Export of internal Abseil changes

-- c99f979ad34f155fbeeea69b88bdc7458d89a21c by Derek Mauro <dmauro@google.com>: Remove a floating point division by zero test. This isn't testing behavior related to the library, and MSVC warns about it in opt mode. PiperOrigin-RevId: 285220804 -- 68b015491f0dbf1ab547994673281abd1f34cd4b by Gennadiy Rozental <rogeeff@google.com>: This CL introduces following changes to the class FlagImpl: * We eliminate the CommandLineFlagLocks struct. Instead callback guard and callback function are combined into a single CallbackData struct, while primary data lock is stored separately. * CallbackData member of class FlagImpl is initially set to be nullptr and is only allocated and initialized when a flag's callback is being set. For most flags we do not pay for the extra space and extra absl::Mutex now. * Primary data guard is stored in data_guard_ data member. This is a properly aligned character buffer of necessary size. During initialization of the flag we construct absl::Mutex in this space using placement new call. * We now avoid extra value copy after successful attempt to parse value out of string. Instead we swap flag's current value with tentative value we just produced. PiperOrigin-RevId: 285132636 -- ed45d118fb818969eb13094cf7827c885dfc562c by Tom Manshreck <shreck@google.com>: Change null-term* (and nul-term*) to NUL-term* in comments PiperOrigin-RevId: 285036610 -- 729619017944db895ce8d6d29c1995aa2e5628a5 by Derek Mauro <dmauro@google.com>: Use the Posix implementation of thread identity on MinGW. Some versions of MinGW suffer from thread_local bugs. PiperOrigin-RevId: 285022920 -- 39a25493503c76885bc3254c28f66a251c5b5bb0 by Greg Falcon <gfalcon@google.com>: Implementation detail change. Add further ABSL_NAMESPACE_BEGIN and _END annotation macros to files in Abseil. PiperOrigin-RevId: 285012012 GitOrigin-RevId: c99f979ad34f155fbeeea69b88bdc7458d89a21c Change-Id: I4c85d3704e45d11a9ac50d562f39640a6adbedc1
author: Abseil Team <absl-team@google.com> 2019-12-12T18·36-0800
committer: Matt Calabrese <calabrese@x.team> 2019-12-12T20·37-0500
commit: 12bc53e0318d80569270a5b26ccbc62b52022b89 (patch)
tree: 703f7dd5e7fdea7db3eefe317b10b1f67ddd8212 /absl
parent: 1e39f8626a4dadec1f56920b999dd4c3cfae333e (diff)
339 files changed, 949 insertions, 83 deletions
diff --git a/absl/algorithm/BUILD.bazel b/absl/algorithm/BUILD.bazel
index 2ee8c09e6268..6a96420b96a3 100644
--- a/absl/algorithm/BUILD.bazel
+++ b/absl/algorithm/BUILD.bazel
@@ -31,6 +31,7 @@ cc_library(
     hdrs = ["algorithm.h"],
     copts = ABSL_DEFAULT_COPTS,
     linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = ["//absl/base:config"],
 )
 
 cc_test(
diff --git a/absl/algorithm/CMakeLists.txt b/absl/algorithm/CMakeLists.txt
index 9fbe36f698f0..56cd0fb85b50 100644
--- a/absl/algorithm/CMakeLists.txt
+++ b/absl/algorithm/CMakeLists.txt
@@ -21,6 +21,8 @@ absl_cc_library(
     "algorithm.h"
   COPTS
     ${ABSL_DEFAULT_COPTS}
+  DEPS
+    absl::config
   PUBLIC
 )
 
diff --git a/absl/algorithm/algorithm.h b/absl/algorithm/algorithm.h
index 771228a0201e..e9b473387278 100644
--- a/absl/algorithm/algorithm.h
+++ b/absl/algorithm/algorithm.h
@@ -26,7 +26,10 @@
 #include <iterator>
 #include <type_traits>
 
+#include "absl/base/config.h"
+
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 namespace algorithm_internal {
 
@@ -150,6 +153,7 @@ ForwardIterator rotate(ForwardIterator first, ForwardIterator middle,
                    ForwardIterator>());
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_ALGORITHM_ALGORITHM_H_
diff --git a/absl/algorithm/container.h b/absl/algorithm/container.h
index 5dae9fd6a336..d72532decf38 100644
--- a/absl/algorithm/container.h
+++ b/absl/algorithm/container.h
@@ -55,6 +55,7 @@
 #include "absl/meta/type_traits.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_algorithm_internal {
 
 // NOTE: it is important to defer to ADL lookup for building with C++ modules,
@@ -1720,6 +1721,7 @@ OutputIt c_partial_sum(const InputSequence& input, OutputIt output_first,
                           output_first, std::forward<BinaryOp>(op));
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_ALGORITHM_CONTAINER_H_
diff --git a/absl/base/internal/raw_logging.h b/absl/base/internal/raw_logging.h
index 12145c48f569..cff45058b3d5 100644
--- a/absl/base/internal/raw_logging.h
+++ b/absl/base/internal/raw_logging.h
@@ -154,7 +154,7 @@ using LogPrefixHook = bool (*)(absl::LogSeverity severity, const char* file,
 //
 // 'file' and 'line' are the file and line number where the ABSL_RAW_LOG macro
 // was located.
-// The null-terminated logged message lives in the buffer between 'buf_start'
+// The NUL-terminated logged message lives in the buffer between 'buf_start'
 // and 'buf_end'.  'prefix_end' points to the first non-prefix character of the
 // buffer (as written by the LogPrefixHook.)
 using AbortHook = void (*)(const char* file, int line, const char* buf_start,
diff --git a/absl/base/internal/thread_identity.h b/absl/base/internal/thread_identity.h
index a1aa45ff2e42..5dfd0715dc5d 100644
--- a/absl/base/internal/thread_identity.h
+++ b/absl/base/internal/thread_identity.h
@@ -209,7 +209,7 @@ void ClearCurrentThreadIdentity();
 #error ABSL_THREAD_IDENTITY_MODE cannot be direcly set
 #elif defined(ABSL_FORCE_THREAD_IDENTITY_MODE)
 #define ABSL_THREAD_IDENTITY_MODE ABSL_FORCE_THREAD_IDENTITY_MODE
-#elif defined(_WIN32)
+#elif defined(_WIN32) && !defined(__MINGW32__)
 #define ABSL_THREAD_IDENTITY_MODE ABSL_THREAD_IDENTITY_MODE_USE_CPP11
 #elif ABSL_PER_THREAD_TLS && defined(__GOOGLE_GRTE_VERSION__) && \
     (__GOOGLE_GRTE_VERSION__ >= 20140228L)
diff --git a/absl/container/BUILD.bazel b/absl/container/BUILD.bazel
index e60979b2a54f..1f7abe07ff07 100644
--- a/absl/container/BUILD.bazel
+++ b/absl/container/BUILD.bazel
@@ -141,6 +141,7 @@ cc_library(
     copts = ABSL_DEFAULT_COPTS,
     linkopts = ABSL_DEFAULT_LINKOPTS,
     visibility = ["//visibility:private"],
+    deps = ["//absl/base:config"],
 )
 
 cc_test(
@@ -478,6 +479,9 @@ cc_library(
     hdrs = ["internal/hashtable_debug_hooks.h"],
     copts = ABSL_DEFAULT_COPTS,
     linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        "//absl/base:config",
+    ],
 )
 
 cc_library(
@@ -521,6 +525,7 @@ cc_library(
     hdrs = ["internal/node_hash_policy.h"],
     copts = ABSL_DEFAULT_COPTS,
     linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = ["//absl/base:config"],
 )
 
 cc_test(
@@ -662,6 +667,9 @@ cc_library(
     hdrs = ["internal/tracked.h"],
     copts = ABSL_TEST_COPTS,
     linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        "//absl/base:config",
+    ],
 )
 
 cc_library(
diff --git a/absl/container/CMakeLists.txt b/absl/container/CMakeLists.txt
index aa33659b322a..a931f3341662 100644
--- a/absl/container/CMakeLists.txt
+++ b/absl/container/CMakeLists.txt
@@ -204,6 +204,8 @@ absl_cc_library(
     "internal/counting_allocator.h"
   COPTS
     ${ABSL_DEFAULT_COPTS}
+  DEPS
+    absl::config
 )
 
 absl_cc_test(
@@ -574,6 +576,8 @@ absl_cc_library(
     "internal/hashtable_debug_hooks.h"
   COPTS
     ${ABSL_DEFAULT_COPTS}
+  DEPS
+    absl::config
   PUBLIC
 )
 
@@ -593,6 +597,8 @@ absl_cc_library(
     "internal/node_hash_policy.h"
   COPTS
     ${ABSL_DEFAULT_COPTS}
+  DEPS
+    absl::config
   PUBLIC
 )
 
@@ -735,6 +741,8 @@ absl_cc_library(
     "internal/tracked.h"
   COPTS
     ${ABSL_TEST_COPTS}
+  DEPS
+    absl::config
   TESTONLY
 )
 
diff --git a/absl/container/btree_map.h b/absl/container/btree_map.h
index 9f35f63949df..470e3197084c 100644
--- a/absl/container/btree_map.h
+++ b/absl/container/btree_map.h
@@ -51,6 +51,7 @@
 #include "absl/container/internal/btree_container.h"  // IWYU pragma: export
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // absl::btree_map<>
 //
@@ -700,6 +701,7 @@ void swap(btree_multimap<K, V, C, A> &x, btree_multimap<K, V, C, A> &y) {
   return x.swap(y);
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_CONTAINER_BTREE_MAP_H_
diff --git a/absl/container/btree_set.h b/absl/container/btree_set.h
index 6e47b4aae652..2a4d0aceb354 100644
--- a/absl/container/btree_set.h
+++ b/absl/container/btree_set.h
@@ -51,6 +51,7 @@
 #include "absl/container/internal/btree_container.h"  // IWYU pragma: export
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // absl::btree_set<>
 //
@@ -648,6 +649,7 @@ void swap(btree_multiset<K, C, A> &x, btree_multiset<K, C, A> &y) {
   return x.swap(y);
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_CONTAINER_BTREE_SET_H_
diff --git a/absl/container/btree_test.cc b/absl/container/btree_test.cc
index ea73f032ed63..f8aadd62ad75 100644
--- a/absl/container/btree_test.cc
+++ b/absl/container/btree_test.cc
@@ -42,6 +42,7 @@
 ABSL_FLAG(int, test_values, 10000, "The number of values to use for tests");
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 namespace {
 
@@ -2304,4 +2305,5 @@ TEST(Btree, EmptyTree) {
 
 }  // namespace
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/container/btree_test.h b/absl/container/btree_test.h
index 5ecf43ceebe5..218ba41dc2e9 100644
--- a/absl/container/btree_test.h
+++ b/absl/container/btree_test.h
@@ -28,6 +28,7 @@
 #include "absl/time/time.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 
 // Like remove_const but propagates the removal through std::pair.
@@ -148,6 +149,7 @@ std::vector<V> GenerateValuesWithSeed(int n, int maxval, int seed) {
 }
 
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_CONTAINER_BTREE_TEST_H_
diff --git a/absl/container/fixed_array.h b/absl/container/fixed_array.h
index 70e94ad5e182..a9ce99bafd32 100644
--- a/absl/container/fixed_array.h
+++ b/absl/container/fixed_array.h
@@ -50,6 +50,7 @@
 #include "absl/memory/memory.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 constexpr static auto kFixedArrayUseDefault = static_cast<size_t>(-1);
 
@@ -508,6 +509,7 @@ void FixedArray<T, N, A>::NonEmptyInlinedStorage::AnnotateDestruct(
 #endif                   // ADDRESS_SANITIZER
   static_cast<void>(n);  // Mark used when not in asan mode
 }
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_CONTAINER_FIXED_ARRAY_H_
diff --git a/absl/container/fixed_array_exception_safety_test.cc b/absl/container/fixed_array_exception_safety_test.cc
index 5ebeac05b7b4..a5bb009d9881 100644
--- a/absl/container/fixed_array_exception_safety_test.cc
+++ b/absl/container/fixed_array_exception_safety_test.cc
@@ -23,6 +23,7 @@
 #include "absl/base/internal/exception_safety_testing.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 namespace {
 
@@ -195,6 +196,7 @@ TEST(FixedArrayExceptionSafety, FillWithAlloc) {
 
 }  // namespace
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_HAVE_EXCEPTIONS
diff --git a/absl/container/flat_hash_map.h b/absl/container/flat_hash_map.h
index 283f24396764..fb570cd495ee 100644
--- a/absl/container/flat_hash_map.h
+++ b/absl/container/flat_hash_map.h
@@ -42,6 +42,7 @@
 #include "absl/memory/memory.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 template <class K, class V>
 struct FlatHashMapPolicy;
@@ -584,6 +585,7 @@ struct IsUnorderedContainer<
 
 }  // namespace container_algorithm_internal
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_CONTAINER_FLAT_HASH_MAP_H_
diff --git a/absl/container/flat_hash_map_test.cc b/absl/container/flat_hash_map_test.cc
index 02d1f879dae1..dae8e00389bc 100644
--- a/absl/container/flat_hash_map_test.cc
+++ b/absl/container/flat_hash_map_test.cc
@@ -24,6 +24,7 @@
 #include "absl/types/any.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 namespace {
 using ::absl::container_internal::hash_internal::Enum;
@@ -251,4 +252,5 @@ TEST(FlatHashMap, Any) {
 
 }  // namespace
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/container/flat_hash_set.h b/absl/container/flat_hash_set.h
index 2a51c3411d66..930107ea212d 100644
--- a/absl/container/flat_hash_set.h
+++ b/absl/container/flat_hash_set.h
@@ -40,6 +40,7 @@
 #include "absl/memory/memory.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 template <typename T>
 struct FlatHashSetPolicy;
@@ -488,6 +489,7 @@ struct IsUnorderedContainer<absl::flat_hash_set<Key, Hash, KeyEqual, Allocator>>
 
 }  // namespace container_algorithm_internal
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_CONTAINER_FLAT_HASH_SET_H_
diff --git a/absl/container/flat_hash_set_test.cc b/absl/container/flat_hash_set_test.cc
index b55be59b04c8..6eacb1bb653c 100644
--- a/absl/container/flat_hash_set_test.cc
+++ b/absl/container/flat_hash_set_test.cc
@@ -25,6 +25,7 @@
 #include "absl/strings/string_view.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 namespace {
 
@@ -125,4 +126,5 @@ TEST(FlatHashSet, MergeExtractInsert) {
 
 }  // namespace
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/container/inlined_vector.h b/absl/container/inlined_vector.h
index d5c67db59842..2388d471dcc8 100644
--- a/absl/container/inlined_vector.h
+++ b/absl/container/inlined_vector.h
@@ -54,6 +54,7 @@
 #include "absl/memory/memory.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 // -----------------------------------------------------------------------------
 // InlinedVector
 // -----------------------------------------------------------------------------
@@ -841,6 +842,7 @@ H AbslHashValue(H h, const absl::InlinedVector<T, N, A>& a) {
   return H::combine(H::combine_contiguous(std::move(h), a.data(), size), size);
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_CONTAINER_INLINED_VECTOR_H_
diff --git a/absl/container/internal/btree.h b/absl/container/internal/btree.h
index 40217dd5f0a8..aef861dc6dc6 100644
--- a/absl/container/internal/btree.h
+++ b/absl/container/internal/btree.h
@@ -70,6 +70,7 @@
 #include "absl/utility/utility.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 
 // A helper class that indicates if the Compare parameter is a key-compare-to
@@ -2606,6 +2607,7 @@ int btree<P>::internal_verify(
 }
 
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_CONTAINER_INTERNAL_BTREE_H_
diff --git a/absl/container/internal/btree_container.h b/absl/container/internal/btree_container.h
index 774412d91592..04795c2e3f0a 100644
--- a/absl/container/internal/btree_container.h
+++ b/absl/container/internal/btree_container.h
@@ -26,6 +26,7 @@
 #include "absl/meta/type_traits.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 
 // A common base class for btree_set, btree_map, btree_multiset, and
@@ -602,6 +603,7 @@ class btree_multimap_container : public btree_multiset_container<Tree> {
 };
 
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_CONTAINER_INTERNAL_BTREE_CONTAINER_H_
diff --git a/absl/container/internal/common.h b/absl/container/internal/common.h
index cc7633dcfa15..853a5b214925 100644
--- a/absl/container/internal/common.h
+++ b/absl/container/internal/common.h
@@ -22,6 +22,7 @@
 #include "absl/types/optional.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 
 template <class, class = void>
@@ -196,6 +197,7 @@ struct InsertReturnType {
 };
 
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_CONTAINER_INTERNAL_CONTAINER_H_
diff --git a/absl/container/internal/compressed_tuple.h b/absl/container/internal/compressed_tuple.h
index 7d08e370dec1..4bfe92fd991f 100644
--- a/absl/container/internal/compressed_tuple.h
+++ b/absl/container/internal/compressed_tuple.h
@@ -48,6 +48,7 @@
 #endif
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 
 template <typename... Ts>
@@ -256,6 +257,7 @@ template <>
 class ABSL_INTERNAL_COMPRESSED_TUPLE_DECLSPEC CompressedTuple<> {};
 
