e896bdfd by Chris Kennelly <ckennelly@google.com>:

SpinLock: Use exchange to avoid missing wakeups.

The default fast path for SpinLock::Unlock does not use an atomic.  If the
SpinLock becomes contended while we are unlocking between lockword_.load and
lockword_.store, we will fail to wake up the new waiter.  This can cause
unexpected latency spikes.

PiperOrigin-RevId: 223800369

--
9b9d35df786482f0016f77dd31691eff81503d23 by Abseil Team <absl-team@google.com>:

Update absl/hash/CMakeLists.txt to use new functions
i.e. absl_cc_(library|test)

PiperOrigin-RevId: 223755819

--
c2014e2704b87e7cdce2d2a0287c7e2397752296 by Abseil Team <absl-team@google.com>:

Update absl/debugging/CMakeLists.txt to use new functions
i.e. absl_cc_(library|test)

PiperOrigin-RevId: 223751986

--
d83a4e09126400e3fd80645cb03ee558f532271e by Derek Mauro <dmauro@google.com>:

Cleanup synchronization benchmarks.

PiperOrigin-RevId: 223589416

--
fad140b473586531b5b12843f942ec27dfcf5e93 by CJ Johnson <johnsoncj@google.com>:

Makes unifies the order of forward_iterator and input_iterator overloads

PiperOrigin-RevId: 223580660

--
6cd7c96faa7cc5f79f574e35a1b13837ef187d05 by Abseil Team <absl-team@google.com>:

Internal Change.

PiperOrigin-RevId: 223561629

--
bd2e545356b0f548af0e3c14bb2f7f0e712e49d0 by Shaindel Schwartz <shaindel@google.com>:

Remove misleading comments. try_emplace() does not exist for the hash_set containers.

PiperOrigin-RevId: 223543089

--
0cd380a53b587eb7aacc4003a4a3bbb6c78d7c10 by Derek Mauro <dmauro@google.com>:

Internal change

PiperOrigin-RevId: 223512551

--
7156dfee599cb72e9adddfe0e6ae07a95ddf10bb by Greg Miller <jgm@google.com>:

Fixes UB that would result from constructing, multiplying, or dividing a
Duration with a double "NaN" value. This CL changes the absl::Duration
*implementation* to return an InfiniteDuration value that has the same sign as
the given NaN.

PiperOrigin-RevId: 223407499

--
196b7d18609958267951882baf7f9429e49bcafa by CJ Johnson <johnsoncj@google.com>:

Addresses NVCC+MSVC compilation bug where `inlined_capacity()` was not considered valid in constexpr

PiperOrigin-RevId: 223397718
GitOrigin-RevId: cd076f55c1fa600131f6dda392533dfe61679fc0
Change-Id: I5423ca6470f661a7c6f73aa8fee49990446f157f

29 files changed, 1092 insertions, 361 deletions

diff --git a/absl/base/BUILD.bazel b/absl/base/BUILD.bazel
index 44de05e3..4566c697 100644
--- a/absl/base/BUILD.bazel
+++ b/absl/base/BUILD.bazel
@@ -107,6 +107,7 @@ cc_library(
         "internal/identity.h",
         "internal/inline_variable.h",
         "internal/invoke.h",
+        "internal/scheduling_mode.h",
     ],
     copts = ABSL_DEFAULT_COPTS,
     visibility = [
@@ -314,6 +315,33 @@ cc_test(
 )
 
 cc_library(
+    name = "spinlock_benchmark_common",
+    testonly = 1,
+    srcs = ["internal/spinlock_benchmark.cc"],
+    copts = ABSL_DEFAULT_COPTS,
+    visibility = [
+        "//absl/base:__pkg__",
+    ],
+    deps = [
+        ":base",
+        ":base_internal",
+        "//absl/synchronization",
+        "@com_github_google_benchmark//:benchmark_main",
+    ],
+    alwayslink = 1,
+)
+
+cc_binary(
+    name = "spinlock_benchmark",
+    testonly = 1,
+    copts = ABSL_DEFAULT_COPTS,
+    visibility = ["//visibility:private"],
+    deps = [
+        ":spinlock_benchmark_common",
+    ],
+)
+
+cc_library(
     name = "endian",
     hdrs = [
         "internal/endian.h",
diff --git a/absl/base/internal/spinlock.h b/absl/base/internal/spinlock.h
index dcce0109..eb3eec9c 100644
--- a/absl/base/internal/spinlock.h
+++ b/absl/base/internal/spinlock.h
@@ -101,8 +101,8 @@ class LOCKABLE SpinLock {
   inline void Unlock() UNLOCK_FUNCTION() {
     ABSL_TSAN_MUTEX_PRE_UNLOCK(this, 0);
     uint32_t lock_value = lockword_.load(std::memory_order_relaxed);
-    lockword_.store(lock_value & kSpinLockCooperative,
-                    std::memory_order_release);
+    lock_value = lockword_.exchange(lock_value & kSpinLockCooperative,
+                                    std::memory_order_release);
 
     if ((lock_value & kSpinLockDisabledScheduling) != 0) {
       base_internal::SchedulingGuard::EnableRescheduling(true);
diff --git a/absl/base/internal/spinlock_benchmark.cc b/absl/base/internal/spinlock_benchmark.cc
new file mode 100644
index 00000000..907d3e27
--- /dev/null
+++ b/absl/base/internal/spinlock_benchmark.cc
@@ -0,0 +1,52 @@
+// 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
+//
+//      http://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.
+
+// See also //absl/synchronization:mutex_benchmark for a comparison of SpinLock
+// and Mutex performance under varying levels of contention.
+
+#include "absl/base/internal/raw_logging.h"
+#include "absl/base/internal/scheduling_mode.h"
+#include "absl/base/internal/spinlock.h"
+#include "absl/synchronization/internal/create_thread_identity.h"
+#include "benchmark/benchmark.h"
+
+namespace {
+
+template <absl::base_internal::SchedulingMode scheduling_mode>
+static void BM_SpinLock(benchmark::State& state) {
+  // Ensure a ThreadIdentity is installed.
+  ABSL_INTERNAL_CHECK(
+      absl::synchronization_internal::GetOrCreateCurrentThreadIdentity() !=
+          nullptr,
+      "GetOrCreateCurrentThreadIdentity() failed");
+
+  static auto* spinlock = new absl::base_internal::SpinLock(scheduling_mode);
+  for (auto _ : state) {
+    absl::base_internal::SpinLockHolder holder(spinlock);
+  }
+}
+
+BENCHMARK_TEMPLATE(BM_SpinLock,
+                   absl::base_internal::SCHEDULE_KERNEL_ONLY)
+    ->UseRealTime()
+    ->Threads(1)
+    ->ThreadPerCpu();
+
+BENCHMARK_TEMPLATE(BM_SpinLock,
+                   absl::base_internal::SCHEDULE_COOPERATIVE_AND_KERNEL)
+    ->UseRealTime()
+    ->Threads(1)
+    ->ThreadPerCpu();
+
+}  // namespace
diff --git a/absl/container/CMakeLists.txt b/absl/container/CMakeLists.txt
index 7cddd84b..8605facc 100644
--- a/absl/container/CMakeLists.txt
+++ b/absl/container/CMakeLists.txt
@@ -30,7 +30,7 @@ absl_cc_library(
 absl_cc_library(
   NAME
     compressed_tuple
-  SRCS
+  HDRS
    "internal/compressed_tuple.h"
   DEPS
     absl::utility
diff --git a/absl/container/flat_hash_set.h b/absl/container/flat_hash_set.h
index 5ea6a816..84984cc4 100644
--- a/absl/container/flat_hash_set.h
+++ b/absl/container/flat_hash_set.h
@@ -279,8 +279,7 @@ class flat_hash_set
   //
   // The element may be constructed even if there already is an element with the
   // key in the container, in which case the newly constructed element will be
-  // destroyed immediately. Prefer `try_emplace()` unless your key is not
-  // copyable or moveable.
+  // destroyed immediately.
   //
   // If rehashing occurs due to the insertion, all iterators are invalidated.
   using Base::emplace;
@@ -294,8 +293,7 @@ class flat_hash_set
   //
   // The element may be constructed even if there already is an element with the
   // key in the container, in which case the newly constructed element will be
-  // destroyed immediately. Prefer `try_emplace()` unless your key is not
-  // copyable or moveable.
+  // destroyed immediately.
   //
   // If rehashing occurs due to the insertion, all iterators are invalidated.
   using Base::emplace_hint;
diff --git a/absl/container/inlined_vector.h b/absl/container/inlined_vector.h
index 642dae6c..5f3f0095 100644
--- a/absl/container/inlined_vector.h
+++ b/absl/container/inlined_vector.h
@@ -66,12 +66,11 @@ namespace absl {
 // designed to cover the same API footprint as covered by `std::vector`.
 template <typename T, size_t N, typename A = std::allocator<T>>
 class InlinedVector {
+  static_assert(N > 0, "InlinedVector requires inline capacity greater than 0");
   constexpr static typename A::size_type inlined_capacity() {
     return static_cast<typename A::size_type>(N);
   }
 
-  static_assert(inlined_capacity() > 0, "InlinedVector needs inlined capacity");
-
   template <typename Iterator>
   using DisableIfIntegral =
       absl::enable_if_t<!std::is_integral<Iterator>::value>;
@@ -131,7 +130,8 @@ class InlinedVector {
   InlinedVector(std::initializer_list<value_type> init_list,
                 const allocator_type& alloc = allocator_type())
       : allocator_and_tag_(alloc) {
-    AppendRange(init_list.begin(), init_list.end());
+    AppendRange(init_list.begin(), init_list.end(),
+                IteratorCategory<decltype(init_list.begin())>{});
   }
 
   // Creates an inlined vector with elements constructed from the provided
@@ -144,7 +144,7 @@ class InlinedVector {
   InlinedVector(InputIterator first, InputIterator last,
                 const allocator_type& alloc = allocator_type())
       : allocator_and_tag_(alloc) {
-    AppendRange(first, last);
+    AppendRange(first, last, IteratorCategory<InputIterator>{});
   }
 
   // Creates a copy of `other` using `other`'s allocator.
@@ -366,7 +366,6 @@ class InlinedVector {
   // Returns a copy of the allocator of the inlined vector.
   allocator_type get_allocator() const { return allocator(); }
 
