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-rw-r--r--absl/base/BUILD.bazel21
-rw-r--r--absl/base/CMakeLists.txt43
-rw-r--r--absl/base/attributes.h12
-rw-r--r--absl/base/config.h7
-rw-r--r--absl/base/exception_safety_testing_test.cc25
-rw-r--r--absl/base/inline_variable_test.cc62
-rw-r--r--absl/base/inline_variable_test_a.cc (renamed from absl/base/internal/log_severity.cc)12
-rw-r--r--absl/base/inline_variable_test_b.cc25
-rw-r--r--absl/base/internal/exception_safety_testing.cc7
-rw-r--r--absl/base/internal/exception_safety_testing.h61
-rw-r--r--absl/base/internal/inline_variable.h127
-rw-r--r--absl/base/internal/inline_variable_testing.h44
-rw-r--r--absl/base/internal/malloc_extension.cc39
-rw-r--r--absl/base/internal/malloc_extension_test.cc23
-rw-r--r--absl/base/internal/malloc_hook.cc161
-rw-r--r--absl/base/internal/malloc_hook.h111
-rw-r--r--absl/base/internal/malloc_hook_c.h88
-rw-r--r--absl/base/internal/per_thread_tls.h2
-rw-r--r--absl/base/internal/raw_logging.cc2
-rw-r--r--absl/base/internal/raw_logging.h2
-rw-r--r--absl/base/internal/spinlock.h2
-rw-r--r--absl/base/internal/thread_identity.h2
-rw-r--r--absl/base/log_severity.h (renamed from absl/base/internal/log_severity.h)0
-rw-r--r--absl/base/macros.h2
24 files changed, 522 insertions, 358 deletions
diff --git a/absl/base/BUILD.bazel b/absl/base/BUILD.bazel
index 743add7e0127..9bb7bfa14efb 100644
--- a/absl/base/BUILD.bazel
+++ b/absl/base/BUILD.bazel
@@ -82,7 +82,6 @@ cc_library(
     srcs = ["internal/malloc_extension.cc"],
     hdrs = [
         "internal/malloc_extension.h",
-        "internal/malloc_extension_c.h",
     ],
     copts = ABSL_DEFAULT_COPTS,
     visibility = [
@@ -129,6 +128,7 @@ cc_library(
     name = "base_internal",
     hdrs = [
         "internal/identity.h",
+        "internal/inline_variable.h",
         "internal/invoke.h",
     ],
     copts = ABSL_DEFAULT_COPTS,
@@ -152,7 +152,6 @@ cc_library(
         "casts.h",
         "internal/atomic_hook.h",
         "internal/cycleclock.h",
-        "internal/log_severity.h",
         "internal/low_level_scheduling.h",
         "internal/per_thread_tls.h",
         "internal/raw_logging.h",
@@ -161,6 +160,7 @@ cc_library(
         "internal/thread_identity.h",
         "internal/tsan_mutex_interface.h",
         "internal/unscaledcycleclock.h",
+        "log_severity.h",
     ],
     copts = ABSL_DEFAULT_COPTS,
     deps = [
@@ -236,6 +236,7 @@ cc_library(
     hdrs = ["internal/exception_safety_testing.h"],
     copts = ABSL_TEST_COPTS + ABSL_EXCEPTIONS_FLAG,
     deps = [
+        ":base",
         ":config",
         ":pretty_function",
         "//absl/memory",
@@ -258,6 +259,22 @@ cc_test(
 )
 
 cc_test(
+    name = "inline_variable_test",
+    size = "small",
+    srcs = [
+        "inline_variable_test.cc",
+        "inline_variable_test_a.cc",
+        "inline_variable_test_b.cc",
+        "internal/inline_variable_testing.h",
+    ],
+    copts = ABSL_TEST_COPTS,
+    deps = [
+        ":base_internal",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_test(
     name = "invoke_test",
     size = "small",
     srcs = ["invoke_test.cc"],
diff --git a/absl/base/CMakeLists.txt b/absl/base/CMakeLists.txt
index 3e94d51fef8e..9d2de55fea90 100644
--- a/absl/base/CMakeLists.txt
+++ b/absl/base/CMakeLists.txt
@@ -20,6 +20,7 @@ list(APPEND BASE_PUBLIC_HEADERS
   "casts.h"
   "config.h"
   "dynamic_annotations.h"
+  "log_severity.h"
   "macros.h"
   "optimization.h"
   "policy_checks.h"
@@ -33,17 +34,18 @@ list(APPEND BASE_INTERNAL_HEADERS
   "internal/cycleclock.h"
   "internal/endian.h"
   "internal/exception_testing.h"
+  "internal/exception_safety_testing.h"
   "internal/identity.h"
   "internal/invoke.h"
-  "internal/log_severity.h"
+  "internal/inline_variable.h"
   "internal/low_level_alloc.h"
   "internal/low_level_scheduling.h"
-  "internal/malloc_extension_c.h"
   "internal/malloc_extension.h"
   "internal/malloc_hook_c.h"
   "internal/malloc_hook.h"
   "internal/malloc_hook_invoke.h"
   "internal/per_thread_tls.h"
+  "internal/pretty_function.h"
   "internal/raw_logging.h"
   "internal/scheduling_mode.h"
   "internal/spinlock.h"
@@ -58,8 +60,9 @@ list(APPEND BASE_INTERNAL_HEADERS
 
 
 # absl_base main library
-list(APPEND BASE_SRC 
+list(APPEND BASE_SRC
   "internal/cycleclock.cc"
+  "internal/exception_safety_testing.cc"
   "internal/raw_logging.cc"
   "internal/spinlock.cc"
   "internal/sysinfo.cc"
@@ -212,6 +215,26 @@ absl_test(
 )
 
 
+# test inline_variable_test
+list(APPEND INLINE_VARIABLE_TEST_SRC
+  "internal/inline_variable_testing.h"
+  "inline_variable_test.cc"
+  "inline_variable_test_a.cc"
+  "inline_variable_test_b.cc"
+)
+
+set(INLINE_VARIABLE_TEST_PUBLIC_LIBRARIES absl::base)
+
+absl_test(
+  TARGET
+    inline_variable_test
+  SOURCES
+    ${INLINE_VARIABLE_TEST_SRC}
+  PUBLIC_LIBRARIES
+    ${INLINE_VARIABLE_TEST_PUBLIC_LIBRARIES}
+)
+
+
 # test spinlock_test_common
 set(SPINLOCK_TEST_COMMON_SRC "spinlock_test_common.cc")
 set(SPINLOCK_TEST_COMMON_PUBLIC_LIBRARIES absl::base absl::synchronization)
@@ -319,6 +342,20 @@ absl_test(
     ${THREAD_IDENTITY_TEST_PUBLIC_LIBRARIES}
 )
 
+#test exceptions_safety_testing_test
+set(EXCEPTION_SAFETY_TESTING_TEST_SRC "exception_safety_testing_test.cc")
+set(EXCEPTION_SAFETY_TESTING_TEST_PUBLIC_LIBRARIES absl::base absl::memory absl::meta absl::strings absl::optional)
+
+absl_test(
+  TARGET
+    absl_exception_safety_testing_test
+  SOURCES
+    ${EXCEPTION_SAFETY_TESTING_TEST_SRC}
+  PUBLIC_LIBRARIES
+    ${EXCEPTION_SAFETY_TESTING_TEST_PUBLIC_LIBRARIES}
+  PRIVATE_COMPILE_FLAGS
+    ${ABSL_EXCEPTIONS_FLAG}
+)
 
 # test absl_malloc_extension_system_malloc_test
 set(MALLOC_EXTENSION_SYSTEM_MALLOC_TEST_SRC "internal/malloc_extension_test.cc")
diff --git a/absl/base/attributes.h b/absl/base/attributes.h
index 02bb030f5e5a..4e1fc8b550d1 100644
--- a/absl/base/attributes.h
+++ b/absl/base/attributes.h
@@ -281,6 +281,18 @@
 #define ABSL_ATTRIBUTE_NO_SANITIZE_CFI
 #endif
 
