- ed0ba496fe01eb8edfa86beade8a37768e7c12ef Updates the API for Exception Safety testing to use build... by Abseil Team <absl-team@google.com>

  - c4b7a4e517c9404932c45f2f9f92eb7dc694e45d Internal change by Abseil Team <absl-team@google.com>
  - 76c78ed9385f65d881511645446e0bb8ababf6ec Add missing ABSL_PREDICT_FALSE to one of FixedArray::at()... by Abseil Team <absl-team@google.com>
  - 1204fb1c46f007dd9dfb7d9abf3e96c58835d193 Internal change. by Greg Falcon <gfalcon@google.com>
  - f1f47c98a026bc5e425ae83ff4a2eb391bbd3d9b Add internal-only functionality to examine the stack, to ... by Derek Mauro <dmauro@google.com>
  - 30d63097cd268d912f917526f6511005580465c4 fix typo by Abseil Team <absl-team@google.com>
  - 942d7efa6cf54cd248ca57dcaf3c245188b52a76 Remove unnecessary semicolons from comment examples. by Abseil Team <absl-team@google.com>
  - 7db0669cf23a06d934d3ed8c76aee4e4e23b7e04 Remove malloc_hook and malloc_extension from our internal... by Greg Falcon <gfalcon@google.com>
  - 0190f1063d101b1ded355019df2e1d325931f6c7 Make the maximum length of a string view equal difference... by Abseil Team <absl-team@google.com>
  - c8ae37cbce29449b02115a0ebd435ddc3d7ab062 Add namespace qualification. by Shaindel Schwartz <shaindel@google.com>
  - ff70afe2e6e3dd39f51ce9829e3e1f18231bf4d7 Fix internal/direct_mmap.h for non-linux builds. by Greg Falcon <gfalcon@google.com>

GitOrigin-RevId: ed0ba496fe01eb8edfa86beade8a37768e7c12ef
Change-Id: I7595ee3480d1d6724fd3797c15ba9d9be0d17e62

35 files changed, 830 insertions, 2600 deletions

diff --git a/absl/base/BUILD.bazel b/absl/base/BUILD.bazel
index 707f4882..f9aac5a5 100644
--- a/absl/base/BUILD.bazel
+++ b/absl/base/BUILD.bazel
@@ -78,41 +78,15 @@ cc_library(
 )
 
 cc_library(
-    name = "malloc_extension",
-    srcs = ["internal/malloc_extension.cc"],
-    hdrs = [
-        "internal/malloc_extension.h",
-    ],
-    copts = ABSL_DEFAULT_COPTS,
-    visibility = [
-        "//absl:__subpackages__",
-    ],
-    deps = [
-        ":core_headers",
-        ":dynamic_annotations",
-    ],
-)
-
-# malloc_extension feels like it wants to be folded into this target, but
-# malloc_internal gets special build treatment to compile at -O3, so these
-# need to stay separate.
-cc_library(
     name = "malloc_internal",
     srcs = [
         "internal/low_level_alloc.cc",
-        "internal/malloc_hook.cc",
-        "internal/malloc_hook_mmap_linux.inc",
     ],
     hdrs = [
         "internal/direct_mmap.h",
         "internal/low_level_alloc.h",
-        "internal/malloc_hook.h",
-        "internal/malloc_hook_c.h",
     ],
     copts = ABSL_DEFAULT_COPTS,
-    textual_hdrs = [
-        "internal/malloc_hook_invoke.h",
-    ],
     visibility = [
         "//absl:__subpackages__",
     ],
@@ -419,26 +393,3 @@ cc_test(
         "@com_google_googletest//:gtest_main",
     ],
 )
-
-cc_test(
-    name = "malloc_extension_system_malloc_test",
-    size = "small",
-    srcs = ["internal/malloc_extension_test.cc"],
-    copts = select({
-        "//absl:windows": [
-            "/DABSL_MALLOC_EXTENSION_TEST_ALLOW_MISSING_EXTENSION=1",
-        ],
-        "//conditions:default": [
-            "-DABSL_MALLOC_EXTENSION_TEST_ALLOW_MISSING_EXTENSION=1",
-        ],
-    }) + ABSL_TEST_COPTS,
-    features = [
-        # This test can't be run under lsan because the test requires system
-        # malloc, and lsan provides a competing malloc implementation.
-        "-leak_sanitize",
-    ],
-    deps = [
-        ":malloc_extension",
-        "@com_google_googletest//:gtest_main",
-    ],
-)
diff --git a/absl/base/CMakeLists.txt b/absl/base/CMakeLists.txt
index ced81b6b..329a3d05 100644
--- a/absl/base/CMakeLists.txt
+++ b/absl/base/CMakeLists.txt
@@ -41,10 +41,6 @@ list(APPEND BASE_INTERNAL_HEADERS
   "internal/inline_variable.h"
   "internal/low_level_alloc.h"
   "internal/low_level_scheduling.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"
@@ -69,7 +65,6 @@ list(APPEND BASE_SRC
   "internal/thread_identity.cc"
   "internal/unscaledcycleclock.cc"
   "internal/low_level_alloc.cc"
-  "internal/malloc_hook.cc"
   ${BASE_PUBLIC_HEADERS}
   ${BASE_INTERNAL_HEADERS}
 )
@@ -86,21 +81,6 @@ absl_library(
     base
 )
 
-# malloc extension library
-set(MALLOC_EXTENSION_SRC "internal/malloc_extension.cc")
-set(MALLOC_EXTENSION_PUBLIC_LIBRARIES absl::base)
-
-absl_library(
-  TARGET
-    absl_malloc_extension
-  SOURCES
-    ${MALLOC_EXTENSION_SRC}
-  PUBLIC_LIBRARIES
-    ${MALLOC_EXTENSION_PUBLIC_LIBRARIES}
-  EXPORT_NAME
-    malloc_extension
-)
-
 # throw delegate library
 set(THROW_DELEGATE_SRC "internal/throw_delegate.cc")
 
@@ -165,8 +145,6 @@ absl_library(
 # malloc_internal library
 list(APPEND MALLOC_INTERNAL_SRC
   "internal/low_level_alloc.cc"
-  "internal/malloc_hook.cc"
-  "internal/malloc_hook_mmap_linux.inc"
 )
 
 absl_library(
@@ -378,23 +356,3 @@ absl_test(
   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")
-set(MALLOC_EXTENSION_SYSTEM_MALLOC_TEST_PUBLIC_LIBRARIES absl::base absl_malloc_extension)
-set(MALLOC_EXTENSION_SYSTEM_MALLOC_TEST_PRIVATE_COMPILE_FLAGS "-DABSL_MALLOC_EXTENSION_TEST_ALLOW_MISSING_EXTENSION=1")
-
-absl_test(
-  TARGET
-    absl_malloc_extension_system_malloc_test
-  SOURCES
-    ${MALLOC_EXTENSION_SYSTEM_MALLOC_TEST_SRC}
-  PUBLIC_LIBRARIES
-    ${MALLOC_EXTENSION_SYSTEM_MALLOC_TEST_PUBLIC_LIBRARIES}
-  PRIVATE_COMPILE_FLAGS
-    ${MALLOC_EXTENSION_SYSTEM_MALLOC_TEST_PRIVATE_COMPILE_FLAGS}
-)
-
-
-
-
diff --git a/absl/base/casts.h b/absl/base/casts.h
index 266c4a0a..3096d4c1 100644
--- a/absl/base/casts.h
+++ b/absl/base/casts.h
@@ -20,7 +20,6 @@
 // This header file defines casting templates to fit use cases not covered by
 // the standard casts provided in the C++ standard. As with all cast operations,
 // use these with caution and only if alternatives do not exist.
-//
 
 #ifndef ABSL_BASE_CASTS_H_
 #define ABSL_BASE_CASTS_H_
@@ -122,7 +121,7 @@ inline To implicit_cast(typename absl::internal::identity_t<To> to) {
 // object in memory has one type, and a program accesses it with a different
 // type, the result is undefined behavior for most values of "different type".
 //
-// Such casting results is type punning: holding an object in memory of one type
+// Such casting results in type punning: holding an object in memory of one type
 // and reading its bits back using a different type. A `bit_cast()` avoids this
 // issue by implementating its casts using `memcpy()`, which avoids introducing
 // this undefined behavior.
diff --git a/absl/base/exception_safety_testing_test.cc b/absl/base/exception_safety_testing_test.cc
index 9c52f249..041d780f 100644
--- a/absl/base/exception_safety_testing_test.cc
+++ b/absl/base/exception_safety_testing_test.cc
@@ -402,29 +402,158 @@ TEST_F(ThrowingAllocatorTest, InList) {
   for (int i = 0; i < 20; ++i) l.pop_front();
 }
 
-struct CallOperator {
-  template <typename T>
-  void operator()(T* t) const {
-    (*t)();
+template <typename TesterInstance, typename = void>
+struct NullaryTestValidator : public std::false_type {};
+
+template <typename TesterInstance>
+struct NullaryTestValidator<
+    TesterInstance,
+    absl::void_t<decltype(std::declval<TesterInstance>().Test())>>
+    : public std::true_type {};
+
+template <typename TesterInstance>
+bool HasNullaryTest(const TesterInstance&) {
+  return NullaryTestValidator<TesterInstance>::value;
+}
+
+void DummyOp(void*) {}
+
+template <typename TesterInstance, typename = void>
+struct UnaryTestValidator : public std::false_type {};
+
+template <typename TesterInstance>
+struct UnaryTestValidator<
+    TesterInstance,
+    absl::void_t<decltype(std::declval<TesterInstance>().Test(DummyOp))>>
+    : public std::true_type {};
+
+template <typename TesterInstance>
+bool HasUnaryTest(const TesterInstance&) {
+  return UnaryTestValidator<TesterInstance>::value;
+}
+
+TEST(ExceptionSafetyTesterTest, IncompleteTypesAreNotTestable) {
+  using T = exceptions_internal::UninitializedT;
+  auto op = [](T* t) {};
+  auto inv = [](T*) { return testing::AssertionSuccess(); };
+  auto fac = []() { return absl::make_unique<T>(); };
+
+  // Test that providing operation and inveriants still does not allow for the
+  // the invocation of .Test() and .Test(op) because it lacks a factory
+  auto without_fac =
+      absl::MakeExceptionSafetyTester().WithOperation(op).WithInvariants(
+          inv, absl::strong_guarantee);
+  EXPECT_FALSE(HasNullaryTest(without_fac));
+  EXPECT_FALSE(HasUnaryTest(without_fac));
+
+  // Test that providing invariants and factory allows the invocation of
+  // .Test(op) but does not allow for .Test() because it lacks an operation
+  auto without_op = absl::MakeExceptionSafetyTester()
+                        .WithInvariants(inv, absl::strong_guarantee)
+                        .WithFactory(fac);
+  EXPECT_FALSE(HasNullaryTest(without_op));
+  EXPECT_TRUE(HasUnaryTest(without_op));
+
+  // Test that providing operation and factory still does not allow for the
+  // the invocation of .Test() and .Test(op) because it lacks invariants
+  auto without_inv =
+      absl::MakeExceptionSafetyTester().WithOperation(op).WithFactory(fac);
+  EXPECT_FALSE(HasNullaryTest(without_inv));
+  EXPECT_FALSE(HasUnaryTest(without_inv));
+}
+
+struct ExampleStruct {};
+
+std::unique_ptr<ExampleStruct> ExampleFunctionFactory() {
+  return absl::make_unique<ExampleStruct>();
+}
+
+void ExampleFunctionOperation(ExampleStruct*) {}
+
+testing::AssertionResult ExampleFunctionInvariant(ExampleStruct*) {
+  return testing::AssertionSuccess();
+}
+
+struct {
+  std::unique_ptr<ExampleStruct> operator()() const {
+    return ExampleFunctionFactory();
+  }
+} example_struct_factory;
+
+struct {
+  void operator()(ExampleStruct*) const {}
+} example_struct_operation;
+
+struct {
+  testing::AssertionResult operator()(ExampleStruct* example_struct) const {
+    return ExampleFunctionInvariant(example_struct);
   }
+} example_struct_invariant;
+
+auto example_lambda_factory = []() { return ExampleFunctionFactory(); };
+
+auto example_lambda_operation = [](ExampleStruct*) {};
+
+auto example_lambda_invariant = [](ExampleStruct* example_struct) {
+  return ExampleFunctionInvariant(example_struct);
 };
 
+// Testing that function references, pointers, structs with operator() and
+// lambdas can all be used with ExceptionSafetyTester
+TEST(ExceptionSafetyTesterTest, MixedFunctionTypes) {
+  // function reference
+  EXPECT_TRUE(absl::MakeExceptionSafetyTester()
+                  .WithFactory(ExampleFunctionFactory)
+                  .WithOperation(ExampleFunctionOperation)
+                  .WithInvariants(ExampleFunctionInvariant)
+                  .Test());
+
+  // function pointer
+  EXPECT_TRUE(absl::MakeExceptionSafetyTester()
+                  .WithFactory(&ExampleFunctionFactory)
+                  .WithOperation(&ExampleFunctionOperation)
+                  .WithInvariants(&ExampleFunctionInvariant)
+                  .Test());
+
+  // struct
+  EXPECT_TRUE(absl::MakeExceptionSafetyTester()
+                  .WithFactory(example_struct_factory)
+                  .WithOperation(example_struct_operation)
+                  .WithInvariants(example_struct_invariant)
+                  .Test());
+
+  // lambda
+  EXPECT_TRUE(absl::MakeExceptionSafetyTester()
+                  .WithFactory(example_lambda_factory)
+                  .WithOperation(example_lambda_operation)
+                  .WithInvariants(example_lambda_invariant)
+                  .Test());
+}
+
 struct NonNegative {
-  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;
-  }
   bool operator==(const NonNegative& other) const { return i == other.i; }
-
   int i;
 };
 
-template <typename T>
-struct DefaultFactory {
-  std::unique_ptr<T> operator()() const { return absl::make_unique<T>(); }
-};
+testing::AssertionResult CheckNonNegativeInvariants(NonNegative* g) {
+  if (g->i >= 0) {
+    return testing::AssertionSuccess();
+  }
+  return testing::AssertionFailure()
+         << "i should be non-negative but is " << g->i;
+}
+
+struct {
+  template <typename T>
+  void operator()(T* t) const {
+    (*t)();
+  }
+} invoker;
+
+auto tester =
+    absl::MakeExceptionSafetyTester().WithOperation(invoker).WithInvariants(
+        CheckNonNegativeInvariants);
+auto strong_tester = tester.WithInvariants(absl::strong_guarantee);
 
 struct FailsBasicGuarantee : public NonNegative {
   void operator()() {
@@ -435,8 +564,7 @@ struct FailsBasicGuarantee : public NonNegative {
 };
 
 TEST(ExceptionCheckTest, BasicGuaranteeFailure) {
-  EXPECT_FALSE(TestExceptionSafety(DefaultFactory<FailsBasicGuarantee>(),
-                                   CallOperator{}));
+  EXPECT_FALSE(tester.WithInitialValue(FailsBasicGuarantee{}).Test());
 }
 
 struct FollowsBasicGuarantee : public NonNegative {
@@ -447,22 +575,12 @@ struct FollowsBasicGuarantee : public NonNegative {
 };
 
 TEST(ExceptionCheckTest, BasicGuarantee) {
-  EXPECT_TRUE(TestExceptionSafety(DefaultFactory<FollowsBasicGuarantee>(),
-                                  CallOperator{}));
+  EXPECT_TRUE(tester.WithInitialValue(FollowsBasicGuarantee{}).Test());
 }
 
 TEST(ExceptionCheckTest, StrongGuaranteeFailure) {
-  {
-    DefaultFactory<FailsBasicGuarantee> factory;
-    EXPECT_FALSE(
-        TestExceptionSafety(factory, CallOperator{}, StrongGuarantee(factory)));
-  }
-
-  {
-    DefaultFactory<FollowsBasicGuarantee> factory;
-    EXPECT_FALSE(
-        TestExceptionSafety(factory, CallOperator{}, StrongGuarantee(factory)));
-  }
+  EXPECT_FALSE(strong_tester.WithInitialValue(FailsBasicGuarantee{}).Test());
+  EXPECT_FALSE(strong_tester.WithInitialValue(FollowsBasicGuarantee{}).Test());
 }
 
 struct BasicGuaranteeWithExtraInvariants : public NonNegative {
@@ -479,20 +597,21 @@ struct BasicGuaranteeWithExtraInvariants : public NonNegative {
 constexpr int BasicGuaranteeWithExtraInvariants::kExceptionSentinel;
 
 TEST(ExceptionCheckTest, BasicGuaranteeWithInvariants) {
-  DefaultFactory<BasicGuaranteeWithExtraInvariants> factory;
-
-  EXPECT_TRUE(TestExceptionSafety(factory, CallOperator{}));
-
-  EXPECT_TRUE(TestExceptionSafety(
-      factory, CallOperator{}, [](BasicGuaranteeWithExtraInvariants* w) {
-        if (w->i == BasicGuaranteeWithExtraInvariants::kExceptionSentinel) {
-          return testing::AssertionSuccess();
-        }
-        return testing::AssertionFailure()
-               << "i should be "
-               << BasicGuaranteeWithExtraInvariants::kExceptionSentinel
-               << ", but is " << w->i;
-      }));
+  auto tester_with_val =
+      tester.WithInitialValue(BasicGuaranteeWithExtraInvariants{});
+  EXPECT_TRUE(tester_with_val.Test());
+  EXPECT_TRUE(
+      tester_with_val
+          .WithInvariants([](BasicGuaranteeWithExtraInvariants* w) {
+            if (w->i == BasicGuaranteeWithExtraInvariants::kExceptionSentinel) {
+              return testing::AssertionSuccess();
+            }
+            return testing::AssertionFailure()
+                   << "i should be "
+                   << BasicGuaranteeWithExtraInvariants::kExceptionSentinel
+                   << ", but is " << w->i;
+          })
+          .Test());
 }
 
 struct FollowsStrongGuarantee : public NonNegative {
@@ -500,10 +619,8 @@ struct FollowsStrongGuarantee : public NonNegative {
 };
 
 TEST(ExceptionCheckTest, StrongGuarantee) {
-  DefaultFactory<FollowsStrongGuarantee> factory;
-  EXPECT_TRUE(TestExceptionSafety(factory, CallOperator{}));
-  EXPECT_TRUE(
-      TestExceptionSafety(factory, CallOperator{}, StrongGuarantee(factory)));
+  EXPECT_TRUE(tester.WithInitialValue(FollowsStrongGuarantee{}).Test());
+  EXPECT_TRUE(strong_tester.WithInitialValue(FollowsStrongGuarantee{}).Test());
 }
 
 struct HasReset : public NonNegative {
@@ -514,38 +631,36 @@ struct HasReset : public NonNegative {
   }
 
   void reset() { i = 0; }
-
-  friend bool AbslCheckInvariants(HasReset* h,
-                                  absl::InternalAbslNamespaceFinder) {
-    h->reset();
-    return h->i == 0;
-  }
 };
 