-
   // ---------------------------------------------------------------------------
   // InlinedVector Member Mutators
   // ---------------------------------------------------------------------------
@@ -376,7 +375,8 @@ class InlinedVector {
   // Replaces the contents of the inlined vector with copies of the elements in
   // the provided `std::initializer_list`.
   InlinedVector& operator=(std::initializer_list<value_type> init_list) {
-    AssignRange(init_list.begin(), init_list.end());
+    AssignRange(init_list.begin(), init_list.end(),
+                IteratorCategory<decltype(init_list.begin())>{});
     return *this;
   }
 
@@ -453,14 +453,15 @@ class InlinedVector {
   // inlined vector with copies of the values in the provided
   // `std::initializer_list`.
   void assign(std::initializer_list<value_type> init_list) {
-    AssignRange(init_list.begin(), init_list.end());
+    AssignRange(init_list.begin(), init_list.end(),
+                IteratorCategory<decltype(init_list.begin())>{});
   }
 
   // Overload of `InlinedVector::assign()` to replace the contents of the
   // inlined vector with values constructed from the range [`first`, `last`).
   template <typename InputIterator, DisableIfIntegral<InputIterator>* = nullptr>
   void assign(InputIterator first, InputIterator last) {
-    AssignRange(first, last);
+    AssignRange(first, last, IteratorCategory<InputIterator>{});
   }
 
   // `InlinedVector::resize()`
@@ -845,40 +846,28 @@ class InlinedVector {
   void Destroy(pointer from, pointer to);
 
   template <typename Iterator>
-  void AppendRange(Iterator first, Iterator last, std::input_iterator_tag) {
-    std::copy(first, last, std::back_inserter(*this));
-  }
-
-  template <typename Iterator>
   void AppendRange(Iterator first, Iterator last, std::forward_iterator_tag);
 
   template <typename Iterator>
-  void AppendRange(Iterator first, Iterator last) {
-    AppendRange(first, last, IteratorCategory<Iterator>());
-  }
-
-  template <typename Iterator>
-  void AssignRange(Iterator first, Iterator last, std::input_iterator_tag);
+  void AppendRange(Iterator first, Iterator last, std::input_iterator_tag);
 
   template <typename Iterator>
   void AssignRange(Iterator first, Iterator last, std::forward_iterator_tag);
 
   template <typename Iterator>
-  void AssignRange(Iterator first, Iterator last) {
-    AssignRange(first, last, IteratorCategory<Iterator>());
-  }
+  void AssignRange(Iterator first, Iterator last, std::input_iterator_tag);
 
   iterator InsertWithCount(const_iterator position, size_type n,
                            const_reference v);
 
-  template <typename InputIterator>
-  iterator InsertWithRange(const_iterator position, InputIterator first,
-                           InputIterator last, std::input_iterator_tag);
-
   template <typename ForwardIterator>
   iterator InsertWithRange(const_iterator position, ForwardIterator first,
                            ForwardIterator last, std::forward_iterator_tag);
 
+  template <typename InputIterator>
+  iterator InsertWithRange(const_iterator position, InputIterator first,
+                           InputIterator last, std::input_iterator_tag);
+
   // Stores either the inlined or allocated representation
   union Rep {
     using ValueTypeBuffer =
@@ -889,7 +878,7 @@ class InlinedVector {
     // Structs wrap the buffers to perform indirection that solves a bizarre
     // compilation error on Visual Studio (all known versions).
     struct InlinedRep {
-      ValueTypeBuffer inlined[inlined_capacity()];
+      ValueTypeBuffer inlined[N];
     };
     struct AllocatedRep {
       AllocationBuffer allocation;
@@ -1364,15 +1353,8 @@ void InlinedVector<T, N, A>::AppendRange(Iterator first, Iterator last,
 
 template <typename T, size_t N, typename A>
 template <typename Iterator>
-void InlinedVector<T, N, A>::AssignRange(Iterator first, Iterator last,
+void InlinedVector<T, N, A>::AppendRange(Iterator first, Iterator last,
                                          std::input_iterator_tag) {
-  // Optimized to avoid reallocation.
-  // Prefer reassignment to copy construction for elements.
-  iterator out = begin();
-  for (; first != last && out != end(); ++first, ++out) {
-    *out = *first;
-  }
-  erase(out, end());
   std::copy(first, last, std::back_inserter(*this));
 }
 
@@ -1399,6 +1381,20 @@ void InlinedVector<T, N, A>::AssignRange(Iterator first, Iterator last,
 }
 
 template <typename T, size_t N, typename A>
+template <typename Iterator>
+void InlinedVector<T, N, A>::AssignRange(Iterator first, Iterator last,
+                                         std::input_iterator_tag) {
+  // Optimized to avoid reallocation.
+  // Prefer reassignment to copy construction for elements.
+  iterator out = begin();
+  for (; first != last && out != end(); ++first, ++out) {
+    *out = *first;
+  }
+  erase(out, end());
+  std::copy(first, last, std::back_inserter(*this));
+}
+
+template <typename T, size_t N, typename A>
 auto InlinedVector<T, N, A>::InsertWithCount(const_iterator position,
                                              size_type n, const_reference v)
     -> iterator {
@@ -1414,20 +1410,6 @@ auto InlinedVector<T, N, A>::InsertWithCount(const_iterator position,
 }
 
 template <typename T, size_t N, typename A>
-template <typename InputIterator>
-auto InlinedVector<T, N, A>::InsertWithRange(const_iterator position,
-                                             InputIterator first,
-                                             InputIterator last,
-                                             std::input_iterator_tag)
-    -> iterator {
-  assert(position >= begin() && position <= end());
-  size_type index = position - cbegin();
-  size_type i = index;
-  while (first != last) insert(begin() + i++, *first++);
-  return begin() + index;
-}
-
-template <typename T, size_t N, typename A>
 template <typename ForwardIterator>
 auto InlinedVector<T, N, A>::InsertWithRange(const_iterator position,
                                              ForwardIterator first,
@@ -1446,6 +1428,20 @@ auto InlinedVector<T, N, A>::InsertWithRange(const_iterator position,
   return it_pair.first;
 }
 
+template <typename T, size_t N, typename A>
+template <typename InputIterator>
+auto InlinedVector<T, N, A>::InsertWithRange(const_iterator position,
+                                             InputIterator first,
+                                             InputIterator last,
+                                             std::input_iterator_tag)
+    -> iterator {
+  assert(position >= begin() && position <= end());
+  size_type index = position - cbegin();
+  size_type i = index;
+  while (first != last) insert(begin() + i++, *first++);
+  return begin() + index;
+}
+
 }  // namespace absl
 
 #endif  // ABSL_CONTAINER_INLINED_VECTOR_H_
diff --git a/absl/container/internal/layout.h b/absl/container/internal/layout.h
index a9c1244a..3d21ac96 100644
--- a/absl/container/internal/layout.h
+++ b/absl/container/internal/layout.h
@@ -253,8 +253,10 @@ template <class From, class To>
 using CopyConst =
     typename std::conditional<std::is_const<From>::value, const To, To>::type;
 
+// Note: We're not qualifying this with absl:: because it doesn't compile under
+// MSVC.
 template <class T>
-using SliceType = absl::Span<T>;
+using SliceType = Span<T>;
 
 // This namespace contains no types. It prevents functions defined in it from
 // being found by ADL.
diff --git a/absl/container/internal/raw_hash_set.cc b/absl/container/internal/raw_hash_set.cc
index 10153129..180d3fe5 100644
--- a/absl/container/internal/raw_hash_set.cc
+++ b/absl/container/internal/raw_hash_set.cc
@@ -14,6 +14,7 @@
 
 #include "absl/container/internal/raw_hash_set.h"
 
+#include <atomic>
 #include <cstddef>
 
 #include "absl/base/config.h"
@@ -29,7 +30,7 @@ inline size_t RandomSeed() {
   static thread_local size_t counter = 0;
   size_t value = ++counter;
 #else   // ABSL_HAVE_THREAD_LOCAL
-  static std::atomic<size_t> counter;
+  static std::atomic<size_t> counter(0);
   size_t value = counter.fetch_add(1, std::memory_order_relaxed);
 #endif  // ABSL_HAVE_THREAD_LOCAL
   return value ^ static_cast<size_t>(reinterpret_cast<uintptr_t>(&counter));
diff --git a/absl/container/node_hash_set.h b/absl/container/node_hash_set.h
index e4034461..843b11aa 100644
--- a/absl/container/node_hash_set.h
+++ b/absl/container/node_hash_set.h
@@ -273,8 +273,7 @@ class node_hash_set
   //
   // The element may be constructed even if there already is an element with the
   // key in the container, in which case the newly constructed element will be
-  // destroyed immediately. Prefer `try_emplace()` unless your key is not
-  // copyable or moveable.
+  // destroyed immediately.
   //
   // If rehashing occurs due to the insertion, all iterators are invalidated.
   using Base::emplace;
@@ -288,8 +287,7 @@ class node_hash_set
   //
   // The element may be constructed even if there already is an element with the
   // key in the container, in which case the newly constructed element will be
-  // destroyed immediately. Prefer `try_emplace()` unless your key is not
-  // copyable or moveable.
+  // destroyed immediately.
   //
   // If rehashing occurs due to the insertion, all iterators are invalidated.
   using Base::emplace_hint;
diff --git a/absl/debugging/CMakeLists.txt b/absl/debugging/CMakeLists.txt
index c28eb14b..f66688ba 100644
--- a/absl/debugging/CMakeLists.txt
+++ b/absl/debugging/CMakeLists.txt
@@ -14,204 +14,297 @@
 # limitations under the License.
 #
 