+// ABSL_ATTRIBUTE_RETURNS_NONNULL
+//
+// Tells the compiler that a particular function never returns a null pointer.
+#if ABSL_HAVE_ATTRIBUTE(returns_nonnull) || \
+    (defined(__GNUC__) && \
+     (__GNUC__ > 5 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 9)) && \
+     !defined(__clang__))
+#define ABSL_ATTRIBUTE_RETURNS_NONNULL __attribute__((returns_nonnull))
+#else
+#define ABSL_ATTRIBUTE_RETURNS_NONNULL
+#endif
+
 // ABSL_HAVE_ATTRIBUTE_SECTION
 //
 // Indicates whether labeled sections are supported. Labeled sections are not
diff --git a/absl/base/config.h b/absl/base/config.h
index 3f3b8b3a64e3..6703d0eac715 100644
--- a/absl/base/config.h
+++ b/absl/base/config.h
@@ -138,9 +138,10 @@
 // supported.
 #ifdef ABSL_HAVE_THREAD_LOCAL
 #error ABSL_HAVE_THREAD_LOCAL cannot be directly set
-#elif !defined(__apple_build_version__) ||   \
-    ((__apple_build_version__ >= 8000042) && \
-     !(TARGET_OS_IPHONE && __IPHONE_OS_VERSION_MIN_REQUIRED < __IPHONE_9_0))
+#elif (!defined(__apple_build_version__) || \
+       (__apple_build_version__ >= 8000042)) && \
+      !(defined(__APPLE__) && TARGET_OS_IPHONE && \
+        __IPHONE_OS_VERSION_MIN_REQUIRED < __IPHONE_9_0)
 // Notes: Xcode's clang did not support `thread_local` until version
 // 8, and even then not for all iOS < 9.0.
 #define ABSL_HAVE_THREAD_LOCAL 1
diff --git a/absl/base/exception_safety_testing_test.cc b/absl/base/exception_safety_testing_test.cc
index 1fc03861784e..5477b40a5bed 100644
--- a/absl/base/exception_safety_testing_test.cc
+++ b/absl/base/exception_safety_testing_test.cc
@@ -63,7 +63,7 @@ TEST_F(ThrowingValueTest, Throws) {
 // the countdown doesn't hit 0, and doesn't modify the state of the
 // ThrowingValue if it throws
 template <typename F>
-void TestOp(F&& f) {
+void TestOp(const F& f) {
   UnsetCountdown();
   ExpectNoThrow(f);
 
@@ -153,11 +153,21 @@ TEST_F(ThrowingValueTest, ThrowingStreamOps) {
   TestOp([&]() { std::cout << bomb; });
 }
 
+template <typename F>
+void TestAllocatingOp(const F& f) {
+  UnsetCountdown();
+  ExpectNoThrow(f);
+
+  SetCountdown();
+  EXPECT_THROW(f(), exceptions_internal::TestBadAllocException);
+  UnsetCountdown();
+}
+
 TEST_F(ThrowingValueTest, ThrowingAllocatingOps) {
   // make_unique calls unqualified operator new, so these exercise the
   // ThrowingValue overloads.
-  TestOp([]() { return absl::make_unique<ThrowingValue<>>(1); });
-  TestOp([]() { return absl::make_unique<ThrowingValue<>[]>(2); });
+  TestAllocatingOp([]() { return absl::make_unique<ThrowingValue<>>(1); });
+  TestAllocatingOp([]() { return absl::make_unique<ThrowingValue<>[]>(2); });
 }
 
 TEST_F(ThrowingValueTest, NonThrowingMoveCtor) {
@@ -399,7 +409,8 @@ struct CallOperator {
 };
 
 struct NonNegative {
-  friend testing::AssertionResult AbslCheckInvariants(NonNegative* g) {
+  friend testing::AssertionResult AbslCheckInvariants(
+      NonNegative* g, absl::InternalAbslNamespaceFinder) {
     if (g->i >= 0) return testing::AssertionSuccess();
     return testing::AssertionFailure()
            << "i should be non-negative but is " << g->i;
@@ -503,7 +514,8 @@ struct HasReset : public NonNegative {
 
   void reset() { i = 0; }
 
-  friend bool AbslCheckInvariants(HasReset* h) {
+  friend bool AbslCheckInvariants(HasReset* h,
+                                  absl::InternalAbslNamespaceFinder) {
     h->reset();
     return h->i == 0;
   }
@@ -591,7 +603,8 @@ struct ExhaustivenessTester {
     return true;
   }
 
-  friend testing::AssertionResult AbslCheckInvariants(ExhaustivenessTester*) {
+  friend testing::AssertionResult AbslCheckInvariants(
+      ExhaustivenessTester*, absl::InternalAbslNamespaceFinder) {
     return testing::AssertionSuccess();
   }
 
diff --git a/absl/base/inline_variable_test.cc b/absl/base/inline_variable_test.cc
new file mode 100644
index 000000000000..5499189a3da9
--- /dev/null
+++ b/absl/base/inline_variable_test.cc
@@ -0,0 +1,62 @@
+// 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
+//
+//      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 <type_traits>
+
+#include "absl/base/internal/inline_variable.h"
+#include "absl/base/internal/inline_variable_testing.h"
+
+#include "gtest/gtest.h"
+
+namespace absl {
+namespace inline_variable_testing_internal {
+namespace {
+
+TEST(InlineVariableTest, Constexpr) {
+  static_assert(inline_variable_foo.value == 5, "");
+  static_assert(other_inline_variable_foo.value == 5, "");
+  static_assert(inline_variable_int == 5, "");
+  static_assert(other_inline_variable_int == 5, "");
+}
+
+TEST(InlineVariableTest, DefaultConstructedIdentityEquality) {
+  EXPECT_EQ(get_foo_a().value, 5);
+  EXPECT_EQ(get_foo_b().value, 5);
+  EXPECT_EQ(&get_foo_a(), &get_foo_b());
+}
+
+TEST(InlineVariableTest, DefaultConstructedIdentityInequality) {
+  EXPECT_NE(&inline_variable_foo, &other_inline_variable_foo);
+}
+
+TEST(InlineVariableTest, InitializedIdentityEquality) {
+  EXPECT_EQ(get_int_a(), 5);
+  EXPECT_EQ(get_int_b(), 5);
+  EXPECT_EQ(&get_int_a(), &get_int_b());
+}
+
+TEST(InlineVariableTest, InitializedIdentityInequality) {
+  EXPECT_NE(&inline_variable_int, &other_inline_variable_int);
+}
+
+TEST(InlineVariableTest, FunPtrType) {
+  static_assert(
+      std::is_same<void(*)(),
+                   std::decay<decltype(inline_variable_fun_ptr)>::type>::value,
+      "");
+}
+
+}  // namespace
+}  // namespace inline_variable_testing_internal
+}  // namespace absl
diff --git a/absl/base/internal/log_severity.cc b/absl/base/inline_variable_test_a.cc
index 430ac45848a0..a3bf3b68b3cf 100644
--- a/absl/base/internal/log_severity.cc
+++ b/absl/base/inline_variable_test_a.cc
@@ -12,4 +12,14 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#include "absl/base/internal/log_severity.h"
+#include "absl/base/internal/inline_variable_testing.h"
+
+namespace absl {
+namespace inline_variable_testing_internal {
+
+const Foo& get_foo_a() { return inline_variable_foo; }
+
+const int& get_int_a() { return inline_variable_int; }
+
+}  // namespace inline_variable_testing_internal
+}  // namespace absl
diff --git a/absl/base/inline_variable_test_b.cc b/absl/base/inline_variable_test_b.cc
new file mode 100644
index 000000000000..b4b9393a5585
--- /dev/null
+++ b/absl/base/inline_variable_test_b.cc
@@ -0,0 +1,25 @@
+// 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
+//
+//      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/base/internal/inline_variable_testing.h"
+
+namespace absl {
+namespace inline_variable_testing_internal {
+
+const Foo& get_foo_b() { return inline_variable_foo; }
+
+const int& get_int_b() { return inline_variable_int; }
+
+}  // namespace inline_variable_testing_internal
+}  // namespace absl
diff --git a/absl/base/internal/exception_safety_testing.cc b/absl/base/internal/exception_safety_testing.cc
index ab8d6c9fb4d0..821438ecc28c 100644
--- a/absl/base/internal/exception_safety_testing.cc
+++ b/absl/base/internal/exception_safety_testing.cc
@@ -23,8 +23,11 @@ namespace exceptions_internal {
 
 int countdown = -1;
 
-void MaybeThrow(absl::string_view msg) {
-  if (countdown-- == 0) throw TestException(msg);
+void MaybeThrow(absl::string_view msg, bool throw_bad_alloc) {
+  if (countdown-- == 0) {
+    if (throw_bad_alloc) throw TestBadAllocException(msg);
+    throw TestException(msg);
+  }
 }
 
 testing::AssertionResult FailureMessage(const TestException& e,
diff --git a/absl/base/internal/exception_safety_testing.h b/absl/base/internal/exception_safety_testing.h
index a0127a8819fa..8eac2264884f 100644
--- a/absl/base/internal/exception_safety_testing.h
+++ b/absl/base/internal/exception_safety_testing.h
@@ -35,6 +35,8 @@
 #include "absl/types/optional.h"
 
 namespace absl {
+struct InternalAbslNamespaceFinder {};
+
 struct AllocInspector;
 