+testing::AssertionResult CheckHasResetInvariants(HasReset* h) {
+  h->reset();
+  return testing::AssertionResult(h->i == 0);
+}
+
 TEST(ExceptionCheckTest, ModifyingChecker) {
-  {
-    DefaultFactory<FollowsBasicGuarantee> factory;
-    EXPECT_FALSE(TestExceptionSafety(
-        factory, CallOperator{},
-        [](FollowsBasicGuarantee* g) {
-          g->i = 1000;
-          return true;
-        },
-        [](FollowsBasicGuarantee* g) { return g->i == 1000; }));
-  }
-  {
-    DefaultFactory<FollowsStrongGuarantee> factory;
-    EXPECT_TRUE(TestExceptionSafety(factory, CallOperator{},
-                                    [](FollowsStrongGuarantee* g) {
-                                      ++g->i;
-                                      return true;
-                                    },
-                                    StrongGuarantee(factory)));
-  }
-  {
-    DefaultFactory<HasReset> factory;
-    EXPECT_TRUE(TestExceptionSafety(factory, CallOperator{}));
-  }
+  auto set_to_1000 = [](FollowsBasicGuarantee* g) {
+    g->i = 1000;
+    return testing::AssertionSuccess();
+  };
+  auto is_1000 = [](FollowsBasicGuarantee* g) {
+    return testing::AssertionResult(g->i == 1000);
+  };
+  auto increment = [](FollowsStrongGuarantee* g) {
+    ++g->i;
+    return testing::AssertionSuccess();
+  };
+
+  EXPECT_FALSE(tester.WithInitialValue(FollowsBasicGuarantee{})
+                   .WithInvariants(set_to_1000, is_1000)
+                   .Test());
+  EXPECT_TRUE(strong_tester.WithInitialValue(FollowsStrongGuarantee{})
+                  .WithInvariants(increment)
+                  .Test());
+  EXPECT_TRUE(absl::MakeExceptionSafetyTester()
+                  .WithInitialValue(HasReset{})
+                  .WithInvariants(CheckHasResetInvariants)
+                  .Test(invoker));
 }
 
 struct NonCopyable : public NonNegative {
@@ -556,10 +671,9 @@ struct NonCopyable : public NonNegative {
 };
 
 TEST(ExceptionCheckTest, NonCopyable) {
-  DefaultFactory<NonCopyable> factory;
-  EXPECT_TRUE(TestExceptionSafety(factory, CallOperator{}));
-  EXPECT_TRUE(
-      TestExceptionSafety(factory, CallOperator{}, StrongGuarantee(factory)));
+  auto factory = []() { return absl::make_unique<NonCopyable>(); };
+  EXPECT_TRUE(tester.WithFactory(factory).Test());
+  EXPECT_TRUE(strong_tester.WithFactory(factory).Test());
 }
 
 struct NonEqualityComparable : public NonNegative {
@@ -574,15 +688,15 @@ struct NonEqualityComparable : public NonNegative {
 };
 
 TEST(ExceptionCheckTest, NonEqualityComparable) {
-  DefaultFactory<NonEqualityComparable> factory;
-  auto comp = [](const NonEqualityComparable& a,
-                 const NonEqualityComparable& b) { return a.i == b.i; };
-  EXPECT_TRUE(TestExceptionSafety(factory, CallOperator{}));
-  EXPECT_TRUE(TestExceptionSafety(factory, CallOperator{},
-                                  absl::StrongGuarantee(factory, comp)));
-  EXPECT_FALSE(TestExceptionSafety(
-      factory, [&](NonEqualityComparable* n) { n->ModifyOnThrow(); },
-      absl::StrongGuarantee(factory, comp)));
+  auto nec_is_strong = [](NonEqualityComparable* nec) {
+    return testing::AssertionResult(nec->i == NonEqualityComparable().i);
+  };
+  auto strong_nec_tester = tester.WithInitialValue(NonEqualityComparable{})
+                               .WithInvariants(nec_is_strong);
+
+  EXPECT_TRUE(strong_nec_tester.Test());
+  EXPECT_FALSE(strong_nec_tester.Test(
+      [](NonEqualityComparable* n) { n->ModifyOnThrow(); }));
 }
 
 template <typename T>
@@ -604,28 +718,32 @@ struct ExhaustivenessTester {
     return true;
   }
 
-  friend testing::AssertionResult AbslCheckInvariants(
-      ExhaustivenessTester*, absl::InternalAbslNamespaceFinder) {
+  static unsigned char successes;
+};
+
+struct {
+  template <typename T>
+  testing::AssertionResult operator()(ExhaustivenessTester<T>*) const {
     return testing::AssertionSuccess();
   }
+} CheckExhaustivenessTesterInvariants;
 
-  static unsigned char successes;
-};
 template <typename T>
 unsigned char ExhaustivenessTester<T>::successes = 0;
 
 TEST(ExceptionCheckTest, Exhaustiveness) {
-  DefaultFactory<ExhaustivenessTester<int>> int_factory;
-  EXPECT_TRUE(TestExceptionSafety(int_factory, CallOperator{}));
-  EXPECT_EQ(ExhaustivenessTester<int>::successes, 0xF);
+  auto exhaust_tester = absl::MakeExceptionSafetyTester()
+                            .WithInvariants(CheckExhaustivenessTesterInvariants)
+                            .WithOperation(invoker);
 
-  DefaultFactory<ExhaustivenessTester<ThrowingValue<>>> bomb_factory;
-  EXPECT_TRUE(TestExceptionSafety(bomb_factory, CallOperator{}));
-  EXPECT_EQ(ExhaustivenessTester<ThrowingValue<>>::successes, 0xF);
+  EXPECT_TRUE(
+      exhaust_tester.WithInitialValue(ExhaustivenessTester<int>{}).Test());
+  EXPECT_EQ(ExhaustivenessTester<int>::successes, 0xF);
 
-  ExhaustivenessTester<ThrowingValue<>>::successes = 0;
-  EXPECT_TRUE(TestExceptionSafety(bomb_factory, CallOperator{},
-                                  StrongGuarantee(bomb_factory)));
+  EXPECT_TRUE(
+      exhaust_tester.WithInitialValue(ExhaustivenessTester<ThrowingValue<>>{})
+          .WithInvariants(absl::strong_guarantee)
+          .Test());
   EXPECT_EQ(ExhaustivenessTester<ThrowingValue<>>::successes, 0xF);
 }
 
diff --git a/absl/base/internal/direct_mmap.h b/absl/base/internal/direct_mmap.h
index 87576df6..4bd273ed 100644
--- a/absl/base/internal/direct_mmap.h
+++ b/absl/base/internal/direct_mmap.h
@@ -67,7 +67,7 @@ namespace base_internal {
 // Platform specific logic extracted from
 // https://chromium.googlesource.com/linux-syscall-support/+/master/linux_syscall_support.h
 inline void* DirectMmap(void* start, size_t length, int prot, int flags, int fd,
-                        off64_t offset) __THROW {
+                        off64_t offset) noexcept {
 #if defined(__i386__) || defined(__ARM_ARCH_3__) || defined(__ARM_EABI__) || \
     (defined(__mips__) && _MIPS_SIM == _MIPS_SIM_ABI32) ||                   \
     (defined(__PPC__) && !defined(__PPC64__)) ||                             \
@@ -129,6 +129,9 @@ inline int DirectMunmap(void* start, size_t length) {
 // For non-linux platforms where we have mmap, just dispatch directly to the
 // actual mmap()/munmap() methods.
 
+namespace absl {
+namespace base_internal {
+
 inline void* DirectMmap(void* start, size_t length, int prot, int flags, int fd,
                         off_t offset) {
   return mmap(start, length, prot, flags, fd, offset);
@@ -138,6 +141,9 @@ inline int DirectMunmap(void* start, size_t length) {
   return munmap(start, length);
 }
 
+}  // namespace base_internal
+}  // namespace absl
+
 #endif  // __linux__
 
 #endif  // ABSL_HAVE_MMAP
diff --git a/absl/base/internal/exception_safety_testing.cc b/absl/base/internal/exception_safety_testing.cc
index 821438ec..c6f7c7cf 100644
--- a/absl/base/internal/exception_safety_testing.cc
+++ b/absl/base/internal/exception_safety_testing.cc
@@ -18,7 +18,10 @@
 #include "absl/meta/type_traits.h"
 
 namespace absl {
+
 exceptions_internal::NoThrowTag no_throw_ctor;
+exceptions_internal::StrongGuaranteeTagType strong_guarantee;
+
 namespace exceptions_internal {
 
 int countdown = -1;
diff --git a/absl/base/internal/exception_safety_testing.h b/absl/base/internal/exception_safety_testing.h
index a0cd33b4..3493b5e2 100644
--- a/absl/base/internal/exception_safety_testing.h
+++ b/absl/base/internal/exception_safety_testing.h
@@ -23,6 +23,7 @@
 #include <initializer_list>
 #include <iosfwd>
 #include <string>
+#include <tuple>
 #include <unordered_map>
 
 #include "gtest/gtest.h"
@@ -35,7 +36,6 @@
 #include "absl/types/optional.h"
 
 namespace absl {
-struct InternalAbslNamespaceFinder {};
 
 struct ConstructorTracker;
 
@@ -63,6 +63,7 @@ constexpr NoThrow operator&(NoThrow a, NoThrow b) {
 
 namespace exceptions_internal {
 struct NoThrowTag {};
+struct StrongGuaranteeTagType {};
 
 constexpr bool ThrowingAllowed(NoThrow flags, NoThrow flag) {
   return !static_cast<bool>(flags & flag);
@@ -87,8 +88,7 @@ class TestException {
 // bad_alloc exception in TestExceptionSafety.
 class TestBadAllocException : public std::bad_alloc, public TestException {
  public:
-  explicit TestBadAllocException(absl::string_view msg)
-      : TestException(msg) {}
+  explicit TestBadAllocException(absl::string_view msg) : TestException(msg) {}
   using TestException::what;
 };
 
@@ -128,75 +128,73 @@ class TrackedObject {
   friend struct ::absl::ConstructorTracker;
 };
 
-template <typename Factory>
-using FactoryType = typename absl::result_of_t<Factory()>::element_type;
-
-// 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 Checker>
-absl::optional<testing::AssertionResult> TestCheckerAtCountdown(
-    Factory factory, const Op& op, int count, const Checker& check) {
+template <typename Factory, typename Operation, typename Invariant>
+absl::optional<testing::AssertionResult> TestSingleInvariantAtCountdownImpl(
+    const Factory& factory, const Operation& operation, int count,
+    const Invariant& invariant) {
   auto t_ptr = factory();
-  absl::optional<testing::AssertionResult> out;
+  absl::optional<testing::AssertionResult> current_res;
+  exceptions_internal::countdown = count;
   try {
-    exceptions_internal::countdown = count;
-    op(t_ptr.get());
+    operation(t_ptr.get());
   } catch (const exceptions_internal::TestException& e) {
-    out.emplace(check(t_ptr.get()));
-    if (!*out) {
-      *out << " caused by exception thrown by " << e.what();
+    current_res.emplace(invariant(t_ptr.get()));
+    if (!current_res.value()) {
+      *current_res << e.what() << " failed invariant check";
     }
   }
-  return out;
+  exceptions_internal::countdown = -1;
+  return current_res;
+}
+
+template <typename Factory, typename Operation>
+absl::optional<testing::AssertionResult> TestSingleInvariantAtCountdownImpl(
+    const Factory& factory, const Operation& operation, int count,
+    StrongGuaranteeTagType) {
+  using TPtr = typename decltype(factory())::pointer;
+  auto t_is_strong = [&](TPtr t) { return *t == *factory(); };
+  return TestSingleInvariantAtCountdownImpl(factory, operation, count,
+                                            t_is_strong);
 }
 
-template <typename Factory, typename Op, typename Checker>
-int UpdateOut(Factory factory, const Op& op, int count, const Checker& checker,
-              testing::AssertionResult* out) {
-  if (*out) *out = *TestCheckerAtCountdown(factory, op, count, checker);
+template <typename Factory, typename Operation, typename Invariant>
+int TestSingleInvariantAtCountdown(
+    const Factory& factory, const Operation& operation, int count,
+    const Invariant& invariant,
+    absl::optional<testing::AssertionResult>* reduced_res) {
+  // If reduced_res is empty, it means the current call to
+  // TestSingleInvariantAtCountdown(...) is the first test being run so we do
+  // want to run it. Alternatively, if it's not empty (meaning a previous test
+  // has run) we want to check if it passed. If the previous test did pass, we
+  // want to contine running tests so we do want to run the current one. If it
+  // failed, we want to short circuit so as not to overwrite the AssertionResult
+  // output. If that's the case, we do not run the current test and instead we
+  // simply return.
+  if (!reduced_res->has_value() || reduced_res->value()) {
+    *reduced_res = TestSingleInvariantAtCountdownImpl(factory, operation, count,
+                                                      invariant);
+  }
   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>
-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, InternalAbslNamespaceFinder());
-      });
-  if (!out.has_value()) return out;
+template <typename Factory, typename Operation, typename... Invariants>
+inline absl::optional<testing::AssertionResult> TestAllInvariantsAtCountdown(
+    const Factory& factory, const Operation& operation, int count,
+    const Invariants&... invariants) {
+  absl::optional<testing::AssertionResult> reduced_res;
 
   // Run each checker, short circuiting after the first failure
-  int dummy[] = {0, (UpdateOut(factory, op, count, checkers, &*out))...};
+  int dummy[] = {
+      0, (TestSingleInvariantAtCountdown(factory, operation, count, invariants,
+                                         &reduced_res))...};
   static_cast<void>(dummy);
-  return out;
+  return reduced_res;
 }
 
-template <typename T, typename EqualTo>
-class StrongGuaranteeTester {
- public:
-  explicit StrongGuaranteeTester(std::unique_ptr<T> t_ptr, EqualTo eq) noexcept
-      : val_(std::move(t_ptr)), eq_(eq) {}
-
-  testing::AssertionResult operator()(T* other) const {
-    return eq_(*val_, *other) ? testing::AssertionSuccess()
-                              : testing::AssertionFailure() << "State changed";
-  }
-
- private:
-  std::unique_ptr<T> val_;
-  EqualTo eq_;
-};
 }  // namespace exceptions_internal
 
 extern exceptions_internal::NoThrowTag no_throw_ctor;
+extern exceptions_internal::StrongGuaranteeTagType strong_guarantee;
 
 // These are useful for tests which just construct objects and make sure there
 // are no leaks.
@@ -208,7 +206,7 @@ inline void UnsetCountdown() { exceptions_internal::countdown = -1; }
 class ThrowingBool {
  public:
   ThrowingBool(bool b) noexcept : b_(b) {}  // NOLINT(runtime/explicit)
-  operator bool() const {  // NOLINT(runtime/explicit)
+  operator bool() const {                   // NOLINT
     exceptions_internal::MaybeThrow(ABSL_PRETTY_FUNCTION);
     return b_;
   }
@@ -734,10 +732,9 @@ template <typename T, typename... Args>
 T TestThrowingCtor(Args&&... args) {
   struct Cleanup {
     ~Cleanup() { UnsetCountdown(); }
-  };
-  Cleanup c;
-  for (int countdown = 0;; ++countdown) {
-    exceptions_internal::countdown = countdown;
+  } c;
+  for (int count = 0;; ++count) {
+    exceptions_internal::countdown = count;
     try {
       return T(std::forward<Args>(args)...);
     } catch (const exceptions_internal::TestException&) {
@@ -745,58 +742,237 @@ 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*, 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
-//   should always return pointers to values which compare equal.
-//   * FunctionFromTPtrToVoid: A functor exercising the function under test.  It
-//   should take a T* and return void.
-//   * Checkers: Any number of functions taking a T* and returning
-//   anything contextually convertible to bool.  If a testing::AssertionResult
-//   is used then the error message is kept.  These test invariants related to
-//   the operation. To test the strong guarantee, pass
-//   absl::StrongGuarantee(factory).  A checker may freely modify the passed-in
-//   T, for example to make sure the T can be set to a known state.
-template <typename TFactory, typename FunctionFromTPtrToVoid,
-          typename... Checkers>
-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()) {
-      return testing::AssertionSuccess();
+namespace exceptions_internal {
+
+// Dummy struct for ExceptionSafetyTester<> partial state.
+struct UninitializedT {};
+
+template <typename T>
+class DefaultFactory {
+ public:
+  explicit DefaultFactory(const T& t) : t_(t) {}
+  std::unique_ptr<T> operator()() const { return absl::make_unique<T>(t_); }
+
+ private:
+  T t_;
+};
+
+template <size_t LazyInvariantsCount, typename LazyFactory,
+          typename LazyOperation>
+using EnableIfTestable = typename absl::enable_if_t<
+    LazyInvariantsCount != 0 &&
+    !std::is_same<LazyFactory, UninitializedT>::value &&
+    !std::is_same<LazyOperation, UninitializedT>::value>;
+
+template <typename Factory = UninitializedT,
+          typename Operation = UninitializedT, typename... Invariants>
+class ExceptionSafetyTester;
+
+}  // namespace exceptions_internal
+
+exceptions_internal::ExceptionSafetyTester<> MakeExceptionSafetyTester();
+
+namespace exceptions_internal {
+
+/*
+ * Builds a tester object that tests if performing a operation on a T follows
+ * exception safety guarantees. Verification is done via invariant assertion
+ * callbacks applied to T instances post-throw.
+ *
+ * Template parameters for ExceptionSafetyTester:
+ *
+ * - Factory: The factory object (passed in via tester.WithFactory(...) or
+ *   tester.WithInitialValue(...)) must be invocable with the signature
+ *   `std::unique_ptr<T> operator()() const` where T is the type being tested.
+ *   It is used for reliably creating identical T instances to test on.
+ *
+ * - Operation: The operation object (passsed in via tester.WithOperation(...)
+ *   or tester.Test(...)) must be invocable with the signature
+ *   `void operator()(T*) const` where T is the type being tested. It is used
+ *   for performing steps on a T instance that may throw and that need to be
+ *   checked for exception safety. Each call to the operation will receive a
+ *   fresh T instance so it's free to modify and destroy the T instances as it
+ *   pleases.
+ *
+ * - Invariants...: The invariant assertion callback objects (passed in via
+ *   tester.WithInvariants(...)) must be invocable with the signature
+ *   `testing::AssertionResult operator()(T*) const` where T is the type being
+ *   tested. Invariant assertion callbacks are provided T instances post-throw.
+ *   They must return testing::AssertionSuccess when the type invariants of the
+ *   provided T instance hold. If the type invariants of the T instance do not
+ *   hold, they must return testing::AssertionFailure. Execution order of
+ *   Invariants... is unspecified. They will each individually get a fresh T
+ *   instance so they are free to modify and destroy the T instances as they
+ *   please.
+ */
+template <typename Factory, typename Operation, typename... Invariants>
+class ExceptionSafetyTester {
+ public:
+  /*
+   * Returns a new ExceptionSafetyTester with an included T factory based on the
+   * provided T instance. The existing factory will not be included in the newly
+   * created tester instance. The created factory returns a new T instance by
+   * copy-constructing the provided const T& t.
+   *
+   * Preconditions for tester.WithInitialValue(const T& t):
+   *
+   * - The const T& t object must be copy-constructible where T is the type
+   *   being tested. For non-copy-constructible objects, use the method
+   *   tester.WithFactory(...).
+   */
+  template <typename T>
+  ExceptionSafetyTester<DefaultFactory<T>, Operation, Invariants...>
+  WithInitialValue(const T& t) const {
+    return WithFactory(DefaultFactory<T>(t));
+  }
+
+  /*
+   * Returns a new ExceptionSafetyTester with the provided T factory included.
+   * The existing factory will not be included in the newly-created tester
+   * instance. This method is intended for use with types lacking a copy
+   * constructor. Types that can be copy-constructed should instead use the
+   * method tester.WithInitialValue(...).
+   */
+  template <typename NewFactory>
+  ExceptionSafetyTester<absl::decay_t<NewFactory>, Operation, Invariants...>
+  WithFactory(const NewFactory& new_factory) const {
+    return {new_factory, operation_, invariants_};
+  }
+
+  /*
+   * Returns a new ExceptionSafetyTester with the provided testable operation
+   * included. The existing operation will not be included in the newly created
+   * tester.
+   */
+  template <typename NewOperation>
+  ExceptionSafetyTester<Factory, absl::decay_t<NewOperation>, Invariants...>
+  WithOperation(const NewOperation& new_operation) const {
+    return {factory_, new_operation, invariants_};
+  }
+
+  /*
+   * Returns a new ExceptionSafetyTester with the provided MoreInvariants...
+   * combined with the Invariants... that were already included in the instance
+   * on which the method was called. Invariants... cannot be removed or replaced
+   * once added to an ExceptionSafetyTester instance. A fresh object must be
+   * created in order to get an empty Invariants... list.
+   *
+   * In addition to passing in custom invariant assertion callbacks, this method
+   * accepts `absl::strong_guarantee` as an argument which checks T instances
+   * post-throw against freshly created T instances via operator== to verify
+   * that any state changes made during the execution of the operation were
+   * properly rolled back.
+   */
+  template <typename... MoreInvariants>
+  ExceptionSafetyTester<Factory, Operation, Invariants...,
+                        absl::decay_t<MoreInvariants>...>
+  WithInvariants(const MoreInvariants&... more_invariants) const {
+    return {factory_, operation_,
+            std::tuple_cat(invariants_,
+                           std::tuple<absl::decay_t<MoreInvariants>...>(
+                               more_invariants...))};
+  }
+
+  /*
+   * Returns a testing::AssertionResult that is the reduced result of the
+   * exception safety algorithm. The algorithm short circuits and returns
+   * AssertionFailure after the first invariant callback returns an
+   * AssertionFailure. Otherwise, if all invariant callbacks return an
+   * AssertionSuccess, the reduced result is AssertionSuccess.
+   *
+   * The passed-in testable operation will not be saved in a new tester instance
+   * nor will it modify/replace the existing tester instance. This is useful
+   * when each operation being tested is unique and does not need to be reused.
+   *
+   * Preconditions for tester.Test(const NewOperation& new_operation):
+   *
+   * - May only be called after at least one invariant assertion callback and a
+   *   factory or initial value have been provided.
+   */
+  template <
+      typename NewOperation,
+      typename = EnableIfTestable<sizeof...(Invariants), Factory, NewOperation>>
+  testing::AssertionResult Test(const NewOperation& new_operation) const {
+    return TestImpl(new_operation, absl::index_sequence_for<Invariants...>());
+  }
+
+  /*
+   * Returns a testing::AssertionResult that is the reduced result of the
+   * exception safety algorithm. The algorithm short circuits and returns
+   * AssertionFailure after the first invariant callback returns an
+   * AssertionFailure. Otherwise, if all invariant callbacks return an
+   * AssertionSuccess, the reduced result is AssertionSuccess.
+   *
+   * Preconditions for tester.Test():
+   *
+   * - May only be called after at least one invariant assertion callback, a
+   *   factory or initial value and a testable operation have been provided.
+   */
+  template <typename LazyOperation = Operation,
+            typename =
+                EnableIfTestable<sizeof...(Invariants), Factory, LazyOperation>>
+  testing::AssertionResult Test() const {
+    return TestImpl(operation_, absl::index_sequence_for<Invariants...>());
+  }
+
+ private:
+  template <typename, typename, typename...>
+  friend class ExceptionSafetyTester;
+
+  friend ExceptionSafetyTester<> absl::MakeExceptionSafetyTester();
+
+  ExceptionSafetyTester() {}
+
+  ExceptionSafetyTester(const Factory& f, const Operation& o,
+                        const std::tuple<Invariants...>& i)
+      : factory_(f), operation_(o), invariants_(i) {}
+
+  template <typename SelectedOperation, size_t... Indices>
+  testing::AssertionResult TestImpl(const SelectedOperation& selected_operation,
+                                    absl::index_sequence<Indices...>) const {
+    // Starting from 0 and counting upwards until one of the exit conditions is
+    // hit...
+    for (int count = 0;; ++count) {
+      // Run the full exception safety test algorithm for the current countdown
+      auto reduced_res =
+          TestAllInvariantsAtCountdown(factory_, selected_operation, count,
+                                       std::get<Indices>(invariants_)...);
+      // If there is no value in the optional, no invariants were run because no
+      // exception was thrown. This means that the test is complete and the loop
+      // can exit successfully.
+      if (!reduced_res.has_value()) {
+        return testing::AssertionSuccess();
+      }
+      // If the optional is not empty and the value is falsy, an invariant check
+      // failed so the test must exit to propegate the failure.
+      if (!reduced_res.value()) {
+        return reduced_res.value();
+      }
+      // If the optional is not empty and the value is not falsy, it means
+      // exceptions were thrown but the invariants passed so the test must
+      // continue to run.
     }
-    if (!*out) return *out;
   }
-}
 