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #undef ABSL_INTERNAL_COMPRESSED_TUPLE_DECLSPEC
diff --git a/absl/container/internal/compressed_tuple_test.cc b/absl/container/internal/compressed_tuple_test.cc
index 19af8f10aa6c..76bc92130e26 100644
--- a/absl/container/internal/compressed_tuple_test.cc
+++ b/absl/container/internal/compressed_tuple_test.cc
@@ -48,6 +48,7 @@ struct TwoValues {
 
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 namespace {
 
@@ -408,4 +409,5 @@ TEST(CompressedTupleTest, EmptyFinalClass) {
 
 }  // namespace
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/container/internal/container_memory.h b/absl/container/internal/container_memory.h
index e5bb977355ee..d24b0f841384 100644
--- a/absl/container/internal/container_memory.h
+++ b/absl/container/internal/container_memory.h
@@ -34,6 +34,7 @@
 #include "absl/utility/utility.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 
 // Allocates at least n bytes aligned to the specified alignment.
@@ -433,6 +434,7 @@ struct map_slot_policy {
 };
 
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_CONTAINER_INTERNAL_CONTAINER_MEMORY_H_
diff --git a/absl/container/internal/container_memory_test.cc b/absl/container/internal/container_memory_test.cc
index d6b0495f173a..7942c7be4831 100644
--- a/absl/container/internal/container_memory_test.cc
+++ b/absl/container/internal/container_memory_test.cc
@@ -23,6 +23,7 @@
 #include "absl/strings/string_view.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 namespace {
 
@@ -185,4 +186,5 @@ TEST(DecomposePair, NotDecomposable) {
 
 }  // namespace
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/container/internal/counting_allocator.h b/absl/container/internal/counting_allocator.h
index 4e717bef6789..9efdc6621363 100644
--- a/absl/container/internal/counting_allocator.h
+++ b/absl/container/internal/counting_allocator.h
@@ -19,7 +19,10 @@
 #include <cstdint>
 #include <memory>
 
+#include "absl/base/config.h"
+
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 
 // This is a stateful allocator, but the state lives outside of the
@@ -74,6 +77,7 @@ class CountingAllocator : public std::allocator<T> {
 };
 
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_CONTAINER_INTERNAL_COUNTING_ALLOCATOR_H_
diff --git a/absl/container/internal/hash_function_defaults.h b/absl/container/internal/hash_function_defaults.h
index cb8f03c87aaf..401ddf4d83c6 100644
--- a/absl/container/internal/hash_function_defaults.h
+++ b/absl/container/internal/hash_function_defaults.h
@@ -56,6 +56,7 @@
 #include "absl/strings/string_view.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 
 // The hash of an object of type T is computed by using absl::Hash.
@@ -139,6 +140,7 @@ template <class T>
 using hash_default_eq = typename container_internal::HashEq<T>::Eq;
 
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_CONTAINER_INTERNAL_HASH_FUNCTION_DEFAULTS_H_
diff --git a/absl/container/internal/hash_function_defaults_test.cc b/absl/container/internal/hash_function_defaults_test.cc
index 82708dbe9530..2eefc7e0defb 100644
--- a/absl/container/internal/hash_function_defaults_test.cc
+++ b/absl/container/internal/hash_function_defaults_test.cc
@@ -22,6 +22,7 @@
 #include "absl/strings/string_view.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 namespace {
 
@@ -248,6 +249,7 @@ TYPED_TEST_SUITE(StringLikeTest, StringTypesCartesianProduct);
 
 }  // namespace
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 enum Hash : size_t {
@@ -278,6 +280,7 @@ struct hash<Hashable<H>> {
 }  // namespace std
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 namespace {
 
@@ -292,4 +295,5 @@ TEST(Delegate, HashDispatch) {
 
 }  // namespace
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/container/internal/hash_generator_testing.cc b/absl/container/internal/hash_generator_testing.cc
index 37a23d6091d9..75c4db6c3661 100644
--- a/absl/container/internal/hash_generator_testing.cc
+++ b/absl/container/internal/hash_generator_testing.cc
@@ -17,6 +17,7 @@
 #include <deque>
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 namespace hash_internal {
 namespace {
@@ -69,4 +70,5 @@ absl::string_view Generator<absl::string_view>::operator()() const {
 
 }  // namespace hash_internal
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/container/internal/hash_generator_testing.h b/absl/container/internal/hash_generator_testing.h
index 477215cdba23..6869fe45e8c8 100644
--- a/absl/container/internal/hash_generator_testing.h
+++ b/absl/container/internal/hash_generator_testing.h
@@ -33,6 +33,7 @@
 #include "absl/strings/string_view.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 namespace hash_internal {
 namespace generator_internal {
@@ -154,6 +155,7 @@ using GeneratedType = decltype(
 
 }  // namespace hash_internal
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_CONTAINER_INTERNAL_HASH_GENERATOR_TESTING_H_
diff --git a/absl/container/internal/hash_policy_testing.h b/absl/container/internal/hash_policy_testing.h
index c57407a02b2e..01c40d2e5cff 100644
--- a/absl/container/internal/hash_policy_testing.h
+++ b/absl/container/internal/hash_policy_testing.h
@@ -30,6 +30,7 @@
 #include "absl/strings/string_view.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 namespace hash_testing_internal {
 
@@ -162,6 +163,7 @@ auto keys(const Set& s)
 }
 
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 // ABSL_UNORDERED_SUPPORTS_ALLOC_CTORS is false for glibcxx versions
diff --git a/absl/container/internal/hash_policy_testing_test.cc b/absl/container/internal/hash_policy_testing_test.cc
index 0c95eb5eaa57..f0b20fe345e2 100644
--- a/absl/container/internal/hash_policy_testing_test.cc
+++ b/absl/container/internal/hash_policy_testing_test.cc
@@ -17,6 +17,7 @@
 #include "gtest/gtest.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 namespace {
 
@@ -40,4 +41,5 @@ TEST(_, Hash) {
 
 }  // namespace
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/container/internal/hash_policy_traits.h b/absl/container/internal/hash_policy_traits.h
index fd007de7c0db..3e1209c6ebec 100644
--- a/absl/container/internal/hash_policy_traits.h
+++ b/absl/container/internal/hash_policy_traits.h
@@ -23,6 +23,7 @@
 #include "absl/meta/type_traits.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 
 // Defines how slots are initialized/destroyed/moved.
@@ -184,6 +185,7 @@ struct hash_policy_traits {
 };
 
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_CONTAINER_INTERNAL_HASH_POLICY_TRAITS_H_
diff --git a/absl/container/internal/hash_policy_traits_test.cc b/absl/container/internal/hash_policy_traits_test.cc
index e643d189913c..6ef8b9e05fb1 100644
--- a/absl/container/internal/hash_policy_traits_test.cc
+++ b/absl/container/internal/hash_policy_traits_test.cc
@@ -22,6 +22,7 @@
 #include "gtest/gtest.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 namespace {
 
@@ -139,4 +140,5 @@ TEST_F(Test, with_transfer) {
 
 }  // namespace
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/container/internal/hashtable_debug.h b/absl/container/internal/hashtable_debug.h
index 71930004607e..19d52121d688 100644
--- a/absl/container/internal/hashtable_debug.h
+++ b/absl/container/internal/hashtable_debug.h
@@ -38,6 +38,7 @@
 #include "absl/container/internal/hashtable_debug_hooks.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 
 // Returns the number of probes required to lookup `key`.  Returns 0 for a
@@ -103,6 +104,7 @@ size_t LowerBoundAllocatedByteSize(size_t num_elements) {
 }
 
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_CONTAINER_INTERNAL_HASHTABLE_DEBUG_H_
diff --git a/absl/container/internal/hashtable_debug_hooks.h b/absl/container/internal/hashtable_debug_hooks.h
index 371ce81f55c6..3e9ea5954e0a 100644
--- a/absl/container/internal/hashtable_debug_hooks.h
+++ b/absl/container/internal/hashtable_debug_hooks.h
@@ -23,7 +23,10 @@
 #include <type_traits>
 #include <vector>
 
+#include "absl/base/config.h"
+
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 namespace hashtable_debug_internal {
 
@@ -76,6 +79,7 @@ struct HashtableDebugAccess {
 
 }  // namespace hashtable_debug_internal
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_CONTAINER_INTERNAL_HASHTABLE_DEBUG_HOOKS_H_
diff --git a/absl/container/internal/hashtablez_sampler.cc b/absl/container/internal/hashtablez_sampler.cc
index 6deeca44d97b..e15f44443f59 100644
--- a/absl/container/internal/hashtablez_sampler.cc
+++ b/absl/container/internal/hashtablez_sampler.cc
@@ -28,6 +28,7 @@
 #include "absl/synchronization/mutex.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 constexpr int HashtablezInfo::kMaxStackDepth;
 
@@ -265,4 +266,5 @@ void SetHashtablezMaxSamples(int32_t max) {
 }
 
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/container/internal/hashtablez_sampler.h b/absl/container/internal/hashtablez_sampler.h
index c694df057d8e..c4f9629fcb47 100644
--- a/absl/container/internal/hashtablez_sampler.h
+++ b/absl/container/internal/hashtablez_sampler.h
@@ -51,6 +51,7 @@
 #include "absl/utility/utility.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 
 // Stores information about a sampled hashtable.  All mutations to this *must*
@@ -281,6 +282,7 @@ void SetHashtablezMaxSamples(int32_t max);
 extern "C" bool AbslContainerInternalSampleEverything();
 
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_CONTAINER_INTERNAL_HASHTABLEZ_SAMPLER_H_
diff --git a/absl/container/internal/hashtablez_sampler_force_weak_definition.cc b/absl/container/internal/hashtablez_sampler_force_weak_definition.cc
index 984dce5dd992..78b9d362acf3 100644
--- a/absl/container/internal/hashtablez_sampler_force_weak_definition.cc
+++ b/absl/container/internal/hashtablez_sampler_force_weak_definition.cc
@@ -17,6 +17,7 @@
 #include "absl/base/attributes.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 
 // See hashtablez_sampler.h for details.
@@ -25,4 +26,5 @@ extern "C" ABSL_ATTRIBUTE_WEAK bool AbslContainerInternalSampleEverything() {
 }
 
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/container/internal/hashtablez_sampler_test.cc b/absl/container/internal/hashtablez_sampler_test.cc
index af4b5ee108ac..102b23757cf6 100644
--- a/absl/container/internal/hashtablez_sampler_test.cc
+++ b/absl/container/internal/hashtablez_sampler_test.cc
@@ -36,6 +36,7 @@ constexpr int kProbeLength = 8;
 #endif
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 class HashtablezInfoHandlePeer {
  public:
@@ -354,4 +355,5 @@ TEST(HashtablezSamplerTest, Callback) {
 
 }  // namespace
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/container/internal/inlined_vector.h b/absl/container/internal/inlined_vector.h
index 84aa785ad636..4d80b727bf4c 100644
--- a/absl/container/internal/inlined_vector.h
+++ b/absl/container/internal/inlined_vector.h
@@ -30,6 +30,7 @@
 #include "absl/types/span.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace inlined_vector_internal {
 
 template <typename Iterator>
@@ -885,6 +886,7 @@ auto Storage<T, N, A>::Swap(Storage* other_storage_ptr) -> void {
 }
 
 }  // namespace inlined_vector_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_CONTAINER_INTERNAL_INLINED_VECTOR_INTERNAL_H_
diff --git a/absl/container/internal/layout.h b/absl/container/internal/layout.h
index bbdde50796ea..69cc85dd6679 100644
--- a/absl/container/internal/layout.h
+++ b/absl/container/internal/layout.h
@@ -188,6 +188,7 @@
 #endif
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 
 // A type wrapper that instructs `Layout` to use the specific alignment for the
@@ -734,6 +735,7 @@ class Layout : public internal_layout::LayoutType<sizeof...(Ts), Ts...> {
 };
 
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_CONTAINER_INTERNAL_LAYOUT_H_
diff --git a/absl/container/internal/layout_test.cc b/absl/container/internal/layout_test.cc
index 33b72bd372e3..8f3628a1f1a5 100644
--- a/absl/container/internal/layout_test.cc
+++ b/absl/container/internal/layout_test.cc
@@ -28,6 +28,7 @@
 #include "absl/types/span.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 namespace {
 
@@ -1562,4 +1563,5 @@ TEST(CompactString, Works) {
 
 }  // namespace
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/container/internal/node_hash_policy.h b/absl/container/internal/node_hash_policy.h
index 19b4fc098fb8..4617162f0b32 100644
--- a/absl/container/internal/node_hash_policy.h
+++ b/absl/container/internal/node_hash_policy.h
@@ -39,7 +39,10 @@
 #include <type_traits>
 #include <utility>
 
+#include "absl/base/config.h"
+
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 
 template <class Reference, class Policy>
@@ -83,6 +86,7 @@ struct node_hash_policy {
 };
 
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_CONTAINER_INTERNAL_NODE_HASH_POLICY_H_
diff --git a/absl/container/internal/node_hash_policy_test.cc b/absl/container/internal/node_hash_policy_test.cc
index f1d3ec3014ae..84aabba96830 100644
--- a/absl/container/internal/node_hash_policy_test.cc
+++ b/absl/container/internal/node_hash_policy_test.cc
@@ -21,6 +21,7 @@
 #include "absl/container/internal/hash_policy_traits.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 namespace {
 
@@ -64,4 +65,5 @@ TEST_F(NodeTest, transfer) {
 
 }  // namespace
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/container/internal/raw_hash_map.h b/absl/container/internal/raw_hash_map.h
index 7dad120ad126..0a02757ddfb4 100644
--- a/absl/container/internal/raw_hash_map.h
+++ b/absl/container/internal/raw_hash_map.h
@@ -24,6 +24,7 @@
 #include "absl/container/internal/raw_hash_set.h"  // IWYU pragma: export
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 
 template <class Policy, class Hash, class Eq, class Alloc>
@@ -190,6 +191,7 @@ class raw_hash_map : public raw_hash_set<Policy, Hash, Eq, Alloc> {
 };
 
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_CONTAINER_INTERNAL_RAW_HASH_MAP_H_
diff --git a/absl/container/internal/raw_hash_set.cc b/absl/container/internal/raw_hash_set.cc
index ac2d10a7666c..919ac0740573 100644
--- a/absl/container/internal/raw_hash_set.cc
+++ b/absl/container/internal/raw_hash_set.cc
@@ -20,6 +20,7 @@
 #include "absl/base/config.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 
 constexpr size_t Group::kWidth;
@@ -43,4 +44,5 @@ bool ShouldInsertBackwards(size_t hash, ctrl_t* ctrl) {
 }
 
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/container/internal/raw_hash_set.h b/absl/container/internal/raw_hash_set.h
index 469226fedd86..4103e02ab0b0 100644
--- a/absl/container/internal/raw_hash_set.h
+++ b/absl/container/internal/raw_hash_set.h
@@ -118,6 +118,7 @@
 #include "absl/utility/utility.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 
 template <size_t Width>
@@ -1861,6 +1862,7 @@ struct HashtableDebugAccess<Set, absl::void_t<typename Set::raw_hash_set>> {
 
 }  // namespace hashtable_debug_internal
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_CONTAINER_INTERNAL_RAW_HASH_SET_H_
diff --git a/absl/container/internal/raw_hash_set_allocator_test.cc b/absl/container/internal/raw_hash_set_allocator_test.cc
index a5eff0b3d27f..7ac4b9f7dfc5 100644
--- a/absl/container/internal/raw_hash_set_allocator_test.cc
+++ b/absl/container/internal/raw_hash_set_allocator_test.cc
@@ -20,6 +20,7 @@
 #include "absl/container/internal/tracked.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 namespace {
 
@@ -425,4 +426,5 @@ TEST_F(PropagateOnAll, Swap) {
 
 }  // namespace
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/container/internal/raw_hash_set_test.cc b/absl/container/internal/raw_hash_set_test.cc
index ec8f92313bac..38e5e0e8d3bd 100644
--- a/absl/container/internal/raw_hash_set_test.cc
+++ b/absl/container/internal/raw_hash_set_test.cc
@@ -35,6 +35,7 @@
 #include "absl/strings/string_view.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 
 struct RawHashSetTestOnlyAccess {
@@ -1913,4 +1914,5 @@ TEST(Sanitizer, PoisoningOnErase) {
 
 }  // namespace
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/container/internal/test_instance_tracker.cc b/absl/container/internal/test_instance_tracker.cc
index 5a66cb4d14d2..f9947f0475d2 100644
--- a/absl/container/internal/test_instance_tracker.cc
+++ b/absl/container/internal/test_instance_tracker.cc
@@ -15,6 +15,7 @@
 #include "absl/container/internal/test_instance_tracker.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace test_internal {
 int BaseCountedInstance::num_instances_ = 0;
 int BaseCountedInstance::num_live_instances_ = 0;
@@ -24,4 +25,5 @@ int BaseCountedInstance::num_swaps_ = 0;
 int BaseCountedInstance::num_comparisons_ = 0;
 