 // A configuration enum for Throwing*.  Operations whose flags are set will
@@ -71,31 +73,45 @@ constexpr bool ThrowingAllowed(NoThrow flags, NoThrow flag) {
 class TestException {
  public:
   explicit TestException(absl::string_view msg) : msg_(msg) {}
-  absl::string_view what() const { return msg_; }
+  virtual ~TestException() {}
+  virtual const char* what() const noexcept { return msg_.c_str(); }
 
  private:
   std::string msg_;
 };
 
+// TestBadAllocException exists because allocation functions must throw an
+// exception which can be caught by a handler of std::bad_alloc.  We use a child
+// class of std::bad_alloc so we can customise the error message, and also
+// derive from TestException so we don't accidentally end up catching an actual
+// bad_alloc exception in TestExceptionSafety.
+class TestBadAllocException : public std::bad_alloc, public TestException {
+ public:
+  explicit TestBadAllocException(absl::string_view msg)
+      : TestException(msg) {}
+  using TestException::what;
+};
+
 extern int countdown;
 
-void MaybeThrow(absl::string_view msg);
+void MaybeThrow(absl::string_view msg, bool throw_bad_alloc = false);
 
 testing::AssertionResult FailureMessage(const TestException& e,
                                         int countdown) noexcept;
 
 class TrackedObject {
+ public:
+  TrackedObject(const TrackedObject&) = delete;
+  TrackedObject(TrackedObject&&) = delete;
+
  protected:
-  explicit TrackedObject(absl::string_view child_ctor) {
+  explicit TrackedObject(const char* child_ctor) {
     if (!GetAllocs().emplace(this, child_ctor).second) {
       ADD_FAILURE() << "Object at address " << static_cast<void*>(this)
                     << " re-constructed in ctor " << child_ctor;
     }
   }
 
-  TrackedObject(const TrackedObject&) = delete;
-  TrackedObject(TrackedObject&&) = delete;
-
   static std::unordered_map<TrackedObject*, absl::string_view>& GetAllocs() {
     static auto* m =
         new std::unordered_map<TrackedObject*, absl::string_view>();
@@ -120,10 +136,10 @@ using FactoryType = typename absl::result_of_t<Factory()>::element_type;
 template <typename Factory, typename Op, typename Checker>
 absl::optional<testing::AssertionResult> TestCheckerAtCountdown(
     Factory factory, const Op& op, int count, const Checker& check) {
-  exceptions_internal::countdown = count;
   auto t_ptr = factory();
   absl::optional<testing::AssertionResult> out;
   try {
+    exceptions_internal::countdown = count;
     op(t_ptr.get());
   } catch (const exceptions_internal::TestException& e) {
     out.emplace(check(t_ptr.get()));
@@ -141,6 +157,10 @@ int UpdateOut(Factory factory, const Op& op, int count, const Checker& checker,
   return 0;
 }
 
+// Declare AbslCheckInvariants so that it can be found eventually via ADL.
+// Taking `...` gives it the lowest possible precedence.
+void AbslCheckInvariants(...);
+
 // Returns an optional with the result of the check if op fails, or an empty
 // optional if op passes
 template <typename Factory, typename Op, typename... Checkers>
@@ -148,8 +168,9 @@ absl::optional<testing::AssertionResult> TestAtCountdown(
     Factory factory, const Op& op, int count, const Checkers&... checkers) {
   // Don't bother with the checkers if the class invariants are already broken.
   auto out = TestCheckerAtCountdown(
-      factory, op, count,
-      [](FactoryType<Factory>* t_ptr) { return AbslCheckInvariants(t_ptr); });
+      factory, op, count, [](FactoryType<Factory>* t_ptr) {
+        return AbslCheckInvariants(t_ptr, InternalAbslNamespaceFinder());
+      });
   if (!out.has_value()) return out;
 
   // Run each checker, short circuiting after the first failure
@@ -483,7 +504,7 @@ class ThrowingValue : private exceptions_internal::TrackedObject {
   static void* operator new(size_t s, Args&&... args) noexcept(
       !exceptions_internal::ThrowingAllowed(Flags, NoThrow::kAllocation)) {
     if (exceptions_internal::ThrowingAllowed(Flags, NoThrow::kAllocation)) {
-      exceptions_internal::MaybeThrow(ABSL_PRETTY_FUNCTION);
+      exceptions_internal::MaybeThrow(ABSL_PRETTY_FUNCTION, true);
     }
     return ::operator new(s, std::forward<Args>(args)...);
   }
@@ -492,7 +513,7 @@ class ThrowingValue : private exceptions_internal::TrackedObject {
   static void* operator new[](size_t s, Args&&... args) noexcept(
       !exceptions_internal::ThrowingAllowed(Flags, NoThrow::kAllocation)) {
     if (exceptions_internal::ThrowingAllowed(Flags, NoThrow::kAllocation)) {
-      exceptions_internal::MaybeThrow(ABSL_PRETTY_FUNCTION);
+      exceptions_internal::MaybeThrow(ABSL_PRETTY_FUNCTION, true);
     }
     return ::operator new[](s, std::forward<Args>(args)...);
   }
@@ -630,10 +651,7 @@ class ThrowingAllocator : private exceptions_internal::TrackedObject {
     p->~U();
   }
 
-  size_type max_size() const
-      noexcept(!exceptions_internal::ThrowingAllowed(Flags,
-                                                     NoThrow::kNoThrow)) {
-    ReadStateAndMaybeThrow(ABSL_PRETTY_FUNCTION);
+  size_type max_size() const noexcept {
     return std::numeric_limits<difference_type>::max() / sizeof(value_type);
   }
 