-list(APPEND DEBUGGING_PUBLIC_HEADERS
-  "failure_signal_handler.h"
-  "leak_check.h"
-  "stacktrace.h"
-  "symbolize.h"
-)
-
-# TODO(cohenjon) The below is all kinds of wrong.  Make this match what we do in
-# Bazel
-list(APPEND DEBUGGING_INTERNAL_HEADERS
-  "internal/address_is_readable.h"
-  "internal/demangle.h"
-  "internal/elf_mem_image.h"
-  "internal/examine_stack.h"
-  "internal/stacktrace_config.h"
-  "internal/symbolize.h"
-  "internal/vdso_support.h"
-)
-
-list(APPEND DEBUGGING_INTERNAL_SRC
-  "internal/address_is_readable.cc"
-  "internal/elf_mem_image.cc"
-  "internal/vdso_support.cc"
-)
-
-
-list(APPEND STACKTRACE_SRC
-  "stacktrace.cc"
-  ${DEBUGGING_INTERNAL_SRC}
-  ${DEBUGGING_PUBLIC_HEADERS}
-  ${DEBUGGING_INTERNAL_HEADERS}
+absl_cc_library(
+  NAME
+    stacktrace
+  HDRS
+    "stacktrace.h"
+  SRCS
+    "stacktrace.cc"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  DEPS
+    absl::debugging_internal
+    absl::base
+    absl::core_headers
+  PUBLIC
 )
 
-list(APPEND SYMBOLIZE_SRC
-  "symbolize.cc"
-  "symbolize_elf.inc"
-  "symbolize_unimplemented.inc"
-  "symbolize_win32.inc"
-  "internal/demangle.cc"
-  ${DEBUGGING_PUBLIC_HEADERS}
-  ${DEBUGGING_INTERNAL_HEADERS}
-  ${DEBUGGING_INTERNAL_SRC}
+absl_cc_library(
+  NAME
+    symbolize
+  HDRS
+    "symbolize.h"
+    "internal/symbolize.h"
+  SRCS
+    "symbolize.cc"
+    "symbolize_elf.inc"
+    "symbolize_unimplemented.inc"
+    "symbolize_win32.inc"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  DEPS
+    absl::debugging_internal
+    absl::demangle_internal
+    absl::base
+    absl::core_headers
+    absl::malloc_internal
+  PUBLIC
 )
 
-list(APPEND FAILURE_SIGNAL_HANDLER_SRC
-  "failure_signal_handler.cc"
-  ${DEBUGGING_PUBLIC_HEADERS}
+absl_cc_test(
+  NAME
+    symbolize_test
+  SRCS
+    "symbolize_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  DEPS
+    absl::stack_consumption
+    absl::symbolize
+    absl::base
+    absl::core_headers
+    absl::memory
+    gmock
 )
 
-list(APPEND EXAMINE_STACK_SRC
-  "internal/examine_stack.cc"
-  ${DEBUGGING_PUBLIC_HEADERS}
-  ${DEBUGGING_INTERNAL_HEADERS}
+absl_cc_library(
+  NAME
+    examine_stack
+  HDRS
+    "internal/examine_stack.h"
+  SRCS
+    "internal/examine_stack.cc"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  DEPS
+    absl::stacktrace
+    absl::symbolize
+    absl::base
+    absl::core_headers
 )
 
-absl_library(
-  TARGET
-    absl_stacktrace
-  SOURCES
-    ${STACKTRACE_SRC}
-  EXPORT_NAME
-    stacktrace
+absl_cc_library(
+  NAME
+    failure_signal_handler
+  HDRS
+    "failure_signal_handler.h"
+  SRCS
+    "failure_signal_handler.cc"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  DEPS
+    absl::examine_stack
+    absl::stacktrace
+    absl::base
+    absl::config
+    absl::core_headers
+  PUBLIC
 )
 
-absl_library(
-  TARGET
-    absl_symbolize
-  SOURCES
-    ${SYMBOLIZE_SRC}
-  PUBLIC_LIBRARIES
+absl_cc_test(
+  NAME
+    failure_signal_handler_test
+  SRCS
+    "failure_signal_handler_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  DEPS
+    absl::failure_signal_handler
+    absl::stacktrace
+    absl::symbolize
     absl::base
-    absl::malloc_internal
-  EXPORT_NAME
-    symbolize
+    absl::strings
+    Threads::Threads
+    gmock
 )
 
-absl_library(
-  TARGET
-    absl_failure_signal_handler
-  SOURCES
-    ${FAILURE_SIGNAL_HANDLER_SRC}
-  PUBLIC_LIBRARIES
-    absl_base absl::examine_stack absl::stacktrace absl_synchronization
-  EXPORT_NAME
-    failure_signal_handler
+absl_cc_library(
+  NAME
+    debugging_internal
+  HDRS
+    "internal/address_is_readable.h"
+    "internal/elf_mem_image.h"
+    "internal/stacktrace_aarch64-inl.inc"
+    "internal/stacktrace_arm-inl.inc"
+    "internal/stacktrace_config.h"
+    "internal/stacktrace_generic-inl.inc"
+    "internal/stacktrace_powerpc-inl.inc"
+    "internal/stacktrace_unimplemented-inl.inc"
+    "internal/stacktrace_win32-inl.inc"
+    "internal/stacktrace_x86-inl.inc"
+    "internal/vdso_support.h"
+  SRCS
+    "internal/address_is_readable.cc"
+    "internal/elf_mem_image.cc"
+    "internal/vdso_support.cc"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  DEPS
+    absl::base
+    absl::core_headers
+    absl::dynamic_annotations
 )
 
-# Internal-only. Projects external to Abseil should not depend
-# directly on this library.
-absl_library(
-  TARGET
-    absl_examine_stack
-  SOURCES
-    ${EXAMINE_STACK_SRC}
-  EXPORT_NAME
-    examine_stack
+absl_cc_library(
+  NAME
+    demangle_internal
+  HDRS
+    "internal/demangle.h"
+  SRCS
+    "internal/demangle.cc"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  DEPS
+    absl::base
+    absl::core_headers
+  PUBLIC
 )
 
-list(APPEND LEAK_CHECK_SRC
-  "leak_check.cc"
+absl_cc_test(
+  NAME
+    demangle_test
+  SRCS
+    "internal/demangle_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  DEPS
+    absl::demangle_internal
+    absl::stack_consumption
+    absl::base
+    absl::core_headers
+    absl::memory
+    gmock_main
 )
 
-
-# leak_check library
-absl_library(
-  TARGET
-    absl_leak_check
-  SOURCES
-    ${LEAK_CHECK_SRC}
-  PUBLIC_LIBRARIES
-    absl_base
-  EXPORT_NAME
+absl_cc_library(
+  NAME
     leak_check
+  HDRS
+    "$<$<NOT:$<CXX_COMPILER_ID:MSVC>>:leak_check.h>"
+  SRCS
+    "$<$<NOT:$<CXX_COMPILER_ID:MSVC>>:leak_check.cc>"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  DEPS
+    absl::core_headers
+  PUBLIC
 )
 
-
-# component target
-absl_header_library(
-  TARGET
-    absl_debugging
-  PUBLIC_LIBRARIES
-    absl_stacktrace absl_leak_check
-  EXPORT_NAME
-    debugging
+absl_cc_library(
+  NAME
+    leak_check_disable
+  SRCS
+    "leak_check_disable.cc"
+  PUBLIC
 )
 
-#
-## TESTS
-#
+# TODO(cohenjon) Move into the copts code.
+if(CMAKE_CXX_COMPILER_ID MATCHES "Clang")
+  set(ABSL_LSAN_LINKOPTS "-fsanitize=leak")
+endif()
 
-list(APPEND STACK_CONSUMPTION_SRC
-  "internal/stack_consumption.cc"
-  "internal/stack_consumption.h"
+absl_cc_library(
+  NAME
+    leak_check_api_enabled_for_testing
+  HDRS
+    "leak_check.h"
+  SRCS
+    "leak_check.cc"
+  COPTS
+    $<$<BOOL:${ABSL_USING_CLANG}>:-DLEAK_SANITIZER>
+  TESTONLY
 )
 
-absl_library(
-  TARGET
-    absl_stack_consumption
-  SOURCES
-    ${STACK_CONSUMPTION_SRC}
+absl_cc_library(
+  NAME
+    leak_check_api_disabled_for_testing
+  HDRS
+    "leak_check.h"
+  SRCS
+    "leak_check.cc"
+  COPTS
+    "-ULEAK_SANITIZER"
+  TESTONLY
 )
 
-absl_test(
-  TARGET
-    absl_stack_consumption_test
-  SOURCES
-    "internal/stack_consumption_test.cc"
-  PUBLIC_LIBRARIES
-    absl_stack_consumption
+absl_cc_test(
+  NAME
+    leak_check_test
+  SRCS
+    "leak_check_test.cc"
+  COPTS
+    "$<$<CXX_COMPILER_ID:Clang>:-DABSL_EXPECT_LEAK_SANITIZER>"
+  LINKOPTS
+    "${ABSL_LSAN_LINKOPTS}"
+  DEPS
+    absl::leak_check_api_enabled_for_testing
     absl::base
+    gmock_main
 )
 
-list(APPEND DEMANGLE_TEST_SRC "internal/demangle_test.cc")
-
-absl_test(
-  TARGET
-    demangle_test
-  SOURCES
-    ${DEMANGLE_TEST_SRC}
-  PUBLIC_LIBRARIES
-    absl_symbolize absl_stack_consumption
+absl_cc_test(
+  NAME
+    leak_check_no_lsan_test
+  SRCS
+    "leak_check_test.cc"
+  COPTS
+    "-UABSL_EXPECT_LEAK_SANITIZER"
+  DEPS
+    absl::leak_check_api_disabled_for_testing
+    absl::base
+    gmock_main
 )
 
-list(APPEND SYMBOLIZE_TEST_SRC "symbolize_test.cc")
-
-absl_test(
-  TARGET
-    symbolize_test
-  SOURCES
-    ${SYMBOLIZE_TEST_SRC}
-  PUBLIC_LIBRARIES
-    absl::base absl::memory absl_symbolize absl_stack_consumption
+absl_cc_test(
+  NAME
+    disabled_leak_check_test
+  SRCS
+    "leak_check_fail_test.cc"
+  LINKOPTS
+    "${ABSL_LSAN_LINKOPTS}"
+  DEPS
+    absl::leak_check_api_enabled_for_testing
+    absl::leak_check_disable
+    absl::base
+    gmock_main
 )
 
-list(APPEND FAILURE_SIGNAL_HANDLER_TEST_SRC "failure_signal_handler_test.cc")
-
-absl_test(
-  TARGET
-    failure_signal_handler_test
-  SOURCES
-    ${FAILURE_SIGNAL_HANDLER_TEST_SRC}
-  PUBLIC_LIBRARIES
-    absl_examine_stack
-    absl_failure_signal_handler
-    absl_stacktrace
-    absl_symbolize
+absl_cc_library(
+  NAME
+    stack_consumption
+  HDRS
+    "internal/stack_consumption.h"
+  SRCS
+    "internal/stack_consumption.cc"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  DEPS
     absl::base
-    absl::strings
+    absl::core_headers
+  TESTONLY
 )
 