 }  // namespace test_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/container/internal/test_instance_tracker.h b/absl/container/internal/test_instance_tracker.h
index c4731dbe3d1d..5ff6fd714e2b 100644
--- a/absl/container/internal/test_instance_tracker.h
+++ b/absl/container/internal/test_instance_tracker.h
@@ -21,6 +21,7 @@
 #include "absl/types/compare.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace test_internal {
 
 // A type that counts number of occurrences of the type, the live occurrences of
@@ -267,6 +268,7 @@ class MovableOnlyInstance : public BaseCountedInstance {
 };
 
 }  // namespace test_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_CONTAINER_INTERNAL_TEST_INSTANCE_TRACKER_H_
diff --git a/absl/container/internal/tracked.h b/absl/container/internal/tracked.h
index 75173ab00aac..29f5829f7199 100644
--- a/absl/container/internal/tracked.h
+++ b/absl/container/internal/tracked.h
@@ -16,10 +16,14 @@
 #define ABSL_CONTAINER_INTERNAL_TRACKED_H_
 
 #include <stddef.h>
+
 #include <memory>
 #include <utility>
 
+#include "absl/base/config.h"
+
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 
 // A class that tracks its copies and moves so that it can be queried in tests.
@@ -73,6 +77,7 @@ class Tracked {
 };
 
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_CONTAINER_INTERNAL_TRACKED_H_
diff --git a/absl/container/internal/unordered_map_constructor_test.h b/absl/container/internal/unordered_map_constructor_test.h
index 68817e4e4cc0..76ee95e6abc5 100644
--- a/absl/container/internal/unordered_map_constructor_test.h
+++ b/absl/container/internal/unordered_map_constructor_test.h
@@ -24,6 +24,7 @@
 #include "absl/container/internal/hash_policy_testing.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 
 template <class UnordMap>
@@ -482,6 +483,7 @@ REGISTER_TYPED_TEST_CASE_P(
     AssignmentFromInitializerListOverwritesExisting, AssignmentOnSelf);
 
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_CONTAINER_INTERNAL_UNORDERED_MAP_CONSTRUCTOR_TEST_H_
diff --git a/absl/container/internal/unordered_map_lookup_test.h b/absl/container/internal/unordered_map_lookup_test.h
index ebd3612bdf37..e76421e508fe 100644
--- a/absl/container/internal/unordered_map_lookup_test.h
+++ b/absl/container/internal/unordered_map_lookup_test.h
@@ -21,6 +21,7 @@
 #include "absl/container/internal/hash_policy_testing.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 
 template <class UnordMap>
@@ -110,6 +111,7 @@ REGISTER_TYPED_TEST_CASE_P(LookupTest, At, OperatorBracket, Count, Find,
                            EqualRange);
 
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_CONTAINER_INTERNAL_UNORDERED_MAP_LOOKUP_TEST_H_
diff --git a/absl/container/internal/unordered_map_members_test.h b/absl/container/internal/unordered_map_members_test.h
index 1bf31ab40951..7d48cdb890bb 100644
--- a/absl/container/internal/unordered_map_members_test.h
+++ b/absl/container/internal/unordered_map_members_test.h
@@ -21,6 +21,7 @@
 #include "absl/meta/type_traits.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 
 template <class UnordMap>
@@ -80,6 +81,7 @@ TYPED_TEST_P(MembersTest, BeginEnd) {
 REGISTER_TYPED_TEST_SUITE_P(MembersTest, Typedefs, SimpleFunctions, BeginEnd);
 
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_CONTAINER_INTERNAL_UNORDERED_MAP_MEMBERS_TEST_H_
diff --git a/absl/container/internal/unordered_map_modifiers_test.h b/absl/container/internal/unordered_map_modifiers_test.h
index f6aff5422b41..b8c513f1579d 100644
--- a/absl/container/internal/unordered_map_modifiers_test.h
+++ b/absl/container/internal/unordered_map_modifiers_test.h
@@ -23,6 +23,7 @@
 #include "absl/container/internal/hash_policy_testing.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 
 template <class UnordMap>
@@ -309,6 +310,7 @@ TYPED_TEST_P(UniquePtrModifiersTest, TryEmplace) {
 REGISTER_TYPED_TEST_SUITE_P(UniquePtrModifiersTest, TryEmplace);
 
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_CONTAINER_INTERNAL_UNORDERED_MAP_MODIFIERS_TEST_H_
diff --git a/absl/container/internal/unordered_map_test.cc b/absl/container/internal/unordered_map_test.cc
index 114b342def76..9cbf512f32b2 100644
--- a/absl/container/internal/unordered_map_test.cc
+++ b/absl/container/internal/unordered_map_test.cc
@@ -21,6 +21,7 @@
 #include "absl/container/internal/unordered_map_modifiers_test.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 namespace {
 
@@ -45,4 +46,5 @@ INSTANTIATE_TYPED_TEST_SUITE_P(UnorderedMap, UniquePtrModifiersTest,
 
 }  // namespace
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/container/internal/unordered_set_constructor_test.h b/absl/container/internal/unordered_set_constructor_test.h
index f484468393e4..41165b05e97b 100644
--- a/absl/container/internal/unordered_set_constructor_test.h
+++ b/absl/container/internal/unordered_set_constructor_test.h
@@ -26,6 +26,7 @@
 #include "absl/meta/type_traits.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 
 template <class UnordMap>
@@ -489,6 +490,7 @@ REGISTER_TYPED_TEST_CASE_P(
     AssignmentFromInitializerListOverwritesExisting, AssignmentOnSelf);
 
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_CONTAINER_INTERNAL_UNORDERED_SET_CONSTRUCTOR_TEST_H_
diff --git a/absl/container/internal/unordered_set_lookup_test.h b/absl/container/internal/unordered_set_lookup_test.h
index 05b32b5d906b..8f2f4b207ef0 100644
--- a/absl/container/internal/unordered_set_lookup_test.h
+++ b/absl/container/internal/unordered_set_lookup_test.h
@@ -21,6 +21,7 @@
 #include "absl/container/internal/hash_policy_testing.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 
 template <class UnordSet>
@@ -84,6 +85,7 @@ TYPED_TEST_P(LookupTest, EqualRange) {
 REGISTER_TYPED_TEST_CASE_P(LookupTest, Count, Find, EqualRange);
 
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_CONTAINER_INTERNAL_UNORDERED_SET_LOOKUP_TEST_H_
diff --git a/absl/container/internal/unordered_set_members_test.h b/absl/container/internal/unordered_set_members_test.h
index b96c945a11bd..4c5e104af292 100644
--- a/absl/container/internal/unordered_set_members_test.h
+++ b/absl/container/internal/unordered_set_members_test.h
@@ -21,6 +21,7 @@
 #include "absl/meta/type_traits.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 
 template <class UnordSet>
@@ -79,6 +80,7 @@ TYPED_TEST_P(MembersTest, BeginEnd) {
 REGISTER_TYPED_TEST_SUITE_P(MembersTest, Typedefs, SimpleFunctions, BeginEnd);
 
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_CONTAINER_INTERNAL_UNORDERED_SET_MEMBERS_TEST_H_
diff --git a/absl/container/internal/unordered_set_modifiers_test.h b/absl/container/internal/unordered_set_modifiers_test.h
index 79a8d422be1e..26be58d99f21 100644
--- a/absl/container/internal/unordered_set_modifiers_test.h
+++ b/absl/container/internal/unordered_set_modifiers_test.h
@@ -21,6 +21,7 @@
 #include "absl/container/internal/hash_policy_testing.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 
 template <class UnordSet>
@@ -183,6 +184,7 @@ REGISTER_TYPED_TEST_CASE_P(ModifiersTest, Clear, Insert, InsertHint,
                            EraseKey, Swap);
 
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_CONTAINER_INTERNAL_UNORDERED_SET_MODIFIERS_TEST_H_
diff --git a/absl/container/internal/unordered_set_test.cc b/absl/container/internal/unordered_set_test.cc
index 6478fac17c7d..a134b53984bc 100644
--- a/absl/container/internal/unordered_set_test.cc
+++ b/absl/container/internal/unordered_set_test.cc
@@ -20,6 +20,7 @@
 #include "absl/container/internal/unordered_set_modifiers_test.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 namespace {
 
@@ -36,4 +37,5 @@ INSTANTIATE_TYPED_TEST_SUITE_P(UnorderedSet, ModifiersTest, SetTypes);
 
 }  // namespace
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/container/node_hash_map.h b/absl/container/node_hash_map.h
index a718842b6532..e8065a98a987 100644
--- a/absl/container/node_hash_map.h
+++ b/absl/container/node_hash_map.h
@@ -48,6 +48,7 @@
 #include "absl/memory/memory.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 template <class Key, class Value>
 class NodeHashMapPolicy;
@@ -581,6 +582,7 @@ struct IsUnorderedContainer<
 
 }  // namespace container_algorithm_internal
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_CONTAINER_NODE_HASH_MAP_H_
diff --git a/absl/container/node_hash_map_test.cc b/absl/container/node_hash_map_test.cc
index 0f2714a72ceb..f923e91513a5 100644
--- a/absl/container/node_hash_map_test.cc
+++ b/absl/container/node_hash_map_test.cc
@@ -21,6 +21,7 @@
 #include "absl/container/internal/unordered_map_modifiers_test.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 namespace {
 
@@ -217,4 +218,5 @@ TEST(NodeHashMap, MergeExtractInsert) {
 
 }  // namespace
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/container/node_hash_set.h b/absl/container/node_hash_set.h
index 0cd1fe57f965..43ada3f9df24 100644
--- a/absl/container/node_hash_set.h
+++ b/absl/container/node_hash_set.h
@@ -44,6 +44,7 @@
 #include "absl/memory/memory.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 template <typename T>
 struct NodeHashSetPolicy;
@@ -483,6 +484,7 @@ struct IsUnorderedContainer<absl::node_hash_set<Key, Hash, KeyEqual, Allocator>>
     : std::true_type {};
 
 }  // namespace container_algorithm_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_CONTAINER_NODE_HASH_SET_H_
diff --git a/absl/container/node_hash_set_test.cc b/absl/container/node_hash_set_test.cc
index 0ea76e7c78ec..e1d544ff882e 100644
--- a/absl/container/node_hash_set_test.cc
+++ b/absl/container/node_hash_set_test.cc
@@ -20,6 +20,7 @@
 #include "absl/container/internal/unordered_set_modifiers_test.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 namespace {
 using ::absl::container_internal::hash_internal::Enum;
@@ -102,4 +103,5 @@ TEST(NodeHashSet, MergeExtractInsert) {
 
 }  // namespace
 }  // namespace container_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/debugging/BUILD.bazel b/absl/debugging/BUILD.bazel
index 2601090bc60b..32cacefde3df 100644
--- a/absl/debugging/BUILD.bazel
+++ b/absl/debugging/BUILD.bazel
@@ -38,6 +38,7 @@ cc_library(
     linkopts = ABSL_DEFAULT_LINKOPTS,
     deps = [
         ":debugging_internal",
+        "//absl/base:config",
         "//absl/base:core_headers",
     ],
 )
@@ -63,6 +64,7 @@ cc_library(
         ":debugging_internal",
         ":demangle_internal",
         "//absl/base",
+        "//absl/base:config",
         "//absl/base:core_headers",
         "//absl/base:dynamic_annotations",
         "//absl/base:malloc_internal",
@@ -106,6 +108,7 @@ cc_library(
     deps = [
         ":stacktrace",
         ":symbolize",
+        "//absl/base:config",
         "//absl/base:core_headers",
         "//absl/base:raw_logging_internal",
     ],
@@ -168,6 +171,7 @@ cc_library(
     copts = ABSL_DEFAULT_COPTS,
     linkopts = ABSL_DEFAULT_LINKOPTS,
     deps = [
+        "//absl/base:config",
         "//absl/base:core_headers",
         "//absl/base:dynamic_annotations",
         "//absl/base:raw_logging_internal",
@@ -181,6 +185,7 @@ cc_library(
     copts = ABSL_DEFAULT_COPTS,
     deps = [
         "//absl/base",
+        "//absl/base:config",
         "//absl/base:core_headers",
     ],
 )
@@ -205,7 +210,10 @@ cc_library(
     srcs = ["leak_check.cc"],
     hdrs = ["leak_check.h"],
     linkopts = ABSL_DEFAULT_LINKOPTS,
-    deps = ["//absl/base:core_headers"],
+    deps = [
+        "//absl/base:config",
+        "//absl/base:core_headers",
+    ],
 )
 
 # Adding a dependency to leak_check_disable will disable
@@ -216,6 +224,7 @@ cc_library(
     srcs = ["leak_check_disable.cc"],
     linkopts = ABSL_DEFAULT_LINKOPTS,
     linkstatic = 1,
+    deps = ["//absl/base:config"],
     alwayslink = 1,
 )
 
@@ -237,6 +246,9 @@ cc_library(
     }),
     linkopts = ABSL_DEFAULT_LINKOPTS,
     visibility = ["//visibility:private"],
+    deps = [
+        "//absl/base:config",
+    ],
 )
 
 cc_library(
@@ -247,6 +259,9 @@ cc_library(
     copts = ["-ULEAK_SANITIZER"],
     linkopts = ABSL_DEFAULT_LINKOPTS,
     visibility = ["//visibility:private"],
+    deps = [
+        "//absl/base:config",
+    ],
 )
 
 cc_test(
@@ -304,6 +319,7 @@ cc_library(
     linkopts = ABSL_DEFAULT_LINKOPTS,
     visibility = ["//visibility:private"],
     deps = [
+        "//absl/base:config",
         "//absl/base:core_headers",
         "//absl/base:raw_logging_internal",
     ],
diff --git a/absl/debugging/CMakeLists.txt b/absl/debugging/CMakeLists.txt
index eff504b48832..ef9e71fc0481 100644
--- a/absl/debugging/CMakeLists.txt
+++ b/absl/debugging/CMakeLists.txt
@@ -25,6 +25,7 @@ absl_cc_library(
     ${ABSL_DEFAULT_COPTS}
   DEPS
     absl::debugging_internal
+    absl::config
     absl::core_headers
   PUBLIC
 )
@@ -49,6 +50,7 @@ absl_cc_library(
     absl::debugging_internal
     absl::demangle_internal
     absl::base
+    absl::config
     absl::core_headers
     absl::dynamic_annotations
     absl::malloc_internal
@@ -88,6 +90,7 @@ absl_cc_library(
   DEPS
     absl::stacktrace
     absl::symbolize
+    absl::config
     absl::core_headers
     absl::raw_logging_internal
 )
@@ -151,6 +154,7 @@ absl_cc_library(
     ${ABSL_DEFAULT_COPTS}
   DEPS
     absl::core_headers
+    absl::config
     absl::dynamic_annotations
     absl::raw_logging_internal
 )
@@ -196,6 +200,7 @@ absl_cc_library(
   COPTS
     ${ABSL_DEFAULT_COPTS}
   DEPS
+    absl::config
     absl::core_headers
   PUBLIC
 )
@@ -293,6 +298,7 @@ absl_cc_library(
   COPTS
     ${ABSL_DEFAULT_COPTS}
   DEPS
+    absl::config
     absl::core_headers
     absl::raw_logging_internal
   TESTONLY
diff --git a/absl/debugging/failure_signal_handler.cc b/absl/debugging/failure_signal_handler.cc
index c6a4d962b42c..470d676812c2 100644
--- a/absl/debugging/failure_signal_handler.cc
+++ b/absl/debugging/failure_signal_handler.cc
@@ -47,6 +47,7 @@
 #endif
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 ABSL_CONST_INIT static FailureSignalHandlerOptions fsh_options;
 
@@ -356,4 +357,5 @@ void InstallFailureSignalHandler(const FailureSignalHandlerOptions& options) {
   }
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/debugging/failure_signal_handler.h b/absl/debugging/failure_signal_handler.h
index 1beb78b93788..f5a83962f1fc 100644
--- a/absl/debugging/failure_signal_handler.h
+++ b/absl/debugging/failure_signal_handler.h
@@ -44,7 +44,10 @@
 #ifndef ABSL_DEBUGGING_FAILURE_SIGNAL_HANDLER_H_
 #define ABSL_DEBUGGING_FAILURE_SIGNAL_HANDLER_H_
 
+#include "absl/base/config.h"
+
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // FailureSignalHandlerOptions
 //
@@ -112,6 +115,7 @@ namespace debugging_internal {
 const char* FailureSignalToString(int signo);
 }  // namespace debugging_internal
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_DEBUGGING_FAILURE_SIGNAL_HANDLER_H_
diff --git a/absl/debugging/internal/address_is_readable.cc b/absl/debugging/internal/address_is_readable.cc
index 99c4c64be81e..f45e59b3836a 100644
--- a/absl/debugging/internal/address_is_readable.cc
+++ b/absl/debugging/internal/address_is_readable.cc
@@ -20,12 +20,14 @@
 #if !defined(__linux__) || defined(__ANDROID__)
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace debugging_internal {
 