@@ -720,9 +738,12 @@ T TestThrowingCtor(Args&&... args) {
 
 // Tests that performing operation Op on a T follows exception safety
 // guarantees.  By default only tests the basic guarantee. There must be a
-// function, AbslCheckInvariants(T*) which returns
-// anything convertible to bool and which makes sure the invariants of the type
-// are upheld.  This is called before any of the checkers.
+// function, AbslCheckInvariants(T*, absl::InternalAbslNamespaceFinder) which
+// returns anything convertible to bool and which makes sure the invariants of
+// the type are upheld.  This is called before any of the checkers.  The
+// InternalAbslNamespaceFinder is unused, and just helps find
+// AbslCheckInvariants for absl types which become aliases to std::types in
+// C++17.
 //
 // Parameters:
 //   * TFactory: operator() returns a unique_ptr to the type under test (T).  It
@@ -740,11 +761,13 @@ template <typename TFactory, typename FunctionFromTPtrToVoid,
 testing::AssertionResult TestExceptionSafety(TFactory factory,
                                              FunctionFromTPtrToVoid&& op,
                                              const Checkers&... checkers) {
+  struct Cleanup {
+    ~Cleanup() { UnsetCountdown(); }
+  } c;
   for (int countdown = 0;; ++countdown) {
     auto out = exceptions_internal::TestAtCountdown(factory, op, countdown,
                                                     checkers...);
     if (!out.has_value()) {
-      UnsetCountdown();
       return testing::AssertionSuccess();
     }
     if (!*out) return *out;
diff --git a/absl/base/internal/inline_variable.h b/absl/base/internal/inline_variable.h
new file mode 100644
index 000000000000..a65fe89354cb
--- /dev/null
+++ b/absl/base/internal/inline_variable.h
@@ -0,0 +1,127 @@
+// 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
+//
+//      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.
+
+#ifndef ABSL_BASE_INTERNAL_INLINE_VARIABLE_EMULATION_H_
+#define ABSL_BASE_INTERNAL_INLINE_VARIABLE_EMULATION_H_
+
+#include <type_traits>
+
+#include "absl/base/internal/identity.h"
+
+// File:
+//   This file define a macro that allows the creation of or emulation of C++17
+//   inline variables based on whether or not the feature is supported.
+
+////////////////////////////////////////////////////////////////////////////////
+// Macro: ABSL_INTERNAL_INLINE_CONSTEXPR(type, name, init)
+//
+// Description:
+//   Expands to the equivalent of an inline constexpr instance of the specified
+//   `type` and `name`, initialized to the value `init`. If the compiler being
+//   used is detected as supporting actual inline variables as a language
+//   feature, then the macro expands to an actual inline variable definition.
+//
+// Requires:
+//   `type` is a type that is usable in an extern variable declaration.
+//
+// Requires: `name` is a valid identifier
+//
+// Requires:
+//   `init` is an expression that can be used in the following definition:
+//     constexpr type name = init;
+//
+// Usage:
+//
+//   // Equivalent to: `inline constexpr size_t variant_npos = -1;`
+//   ABSL_INTERNAL_INLINE_CONSTEXPR(size_t, variant_npos, -1);
+//
+// Differences in implementation:
+//   For a direct, language-level inline variable, decltype(name) will be the
+//   type that was specified along with const qualification, whereas for
+//   emulated inline variables, decltype(name) may be different (in practice
+//   it will likely be a reference type).
+////////////////////////////////////////////////////////////////////////////////
+
+// ABSL_INTERNAL_HAS_WARNING()
+//
+// If the compiler supports the `__has_warning` extension for detecting
+// warnings, then this macro is defined to be `__has_warning`.
+//
+// If the compiler does not support `__has_warning`, invocations expand to 0.
+//
+// For clang's documentation of `__has_warning`, see
+// https://clang.llvm.org/docs/LanguageExtensions.html#has-warning
+#if defined(__has_warning)
+#define ABSL_INTERNAL_HAS_WARNING __has_warning
+#else  // Otherwise, be optimistic and assume the warning is not enabled.
+#define ABSL_INTERNAL_HAS_WARNING(warning) 0
+#endif  // defined(__has_warning)
+
+// If the compiler supports inline variables and does not warn when used...
+#if defined(__cpp_inline_variables) && \
+    !ABSL_INTERNAL_HAS_WARNING("-Wc++98-c++11-c++14-compat")
+
+// Clang's -Wmissing-variable-declarations option erroneously warned that
+// inline constexpr objects need to be pre-declared. This has now been fixed,
+// but we will need to support this workaround for people building with older
+// versions of clang.
+//
+// Bug: https://bugs.llvm.org/show_bug.cgi?id=35862
+//
+// Note:
+//   identity_t is used here so that the const and name are in the
+//   appropriate place for pointer types, reference types, function pointer
+//   types, etc..
+#if defined(__clang__) && \
+    ABSL_INTERNAL_HAS_WARNING("-Wmissing-variable-declarations")
+#define ABSL_INTERNAL_EXTERN_DECL(type, name) \
+  extern const ::absl::internal::identity_t<type> name;
+#else  // Otherwise, just define the macro to do nothing.
+#define ABSL_INTERNAL_EXTERN_DECL(type, name)
+#endif  // defined(__clang__) &&
+        // ABSL_INTERNAL_HAS_WARNING("-Wmissing-variable-declarations")
+
+// See above comment at top of file for details.
+#define ABSL_INTERNAL_INLINE_CONSTEXPR(type, name, init) \
+  ABSL_INTERNAL_EXTERN_DECL(type, name)                  \
+  inline constexpr ::absl::internal::identity_t<type> name = init
+
+#else  // Otherwise, we need to emulate inline variables...
+
+// See above comment at top of file for details.
+//
+// Note:
+//   identity_t is used here so that the const and name are in the
+//   appropriate place for pointer types, reference types, function pointer
+//   types, etc..
+#define ABSL_INTERNAL_INLINE_CONSTEXPR(var_type, name, init)                  \
+  template <class /*AbslInternalDummy*/ = void>                               \
+  struct AbslInternalInlineVariableHolder##name {                             \
+    static constexpr ::absl::internal::identity_t<var_type> kInstance = init; \
+  };                                                                          \
+                                                                              \
+  template <class AbslInternalDummy>                                          \
+  constexpr ::absl::internal::identity_t<var_type>                            \
+      AbslInternalInlineVariableHolder##name<AbslInternalDummy>::kInstance;   \
+                                                                              \
+  static constexpr const ::absl::internal::identity_t<var_type>&              \
+      name = /* NOLINT */                                                     \
+      AbslInternalInlineVariableHolder##name<>::kInstance;                    \
+  static_assert(sizeof(void (*)(decltype(name))) != 0,                        \
+                "Silence unused variable warnings.")
+
+#endif  // defined(__cpp_inline_variables) &&
+        // !ABSL_INTERNAL_HAS_WARNING("-Wc++98-c++11-c++14-compat")
+
+#endif  // ABSL_BASE_INTERNAL_INLINE_VARIABLE_EMULATION_H_
diff --git a/absl/base/internal/inline_variable_testing.h b/absl/base/internal/inline_variable_testing.h
new file mode 100644
index 000000000000..a0dd2bb28a40
--- /dev/null
+++ b/absl/base/internal/inline_variable_testing.h
@@ -0,0 +1,44 @@
+// 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
+//
+//      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.
+
+#ifndef ABSL_BASE_INLINE_VARIABLE_TESTING_H_
+#define ABSL_BASE_INLINE_VARIABLE_TESTING_H_
+
+#include "absl/base/internal/inline_variable.h"
+
+namespace absl {
+namespace inline_variable_testing_internal {
+
+struct Foo {
+  int value = 5;
+};
+
+ABSL_INTERNAL_INLINE_CONSTEXPR(Foo, inline_variable_foo, {});
+ABSL_INTERNAL_INLINE_CONSTEXPR(Foo, other_inline_variable_foo, {});
+
+ABSL_INTERNAL_INLINE_CONSTEXPR(int, inline_variable_int, 5);
+ABSL_INTERNAL_INLINE_CONSTEXPR(int, other_inline_variable_int, 5);
+
+ABSL_INTERNAL_INLINE_CONSTEXPR(void(*)(), inline_variable_fun_ptr, nullptr);
+
+const Foo& get_foo_a();
+const Foo& get_foo_b();
+
+const int& get_int_a();
+const int& get_int_b();
+
+}  // namespace inline_variable_testing_internal
+}  // namespace absl
+
+#endif  // ABSL_BASE_INLINE_VARIABLE_TESTING_H_
diff --git a/absl/base/internal/malloc_extension.cc b/absl/base/internal/malloc_extension.cc
index d48ec5bcf548..5b90653360aa 100644
--- a/absl/base/internal/malloc_extension.cc
+++ b/absl/base/internal/malloc_extension.cc
@@ -20,7 +20,6 @@
 #include <string>
 
 #include "absl/base/dynamic_annotations.h"
-#include "absl/base/internal/malloc_extension_c.h"
 
 namespace absl {
 namespace base_internal {
@@ -155,44 +154,6 @@ void MallocExtension::GetFragmentationProfile(MallocExtensionWriter*) {}
 }  // namespace base_internal
 }  // namespace absl
 
-// These are C shims that work on the current instance.
-
-#define C_SHIM(fn, retval, paramlist, arglist)                           \
-  extern "C" retval MallocExtension_##fn paramlist {                     \
-    return absl::base_internal::MallocExtension::instance()->fn arglist; \
-  }
-
-C_SHIM(VerifyAllMemory, int, (void), ());
-C_SHIM(VerifyNewMemory, int, (const void* p), (p));
-C_SHIM(VerifyArrayNewMemory, int, (const void* p), (p));
-C_SHIM(VerifyMallocMemory, int, (const void* p), (p));
-C_SHIM(
-    MallocMemoryStats, int,
-    (int* blocks, size_t* total,
-     int histogram[absl::base_internal::MallocExtension::kMallocHistogramSize]),
-    (blocks, total, histogram));
-
-C_SHIM(GetStats, void,
-       (char* buffer, int buffer_length), (buffer, buffer_length));
-C_SHIM(GetNumericProperty, int,
-       (const char* property, size_t* value), (property, value));
-C_SHIM(SetNumericProperty, int,
-       (const char* property, size_t value), (property, value));
-
-C_SHIM(MarkThreadIdle, void, (void), ());
-C_SHIM(MarkThreadBusy, void, (void), ());
-C_SHIM(ReleaseFreeMemory, void, (void), ());
-C_SHIM(ReleaseToSystem, void, (size_t num_bytes), (num_bytes));
-C_SHIM(GetEstimatedAllocatedSize, size_t, (size_t size), (size));
-C_SHIM(GetAllocatedSize, size_t, (const void* p), (p));
-
-// Can't use the shim here because of the need to translate the enums.
-extern "C"
-MallocExtension_Ownership MallocExtension_GetOwnership(const void* p) {
-  return static_cast<MallocExtension_Ownership>(
-      absl::base_internal::MallocExtension::instance()->GetOwnership(p));
-}
-
 // Default implementation just returns size. The expectation is that
 // the linked-in malloc implementation might provide an override of
 // this weak function with a better implementation.
diff --git a/absl/base/internal/malloc_extension_test.cc b/absl/base/internal/malloc_extension_test.cc
index 246875a030ef..76605eb19936 100644
--- a/absl/base/internal/malloc_extension_test.cc
+++ b/absl/base/internal/malloc_extension_test.cc
@@ -19,7 +19,6 @@
 