-# test leak_check_test
-list(APPEND LEAK_CHECK_TEST_SRC "leak_check_test.cc")
+absl_cc_test(
+  NAME
+    stack_consumption_test
+  SRCS
+    "internal/stack_consumption_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  DEPS
+    absl::stack_consumption
+    absl::base
+    absl::core_headers
+    gmock_main
+)
 
-absl_test(
-  TARGET
-    leak_check_test
-  SOURCES
-    ${LEAK_CHECK_TEST_SRC}
-  PUBLIC_LIBRARIES
-    absl_leak_check
+# component target
+absl_cc_library(
+  NAME
+    debugging
+  DEPS
+    absl::stacktrace
+    absl::leak_check
+  PUBLIC
 )
diff --git a/absl/debugging/internal/demangle.cc b/absl/debugging/internal/demangle.cc
index 48354459..3ee3df51 100644
--- a/absl/debugging/internal/demangle.cc
+++ b/absl/debugging/internal/demangle.cc
@@ -1636,6 +1636,15 @@ static bool ParseExpression(State *state) {
   }
   state->parse_state = copy;
 
+  // Pointer-to-member access expressions.  This parses the same as a binary
+  // operator, but it's implemented separately because "ds" shouldn't be
+  // accepted in other contexts that parse an operator name.
+  if (ParseTwoCharToken(state, "ds") && ParseExpression(state) &&
+      ParseExpression(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+
   // Parameter pack expansion
   if (ParseTwoCharToken(state, "sp") && ParseExpression(state)) {
     return true;
diff --git a/absl/hash/CMakeLists.txt b/absl/hash/CMakeLists.txt
index a0d59b0b..8f97d7cc 100644
--- a/absl/hash/CMakeLists.txt
+++ b/absl/hash/CMakeLists.txt
@@ -14,40 +14,30 @@
 # limitations under the License.
 #
 
-list(APPEND HASH_PUBLIC_HEADERS
-  "hash.h"
-)
-
-list(APPEND HASH_INTERNAL_HEADERS
-  "internal/city.h"
-  "internal/hash.h"
-)
-
-# absl_hash library
-list(APPEND HASH_SRC
-  "internal/city.cc"
-  "internal/hash.cc"
-  ${HASH_PUBLIC_HEADERS}
-  ${HASH_INTERNAL_HEADERS}
-)
-
-set(HASH_PUBLIC_LIBRARIES absl::hash absl::fixed_array absl::strings absl::str_format absl::utility)
-
-absl_library(
-  TARGET
-    absl_hash
-  SOURCES
-    ${HASH_SRC}
-  PUBLIC_LIBRARIES
-    ${HASH_PUBLIC_LIBRARIES}
-  EXPORT_NAME
+absl_cc_library(
+  NAME
     hash
+  HDRS
+    "hash.h"
+  SRCS
+    "internal/hash.cc"
+    "internal/hash.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  DEPS
+    absl::core_headers
+    absl::endian
+    absl::fixed_array
+    absl::meta
+    absl::int128
+    absl::strings
+    absl::optional
+    absl::variant
+    absl::utility
+    absl::city
+  PUBLIC
 )
 
-#
-## TESTS
-#
-
 absl_cc_library(
   NAME
     hash_testing
@@ -62,11 +52,29 @@ absl_cc_library(
   TESTONLY
 )
 
+absl_cc_test(
+  NAME
+    hash_test
+  SRCS
+   "hash_test.cc"
+  DEPS
+    absl::hash
+    absl::hash_testing
+    absl::core_headers
+    absl::flat_hash_set
+    absl::spy_hash_state
+    absl::meta
+    absl::int128
+    gmock_main
+)
+
 absl_cc_library(
   NAME
     spy_hash_state
   HDRS
     "internal/spy_hash_state.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
   DEPS
     absl::hash
     absl::strings
@@ -74,32 +82,30 @@ absl_cc_library(
   TESTONLY
 )
 
-# testing support
-set(HASH_TEST_HEADERS hash_testing.h internal/spy_hash_state.h)
-set(HASH_TEST_PUBLIC_LIBRARIES absl::hash absl::flat_hash_set absl::numeric absl::strings absl::str_format)
-
-# hash_test
-set(HASH_TEST_SRC "hash_test.cc" ${HASH_TEST_HEADERS})
-
-absl_test(
-  TARGET
-    hash_test
-  SOURCES
-    ${HASH_TEST_SRC}
-  PUBLIC_LIBRARIES
-    ${HASH_TEST_PUBLIC_LIBRARIES}
+absl_cc_library(
+  NAME
+    city
+  HDRS
+    "internal/city.h"
+  SRCS
+    "internal/city.cc"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  DEPS
+    absl::config
+    absl::core_headers
+    absl::endian
 )
 
-# hash_test
-set(CITY_TEST_SRC "internal/city_test.cc")
-
-absl_test(
-  TARGET
+absl_cc_test(
+  NAME
     city_test
-  SOURCES
-    ${CITY_TEST_SRC}
-  PUBLIC_LIBRARIES
-    ${HASH_TEST_PUBLIC_LIBRARIES}
+  SRCS
+    "internal/city_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  DEPS
+    absl::city
+    gmock_main
 )
 
-
diff --git a/absl/memory/CMakeLists.txt b/absl/memory/CMakeLists.txt
index 8f9e731f..4b494dc0 100644
--- a/absl/memory/CMakeLists.txt
+++ b/absl/memory/CMakeLists.txt
@@ -14,55 +14,45 @@
 # limitations under the License.
 #
 
-list(APPEND MEMORY_PUBLIC_HEADERS
-  "memory.h"
-)
-
-
-absl_header_library(
-  TARGET
-    absl_memory
-  EXPORT_NAME
+absl_cc_library(
+  NAME
     memory
+  HDRS
+    "memory.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  DEPS
+    absl::core_headers
+    absl::meta
+  PUBLIC
 )
 
-#
-## TESTS
-#
-
-# test memory_test
-list(APPEND MEMORY_TEST_SRC
-  "memory_test.cc"
-  ${MEMORY_PUBLIC_HEADERS}
-)
-set(MEMORY_TEST_PUBLIC_LIBRARIES absl::base absl::memory)
-
-
-
-absl_test(
-  TARGET
+absl_cc_test(
+  NAME
     memory_test
-  SOURCES
-    ${MEMORY_TEST_SRC}
-  PUBLIC_LIBRARIES
-    ${MEMORY_TEST_PUBLIC_LIBRARIES}
-)
-
-
-# test memory_exception_safety_test
-set(MEMORY_EXCEPTION_SAFETY_TEST_SRC "memory_exception_safety_test.cc")
-set(MEMORY_EXCEPTION_SAFETY_TEST_PUBLIC_LIBRARIES
-  absl::memory
-  absl_internal_exception_safety_testing
+  SRCS
+    "memory_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  DEPS
+    absl::memory
+    absl::base
+    absl::core_headers
+    gmock_main
 )
 
-absl_test(
-  TARGET
+absl_cc_test(
+  NAME
     memory_exception_safety_test
-  SOURCES
-    ${MEMORY_EXCEPTION_SAFETY_TEST_SRC}
-  PUBLIC_LIBRARIES
-    ${MEMORY_EXCEPTION_SAFETY_TEST_PUBLIC_LIBRARIES}
-  PRIVATE_COMPILE_FLAGS
+  SRCS
+    "memory_exception_safety_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
     ${ABSL_EXCEPTIONS_FLAG}
+  LINKOPTS
+    ${ABSL_EXCEPTIONS_FLAG_LINKOPTS}
+  DEPS
+    absl::memory
+    absl::exception_safety_testing
+    gmock_main
 )
diff --git a/absl/memory/memory_test.cc b/absl/memory/memory_test.cc
index 54f920b5..21fe32f9 100644
--- a/absl/memory/memory_test.cc
+++ b/absl/memory/memory_test.cc
@@ -69,6 +69,45 @@ TEST(MakeUniqueTest, Basic) {
   EXPECT_EQ("hi", *p);
 }
 
+// InitializationVerifier fills in a pattern when allocated so we can
+// distinguish between its default and value initialized states (without
+// accessing truly uninitialized memory).
+struct InitializationVerifier {
+  static constexpr int kDefaultScalar = 0x43;
+  static constexpr int kDefaultArray = 0x4B;
+
+  static void* operator new(size_t n) {
+    void* ret = ::operator new(n);
+    memset(ret, kDefaultScalar, n);
+    return ret;
+  }
+
+  static void* operator new[](size_t n) {
+    void* ret = ::operator new[](n);
+    memset(ret, kDefaultArray, n);
+    return ret;
+  }
+
+  int a;
+  int b;
+};
+
+TEST(Initialization, MakeUnique) {
+  auto p = absl::make_unique<InitializationVerifier>();
+
+  EXPECT_EQ(0, p->a);
+  EXPECT_EQ(0, p->b);
+}
+
+TEST(Initialization, MakeUniqueArray) {
+  auto p = absl::make_unique<InitializationVerifier[]>(2);
+
+  EXPECT_EQ(0, p[0].a);
+  EXPECT_EQ(0, p[0].b);
+  EXPECT_EQ(0, p[1].a);
+  EXPECT_EQ(0, p[1].b);
+}
+
 struct MoveOnly {
   MoveOnly() = default;
   explicit MoveOnly(int i1) : ip1{new int{i1}} {}
diff --git a/absl/strings/BUILD.bazel b/absl/strings/BUILD.bazel
index 6d7c2619..3b85f1b4 100644
--- a/absl/strings/BUILD.bazel
+++ b/absl/strings/BUILD.bazel
@@ -413,6 +413,7 @@ cc_test(
     copts = ABSL_TEST_COPTS,
     visibility = ["//visibility:private"],
     deps = [
+        ":pow10_helper",
         ":strings",
         "//absl/base",
         "//absl/base:core_headers",
@@ -471,6 +472,8 @@ cc_test(
     srcs = ["charconv_test.cc"],
     copts = ABSL_TEST_COPTS,
     deps = [
+        ":pow10_helper",
+        ":str_format",
         ":strings",
         "//absl/base",
         "@com_google_googletest//:gtest_main",
@@ -659,3 +662,23 @@ cc_test(
         "@com_google_googletest//:gtest_main",
     ],
 )
+
+cc_library(
+    name = "pow10_helper",
+    testonly = True,
+    srcs = ["internal/pow10_helper.cc"],
+    hdrs = ["internal/pow10_helper.h"],
+    visibility = ["//visibility:private"],
+)
+
+cc_test(
+    name = "pow10_helper_test",
+    srcs = ["internal/pow10_helper_test.cc"],
+    copts = ABSL_TEST_COPTS,
+    visibility = ["//visibility:private"],
+    deps = [
+        ":pow10_helper",
+        ":str_format",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
diff --git a/absl/strings/CMakeLists.txt b/absl/strings/CMakeLists.txt
index a6574c17..5b877ad1 100644
--- a/absl/strings/CMakeLists.txt
+++ b/absl/strings/CMakeLists.txt
@@ -131,6 +131,15 @@ absl_library(
     absl::strings
 )
 