 // On platforms other than Linux, just return true.
 bool AddressIsReadable(const void* /* addr */) { return true; }
 
 }  // namespace debugging_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #else
@@ -40,6 +42,7 @@ bool AddressIsReadable(const void* /* addr */) { return true; }
 #include "absl/base/internal/raw_logging.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace debugging_internal {
 
 // Pack a pid and two file descriptors into a 64-bit word,
@@ -128,6 +131,7 @@ bool AddressIsReadable(const void *addr) {
 }
 
 }  // namespace debugging_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif
diff --git a/absl/debugging/internal/address_is_readable.h b/absl/debugging/internal/address_is_readable.h
index ca8003e6292a..4bbaf4d69bd8 100644
--- a/absl/debugging/internal/address_is_readable.h
+++ b/absl/debugging/internal/address_is_readable.h
@@ -15,7 +15,10 @@
 #ifndef ABSL_DEBUGGING_INTERNAL_ADDRESS_IS_READABLE_H_
 #define ABSL_DEBUGGING_INTERNAL_ADDRESS_IS_READABLE_H_
 
+#include "absl/base/config.h"
+
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace debugging_internal {
 
 // Return whether the byte at *addr is readable, without faulting.
@@ -23,6 +26,7 @@ namespace debugging_internal {
 bool AddressIsReadable(const void *addr);
 
 }  // namespace debugging_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_DEBUGGING_INTERNAL_ADDRESS_IS_READABLE_H_
diff --git a/absl/debugging/internal/demangle.cc b/absl/debugging/internal/demangle.cc
index 3809e4960e2c..fc615c3f583b 100644
--- a/absl/debugging/internal/demangle.cc
+++ b/absl/debugging/internal/demangle.cc
@@ -24,6 +24,7 @@
 #include <limits>
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace debugging_internal {
 
 typedef struct {
@@ -1890,4 +1891,5 @@ bool Demangle(const char *mangled, char *out, int out_size) {
 }
 
 }  // namespace debugging_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/debugging/internal/demangle.h b/absl/debugging/internal/demangle.h
index 81bb0dfd4bda..c314d9bc237c 100644
--- a/absl/debugging/internal/demangle.h
+++ b/absl/debugging/internal/demangle.h
@@ -53,7 +53,10 @@
 #ifndef ABSL_DEBUGGING_INTERNAL_DEMANGLE_H_
 #define ABSL_DEBUGGING_INTERNAL_DEMANGLE_H_
 
+#include "absl/base/config.h"
+
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace debugging_internal {
 
 // Demangle `mangled`.  On success, return true and write the
@@ -62,6 +65,7 @@ namespace debugging_internal {
 bool Demangle(const char *mangled, char *out, int out_size);
 
 }  // namespace debugging_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_DEBUGGING_INTERNAL_DEMANGLE_H_
diff --git a/absl/debugging/internal/demangle_test.cc b/absl/debugging/internal/demangle_test.cc
index a68ce3249bcb..c6f1ce184c10 100644
--- a/absl/debugging/internal/demangle_test.cc
+++ b/absl/debugging/internal/demangle_test.cc
@@ -23,6 +23,7 @@
 #include "absl/memory/memory.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace debugging_internal {
 namespace {
 
@@ -190,4 +191,5 @@ TEST(DemangleRegression, DeeplyNestedArrayType) {
 
 }  // namespace
 }  // namespace debugging_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/debugging/internal/elf_mem_image.cc b/absl/debugging/internal/elf_mem_image.cc
index e7408bca8e42..24cc01302dc5 100644
--- a/absl/debugging/internal/elf_mem_image.cc
+++ b/absl/debugging/internal/elf_mem_image.cc
@@ -38,6 +38,7 @@
 #define VERSYM_VERSION 0x7fff
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace debugging_internal {
 
 namespace {
@@ -375,6 +376,7 @@ void ElfMemImage::SymbolIterator::Update(int increment) {
 }
 
 }  // namespace debugging_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_HAVE_ELF_MEM_IMAGE
diff --git a/absl/debugging/internal/elf_mem_image.h b/absl/debugging/internal/elf_mem_image.h
index d84200db1e1a..46bfade3503e 100644
--- a/absl/debugging/internal/elf_mem_image.h
+++ b/absl/debugging/internal/elf_mem_image.h
@@ -23,6 +23,8 @@
 // used.
 #include <climits>
 
+#include "absl/base/config.h"
+
 // Maybe one day we can rewrite this file not to require the elf
 // symbol extensions in glibc, but for right now we need them.
 #ifdef ABSL_HAVE_ELF_MEM_IMAGE
@@ -39,6 +41,7 @@
 #include <link.h>  // for ElfW
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace debugging_internal {
 
 // An in-memory ELF image (may not exist on disk).
@@ -123,6 +126,7 @@ class ElfMemImage {
 };
 
 }  // namespace debugging_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_HAVE_ELF_MEM_IMAGE
diff --git a/absl/debugging/internal/examine_stack.cc b/absl/debugging/internal/examine_stack.cc
index 1ebc788fe3d6..22f41b46ee2e 100644
--- a/absl/debugging/internal/examine_stack.cc
+++ b/absl/debugging/internal/examine_stack.cc
@@ -30,6 +30,7 @@
 #include "absl/debugging/symbolize.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace debugging_internal {
 
 // Returns the program counter from signal context, nullptr if
@@ -150,4 +151,5 @@ void DumpPCAndFrameSizesAndStackTrace(
 }
 
 }  // namespace debugging_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/debugging/internal/examine_stack.h b/absl/debugging/internal/examine_stack.h
index 56c9763eb733..393369131f1e 100644
--- a/absl/debugging/internal/examine_stack.h
+++ b/absl/debugging/internal/examine_stack.h
@@ -17,7 +17,10 @@
 #ifndef ABSL_DEBUGGING_INTERNAL_EXAMINE_STACK_H_
 #define ABSL_DEBUGGING_INTERNAL_EXAMINE_STACK_H_
 
+#include "absl/base/config.h"
+
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace debugging_internal {
 
 // Returns the program counter from signal context, or nullptr if
@@ -33,6 +36,7 @@ void DumpPCAndFrameSizesAndStackTrace(
     void (*writerfn)(const char*, void*), void* writerfn_arg);
 
 }  // namespace debugging_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_DEBUGGING_INTERNAL_EXAMINE_STACK_H_
diff --git a/absl/debugging/internal/stack_consumption.cc b/absl/debugging/internal/stack_consumption.cc
index d4703264a666..875ca6d91f7f 100644
--- a/absl/debugging/internal/stack_consumption.cc
+++ b/absl/debugging/internal/stack_consumption.cc
@@ -27,6 +27,7 @@
 #include "absl/base/internal/raw_logging.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace debugging_internal {
 namespace {
 
@@ -177,6 +178,7 @@ int GetSignalHandlerStackConsumption(void (*signal_handler)(int)) {
 }
 
 }  // namespace debugging_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_INTERNAL_HAVE_DEBUGGING_STACK_CONSUMPTION
diff --git a/absl/debugging/internal/stack_consumption.h b/absl/debugging/internal/stack_consumption.h
index b860a3c1a17e..5e60ec422916 100644
--- a/absl/debugging/internal/stack_consumption.h
+++ b/absl/debugging/internal/stack_consumption.h
@@ -18,6 +18,8 @@
 #ifndef ABSL_DEBUGGING_INTERNAL_STACK_CONSUMPTION_H_
 #define ABSL_DEBUGGING_INTERNAL_STACK_CONSUMPTION_H_
 
+#include "absl/base/config.h"
+
 // The code in this module is not portable.
 // Use this feature test macro to detect its availability.
 #ifdef ABSL_INTERNAL_HAVE_DEBUGGING_STACK_CONSUMPTION
@@ -27,6 +29,7 @@
 #define ABSL_INTERNAL_HAVE_DEBUGGING_STACK_CONSUMPTION 1
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace debugging_internal {
 
 // Returns the stack consumption in bytes for the code exercised by
@@ -38,6 +41,7 @@ namespace debugging_internal {
 int GetSignalHandlerStackConsumption(void (*signal_handler)(int));
 
 }  // namespace debugging_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_INTERNAL_HAVE_DEBUGGING_STACK_CONSUMPTION
diff --git a/absl/debugging/internal/stack_consumption_test.cc b/absl/debugging/internal/stack_consumption_test.cc
index 68bfa126e23b..80445bf43aab 100644
--- a/absl/debugging/internal/stack_consumption_test.cc
+++ b/absl/debugging/internal/stack_consumption_test.cc
@@ -23,6 +23,7 @@
 #include "absl/base/internal/raw_logging.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace debugging_internal {
 namespace {
 
@@ -43,6 +44,7 @@ TEST(SignalHandlerStackConsumptionTest, MeasuresStackConsumption) {
 
 }  // namespace
 }  // namespace debugging_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_INTERNAL_HAVE_DEBUGGING_STACK_CONSUMPTION
diff --git a/absl/debugging/internal/stacktrace_aarch64-inl.inc b/absl/debugging/internal/stacktrace_aarch64-inl.inc
index 7ed6b3eb82dc..411ea308e90b 100644
--- a/absl/debugging/internal/stacktrace_aarch64-inl.inc
+++ b/absl/debugging/internal/stacktrace_aarch64-inl.inc
@@ -180,11 +180,13 @@ static int UnwindImpl(void** result, int* sizes, int max_depth, int skip_count,
 }
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace debugging_internal {
 bool StackTraceWorksForTest() {
   return true;
 }
 }  // namespace debugging_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_DEBUGGING_INTERNAL_STACKTRACE_AARCH64_INL_H_
diff --git a/absl/debugging/internal/stacktrace_arm-inl.inc b/absl/debugging/internal/stacktrace_arm-inl.inc
index c84083379bb2..fffda968dde6 100644
--- a/absl/debugging/internal/stacktrace_arm-inl.inc
+++ b/absl/debugging/internal/stacktrace_arm-inl.inc
@@ -113,11 +113,13 @@ static int UnwindImpl(void** result, int* sizes, int max_depth, int skip_count,
 }
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace debugging_internal {
 bool StackTraceWorksForTest() {
   return false;
 }
 }  // namespace debugging_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_DEBUGGING_INTERNAL_STACKTRACE_ARM_INL_H_
diff --git a/absl/debugging/internal/stacktrace_generic-inl.inc b/absl/debugging/internal/stacktrace_generic-inl.inc
index 81a49ef2e860..ac034c9f5b2e 100644
--- a/absl/debugging/internal/stacktrace_generic-inl.inc
+++ b/absl/debugging/internal/stacktrace_generic-inl.inc
@@ -87,11 +87,13 @@ static int UnwindImpl(void** result, int* sizes, int max_depth, int skip_count,
 }
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace debugging_internal {
 bool StackTraceWorksForTest() {
   return true;
 }
 }  // namespace debugging_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_DEBUGGING_INTERNAL_STACKTRACE_GENERIC_INL_H_
diff --git a/absl/debugging/internal/stacktrace_powerpc-inl.inc b/absl/debugging/internal/stacktrace_powerpc-inl.inc
index 3a070ee45d4b..2e7c2f404f20 100644
--- a/absl/debugging/internal/stacktrace_powerpc-inl.inc
+++ b/absl/debugging/internal/stacktrace_powerpc-inl.inc
@@ -236,11 +236,13 @@ static int UnwindImpl(void** result, int* sizes, int max_depth, int skip_count,
 }
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace debugging_internal {
 bool StackTraceWorksForTest() {
   return true;
 }
 }  // namespace debugging_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_DEBUGGING_INTERNAL_STACKTRACE_POWERPC_INL_H_
diff --git a/absl/debugging/internal/stacktrace_unimplemented-inl.inc b/absl/debugging/internal/stacktrace_unimplemented-inl.inc
index e256fdd4ae76..5b8fb191b65a 100644
--- a/absl/debugging/internal/stacktrace_unimplemented-inl.inc
+++ b/absl/debugging/internal/stacktrace_unimplemented-inl.inc
@@ -12,11 +12,13 @@ static int UnwindImpl(void** /* result */, int* /* sizes */,
 }
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace debugging_internal {
 bool StackTraceWorksForTest() {
   return false;
 }
 }  // namespace debugging_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_DEBUGGING_INTERNAL_STACKTRACE_UNIMPLEMENTED_INL_H_
diff --git a/absl/debugging/internal/stacktrace_win32-inl.inc b/absl/debugging/internal/stacktrace_win32-inl.inc
index 247e7428df8b..9c2c558044d8 100644
--- a/absl/debugging/internal/stacktrace_win32-inl.inc
+++ b/absl/debugging/internal/stacktrace_win32-inl.inc
@@ -73,11 +73,13 @@ static int UnwindImpl(void** result, int* sizes, int max_depth, int skip_count,
 }
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace debugging_internal {
 bool StackTraceWorksForTest() {
   return false;
 }
 }  // namespace debugging_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_DEBUGGING_INTERNAL_STACKTRACE_WIN32_INL_H_
diff --git a/absl/debugging/internal/stacktrace_x86-inl.inc b/absl/debugging/internal/stacktrace_x86-inl.inc
index 9494441e1cff..972febdd6fb9 100644
--- a/absl/debugging/internal/stacktrace_x86-inl.inc
+++ b/absl/debugging/internal/stacktrace_x86-inl.inc
@@ -330,11 +330,13 @@ static int UnwindImpl(void **result, int *sizes, int max_depth, int skip_count,
 }
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace debugging_internal {
 bool StackTraceWorksForTest() {
   return true;
 }
 }  // namespace debugging_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_DEBUGGING_INTERNAL_STACKTRACE_X86_INL_INC_
diff --git a/absl/debugging/internal/symbolize.h b/absl/debugging/internal/symbolize.h
index 3e537893097d..5d0858b5c7e1 100644
--- a/absl/debugging/internal/symbolize.h
+++ b/absl/debugging/internal/symbolize.h
@@ -21,6 +21,8 @@
 #include <cstddef>
 #include <cstdint>
 
+#include "absl/base/config.h"
+
 #ifdef ABSL_INTERNAL_HAVE_ELF_SYMBOLIZE
 #error ABSL_INTERNAL_HAVE_ELF_SYMBOLIZE cannot be directly set
 #elif defined(__ELF__) && defined(__GLIBC__) && !defined(__native_client__) && \
@@ -33,6 +35,7 @@
 #include <string>
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace debugging_internal {
 
 // Iterates over all sections, invoking callback on each with the section name
@@ -51,11 +54,13 @@ bool GetSectionHeaderByName(int fd, const char *name, size_t name_len,
                             ElfW(Shdr) *out);
 
 }  // namespace debugging_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_INTERNAL_HAVE_ELF_SYMBOLIZE
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace debugging_internal {
 
 struct SymbolDecoratorArgs {
@@ -117,6 +122,7 @@ bool GetFileMappingHint(const void** start,
                         const char** filename);
 
 }  // namespace debugging_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_DEBUGGING_INTERNAL_SYMBOLIZE_H_
diff --git a/absl/debugging/internal/vdso_support.cc b/absl/debugging/internal/vdso_support.cc
index d13ef25d3f88..1e8a78ac9c1f 100644
--- a/absl/debugging/internal/vdso_support.cc
+++ b/absl/debugging/internal/vdso_support.cc
@@ -38,6 +38,7 @@
 #endif
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace debugging_internal {
 
 ABSL_CONST_INIT
@@ -187,6 +188,7 @@ static class VDSOInitHelper {
 } vdso_init_helper;
 
 }  // namespace debugging_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_HAVE_VDSO_SUPPORT
diff --git a/absl/debugging/internal/vdso_support.h b/absl/debugging/internal/vdso_support.h
index 9895b48dd368..6562c6c2350a 100644
--- a/absl/debugging/internal/vdso_support.h
+++ b/absl/debugging/internal/vdso_support.h
@@ -53,6 +53,7 @@
 #endif
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace debugging_internal {
 
 // NOTE: this class may be used from within tcmalloc, and can not
@@ -149,6 +150,7 @@ class VDSOSupport {
 int GetCPU();
 