-// Returns a functor to test for the strong exception-safety guarantee.
-// Equality comparisons are made against the T provided by the factory and
-// default to using operator==.
-//
-// Parameters:
-//   * TFactory: operator() returns a unique_ptr to the type under test.  It
-//   should always return pointers to values which compare equal.
-template <typename TFactory, typename EqualTo = std::equal_to<
-                                 exceptions_internal::FactoryType<TFactory>>>
-exceptions_internal::StrongGuaranteeTester<
-    exceptions_internal::FactoryType<TFactory>, EqualTo>
-StrongGuarantee(TFactory factory, EqualTo eq = EqualTo()) {
-  return exceptions_internal::StrongGuaranteeTester<
-      exceptions_internal::FactoryType<TFactory>, EqualTo>(factory(), eq);
+  Factory factory_;
+  Operation operation_;
+  std::tuple<Invariants...> invariants_;
+};
+
+}  // namespace exceptions_internal
+
+/*
+ * Constructs an empty ExceptionSafetyTester. All ExceptionSafetyTester
+ * objects are immutable and all With[thing] mutation methods return new
+ * instances of ExceptionSafetyTester.
+ *
+ * In order to test a T for exception safety, a factory for that T, a testable
+ * operation, and at least one invariant callback returning an assertion
+ * result must be applied using the respective methods.
+ */
+inline exceptions_internal::ExceptionSafetyTester<>
+MakeExceptionSafetyTester() {
+  return {};
 }
 
 }  // namespace absl
diff --git a/absl/base/internal/low_level_alloc.cc b/absl/base/internal/low_level_alloc.cc
index 5f047a54..0a6f3070 100644
--- a/absl/base/internal/low_level_alloc.cc
+++ b/absl/base/internal/low_level_alloc.cc
@@ -23,6 +23,7 @@
 
 #include "absl/base/call_once.h"
 #include "absl/base/config.h"
+#include "absl/base/internal/direct_mmap.h"
 #include "absl/base/internal/scheduling_mode.h"
 #include "absl/base/macros.h"
 #include "absl/base/thread_annotations.h"
@@ -49,8 +50,6 @@
 #include <new>                   // for placement-new
 
 #include "absl/base/dynamic_annotations.h"
-#include "absl/base/internal/malloc_hook.h"
-#include "absl/base/internal/malloc_hook_invoke.h"
 #include "absl/base/internal/raw_logging.h"
 #include "absl/base/internal/spinlock.h"
 
@@ -405,7 +404,7 @@ bool LowLevelAlloc::DeleteArena(Arena *arena) {
     if ((arena->flags & LowLevelAlloc::kAsyncSignalSafe) == 0) {
       munmap_result = munmap(region, size);
     } else {
-      munmap_result = MallocHook::UnhookedMUnmap(region, size);
+      munmap_result = base_internal::DirectMunmap(region, size);
     }
     if (munmap_result != 0) {
       ABSL_RAW_LOG(FATAL, "LowLevelAlloc::DeleteArena: munmap failed: %d",
@@ -503,9 +502,6 @@ void LowLevelAlloc::Free(void *v) {
     ABSL_RAW_CHECK(f->header.magic == Magic(kMagicAllocated, &f->header),
                    "bad magic number in Free()");
     LowLevelAlloc::Arena *arena = f->header.arena;
-    if ((arena->flags & kCallMallocHook) != 0) {
-      MallocHook::InvokeDeleteHook(v);
-    }
     ArenaLock section(arena);
     AddToFreelist(v, arena);
     ABSL_RAW_CHECK(arena->allocation_count > 0, "nothing in arena to free");
@@ -550,7 +546,7 @@ static void *DoAllocWithArena(size_t request, LowLevelAlloc::Arena *arena) {
       ABSL_RAW_CHECK(new_pages != nullptr, "VirtualAlloc failed");
 #else
       if ((arena->flags & LowLevelAlloc::kAsyncSignalSafe) != 0) {
-        new_pages = MallocHook::UnhookedMMap(nullptr, new_pages_size,
+        new_pages = base_internal::DirectMmap(nullptr, new_pages_size,
             PROT_WRITE|PROT_READ, MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
       } else {
         new_pages = mmap(nullptr, new_pages_size, PROT_WRITE | PROT_READ,
@@ -593,21 +589,12 @@ static void *DoAllocWithArena(size_t request, LowLevelAlloc::Arena *arena) {
 
 void *LowLevelAlloc::Alloc(size_t request) {
   void *result = DoAllocWithArena(request, DefaultArena());
-  // The default arena always calls the malloc hook.
-  // This call must be directly in the user-called allocator function
-  // for MallocHook::GetCallerStackTrace to work properly
-  MallocHook::InvokeNewHook(result, request);
   return result;
 }
 
 void *LowLevelAlloc::AllocWithArena(size_t request, Arena *arena) {
   ABSL_RAW_CHECK(arena != nullptr, "must pass a valid arena");
   void *result = DoAllocWithArena(request, arena);
-  if ((arena->flags & kCallMallocHook) != 0) {
-    // this call must be directly in the user-called allocator function
-    // for MallocHook::GetCallerStackTrace to work properly
-    MallocHook::InvokeNewHook(result, request);
-  }
   return result;
 }
 
diff --git a/absl/base/internal/low_level_alloc_test.cc b/absl/base/internal/low_level_alloc_test.cc
index 7c359f30..cf2b3632 100644
--- a/absl/base/internal/low_level_alloc_test.cc
+++ b/absl/base/internal/low_level_alloc_test.cc
@@ -21,8 +21,6 @@
 #include <unordered_map>
 #include <utility>
 
-#include "absl/base/internal/malloc_hook.h"
-
 namespace absl {
 namespace base_internal {
 namespace {
@@ -139,58 +137,12 @@ static void Test(bool use_new_arena, bool call_malloc_hook, int n) {
     TEST_ASSERT(LowLevelAlloc::DeleteArena(arena));
   }
 }
-
-// used for counting allocates and frees
-static int32_t allocates;
-static int32_t frees;
-
-// ignore uses of the allocator not triggered by our test
-static std::thread::id* test_tid;
-
-// called on each alloc if kCallMallocHook specified
-static void AllocHook(const void *p, size_t size) {
-  if (using_low_level_alloc) {
-    if (*test_tid == std::this_thread::get_id()) {
-      allocates++;
-    }
-  }
-}
-
-// called on each free if kCallMallocHook specified
-static void FreeHook(const void *p) {
-  if (using_low_level_alloc) {
-    if (*test_tid == std::this_thread::get_id()) {
-      frees++;
-    }
-  }
-}
-
 // LowLevelAlloc is designed to be safe to call before main().
 static struct BeforeMain {
   BeforeMain() {
-    test_tid = new std::thread::id(std::this_thread::get_id());
-    TEST_ASSERT(MallocHook::AddNewHook(&AllocHook));
-    TEST_ASSERT(MallocHook::AddDeleteHook(&FreeHook));
-    TEST_ASSERT(allocates == 0);
-    TEST_ASSERT(frees == 0);
     Test(false, false, 50000);
-    TEST_ASSERT(allocates != 0);  // default arena calls hooks
-    TEST_ASSERT(frees != 0);
-    for (int i = 0; i != 16; i++) {
-      bool call_hooks = ((i & 1) == 1);
-      allocates = 0;
-      frees = 0;
-      Test(true, call_hooks, 15000);
-      if (call_hooks) {
-        TEST_ASSERT(allocates > 5000);  // arena calls hooks
-        TEST_ASSERT(frees > 5000);
-      } else {
-        TEST_ASSERT(allocates == 0);  // arena doesn't call hooks
-        TEST_ASSERT(frees == 0);
-      }
-    }
-    TEST_ASSERT(MallocHook::RemoveNewHook(&AllocHook));
-    TEST_ASSERT(MallocHook::RemoveDeleteHook(&FreeHook));
+    Test(true, false, 50000);
+    Test(true, true, 50000);
   }
 } before_main;
 