 #include "gtest/gtest.h"
 #include "absl/base/internal/malloc_extension.h"
-#include "absl/base/internal/malloc_extension_c.h"
 
 namespace absl {
 namespace base_internal {
@@ -35,15 +34,12 @@ TEST(MallocExtension, MallocExtension) {
   } else {
     ASSERT_TRUE(MallocExtension::instance()->GetNumericProperty(
         "generic.current_allocated_bytes", &cxx_bytes_used));
-    ASSERT_TRUE(MallocExtension_GetNumericProperty(
-        "generic.current_allocated_bytes", &c_bytes_used));
 #ifndef MEMORY_SANITIZER
     EXPECT_GT(cxx_bytes_used, 1000);
     EXPECT_GT(c_bytes_used, 1000);
 #endif
 
     EXPECT_TRUE(MallocExtension::instance()->VerifyAllMemory());
-    EXPECT_TRUE(MallocExtension_VerifyAllMemory());
 
     EXPECT_EQ(MallocExtension::kOwned,
               MallocExtension::instance()->GetOwnership(a));
@@ -65,30 +61,11 @@ TEST(MallocExtension, MallocExtension) {
                 MallocExtension::instance()->GetEstimatedAllocatedSize(i));
       free(p);
     }
-
-    // Check the c-shim version too.
-    EXPECT_EQ(MallocExtension_kOwned, MallocExtension_GetOwnership(a));
-    EXPECT_EQ(MallocExtension_kNotOwned,
-              MallocExtension_GetOwnership(&cxx_bytes_used));
-    EXPECT_EQ(MallocExtension_kNotOwned, MallocExtension_GetOwnership(nullptr));
-    EXPECT_GE(MallocExtension_GetAllocatedSize(a), 1000);
-    EXPECT_LE(MallocExtension_GetAllocatedSize(a), 5000);
-    EXPECT_GE(MallocExtension_GetEstimatedAllocatedSize(1000), 1000);
   }
 
   free(a);
 }
 
-// Verify that the .cc file and .h file have the same enum values.
-TEST(GetOwnership, EnumValuesEqualForCAndCXX) {
-  EXPECT_EQ(static_cast<int>(MallocExtension::kUnknownOwnership),
-            static_cast<int>(MallocExtension_kUnknownOwnership));
-  EXPECT_EQ(static_cast<int>(MallocExtension::kOwned),
-            static_cast<int>(MallocExtension_kOwned));
-  EXPECT_EQ(static_cast<int>(MallocExtension::kNotOwned),
-            static_cast<int>(MallocExtension_kNotOwned));
-}
-
 TEST(nallocx, SaneBehavior) {
   for (size_t size = 0; size < 64 * 1024; ++size) {
     size_t alloc_size = nallocx(size, 0);
diff --git a/absl/base/internal/malloc_hook.cc b/absl/base/internal/malloc_hook.cc
index 52531c680148..780e8fe3296c 100644
--- a/absl/base/internal/malloc_hook.cc
+++ b/absl/base/internal/malloc_hook.cc
@@ -215,139 +215,101 @@ HookList<MallocHook::MunmapReplacement> munmap_replacement_ = INIT_HOOK_LIST;
 #undef INIT_HOOK_LIST_WITH_VALUE
 #undef INIT_HOOK_LIST
 
-}  // namespace base_internal
-}  // namespace absl
+bool MallocHook::AddNewHook(NewHook hook) { return new_hooks_.Add(hook); }
 
-// These are available as C bindings as well as C++, hence their
-// definition outside the MallocHook class.
-extern "C"
-int MallocHook_AddNewHook(MallocHook_NewHook hook) {
-  return absl::base_internal::new_hooks_.Add(hook);
-}
-
-extern "C"
-int MallocHook_RemoveNewHook(MallocHook_NewHook hook) {
-  return absl::base_internal::new_hooks_.Remove(hook);
-}
+bool MallocHook::RemoveNewHook(NewHook hook) { return new_hooks_.Remove(hook); }
 
-extern "C"
-int MallocHook_AddDeleteHook(MallocHook_DeleteHook hook) {
-  return absl::base_internal::delete_hooks_.Add(hook);
+bool MallocHook::AddDeleteHook(DeleteHook hook) {
+  return delete_hooks_.Add(hook);
 }
 
-extern "C"
-int MallocHook_RemoveDeleteHook(MallocHook_DeleteHook hook) {
-  return absl::base_internal::delete_hooks_.Remove(hook);
+bool MallocHook::RemoveDeleteHook(DeleteHook hook) {
+  return delete_hooks_.Remove(hook);
 }
 
-extern "C" int MallocHook_AddSampledNewHook(MallocHook_SampledNewHook hook) {
-  return absl::base_internal::sampled_new_hooks_.Add(hook);
+bool MallocHook::AddSampledNewHook(SampledNewHook hook) {
+  return sampled_new_hooks_.Add(hook);
 }
 
-extern "C" int MallocHook_RemoveSampledNewHook(MallocHook_SampledNewHook hook) {
-  return absl::base_internal::sampled_new_hooks_.Remove(hook);
+bool MallocHook::RemoveSampledNewHook(SampledNewHook hook) {
+  return sampled_new_hooks_.Remove(hook);
 }
 
-extern "C" int MallocHook_AddSampledDeleteHook(
-    MallocHook_SampledDeleteHook hook) {
-  return absl::base_internal::sampled_delete_hooks_.Add(hook);
+bool MallocHook::AddSampledDeleteHook(SampledDeleteHook hook) {
+  return sampled_delete_hooks_.Add(hook);
 }
 
-extern "C" int MallocHook_RemoveSampledDeleteHook(
-    MallocHook_SampledDeleteHook hook) {
-  return absl::base_internal::sampled_delete_hooks_.Remove(hook);
+bool MallocHook::RemoveSampledDeleteHook(SampledDeleteHook hook) {
+  return sampled_delete_hooks_.Remove(hook);
 }
 
-extern "C"
-int MallocHook_AddPreMmapHook(MallocHook_PreMmapHook hook) {
-  return absl::base_internal::premmap_hooks_.Add(hook);
+bool MallocHook::AddPreMmapHook(PreMmapHook hook) {
+  return premmap_hooks_.Add(hook);
 }
 
-extern "C"
-int MallocHook_RemovePreMmapHook(MallocHook_PreMmapHook hook) {
-  return absl::base_internal::premmap_hooks_.Remove(hook);
+bool MallocHook::RemovePreMmapHook(PreMmapHook hook) {
+  return premmap_hooks_.Remove(hook);
 }
 
-extern "C"
-int MallocHook_SetMmapReplacement(MallocHook_MmapReplacement hook) {
+bool MallocHook::SetMmapReplacement(MmapReplacement hook) {
   // NOTE this is a best effort CHECK. Concurrent sets could succeed since
   // this test is outside of the Add spin lock.
-  ABSL_RAW_CHECK(absl::base_internal::mmap_replacement_.empty(),
+  ABSL_RAW_CHECK(mmap_replacement_.empty(),
                  "Only one MMapReplacement is allowed.");
-  return absl::base_internal::mmap_replacement_.Add(hook);
-}
-
-extern "C"
-int MallocHook_RemoveMmapReplacement(MallocHook_MmapReplacement hook) {
-  return absl::base_internal::mmap_replacement_.Remove(hook);
-}
-
-extern "C"
-int MallocHook_AddMmapHook(MallocHook_MmapHook hook) {
-  return absl::base_internal::mmap_hooks_.Add(hook);
+  return mmap_replacement_.Add(hook);
 }
 
-extern "C"
-int MallocHook_RemoveMmapHook(MallocHook_MmapHook hook) {
-  return absl::base_internal::mmap_hooks_.Remove(hook);
+bool MallocHook::RemoveMmapReplacement(MmapReplacement hook) {
+  return mmap_replacement_.Remove(hook);
 }
 
-extern "C"
-int MallocHook_AddMunmapHook(MallocHook_MunmapHook hook) {
-  return absl::base_internal::munmap_hooks_.Add(hook);
-}
+bool MallocHook::AddMmapHook(MmapHook hook) { return mmap_hooks_.Add(hook); }
 
-extern "C"
-int MallocHook_RemoveMunmapHook(MallocHook_MunmapHook hook) {
-  return absl::base_internal::munmap_hooks_.Remove(hook);
+bool MallocHook::RemoveMmapHook(MmapHook hook) {
+  return mmap_hooks_.Remove(hook);
 }
 
-extern "C"
-int MallocHook_SetMunmapReplacement(MallocHook_MunmapReplacement hook) {
+bool MallocHook::SetMunmapReplacement(MunmapReplacement hook) {
   // NOTE this is a best effort CHECK. Concurrent sets could succeed since
   // this test is outside of the Add spin lock.
-  ABSL_RAW_CHECK(absl::base_internal::munmap_replacement_.empty(),
+  ABSL_RAW_CHECK(munmap_replacement_.empty(),
                  "Only one MunmapReplacement is allowed.");
-  return absl::base_internal::munmap_replacement_.Add(hook);
+  return munmap_replacement_.Add(hook);
 }
 