 }  // namespace debugging_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_HAVE_ELF_MEM_IMAGE
diff --git a/absl/debugging/leak_check.cc b/absl/debugging/leak_check.cc
index ffe3d1bda9d6..ff9049559d4d 100644
--- a/absl/debugging/leak_check.cc
+++ b/absl/debugging/leak_check.cc
@@ -21,12 +21,14 @@
 #ifndef LEAK_SANITIZER
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 bool HaveLeakSanitizer() { return false; }
 void DoIgnoreLeak(const void*) { }
 void RegisterLivePointers(const void*, size_t) { }
 void UnRegisterLivePointers(const void*, size_t) { }
 LeakCheckDisabler::LeakCheckDisabler() { }
 LeakCheckDisabler::~LeakCheckDisabler() { }
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #else
@@ -34,6 +36,7 @@ LeakCheckDisabler::~LeakCheckDisabler() { }
 #include <sanitizer/lsan_interface.h>
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 bool HaveLeakSanitizer() { return true; }
 void DoIgnoreLeak(const void* ptr) { __lsan_ignore_object(ptr); }
 void RegisterLivePointers(const void* ptr, size_t size) {
@@ -44,6 +47,7 @@ void UnRegisterLivePointers(const void* ptr, size_t size) {
 }
 LeakCheckDisabler::LeakCheckDisabler() { __lsan_disable(); }
 LeakCheckDisabler::~LeakCheckDisabler() { __lsan_enable(); }
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // LEAK_SANITIZER
diff --git a/absl/debugging/leak_check.h b/absl/debugging/leak_check.h
index 4d489c582849..7a5a22dd1caf 100644
--- a/absl/debugging/leak_check.h
+++ b/absl/debugging/leak_check.h
@@ -32,7 +32,10 @@
 
 #include <cstddef>
 
+#include "absl/base/config.h"
+
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // HaveLeakSanitizer()
 //
@@ -104,6 +107,7 @@ void RegisterLivePointers(const void* ptr, size_t size);
 // `RegisterLivePointers()`, enabling leak checking of those pointers.
 void UnRegisterLivePointers(const void* ptr, size_t size);
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_DEBUGGING_LEAK_CHECK_H_
diff --git a/absl/debugging/stacktrace.cc b/absl/debugging/stacktrace.cc
index 9de8782f4cae..1f7c7d82b2d2 100644
--- a/absl/debugging/stacktrace.cc
+++ b/absl/debugging/stacktrace.cc
@@ -57,6 +57,7 @@
 #endif
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace {
 
 typedef int (*Unwinder)(void**, int*, int, int, const void*, int*);
@@ -135,4 +136,5 @@ int DefaultStackUnwinder(void** pcs, int* sizes, int depth, int skip,
   return n;
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/debugging/stacktrace.h b/absl/debugging/stacktrace.h
index cd8fae76d536..0ec0ffdabd42 100644
--- a/absl/debugging/stacktrace.h
+++ b/absl/debugging/stacktrace.h
@@ -31,7 +31,10 @@
 #ifndef ABSL_DEBUGGING_STACKTRACE_H_
 #define ABSL_DEBUGGING_STACKTRACE_H_
 
+#include "absl/base/config.h"
+
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // GetStackFrames()
 //
@@ -222,6 +225,7 @@ namespace debugging_internal {
 // working.
 extern bool StackTraceWorksForTest();
 }  // namespace debugging_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_DEBUGGING_STACKTRACE_H_
diff --git a/absl/debugging/symbolize.h b/absl/debugging/symbolize.h
index a73dbd9eabed..a8ff374049f3 100644
--- a/absl/debugging/symbolize.h
+++ b/absl/debugging/symbolize.h
@@ -55,6 +55,7 @@
 #include "absl/debugging/internal/symbolize.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // InitializeSymbolizer()
 //
@@ -92,6 +93,7 @@ void InitializeSymbolizer(const char* argv0);
 //  }
 bool Symbolize(const void *pc, char *out, int out_size);
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_DEBUGGING_SYMBOLIZE_H_
diff --git a/absl/debugging/symbolize_elf.inc b/absl/debugging/symbolize_elf.inc
index 14f0c9723a33..c371635ffa0a 100644
--- a/absl/debugging/symbolize_elf.inc
+++ b/absl/debugging/symbolize_elf.inc
@@ -76,6 +76,7 @@
 #include "absl/debugging/internal/vdso_support.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // Value of argv[0]. Used by MaybeInitializeObjFile().
 static char *argv0_value = nullptr;
@@ -1475,4 +1476,5 @@ bool Symbolize(const void *pc, char *out, int out_size) {
   return ok;
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/debugging/symbolize_unimplemented.inc b/absl/debugging/symbolize_unimplemented.inc
index 7c580fe447ed..db24456b0afa 100644
--- a/absl/debugging/symbolize_unimplemented.inc
+++ b/absl/debugging/symbolize_unimplemented.inc
@@ -17,6 +17,7 @@
 #include "absl/base/internal/raw_logging.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 namespace debugging_internal {
 
@@ -35,4 +36,5 @@ bool GetFileMappingHint(const void **, const void **, uint64_t *, const char **)
 void InitializeSymbolizer(const char*) {}
 bool Symbolize(const void *, char *, int) { return false; }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/debugging/symbolize_win32.inc b/absl/debugging/symbolize_win32.inc
index bd6fbd5ef463..c3df46f606c2 100644
--- a/absl/debugging/symbolize_win32.inc
+++ b/absl/debugging/symbolize_win32.inc
@@ -31,6 +31,7 @@
 #include "absl/base/internal/raw_logging.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 static HANDLE process = NULL;
 
@@ -76,4 +77,5 @@ bool Symbolize(const void* pc, char* out, int out_size) {
   return true;
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/flags/declare.h b/absl/flags/declare.h
index 4926a09ef4dd..f7509ce77ffc 100644
--- a/absl/flags/declare.h
+++ b/absl/flags/declare.h
@@ -28,6 +28,7 @@
 #include "absl/strings/string_view.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace flags_internal {
 
 // absl::Flag<T> represents a flag of type 'T' created by ABSL_FLAG.
@@ -47,6 +48,7 @@ template <typename T>
 using Flag = flags_internal::Flag<T>;
 #endif
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 // ABSL_DECLARE_FLAG()
diff --git a/absl/flags/flag.cc b/absl/flags/flag.cc
index 37bbce233117..7faa7ade0d0d 100644
--- a/absl/flags/flag.cc
+++ b/absl/flags/flag.cc
@@ -18,6 +18,7 @@
 #include <cstring>
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // We want to validate the type mismatch between type definition and
 // declaration. The lock-free implementation does not allow us to do it,
@@ -55,4 +56,5 @@ absl::Mutex* GetGlobalConstructionGuard() { return &construction_guard; }
 
 #endif
 
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/flags/flag.h b/absl/flags/flag.h
index 52c3cede690a..b6fbd116ed2f 100644
--- a/absl/flags/flag.h
+++ b/absl/flags/flag.h
@@ -38,6 +38,7 @@
 #include "absl/flags/marshalling.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // Flag
 //
@@ -219,6 +220,7 @@ void SetFlag(absl::Flag<T>* flag, const V& v) {
   flag->Set(value);
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 
diff --git a/absl/flags/flag_test_defs.cc b/absl/flags/flag_test_defs.cc
index 3366c5803279..49f91dee3922 100644
--- a/absl/flags/flag_test_defs.cc
+++ b/absl/flags/flag_test_defs.cc
@@ -20,3 +20,5 @@
 
 ABSL_FLAG(int, mistyped_int_flag, 0, "");
 ABSL_FLAG(std::string, mistyped_string_flag, "", "");
+ABSL_RETIRED_FLAG(bool, old_bool_flag, true,
+                  "repetition of retired flag definition");
diff --git a/absl/flags/internal/commandlineflag.cc b/absl/flags/internal/commandlineflag.cc
index 88f91e16d196..09249274c3e7 100644
--- a/absl/flags/internal/commandlineflag.cc
+++ b/absl/flags/internal/commandlineflag.cc
@@ -18,6 +18,7 @@
 #include "absl/flags/usage_config.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace flags_internal {
 
 // The help message indicating that the commandline flag has been
@@ -57,4 +58,5 @@ std::string CommandLineFlag::Filename() const {
 }
 
 }  // namespace flags_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/flags/internal/commandlineflag.h b/absl/flags/internal/commandlineflag.h
index 7964f1bf8c4a..49e13d1e726b 100644
--- a/absl/flags/internal/commandlineflag.h
+++ b/absl/flags/internal/commandlineflag.h
@@ -23,6 +23,7 @@
 #include "absl/types/optional.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace flags_internal {
 
 // Type-specific operations, eg., parsing, copying, etc. are provided
@@ -158,7 +159,7 @@ class CommandLineFlag {
       : name_(name), filename_(filename) {}
 
   // Virtual destructor
-  virtual void Destroy() const = 0;
+  virtual void Destroy() = 0;
 
   // Not copyable/assignable.
   CommandLineFlag(const CommandLineFlag&) = delete;
@@ -280,6 +281,7 @@ class CommandLineFlag {
   A(float)
 
 }  // namespace flags_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_FLAGS_INTERNAL_COMMANDLINEFLAG_H_
diff --git a/absl/flags/internal/flag.cc b/absl/flags/internal/flag.cc
index 435cc362478f..599bd7a45561 100644
--- a/absl/flags/internal/flag.cc
+++ b/absl/flags/internal/flag.cc
@@ -19,6 +19,7 @@
 #include "absl/synchronization/mutex.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace flags_internal {
 namespace {
 
@@ -34,20 +35,40 @@ bool ShouldValidateFlagValue(const CommandLineFlag& flag) {
   return true;
 }
 
+// RAII helper used to temporarily unlock and relock `absl::Mutex`.
+// This is used when we need to ensure that locks are released while
+// invoking user supplied callbacks and then reacquired, since callbacks may
+// need to acquire these locks themselves.
+class MutexRelock {
+ public:
+  explicit MutexRelock(absl::Mutex* mu) : mu_(mu) { mu_->Unlock(); }
+  ~MutexRelock() { mu_->Lock(); }
+
+  MutexRelock(const MutexRelock&) = delete;
+  MutexRelock& operator=(const MutexRelock&) = delete;
+
+ private:
+  absl::Mutex* mu_;
+};
+
+// This global lock guards the initialization and destruction of data_guard_,
+// which is used to guard the other Flag data.
+ABSL_CONST_INIT static absl::Mutex flag_mutex_lifetime_guard(absl::kConstInit);
+
 }  // namespace
 
 void FlagImpl::Init() {
-  ABSL_CONST_INIT static absl::Mutex init_lock(absl::kConstInit);
-
   {
-    absl::MutexLock lock(&init_lock);
+    absl::MutexLock lock(&flag_mutex_lifetime_guard);
 
-    if (locks_ == nullptr) {  // Must initialize Mutexes for this flag.
-      locks_ = new FlagImpl::CommandLineFlagLocks;
+    // Must initialize data guard for this flag.
+    if (!is_data_guard_inited_) {
+      new (&data_guard_) absl::Mutex;
+      is_data_guard_inited_ = true;
     }
   }
 
-  absl::MutexLock lock(&locks_->primary_mu);
+  absl::MutexLock lock(reinterpret_cast<absl::Mutex*>(&data_guard_));
 
   if (cur_ != nullptr) {
     inited_.store(true, std::memory_order_release);
@@ -67,21 +88,29 @@ absl::Mutex* FlagImpl::DataGuard() const {
     const_cast<FlagImpl*>(this)->Init();
   }
 
-  // All fields initialized; locks_ is therefore safe to read.
-  return &locks_->primary_mu;
+  // data_guard_ is initialized.
+  return reinterpret_cast<absl::Mutex*>(&data_guard_);
 }
 
-void FlagImpl::Destroy() const {
+void FlagImpl::Destroy() {
   {
     absl::MutexLock l(DataGuard());
 
     // Values are heap allocated for Abseil Flags.
     if (cur_) Delete(op_, cur_);
-    if (def_kind_ == FlagDefaultSrcKind::kDynamicValue)
+
+    // Release the dynamically allocated default value if any.
+    if (def_kind_ == FlagDefaultSrcKind::kDynamicValue) {
       Delete(op_, default_src_.dynamic_value);
+    }
+
+    // If this flag has an assigned callback, release callback data.
+    if (callback_data_) delete callback_data_;
   }
 
-  delete locks_;
+  absl::MutexLock l(&flag_mutex_lifetime_guard);
+  DataGuard()->~Mutex();
+  is_data_guard_inited_ = false;
 }
 
 std::unique_ptr<void, DynValueDeleter> FlagImpl::MakeInitValue() const {
@@ -126,13 +155,20 @@ void FlagImpl::SetCallback(
     const flags_internal::FlagCallback mutation_callback) {
   absl::MutexLock l(DataGuard());
 
-  callback_ = mutation_callback;
+  if (callback_data_ == nullptr) {
+    callback_data_ = new CallbackData;
+  }
+  callback_data_->func = mutation_callback;
 
   InvokeCallback();
 }
 
 void FlagImpl::InvokeCallback() const {
-  if (!callback_) return;
+  if (!callback_data_) return;
+
+  // Make a copy of the C-style function pointer that we are about to invoke
+  // before we release the lock guarding it.
+  FlagCallback cb = callback_data_->func;
 
   // If the flag has a mutation callback this function invokes it. While the
   // callback is being invoked the primary flag's mutex is unlocked and it is
@@ -145,14 +181,9 @@ void FlagImpl::InvokeCallback() const {
   // and it also can be different by the time the callback invocation is
   // completed. Requires that *primary_lock be held in exclusive mode; it may be
   // released and reacquired by the implementation.
-  DataGuard()->Unlock();
-
-  {
-    absl::MutexLock lock(&locks_->callback_mu);
-    callback_();
-  }
-
-  DataGuard()->Lock();
+  MutexRelock relock(DataGuard());
+  absl::MutexLock lock(&callback_data_->guard);
+  cb();
 }
 
 bool FlagImpl::RestoreState(const CommandLineFlag& flag, const void* value,
@@ -177,12 +208,13 @@ bool FlagImpl::RestoreState(const CommandLineFlag& flag, const void* value,
 }
 
 // Attempts to parse supplied `value` string using parsing routine in the `flag`
-// argument. If parsing successful, this function stores the parsed value in
-// 'dst' assuming it is a pointer to the flag's value type. In case if any error
-// is encountered in either step, the error message is stored in 'err'
-bool FlagImpl::TryParse(const CommandLineFlag& flag, void* dst,
+// argument. If parsing successful, this function replaces the dst with newly
+// parsed value. In case if any error is encountered in either step, the error
+// message is stored in 'err'
+bool FlagImpl::TryParse(const CommandLineFlag& flag, void** dst,
                         absl::string_view value, std::string* err) const {
   auto tentative_value = MakeInitValue();
+
   std::string parse_err;
   if (!Parse(marshalling_op_, value, tentative_value.get(), &parse_err)) {
     auto type_name = flag.Typename();
@@ -194,7 +226,10 @@ bool FlagImpl::TryParse(const CommandLineFlag& flag, void* dst,
     return false;
   }
 
-  Copy(op_, tentative_value.get(), dst);
+  void* old_val = *dst;
+  *dst = tentative_value.release();
+  tentative_value.reset(old_val);
+
   return true;
 }
 
@@ -274,7 +309,7 @@ bool FlagImpl::SetFromString(const CommandLineFlag& flag,
   switch (set_mode) {
     case SET_FLAGS_VALUE: {
       // set or modify the flag's value
-      if (!TryParse(flag, cur_, value, err)) return false;
+      if (!TryParse(flag, &cur_, value, err)) return false;
       modified_ = true;
       counter_++;
       StoreAtomic();
@@ -288,7 +323,7 @@ bool FlagImpl::SetFromString(const CommandLineFlag& flag,
     case SET_FLAG_IF_DEFAULT: {
       // set the flag's value, but only if it hasn't been set by someone else
       if (!modified_) {
-        if (!TryParse(flag, cur_, value, err)) return false;
+        if (!TryParse(flag, &cur_, value, err)) return false;
         modified_ = true;
         counter_++;
         StoreAtomic();
@@ -305,18 +340,19 @@ bool FlagImpl::SetFromString(const CommandLineFlag& flag,
       break;
     }
     case SET_FLAGS_DEFAULT: {
-      // Flag's new default-value.
-      auto new_default_value = MakeInitValue();
-
-      if (!TryParse(flag, new_default_value.get(), value, err)) return false;
-
       if (def_kind_ == FlagDefaultSrcKind::kDynamicValue) {
-        // Release old default value.
-        Delete(op_, default_src_.dynamic_value);
-      }
+        if (!TryParse(flag, &default_src_.dynamic_value, value, err)) {
+          return false;
+        }
+      } else {
+        void* new_default_val = nullptr;
+        if (!TryParse(flag, &new_default_val, value, err)) {
+          return false;
+        }
 
-      default_src_.dynamic_value = new_default_value.release();
-      def_kind_ = FlagDefaultSrcKind::kDynamicValue;
+        default_src_.dynamic_value = new_default_val;
+        def_kind_ = FlagDefaultSrcKind::kDynamicValue;
+      }
 
       if (!modified_) {
         // Need to set both default value *and* current, in this case
@@ -361,4 +397,5 @@ bool FlagImpl::ValidateInputValue(absl::string_view value) const {
 }
 