+# pow10_helper
+absl_library(
+  TARGET
+    pow10_helper
+  SOURCES
+    "internal/pow10_helper.cc"
+    "internal/pow10_helper.h"
+)
+
 #
 ## TESTS
 #
@@ -316,7 +325,7 @@ absl_test(
 
 # test numbers_test
 set(NUMBERS_TEST_SRC "numbers_test.cc")
-set(NUMBERS_TEST_PUBLIC_LIBRARIES absl::strings)
+set(NUMBERS_TEST_PUBLIC_LIBRARIES absl::strings pow10_helper)
 
 absl_test(
   TARGET
@@ -358,7 +367,7 @@ absl_test(
 
 # test charconv_test
 set(CHARCONV_TEST_SRC "charconv_test.cc")
-set(CHARCONV_TEST_PUBLIC_LIBRARIES absl::strings)
+set(CHARCONV_TEST_PUBLIC_LIBRARIES absl::strings absl::str_format pow10_helper)
 
 absl_test(
   TARGET
@@ -460,3 +469,13 @@ absl_test(
     absl::base
 )
 
+# test pow10_helper_test
+absl_test(
+  TARGET
+    pow10_helper_test
+  SOURCES
+    "internal/pow10_helper_test.cc"
+  PUBLIC_LIBRARIES
+    pow10_helper
+    absl::str_format
+)
diff --git a/absl/strings/charconv_test.cc b/absl/strings/charconv_test.cc
index 89418fe9..d07537eb 100644
--- a/absl/strings/charconv_test.cc
+++ b/absl/strings/charconv_test.cc
@@ -19,7 +19,9 @@
 
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
+#include "absl/strings/internal/pow10_helper.h"
 #include "absl/strings/str_cat.h"
+#include "absl/strings/str_format.h"
 
 #ifdef _MSC_FULL_VER
 #define ABSL_COMPILER_DOES_EXACT_ROUNDING 0
@@ -31,6 +33,8 @@
 
 namespace {
 
+using absl::strings_internal::Pow10;
+
 #if ABSL_COMPILER_DOES_EXACT_ROUNDING
 
 // Tests that the given string is accepted by absl::from_chars, and that it
@@ -678,7 +682,8 @@ void TestOverflowAndUnderflow(
     auto result =
         absl::from_chars(input.data(), input.data() + input.size(), actual);
     EXPECT_EQ(result.ec, std::errc());
-    EXPECT_EQ(expected, actual);
+    EXPECT_EQ(expected, actual)
+        << absl::StrFormat("%a vs %a", expected, actual);
   }
   // test legal values near upper_bound
   for (index = upper_bound, step = 1; index > lower_bound;
@@ -690,7 +695,8 @@ void TestOverflowAndUnderflow(
     auto result =
         absl::from_chars(input.data(), input.data() + input.size(), actual);
     EXPECT_EQ(result.ec, std::errc());
-    EXPECT_EQ(expected, actual);
+    EXPECT_EQ(expected, actual)
+        << absl::StrFormat("%a vs %a", expected, actual);
   }
   // Test underflow values below lower_bound
   for (index = lower_bound - 1, step = 1; index > -1000000;
@@ -747,7 +753,7 @@ TEST(FromChars, HexdecimalFloatLimits) {
 // acceptable exponents in this test.
 TEST(FromChars, DecimalDoubleLimits) {
   auto input_gen = [](int index) { return absl::StrCat("1.0e", index); };
-  auto expected_gen = [](int index) { return std::pow(10.0, index); };
+  auto expected_gen = [](int index) { return Pow10(index); };
   TestOverflowAndUnderflow<double>(input_gen, expected_gen, -323, 308);
 }
 
@@ -759,7 +765,7 @@ TEST(FromChars, DecimalDoubleLimits) {
 // acceptable exponents in this test.
 TEST(FromChars, DecimalFloatLimits) {
   auto input_gen = [](int index) { return absl::StrCat("1.0e", index); };
-  auto expected_gen = [](int index) { return std::pow(10.0, index); };
+  auto expected_gen = [](int index) { return Pow10(index); };
   TestOverflowAndUnderflow<float>(input_gen, expected_gen, -45, 38);
 }
 