-extern "C"
-int MallocHook_RemoveMunmapReplacement(MallocHook_MunmapReplacement hook) {
-  return absl::base_internal::munmap_replacement_.Remove(hook);
+bool MallocHook::RemoveMunmapReplacement(MunmapReplacement hook) {
+  return munmap_replacement_.Remove(hook);
 }
 
-extern "C"
-int MallocHook_AddMremapHook(MallocHook_MremapHook hook) {
-  return absl::base_internal::mremap_hooks_.Add(hook);
+bool MallocHook::AddMunmapHook(MunmapHook hook) {
+  return munmap_hooks_.Add(hook);
 }
 
-extern "C"
-int MallocHook_RemoveMremapHook(MallocHook_MremapHook hook) {
-  return absl::base_internal::mremap_hooks_.Remove(hook);
+bool MallocHook::RemoveMunmapHook(MunmapHook hook) {
+  return munmap_hooks_.Remove(hook);
 }
 
-extern "C"
-int MallocHook_AddPreSbrkHook(MallocHook_PreSbrkHook hook) {
-  return absl::base_internal::presbrk_hooks_.Add(hook);
+bool MallocHook::AddMremapHook(MremapHook hook) {
+  return mremap_hooks_.Add(hook);
 }
 
-extern "C"
-int MallocHook_RemovePreSbrkHook(MallocHook_PreSbrkHook hook) {
-  return absl::base_internal::presbrk_hooks_.Remove(hook);
+bool MallocHook::RemoveMremapHook(MremapHook hook) {
+  return mremap_hooks_.Remove(hook);
 }
 
-extern "C"
-int MallocHook_AddSbrkHook(MallocHook_SbrkHook hook) {
-  return absl::base_internal::sbrk_hooks_.Add(hook);
+bool MallocHook::AddPreSbrkHook(PreSbrkHook hook) {
+  return presbrk_hooks_.Add(hook);
 }
 
-extern "C"
-int MallocHook_RemoveSbrkHook(MallocHook_SbrkHook hook) {
-  return absl::base_internal::sbrk_hooks_.Remove(hook);
+bool MallocHook::RemovePreSbrkHook(PreSbrkHook hook) {
+  return presbrk_hooks_.Remove(hook);
 }
 
-namespace absl {
-namespace base_internal {
+bool MallocHook::AddSbrkHook(SbrkHook hook) { return sbrk_hooks_.Add(hook); }
+
+bool MallocHook::RemoveSbrkHook(SbrkHook hook) {
+  return sbrk_hooks_.Remove(hook);
+}
 
 // Note: embedding the function calls inside the traversal of HookList would be
 // very confusing, as it is legal for a hook to remove itself and add other
@@ -501,12 +463,11 @@ static void InitializeInHookCaller() {
   ABSL_INIT_ATTRIBUTE_SECTION_VARS(blink_malloc);
 }
 
-// We can improve behavior/compactness of this function
-// if we pass a generic test function (with a generic arg)
-// into the implementations for get_stack_trace_fn instead of the skip_count.
-extern "C" int MallocHook_GetCallerStackTrace(
-    void** result, int max_depth, int skip_count,
-    MallocHook_GetStackTraceFn get_stack_trace_fn) {
+namespace absl {
+namespace base_internal {
+int MallocHook::GetCallerStackTrace(void** result, int max_depth,
+                                    int skip_count,
+                                    GetStackTraceFn get_stack_trace_fn) {
   if (!ABSL_HAVE_ATTRIBUTE_SECTION) {
     // Fall back to get_stack_trace_fn and good old but fragile frame skip
     // counts.
@@ -524,11 +485,11 @@ extern "C" int MallocHook_GetCallerStackTrace(
   absl::call_once(in_hook_caller_once, InitializeInHookCaller);
   // MallocHook caller determination via InHookCaller works, use it:
   static const int kMaxSkip = 32 + 6 + 3;
-    // Constant tuned to do just one get_stack_trace_fn call below in practice
-    // and not get many frames that we don't actually need:
-    // currently max passed max_depth is 32,
-    // max passed/needed skip_count is 6
-    // and 3 is to account for some hook daisy chaining.
+  // Constant tuned to do just one get_stack_trace_fn call below in practice
+  // and not get many frames that we don't actually need:
+  // currently max passed max_depth is 32,
+  // max passed/needed skip_count is 6
+  // and 3 is to account for some hook daisy chaining.
   static const int kStackSize = kMaxSkip + 1;
   void* stack[kStackSize];
   int depth =
@@ -538,11 +499,11 @@ extern "C" int MallocHook_GetCallerStackTrace(
     return 0;
   for (int i = depth - 1; i >= 0; --i) {  // stack[0] is our immediate caller
     if (InHookCaller(stack[i])) {
-      i += 1;  // skip hook caller frame
+      i += 1;      // skip hook caller frame
       depth -= i;  // correct depth
       if (depth > max_depth) depth = max_depth;
       std::copy(stack + i, stack + i + depth, result);
-      if (depth < max_depth  &&  depth + i == kStackSize) {
+      if (depth < max_depth && depth + i == kStackSize) {
         // get frames for the missing depth
         depth += get_stack_trace_fn(result + depth, max_depth - depth,
                                     1 + kStackSize);
@@ -558,6 +519,8 @@ extern "C" int MallocHook_GetCallerStackTrace(
   // all functions in that section must be inside the same library.
   return 0;
 }
+}  // namespace base_internal
+}  // namespace absl
 
 // On systems where we know how, we override mmap/munmap/mremap/sbrk
 // to provide support for calling the related hooks (in addition,
diff --git a/absl/base/internal/malloc_hook.h b/absl/base/internal/malloc_hook.h
index ed5cf2e65dd6..6b006edac6d4 100644
--- a/absl/base/internal/malloc_hook.h
+++ b/absl/base/internal/malloc_hook.h
@@ -74,24 +74,16 @@ class MallocHook {
   // Object pointer and size are passed in.
   // It may be passed null pointer if the allocator returned null.
   typedef MallocHook_NewHook NewHook;
-  inline static bool AddNewHook(NewHook hook) {
-    return MallocHook_AddNewHook(hook);
-  }
-  inline static bool RemoveNewHook(NewHook hook) {
-    return MallocHook_RemoveNewHook(hook);
-  }
+  static bool AddNewHook(NewHook hook);
+  static bool RemoveNewHook(NewHook hook);
   inline static void InvokeNewHook(const void* ptr, size_t size);
 
   // The DeleteHook is invoked whenever an object is being deallocated.
   // Object pointer is passed in.
   // It may be passed null pointer if the caller is trying to delete null.
   typedef MallocHook_DeleteHook DeleteHook;
-  inline static bool AddDeleteHook(DeleteHook hook) {
-    return MallocHook_AddDeleteHook(hook);
-  }
-  inline static bool RemoveDeleteHook(DeleteHook hook) {
-    return MallocHook_RemoveDeleteHook(hook);
-  }
+  static bool AddDeleteHook(DeleteHook hook);
+  static bool RemoveDeleteHook(DeleteHook hook);
   inline static void InvokeDeleteHook(const void* ptr);
 
   // The SampledNewHook is invoked for some subset of object allocations
@@ -99,20 +91,19 @@ class MallocHook {
   // SampledAlloc has the following fields:
   //  * AllocHandle handle: to be set to an effectively unique value (in this
   //    process) by allocator.
-  //  * size_t allocated_size: space actually used by allocator to host
-  //    the object.
+  //  * size_t allocated_size: space actually used by allocator to host the
+  //    object. Not necessarily equal to the requested size due to alignment
+  //    and other reasons.
+  //  * double weight: the expected number of allocations matching this profile
+  //    that this sample represents.
   //  * int stack_depth and const void* stack: invocation stack for
   //    the allocation.
   // The allocator invoking the hook should record the handle value and later
   // call InvokeSampledDeleteHook() with that value.
   typedef MallocHook_SampledNewHook SampledNewHook;
   typedef MallocHook_SampledAlloc SampledAlloc;
-  inline static bool AddSampledNewHook(SampledNewHook hook) {
-    return MallocHook_AddSampledNewHook(hook);
-  }
-  inline static bool RemoveSampledNewHook(SampledNewHook hook) {
-    return MallocHook_RemoveSampledNewHook(hook);
-  }
+  static bool AddSampledNewHook(SampledNewHook hook);
+  static bool RemoveSampledNewHook(SampledNewHook hook);
   inline static void InvokeSampledNewHook(const SampledAlloc* sampled_alloc);
 