 }  // namespace flags_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/flags/internal/flag.h b/absl/flags/internal/flag.h
index 947a8cadaf2d..20de406f4615 100644
--- a/absl/flags/internal/flag.h
+++ b/absl/flags/internal/flag.h
@@ -27,6 +27,7 @@
 #include "absl/synchronization/mutex.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace flags_internal {
 
 constexpr int64_t AtomicInit() { return 0xababababababababll; }
@@ -156,10 +157,11 @@ class FlagImpl {
         help_(help.source),
         help_source_kind_(help.kind),
         def_kind_(flags_internal::FlagDefaultSrcKind::kGenFunc),
-        default_src_(default_value_gen) {}
+        default_src_(default_value_gen),
+        data_guard_{} {}
 
   // Forces destruction of the Flag's data.
-  void Destroy() const;
+  void Destroy();
 
   // Constant access methods
   std::string Help() const;
@@ -170,9 +172,10 @@ class FlagImpl {
   void Read(const CommandLineFlag& flag, void* dst,
             const flags_internal::FlagOpFn dst_op) const
       ABSL_LOCKS_EXCLUDED(*DataGuard());
-  // Attempts to parse supplied `value` std::string.
-  bool TryParse(const CommandLineFlag& flag, void* dst, absl::string_view value,
-                std::string* err) const
+  // Attempts to parse supplied `value` std::string. If parsing is successful, then
+  // it replaces `dst` with the new value.
+  bool TryParse(const CommandLineFlag& flag, void** dst,
+                absl::string_view value, std::string* err) const
       ABSL_EXCLUSIVE_LOCKS_REQUIRED(*DataGuard());
   template <typename T>
   bool AtomicGet(T* v) const {
@@ -226,8 +229,7 @@ class FlagImpl {
   void Init();
   // Ensures that the lazily initialized data is initialized,
   // and returns pointer to the mutex guarding flags data.
-  absl::Mutex* DataGuard() const ABSL_LOCK_RETURNED(locks_->primary_mu);
-
+  absl::Mutex* DataGuard() const ABSL_LOCK_RETURNED((absl::Mutex*)&data_guard_);
   // Returns heap allocated value of type T initialized with default value.
   std::unique_ptr<void, DynValueDeleter> MakeInitValue() const
       ABSL_EXCLUSIVE_LOCKS_REQUIRED(*DataGuard());
@@ -239,9 +241,12 @@ class FlagImpl {
   // Indicates if help message was supplied as literal or generator func.
   const FlagHelpSrcKind help_source_kind_;
 
-  // Mutable Flag's data. (guarded by DataGuard()).
-  // Indicates that locks_ and cur_ fields have been lazily initialized.
+  // Indicates that the Flag state is initialized.
   std::atomic<bool> inited_{false};
+  // Mutable Flag state (guarded by data_guard_).
+  // Additional bool to protect against multiple concurrent constructions
+  // of `data_guard_`.
+  bool is_data_guard_inited_ = false;
   // Has flag value been modified?
   bool modified_ ABSL_GUARDED_BY(*DataGuard()) = false;
   // Specified on command line.
@@ -261,22 +266,20 @@ class FlagImpl {
   // For some types, a copy of the current value is kept in an atomically
   // accessible field.
   std::atomic<int64_t> atomic_{flags_internal::AtomicInit()};
-  // Mutation callback
-  FlagCallback callback_ = nullptr;
-
-  // Lazily initialized mutexes for this flag value.  We cannot inline a
-  // SpinLock or Mutex here because those have non-constexpr constructors and
-  // so would prevent constant initialization of this type.
-  // TODO(rogeeff): fix it once Mutex has constexpr constructor
-  // The following struct contains the locks in a CommandLineFlag struct.
-  // They are in a separate struct that is lazily allocated to avoid problems
-  // with static initialization and to avoid multiple allocations.
-  struct CommandLineFlagLocks {
-    absl::Mutex primary_mu;   // protects several fields in CommandLineFlag
-    absl::Mutex callback_mu;  // used to serialize callbacks
-  };
 
-  CommandLineFlagLocks* locks_ = nullptr;  // locks, laziliy allocated.
+  struct CallbackData {
+    FlagCallback func;
+    absl::Mutex guard;  // Guard for concurrent callback invocations.
+  };
+  CallbackData* callback_data_ ABSL_GUARDED_BY(*DataGuard()) = nullptr;
+  // This is reserved space for an absl::Mutex to guard flag data. It will be
+  // initialized in FlagImpl::Init via placement new.
+  // We can't use "absl::Mutex data_guard_", since this class is not literal.
+  // We do not want to use "absl::Mutex* data_guard_", since this would require
+  // heap allocation during initialization, which is both slows program startup
+  // and can fail. Using reserved space + placement new allows us to avoid both
+  // problems.
+  alignas(absl::Mutex) mutable char data_guard_[sizeof(absl::Mutex)];
 };
 
 // This is "unspecified" implementation of absl::Flag<T> type.
@@ -354,7 +357,7 @@ class Flag final : public flags_internal::CommandLineFlag {
  private:
   friend class FlagState<T>;
 
-  void Destroy() const override { impl_.Destroy(); }
+  void Destroy() override { impl_.Destroy(); }
 
   void Read(void* dst) const override {
     impl_.Read(*this, dst, &flags_internal::FlagOps<T>);
@@ -414,6 +417,7 @@ T* MakeFromDefaultValue(EmptyBraces) {
 }
 
 }  // namespace flags_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_FLAGS_INTERNAL_FLAG_H_
diff --git a/absl/flags/internal/parse.h b/absl/flags/internal/parse.h
index fd3aca61f408..e534635b700a 100644
--- a/absl/flags/internal/parse.h
+++ b/absl/flags/internal/parse.h
@@ -27,6 +27,7 @@ ABSL_DECLARE_FLAG(std::vector<std::string>, tryfromenv);
 ABSL_DECLARE_FLAG(std::vector<std::string>, undefok);
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace flags_internal {
 
 enum class ArgvListAction { kRemoveParsedArgs, kKeepParsedArgs };
@@ -43,6 +44,7 @@ std::vector<char*> ParseCommandLineImpl(int argc, char* argv[],
                                         OnUndefinedFlag on_undef_flag);
 
 }  // namespace flags_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_FLAGS_INTERNAL_PARSE_H_
diff --git a/absl/flags/internal/path_util.h b/absl/flags/internal/path_util.h
index 5615c0e6c590..4169637731e5 100644
--- a/absl/flags/internal/path_util.h
+++ b/absl/flags/internal/path_util.h
@@ -20,6 +20,7 @@
 #include "absl/strings/string_view.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace flags_internal {
 
 // A portable interface that returns the basename of the filename passed as an
@@ -55,6 +56,7 @@ inline absl::string_view Package(absl::string_view filename) {
 }
 
 }  // namespace flags_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_FLAGS_INTERNAL_PATH_UTIL_H_
diff --git a/absl/flags/internal/program_name.cc b/absl/flags/internal/program_name.cc
index f0811f144868..df0c3309d37c 100644
--- a/absl/flags/internal/program_name.cc
+++ b/absl/flags/internal/program_name.cc
@@ -21,6 +21,7 @@
 #include "absl/synchronization/mutex.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace flags_internal {
 
 ABSL_CONST_INIT static absl::Mutex program_name_guard(absl::kConstInit);
@@ -50,4 +51,5 @@ void SetProgramInvocationName(absl::string_view prog_name_str) {
 }
 
 }  // namespace flags_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/flags/internal/program_name.h b/absl/flags/internal/program_name.h
index 326f24bb6533..317a7c5c9169 100644
--- a/absl/flags/internal/program_name.h
+++ b/absl/flags/internal/program_name.h
@@ -24,6 +24,7 @@
 // Program name
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace flags_internal {
 
 // Returns program invocation name or "UNKNOWN" if `SetProgramInvocationName()`
@@ -42,6 +43,7 @@ std::string ShortProgramInvocationName();
 void SetProgramInvocationName(absl::string_view prog_name_str);
 
 }  // namespace flags_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_FLAGS_INTERNAL_PROGRAM_NAME_H_
diff --git a/absl/flags/internal/registry.cc b/absl/flags/internal/registry.cc
index 52d9f3c716f3..5eae933c3fa3 100644
--- a/absl/flags/internal/registry.cc
+++ b/absl/flags/internal/registry.cc
@@ -30,6 +30,7 @@
 //    set it.
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace flags_internal {
 
 // --------------------------------------------------------------------
@@ -281,7 +282,7 @@ class RetiredFlagObj final : public flags_internal::CommandLineFlag {
         op_(ops) {}
 
  private:
-  void Destroy() const override {
+  void Destroy() override {
     // Values are heap allocated for Retired Flags.
     delete this;
   }
@@ -336,4 +337,5 @@ bool IsRetiredFlag(absl::string_view name, bool* type_is_bool) {
 }
 
 }  // namespace flags_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/flags/internal/registry.h b/absl/flags/internal/registry.h
index 1889f3a076dd..d2145a8acfa0 100644
--- a/absl/flags/internal/registry.h
+++ b/absl/flags/internal/registry.h
@@ -27,6 +27,7 @@
 // Global flags registry API.
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace flags_internal {
 
 CommandLineFlag* FindCommandLineFlag(absl::string_view name);
@@ -115,6 +116,7 @@ class FlagSaver {
 };
 
 }  // namespace flags_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_FLAGS_INTERNAL_REGISTRY_H_
diff --git a/absl/flags/internal/type_erased.cc b/absl/flags/internal/type_erased.cc
index a1650fcf71e4..7910db8fd86e 100644
--- a/absl/flags/internal/type_erased.cc
+++ b/absl/flags/internal/type_erased.cc
@@ -21,6 +21,7 @@
 #include "absl/strings/str_cat.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace flags_internal {
 
 bool GetCommandLineOption(absl::string_view name, std::string* value) {
@@ -79,4 +80,5 @@ bool SpecifiedOnCommandLine(absl::string_view name) {
 }
 
 }  // namespace flags_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/flags/internal/type_erased.h b/absl/flags/internal/type_erased.h
index a955116628ff..6cbd84cd1996 100644
--- a/absl/flags/internal/type_erased.h
+++ b/absl/flags/internal/type_erased.h
@@ -25,6 +25,7 @@
 // Registry interfaces operating on type erased handles.
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace flags_internal {
 
 // If a flag named "name" exists, store its current value in *OUTPUT
@@ -81,6 +82,7 @@ inline bool GetByName(absl::string_view name, T* dst) {
 }
 
 }  // namespace flags_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_FLAGS_INTERNAL_TYPE_ERASED_H_
diff --git a/absl/flags/internal/usage.cc b/absl/flags/internal/usage.cc
index dc12e32f04cb..4602c0196924 100644
--- a/absl/flags/internal/usage.cc
+++ b/absl/flags/internal/usage.cc
@@ -44,6 +44,7 @@ ABSL_FLAG(std::string, helpmatch, "",
           "show help on modules whose name contains the specified substr");
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace flags_internal {
 namespace {
 
@@ -404,4 +405,5 @@ int HandleUsageFlags(std::ostream& out,
 }
 
 }  // namespace flags_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/flags/internal/usage.h b/absl/flags/internal/usage.h
index 76075b0829d9..5e8ca6a1f81f 100644
--- a/absl/flags/internal/usage.h
+++ b/absl/flags/internal/usage.h
@@ -27,6 +27,7 @@
 // Usage reporting interfaces
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace flags_internal {
 
 // The format to report the help messages in.
@@ -64,6 +65,7 @@ int HandleUsageFlags(std::ostream& out,
                      absl::string_view program_usage_message);
 
 }  // namespace flags_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 ABSL_DECLARE_FLAG(bool, help);
diff --git a/absl/flags/marshalling.cc b/absl/flags/marshalling.cc
index f4ebe0e34330..87020a2741c8 100644
--- a/absl/flags/marshalling.cc
+++ b/absl/flags/marshalling.cc
@@ -27,6 +27,7 @@
 #include "absl/strings/str_split.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace flags_internal {
 
 // --------------------------------------------------------------------
@@ -226,4 +227,5 @@ std::string AbslUnparseFlag(absl::LogSeverity v) {
   return absl::UnparseFlag(static_cast<int>(v));
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/flags/marshalling.h b/absl/flags/marshalling.h
index 6d3918043704..b9fca7524026 100644
--- a/absl/flags/marshalling.h
+++ b/absl/flags/marshalling.h
@@ -168,6 +168,7 @@
 #include "absl/strings/string_view.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace flags_internal {
 
 // Overloads of `AbslParseFlag()` and `AbslUnparseFlag()` for fundamental types.
@@ -256,6 +257,7 @@ enum class LogSeverity : int;
 bool AbslParseFlag(absl::string_view, absl::LogSeverity*, std::string*);
 std::string AbslUnparseFlag(absl::LogSeverity);
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_FLAGS_MARSHALLING_H_
diff --git a/absl/flags/parse.cc b/absl/flags/parse.cc
index 16c4d68fc270..5a56a35625df 100644
--- a/absl/flags/parse.cc
+++ b/absl/flags/parse.cc
@@ -38,6 +38,7 @@
 // --------------------------------------------------------------------
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace flags_internal {
 namespace {
 
@@ -52,6 +53,7 @@ ABSL_CONST_INIT bool tryfromenv_needs_processing
 
 }  // namespace
 }  // namespace flags_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 ABSL_FLAG(std::vector<std::string>, flagfile, {},
@@ -109,6 +111,7 @@ ABSL_FLAG(std::vector<std::string>, undefok, {},
           "with that name");
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace flags_internal {
 
 namespace {
@@ -748,4 +751,5 @@ std::vector<char*> ParseCommandLine(int argc, char* argv[]) {
       flags_internal::OnUndefinedFlag::kAbortIfUndefined);
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/flags/parse.h b/absl/flags/parse.h
index dbb751015686..871fc993b616 100644
--- a/absl/flags/parse.h
+++ b/absl/flags/parse.h
@@ -29,6 +29,7 @@
 #include "absl/flags/internal/parse.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // ParseCommandLine()
 //
@@ -53,6 +54,7 @@ namespace absl {
 // help messages and then exits the program.
 std::vector<char*> ParseCommandLine(int argc, char* argv[]);
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_FLAGS_PARSE_H_
diff --git a/absl/flags/usage.cc b/absl/flags/usage.cc
index dff7a3dab39c..60459bc2a476 100644
--- a/absl/flags/usage.cc
+++ b/absl/flags/usage.cc
@@ -20,6 +20,7 @@
 #include "absl/synchronization/mutex.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace flags_internal {
 namespace {
 ABSL_CONST_INIT absl::Mutex usage_message_guard(absl::kConstInit);
@@ -53,4 +54,5 @@ absl::string_view ProgramUsageMessage() {
              : "Warning: SetProgramUsageMessage() never called";
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/flags/usage.h b/absl/flags/usage.h
index 3a12107137ad..299e5c3414f5 100644
--- a/absl/flags/usage.h
+++ b/absl/flags/usage.h
@@ -22,6 +22,7 @@
 // Usage reporting interfaces
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // Sets the "usage" message to be used by help reporting routines.
 // For example:
@@ -35,6 +36,7 @@ void SetProgramUsageMessage(absl::string_view new_usage_message);
 // Returns the usage message set by SetProgramUsageMessage().
 absl::string_view ProgramUsageMessage();
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_FLAGS_USAGE_H_
diff --git a/absl/flags/usage_config.cc b/absl/flags/usage_config.cc
index f97bf300dde7..21a2dd018b4a 100644
--- a/absl/flags/usage_config.cc
+++ b/absl/flags/usage_config.cc
@@ -34,6 +34,7 @@ ABSL_ATTRIBUTE_WEAK void AbslInternalReportFatalUsageError(absl::string_view) {}
 }  // extern "C"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace flags_internal {
 
 namespace {
@@ -149,4 +150,5 @@ void SetFlagsUsageConfig(FlagsUsageConfig usage_config) {
     flags_internal::custom_usage_config = new FlagsUsageConfig(usage_config);
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/flags/usage_config.h b/absl/flags/usage_config.h
index bfd0eedbc4a7..e6428e0a6267 100644
--- a/absl/flags/usage_config.h
+++ b/absl/flags/usage_config.h
@@ -54,6 +54,7 @@
 //     Shows help on modules whose name contains the specified substring
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 namespace flags_internal {
 using FlagKindFilter = std::function<bool (absl::string_view)>;
@@ -118,6 +119,7 @@ FlagsUsageConfig GetUsageConfig();
 void ReportUsageError(absl::string_view msg, bool is_fatal);
 