diff --git a/absl/strings/internal/pow10_helper.cc b/absl/strings/internal/pow10_helper.cc
new file mode 100644
index 00000000..66be163f
--- /dev/null
+++ b/absl/strings/internal/pow10_helper.cc
@@ -0,0 +1,120 @@
+// 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
+//
+//      http://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/strings/internal/pow10_helper.h"
+
+#include <cmath>
+
+namespace absl {
+namespace strings_internal {
+
+namespace {
+
+// The exact value of 1e23 falls precisely halfway between two representable
+// doubles. Furthermore, the rounding rules we prefer (break ties by rounding
+// to the nearest even) dictate in this case that the number should be rounded
+// down, but this is not completely specified for floating-point literals in
+// C++. (It just says to use the default rounding mode of the standard
+// library.) We ensure the result we want by using a number that has an
+// unambiguous correctly rounded answer.
+constexpr double k1e23 = 9999999999999999e7;
+
+constexpr double kPowersOfTen[] = {
+    0.0,    1e-323, 1e-322, 1e-321, 1e-320, 1e-319, 1e-318, 1e-317, 1e-316,
+    1e-315, 1e-314, 1e-313, 1e-312, 1e-311, 1e-310, 1e-309, 1e-308, 1e-307,
+    1e-306, 1e-305, 1e-304, 1e-303, 1e-302, 1e-301, 1e-300, 1e-299, 1e-298,
+    1e-297, 1e-296, 1e-295, 1e-294, 1e-293, 1e-292, 1e-291, 1e-290, 1e-289,
+    1e-288, 1e-287, 1e-286, 1e-285, 1e-284, 1e-283, 1e-282, 1e-281, 1e-280,
+    1e-279, 1e-278, 1e-277, 1e-276, 1e-275, 1e-274, 1e-273, 1e-272, 1e-271,
+    1e-270, 1e-269, 1e-268, 1e-267, 1e-266, 1e-265, 1e-264, 1e-263, 1e-262,
+    1e-261, 1e-260, 1e-259, 1e-258, 1e-257, 1e-256, 1e-255, 1e-254, 1e-253,
+    1e-252, 1e-251, 1e-250, 1e-249, 1e-248, 1e-247, 1e-246, 1e-245, 1e-244,
+    1e-243, 1e-242, 1e-241, 1e-240, 1e-239, 1e-238, 1e-237, 1e-236, 1e-235,
+    1e-234, 1e-233, 1e-232, 1e-231, 1e-230, 1e-229, 1e-228, 1e-227, 1e-226,
+    1e-225, 1e-224, 1e-223, 1e-222, 1e-221, 1e-220, 1e-219, 1e-218, 1e-217,
+    1e-216, 1e-215, 1e-214, 1e-213, 1e-212, 1e-211, 1e-210, 1e-209, 1e-208,
+    1e-207, 1e-206, 1e-205, 1e-204, 1e-203, 1e-202, 1e-201, 1e-200, 1e-199,
+    1e-198, 1e-197, 1e-196, 1e-195, 1e-194, 1e-193, 1e-192, 1e-191, 1e-190,
+    1e-189, 1e-188, 1e-187, 1e-186, 1e-185, 1e-184, 1e-183, 1e-182, 1e-181,
+    1e-180, 1e-179, 1e-178, 1e-177, 1e-176, 1e-175, 1e-174, 1e-173, 1e-172,
+    1e-171, 1e-170, 1e-169, 1e-168, 1e-167, 1e-166, 1e-165, 1e-164, 1e-163,
+    1e-162, 1e-161, 1e-160, 1e-159, 1e-158, 1e-157, 1e-156, 1e-155, 1e-154,
+    1e-153, 1e-152, 1e-151, 1e-150, 1e-149, 1e-148, 1e-147, 1e-146, 1e-145,
+    1e-144, 1e-143, 1e-142, 1e-141, 1e-140, 1e-139, 1e-138, 1e-137, 1e-136,
+    1e-135, 1e-134, 1e-133, 1e-132, 1e-131, 1e-130, 1e-129, 1e-128, 1e-127,
+    1e-126, 1e-125, 1e-124, 1e-123, 1e-122, 1e-121, 1e-120, 1e-119, 1e-118,
+    1e-117, 1e-116, 1e-115, 1e-114, 1e-113, 1e-112, 1e-111, 1e-110, 1e-109,
+    1e-108, 1e-107, 1e-106, 1e-105, 1e-104, 1e-103, 1e-102, 1e-101, 1e-100,
+    1e-99,  1e-98,  1e-97,  1e-96,  1e-95,  1e-94,  1e-93,  1e-92,  1e-91,
+    1e-90,  1e-89,  1e-88,  1e-87,  1e-86,  1e-85,  1e-84,  1e-83,  1e-82,
+    1e-81,  1e-80,  1e-79,  1e-78,  1e-77,  1e-76,  1e-75,  1e-74,  1e-73,
+    1e-72,  1e-71,  1e-70,  1e-69,  1e-68,  1e-67,  1e-66,  1e-65,  1e-64,
+    1e-63,  1e-62,  1e-61,  1e-60,  1e-59,  1e-58,  1e-57,  1e-56,  1e-55,
+    1e-54,  1e-53,  1e-52,  1e-51,  1e-50,  1e-49,  1e-48,  1e-47,  1e-46,
+    1e-45,  1e-44,  1e-43,  1e-42,  1e-41,  1e-40,  1e-39,  1e-38,  1e-37,
+    1e-36,  1e-35,  1e-34,  1e-33,  1e-32,  1e-31,  1e-30,  1e-29,  1e-28,
+    1e-27,  1e-26,  1e-25,  1e-24,  1e-23,  1e-22,  1e-21,  1e-20,  1e-19,
+    1e-18,  1e-17,  1e-16,  1e-15,  1e-14,  1e-13,  1e-12,  1e-11,  1e-10,
+    1e-9,   1e-8,   1e-7,   1e-6,   1e-5,   1e-4,   1e-3,   1e-2,   1e-1,
+    1e+0,   1e+1,   1e+2,   1e+3,   1e+4,   1e+5,   1e+6,   1e+7,   1e+8,
+    1e+9,   1e+10,  1e+11,  1e+12,  1e+13,  1e+14,  1e+15,  1e+16,  1e+17,
+    1e+18,  1e+19,  1e+20,  1e+21,  1e+22,  k1e23,  1e+24,  1e+25,  1e+26,
+    1e+27,  1e+28,  1e+29,  1e+30,  1e+31,  1e+32,  1e+33,  1e+34,  1e+35,
+    1e+36,  1e+37,  1e+38,  1e+39,  1e+40,  1e+41,  1e+42,  1e+43,  1e+44,
+    1e+45,  1e+46,  1e+47,  1e+48,  1e+49,  1e+50,  1e+51,  1e+52,  1e+53,
+    1e+54,  1e+55,  1e+56,  1e+57,  1e+58,  1e+59,  1e+60,  1e+61,  1e+62,
+    1e+63,  1e+64,  1e+65,  1e+66,  1e+67,  1e+68,  1e+69,  1e+70,  1e+71,
+    1e+72,  1e+73,  1e+74,  1e+75,  1e+76,  1e+77,  1e+78,  1e+79,  1e+80,
+    1e+81,  1e+82,  1e+83,  1e+84,  1e+85,  1e+86,  1e+87,  1e+88,  1e+89,
+    1e+90,  1e+91,  1e+92,  1e+93,  1e+94,  1e+95,  1e+96,  1e+97,  1e+98,
+    1e+99,  1e+100, 1e+101, 1e+102, 1e+103, 1e+104, 1e+105, 1e+106, 1e+107,
+    1e+108, 1e+109, 1e+110, 1e+111, 1e+112, 1e+113, 1e+114, 1e+115, 1e+116,
+    1e+117, 1e+118, 1e+119, 1e+120, 1e+121, 1e+122, 1e+123, 1e+124, 1e+125,
+    1e+126, 1e+127, 1e+128, 1e+129, 1e+130, 1e+131, 1e+132, 1e+133, 1e+134,
+    1e+135, 1e+136, 1e+137, 1e+138, 1e+139, 1e+140, 1e+141, 1e+142, 1e+143,
+    1e+144, 1e+145, 1e+146, 1e+147, 1e+148, 1e+149, 1e+150, 1e+151, 1e+152,
+    1e+153, 1e+154, 1e+155, 1e+156, 1e+157, 1e+158, 1e+159, 1e+160, 1e+161,
+    1e+162, 1e+163, 1e+164, 1e+165, 1e+166, 1e+167, 1e+168, 1e+169, 1e+170,
+    1e+171, 1e+172, 1e+173, 1e+174, 1e+175, 1e+176, 1e+177, 1e+178, 1e+179,
+    1e+180, 1e+181, 1e+182, 1e+183, 1e+184, 1e+185, 1e+186, 1e+187, 1e+188,
+    1e+189, 1e+190, 1e+191, 1e+192, 1e+193, 1e+194, 1e+195, 1e+196, 1e+197,
+    1e+198, 1e+199, 1e+200, 1e+201, 1e+202, 1e+203, 1e+204, 1e+205, 1e+206,
+    1e+207, 1e+208, 1e+209, 1e+210, 1e+211, 1e+212, 1e+213, 1e+214, 1e+215,
+    1e+216, 1e+217, 1e+218, 1e+219, 1e+220, 1e+221, 1e+222, 1e+223, 1e+224,
+    1e+225, 1e+226, 1e+227, 1e+228, 1e+229, 1e+230, 1e+231, 1e+232, 1e+233,
+    1e+234, 1e+235, 1e+236, 1e+237, 1e+238, 1e+239, 1e+240, 1e+241, 1e+242,
+    1e+243, 1e+244, 1e+245, 1e+246, 1e+247, 1e+248, 1e+249, 1e+250, 1e+251,
+    1e+252, 1e+253, 1e+254, 1e+255, 1e+256, 1e+257, 1e+258, 1e+259, 1e+260,
+    1e+261, 1e+262, 1e+263, 1e+264, 1e+265, 1e+266, 1e+267, 1e+268, 1e+269,
+    1e+270, 1e+271, 1e+272, 1e+273, 1e+274, 1e+275, 1e+276, 1e+277, 1e+278,
+    1e+279, 1e+280, 1e+281, 1e+282, 1e+283, 1e+284, 1e+285, 1e+286, 1e+287,
+    1e+288, 1e+289, 1e+290, 1e+291, 1e+292, 1e+293, 1e+294, 1e+295, 1e+296,
+    1e+297, 1e+298, 1e+299, 1e+300, 1e+301, 1e+302, 1e+303, 1e+304, 1e+305,
+    1e+306, 1e+307, 1e+308,
+};
+
+}  // namespace
+
+double Pow10(int exp) {
+  if (exp < -324) {
+    return 0.0;
+  } else if (exp > 308) {
+    return INFINITY;
+  } else {
+    return kPowersOfTen[exp + 324];
+  }
+}
+
+}  // namespace strings_internal
+}  // namespace absl
diff --git a/absl/strings/internal/pow10_helper.h b/absl/strings/internal/pow10_helper.h
new file mode 100644
index 00000000..39c15392
--- /dev/null
+++ b/absl/strings/internal/pow10_helper.h
@@ -0,0 +1,36 @@
+//
+// 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
+//
+//      http://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 test helper library contains a table of powers of 10, to guarantee
+// precise values are computed across the full range of doubles. We can't rely
+// on the pow() function, because not all standard libraries ship a version
+// that is precise.
+#ifndef ABSL_STRINGS_POW10_HELPER_H_
+#define ABSL_STRINGS_POW10_HELPER_H_
+
+#include <vector>
+
+namespace absl {
+namespace strings_internal {
+
+// Computes the precise value of 10^exp. (I.e. the nearest representable
+// double to the exact value, rounding to nearest-even in the (single) case of
+// being exactly halfway between.)
+double Pow10(int exp);
+
+}  // namespace strings_internal
+}  // namespace absl
+
+#endif  // ABSL_STRINGS_POW10_HELPER_H_
diff --git a/absl/strings/internal/pow10_helper_test.cc b/absl/strings/internal/pow10_helper_test.cc
new file mode 100644
index 00000000..9a13d524
--- /dev/null
+++ b/absl/strings/internal/pow10_helper_test.cc
@@ -0,0 +1,120 @@
+// 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
+//
+//      http://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/strings/internal/pow10_helper.h"
+
+#include <cmath>
+
+#include "gtest/gtest.h"
+#include "absl/strings/str_format.h"
+
+namespace absl {
+namespace strings_internal {
+
+namespace {
+
+struct TestCase {
+  int power;           // Testing Pow10(power)
+  uint64_t significand;  // Raw bits of the expected value
+  int radix;           // significand is adjusted by 2^radix
+};
+
+TEST(Pow10HelperTest, Works) {
+  // The logic in pow10_helper.cc is so simple that theoretically we don't even
+  // need a test. However, we're paranoid and believe that there may be
+  // compilers that don't round floating-point literals correctly, even though
+  // it is specified by the standard. We check various edge cases, just to be
+  // sure.
+  constexpr TestCase kTestCases[] = {
+      // Subnormals
+      {-323, 0x2, -1074},
+      {-322, 0x14, -1074},
+      {-321, 0xca, -1074},
+      {-320, 0x7e8, -1074},
+      {-319, 0x4f10, -1074},
+      {-318, 0x316a2, -1074},
+      {-317, 0x1ee257, -1074},
+      {-316, 0x134d761, -1074},
+      {-315, 0xc1069cd, -1074},
+      {-314, 0x78a42205, -1074},
+      {-313, 0x4b6695433, -1074},
+      {-312, 0x2f201d49fb, -1074},
+      {-311, 0x1d74124e3d1, -1074},
+      {-310, 0x12688b70e62b, -1074},
+      {-309, 0xb8157268fdaf, -1074},
+      {-308, 0x730d67819e8d2, -1074},
+      // Values that are very close to rounding the other way.
+      // Comment shows difference of significand from the true value.
+      {-307, 0x11fa182c40c60d, -1072},  // -.4588
+      {-290, 0x18f2b061aea072, -1016},  //  .4854
+      {-276, 0x11BA03F5B21000, -969},   //  .4709
+      {-259, 0x1899C2F6732210, -913},   //  .4830
+      {-252, 0x1D53844EE47DD1, -890},   // -.4743
+      {-227, 0x1E5297287C2F45, -807},   // -.4708
+      {-198, 0x1322E220A5B17E, -710},   // -.4714
+      {-195, 0x12B010D3E1CF56, -700},   //  .4928
+      {-192, 0x123FF06EEA847A, -690},   //  .4968
+      {-163, 0x1708D0F84D3DE7, -594},   // -.4977
+      {-145, 0x13FAAC3E3FA1F3, -534},   // -.4785
+      {-111, 0x133D4032C2C7F5, -421},   //  .4774
+      {-106, 0x1D5B561574765B, -405},   // -.4869
+      {-104, 0x16EF5B40C2FC77, -398},   // -.4741
+      {-88, 0x197683DF2F268D, -345},    // -.4738
+      {-86, 0x13E497065CD61F, -338},    //  .4736
+      {-76, 0x17288E1271F513, -305},    // -.4761
+      {-63, 0x1A53FC9631D10D, -262},    //  .4929
+      {-30, 0x14484BFEEBC2A0, -152},    //  .4758
+      {-21, 0x12E3B40A0E9B4F, -122},    // -.4916
+      {-5, 0x14F8B588E368F1, -69},      //  .4829
+      {23, 0x152D02C7E14AF6, 24},       // -.5000 (exactly, round-to-even)
+      {29, 0x1431E0FAE6D721, 44},       // -.4870
+      {34, 0x1ED09BEAD87C03, 60},       // -.4721
+      {70, 0x172EBAD6DDC73D, 180},      //  .4733
+      {105, 0x1BE7ABD3781ECA, 296},     // -.4850
+      {126, 0x17A2ECC414A03F, 366},     // -.4999
+      {130, 0x1CDA62055B2D9E, 379},     //  .4855
+      {165, 0x115D847AD00087, 496},     // -.4913
+      {172, 0x14B378469B6732, 519},     //  .4818
+      {187, 0x1262DFEEBBB0F9, 569},     // -.4805
+      {210, 0x18557F31326BBB, 645},     // -.4992
+      {212, 0x1302CB5E6F642A, 652},     // -.4838
+      {215, 0x1290BA9A38C7D1, 662},     // -.4881
+      {236, 0x1F736F9B3494E9, 731},     //  .4707
+      {244, 0x176EC98994F489, 758},     //  .4924
+      {250, 0x1658E3AB795204, 778},     // -.4963
+      {252, 0x117571DDF6C814, 785},     //  .4873
+      {254, 0x1B4781EAD1989E, 791},     // -.4887
+      {260, 0x1A03FDE214CAF1, 811},     //  .4784
+      {284, 0x1585041B2C477F, 891},     //  .4798
+      {304, 0x1D2A1BE4048F90, 957},     // -.4987
+      // Out-of-range values
+      {-324, 0x0, 0},
+      {-325, 0x0, 0},
+      {-326, 0x0, 0},
+      {309, 1, 2000},
+      {310, 1, 2000},
+      {311, 1, 2000},
+  };
+  for (const TestCase& test_case : kTestCases) {
+    EXPECT_EQ(Pow10(test_case.power),
+              std::ldexp(test_case.significand, test_case.radix))
+        << absl::StrFormat("Failure for Pow10(%d): %a vs %a", test_case.power,
+                           Pow10(test_case.power),
+                           std::ldexp(test_case.significand, test_case.radix));
+  }
+}
+
+}  // namespace
+}  // namespace strings_internal
+}  // namespace absl
diff --git a/absl/strings/numbers_test.cc b/absl/strings/numbers_test.cc
index 36fc0d64..099326c2 100644
--- a/absl/strings/numbers_test.cc
+++ b/absl/strings/numbers_test.cc
@@ -39,6 +39,7 @@
 #include "absl/strings/str_cat.h"
 