diff --git a/absl/base/internal/malloc_extension.cc b/absl/base/internal/malloc_extension.cc
deleted file mode 100644
index 5b906533..00000000
--- a/absl/base/internal/malloc_extension.cc
+++ /dev/null
@@ -1,162 +0,0 @@
-// Copyright 2017 The Abseil Authors.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//      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/malloc_extension.h"
-
-#include <assert.h>
-#include <string.h>
-#include <atomic>
-#include <string>
-
-#include "absl/base/dynamic_annotations.h"
-
-namespace absl {
-namespace base_internal {
-
-// SysAllocator implementation
-SysAllocator::~SysAllocator() {}
-void SysAllocator::GetStats(char* buffer, int) { buffer[0] = 0; }
-
-// Dummy key method to avoid weak vtable.
-void MallocExtensionWriter::UnusedKeyMethod() {}
-
-void StringMallocExtensionWriter::Write(const char* buf, int len) {
-  out_->append(buf, len);
-}
-
-// Default implementation -- does nothing
-MallocExtension::~MallocExtension() { }
-bool MallocExtension::VerifyAllMemory() { return true; }
-bool MallocExtension::VerifyNewMemory(const void*) { return true; }
-bool MallocExtension::VerifyArrayNewMemory(const void*) { return true; }
-bool MallocExtension::VerifyMallocMemory(const void*) { return true; }
-
-bool MallocExtension::GetNumericProperty(const char*, size_t*) {
-  return false;
-}
-
-bool MallocExtension::SetNumericProperty(const char*, size_t) {
-  return false;
-}
-
-void MallocExtension::GetStats(char* buffer, int length) {
-  assert(length > 0);
-  static_cast<void>(length);
-  buffer[0] = '\0';
-}
-
-bool MallocExtension::MallocMemoryStats(int* blocks, size_t* total,
-                                        int histogram[kMallocHistogramSize]) {
-  *blocks = 0;
-  *total = 0;
-  memset(histogram, 0, sizeof(*histogram) * kMallocHistogramSize);
-  return true;
-}
-
-void MallocExtension::MarkThreadIdle() {
-  // Default implementation does nothing
-}
-
-void MallocExtension::MarkThreadBusy() {
-  // Default implementation does nothing
-}
-
-SysAllocator* MallocExtension::GetSystemAllocator() {
-  return nullptr;
-}
-
-void MallocExtension::SetSystemAllocator(SysAllocator*) {
-  // Default implementation does nothing
-}
-
-void MallocExtension::ReleaseToSystem(size_t) {
-  // Default implementation does nothing
-}
-
-void MallocExtension::ReleaseFreeMemory() {
-  ReleaseToSystem(static_cast<size_t>(-1));   // SIZE_T_MAX
-}
-
-void MallocExtension::SetMemoryReleaseRate(double) {
-  // Default implementation does nothing
-}
-
-double MallocExtension::GetMemoryReleaseRate() {
-  return -1.0;
-}
-
-size_t MallocExtension::GetEstimatedAllocatedSize(size_t size) {
-  return size;
-}
-
-size_t MallocExtension::GetAllocatedSize(const void* p) {
-  assert(GetOwnership(p) != kNotOwned);
-  static_cast<void>(p);
-  return 0;
-}
-
-MallocExtension::Ownership MallocExtension::GetOwnership(const void*) {
-  return kUnknownOwnership;
-}
-
-void MallocExtension::GetProperties(MallocExtension::StatLevel,
-                                    std::map<std::string, Property>* result) {
-  result->clear();
-}
-
-size_t MallocExtension::ReleaseCPUMemory(int) {
-  return 0;
-}
-
-// The current malloc extension object.
-
-std::atomic<MallocExtension*> MallocExtension::current_instance_;
-
-MallocExtension* MallocExtension::InitModule() {
-  MallocExtension* ext = new MallocExtension;
-  current_instance_.store(ext, std::memory_order_release);
-  return ext;
-}
-
-void MallocExtension::Register(MallocExtension* implementation) {
-  InitModuleOnce();
-  // When running under valgrind, our custom malloc is replaced with
-  // valgrind's one and malloc extensions will not work.  (Note:
-  // callers should be responsible for checking that they are the
-  // malloc that is really being run, before calling Register.  This
-  // is just here as an extra sanity check.)
-  // Under compiler-based ThreadSanitizer RunningOnValgrind() returns true,
-  // but we still want to use malloc extensions.
-#ifndef THREAD_SANITIZER
-  if (RunningOnValgrind()) {
-    return;
-  }
-#endif  // #ifndef THREAD_SANITIZER
-  current_instance_.store(implementation, std::memory_order_release);
-}
-void MallocExtension::GetHeapSample(MallocExtensionWriter*) {}
-
-void MallocExtension::GetHeapGrowthStacks(MallocExtensionWriter*) {}
-
-void MallocExtension::GetFragmentationProfile(MallocExtensionWriter*) {}
-
-}  // namespace base_internal
-}  // namespace absl
-
-// 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.
-ABSL_ATTRIBUTE_WEAK ABSL_ATTRIBUTE_NOINLINE size_t nallocx(size_t size, int) {
-  return size;
-}
diff --git a/absl/base/internal/malloc_extension.h b/absl/base/internal/malloc_extension.h
deleted file mode 100644
index 75a00ce9..00000000
--- a/absl/base/internal/malloc_extension.h
+++ /dev/null
@@ -1,426 +0,0 @@
-//
-// Copyright 2017 The Abseil Authors.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//      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.
-//
-
-// Extra extensions exported by some malloc implementations.  These
-// extensions are accessed through a virtual base class so an
-// application can link against a malloc that does not implement these
-// extensions, and it will get default versions that do nothing.
-//
-// NOTE FOR C USERS: If you wish to use this functionality from within
-// a C program, see malloc_extension_c.h.
-
-#ifndef ABSL_BASE_INTERNAL_MALLOC_EXTENSION_H_
-#define ABSL_BASE_INTERNAL_MALLOC_EXTENSION_H_
-
-#include <stddef.h>
-#include <stdint.h>
-#include <atomic>
-#include <map>
-#include <memory>
-#include <string>
-#include <vector>
-
-#include "absl/base/attributes.h"
-#include "absl/base/macros.h"
-#include "absl/base/port.h"
-namespace absl {
-namespace base_internal {
-
-class MallocExtensionWriter;
-
-// Interface to a pluggable system allocator.
-class SysAllocator {
- public:
-  SysAllocator() {
-  }
-  virtual ~SysAllocator();
-
-  // Allocates "size"-byte of memory from system aligned with "alignment".
-  // Returns null if failed. Otherwise, the returned pointer p up to and
-  // including (p + actual_size -1) have been allocated.
-  virtual void* Alloc(size_t size, size_t *actual_size, size_t alignment) = 0;
-
-  // Get a human-readable description of the current state of the
-  // allocator.  The state is stored as a null-terminated std::string in
-  // a prefix of buffer.
-  virtual void GetStats(char* buffer, int length);
-};
-
-// The default implementations of the following routines do nothing.
-// All implementations should be thread-safe; the current ones
-// (DebugMallocImplementation and TCMallocImplementation) are.
-class MallocExtension {
- public:
-  virtual ~MallocExtension();
-
-  // Verifies that all blocks are valid.  Returns true if all are; dumps
-  // core otherwise.  A no-op except in debug mode.  Even in debug mode,
-  // they may not do any checking except with certain malloc
-  // implementations.  Thread-safe.
-  virtual bool VerifyAllMemory();
-
-  // Verifies that p was returned by new, has not been deleted, and is
-  // valid.  Returns true if p is good; dumps core otherwise.  A no-op
-  // except in debug mode.  Even in debug mode, may not do any checking
-  // except with certain malloc implementations.  Thread-safe.
-  virtual bool VerifyNewMemory(const void* p);
-
-  // Verifies that p was returned by new[], has not been deleted, and is
-  // valid.  Returns true if p is good; dumps core otherwise.  A no-op
-  // except in debug mode.  Even in debug mode, may not do any checking
-  // except with certain malloc implementations.  Thread-safe.
-  virtual bool VerifyArrayNewMemory(const void* p);
-
-  // Verifies that p was returned by malloc, has not been freed, and is
-  // valid.  Returns true if p is good; dumps core otherwise.  A no-op
-  // except in debug mode.  Even in debug mode, may not do any checking
-  // except with certain malloc implementations.  Thread-safe.
-  virtual bool VerifyMallocMemory(const void* p);
-
-  // If statistics collection is enabled, sets *blocks to be the number of
-  // currently allocated blocks, sets *total to be the total size allocated
-  // over all blocks, sets histogram[n] to be the number of blocks with
-  // size between 2^n-1 and 2^(n+1), and returns true.  Returns false, and
-  // does not change *blocks, *total, or *histogram, if statistics
-  // collection is disabled.
-  //
-  // Note that these statistics reflect memory allocated by new, new[],
-  // malloc(), and realloc(), but not mmap().  They may be larger (if not
-  // all pages have been written to) or smaller (if pages have been
-  // allocated by mmap()) than the total RSS size.  They will always be
-  // smaller than the total virtual memory size.
-  static constexpr int kMallocHistogramSize = 64;
-  virtual bool MallocMemoryStats(int* blocks, size_t* total,
-                                 int histogram[kMallocHistogramSize]);
-
-  // Get a human readable description of the current state of the malloc
-  // data structures.  The state is stored as a null-terminated std::string
-  // in a prefix of "buffer[0,buffer_length-1]".
-  // REQUIRES: buffer_length > 0.
-  virtual void GetStats(char* buffer, int buffer_length);
-
-  // Outputs to "writer" a sample of live objects and the stack traces
-  // that allocated these objects. The output can be passed to pprof.
-  virtual void GetHeapSample(MallocExtensionWriter* writer);
-
-  // Outputs to "writer" the stack traces that caused growth in the
-  // address space size. The output can be passed to "pprof".
-  virtual void GetHeapGrowthStacks(MallocExtensionWriter* writer);
-
-  // Outputs to "writer" a fragmentation profile. The output can be
-  // passed to "pprof".  In particular, the result is a list of
-  // <n,total,stacktrace> tuples that says that "total" bytes in "n"
-  // objects are currently unusable because of fragmentation caused by
-  // an allocation with the specified "stacktrace".
-  virtual void GetFragmentationProfile(MallocExtensionWriter* writer);
-
-  // -------------------------------------------------------------------
-  // Control operations for getting and setting malloc implementation
-  // specific parameters.  Some currently useful properties:
-  //
-  // generic
-  // -------
-  // "generic.current_allocated_bytes"
-  //      Number of bytes currently allocated by application
-  //      This property is not writable.
-  //
-  // "generic.heap_size"
-  //      Number of bytes in the heap ==
-  //            current_allocated_bytes +
-  //            fragmentation +
-  //            freed memory regions
-  //      This property is not writable.
-  //
-  // tcmalloc
-  // --------
-  // "tcmalloc.max_total_thread_cache_bytes"
-  //      Upper limit on total number of bytes stored across all
-  //      per-thread caches.  Default: 16MB.
-  //
-  // "tcmalloc.current_total_thread_cache_bytes"
-  //      Number of bytes used across all thread caches.
-  //      This property is not writable.
-  //
-  // "tcmalloc.pageheap_free_bytes"
-  //      Number of bytes in free, mapped pages in page heap.  These
-  //      bytes can be used to fulfill allocation requests.  They
-  //      always count towards virtual memory usage, and unless the
-  //      underlying memory is swapped out by the OS, they also count
-  //      towards physical memory usage.  This property is not writable.
-  //
-  // "tcmalloc.pageheap_unmapped_bytes"
-  //      Number of bytes in free, unmapped pages in page heap.
-  //      These are bytes that have been released back to the OS,
-  //      possibly by one of the MallocExtension "Release" calls.
-  //      They can be used to fulfill allocation requests, but
-  //      typically incur a page fault.  They always count towards
-  //      virtual memory usage, and depending on the OS, typically
-  //      do not count towards physical memory usage.  This property
-  //      is not writable.
-  //
-  //  "tcmalloc.per_cpu_caches_active"
-  //      Whether tcmalloc is using per-CPU caches (1 or 0 respectively).
-  //      This property is not writable.
-  // -------------------------------------------------------------------
-
-  // Get the named "property"'s value.  Returns true if the property
-  // is known.  Returns false if the property is not a valid property
-  // name for the current malloc implementation.
-  // REQUIRES: property != null; value != null
-  virtual bool GetNumericProperty(const char* property, size_t* value);
-
-  // Set the named "property"'s value.  Returns true if the property
-  // is known and writable.  Returns false if the property is not a
-  // valid property name for the current malloc implementation, or
-  // is not writable.
-  // REQUIRES: property != null
-  virtual bool SetNumericProperty(const char* property, size_t value);
-
-  // Mark the current thread as "idle".  This routine may optionally
-  // be called by threads as a hint to the malloc implementation that
-  // any thread-specific resources should be released.  Note: this may
-  // be an expensive routine, so it should not be called too often.
-  //
-  // Also, if the code that calls this routine will go to sleep for
-  // a while, it should take care to not allocate anything between
-  // the call to this routine and the beginning of the sleep.
-  //
-  // Most malloc implementations ignore this routine.
-  virtual void MarkThreadIdle();
-
-  // Mark the current thread as "busy".  This routine should be
-  // called after MarkThreadIdle() if the thread will now do more
-  // work.  If this method is not called, performance may suffer.
-  //
-  // Most malloc implementations ignore this routine.
-  virtual void MarkThreadBusy();
-
-  // Attempt to free any resources associated with cpu <cpu> (in the sense
-  // of only being usable from that CPU.)  Returns the number of bytes
-  // previously assigned to "cpu" that were freed.  Safe to call from
-  // any processor, not just <cpu>.
-  //
-  // Most malloc implementations ignore this routine (known exceptions:
-  // tcmalloc with --tcmalloc_per_cpu_caches=true.)
-  virtual size_t ReleaseCPUMemory(int cpu);
-
-  // Gets the system allocator used by the malloc extension instance. Returns
-  // null for malloc implementations that do not support pluggable system
-  // allocators.
-  virtual SysAllocator* GetSystemAllocator();
-
-  // Sets the system allocator to the specified.
-  //
-  // Users could register their own system allocators for malloc implementation
-  // that supports pluggable system allocators, such as TCMalloc, by doing:
-  //   alloc = new MyOwnSysAllocator();
-  //   MallocExtension::instance()->SetSystemAllocator(alloc);
-  // It's up to users whether to fall back (recommended) to the default
-  // system allocator (use GetSystemAllocator() above) or not. The caller is
-  // responsible to any necessary locking.
-  // See tcmalloc/system-alloc.h for the interface and
-  //     tcmalloc/memfs_malloc.cc for the examples.
-  //
-  // It's a no-op for malloc implementations that do not support pluggable
-  // system allocators.
-  virtual void SetSystemAllocator(SysAllocator *a);
-
-  // Try to release num_bytes of free memory back to the operating
-  // system for reuse.  Use this extension with caution -- to get this
-  // memory back may require faulting pages back in by the OS, and
-  // that may be slow.  (Currently only implemented in tcmalloc.)
-  virtual void ReleaseToSystem(size_t num_bytes);
-
-  // Same as ReleaseToSystem() but release as much memory as possible.
-  virtual void ReleaseFreeMemory();
-
-  // Sets the rate at which we release unused memory to the system.
-  // Zero means we never release memory back to the system.  Increase
-  // this flag to return memory faster; decrease it to return memory
-  // slower.  Reasonable rates are in the range [0,10].  (Currently
-  // only implemented in tcmalloc).
-  virtual void SetMemoryReleaseRate(double rate);
-
-  // Gets the release rate.  Returns a value < 0 if unknown.
-  virtual double GetMemoryReleaseRate();
-
-  // Returns the estimated number of bytes that will be allocated for
-  // a request of "size" bytes.  This is an estimate: an allocation of
-  // SIZE bytes may reserve more bytes, but will never reserve less.
-  // (Currently only implemented in tcmalloc, other implementations
-  // always return SIZE.)
-  // This is equivalent to malloc_good_size() in OS X.
-  virtual size_t GetEstimatedAllocatedSize(size_t size);
-
-  // Returns the actual number N of bytes reserved by tcmalloc for the
-  // pointer p.  This number may be equal to or greater than the
-  // number of bytes requested when p was allocated.
-  //
-  // This routine is just useful for statistics collection.  The
-  // client must *not* read or write from the extra bytes that are
-  // indicated by this call.
-  //
-  // Example, suppose the client gets memory by calling
-  //    p = malloc(10)
-  // and GetAllocatedSize(p) returns 16.  The client must only use the
-  // first 10 bytes p[0..9], and not attempt to read or write p[10..15].
-  //
-  // p must have been allocated by this malloc implementation, must
-  // not be an interior pointer -- that is, must be exactly the
-  // pointer returned to by malloc() et al., not some offset from that
-  // -- and should not have been freed yet.  p may be null.
-  // (Currently only implemented in tcmalloc; other implementations
-  // will return 0.)
-  virtual size_t GetAllocatedSize(const void* p);
-
-  // Returns kOwned if this malloc implementation allocated the memory
-  // pointed to by p, or kNotOwned if some other malloc implementation
-  // allocated it or p is null.  May also return kUnknownOwnership if
-  // the malloc implementation does not keep track of ownership.
-  // REQUIRES: p must be a value returned from a previous call to
-  // malloc(), calloc(), realloc(), memalign(), posix_memalign(),
-  // valloc(), pvalloc(), new, or new[], and must refer to memory that
-  // is currently allocated (so, for instance, you should not pass in
-  // a pointer after having called free() on it).
-  enum Ownership {
-    // NOTE: Enum values MUST be kept in sync with the version in
-    // malloc_extension_c.h
-    kUnknownOwnership = 0,
-    kOwned,
-    kNotOwned
-  };
-  virtual Ownership GetOwnership(const void* p);
-
-  // The current malloc implementation.  Always non-null.
-  static MallocExtension* instance() {
-    InitModuleOnce();
-    return current_instance_.load(std::memory_order_acquire);
-  }
-
-  // Change the malloc implementation.  Typically called by the
-  // malloc implementation during initialization.
-  static void Register(MallocExtension* implementation);
-
-  // Type used by GetProperties.  See comment on GetProperties.
-  struct Property {
-    size_t value;
-    // Stores breakdown of the property value bucketed by object size.
-    struct Bucket {
-      size_t min_object_size;
-      size_t max_object_size;
-      size_t size;
-    };
-    // Empty unless detailed info was asked for and this type has buckets
-    std::vector<Bucket> buckets;
-  };
-
-  // Type used by GetProperties.  See comment on GetProperties.
-  enum StatLevel { kSummary, kDetailed };
-
-  // Stores in *result detailed statistics about the malloc
-  // implementation. *result will be a map keyed by the name of
-  // the statistic. Each statistic has at least a "value" field.
-  //
-  // Some statistics may also contain an array of buckets if
-  // level==kDetailed and the "value" can be subdivided
-  // into different buckets for different object sizes.  If
-  // such detailed statistics are not available, Property::buckets
-  // will be empty.  Otherwise Property::buckets will contain
-  // potentially many entries.  For each bucket b, b.value
-  // will count the value contributed by objects in the range
-  // [b.min_object_size, b.max_object_size].
-  //
-  // Common across malloc implementations:
-  //  generic.bytes_in_use_by_app  -- Bytes currently in use by application
-  //  generic.physical_memory_used -- Overall (including malloc internals)
-  //  generic.virtual_memory_used  -- Overall (including malloc internals)
-  //
-  // Tcmalloc specific properties
-  //  tcmalloc.cpu_free            -- Bytes in per-cpu free-lists
-  //  tcmalloc.thread_cache_free   -- Bytes in per-thread free-lists
-  //  tcmalloc.transfer_cache      -- Bytes in cross-thread transfer caches
-  //  tcmalloc.central_cache_free  -- Bytes in central cache
-  //  tcmalloc.page_heap_free      -- Bytes in page heap
-  //  tcmalloc.page_heap_unmapped  -- Bytes in page heap (no backing phys. mem)
-  //  tcmalloc.metadata_bytes      -- Used by internal data structures
-  //  tcmalloc.thread_cache_count  -- Number of thread caches in use
-  //
-  // Debug allocator
-  //  debug.free_queue             -- Recently freed objects
-  virtual void GetProperties(StatLevel level,
-                             std::map<std::string, Property>* result);
- private:
-  static MallocExtension* InitModule();
-
-  static void InitModuleOnce() {
-    // Pointer stored here so heap leak checker will consider the default
-    // instance reachable, even if current_instance_ is later overridden by
-    // MallocExtension::Register().
-    ABSL_ATTRIBUTE_UNUSED static MallocExtension* default_instance =
-        InitModule();
-  }
-
-  static std::atomic<MallocExtension*> current_instance_;
-};
-
-// Base class than can handle output generated by GetHeapSample() and
-// GetHeapGrowthStacks().  Use the available subclass or roll your
-// own.  Useful if you want explicit control over the type of output
-// buffer used (e.g. IOBuffer, Cord, etc.)
-class MallocExtensionWriter {
- public:
-  virtual ~MallocExtensionWriter() {}
-  virtual void Write(const char* buf, int len) = 0;
- protected:
-  MallocExtensionWriter() {}
-  MallocExtensionWriter(const MallocExtensionWriter&) = delete;
-  MallocExtensionWriter& operator=(const MallocExtensionWriter&) = delete;
-
- private:
-  virtual void UnusedKeyMethod();  // Dummy key method to avoid weak vtable.
-};
-
-// A subclass that writes to the std::string "out".  NOTE: The generated
-// data is *appended* to "*out".  I.e., the old contents of "*out" are
-// preserved.
-class StringMallocExtensionWriter : public MallocExtensionWriter {
- public:
-  explicit StringMallocExtensionWriter(std::string* out) : out_(out) {}
-  void Write(const char* buf, int len) override;
-
- private:
-  std::string* const out_;
-  StringMallocExtensionWriter(const StringMallocExtensionWriter&) = delete;
-  StringMallocExtensionWriter& operator=(const StringMallocExtensionWriter&) =
-      delete;
-};
-
-}  // namespace base_internal
-}  // namespace absl
-
-// The nallocx function allocates no memory, but it performs the same size
-// computation as the malloc function, and returns the real size of the
-// allocation that would result from the equivalent malloc function call.
-// Default weak implementation returns size unchanged, but tcmalloc overrides it
-// and returns rounded up size. See the following link for details:
-// http://www.unix.com/man-page/freebsd/3/nallocx/
-extern "C" size_t nallocx(size_t size, int flags);
-
-#ifndef MALLOCX_LG_ALIGN
-#define MALLOCX_LG_ALIGN(la) (la)
-#endif
-
-#endif  // ABSL_BASE_INTERNAL_MALLOC_EXTENSION_H_
diff --git a/absl/base/internal/malloc_extension_c.h b/absl/base/internal/malloc_extension_c.h
deleted file mode 100644
index 5afc84a4..00000000
--- a/absl/base/internal/malloc_extension_c.h
+++ /dev/null
@@ -1,75 +0,0 @@
-/*
- * Copyright 2017 The Abseil Authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      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.
-
- * C shims for the C++ malloc_extension.h.  See malloc_extension.h for
- * details.  Note these C shims always work on
- * MallocExtension::instance(); it is not possible to have more than
- * one MallocExtension object in C applications.
- */
-
-#ifndef ABSL_BASE_INTERNAL_MALLOC_EXTENSION_C_H_
-#define ABSL_BASE_INTERNAL_MALLOC_EXTENSION_C_H_
-
-#include <stddef.h>
-#include <sys/types.h>
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-#define kMallocExtensionHistogramSize 64
-
-int MallocExtension_VerifyAllMemory(void);
-int MallocExtension_VerifyNewMemory(const void* p);
-int MallocExtension_VerifyArrayNewMemory(const void* p);
-int MallocExtension_VerifyMallocMemory(const void* p);
-int MallocExtension_MallocMemoryStats(int* blocks, size_t* total,
-                                      int histogram[kMallocExtensionHistogramSize]);
-
-void MallocExtension_GetStats(char* buffer, int buffer_length);
-
-/* TODO(csilvers): write a C version of these routines, that perhaps
- * takes a function ptr and a void *.
- */
-/* void MallocExtension_GetHeapSample(MallocExtensionWriter* result); */
-/* void MallocExtension_GetHeapGrowthStacks(MallocExtensionWriter* result); */
-
-int MallocExtension_GetNumericProperty(const char* property, size_t* value);
-int MallocExtension_SetNumericProperty(const char* property, size_t value);
-void MallocExtension_MarkThreadIdle(void);
-void MallocExtension_MarkThreadBusy(void);
-void MallocExtension_ReleaseToSystem(size_t num_bytes);
-void MallocExtension_ReleaseFreeMemory(void);
-size_t MallocExtension_GetEstimatedAllocatedSize(size_t size);
-size_t MallocExtension_GetAllocatedSize(const void* p);
-
-/*
- * NOTE: These enum values MUST be kept in sync with the version in
- *       malloc_extension.h
- */
-typedef enum {
-  MallocExtension_kUnknownOwnership = 0,
-  MallocExtension_kOwned,
-  MallocExtension_kNotOwned
-} MallocExtension_Ownership;
-
-MallocExtension_Ownership MallocExtension_GetOwnership(const void* p);
-
-
-#ifdef __cplusplus
-}   // extern "C"
-#endif
-
-#endif  /* ABSL_BASE_INTERNAL_MALLOC_EXTENSION_C_H_ */
diff --git a/absl/base/internal/malloc_extension_test.cc b/absl/base/internal/malloc_extension_test.cc
deleted file mode 100644
index 76605eb1..00000000
--- a/absl/base/internal/malloc_extension_test.cc
+++ /dev/null
@@ -1,79 +0,0 @@
-/*
- * Copyright 2017 The Abseil Authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      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 <algorithm>
-#include <cstdlib>
-
-#include "gtest/gtest.h"
-#include "absl/base/internal/malloc_extension.h"
-
-namespace absl {
-namespace base_internal {
-namespace {
-
-TEST(MallocExtension, MallocExtension) {
-  void* a = malloc(1000);
-
-  size_t cxx_bytes_used, c_bytes_used;
-  if (!MallocExtension::instance()->GetNumericProperty(
-          "generic.current_allocated_bytes", &cxx_bytes_used)) {
-    EXPECT_TRUE(ABSL_MALLOC_EXTENSION_TEST_ALLOW_MISSING_EXTENSION);
-  } else {
-    ASSERT_TRUE(MallocExtension::instance()->GetNumericProperty(
-        "generic.current_allocated_bytes", &cxx_bytes_used));
-#ifndef MEMORY_SANITIZER
-    EXPECT_GT(cxx_bytes_used, 1000);
-    EXPECT_GT(c_bytes_used, 1000);
-#endif
-
-    EXPECT_TRUE(MallocExtension::instance()->VerifyAllMemory());
-
-    EXPECT_EQ(MallocExtension::kOwned,
-              MallocExtension::instance()->GetOwnership(a));
-    // TODO(csilvers): this relies on undocumented behavior that
-    // GetOwnership works on stack-allocated variables.  Use a better test.
-    EXPECT_EQ(MallocExtension::kNotOwned,
-              MallocExtension::instance()->GetOwnership(&cxx_bytes_used));
-    EXPECT_EQ(MallocExtension::kNotOwned,
-              MallocExtension::instance()->GetOwnership(nullptr));
-    EXPECT_GE(MallocExtension::instance()->GetAllocatedSize(a), 1000);
-    // This is just a sanity check.  If we allocated too much, tcmalloc is
-    // broken
-    EXPECT_LE(MallocExtension::instance()->GetAllocatedSize(a), 5000);
-    EXPECT_GE(MallocExtension::instance()->GetEstimatedAllocatedSize(1000),
-              1000);
-    for (int i = 0; i < 10; ++i) {
-      void* p = malloc(i);
-      EXPECT_GE(MallocExtension::instance()->GetAllocatedSize(p),
-                MallocExtension::instance()->GetEstimatedAllocatedSize(i));
-      free(p);
-    }
-  }
-
-  free(a);
-}
-
-TEST(nallocx, SaneBehavior) {
-  for (size_t size = 0; size < 64 * 1024; ++size) {
-    size_t alloc_size = nallocx(size, 0);
-    EXPECT_LE(size, alloc_size) << "size is " << size;
-    EXPECT_LE(alloc_size, std::max(size + 100, 2 * size)) << "size is " << size;
-  }
-}
-
-}  // namespace
-}  // namespace base_internal
-}  // namespace absl
diff --git a/absl/base/internal/malloc_hook.cc b/absl/base/internal/malloc_hook.cc
deleted file mode 100644
index c364d3ff..00000000
--- a/absl/base/internal/malloc_hook.cc
+++ /dev/null
@@ -1,574 +0,0 @@
-// Copyright 2017 The Abseil Authors.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//      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/attributes.h"
-#include "absl/base/config.h"
-
-#if ABSL_HAVE_MMAP
-// Disable the glibc prototype of mremap(), as older versions of the
-// system headers define this function with only four arguments,
-// whereas newer versions allow an optional fifth argument:
-#define mremap glibc_mremap
-#include <sys/mman.h>
-#undef mremap
-#endif
-
-#include "absl/base/internal/malloc_hook.h"
-
-#include <algorithm>
-#include <cstddef>
-#include <cstdint>
-
-#include "absl/base/call_once.h"
-#include "absl/base/internal/malloc_hook_invoke.h"
-#include "absl/base/internal/raw_logging.h"
-#include "absl/base/internal/spinlock.h"
-#include "absl/base/macros.h"
-
-// __THROW is defined in glibc systems.  It means, counter-intuitively,
-// "This function will never throw an exception."  It's an optional
-// optimization tool, but we may need to use it to match glibc prototypes.
-#ifndef __THROW    // I guess we're not on a glibc system
-# define __THROW   // __THROW is just an optimization, so ok to make it ""
-#endif
-
-namespace absl {
-namespace base_internal {
-namespace {
-
-void RemoveInitialHooksAndCallInitializers();  // below.
-
-absl::once_flag once;
-
-// These hooks are installed in MallocHook as the only initial hooks.  The first
-// hook that is called will run RemoveInitialHooksAndCallInitializers (see the
-// definition below) and then redispatch to any malloc hooks installed by
-// RemoveInitialHooksAndCallInitializers.
-//
-// Note(llib): there is a possibility of a race in the event that there are
-// multiple threads running before the first allocation.  This is pretty
-// difficult to achieve, but if it is then multiple threads may concurrently do
-// allocations.  The first caller will call
-// RemoveInitialHooksAndCallInitializers via one of the initial hooks.  A
-// concurrent allocation may, depending on timing either:
-// * still have its initial malloc hook installed, run that and block on waiting
-//   for the first caller to finish its call to
-//   RemoveInitialHooksAndCallInitializers, and proceed normally.
-// * occur some time during the RemoveInitialHooksAndCallInitializers call, at
-//   which point there could be no initial hooks and the subsequent hooks that
-//   are about to be set up by RemoveInitialHooksAndCallInitializers haven't
-//   been installed yet.  I think the worst we can get is that some allocations
-//   will not get reported to some hooks set by the initializers called from
-//   RemoveInitialHooksAndCallInitializers.
-
-void InitialNewHook(const void* ptr, size_t size) {
-  absl::call_once(once, RemoveInitialHooksAndCallInitializers);
-  MallocHook::InvokeNewHook(ptr, size);
-}
-
-void InitialPreMMapHook(const void* start,
-                               size_t size,
-                               int protection,
-                               int flags,
-                               int fd,
-                               off_t offset) {
-  absl::call_once(once, RemoveInitialHooksAndCallInitializers);
-  MallocHook::InvokePreMmapHook(start, size, protection, flags, fd, offset);
-}
-
-void InitialPreSbrkHook(ptrdiff_t increment) {
-  absl::call_once(once, RemoveInitialHooksAndCallInitializers);
-  MallocHook::InvokePreSbrkHook(increment);
-}
-
-// This function is called at most once by one of the above initial malloc
-// hooks.  It removes all initial hooks and initializes all other clients that
-// want to get control at the very first memory allocation.  The initializers
-// may assume that the initial malloc hooks have been removed.  The initializers
-// may set up malloc hooks and allocate memory.
-void RemoveInitialHooksAndCallInitializers() {
-  ABSL_RAW_CHECK(MallocHook::RemoveNewHook(&InitialNewHook), "");
-  ABSL_RAW_CHECK(MallocHook::RemovePreMmapHook(&InitialPreMMapHook), "");
-  ABSL_RAW_CHECK(MallocHook::RemovePreSbrkHook(&InitialPreSbrkHook), "");
-}
-
-}  // namespace
-}  // namespace base_internal
-}  // namespace absl
-
-namespace absl {
-namespace base_internal {
-
-// This lock is shared between all implementations of HookList::Add & Remove.
-// The potential for contention is very small.  This needs to be a SpinLock and
-// not a Mutex since it's possible for Mutex locking to allocate memory (e.g.,
-// per-thread allocation in debug builds), which could cause infinite recursion.
-static absl::base_internal::SpinLock hooklist_spinlock(
-    absl::base_internal::kLinkerInitialized);
-
-template <typename T>
-bool HookList<T>::Add(T value_as_t) {
-  if (value_as_t == T()) {
-    return false;
-  }
-  absl::base_internal::SpinLockHolder l(&hooklist_spinlock);
-  // Find the first slot in data that is 0.
-  int index = 0;
-  while ((index < kHookListMaxValues) &&
-         (priv_data[index].load(std::memory_order_relaxed) != 0)) {
-    ++index;
-  }
-  if (index == kHookListMaxValues) {
-    return false;
-  }
-  int prev_num_hooks = priv_end.load(std::memory_order_acquire);
-  priv_data[index].store(reinterpret_cast<intptr_t>(value_as_t),
-                         std::memory_order_release);
-  if (prev_num_hooks <= index) {
-    priv_end.store(index + 1, std::memory_order_release);
-  }
-  return true;
-}
-
-template <typename T>
-bool HookList<T>::Remove(T value_as_t) {
-  if (value_as_t == T()) {
-    return false;
-  }
-  absl::base_internal::SpinLockHolder l(&hooklist_spinlock);
-  int hooks_end = priv_end.load(std::memory_order_acquire);
-  int index = 0;
-  while (index < hooks_end &&
-         value_as_t != reinterpret_cast<T>(
-                           priv_data[index].load(std::memory_order_acquire))) {
-    ++index;
-  }
-  if (index == hooks_end) {
-    return false;
-  }
-  priv_data[index].store(0, std::memory_order_release);
-  if (hooks_end == index + 1) {
-    // Adjust hooks_end down to the lowest possible value.
-    hooks_end = index;
-    while ((hooks_end > 0) &&
-           (priv_data[hooks_end - 1].load(std::memory_order_acquire) == 0)) {
-      --hooks_end;
-    }
-    priv_end.store(hooks_end, std::memory_order_release);
-  }
-  return true;
-}
-
-template <typename T>
-int HookList<T>::Traverse(T* output_array, int n) const {
-  int hooks_end = priv_end.load(std::memory_order_acquire);
-  int actual_hooks_end = 0;
-  for (int i = 0; i < hooks_end && n > 0; ++i) {
-    T data = reinterpret_cast<T>(priv_data[i].load(std::memory_order_acquire));
-    if (data != T()) {
-      *output_array++ = data;
-      ++actual_hooks_end;
-      --n;
-    }
-  }
-  return actual_hooks_end;
-}
-
-// Initialize a HookList (optionally with the given initial_value in index 0).
-#define INIT_HOOK_LIST { {0}, {{}} }
-#define INIT_HOOK_LIST_WITH_VALUE(initial_value) \
-  { {1}, { {reinterpret_cast<intptr_t>(initial_value)} } }
-
-// Explicit instantiation for malloc_hook_test.cc.  This ensures all the methods
-// are instantiated.
-template struct HookList<MallocHook::NewHook>;
-
-HookList<MallocHook::NewHook> new_hooks_ =
-    INIT_HOOK_LIST_WITH_VALUE(&InitialNewHook);
-HookList<MallocHook::DeleteHook> delete_hooks_ = INIT_HOOK_LIST;
-HookList<MallocHook::SampledNewHook> sampled_new_hooks_ = INIT_HOOK_LIST;
-HookList<MallocHook::SampledDeleteHook> sampled_delete_hooks_ = INIT_HOOK_LIST;
-HookList<MallocHook::PreMmapHook> premmap_hooks_ =
-    INIT_HOOK_LIST_WITH_VALUE(&InitialPreMMapHook);
-HookList<MallocHook::MmapHook> mmap_hooks_ = INIT_HOOK_LIST;
-HookList<MallocHook::MunmapHook> munmap_hooks_ = INIT_HOOK_LIST;
-HookList<MallocHook::MremapHook> mremap_hooks_ = INIT_HOOK_LIST;
-HookList<MallocHook::PreSbrkHook> presbrk_hooks_ =
-    INIT_HOOK_LIST_WITH_VALUE(InitialPreSbrkHook);
-HookList<MallocHook::SbrkHook> sbrk_hooks_ = INIT_HOOK_LIST;
-
-// These lists contain either 0 or 1 hooks.
-HookList<MallocHook::MmapReplacement> mmap_replacement_ = INIT_HOOK_LIST;
-HookList<MallocHook::MunmapReplacement> munmap_replacement_ = INIT_HOOK_LIST;
-
-#undef INIT_HOOK_LIST_WITH_VALUE
-#undef INIT_HOOK_LIST
-
-bool MallocHook::AddNewHook(NewHook hook) { return new_hooks_.Add(hook); }
-
-bool MallocHook::RemoveNewHook(NewHook hook) { return new_hooks_.Remove(hook); }
-
-bool MallocHook::AddDeleteHook(DeleteHook hook) {
-  return delete_hooks_.Add(hook);
-}
-
-bool MallocHook::RemoveDeleteHook(DeleteHook hook) {
-  return delete_hooks_.Remove(hook);
-}
-
-bool MallocHook::AddSampledNewHook(SampledNewHook hook) {
-  return sampled_new_hooks_.Add(hook);
-}
-
-bool MallocHook::RemoveSampledNewHook(SampledNewHook hook) {
-  return sampled_new_hooks_.Remove(hook);
-}
-
-bool MallocHook::AddSampledDeleteHook(SampledDeleteHook hook) {
-  return sampled_delete_hooks_.Add(hook);
-}
-
-bool MallocHook::RemoveSampledDeleteHook(SampledDeleteHook hook) {
-  return sampled_delete_hooks_.Remove(hook);
-}
-
-bool MallocHook::AddPreMmapHook(PreMmapHook hook) {
-  return premmap_hooks_.Add(hook);
-}
-
-bool MallocHook::RemovePreMmapHook(PreMmapHook hook) {
-  return premmap_hooks_.Remove(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(mmap_replacement_.empty(),
-                 "Only one MMapReplacement is allowed.");
-  return mmap_replacement_.Add(hook);
-}
-
-bool MallocHook::RemoveMmapReplacement(MmapReplacement hook) {
-  return mmap_replacement_.Remove(hook);
-}
-
-bool MallocHook::AddMmapHook(MmapHook hook) { return mmap_hooks_.Add(hook); }
-
-bool MallocHook::RemoveMmapHook(MmapHook hook) {