 }  // namespace flags_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 extern "C" {
diff --git a/absl/functional/function_ref.h b/absl/functional/function_ref.h
index 42d9f16fca6b..370acc55b041 100644
--- a/absl/functional/function_ref.h
+++ b/absl/functional/function_ref.h
@@ -54,6 +54,7 @@
 #include "absl/meta/type_traits.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // FunctionRef
 //
@@ -132,6 +133,7 @@ class FunctionRef<R(Args...)> {
   absl::functional_internal::Invoker<R, Args...> invoker_;
 };
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_FUNCTIONAL_FUNCTION_REF_H_
diff --git a/absl/functional/function_ref_benchmark.cc b/absl/functional/function_ref_benchmark.cc
index f6dfcabf1108..045305bfef30 100644
--- a/absl/functional/function_ref_benchmark.cc
+++ b/absl/functional/function_ref_benchmark.cc
@@ -20,6 +20,7 @@
 #include "absl/base/attributes.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace {
 
 int dummy = 0;
@@ -137,4 +138,5 @@ void BM_NonTrivialArgsFunctionRef(benchmark::State& state) {
 BENCHMARK(BM_NonTrivialArgsFunctionRef);
 
 }  // namespace
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/functional/function_ref_test.cc b/absl/functional/function_ref_test.cc
index 90829db09a4d..3aa59745873d 100644
--- a/absl/functional/function_ref_test.cc
+++ b/absl/functional/function_ref_test.cc
@@ -22,6 +22,7 @@
 #include "absl/memory/memory.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace {
 
 void RunFun(FunctionRef<void()> f) { f(); }
@@ -252,4 +253,5 @@ TEST(FunctionRef, PassByValueTypes) {
 }
 
 }  // namespace
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/functional/internal/function_ref.h b/absl/functional/internal/function_ref.h
index fcb0496c2c06..d1575054eaf7 100644
--- a/absl/functional/internal/function_ref.h
+++ b/absl/functional/internal/function_ref.h
@@ -23,6 +23,7 @@
 #include "absl/meta/type_traits.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace functional_internal {
 
 // Like a void* that can handle function pointers as well. The standard does not
@@ -99,6 +100,7 @@ template <bool C>
 using EnableIf = typename ::std::enable_if<C, int>::type;
 
 }  // namespace functional_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_FUNCTIONAL_INTERNAL_FUNCTION_REF_H_
diff --git a/absl/hash/hash.h b/absl/hash/hash.h
index 297dc9cb22ac..23a65ea8687e 100644
--- a/absl/hash/hash.h
+++ b/absl/hash/hash.h
@@ -73,6 +73,7 @@
 #include "absl/hash/internal/hash.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // -----------------------------------------------------------------------------
 // `absl::Hash`
@@ -317,6 +318,7 @@ class HashState : public hash_internal::HashStateBase<HashState> {
   void (*combine_contiguous_)(void*, const unsigned char*, size_t);
 };
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_HASH_HASH_H_
diff --git a/absl/hash/hash_test.cc b/absl/hash/hash_test.cc
index 42c0c3d8bf7e..7a9d57f72b77 100644
--- a/absl/hash/hash_test.cc
+++ b/absl/hash/hash_test.cc
@@ -681,6 +681,7 @@ H AbslHashValue(H state, CustomHashType<Tags...> t) {
 }  // namespace
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace hash_internal {
 template <InvokeTag... Tags>
 struct is_uniquely_represented<
@@ -688,6 +689,7 @@ struct is_uniquely_represented<
     typename EnableIfContained<InvokeTag::kUniquelyRepresented, Tags...>::type>
     : std::true_type {};
 }  // namespace hash_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #if ABSL_HASH_INTERNAL_SUPPORT_LEGACY_HASH_
diff --git a/absl/hash/hash_testing.h b/absl/hash/hash_testing.h
index c45bc154982b..1e1c5741491e 100644
--- a/absl/hash/hash_testing.h
+++ b/absl/hash/hash_testing.h
@@ -28,6 +28,7 @@
 #include "absl/types/variant.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // Run the absl::Hash algorithm over all the elements passed in and verify that
 // their hash expansion is congruent with their `==` operator.
@@ -371,6 +372,7 @@ VerifyTypeImplementsAbslHashCorrectly(std::initializer_list<T> values,
       equals);
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_HASH_HASH_TESTING_H_
diff --git a/absl/hash/internal/city.cc b/absl/hash/internal/city.cc
index dc7650a79e0f..e122c184b60f 100644
--- a/absl/hash/internal/city.cc
+++ b/absl/hash/internal/city.cc
@@ -30,6 +30,7 @@
 #include "absl/base/optimization.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace hash_internal {
 
 #ifdef ABSL_IS_BIG_ENDIAN
@@ -341,4 +342,5 @@ uint64_t CityHash64WithSeeds(const char *s, size_t len, uint64_t seed0,
 }
 
 }  // namespace hash_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/hash/internal/city.h b/absl/hash/internal/city.h
index b43d3407dcb4..161c7748ec89 100644
--- a/absl/hash/internal/city.h
+++ b/absl/hash/internal/city.h
@@ -47,9 +47,13 @@
 
 #include <stdint.h>
 #include <stdlib.h>  // for size_t.
+
 #include <utility>
 
+#include "absl/base/config.h"
+
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace hash_internal {
 
 typedef std::pair<uint64_t, uint64_t> uint128;
@@ -86,6 +90,7 @@ inline uint64_t Hash128to64(const uint128 &x) {
 }
 
 }  // namespace hash_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_HASH_INTERNAL_CITY_H_
diff --git a/absl/hash/internal/city_test.cc b/absl/hash/internal/city_test.cc
index 71b4eccecff9..251d381d73e1 100644
--- a/absl/hash/internal/city_test.cc
+++ b/absl/hash/internal/city_test.cc
@@ -20,6 +20,7 @@
 #include "gtest/gtest.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace hash_internal {
 
 static const uint64_t k0 = 0xc3a5c85c97cb3127ULL;
@@ -590,4 +591,5 @@ TEST(CityHashTest, Unchanging) {
 }
 
 }  // namespace hash_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/hash/internal/hash.cc b/absl/hash/internal/hash.cc
index c17f3be1719a..b44ecb3a6b66 100644
--- a/absl/hash/internal/hash.cc
+++ b/absl/hash/internal/hash.cc
@@ -15,6 +15,7 @@
 #include "absl/hash/internal/hash.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace hash_internal {
 
 uint64_t CityHashState::CombineLargeContiguousImpl32(uint64_t state,
@@ -50,4 +51,5 @@ uint64_t CityHashState::CombineLargeContiguousImpl64(uint64_t state,
 ABSL_CONST_INIT const void* const CityHashState::kSeed = &kSeed;
 
 }  // namespace hash_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/hash/internal/hash.h b/absl/hash/internal/hash.h
index 7d44f57dc90d..2564978a828b 100644
--- a/absl/hash/internal/hash.h
+++ b/absl/hash/internal/hash.h
@@ -50,6 +50,7 @@
 #include "absl/hash/internal/city.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace hash_internal {
 
 class PiecewiseCombiner;
@@ -980,6 +981,7 @@ H PiecewiseCombiner::finalize(H state) {
 }
 
 }  // namespace hash_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_HASH_INTERNAL_HASH_H_
diff --git a/absl/hash/internal/spy_hash_state.h b/absl/hash/internal/spy_hash_state.h
index 05c7cafeb0ee..c08312081180 100644
--- a/absl/hash/internal/spy_hash_state.h
+++ b/absl/hash/internal/spy_hash_state.h
@@ -25,6 +25,7 @@
 #include "absl/strings/str_join.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace hash_internal {
 
 // SpyHashState is an implementation of the HashState API that simply
@@ -224,6 +225,7 @@ void AbslHashValue(SpyHashStateImpl<T>, const U&);
 using SpyHashState = SpyHashStateImpl<void>;
 
 }  // namespace hash_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_HASH_INTERNAL_SPY_HASH_STATE_H_
diff --git a/absl/memory/memory.h b/absl/memory/memory.h
index 243a5dda6eeb..513f7103a00c 100644
--- a/absl/memory/memory.h
+++ b/absl/memory/memory.h
@@ -34,6 +34,7 @@
 #include "absl/meta/type_traits.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // -----------------------------------------------------------------------------
 // Function Template: WrapUnique()
@@ -688,6 +689,7 @@ void CopyRange(Allocator& alloc, Iterator destination, InputIterator first,
   }
 }
 }  // namespace memory_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_MEMORY_MEMORY_H_
diff --git a/absl/memory/memory_exception_safety_test.cc b/absl/memory/memory_exception_safety_test.cc
index 729507e97f33..c0910dc759f1 100644
--- a/absl/memory/memory_exception_safety_test.cc
+++ b/absl/memory/memory_exception_safety_test.cc
@@ -22,6 +22,7 @@
 #include "absl/base/internal/exception_safety_testing.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace {
 
 constexpr int kLength = 50;
@@ -53,6 +54,7 @@ TEST(MakeUnique, CheckForLeaks) {
 }
 
 }  // namespace
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_HAVE_EXCEPTIONS
diff --git a/absl/meta/type_traits.h b/absl/meta/type_traits.h
index 8cd5f043e0b7..ba87d2f0edfa 100644
--- a/absl/meta/type_traits.h
+++ b/absl/meta/type_traits.h
@@ -48,6 +48,7 @@
 #endif
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // Defined and documented later on in this file.
 template <typename T>
@@ -752,6 +753,7 @@ using swap_internal::Swap;
 using swap_internal::StdSwapIsUnconstrained;
 
 }  // namespace type_traits_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_META_TYPE_TRAITS_H_
diff --git a/absl/numeric/int128.cc b/absl/numeric/int128.cc
index 1eba09de38c8..a20a77e7eb0d 100644
--- a/absl/numeric/int128.cc
+++ b/absl/numeric/int128.cc
@@ -23,6 +23,7 @@
 #include <type_traits>
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 const uint128 kuint128max = MakeUint128(std::numeric_limits<uint64_t>::max(),
                                         std::numeric_limits<uint64_t>::max());
@@ -349,6 +350,7 @@ std::ostream& operator<<(std::ostream& os, int128 v) {
   return os << rep;
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 namespace std {
diff --git a/absl/numeric/int128.h b/absl/numeric/int128.h
index 506176127fe6..718f70b19782 100644
--- a/absl/numeric/int128.h
+++ b/absl/numeric/int128.h
@@ -49,6 +49,7 @@
 #endif  // defined(_MSC_VER)
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 class int128;
 
@@ -245,6 +246,7 @@ constexpr uint128 Uint128Max() {
                  (std::numeric_limits<uint64_t>::max)());
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 // Specialized numeric_limits for uint128.
@@ -293,6 +295,7 @@ class numeric_limits<absl::uint128> {
 }  // namespace std
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // int128
 //
@@ -478,6 +481,7 @@ constexpr int128 Int128Min() {
   return int128((std::numeric_limits<int64_t>::min)(), 0);
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 // Specialized numeric_limits for int128.
@@ -529,6 +533,7 @@ class numeric_limits<absl::int128> {
 //                      Implementation details follow
 // --------------------------------------------------------------------------
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 constexpr uint128 MakeUint128(uint64_t high, uint64_t low) {
   return uint128(high, low);
@@ -1078,6 +1083,7 @@ constexpr int64_t BitCastToSigned(uint64_t v) {
 #include "absl/numeric/int128_no_intrinsic.inc"  // IWYU pragma: export
 #endif  // ABSL_HAVE_INTRINSIC_INT128
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #undef ABSL_INTERNAL_WCHAR_T
diff --git a/absl/random/CMakeLists.txt b/absl/random/CMakeLists.txt
index 13e96357ffdd..46dbc3efbc83 100644
--- a/absl/random/CMakeLists.txt
+++ b/absl/random/CMakeLists.txt
@@ -526,6 +526,8 @@ absl_cc_library(
     ${ABSL_DEFAULT_COPTS}
   LINKOPTS
     ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::config
 )
 
 # Internal-only target, do not depend on directly.
@@ -559,6 +561,8 @@ absl_cc_library(
     ${ABSL_DEFAULT_COPTS}
   LINKOPTS
     ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::config
 )
 
 # Internal-only target, do not depend on directly.
@@ -618,6 +622,8 @@ absl_cc_library(
     ${ABSL_DEFAULT_COPTS}
   LINKOPTS
     ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::config
   TESTONLY
 )
 
@@ -631,6 +637,8 @@ absl_cc_library(
     ${ABSL_DEFAULT_COPTS}
   LINKOPTS
     ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::config
   TESTONLY
 )
 
@@ -782,6 +790,8 @@ absl_cc_library(
     ${ABSL_DEFAULT_COPTS}
   LINKOPTS
     ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::config
 )
 
 # Internal-only target, do not depend on directly.
@@ -816,6 +826,7 @@ absl_cc_library(
     ${ABSL_DEFAULT_LINKOPTS}
   DEPS
     absl::random_internal_platform
+    absl::config
 )
 
 # Internal-only target, do not depend on directly.
@@ -835,6 +846,7 @@ absl_cc_library(
   DEPS
     absl::random_internal_platform
     absl::random_internal_randen_hwaes_impl
+    absl::config
 )
 
 # Internal-only target, do not depend on directly.
@@ -851,6 +863,7 @@ absl_cc_library(
     ${ABSL_DEFAULT_LINKOPTS}
   DEPS
     absl::random_internal_platform
+    absl::config
 )
 
 # Internal-only target, do not depend on directly.
@@ -868,6 +881,7 @@ absl_cc_library(
   LINKOPTS
     ${ABSL_DEFAULT_LINKOPTS}
   DEPS
+    absl::config
     absl::core_headers
     absl::raw_logging_internal
     absl::strings
diff --git a/absl/random/bernoulli_distribution.h b/absl/random/bernoulli_distribution.h
index 326fcb6e012d..25bd0d5ca420 100644
--- a/absl/random/bernoulli_distribution.h
+++ b/absl/random/bernoulli_distribution.h
@@ -24,6 +24,7 @@
 #include "absl/random/internal/iostream_state_saver.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // absl::bernoulli_distribution is a drop in replacement for
 // std::bernoulli_distribution. It guarantees that (given a perfect
@@ -193,6 +194,7 @@ bool bernoulli_distribution::Generate(double p,
   }
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_RANDOM_BERNOULLI_DISTRIBUTION_H_
diff --git a/absl/random/beta_distribution.h b/absl/random/beta_distribution.h
index b09b02f0dde5..c154066fb813 100644
--- a/absl/random/beta_distribution.h
+++ b/absl/random/beta_distribution.h
@@ -29,6 +29,7 @@
 #include "absl/random/internal/iostream_state_saver.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // absl::beta_distribution:
 // Generate a floating-point variate conforming to a Beta distribution:
@@ -420,6 +421,7 @@ std::basic_istream<CharT, Traits>& operator>>(
   return is;
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_RANDOM_BETA_DISTRIBUTION_H_
diff --git a/absl/random/bit_gen_ref.h b/absl/random/bit_gen_ref.h
index 00e904f85ec3..e8771162e5fb 100644
--- a/absl/random/bit_gen_ref.h
+++ b/absl/random/bit_gen_ref.h
@@ -31,6 +31,7 @@
 #include "absl/random/internal/mocking_bit_gen_base.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace random_internal {
 
 template <typename URBG, typename = void, typename = void, typename = void>
@@ -146,6 +147,7 @@ struct DistributionCaller<absl::BitGenRef> {
 };
 
 }  // namespace random_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_RANDOM_BIT_GEN_REF_H_
diff --git a/absl/random/bit_gen_ref_test.cc b/absl/random/bit_gen_ref_test.cc
index bc02ca5c1621..ca0e4d707250 100644
--- a/absl/random/bit_gen_ref_test.cc
+++ b/absl/random/bit_gen_ref_test.cc
@@ -21,6 +21,7 @@
 #include "absl/random/random.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 class ConstBitGen : public absl::random_internal::MockingBitGenBase {
   bool CallImpl(const std::type_info&, void*, void* result) override {
@@ -96,4 +97,5 @@ TEST(BitGenRefTest, MockingBitGenBaseOverrides) {
   EXPECT_EQ(FnTest(gen_ref), 42);  // Copy
 }
 }  // namespace
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/random/discrete_distribution.cc b/absl/random/discrete_distribution.cc
index e6c09c5180b3..081accee52a4 100644
--- a/absl/random/discrete_distribution.cc
+++ b/absl/random/discrete_distribution.cc
@@ -15,6 +15,7 @@
 #include "absl/random/discrete_distribution.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace random_internal {
 
 // Initializes the distribution table for Walker's Aliasing algorithm, described
@@ -93,4 +94,5 @@ std::vector<std::pair<double, size_t>> InitDiscreteDistribution(
 }
 
 }  // namespace random_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/random/discrete_distribution.h b/absl/random/discrete_distribution.h
index 1560f03c5fdd..171aa11a1eb4 100644
--- a/absl/random/discrete_distribution.h
+++ b/absl/random/discrete_distribution.h
@@ -29,6 +29,7 @@
 #include "absl/random/uniform_int_distribution.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // absl::discrete_distribution
 //
@@ -240,6 +241,7 @@ std::basic_istream<CharT, Traits>& operator>>(
   return is;
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_RANDOM_DISCRETE_DISTRIBUTION_H_
diff --git a/absl/random/distribution_format_traits.h b/absl/random/distribution_format_traits.h
index f9f070589f00..22b358cc8c37 100644
--- a/absl/random/distribution_format_traits.h
+++ b/absl/random/distribution_format_traits.h
@@ -36,6 +36,7 @@
 #include "absl/types/span.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 struct IntervalClosedClosedTag;
 struct IntervalClosedOpenTag;
@@ -271,6 +272,7 @@ struct DistributionFormatTraits<UniformDistributionWrapper<NumType>> {
 };
 