 #include "absl/strings/internal/numbers_test_common.h"
+#include "absl/strings/internal/pow10_helper.h"
 
 namespace {
 
@@ -871,7 +872,7 @@ TEST_F(SimpleDtoaTest, ExhaustiveDoubleToSixDigits) {
     }
 
     for (int exponent = -324; exponent <= 308; ++exponent) {
-      double powten = pow(10.0, exponent);
+      double powten = absl::strings_internal::Pow10(exponent);
       if (powten == 0) powten = 5e-324;
       if (kFloatNumCases >= 1e9) {
         // The exhaustive test takes a very long time, so log progress.
diff --git a/absl/synchronization/BUILD.bazel b/absl/synchronization/BUILD.bazel
index f52e9d41..e63b1d16 100644
--- a/absl/synchronization/BUILD.bazel
+++ b/absl/synchronization/BUILD.bazel
@@ -170,18 +170,32 @@ cc_test(
     ],
 )
 
-cc_test(
-    name = "mutex_benchmark",
+cc_library(
+    name = "mutex_benchmark_common",
+    testonly = 1,
     srcs = ["mutex_benchmark.cc"],
-    copts = ABSL_TEST_COPTS,
-    tags = ["benchmark"],
-    visibility = ["//visibility:private"],
+    copts = ABSL_DEFAULT_COPTS,
+    visibility = [
+        "//absl/synchronization:__pkg__",
+    ],
     deps = [
         ":synchronization",
         ":thread_pool",
         "//absl/base",
+        "//absl/base:base_internal",
         "@com_github_google_benchmark//:benchmark_main",
     ],
+    alwayslink = 1,
+)
+
+cc_binary(
+    name = "mutex_benchmark",
+    testonly = 1,
+    copts = ABSL_DEFAULT_COPTS,
+    visibility = ["//visibility:private"],
+    deps = [
+        ":mutex_benchmark_common",
+    ],
 )
 
 cc_test(
diff --git a/absl/synchronization/mutex_benchmark.cc b/absl/synchronization/mutex_benchmark.cc
index 1e019e00..2652bb97 100644
--- a/absl/synchronization/mutex_benchmark.cc
+++ b/absl/synchronization/mutex_benchmark.cc
@@ -12,16 +12,154 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+#include <cstdint>
+#include <mutex>  // NOLINT(build/c++11)
 #include <vector>
 
-#include "benchmark/benchmark.h"
-#include "absl/base/internal/sysinfo.h"
+#include "absl/base/internal/cycleclock.h"
+#include "absl/base/internal/spinlock.h"
 #include "absl/synchronization/blocking_counter.h"
 #include "absl/synchronization/internal/thread_pool.h"
 #include "absl/synchronization/mutex.h"
+#include "benchmark/benchmark.h"
 
 namespace {
 
+void BM_Mutex(benchmark::State& state) {
+  static absl::Mutex* mu = new absl::Mutex;
+  for (auto _ : state) {
+    absl::MutexLock lock(mu);
+  }
+}
+BENCHMARK(BM_Mutex)->UseRealTime()->Threads(1)->ThreadPerCpu();
+
+static void DelayNs(int64_t ns, int* data) {
+  int64_t end = absl::base_internal::CycleClock::Now() +
+                ns * absl::base_internal::CycleClock::Frequency() / 1e9;
+  while (absl::base_internal::CycleClock::Now() < end) {
+    ++(*data);
+    benchmark::DoNotOptimize(*data);
+  }
+}
+
+template <typename MutexType>
+class RaiiLocker {
+ public:
+  explicit RaiiLocker(MutexType* mu) : mu_(mu) { mu_->Lock(); }
+  ~RaiiLocker() { mu_->Unlock(); }
+ private:
+  MutexType* mu_;
+};
+
+template <>
+class RaiiLocker<std::mutex> {
+ public:
+  explicit RaiiLocker(std::mutex* mu) : mu_(mu) { mu_->lock(); }
+  ~RaiiLocker() { mu_->unlock(); }
+ private:
+  std::mutex* mu_;
+};
+
+template <typename MutexType>
+void BM_Contended(benchmark::State& state) {
+  struct Shared {
+    MutexType mu;
+    int data = 0;
+  };
+  static auto* shared = new Shared;
+  int local = 0;
+  for (auto _ : state) {
+    // Here we model both local work outside of the critical section as well as
+    // some work inside of the critical section. The idea is to capture some
+    // more or less realisitic contention levels.
+    // If contention is too low, the benchmark won't measure anything useful.
+    // If contention is unrealistically high, the benchmark will favor
+    // bad mutex implementations that block and otherwise distract threads
+    // from the mutex and shared state for as much as possible.
+    // To achieve this amount of local work is multiplied by number of threads
+    // to keep ratio between local work and critical section approximately
+    // equal regardless of number of threads.
+    DelayNs(100 * state.threads, &local);
+    RaiiLocker<MutexType> locker(&shared->mu);
+    DelayNs(state.range(0), &shared->data);
+  }
+}
+
+BENCHMARK_TEMPLATE(BM_Contended, absl::Mutex)
+    ->UseRealTime()
+    // ThreadPerCpu poorly handles non-power-of-two CPU counts.
+    ->Threads(1)
+    ->Threads(2)
+    ->Threads(4)
+    ->Threads(6)
+    ->Threads(8)
+    ->Threads(12)
+    ->Threads(16)
+    ->Threads(24)
+    ->Threads(32)
+    ->Threads(48)
+    ->Threads(64)
+    ->Threads(96)
+    ->Threads(128)
+    ->Threads(192)
+    ->Threads(256)
+    // Some empirically chosen amounts of work in critical section.
+    // 1 is low contention, 200 is high contention and few values in between.
+    ->Arg(1)
+    ->Arg(20)
+    ->Arg(50)
+    ->Arg(200);
+
+BENCHMARK_TEMPLATE(BM_Contended, absl::base_internal::SpinLock)
+    ->UseRealTime()
+    // ThreadPerCpu poorly handles non-power-of-two CPU counts.
+    ->Threads(1)
+    ->Threads(2)
+    ->Threads(4)
+    ->Threads(6)
+    ->Threads(8)
+    ->Threads(12)
+    ->Threads(16)
+    ->Threads(24)
+    ->Threads(32)
+    ->Threads(48)
+    ->Threads(64)
+    ->Threads(96)
+    ->Threads(128)
+    ->Threads(192)
+    ->Threads(256)
+    // Some empirically chosen amounts of work in critical section.
+    // 1 is low contention, 200 is high contention and few values in between.
+    ->Arg(1)
+    ->Arg(20)
+    ->Arg(50)
+    ->Arg(200);
+
+BENCHMARK_TEMPLATE(BM_Contended, std::mutex)
+    ->UseRealTime()
+    // ThreadPerCpu poorly handles non-power-of-two CPU counts.
+    ->Threads(1)
+    ->Threads(2)
+    ->Threads(4)
+    ->Threads(6)
+    ->Threads(8)
+    ->Threads(12)
+    ->Threads(16)
+    ->Threads(24)
+    ->Threads(32)
+    ->Threads(48)
+    ->Threads(64)
+    ->Threads(96)
+    ->Threads(128)
+    ->Threads(192)
+    ->Threads(256)
+    // Some empirically chosen amounts of work in critical section.
+    // 1 is low contention, 200 is high contention and few values in between.
+    ->Arg(1)
+    ->Arg(20)
+    ->Arg(50)
+    ->Arg(200);
+
 // Measure the overhead of conditions on mutex release (when they must be
 // evaluated).  Mutex has (some) support for equivalence classes allowing
 // Conditions with the same function/argument to potentially not be multiply
@@ -82,13 +220,4 @@ constexpr int kMaxConditionWaiters = 1024;
 #endif
 BENCHMARK(BM_ConditionWaiters)->RangePair(0, 2, 1, kMaxConditionWaiters);
 