-  return mmap_hooks_.Remove(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(munmap_replacement_.empty(),
-                 "Only one MunmapReplacement is allowed.");
-  return munmap_replacement_.Add(hook);
-}
-
-bool MallocHook::RemoveMunmapReplacement(MunmapReplacement hook) {
-  return munmap_replacement_.Remove(hook);
-}
-
-bool MallocHook::AddMunmapHook(MunmapHook hook) {
-  return munmap_hooks_.Add(hook);
-}
-
-bool MallocHook::RemoveMunmapHook(MunmapHook hook) {
-  return munmap_hooks_.Remove(hook);
-}
-
-bool MallocHook::AddMremapHook(MremapHook hook) {
-  return mremap_hooks_.Add(hook);
-}
-
-bool MallocHook::RemoveMremapHook(MremapHook hook) {
-  return mremap_hooks_.Remove(hook);
-}
-
-bool MallocHook::AddPreSbrkHook(PreSbrkHook hook) {
-  return presbrk_hooks_.Add(hook);
-}
-
-bool MallocHook::RemovePreSbrkHook(PreSbrkHook hook) {
-  return presbrk_hooks_.Remove(hook);
-}
-
-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
-// hooks.  Doing traversal first, and then calling the hooks ensures we only
-// call the hooks registered at the start.
-#define INVOKE_HOOKS(HookType, hook_list, args)                    \
-  do {                                                             \
-    HookType hooks[kHookListMaxValues];                            \
-    int num_hooks = hook_list.Traverse(hooks, kHookListMaxValues); \
-    for (int i = 0; i < num_hooks; ++i) {                          \
-      (*hooks[i]) args;                                            \
-    }                                                              \
-  } while (0)
-
-// There should only be one replacement. Return the result of the first
-// one, or false if there is none.
-#define INVOKE_REPLACEMENT(HookType, hook_list, args)              \
-  do {                                                             \
-    HookType hooks[kHookListMaxValues];                            \
-    int num_hooks = hook_list.Traverse(hooks, kHookListMaxValues); \
-    return (num_hooks > 0 && (*hooks[0])args);                     \
-  } while (0)
-
-void MallocHook::InvokeNewHookSlow(const void* ptr, size_t size) {
-  INVOKE_HOOKS(NewHook, new_hooks_, (ptr, size));
-}
-
-void MallocHook::InvokeDeleteHookSlow(const void* ptr) {
-  INVOKE_HOOKS(DeleteHook, delete_hooks_, (ptr));
-}
-
-void MallocHook::InvokeSampledNewHookSlow(const SampledAlloc* sampled_alloc) {
-  INVOKE_HOOKS(SampledNewHook, sampled_new_hooks_, (sampled_alloc));
-}
-
-void MallocHook::InvokeSampledDeleteHookSlow(AllocHandle handle) {
-  INVOKE_HOOKS(SampledDeleteHook, sampled_delete_hooks_, (handle));
-}
-
-void MallocHook::InvokePreMmapHookSlow(const void* start,
-                                       size_t size,
-                                       int protection,
-                                       int flags,
-                                       int fd,
-                                       off_t offset) {
-  INVOKE_HOOKS(PreMmapHook, premmap_hooks_, (start, size, protection, flags, fd,
-                                            offset));
-}
-
-void MallocHook::InvokeMmapHookSlow(const void* result,
-                                    const void* start,
-                                    size_t size,
-                                    int protection,
-                                    int flags,
-                                    int fd,
-                                    off_t offset) {
-  INVOKE_HOOKS(MmapHook, mmap_hooks_, (result, start, size, protection, flags,
-                                       fd, offset));
-}
-
-bool MallocHook::InvokeMmapReplacementSlow(const void* start,
-                                           size_t size,
-                                           int protection,
-                                           int flags,
-                                           int fd,
-                                           off_t offset,
-                                           void** result) {
-  INVOKE_REPLACEMENT(MmapReplacement, mmap_replacement_,
-                      (start, size, protection, flags, fd, offset, result));
-}
-
-void MallocHook::InvokeMunmapHookSlow(const void* start, size_t size) {
-  INVOKE_HOOKS(MunmapHook, munmap_hooks_, (start, size));
-}
-
-bool MallocHook::InvokeMunmapReplacementSlow(const void* start,
-                                             size_t size,
-                                             int* result) {
-  INVOKE_REPLACEMENT(MunmapReplacement, munmap_replacement_,
-                     (start, size, result));
-}
-
-void MallocHook::InvokeMremapHookSlow(const void* result,
-                                      const void* old_addr,
-                                      size_t old_size,
-                                      size_t new_size,
-                                      int flags,
-                                      const void* new_addr) {
-  INVOKE_HOOKS(MremapHook, mremap_hooks_, (result, old_addr, old_size, new_size,
-                                           flags, new_addr));
-}
-
-void MallocHook::InvokePreSbrkHookSlow(ptrdiff_t increment) {
-  INVOKE_HOOKS(PreSbrkHook, presbrk_hooks_, (increment));
-}
-
-void MallocHook::InvokeSbrkHookSlow(const void* result, ptrdiff_t increment) {
-  INVOKE_HOOKS(SbrkHook, sbrk_hooks_, (result, increment));
-}
-
-#undef INVOKE_HOOKS
-#undef INVOKE_REPLACEMENT
-
-}  // namespace base_internal
-}  // namespace absl
-
-ABSL_DEFINE_ATTRIBUTE_SECTION_VARS(malloc_hook);
-ABSL_DECLARE_ATTRIBUTE_SECTION_VARS(malloc_hook);
-// actual functions are in this file, malloc_hook.cc, and low_level_alloc.cc
-ABSL_DEFINE_ATTRIBUTE_SECTION_VARS(google_malloc);
-ABSL_DECLARE_ATTRIBUTE_SECTION_VARS(google_malloc);
-ABSL_DEFINE_ATTRIBUTE_SECTION_VARS(blink_malloc);
-ABSL_DECLARE_ATTRIBUTE_SECTION_VARS(blink_malloc);
-
-#define ADDR_IN_ATTRIBUTE_SECTION(addr, name)                         \
-  (reinterpret_cast<uintptr_t>(ABSL_ATTRIBUTE_SECTION_START(name)) <= \
-       reinterpret_cast<uintptr_t>(addr) &&                           \
-   reinterpret_cast<uintptr_t>(addr) <                                \
-       reinterpret_cast<uintptr_t>(ABSL_ATTRIBUTE_SECTION_STOP(name)))
-
-// Return true iff 'caller' is a return address within a function
-// that calls one of our hooks via MallocHook:Invoke*.
-// A helper for GetCallerStackTrace.
-static inline bool InHookCaller(const void* caller) {
-  return ADDR_IN_ATTRIBUTE_SECTION(caller, google_malloc) ||
-         ADDR_IN_ATTRIBUTE_SECTION(caller, malloc_hook) ||
-         ADDR_IN_ATTRIBUTE_SECTION(caller, blink_malloc);
-
-  // We can use one section for everything except tcmalloc_or_debug
-  // due to its special linkage mode, which prevents merging of the sections.
-}
-
-#undef ADDR_IN_ATTRIBUTE_SECTION
-
-static absl::once_flag in_hook_caller_once;
-
-static void InitializeInHookCaller() {
-  ABSL_INIT_ATTRIBUTE_SECTION_VARS(malloc_hook);
-  if (ABSL_ATTRIBUTE_SECTION_START(malloc_hook) ==
-      ABSL_ATTRIBUTE_SECTION_STOP(malloc_hook)) {
-    ABSL_RAW_LOG(ERROR,
-                 "malloc_hook section is missing, "
-                 "thus InHookCaller is broken!");
-  }
-  ABSL_INIT_ATTRIBUTE_SECTION_VARS(google_malloc);
-  if (ABSL_ATTRIBUTE_SECTION_START(google_malloc) ==
-      ABSL_ATTRIBUTE_SECTION_STOP(google_malloc)) {
-    ABSL_RAW_LOG(ERROR,
-                 "google_malloc section is missing, "
-                 "thus InHookCaller is broken!");
-  }
-  ABSL_INIT_ATTRIBUTE_SECTION_VARS(blink_malloc);
-}
-
-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.
-    // Note: this path is inaccurate when a hook is not called directly by an
-    // allocation function but is daisy-chained through another hook,
-    // search for MallocHook::(Get|Set|Invoke)* to find such cases.
-#ifdef NDEBUG
-    return get_stack_trace_fn(result, max_depth, skip_count);
-#else
-    return get_stack_trace_fn(result, max_depth, skip_count + 1);
-#endif
-    // due to -foptimize-sibling-calls in opt mode
-    // there's no need for extra frame skip here then
-  }
-  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.
-  static const int kStackSize = kMaxSkip + 1;
-  void* stack[kStackSize];
-  int depth =
-      get_stack_trace_fn(stack, kStackSize, 1);  // skip this function frame
-  if (depth == 0)
-    // silently propagate cases when get_stack_trace_fn does not work
-    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
-      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) {
-        // get frames for the missing depth
-        depth += get_stack_trace_fn(result + depth, max_depth - depth,
-                                    1 + kStackSize);
-      }
-      return depth;
-    }
-  }
-  ABSL_RAW_LOG(WARNING,
-               "Hooked allocator frame not found, returning empty trace");
-  // If this happens try increasing kMaxSkip
-  // or else something must be wrong with InHookCaller,
-  // e.g. for every section used in InHookCaller
-  // 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,
-// of course, to doing what these functions normally do).
-
-// The ABSL_MALLOC_HOOK_MMAP_DISABLE macro disables mmap/munmap interceptors.
-// Dynamic tools that intercept mmap/munmap can't be linked together with
-// malloc_hook interceptors. We disable the malloc_hook interceptors for the
-// widely-used dynamic tools, i.e. ThreadSanitizer and MemorySanitizer, but
-// still allow users to disable this in special cases that can't be easily
-// detected during compilation, via -DABSL_MALLOC_HOOK_MMAP_DISABLE or #define
-// ABSL_MALLOC_HOOK_MMAP_DISABLE.
-//
-// TODO(absl-team): Remove MALLOC_HOOK_MMAP_DISABLE in CROSSTOOL for tsan and
-// msan config; Replace MALLOC_HOOK_MMAP_DISABLE with
-// ABSL_MALLOC_HOOK_MMAP_DISABLE for other special cases.
-#if !defined(THREAD_SANITIZER) && !defined(MEMORY_SANITIZER) && \
-    !defined(ABSL_MALLOC_HOOK_MMAP_DISABLE) && !defined(__ANDROID__) && \
-    defined(__linux__)
-#include "absl/base/internal/malloc_hook_mmap_linux.inc"
-
-#elif ABSL_HAVE_MMAP
-
-namespace absl {
-namespace base_internal {
-
-// static
-void* MallocHook::UnhookedMMap(void* start, size_t size, int protection,
-                               int flags, int fd, off_t offset) {
-  void* result;
-  if (!MallocHook::InvokeMmapReplacement(
-          start, size, protection, flags, fd, offset, &result)) {
-    result = mmap(start, size, protection, flags, fd, offset);
-  }
-  return result;
-}
-
-// static
-int MallocHook::UnhookedMUnmap(void* start, size_t size) {
-  int result;
-  if (!MallocHook::InvokeMunmapReplacement(start, size, &result)) {
-    result = munmap(start, size);
-  }
-  return result;
-}
-
-}  // namespace base_internal
-}  // namespace absl
-
-#endif
diff --git a/absl/base/internal/malloc_hook.h b/absl/base/internal/malloc_hook.h
deleted file mode 100644
index 6b006eda..00000000
--- a/absl/base/internal/malloc_hook.h
+++ /dev/null
@@ -1,284 +0,0 @@
-//
-// Copyright 2017 The Abseil Authors.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//      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.
-//
-
-// Some of our malloc implementations can invoke the following hooks whenever
-// memory is allocated or deallocated.  MallocHook is thread-safe, and things
-// you do before calling AddFooHook(MyHook) are visible to any resulting calls
-// to MyHook.  Hooks must be thread-safe.  If you write:
-//
-//   CHECK(MallocHook::AddNewHook(&MyNewHook));
-//
-// MyNewHook will be invoked in subsequent calls in the current thread, but
-// there are no guarantees on when it might be invoked in other threads.
-//
-// There are a limited number of slots available for each hook type.  Add*Hook
-// will return false if there are no slots available.  Remove*Hook will return
-// false if the given hook was not already installed.
-//
-// The order in which individual hooks are called in Invoke*Hook is undefined.
-//
-// It is safe for a hook to remove itself within Invoke*Hook and add other
-// hooks.  Any hooks added inside a hook invocation (for the same hook type)
-// will not be invoked for the current invocation.
-//
-// One important user of these hooks is the heap profiler.
-//
-// CAVEAT: If you add new MallocHook::Invoke* calls then those calls must be
-// directly in the code of the (de)allocation function that is provided to the
-// user and that function must have an ABSL_ATTRIBUTE_SECTION(malloc_hook)
-// attribute.
-//
-// Note: the Invoke*Hook() functions are defined in malloc_hook-inl.h.  If you
-// need to invoke a hook (which you shouldn't unless you're part of tcmalloc),
-// be sure to #include malloc_hook-inl.h in addition to malloc_hook.h.
-//
-// NOTE FOR C USERS: If you want to use malloc_hook functionality from
-// a C program, #include malloc_hook_c.h instead of this file.
-//
-// IWYU pragma: private, include "base/malloc_hook.h"
-
-#ifndef ABSL_BASE_INTERNAL_MALLOC_HOOK_H_
-#define ABSL_BASE_INTERNAL_MALLOC_HOOK_H_
-
-#include <sys/types.h>
-#include <cstddef>
-
-#include "absl/base/config.h"
-#include "absl/base/internal/malloc_hook_c.h"
-#include "absl/base/port.h"
-
-namespace absl {
-namespace base_internal {
-
-// Note: malloc_hook_c.h defines MallocHook_*Hook and
-// MallocHook_{Add,Remove}*Hook.  The version of these inside the MallocHook
-// class are defined in terms of the malloc_hook_c version.  See malloc_hook_c.h
-// for details of these types/functions.
-
-class MallocHook {
- public:
-  // The NewHook is invoked whenever an object is being allocated.
-  // Object pointer and size are passed in.
-  // It may be passed null pointer if the allocator returned null.
-  typedef MallocHook_NewHook NewHook;
-  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;
-  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
-  // according to the sampling policy of an allocator such as tcmalloc.
-  // 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. 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;
-  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
-  // by an allocator for sampling is being deallocated.
-  // The handle identifying the object --as previously chosen by
-  // InvokeSampledNewHook()-- is passed in.
-  typedef MallocHook_SampledDeleteHook SampledDeleteHook;
-  typedef MallocHook_AllocHandle AllocHandle;
-  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
-  // before the mmap/mmap64 call is actually made.  Such a hook may be useful
-  // 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;
-  static bool AddPreMmapHook(PreMmapHook hook);
-  static bool RemovePreMmapHook(PreMmapHook hook);
-  inline static void InvokePreMmapHook(const void* start,
-                                       size_t size,
-                                       int protection,
-                                       int flags,
-                                       int fd,
-                                       off_t offset);
-
-  // The MmapReplacement is invoked with mmap's arguments and place to put the
-  // result into after the PreMmapHook but before the mmap/mmap64 call is
-  // actually made.
-  // The MmapReplacement should return true if it handled the call, or false
-  // if it is still necessary to call mmap/mmap64.
-  // This should be used only by experts, and users must be be
-  // extremely careful to avoid recursive calls to mmap. The replacement
-  // should be async signal safe.
-  // Only one MmapReplacement is supported. After setting an MmapReplacement
-  // you must call RemoveMmapReplacement before calling SetMmapReplacement
-  // again.
-  typedef MallocHook_MmapReplacement MmapReplacement;
-  static bool SetMmapReplacement(MmapReplacement hook);
-  static bool RemoveMmapReplacement(MmapReplacement hook);
-  inline static bool InvokeMmapReplacement(const void* start,
-                                           size_t size,
-                                           int protection,
-                                           int flags,
-                                           int fd,
-                                           off_t offset,
-                                           void** result);
-
-
-  // The MmapHook is invoked with mmap's return value and arguments whenever
-  // a region of memory has been just mapped.
-  // It may be passed MAP_FAILED if the mmap failed.
-  typedef MallocHook_MmapHook MmapHook;
-  static bool AddMmapHook(MmapHook hook);
-  static bool RemoveMmapHook(MmapHook hook);
-  inline static void InvokeMmapHook(const void* result,
-                                    const void* start,
-                                    size_t size,
-                                    int protection,
-                                    int flags,
-                                    int fd,
-                                    off_t offset);
-
-  // The MunmapReplacement is invoked with munmap's arguments and place to put
-  // the result into just before the munmap call is actually made.
-  // The MunmapReplacement should return true if it handled the call, or false
-  // if it is still necessary to call munmap.
-  // This should be used only by experts. The replacement should be
-  // async signal safe.
-  // Only one MunmapReplacement is supported. After setting an
-  // MunmapReplacement you must call RemoveMunmapReplacement before
-  // calling SetMunmapReplacement again.
-  typedef MallocHook_MunmapReplacement MunmapReplacement;
-  static bool SetMunmapReplacement(MunmapReplacement hook);
-  static bool RemoveMunmapReplacement(MunmapReplacement hook);
-  inline static bool InvokeMunmapReplacement(const void* start,
-                                             size_t size,
-                                             int* result);
-
-  // The MunmapHook is invoked with munmap's arguments just before the munmap
-  // call is actually made.
-  // TODO(maxim): Rename this to PreMunmapHook for consistency with PreMmapHook
-  // and PreSbrkHook.
-  typedef MallocHook_MunmapHook MunmapHook;
-  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;
-  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,
-                                      size_t new_size,
-                                      int flags,
-                                      const void* new_addr);
-
-  // The PreSbrkHook is invoked with sbrk's argument just before sbrk is called
-  // -- except when the increment is 0.  This is because sbrk(0) is often called
-  // to get the top of the memory stack, and is not actually a
-  // memory-allocation call.  It may be useful in memory-limited contexts,
-  // to catch allocations that will exceed the limit and take outside
-  // actions to increase such a limit.
-  typedef MallocHook_PreSbrkHook PreSbrkHook;
-  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
-  // has just executed -- except when the increment is 0.
-  // 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;
-  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
-  // base/stacktrace.h.
-  using GetStackTraceFn = int (*)(void**, int, int);
-
-  // 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.
-  // Stack trace is filled into *result up to the size of max_depth.
-  // The actual number of stack frames filled is returned.
-  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
-  // only by experts, since they bypass heapchecking, etc.
-  // Note: These do not run hooks, but they still use the MmapReplacement
-  // and MunmapReplacement.
-  static void* UnhookedMMap(void* start, size_t size, int protection, int flags,
-                            int fd, off_t offset);
-  static int UnhookedMUnmap(void* start, size_t size);
-#endif
-
- private:
-  // Slow path versions of Invoke*Hook.
-  static void InvokeNewHookSlow(const void* ptr,
-                                size_t size) ABSL_ATTRIBUTE_COLD;
-  static void InvokeDeleteHookSlow(const void* ptr) ABSL_ATTRIBUTE_COLD;
-  static void InvokeSampledNewHookSlow(const SampledAlloc* sampled_alloc)
-      ABSL_ATTRIBUTE_COLD;
-  static void InvokeSampledDeleteHookSlow(AllocHandle handle)
-      ABSL_ATTRIBUTE_COLD;
-  static void InvokePreMmapHookSlow(const void* start, size_t size,
-                                    int protection, int flags, int fd,
-                                    off_t offset) ABSL_ATTRIBUTE_COLD;
-  static void InvokeMmapHookSlow(const void* result, const void* start,
-                                 size_t size, int protection, int flags, int fd,
-                                 off_t offset) ABSL_ATTRIBUTE_COLD;
-  static bool InvokeMmapReplacementSlow(const void* start, size_t size,
-                                        int protection, int flags, int fd,
-                                        off_t offset,
-                                        void** result) ABSL_ATTRIBUTE_COLD;
-  static void InvokeMunmapHookSlow(const void* ptr,
-                                   size_t size) ABSL_ATTRIBUTE_COLD;
-  static bool InvokeMunmapReplacementSlow(const void* ptr, size_t size,
-                                          int* result) ABSL_ATTRIBUTE_COLD;
-  static void InvokeMremapHookSlow(const void* result, const void* old_addr,
-                                   size_t old_size, size_t new_size, int flags,
-                                   const void* new_addr) ABSL_ATTRIBUTE_COLD;
-  static void InvokePreSbrkHookSlow(ptrdiff_t increment) ABSL_ATTRIBUTE_COLD;
-  static void InvokeSbrkHookSlow(const void* result,
-                                 ptrdiff_t increment) ABSL_ATTRIBUTE_COLD;
-};
-
-}  // namespace base_internal
-}  // namespace absl
-#endif  // ABSL_BASE_INTERNAL_MALLOC_HOOK_H_
diff --git a/absl/base/internal/malloc_hook_c.h b/absl/base/internal/malloc_hook_c.h
deleted file mode 100644
index 7255ddc2..00000000
--- a/absl/base/internal/malloc_hook_c.h
+++ /dev/null
@@ -1,69 +0,0 @@
-/*
- * Copyright 2017 The Abseil Authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      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.
- */
-
-/*
- * C shims for the C++ malloc_hook.h.  See malloc_hook.h for details
- * on how to use these.
- */
-#ifndef ABSL_BASE_INTERNAL_MALLOC_HOOK_C_H_
-#define ABSL_BASE_INTERNAL_MALLOC_HOOK_C_H_
-
-#include <stddef.h>
-#include <stdint.h>
-#include <sys/types.h>
-
-#ifdef __cplusplus
-extern "C" {
-#endif  /* __cplusplus */
-
-typedef int (*MallocHook_GetStackTraceFn)(void**, int, int);
-typedef void (*MallocHook_NewHook)(const void* ptr, size_t size);
-typedef void (*MallocHook_DeleteHook)(const void* ptr);
-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);
-typedef void (*MallocHook_SampledDeleteHook)(MallocHook_AllocHandle handle);
-typedef void (*MallocHook_PreMmapHook)(const void* start, size_t size,
-                                       int protection, int flags, int fd,
-                                       off_t offset);
-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);
-typedef int (*MallocHook_MunmapReplacement)(const void* start, size_t size,
-                                            int* result);
-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);
-typedef void (*MallocHook_SbrkHook)(const void* result, ptrdiff_t increment);
-
-#ifdef __cplusplus
-}  /* extern "C" */
-#endif  /* __cplusplus */
-
-#endif  /* ABSL_BASE_INTERNAL_MALLOC_HOOK_C_H_ */
diff --git a/absl/base/internal/malloc_hook_invoke.h b/absl/base/internal/malloc_hook_invoke.h
deleted file mode 100644
index c08220cb..00000000
--- a/absl/base/internal/malloc_hook_invoke.h
+++ /dev/null
@@ -1,198 +0,0 @@
-//
-// Copyright 2017 The Abseil Authors.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//      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 has the implementation details of malloc_hook that are needed
-// to use malloc-hook inside the tcmalloc system.  It does not hold
-// any of the client-facing calls that are used to add new hooks.
-//
-// IWYU pragma: private, include "base/malloc_hook-inl.h"
-
-#ifndef ABSL_BASE_INTERNAL_MALLOC_HOOK_INVOKE_H_
-#define ABSL_BASE_INTERNAL_MALLOC_HOOK_INVOKE_H_
-
-#include <sys/types.h>
-#include <atomic>
-#include <cstddef>
-
-#include "absl/base/internal/malloc_hook.h"
-
-namespace absl {
-namespace base_internal {
-
-// Maximum of 7 hooks means that HookList is 8 words.
-static constexpr int kHookListMaxValues = 7;
-
-// HookList: a class that provides synchronized insertions and removals and
-// lockless traversal.  Most of the implementation is in malloc_hook.cc.
-template <typename T>
-struct HookList {
-  static_assert(sizeof(T) <= sizeof(intptr_t), "T_should_fit_in_intptr_t");
-
-  // Adds value to the list.  Note that duplicates are allowed.  Thread-safe and
-  // blocking (acquires hooklist_spinlock).  Returns true on success; false
-  // otherwise (failures include invalid value and no space left).
-  bool Add(T value);
-
-  // Removes the first entry matching value from the list.  Thread-safe and
-  // blocking (acquires hooklist_spinlock).  Returns true on success; false
-  // otherwise (failures include invalid value and no value found).
-  bool Remove(T value);
-
-  // Store up to n values of the list in output_array, and return the number of
-  // elements stored.  Thread-safe and non-blocking.  This is fast (one memory
-  // access) if the list is empty.
-  int Traverse(T* output_array, int n) const;
-
-  // Fast inline implementation for fast path of Invoke*Hook.
-  bool empty() const {
-    // empty() is only used as an optimization to determine if we should call
-    // Traverse which has proper acquire loads.  Memory reordering around a
-    // call to empty will either lead to an unnecessary Traverse call, or will
-    // miss invoking hooks, neither of which is a problem.
-    return priv_end.load(std::memory_order_relaxed) == 0;
-  }
-
-  // This internal data is not private so that the class is an aggregate and can
-  // be initialized by the linker.  Don't access this directly.  Use the
-  // INIT_HOOK_LIST macro in malloc_hook.cc.
-
-  // One more than the index of the last valid element in priv_data.  During
-  // 'Remove' this may be past the last valid element in priv_data, but
-  // subsequent values will be 0.
-  std::atomic<int> priv_end;
-  std::atomic<intptr_t> priv_data[kHookListMaxValues];
-};
-
-extern template struct HookList<MallocHook::NewHook>;
-
-extern HookList<MallocHook::NewHook> new_hooks_;
-extern HookList<MallocHook::DeleteHook> delete_hooks_;
-extern HookList<MallocHook::SampledNewHook> sampled_new_hooks_;
-extern HookList<MallocHook::SampledDeleteHook> sampled_delete_hooks_;
-extern HookList<MallocHook::PreMmapHook> premmap_hooks_;
-extern HookList<MallocHook::MmapHook> mmap_hooks_;
-extern HookList<MallocHook::MmapReplacement> mmap_replacement_;
-extern HookList<MallocHook::MunmapHook> munmap_hooks_;
-extern HookList<MallocHook::MunmapReplacement> munmap_replacement_;
-extern HookList<MallocHook::MremapHook> mremap_hooks_;
-extern HookList<MallocHook::PreSbrkHook> presbrk_hooks_;
-extern HookList<MallocHook::SbrkHook> sbrk_hooks_;
-
-inline void MallocHook::InvokeNewHook(const void* ptr, size_t size) {
-  if (!absl::base_internal::new_hooks_.empty()) {
-    InvokeNewHookSlow(ptr, size);
-  }
-}
-
-inline void MallocHook::InvokeDeleteHook(const void* ptr) {
-  if (!absl::base_internal::delete_hooks_.empty()) {
-    InvokeDeleteHookSlow(ptr);
-  }
-}
-
-inline void MallocHook::InvokeSampledNewHook(
-    const SampledAlloc* sampled_alloc) {
-  if (!absl::base_internal::sampled_new_hooks_.empty()) {
-    InvokeSampledNewHookSlow(sampled_alloc);
-  }
-}
-
-inline void MallocHook::InvokeSampledDeleteHook(AllocHandle handle) {
-  if (!absl::base_internal::sampled_delete_hooks_.empty()) {
-    InvokeSampledDeleteHookSlow(handle);
-  }
-}
-
-inline void MallocHook::InvokePreMmapHook(const void* start,
-                                          size_t size,
-                                          int protection,
-                                          int flags,
-                                          int fd,
-                                          off_t offset) {
-  if (!absl::base_internal::premmap_hooks_.empty()) {
-    InvokePreMmapHookSlow(start, size, protection, flags, fd, offset);
-  }
-}
-
-inline void MallocHook::InvokeMmapHook(const void* result,
-                                       const void* start,
-                                       size_t size,
-                                       int protection,
-                                       int flags,
-                                       int fd,
-                                       off_t offset) {
-  if (!absl::base_internal::mmap_hooks_.empty()) {
-    InvokeMmapHookSlow(result, start, size, protection, flags, fd, offset);
-  }
-}
-
-inline bool MallocHook::InvokeMmapReplacement(const void* start,
-                                              size_t size,
-                                              int protection,
-                                              int flags,
-                                              int fd,
-                                              off_t offset,
-                                              void** result) {
-  if (!absl::base_internal::mmap_replacement_.empty()) {
-    return InvokeMmapReplacementSlow(start, size,
-                                     protection, flags,
-                                     fd, offset,
-                                     result);
-  }
-  return false;
-}
-
-inline void MallocHook::InvokeMunmapHook(const void* start, size_t size) {
-  if (!absl::base_internal::munmap_hooks_.empty()) {
-    InvokeMunmapHookSlow(start, size);
-  }
-}
-
-inline bool MallocHook::InvokeMunmapReplacement(
-    const void* start, size_t size, int* result) {
-  if (!absl::base_internal::mmap_replacement_.empty()) {
-    return InvokeMunmapReplacementSlow(start, size, result);
-  }
-  return false;
-}
-
-inline void MallocHook::InvokeMremapHook(const void* result,
-                                         const void* old_addr,
-                                         size_t old_size,
-                                         size_t new_size,
-                                         int flags,
-                                         const void* new_addr) {
-  if (!absl::base_internal::mremap_hooks_.empty()) {
-    InvokeMremapHookSlow(result, old_addr, old_size, new_size, flags, new_addr);
-  }
-}
-
-inline void MallocHook::InvokePreSbrkHook(ptrdiff_t increment) {
-  if (!absl::base_internal::presbrk_hooks_.empty() && increment != 0) {
-    InvokePreSbrkHookSlow(increment);
-  }
-}
-
-inline void MallocHook::InvokeSbrkHook(const void* result,
-                                       ptrdiff_t increment) {
-  if (!absl::base_internal::sbrk_hooks_.empty() && increment != 0) {
-    InvokeSbrkHookSlow(result, increment);
-  }
-}
-
-}  // namespace base_internal
-}  // namespace absl
-#endif  // ABSL_BASE_INTERNAL_MALLOC_HOOK_INVOKE_H_
diff --git a/absl/base/internal/malloc_hook_mmap_linux.inc b/absl/base/internal/malloc_hook_mmap_linux.inc
deleted file mode 100644
index b87621a6..00000000
--- a/absl/base/internal/malloc_hook_mmap_linux.inc
+++ /dev/null
@@ -1,168 +0,0 @@
-// Copyright 2017 The Abseil Authors.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//      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.
-//
-// We define mmap() and mmap64(), which somewhat reimplements libc's mmap
-// syscall stubs.  Unfortunately libc only exports the stubs via weak symbols
-// (which we're overriding with our mmap64() and mmap() wrappers) so we can't
-// just call through to them.
-
-#ifndef __linux__
-# error Should only be including malloc_hook_mmap_linux.h on linux systems.
-#endif
-
-#include <sys/mman.h>
-#include <sys/types.h>
-#ifdef __BIONIC__
-#include <sys/syscall.h>
-#else
-#include <syscall.h>
-#endif
-
-#include <linux/unistd.h>
-#include <unistd.h>
-#include <cerrno>
-#include <cstdarg>
-#include <cstdint>
-
-#include "absl/base/internal/direct_mmap.h"
-
-// SYS_mremap is not defined in Android.
-#ifdef __BIONIC__
-#ifndef SYS_mremap
-#define SYS_mremap __NR_mremap
-#endif
-#endif  // __BIONIC__
-
-// We put MallocHook::InvokeMmapHook calls right into mmap and mmap64, so that
-// the stack frames in the caller's stack are at the same offsets for all the
-// calls of memory allocating functions.
-
-// Put all callers of MallocHook::Invoke* in this module into
-// malloc_hook section,
-// so that MallocHook::GetCallerStackTrace can function accurately:
-
-// Make sure mmap doesn't get #define'd away by <sys/mman.h>
-# undef mmap
-
-extern "C" {
-ABSL_ATTRIBUTE_SECTION(malloc_hook)
-void* mmap64(void* start, size_t length, int prot, int flags, int fd,
-             off64_t offset) __THROW;
-ABSL_ATTRIBUTE_SECTION(malloc_hook)
-void* mmap(void* start, size_t length, int prot, int flags, int fd,
-           off_t offset) __THROW;
-ABSL_ATTRIBUTE_SECTION(malloc_hook)
-int munmap(void* start, size_t length) __THROW;
-ABSL_ATTRIBUTE_SECTION(malloc_hook)
-void* mremap(void* old_addr, size_t old_size, size_t new_size, int flags,
-             ...) __THROW;
-ABSL_ATTRIBUTE_SECTION(malloc_hook) void* sbrk(ptrdiff_t increment) __THROW;
-}
-
-extern "C" void* mmap64(void *start, size_t length, int prot, int flags,
-                        int fd, off64_t offset) __THROW {
-  absl::base_internal::MallocHook::InvokePreMmapHook(start, length, prot, flags,
-                                                     fd, offset);
-  void *result;
-  if (!absl::base_internal::MallocHook::InvokeMmapReplacement(
-          start, length, prot, flags, fd, offset, &result)) {
-    result = absl::base_internal::DirectMmap(start, length, prot, flags, fd,
-                                             offset);
-  }
-  absl::base_internal::MallocHook::InvokeMmapHook(result, start, length, prot,
-                                                  flags, fd, offset);
-  return result;
-}
-
-# if !defined(__USE_FILE_OFFSET64) || !defined(__REDIRECT_NTH)
-
-extern "C" void* mmap(void *start, size_t length, int prot, int flags,
-                      int fd, off_t offset) __THROW {
-  absl::base_internal::MallocHook::InvokePreMmapHook(start, length, prot, flags,
-                                                     fd, offset);
-  void *result;
-  if (!absl::base_internal::MallocHook::InvokeMmapReplacement(
-          start, length, prot, flags, fd, offset, &result)) {
-    result = absl::base_internal::DirectMmap(
-        start, length, prot, flags, fd,
-        static_cast<size_t>(offset)); // avoid sign extension
-  }
-  absl::base_internal::MallocHook::InvokeMmapHook(result, start, length, prot,
-                                                  flags, fd, offset);
-  return result;
-}
-
-# endif  // !defined(__USE_FILE_OFFSET64) || !defined(__REDIRECT_NTH)
-
-extern "C" int munmap(void* start, size_t length) __THROW {
-  absl::base_internal::MallocHook::InvokeMunmapHook(start, length);
-  int result;
-  if (!absl::base_internal::MallocHook::InvokeMunmapReplacement(start, length,
-                                                                &result)) {
-    result = absl::base_internal::DirectMunmap(start, length);
-  }
-  return result;
-}
-
-extern "C" void* mremap(void* old_addr, size_t old_size, size_t new_size,
-                        int flags, ...) __THROW {
-  va_list ap;
-  va_start(ap, flags);
-  void *new_address = va_arg(ap, void *);
-  va_end(ap);
-  void* result = reinterpret_cast<void*>(
-      syscall(SYS_mremap, old_addr, old_size, new_size, flags, new_address));
-  absl::base_internal::MallocHook::InvokeMremapHook(
-      result, old_addr, old_size, new_size, flags, new_address);
-  return result;
-}
-
-// sbrk cannot be intercepted on Android as there is no mechanism to
-// invoke the original sbrk (since there is no __sbrk as with glibc).
-#if !defined(__BIONIC__)
-// libc's version:
-extern "C" void* __sbrk(ptrdiff_t increment);
-
-extern "C" void* sbrk(ptrdiff_t increment) __THROW {
-  absl::base_internal::MallocHook::InvokePreSbrkHook(increment);
-  void *result = __sbrk(increment);
-  absl::base_internal::MallocHook::InvokeSbrkHook(result, increment);
-  return result;
-}
-#endif  // !defined(__BIONIC__)
-
-namespace absl {
-namespace base_internal {
-
-/*static*/void* MallocHook::UnhookedMMap(void *start, size_t length, int prot,
-                                         int flags, int fd, off_t offset) {
-  void* result;
-  if (!MallocHook::InvokeMmapReplacement(
-          start, length, prot, flags, fd, offset, &result)) {
-    result = absl::base_internal::DirectMmap(start, length, prot, flags, fd,
-                                             offset);
-  }
-  return result;
-}
-
-/*static*/int MallocHook::UnhookedMUnmap(void *start, size_t length) {
-  int result;
-  if (!MallocHook::InvokeMunmapReplacement(start, length, &result)) {
-    result = absl::base_internal::DirectMunmap(start, length);
-  }
-  return result;
-}
-
-}  // namespace base_internal
-}  // namespace absl
diff --git a/absl/container/fixed_array.h b/absl/container/fixed_array.h
index b92d9056..06bc8009 100644
--- a/absl/container/fixed_array.h
+++ b/absl/container/fixed_array.h
@@ -207,7 +207,7 @@ class FixedArray {
   // Overload of FixedArray::at() to return a const reference to the ith element
   // of the fixed array.
   const_reference at(size_type i) const {
-    if (i >= size()) {
+    if (ABSL_PREDICT_FALSE(i >= size())) {
       base_internal::ThrowStdOutOfRange("FixedArray::at failed bounds check");
     }
     return data()[i];
diff --git a/absl/container/inlined_vector_test.cc b/absl/container/inlined_vector_test.cc
index 0e39855b..26a7d5bc 100644
--- a/absl/container/inlined_vector_test.cc
+++ b/absl/container/inlined_vector_test.cc
@@ -651,7 +651,7 @@ TEST(IntVec, AliasingCopyAssignment) {
     IntVec original;
     Fill(&original, len);
     IntVec dup = original;
-    dup = dup;
+    dup = *&dup;
     EXPECT_EQ(dup, original);
   }
 }
diff --git a/absl/debugging/BUILD.bazel b/absl/debugging/BUILD.bazel
index f6859093..8543200d 100644
--- a/absl/debugging/BUILD.bazel
+++ b/absl/debugging/BUILD.bazel
@@ -76,6 +76,24 @@ cc_test(
 )
 