   // The SampledDeleteHook is invoked whenever an object previously chosen
@@ -121,12 +112,8 @@ class MallocHook {
   // InvokeSampledNewHook()-- is passed in.
   typedef MallocHook_SampledDeleteHook SampledDeleteHook;
   typedef MallocHook_AllocHandle AllocHandle;
-  inline static bool AddSampledDeleteHook(SampledDeleteHook hook) {
-    return MallocHook_AddSampledDeleteHook(hook);
-  }
-  inline static bool RemoveSampledDeleteHook(SampledDeleteHook hook) {
-    return MallocHook_RemoveSampledDeleteHook(hook);
-  }
+  static bool AddSampledDeleteHook(SampledDeleteHook hook);
+  static bool RemoveSampledDeleteHook(SampledDeleteHook hook);
   inline static void InvokeSampledDeleteHook(AllocHandle handle);
 
   // The PreMmapHook is invoked with mmap's or mmap64's arguments just
@@ -134,12 +121,8 @@ class MallocHook {
   // in memory limited contexts, to catch allocations that will exceed
   // a memory limit, and take outside actions to increase that limit.
   typedef MallocHook_PreMmapHook PreMmapHook;
-  inline static bool AddPreMmapHook(PreMmapHook hook) {
-    return MallocHook_AddPreMmapHook(hook);
-  }
-  inline static bool RemovePreMmapHook(PreMmapHook hook) {
-    return MallocHook_RemovePreMmapHook(hook);
-  }
+  static bool AddPreMmapHook(PreMmapHook hook);
+  static bool RemovePreMmapHook(PreMmapHook hook);
   inline static void InvokePreMmapHook(const void* start,
                                        size_t size,
                                        int protection,
@@ -159,12 +142,8 @@ class MallocHook {
   // you must call RemoveMmapReplacement before calling SetMmapReplacement
   // again.
   typedef MallocHook_MmapReplacement MmapReplacement;
-  inline static bool SetMmapReplacement(MmapReplacement hook) {
-    return MallocHook_SetMmapReplacement(hook);
-  }
-  inline static bool RemoveMmapReplacement(MmapReplacement hook) {
-    return MallocHook_RemoveMmapReplacement(hook);
-  }
+  static bool SetMmapReplacement(MmapReplacement hook);
+  static bool RemoveMmapReplacement(MmapReplacement hook);
   inline static bool InvokeMmapReplacement(const void* start,
                                            size_t size,
                                            int protection,
@@ -178,12 +157,8 @@ class MallocHook {
   // a region of memory has been just mapped.
   // It may be passed MAP_FAILED if the mmap failed.
   typedef MallocHook_MmapHook MmapHook;
-  inline static bool AddMmapHook(MmapHook hook) {
-    return MallocHook_AddMmapHook(hook);
-  }
-  inline static bool RemoveMmapHook(MmapHook hook) {
-    return MallocHook_RemoveMmapHook(hook);
-  }
+  static bool AddMmapHook(MmapHook hook);
+  static bool RemoveMmapHook(MmapHook hook);
   inline static void InvokeMmapHook(const void* result,
                                     const void* start,
                                     size_t size,
@@ -202,12 +177,8 @@ class MallocHook {
   // MunmapReplacement you must call RemoveMunmapReplacement before
   // calling SetMunmapReplacement again.
   typedef MallocHook_MunmapReplacement MunmapReplacement;
-  inline static bool SetMunmapReplacement(MunmapReplacement hook) {
-    return MallocHook_SetMunmapReplacement(hook);
-  }
-  inline static bool RemoveMunmapReplacement(MunmapReplacement hook) {
-    return MallocHook_RemoveMunmapReplacement(hook);
-  }
+  static bool SetMunmapReplacement(MunmapReplacement hook);
+  static bool RemoveMunmapReplacement(MunmapReplacement hook);
   inline static bool InvokeMunmapReplacement(const void* start,
                                              size_t size,
                                              int* result);
@@ -217,23 +188,15 @@ class MallocHook {
   // TODO(maxim): Rename this to PreMunmapHook for consistency with PreMmapHook
   // and PreSbrkHook.
   typedef MallocHook_MunmapHook MunmapHook;
-  inline static bool AddMunmapHook(MunmapHook hook) {
-    return MallocHook_AddMunmapHook(hook);
-  }
-  inline static bool RemoveMunmapHook(MunmapHook hook) {
-    return MallocHook_RemoveMunmapHook(hook);
-  }
+  static bool AddMunmapHook(MunmapHook hook);
+  static bool RemoveMunmapHook(MunmapHook hook);
   inline static void InvokeMunmapHook(const void* start, size_t size);
 
   // The MremapHook is invoked with mremap's return value and arguments
   // whenever a region of memory has been just remapped.
   typedef MallocHook_MremapHook MremapHook;
-  inline static bool AddMremapHook(MremapHook hook) {
-    return MallocHook_AddMremapHook(hook);
-  }
-  inline static bool RemoveMremapHook(MremapHook hook) {
-    return MallocHook_RemoveMremapHook(hook);
-  }
+  static bool AddMremapHook(MremapHook hook);
+  static bool RemoveMremapHook(MremapHook hook);
   inline static void InvokeMremapHook(const void* result,
                                       const void* old_addr,
                                       size_t old_size,
@@ -248,12 +211,8 @@ class MallocHook {
   // to catch allocations that will exceed the limit and take outside
   // actions to increase such a limit.
   typedef MallocHook_PreSbrkHook PreSbrkHook;
-  inline static bool AddPreSbrkHook(PreSbrkHook hook) {
-    return MallocHook_AddPreSbrkHook(hook);
-  }
-  inline static bool RemovePreSbrkHook(PreSbrkHook hook) {
-    return MallocHook_RemovePreSbrkHook(hook);
-  }
+  static bool AddPreSbrkHook(PreSbrkHook hook);
+  static bool RemovePreSbrkHook(PreSbrkHook hook);
   inline static void InvokePreSbrkHook(ptrdiff_t increment);
 
   // The SbrkHook is invoked with sbrk's result and argument whenever sbrk
@@ -261,12 +220,8 @@ class MallocHook {
   // This is because sbrk(0) is often called to get the top of the memory stack,
   // and is not actually a memory-allocation call.
   typedef MallocHook_SbrkHook SbrkHook;
-  inline static bool AddSbrkHook(SbrkHook hook) {
-    return MallocHook_AddSbrkHook(hook);
-  }
-  inline static bool RemoveSbrkHook(SbrkHook hook) {
-    return MallocHook_RemoveSbrkHook(hook);
-  }
+  static bool AddSbrkHook(SbrkHook hook);
+  static bool RemoveSbrkHook(SbrkHook hook);
   inline static void InvokeSbrkHook(const void* result, ptrdiff_t increment);
 
   // Pointer to a absl::GetStackTrace implementation, following the API in
@@ -280,12 +235,8 @@ class MallocHook {
   // is not available.
   // Stack trace is filled into *result up to the size of max_depth.
   // The actual number of stack frames filled is returned.
-  inline static int GetCallerStackTrace(void** result, int max_depth,
-                                        int skip_count,
-                                        GetStackTraceFn get_stack_trace_fn) {
-    return MallocHook_GetCallerStackTrace(result, max_depth, skip_count,
-                                          get_stack_trace_fn);
-  }
+  static int GetCallerStackTrace(void** result, int max_depth, int skip_count,
+                                 GetStackTraceFn get_stack_trace_fn);
 
 #if ABSL_HAVE_MMAP
   // Unhooked versions of mmap() and munmap().   These should be used
diff --git a/absl/base/internal/malloc_hook_c.h b/absl/base/internal/malloc_hook_c.h
index 03b84ca627d2..7255ddc22900 100644
--- a/absl/base/internal/malloc_hook_c.h
+++ b/absl/base/internal/malloc_hook_c.h
@@ -29,100 +29,38 @@
 extern "C" {
 #endif  /* __cplusplus */
 