-void BM_ContendedMutex(benchmark::State& state) {
-  static absl::Mutex* mu = new absl::Mutex;
-  for (auto _ : state) {
-    absl::MutexLock lock(mu);
-  }
-}
-BENCHMARK(BM_ContendedMutex)->Threads(1);
-BENCHMARK(BM_ContendedMutex)->ThreadPerCpu();
-
 }  // namespace
diff --git a/absl/synchronization/notification.h b/absl/synchronization/notification.h
index 107932f2..f95f4d14 100644
--- a/absl/synchronization/notification.h
+++ b/absl/synchronization/notification.h
@@ -52,6 +52,7 @@
 
 #include <atomic>
 
+#include "absl/base/macros.h"
 #include "absl/synchronization/mutex.h"
 #include "absl/time/time.h"
 
diff --git a/absl/time/duration.cc b/absl/time/duration.cc
index 2950c7cd..b77d5ec9 100644
--- a/absl/time/duration.cc
+++ b/absl/time/duration.cc
@@ -78,10 +78,16 @@ constexpr int64_t kint64min = std::numeric_limits<int64_t>::min();
 
 // Can't use std::isinfinite() because it doesn't exist on windows.
 inline bool IsFinite(double d) {
+  if (std::isnan(d)) return false;
   return d != std::numeric_limits<double>::infinity() &&
          d != -std::numeric_limits<double>::infinity();
 }
 
+inline bool IsValidDivisor(double d) {
+  if (std::isnan(d)) return false;
+  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>
@@ -455,7 +461,7 @@ Duration& Duration::operator/=(int64_t r) {
 }
 
 Duration& Duration::operator/=(double r) {
-  if (time_internal::IsInfiniteDuration(*this) || r == 0.0) {
+  if (time_internal::IsInfiniteDuration(*this) || !IsValidDivisor(r)) {
     const bool is_neg = (std::signbit(r) != 0) != (rep_hi_ < 0);
     return *this = is_neg ? -InfiniteDuration() : InfiniteDuration();
   }
diff --git a/absl/time/duration_test.cc b/absl/time/duration_test.cc
index 775da91e..61f3c5c0 100644
--- a/absl/time/duration_test.cc
+++ b/absl/time/duration_test.cc
@@ -803,6 +803,40 @@ TEST(Duration, DivisionByZero) {
   EXPECT_EQ(-dbl_inf, absl::FDivDuration(-any_dur, zero));
 }
 
+TEST(Duration, NaN) {
+  // Note that IEEE 754 does not define the behavior of a nan's sign when it is
+  // copied, so the code below allows for either + or - InfiniteDuration.
+#define TEST_NAN_HANDLING(NAME, NAN)           \
+  do {                                         \
+    const auto inf = absl::InfiniteDuration(); \
+    auto x = NAME(NAN);                        \
+    EXPECT_TRUE(x == inf || x == -inf);        \
+    auto y = NAME(42);                         \
+    y *= NAN;                                  \
+    EXPECT_TRUE(y == inf || y == -inf);        \
+    auto z = NAME(42);                         \
+    z /= NAN;                                  \
+    EXPECT_TRUE(z == inf || z == -inf);        \
+  } while (0)
+
+  const double nan = std::numeric_limits<double>::quiet_NaN();
+  TEST_NAN_HANDLING(absl::Nanoseconds, nan);
+  TEST_NAN_HANDLING(absl::Microseconds, nan);
+  TEST_NAN_HANDLING(absl::Milliseconds, nan);
+  TEST_NAN_HANDLING(absl::Seconds, nan);
+  TEST_NAN_HANDLING(absl::Minutes, nan);
+  TEST_NAN_HANDLING(absl::Hours, nan);
+
+  TEST_NAN_HANDLING(absl::Nanoseconds, -nan);
+  TEST_NAN_HANDLING(absl::Microseconds, -nan);
+  TEST_NAN_HANDLING(absl::Milliseconds, -nan);
+  TEST_NAN_HANDLING(absl::Seconds, -nan);
+  TEST_NAN_HANDLING(absl::Minutes, -nan);
+  TEST_NAN_HANDLING(absl::Hours, -nan);
+
+#undef TEST_NAN_HANDLING
+}
+
 TEST(Duration, Range) {
   const absl::Duration range = ApproxYears(100 * 1e9);
   const absl::Duration range_future = range;
diff --git a/absl/time/time.h b/absl/time/time.h
index 3fa9378f..b86abf27 100644
--- a/absl/time/time.h
+++ b/absl/time/time.h
@@ -69,6 +69,7 @@
 #include <winsock2.h>
 #endif
 #include <chrono>  // NOLINT(build/c++11)
+#include <cmath>
 #include <cstdint>
 #include <ctime>
 #include <ostream>
@@ -411,10 +412,12 @@ Duration Milliseconds(T n) {
 }
 template <typename T, time_internal::EnableIfFloat<T> = 0>
 Duration Seconds(T n) {
-  if (n >= 0) {
+  if (n >= 0) {  // Note: `NaN >= 0` is false.
     if (n >= (std::numeric_limits<int64_t>::max)()) return InfiniteDuration();
     return time_internal::MakePosDoubleDuration(n);
   } else {
+    if (std::isnan(n))
+      return std::signbit(n) ? -InfiniteDuration() : InfiniteDuration();
     if (n <= (std::numeric_limits<int64_t>::min)()) return -InfiniteDuration();
     return -time_internal::MakePosDoubleDuration(-n);
   }
diff --git a/absl/types/internal/variant.h b/absl/types/internal/variant.h
index eff4fefe..477e5895 100644
--- a/absl/types/internal/variant.h
+++ b/absl/types/internal/variant.h
@@ -15,6 +15,7 @@
 // Implementation details of absl/types/variant.h, pulled into a
 // separate file to avoid cluttering the top of the API header with
 // implementation details.
+//
 
 #ifndef ABSL_TYPES_variant_internal_H_
 #define ABSL_TYPES_variant_internal_H_
@@ -1234,23 +1235,29 @@ using VariantCopyBase = absl::conditional_t<
 // Base that is dependent on whether or not the move-assign can be trivial.
 template <class... T>
 using VariantMoveAssignBase = absl::conditional_t<
-    absl::disjunction<absl::conjunction<absl::is_move_assignable<Union<T...>>,
-                                        std::is_move_constructible<Union<T...>>,
-                                        std::is_destructible<Union<T...>>>,
-                      absl::negation<absl::conjunction<
-                          std::is_move_constructible<T>...,
-                          absl::is_move_assignable<T>...>>>::value,
+    absl::disjunction<
+        absl::conjunction<absl::is_move_assignable<Union<T...>>,
+                          std::is_move_constructible<Union<T...>>,
+                          std::is_destructible<Union<T...>>>,
+        absl::negation<absl::conjunction<std::is_move_constructible<T>...,
+                                         // Note: We're not qualifying this with
+                                         // absl:: because it doesn't compile
+                                         // under MSVC.
+                                         is_move_assignable<T>...>>>::value,
     VariantCopyBase<T...>, VariantMoveAssignBaseNontrivial<T...>>;
 
 // Base that is dependent on whether or not the copy-assign can be trivial.
 template <class... T>
 using VariantCopyAssignBase = absl::conditional_t<
-    absl::disjunction<absl::conjunction<absl::is_copy_assignable<Union<T...>>,
-                                        std::is_copy_constructible<Union<T...>>,
-                                        std::is_destructible<Union<T...>>>,
-                      absl::negation<absl::conjunction<
-                          std::is_copy_constructible<T>...,
-                          absl::is_copy_assignable<T>...>>>::value,
+    absl::disjunction<
+        absl::conjunction<absl::is_copy_assignable<Union<T...>>,
+                          std::is_copy_constructible<Union<T...>>,
+                          std::is_destructible<Union<T...>>>,
+        absl::negation<absl::conjunction<std::is_copy_constructible<T>...,
+                                         // Note: We're not qualifying this with
+                                         // absl:: because it doesn't compile
+                                         // under MSVC.
+                                         is_copy_assignable<T>...>>>::value,
     VariantMoveAssignBase<T...>, VariantCopyAssignBaseNontrivial<T...>>;
 
 template <class... T>
diff --git a/absl/types/variant.h b/absl/types/variant.h
index 28aaef4f..48c5d7bf 100644
--- a/absl/types/variant.h
+++ b/absl/types/variant.h
@@ -82,7 +82,7 @@ namespace absl {
 // absl::variant
 // -----------------------------------------------------------------------------
 //
-// An 'absl::variant` type is a form of type-safe union. An `absl::variant` --
+// An `absl::variant` type is a form of type-safe union. An `absl::variant` --
 // except in exceptional cases -- always holds a value of one of its alternative
 // types.
 //
@@ -136,7 +136,7 @@ void swap(variant<Ts...>& v, variant<Ts...>& w) noexcept(noexcept(v.swap(w))) {
 
 // variant_size
 //
-// Returns the number of alterative types available for a given `absl::variant`
+// Returns the number of alternative types available for a given `absl::variant`
 // type as a compile-time constant expression. As this is a class template, it
 // is not generally useful for accessing the number of alternative types of
 // any given `absl::variant` instance.
@@ -454,7 +454,7 @@ class variant<T0, Tn...> : private variant_internal::VariantBase<T0, Tn...> {
                                   std::is_object<Tn>...>::value,
                 "Attempted to instantiate a variant containing a non-object "
                 "type.");
-  // Intentionally not qualifing `negation` with `absl::` to work around a bug
+  // Intentionally not qualifying `negation` with `absl::` to work around a bug
   // in MSVC 2015 with inline namespace and variadic template.
   static_assert(absl::conjunction<negation<std::is_array<T0> >,
                                   negation<std::is_array<Tn> >...>::value,
@@ -562,7 +562,7 @@ class variant<T0, Tn...> : private variant_internal::VariantBase<T0, Tn...> {
 
   // Assignment Operators
 
-  // Copy assignement operator
+  // Copy assignment operator
   variant& operator=(const variant& other) = default;
 
   // Move assignment operator