 cc_library(
+    name = "examine_stack",
+    srcs = [
+        "internal/examine_stack.cc",
+    ],
+    hdrs = [
+        "internal/examine_stack.h",
+    ],
+    copts = ABSL_DEFAULT_COPTS,
+    visibility = ["//visibility:private"],
+    deps = [
+        ":stacktrace",
+        ":symbolize",
+        "//absl/base",
+        "//absl/base:core_headers",
+    ],
+)
+
+cc_library(
     name = "debugging_internal",
     srcs = [
         "internal/address_is_readable.cc",
@@ -234,11 +252,11 @@ cc_library(
     srcs = ["internal/stack_consumption.cc"],
     hdrs = ["internal/stack_consumption.h"],
     copts = ABSL_DEFAULT_COPTS,
+    visibility = ["//visibility:private"],
     deps = [
         "//absl/base",
         "//absl/base:core_headers",
     ],
-    visibility = ["//visibility:private"],
 )
 
 cc_test(
diff --git a/absl/debugging/CMakeLists.txt b/absl/debugging/CMakeLists.txt
index b9aec5fa..8d2ec845 100644
--- a/absl/debugging/CMakeLists.txt
+++ b/absl/debugging/CMakeLists.txt
@@ -25,6 +25,7 @@ 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"
@@ -49,6 +50,12 @@ list(APPEND SYMBOLIZE_SRC
   ${DEBUGGING_INTERNAL_HEADERS}
 )
 