-/* Get the current stack trace.  Try to skip all routines up to and
- * including the caller of MallocHook::Invoke*.
- * Use "skip_count" (similarly to absl::GetStackTrace from stacktrace.h)
- * as a hint about how many routines to skip if better information
- * is not available.
- */
 typedef int (*MallocHook_GetStackTraceFn)(void**, int, int);
-int MallocHook_GetCallerStackTrace(void** result, int max_depth, int skip_count,
-                                   MallocHook_GetStackTraceFn fn);
-
-/* All the MallocHook_{Add,Remove}*Hook functions below return 1 on success
- * and 0 on failure.
- */
-
 typedef void (*MallocHook_NewHook)(const void* ptr, size_t size);
-int MallocHook_AddNewHook(MallocHook_NewHook hook);
-int MallocHook_RemoveNewHook(MallocHook_NewHook hook);
-
 typedef void (*MallocHook_DeleteHook)(const void* ptr);
-int MallocHook_AddDeleteHook(MallocHook_DeleteHook hook);
-int MallocHook_RemoveDeleteHook(MallocHook_DeleteHook hook);
-
 typedef int64_t MallocHook_AllocHandle;
 typedef struct {
   /* See malloc_hook.h  for documentation for this struct. */
   MallocHook_AllocHandle handle;
   size_t allocated_size;
+  double weight;
   int stack_depth;
   const void* stack;
 } MallocHook_SampledAlloc;
 typedef void (*MallocHook_SampledNewHook)(
     const MallocHook_SampledAlloc* sampled_alloc);
-int MallocHook_AddSampledNewHook(MallocHook_SampledNewHook hook);
-int MallocHook_RemoveSampledNewHook(MallocHook_SampledNewHook hook);
-
 typedef void (*MallocHook_SampledDeleteHook)(MallocHook_AllocHandle handle);
-int MallocHook_AddSampledDeleteHook(MallocHook_SampledDeleteHook hook);
-int MallocHook_RemoveSampledDeleteHook(MallocHook_SampledDeleteHook hook);
-
-typedef void (*MallocHook_PreMmapHook)(const void *start,
-                                       size_t size,
-                                       int protection,
-                                       int flags,
-                                       int fd,
+typedef void (*MallocHook_PreMmapHook)(const void* start, size_t size,
+                                       int protection, int flags, int fd,
                                        off_t offset);
-int MallocHook_AddPreMmapHook(MallocHook_PreMmapHook hook);
-int MallocHook_RemovePreMmapHook(MallocHook_PreMmapHook hook);
-
-typedef void (*MallocHook_MmapHook)(const void* result,
-                                    const void* start,
-                                    size_t size,
-                                    int protection,
-                                    int flags,
-                                    int fd,
-                                    off_t offset);
-int MallocHook_AddMmapHook(MallocHook_MmapHook hook);
-int MallocHook_RemoveMmapHook(MallocHook_MmapHook hook);
-
-typedef int (*MallocHook_MmapReplacement)(const void* start,
-                                          size_t size,
-                                          int protection,
-                                          int flags,
-                                          int fd,
-                                          off_t offset,
-                                          void** result);
-int MallocHook_SetMmapReplacement(MallocHook_MmapReplacement hook);
-int MallocHook_RemoveMmapReplacement(MallocHook_MmapReplacement hook);
-
+typedef void (*MallocHook_MmapHook)(const void* result, const void* start,
+                                    size_t size, int protection, int flags,
+                                    int fd, off_t offset);
+typedef int (*MallocHook_MmapReplacement)(const void* start, size_t size,
+                                          int protection, int flags, int fd,
+                                          off_t offset, void** result);
 typedef void (*MallocHook_MunmapHook)(const void* start, size_t size);
-int MallocHook_AddMunmapHook(MallocHook_MunmapHook hook);
-int MallocHook_RemoveMunmapHook(MallocHook_MunmapHook hook);
-
-typedef int (*MallocHook_MunmapReplacement)(const void* start,
-                                            size_t size,
+typedef int (*MallocHook_MunmapReplacement)(const void* start, size_t size,
                                             int* result);
-int MallocHook_SetMunmapReplacement(MallocHook_MunmapReplacement hook);
-int MallocHook_RemoveMunmapReplacement(MallocHook_MunmapReplacement hook);
-
-typedef void (*MallocHook_MremapHook)(const void* result,
-                                      const void* old_addr,
-                                      size_t old_size,
-                                      size_t new_size,
-                                      int flags,
-                                      const void* new_addr);
-int MallocHook_AddMremapHook(MallocHook_MremapHook hook);
-int MallocHook_RemoveMremapHook(MallocHook_MremapHook hook);
-
+typedef void (*MallocHook_MremapHook)(const void* result, const void* old_addr,
+                                      size_t old_size, size_t new_size,
+                                      int flags, const void* new_addr);
 typedef void (*MallocHook_PreSbrkHook)(ptrdiff_t increment);
-int MallocHook_AddPreSbrkHook(MallocHook_PreSbrkHook hook);
-int MallocHook_RemovePreSbrkHook(MallocHook_PreSbrkHook hook);
-
 typedef void (*MallocHook_SbrkHook)(const void* result, ptrdiff_t increment);
-int MallocHook_AddSbrkHook(MallocHook_SbrkHook hook);
-int MallocHook_RemoveSbrkHook(MallocHook_SbrkHook hook);
 
 #ifdef __cplusplus
 }  /* extern "C" */
diff --git a/absl/base/internal/per_thread_tls.h b/absl/base/internal/per_thread_tls.h
index 7397451031b9..2428bdc1238e 100644
--- a/absl/base/internal/per_thread_tls.h
+++ b/absl/base/internal/per_thread_tls.h
@@ -26,7 +26,7 @@
 //
 // Microsoft C supports thread-local storage.
 // GCC supports it if the appropriate version of glibc is available,
-// which the programme can indicate by defining ABSL_HAVE_TLS
+// which the programmer can indicate by defining ABSL_HAVE_TLS
 
 #include "absl/base/port.h"  // For ABSL_HAVE_TLS
 
diff --git a/absl/base/internal/raw_logging.cc b/absl/base/internal/raw_logging.cc
index 301b108c07e9..86e34d458f4e 100644
--- a/absl/base/internal/raw_logging.cc
+++ b/absl/base/internal/raw_logging.cc
@@ -22,7 +22,7 @@
 
 #include "absl/base/config.h"
 #include "absl/base/internal/atomic_hook.h"
-#include "absl/base/internal/log_severity.h"
+#include "absl/base/log_severity.h"
 
 // We know how to perform low-level writes to stderr in POSIX and Windows.  For
 // these platforms, we define the token ABSL_LOW_LEVEL_WRITE_SUPPORTED.
diff --git a/absl/base/internal/raw_logging.h b/absl/base/internal/raw_logging.h
index 568d2afce10a..1b2a44b7a7da 100644
--- a/absl/base/internal/raw_logging.h
+++ b/absl/base/internal/raw_logging.h
@@ -20,7 +20,7 @@
 #define ABSL_BASE_INTERNAL_RAW_LOGGING_H_
 
 #include "absl/base/attributes.h"
-#include "absl/base/internal/log_severity.h"
+#include "absl/base/log_severity.h"
 #include "absl/base/macros.h"
 #include "absl/base/port.h"
 
diff --git a/absl/base/internal/spinlock.h b/absl/base/internal/spinlock.h
index a9037e3ed05c..212abc669e62 100644
--- a/absl/base/internal/spinlock.h
+++ b/absl/base/internal/spinlock.h
@@ -227,7 +227,7 @@ inline uint32_t SpinLock::TryLockInternal(uint32_t lock_value,
           kSpinLockHeld | lock_value | wait_cycles | sched_disabled_bit,
           std::memory_order_acquire, std::memory_order_relaxed)) {
   } else {
-    base_internal::SchedulingGuard::EnableRescheduling(sched_disabled_bit);
+    base_internal::SchedulingGuard::EnableRescheduling(sched_disabled_bit != 0);
   }
 
   return lock_value;
diff --git a/absl/base/internal/thread_identity.h b/absl/base/internal/thread_identity.h
index 914d5da7ef40..a51722f9d828 100644
--- a/absl/base/internal/thread_identity.h
+++ b/absl/base/internal/thread_identity.h
@@ -61,7 +61,7 @@ struct PerThreadSynch {
 
   PerThreadSynch *next;  // Circular waiter queue; initialized to 0.
   PerThreadSynch *skip;  // If non-zero, all entries in Mutex queue
-                         // upto and including "skip" have same
+                         // up to and including "skip" have same
                          // condition as this, and will be woken later
   bool may_skip;         // if false while on mutex queue, a mutex unlocker
                          // is using this PerThreadSynch as a terminator.  Its
diff --git a/absl/base/internal/log_severity.h b/absl/base/log_severity.h
index deaf6a578925..deaf6a578925 100644
--- a/absl/base/internal/log_severity.h
+++ b/absl/base/log_severity.h
diff --git a/absl/base/macros.h b/absl/base/macros.h
index d41408727731..5ae0f05bf8c1 100644
--- a/absl/base/macros.h
+++ b/absl/base/macros.h
@@ -146,7 +146,7 @@ enum LinkerInitialized {
 // Every usage of a deprecated entity will trigger a warning when compiled with
 // clang's `-Wdeprecated-declarations` option. This option is turned off by
 // default, but the warnings will be reported by clang-tidy.
-#if defined(__clang__) && __cplusplus >= 201103L && defined(__has_warning)
+#if defined(__clang__) && __cplusplus >= 201103L
 #define ABSL_DEPRECATED(message) __attribute__((deprecated(message)))
 #endif