+list(APPEND EXAMINE_STACK_SRC
+  "internal/examine_stack.cc"
+  ${DEBUGGING_PUBLIC_HEADERS}
+  ${DEBUGGING_INTERNAL_HEADERS}
+)
+
 absl_library(
   TARGET
     absl_stacktrace
@@ -67,6 +74,17 @@ absl_library(
     symbolize
 )
 
+# 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
+)
+
 list(APPEND LEAK_CHECK_SRC
   "leak_check.cc"
 )
diff --git a/absl/debugging/internal/examine_stack.cc b/absl/debugging/internal/examine_stack.cc
new file mode 100644
index 00000000..261daae9
--- /dev/null
+++ b/absl/debugging/internal/examine_stack.cc
@@ -0,0 +1,147 @@
+//
+// 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/debugging/internal/examine_stack.h"
+
+#ifndef _WIN32
+#include <unistd.h>
+#endif
+
+#include <csignal>
+#include <cstdio>
+
+#include "absl/base/attributes.h"
+#include "absl/base/internal/raw_logging.h"
+#include "absl/base/macros.h"
+#include "absl/debugging/stacktrace.h"
+#include "absl/debugging/symbolize.h"
+
+namespace absl {
+namespace debugging_internal {
+
+// Returns the program counter from signal context, nullptr if
+// unknown. vuc is a ucontext_t*. We use void* to avoid the use of
+// ucontext_t on non-POSIX systems.
+void* GetProgramCounter(void* vuc) {
+#ifdef __linux__
+  if (vuc != nullptr) {
+    ucontext_t* context = reinterpret_cast<ucontext_t*>(vuc);
+#if defined(__aarch64__)
+    return reinterpret_cast<void*>(context->uc_mcontext.pc);
+#elif defined(__arm__)
+    return reinterpret_cast<void*>(context->uc_mcontext.arm_pc);
+#elif defined(__i386__)
+    if (14 < ABSL_ARRAYSIZE(context->uc_mcontext.gregs))
+      return reinterpret_cast<void*>(context->uc_mcontext.gregs[14]);
+#elif defined(__powerpc64__)
+    return reinterpret_cast<void*>(context->uc_mcontext.gp_regs[32]);
+#elif defined(__powerpc__)
+    return reinterpret_cast<void*>(context->uc_mcontext.regs->nip);
+#elif defined(__x86_64__)
+    if (16 < ABSL_ARRAYSIZE(context->uc_mcontext.gregs))
+      return reinterpret_cast<void*>(context->uc_mcontext.gregs[16]);
+#else
+#error "Undefined Architecture."
+#endif
+  }
+#elif defined(__akaros__)
+  auto* ctx = reinterpret_cast<struct user_context*>(vuc);
+  return reinterpret_cast<void*>(get_user_ctx_pc(ctx));
+#endif
+  static_cast<void>(vuc);
+  return nullptr;
+}
+
+// The %p field width for printf() functions is two characters per byte,
+// and two extra for the leading "0x".
+static constexpr int kPrintfPointerFieldWidth = 2 + 2 * sizeof(void*);
+
+// Print a program counter, its stack frame size, and its symbol name.
+// Note that there is a separate symbolize_pc argument. Return addresses may be
+// at the end of the function, and this allows the caller to back up from pc if
+// appropriate.
+static void DumpPCAndFrameSizeAndSymbol(void (*writerfn)(const char*, void*),
+                                        void* writerfn_arg, void* pc,
+                                        void* symbolize_pc, int framesize,
+                                        const char* const prefix) {
+  char tmp[1024];
+  const char* symbol = "(unknown)";
+  if (absl::Symbolize(symbolize_pc, tmp, sizeof(tmp))) {
+    symbol = tmp;
+  }
+  char buf[1024];
+  if (framesize <= 0) {
+    snprintf(buf, sizeof(buf), "%s@ %*p  (unknown)  %s\n", prefix,
+             kPrintfPointerFieldWidth, pc, symbol);
+  } else {
+    snprintf(buf, sizeof(buf), "%s@ %*p  %9d  %s\n", prefix,
+             kPrintfPointerFieldWidth, pc, framesize, symbol);
+  }
+  writerfn(buf, writerfn_arg);
+}
+
+// Print a program counter and the corresponding stack frame size.
+static void DumpPCAndFrameSize(void (*writerfn)(const char*, void*),
+                               void* writerfn_arg, void* pc, int framesize,
+                               const char* const prefix) {
+  char buf[100];
+  if (framesize <= 0) {
+    snprintf(buf, sizeof(buf), "%s@ %*p  (unknown)\n", prefix,
+             kPrintfPointerFieldWidth, pc);
+  } else {
+    snprintf(buf, sizeof(buf), "%s@ %*p  %9d\n", prefix,
+             kPrintfPointerFieldWidth, pc, framesize);
+  }
+  writerfn(buf, writerfn_arg);
+}
+
+void DumpPCAndFrameSizesAndStackTrace(
+    void* pc, void* const stack[], int frame_sizes[], int depth,
+    int min_dropped_frames, bool symbolize_stacktrace,
+    void (*writerfn)(const char*, void*), void* writerfn_arg) {
+  if (pc != nullptr) {
+    // We don't know the stack frame size for PC, use 0.
+    if (symbolize_stacktrace) {
+      DumpPCAndFrameSizeAndSymbol(writerfn, writerfn_arg, pc, pc, 0, "PC: ");
+    } else {
+      DumpPCAndFrameSize(writerfn, writerfn_arg, pc, 0, "PC: ");
+    }
+  }
+  for (int i = 0; i < depth; i++) {
+    if (symbolize_stacktrace) {
+      // Pass the previous address of pc as the symbol address because pc is a
+      // return address, and an overrun may occur when the function ends with a
+      // call to a function annotated noreturn (e.g. CHECK). Note that we don't
+      // do this for pc above, as the adjustment is only correct for return
+      // addresses.
+      DumpPCAndFrameSizeAndSymbol(writerfn, writerfn_arg, stack[i],
+                                  reinterpret_cast<char*>(stack[i]) - 1,
+                                  frame_sizes[i], "    ");
+    } else {
+      DumpPCAndFrameSize(writerfn, writerfn_arg, stack[i], frame_sizes[i],
+                         "    ");
+    }
+  }
+  if (min_dropped_frames > 0) {
+    char buf[100];
+    snprintf(buf, sizeof(buf), "    @ ... and at least %d more frames\n",
+             min_dropped_frames);
+    writerfn(buf, writerfn_arg);
+  }
+}
+
+}  // namespace debugging_internal
+}  // namespace absl
diff --git a/absl/debugging/internal/examine_stack.h b/absl/debugging/internal/examine_stack.h
new file mode 100644
index 00000000..a16c03b2
--- /dev/null
+++ b/absl/debugging/internal/examine_stack.h
@@ -0,0 +1,38 @@
+//
+// 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.
+//
+
+#ifndef ABSL_DEBUGGING_INTERNAL_EXAMINE_STACK_H_
+#define ABSL_DEBUGGING_INTERNAL_EXAMINE_STACK_H_
+
+namespace absl {
+namespace debugging_internal {
+
+// Returns the program counter from signal context, or nullptr if
+// unknown. `vuc` is a ucontext_t*. We use void* to avoid the use of
+// ucontext_t on non-POSIX systems.
+void* GetProgramCounter(void* vuc);
+
+// Uses `writerfn` to dump the program counter, stack trace, and stack
+// frame sizes.
+void DumpPCAndFrameSizesAndStackTrace(
+    void* pc, void* const stack[], int frame_sizes[], int depth,
+    int min_dropped_frames, bool symbolize_stacktrace,
+    void (*writerfn)(const char*, void*), void* writerfn_arg);
+
+}  // namespace debugging_internal
+}  // namespace absl
+
+#endif  // ABSL_DEBUGGING_INTERNAL_EXAMINE_STACK_H_
diff --git a/absl/strings/string_view.h b/absl/strings/string_view.h
index ddc89341..9162bb33 100644
--- a/absl/strings/string_view.h
+++ b/absl/strings/string_view.h
@@ -168,13 +168,13 @@ class string_view {
   string_view(  // NOLINT(runtime/explicit)
       const std::basic_string<char, std::char_traits<char>, Allocator>&
           str) noexcept
-      : ptr_(str.data()), length_(str.size()) {}
+      : ptr_(str.data()), length_(CheckLengthInternal(str.size())) {}
 
   // Implicit constructor of a `string_view` from nul-terminated `str`. When
   // accepting possibly null strings, use `absl::NullSafeStringView(str)`
   // instead (see below).
   constexpr string_view(const char* str)  // NOLINT(runtime/explicit)
-      : ptr_(str), length_(StrLenInternal(str)) {}
+      : ptr_(str), length_(CheckLengthInternal(StrLenInternal(str))) {}
 
   // Implicit constructor of a `string_view` from a `const char*` and length.
   constexpr string_view(const char* data, size_type len)
@@ -479,7 +479,7 @@ class string_view {
 
  private:
   static constexpr size_type kMaxSize =
-      std::numeric_limits<size_type>::max() / 2 + 1;
+      std::numeric_limits<difference_type>::max();
 
   // check whether __builtin_strlen is provided by the compiler.
   // GCC doesn't have __has_builtin()
diff --git a/absl/strings/string_view_test.cc b/absl/strings/string_view_test.cc
index 3077d240..a26f6c3a 100644
--- a/absl/strings/string_view_test.cc
+++ b/absl/strings/string_view_test.cc
@@ -1068,6 +1068,17 @@ TEST(HugeStringView, TwoPointTwoGB) {
 TEST(NonNegativeLenTest, NonNegativeLen) {
   EXPECT_DEATH_IF_SUPPORTED(absl::string_view("xyz", -1), "len <= kMaxSize");
 }
+
+TEST(LenExceedsMaxSizeTest, LenExceedsMaxSize) {
+  auto max_size = absl::string_view().max_size();
+
+  // This should construct ok (although the view itself is obviously invalid).
+  absl::string_view ok_view("", max_size);
+
+  // Adding one to the max should trigger an assertion.
+  EXPECT_DEATH_IF_SUPPORTED(absl::string_view("", max_size + 1),
+                            "len <= kMaxSize");
+}
 #endif  // !defined(NDEBUG) && !defined(ABSL_HAVE_STD_STRING_VIEW)
 
 class StringViewStreamTest : public ::testing::Test {
diff --git a/absl/synchronization/BUILD.bazel b/absl/synchronization/BUILD.bazel
index 354291f2..69f9c81f 100644
--- a/absl/synchronization/BUILD.bazel
+++ b/absl/synchronization/BUILD.bazel
@@ -75,7 +75,6 @@ cc_library(
         "//absl/base:config",
         "//absl/base:core_headers",
         "//absl/base:dynamic_annotations",
-        "//absl/base:malloc_extension",
         "//absl/base:malloc_internal",
         "//absl/debugging:stacktrace",
         "//absl/time",
@@ -168,7 +167,6 @@ cc_library(
     deps = [
         ":synchronization",
         "//absl/base",
-        "//absl/base:malloc_extension",
         "//absl/strings",
         "//absl/time",
         "@com_google_googletest//:gtest",
@@ -184,7 +182,6 @@ cc_test(
         ":per_thread_sem_test_common",
         ":synchronization",
         "//absl/base",
-        "//absl/base:malloc_extension",
         "//absl/strings",
         "//absl/time",
         "@com_google_googletest//:gtest_main",
diff --git a/absl/synchronization/CMakeLists.txt b/absl/synchronization/CMakeLists.txt
index c5c4c626..c8f84faf 100644
--- a/absl/synchronization/CMakeLists.txt
+++ b/absl/synchronization/CMakeLists.txt
@@ -44,7 +44,7 @@ list(APPEND SYNCHRONIZATION_SRC
   "notification.cc"
   "mutex.cc"
 )
-set(SYNCHRONIZATION_PUBLIC_LIBRARIES absl::base absl_malloc_extension absl::time)
+set(SYNCHRONIZATION_PUBLIC_LIBRARIES absl::base absl::time)
 
 absl_library(
   TARGET
diff --git a/absl/synchronization/internal/per_thread_sem.cc b/absl/synchronization/internal/per_thread_sem.cc
index af872228..caa2baf6 100644
--- a/absl/synchronization/internal/per_thread_sem.cc
+++ b/absl/synchronization/internal/per_thread_sem.cc
@@ -21,7 +21,6 @@
 #include <atomic>
 
 #include "absl/base/attributes.h"
-#include "absl/base/internal/malloc_extension.h"
 #include "absl/base/internal/thread_identity.h"
 #include "absl/synchronization/internal/waiter.h"
 
@@ -90,12 +89,6 @@ ABSL_ATTRIBUTE_WEAK bool AbslInternalPerThreadSemWait(
   if (identity->blocked_count_ptr != nullptr) {
     identity->blocked_count_ptr->fetch_sub(1, std::memory_order_relaxed);
   }
-
-  if (identity->is_idle.load(std::memory_order_relaxed)) {
-    // We became idle during the wait; become non-idle again so that
-    // performance of deallocations done from now on does not suffer.
-    absl::base_internal::MallocExtension::instance()->MarkThreadBusy();
-  }
   identity->is_idle.store(false, std::memory_order_relaxed);
   identity->wait_start.store(0, std::memory_order_relaxed);
   return !timeout;
diff --git a/absl/synchronization/internal/per_thread_sem_test.cc b/absl/synchronization/internal/per_thread_sem_test.cc
index 61296cfc..2b52ea76 100644
--- a/absl/synchronization/internal/per_thread_sem_test.cc
+++ b/absl/synchronization/internal/per_thread_sem_test.cc
@@ -24,7 +24,6 @@
 
 #include "gtest/gtest.h"
 #include "absl/base/internal/cycleclock.h"
-#include "absl/base/internal/malloc_extension.h"
 #include "absl/base/internal/thread_identity.h"
 #include "absl/strings/str_cat.h"
 #include "absl/time/clock.h"
@@ -167,79 +166,6 @@ TEST_F(PerThreadSemTest, Timeouts) {
   EXPECT_TRUE(Wait(negative_timeout));
 }
 
-// Test that idle threads properly register themselves as such with malloc.
-TEST_F(PerThreadSemTest, Idle) {
-  // We can't use gmock because it might use synch calls.  So we do it
-  // by hand, messily.  I don't bother hitting every one of the
-  // MallocExtension calls because most of them won't get made
-  // anyway--if they do we can add them.
-  class MockMallocExtension : public base_internal::MallocExtension {
-   public:
-    MockMallocExtension(base_internal::MallocExtension *real,
-                        base_internal::ThreadIdentity *id,
-                        std::atomic<int> *idles, std::atomic<int> *busies)
-        : real_(real), id_(id), idles_(idles), busies_(busies) {}
-    void MarkThreadIdle() override {
-      if (base_internal::CurrentThreadIdentityIfPresent() != id_) {
-        return;
-      }
-      idles_->fetch_add(1, std::memory_order_relaxed);
-    }
-
-    void MarkThreadBusy() override {
-      if (base_internal::CurrentThreadIdentityIfPresent() != id_) {
-        return;
-      }
-      busies_->fetch_add(1, std::memory_order_relaxed);
-    }
-    size_t GetAllocatedSize(const void* p) override {
-      return real_->GetAllocatedSize(p);
-    }
-
-   private:
-    MallocExtension *real_;
-    base_internal::ThreadIdentity *id_;
-    std::atomic<int>* idles_;
-    std::atomic<int>* busies_;
-  };
-
-  base_internal::ThreadIdentity *id = GetOrCreateCurrentThreadIdentity();
-  std::atomic<int> idles(0);
-  std::atomic<int> busies(0);
-  base_internal::MallocExtension *old =
-      base_internal::MallocExtension::instance();
-  MockMallocExtension mock(old, id, &idles, &busies);
-  base_internal::MallocExtension::Register(&mock);
-  std::atomic<int> sync(0);
-
-  std::thread t([id, &idles, &sync]() {
-    // Wait for the main thread to begin the wait process
-    while (0 == sync.load(std::memory_order_relaxed)) {
-      SleepFor(absl::Milliseconds(1));
-    }
-    // Wait for main thread to become idle, then wake it
-    // pretend time is passing--enough of these should cause an idling.
-    for (int i = 0; i < 100; ++i) {
-      Tick(id);
-    }
-    while (0 == idles.load(std::memory_order_relaxed)) {
-      // Keep ticking, just in case.
-      Tick(id);
-      SleepFor(absl::Milliseconds(1));
-    }
-    Post(id);
-  });
-
-  idles.store(0, std::memory_order_relaxed);  // In case we slept earlier.
-  sync.store(1, std::memory_order_relaxed);
-  Wait(KernelTimeout::Never());
-
-  // t will wake us once we become idle.
-  EXPECT_LT(0, busies.load(std::memory_order_relaxed));
-  t.join();
-  base_internal::MallocExtension::Register(old);
-}
-
 }  // namespace
 
 }  // namespace synchronization_internal
diff --git a/absl/synchronization/internal/waiter.cc b/absl/synchronization/internal/waiter.cc
index db1b54f6..768c5208 100644
--- a/absl/synchronization/internal/waiter.cc
+++ b/absl/synchronization/internal/waiter.cc
@@ -40,8 +40,6 @@
 #include <atomic>
 #include <cassert>
 #include <cstdint>
-
-#include "absl/base/internal/malloc_extension.h"
 #include "absl/base/internal/raw_logging.h"
 #include "absl/base/internal/thread_identity.h"
 #include "absl/base/optimization.h"
@@ -59,7 +57,6 @@ static void MaybeBecomeIdle() {
   const int wait_start = identity->wait_start.load(std::memory_order_relaxed);
   if (!is_idle && ticker - wait_start > Waiter::kIdlePeriods) {
     identity->is_idle.store(true, std::memory_order_relaxed);
-    base_internal::MallocExtension::instance()->MarkThreadIdle();
   }
 }
 
diff --git a/absl/time/duration.cc b/absl/time/duration.cc
index 108fa490..82b4d989 100644
--- a/absl/time/duration.cc
+++ b/absl/time/duration.cc
@@ -174,8 +174,10 @@ inline Duration MakeDurationFromU128(uint128 u128, bool is_neg) {
 // name intN_t designates a signed integer type with width N, no padding
 // bits, and a two's complement representation." So, we can convert to
 // and from the corresponding uint64_t value using a bit cast.
-inline uint64_t EncodeTwosComp(int64_t v) { return bit_cast<uint64_t>(v); }
-inline int64_t DecodeTwosComp(uint64_t v) { return bit_cast<int64_t>(v); }
+inline uint64_t EncodeTwosComp(int64_t v) {
+  return absl::bit_cast<uint64_t>(v);
+}
+inline int64_t DecodeTwosComp(uint64_t v) { return absl::bit_cast<int64_t>(v); }
 
 // Note: The overflow detection in this function is done using greater/less *or
 // equal* because kint64max/min is too large to be represented exactly in a
diff --git a/absl/types/any_exception_safety_test.cc b/absl/types/any_exception_safety_test.cc
index f4ca52eb..82c176b5 100644
--- a/absl/types/any_exception_safety_test.cc
+++ b/absl/types/any_exception_safety_test.cc
@@ -21,15 +21,21 @@
 #include "absl/base/internal/exception_safety_testing.h"
 
 using Thrower = absl::ThrowingValue<>;
+using NoThrowMoveThrower =
+    absl::ThrowingValue<absl::NoThrow::kMoveCtor | absl::NoThrow::kMoveAssign>;
 using ThrowerList = std::initializer_list<Thrower>;
 using ThrowerVec = std::vector<Thrower>;
 using ThrowingAlloc = absl::ThrowingAllocator<Thrower>;
 using ThrowingThrowerVec = std::vector<Thrower, ThrowingAlloc>;
 
-namespace absl {
+namespace {
+
+class AnyExceptionSafety : public ::testing::Test {
+ private:
+  absl::ConstructorTracker inspector_;
+};
 
-testing::AssertionResult AbslCheckInvariants(absl::any* a,
-                                             InternalAbslNamespaceFinder) {
+testing::AssertionResult AnyInvariants(absl::any* a) {
   using testing::AssertionFailure;
   using testing::AssertionSuccess;
 
@@ -69,17 +75,10 @@ testing::AssertionResult AbslCheckInvariants(absl::any* a,
   return AssertionSuccess();
 }
 
-}  // namespace absl
-
-namespace {
-
-class AnyExceptionSafety : public ::testing::Test {
- private:
-  absl::ConstructorTracker inspector_;
-};
-
 testing::AssertionResult AnyIsEmpty(absl::any* a) {
-  if (!a->has_value()) return testing::AssertionSuccess();
+  if (!a->has_value()) {
+    return testing::AssertionSuccess();
+  }
   return testing::AssertionFailure()
          << "a should be empty, but instead has value "
          << absl::any_cast<Thrower>(*a).Get();
@@ -100,101 +99,70 @@ TEST_F(AnyExceptionSafety, Ctors) {
           absl::in_place_type_t<ThrowingThrowerVec>(), {val}, ThrowingAlloc());
 }
 
-struct OneFactory {
-  std::unique_ptr<absl::any> operator()() const {
-    return absl::make_unique<absl::any>(absl::in_place_type_t<Thrower>(), 1,
-                                        absl::no_throw_ctor);
-  }
-};
-
-struct EmptyFactory {
-  std::unique_ptr<absl::any> operator()() const {
-    return absl::make_unique<absl::any>();
-  }
-};
-
 TEST_F(AnyExceptionSafety, Assignment) {
-  auto thrower_comp = [](const absl::any& l, const absl::any& r) {
-    return absl::any_cast<Thrower>(l) == absl::any_cast<Thrower>(r);
+  auto original =
+      absl::any(absl::in_place_type_t<Thrower>(), 1, absl::no_throw_ctor);
+  auto any_is_strong = [original](absl::any* ap) {
+    return testing::AssertionResult(ap->has_value() &&
+                                    absl::any_cast<Thrower>(original) ==
+                                        absl::any_cast<Thrower>(*ap));
   };
+  auto any_strong_tester = absl::MakeExceptionSafetyTester()
+                               .WithInitialValue(original)
+                               .WithInvariants(AnyInvariants, any_is_strong);
 
-  OneFactory one_factory;
-
-  absl::ThrowingValue<absl::NoThrow::kMoveCtor | absl::NoThrow::kMoveAssign>
-      moveable_val(2);
   Thrower val(2);
   absl::any any_val(val);
+  NoThrowMoveThrower mv_val(2);
 
-  EXPECT_TRUE(absl::TestExceptionSafety(
-      one_factory, [&any_val](absl::any* ap) { *ap = any_val; },
-      absl::StrongGuarantee(one_factory, thrower_comp)));
-
-  EXPECT_TRUE(absl::TestExceptionSafety(
-      one_factory, [&val](absl::any* ap) { *ap = val; },
-      absl::StrongGuarantee(one_factory, thrower_comp)));
-
-  EXPECT_TRUE(absl::TestExceptionSafety(
-      one_factory, [&val](absl::any* ap) { *ap = std::move(val); },
-      absl::StrongGuarantee(one_factory, thrower_comp)));
+  auto assign_any = [&any_val](absl::any* ap) { *ap = any_val; };
+  auto assign_val = [&val](absl::any* ap) { *ap = val; };
+  auto move = [&val](absl::any* ap) { *ap = std::move(val); };
+  auto move_movable = [&mv_val](absl::any* ap) { *ap = std::move(mv_val); };
 
-  EXPECT_TRUE(absl::TestExceptionSafety(
-      one_factory,
-      [&moveable_val](absl::any* ap) { *ap = std::move(moveable_val); },
-      absl::StrongGuarantee(one_factory, thrower_comp)));
+  EXPECT_TRUE(any_strong_tester.Test(assign_any));
+  EXPECT_TRUE(any_strong_tester.Test(assign_val));
+  EXPECT_TRUE(any_strong_tester.Test(move));
+  EXPECT_TRUE(any_strong_tester.Test(move_movable));
 
-  EmptyFactory empty_factory;
-  auto empty_comp = [](const absl::any& l, const absl::any& r) {
-    return !(l.has_value() || r.has_value());
+  auto empty_any_is_strong = [](absl::any* ap) {
+    return testing::AssertionResult{!ap->has_value()};
   };
-
-  EXPECT_TRUE(absl::TestExceptionSafety(
-      empty_factory, [&any_val](absl::any* ap) { *ap = any_val; },
-      absl::StrongGuarantee(empty_factory, empty_comp)));
-
-  EXPECT_TRUE(absl::TestExceptionSafety(
-      empty_factory, [&val](absl::any* ap) { *ap = val; },
-      absl::StrongGuarantee(empty_factory, empty_comp)));
-
-  EXPECT_TRUE(absl::TestExceptionSafety(
-      empty_factory, [&val](absl::any* ap) { *ap = std::move(val); },
-      absl::StrongGuarantee(empty_factory, empty_comp)));
+  auto strong_empty_any_tester =
+      absl::MakeExceptionSafetyTester()
+          .WithInitialValue(absl::any{})
+          .WithInvariants(AnyInvariants, empty_any_is_strong);
+
+  EXPECT_TRUE(strong_empty_any_tester.Test(assign_any));
+  EXPECT_TRUE(strong_empty_any_tester.Test(assign_val));
+  EXPECT_TRUE(strong_empty_any_tester.Test(move));
 }
 // libstdc++ std::any fails this test
 #if !defined(ABSL_HAVE_STD_ANY)
 TEST_F(AnyExceptionSafety, Emplace) {
-  OneFactory one_factory;
-
-  EXPECT_TRUE(absl::TestExceptionSafety(
-      one_factory, [](absl::any* ap) { ap->emplace<Thrower>(2); }, AnyIsEmpty));
-
-  EXPECT_TRUE(absl::TestExceptionSafety(
-      one_factory,
-      [](absl::any* ap) {
-        ap->emplace<absl::ThrowingValue<absl::NoThrow::kMoveCtor |
-                                        absl::NoThrow::kMoveAssign>>(2);
-      },
-      AnyIsEmpty));
-
-  EXPECT_TRUE(absl::TestExceptionSafety(one_factory,
-                                        [](absl::any* ap) {
-                                          std::initializer_list<Thrower> il{
-                                              Thrower(2, absl::no_throw_ctor)};
-                                          ap->emplace<ThrowerVec>(il);
-                                        },
-                                        AnyIsEmpty));
-
-  EmptyFactory empty_factory;
-  EXPECT_TRUE(absl::TestExceptionSafety(
-      empty_factory, [](absl::any* ap) { ap->emplace<Thrower>(2); },
-      AnyIsEmpty));
-
-  EXPECT_TRUE(absl::TestExceptionSafety(empty_factory,
-                                        [](absl::any* ap) {
-                                          std::initializer_list<Thrower> il{
-                                              Thrower(2, absl::no_throw_ctor)};
-                                          ap->emplace<ThrowerVec>(il);
-                                        },
-                                        AnyIsEmpty));
+  auto initial_val =
+      absl::any{absl::in_place_type_t<Thrower>(), 1, absl::no_throw_ctor};
+  auto one_tester = absl::MakeExceptionSafetyTester()
+                        .WithInitialValue(initial_val)
+                        .WithInvariants(AnyInvariants, AnyIsEmpty);
+
+  auto emp_thrower = [](absl::any* ap) { ap->emplace<Thrower>(2); };
+  auto emp_throwervec = [](absl::any* ap) {
+    std::initializer_list<Thrower> il{Thrower(2, absl::no_throw_ctor)};
+    ap->emplace<ThrowerVec>(il);
+  };
+  auto emp_movethrower = [](absl::any* ap) {
+    ap->emplace<NoThrowMoveThrower>(2);
+  };
+
+  EXPECT_TRUE(one_tester.Test(emp_thrower));
+  EXPECT_TRUE(one_tester.Test(emp_throwervec));
+  EXPECT_TRUE(one_tester.Test(emp_movethrower));
+
+  auto empty_tester = one_tester.WithInitialValue(absl::any{});
+
+  EXPECT_TRUE(empty_tester.Test(emp_thrower));
+  EXPECT_TRUE(empty_tester.Test(emp_throwervec));
 }
 #endif  // ABSL_HAVE_STD_ANY
 
diff --git a/absl/types/any_test.cc b/absl/types/any_test.cc
index 23aa3a58..115e78df 100644
--- a/absl/types/any_test.cc
+++ b/absl/types/any_test.cc
@@ -553,7 +553,7 @@ TEST(AnyTest, Move) {
   absl::any tmp4(4);
   absl::any o4(std::move(tmp4));  // move construct
   EXPECT_EQ(4, absl::any_cast<int>(o4));
-  o4 = o4;  // self assign
+  o4 = *&o4;  // self assign
   EXPECT_EQ(4, absl::any_cast<int>(o4));
   EXPECT_TRUE(o4.has_value());
 
diff --git a/absl/types/span.h b/absl/types/span.h
index d1ef97a2..6ba46685 100644
--- a/absl/types/span.h
+++ b/absl/types/span.h
@@ -216,7 +216,7 @@ using EnableIfConvertibleToSpanConst =
 //   // Construct a Span implicitly from a container
 //   void MyRoutine(absl::Span<const int> a) {
 //     ...
-//   };
+//   }
 //   std::vector v = {1,2,3,4,5};
 //   MyRoutine(v)                     // convert to Span<const T>
 //
@@ -235,7 +235,7 @@ using EnableIfConvertibleToSpanConst =
 //
 //   void MyRoutine(absl::Span<const int> a) {
 //     ...
-//   };
+//   }
 //
 //   std::vector v = {1,2,3,4,5};
 //   MyRoutine(v);