 }  // namespace random_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_RANDOM_DISTRIBUTION_FORMAT_TRAITS_H_
diff --git a/absl/random/distributions.h b/absl/random/distributions.h
index 6ced60616158..c1fb66501593 100644
--- a/absl/random/distributions.h
+++ b/absl/random/distributions.h
@@ -67,6 +67,7 @@
 #include "absl/random/zipf_distribution.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 ABSL_INTERNAL_INLINE_CONSTEXPR(IntervalClosedClosedTag, IntervalClosedClosed,
                                {});
@@ -458,6 +459,7 @@ IntType Zipf(URBG&& urbg,  // NOLINT(runtime/references)
       distribution_t, format_t>(&urbg, hi, q, v);
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_RANDOM_DISTRIBUTIONS_H_
diff --git a/absl/random/exponential_distribution.h b/absl/random/exponential_distribution.h
index 24abf57e99d6..b5caf8a1e1f3 100644
--- a/absl/random/exponential_distribution.h
+++ b/absl/random/exponential_distribution.h
@@ -27,6 +27,7 @@
 #include "absl/random/internal/iostream_state_saver.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // absl::exponential_distribution:
 // Generates a number conforming to an exponential distribution and is
@@ -158,6 +159,7 @@ std::basic_istream<CharT, Traits>& operator>>(
   return is;
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_RANDOM_EXPONENTIAL_DISTRIBUTION_H_
diff --git a/absl/random/gaussian_distribution.cc b/absl/random/gaussian_distribution.cc
index 5dd846194141..c7a72cb2f61c 100644
--- a/absl/random/gaussian_distribution.cc
+++ b/absl/random/gaussian_distribution.cc
@@ -4,6 +4,7 @@
 #include "absl/random/gaussian_distribution.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace random_internal {
 
 const gaussian_distribution_base::Tables
@@ -96,6 +97,7 @@ const gaussian_distribution_base::Tables
      0.9362826816850632339, 0.9635996931270905952, 1}};
 
 }  // namespace random_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 // clang-format on
diff --git a/absl/random/gaussian_distribution.h b/absl/random/gaussian_distribution.h
index c299e9441c46..c1427b06d549 100644
--- a/absl/random/gaussian_distribution.h
+++ b/absl/random/gaussian_distribution.h
@@ -33,6 +33,7 @@
 #include "absl/random/internal/iostream_state_saver.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace random_internal {
 
 // absl::gaussian_distribution_base implements the underlying ziggurat algorithm
@@ -267,6 +268,7 @@ inline double gaussian_distribution_base::zignor(
 }
 
 }  // namespace random_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_RANDOM_GAUSSIAN_DISTRIBUTION_H_
diff --git a/absl/random/internal/BUILD.bazel b/absl/random/internal/BUILD.bazel
index 952929ea264d..d7ad4efec989 100644
--- a/absl/random/internal/BUILD.bazel
+++ b/absl/random/internal/BUILD.bazel
@@ -51,6 +51,7 @@ cc_library(
     visibility = [
         "//absl/random:__pkg__",
     ],
+    deps = ["//absl/base:config"],
 )
 
 cc_library(
@@ -78,6 +79,7 @@ cc_library(
     visibility = [
         "//absl/random:__pkg__",
     ],
+    deps = ["//absl/base:config"],
 )
 
 cc_library(
@@ -138,6 +140,7 @@ cc_library(
     ],
     copts = ABSL_DEFAULT_COPTS,
     linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = ["//absl/base:config"],
 )
 
 cc_library(
@@ -148,6 +151,7 @@ cc_library(
     ],
     copts = ABSL_DEFAULT_COPTS,
     linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = ["//absl/base:config"],
 )
 
 cc_library(
@@ -269,6 +273,7 @@ cc_library(
         "randen-keys.inc",
         "platform.h",
     ],
+    deps = ["//absl/base:config"],
 )
 
 cc_library(
@@ -297,6 +302,7 @@ cc_library(
     linkopts = ABSL_DEFAULT_LINKOPTS,
     deps = [
         ":platform",
+        "//absl/base:config",
         "//absl/base:core_headers",
     ],
 )
@@ -317,6 +323,7 @@ cc_library(
     deps = [
         ":platform",
         ":randen_hwaes_impl",
+        "//absl/base:config",
     ],
 )
 
@@ -338,6 +345,7 @@ cc_library(
     linkopts = ABSL_DEFAULT_LINKOPTS,
     deps = [
         ":platform",
+        "//absl/base:config",
         "//absl/base:core_headers",
     ],
 )
@@ -368,6 +376,7 @@ cc_library(
     copts = ABSL_DEFAULT_COPTS,
     linkopts = ABSL_DEFAULT_LINKOPTS,
     deps = [
+        "//absl/base:config",
         "//absl/base:core_headers",
         "//absl/base:raw_logging_internal",
         "//absl/strings",
diff --git a/absl/random/internal/chi_square.cc b/absl/random/internal/chi_square.cc
index c0acc9477883..640d48cea6f4 100644
--- a/absl/random/internal/chi_square.cc
+++ b/absl/random/internal/chi_square.cc
@@ -19,6 +19,7 @@
 #include "absl/random/internal/distribution_test_util.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace random_internal {
 namespace {
 
@@ -227,4 +228,5 @@ double ChiSquarePValue(double chi_square, int dof) {
 }
 
 }  // namespace random_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/random/internal/chi_square.h b/absl/random/internal/chi_square.h
index fa8646f274cd..07f4fbe52298 100644
--- a/absl/random/internal/chi_square.h
+++ b/absl/random/internal/chi_square.h
@@ -26,7 +26,10 @@
 
 #include <cassert>
 
+#include "absl/base/config.h"
+
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace random_internal {
 
 constexpr const char kChiSquared[] = "chi-squared";
@@ -80,6 +83,7 @@ double ChiSquareValue(int dof, double p);
 double ChiSquarePValue(double chi_square, int dof);
 
 }  // namespace random_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_RANDOM_INTERNAL_CHI_SQUARE_H_
diff --git a/absl/random/internal/distribution_caller.h b/absl/random/internal/distribution_caller.h
index 0318e1f8072e..02603cf84355 100644
--- a/absl/random/internal/distribution_caller.h
+++ b/absl/random/internal/distribution_caller.h
@@ -19,7 +19,10 @@
 
 #include <utility>
 
+#include "absl/base/config.h"
+
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace random_internal {
 
 // DistributionCaller provides an opportunity to overload the general
@@ -51,6 +54,7 @@ struct DistributionCaller {
 };
 
 }  // namespace random_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_RANDOM_INTERNAL_DISTRIBUTION_CALLER_H_
diff --git a/absl/random/internal/distribution_test_util.cc b/absl/random/internal/distribution_test_util.cc
index 85c8d596ebf8..e9005658c0a7 100644
--- a/absl/random/internal/distribution_test_util.cc
+++ b/absl/random/internal/distribution_test_util.cc
@@ -25,6 +25,7 @@
 #include "absl/strings/str_format.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace random_internal {
 namespace {
 
@@ -413,4 +414,5 @@ double MaxErrorTolerance(double acceptance_probability) {
 }
 
 }  // namespace random_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/random/internal/distribution_test_util.h b/absl/random/internal/distribution_test_util.h
index b5ba49fa7e1e..6d94cf6c97bf 100644
--- a/absl/random/internal/distribution_test_util.h
+++ b/absl/random/internal/distribution_test_util.h
@@ -26,6 +26,7 @@
 // non-test code.
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace random_internal {
 
 // http://webspace.ship.edu/pgmarr/Geo441/Lectures/Lec%205%20-%20Normality%20Testing.pdf
@@ -106,6 +107,7 @@ double BetaIncomplete(double x, double p, double q);
 double BetaIncompleteInv(double p, double q, double alpha);
 
 }  // namespace random_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_RANDOM_INTERNAL_DISTRIBUTION_TEST_UTIL_H_
diff --git a/absl/random/internal/distributions.h b/absl/random/internal/distributions.h
index c8cec02b7fbc..d7e3c0161f06 100644
--- a/absl/random/internal/distributions.h
+++ b/absl/random/internal/distributions.h
@@ -23,6 +23,7 @@
 #include "absl/random/internal/uniform_helper.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace random_internal {
 
 // In the absence of an explicitly provided return-type, the template
@@ -45,6 +46,7 @@ using uniform_inferred_return_t =
                           is_widening_convertible<A, B>::value, B, A>::type>;
 
 }  // namespace random_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_RANDOM_INTERNAL_DISTRIBUTIONS_H_
diff --git a/absl/random/internal/explicit_seed_seq.h b/absl/random/internal/explicit_seed_seq.h
index b660ece50017..6a743eaf46cc 100644
--- a/absl/random/internal/explicit_seed_seq.h
+++ b/absl/random/internal/explicit_seed_seq.h
@@ -22,7 +22,10 @@
 #include <iterator>
 #include <vector>
 
+#include "absl/base/config.h"
+
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace random_internal {
 
 // This class conforms to the C++ Standard "Seed Sequence" concept
@@ -82,6 +85,7 @@ class ExplicitSeedSeq {
 };
 
 }  // namespace random_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_RANDOM_INTERNAL_EXPLICIT_SEED_SEQ_H_
diff --git a/absl/random/internal/fast_uniform_bits.h b/absl/random/internal/fast_uniform_bits.h
index e8df92f3d99f..f13c8729f7c8 100644
--- a/absl/random/internal/fast_uniform_bits.h
+++ b/absl/random/internal/fast_uniform_bits.h
@@ -20,7 +20,10 @@
 #include <limits>
 #include <type_traits>
 
+#include "absl/base/config.h"
+
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace random_internal {
 // Returns true if the input value is zero or a power of two. Useful for
 // determining if the range of output values in a URBG
@@ -255,6 +258,7 @@ FastUniformBits<UIntType>::Generate(URBG& g,  // NOLINT(runtime/references)
 }
 
 }  // namespace random_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_RANDOM_INTERNAL_FAST_UNIFORM_BITS_H_
diff --git a/absl/random/internal/fast_uniform_bits_test.cc b/absl/random/internal/fast_uniform_bits_test.cc
index 9f2e82687dd6..f5b837e5861b 100644
--- a/absl/random/internal/fast_uniform_bits_test.cc
+++ b/absl/random/internal/fast_uniform_bits_test.cc
@@ -19,6 +19,7 @@
 #include "gtest/gtest.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace random_internal {
 namespace {
 
@@ -269,4 +270,5 @@ TEST(FastUniformBitsTest, URBG32bitRegression) {
 
 }  // namespace
 }  // namespace random_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/random/internal/fastmath.h b/absl/random/internal/fastmath.h
index 4bd184105399..6baeb5a7c917 100644
--- a/absl/random/internal/fastmath.h
+++ b/absl/random/internal/fastmath.h
@@ -25,6 +25,7 @@
 #include "absl/base/internal/bits.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace random_internal {
 
 // Returns the position of the first bit set.
@@ -67,6 +68,7 @@ inline constexpr uint64_t rotr(uint64_t value, uint8_t bits) {
 }
 
 }  // namespace random_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_RANDOM_INTERNAL_FASTMATH_H_
diff --git a/absl/random/internal/gaussian_distribution_gentables.cc b/absl/random/internal/gaussian_distribution_gentables.cc
index 16a23cb2f91f..a2bf03940f67 100644
--- a/absl/random/internal/gaussian_distribution_gentables.cc
+++ b/absl/random/internal/gaussian_distribution_gentables.cc
@@ -27,6 +27,7 @@
 #include "absl/base/macros.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace random_internal {
 namespace {
 
@@ -135,6 +136,7 @@ void TableGenerator::Print(std::ostream* os) {
 }
 
 }  // namespace random_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 int main(int, char**) {
diff --git a/absl/random/internal/generate_real.h b/absl/random/internal/generate_real.h
index 246d863e56e4..20f6d20807d5 100644
--- a/absl/random/internal/generate_real.h
+++ b/absl/random/internal/generate_real.h
@@ -29,6 +29,7 @@
 #include "absl/random/internal/traits.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace random_internal {
 
 // Tristate tag types controlling the output of GenerateRealFromBits.
@@ -139,6 +140,7 @@ inline RealType GenerateRealFromBits(uint64_t bits, int exp_bias = 0) {
 }
 
 }  // namespace random_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_RANDOM_INTERNAL_GENERATE_REAL_H_
diff --git a/absl/random/internal/iostream_state_saver.h b/absl/random/internal/iostream_state_saver.h
index df88fa76bcde..7378829a423c 100644
--- a/absl/random/internal/iostream_state_saver.h
+++ b/absl/random/internal/iostream_state_saver.h
@@ -24,6 +24,7 @@
 #include "absl/numeric/int128.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace random_internal {
 
 // The null_state_saver does nothing.
@@ -238,6 +239,7 @@ inline FloatType read_floating_point(IStream& is) {
 }
 
 }  // namespace random_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_RANDOM_INTERNAL_IOSTREAM_STATE_SAVER_H_
diff --git a/absl/random/internal/mock_overload_set.h b/absl/random/internal/mock_overload_set.h
index 539313d73c95..c2a30d89d52b 100644
--- a/absl/random/internal/mock_overload_set.h
+++ b/absl/random/internal/mock_overload_set.h
@@ -23,6 +23,7 @@
 #include "absl/random/mocking_bit_gen.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace random_internal {
 
 template <typename DistrT, typename Fn>
@@ -85,5 +86,6 @@ struct MockOverloadSet<DistrT, FirstSig, Rest...>
 };
 
 }  // namespace random_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 #endif  // ABSL_RANDOM_INTERNAL_MOCK_OVERLOAD_SET_H_
diff --git a/absl/random/internal/mocking_bit_gen_base.h b/absl/random/internal/mocking_bit_gen_base.h
index aff2ba6df3e7..eeeae9d295b2 100644
--- a/absl/random/internal/mocking_bit_gen_base.h
+++ b/absl/random/internal/mocking_bit_gen_base.h
@@ -25,6 +25,7 @@
 #include "absl/strings/str_cat.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace random_internal {
 
 // MockingBitGenExpectationFormatter is invoked to format unsatisfied mocks
@@ -113,6 +114,7 @@ class MockingBitGenBase {
 };  // namespace random_internal
 
 }  // namespace random_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_RANDOM_INTERNAL_MOCKING_BIT_GEN_BASE_H_
diff --git a/absl/random/internal/nanobenchmark.cc b/absl/random/internal/nanobenchmark.cc
index feb81c859585..8fee77fcc776 100644
--- a/absl/random/internal/nanobenchmark.cc
+++ b/absl/random/internal/nanobenchmark.cc
@@ -70,6 +70,7 @@
 #endif
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace random_internal_nanobenchmark {
 namespace {
 
@@ -799,4 +800,5 @@ size_t Measure(const Func func, const void* arg, const FuncInput* inputs,
 }
 
 }  // namespace random_internal_nanobenchmark
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/random/internal/nanobenchmark.h b/absl/random/internal/nanobenchmark.h
index c2b650d191b7..a5097ba27b0f 100644
--- a/absl/random/internal/nanobenchmark.h
+++ b/absl/random/internal/nanobenchmark.h
@@ -50,7 +50,10 @@
 #include <stddef.h>
 #include <stdint.h>
 
+#include "absl/base/config.h"
+
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace random_internal_nanobenchmark {
 
 // Input influencing the function being measured (e.g. number of bytes to copy).
@@ -163,6 +166,7 @@ static inline size_t MeasureClosure(const Closure& closure,
 }
 
 }  // namespace random_internal_nanobenchmark
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_RANDOM_INTERNAL_NANOBENCHMARK_H_
diff --git a/absl/random/internal/nanobenchmark_test.cc b/absl/random/internal/nanobenchmark_test.cc
index 383345a8b474..ab824ef55fd9 100644
--- a/absl/random/internal/nanobenchmark_test.cc
+++ b/absl/random/internal/nanobenchmark_test.cc
@@ -18,6 +18,7 @@
 #include "absl/strings/numbers.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace random_internal_nanobenchmark {
 namespace {
 
@@ -67,6 +68,7 @@ void RunAll(const int argc, char* argv[]) {
 
 }  // namespace
 }  // namespace random_internal_nanobenchmark
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 int main(int argc, char* argv[]) {
diff --git a/absl/random/internal/nonsecure_base.h b/absl/random/internal/nonsecure_base.h
index 8847e74bef6b..730fa2ea12d2 100644
--- a/absl/random/internal/nonsecure_base.h
+++ b/absl/random/internal/nonsecure_base.h
@@ -33,6 +33,7 @@
 #include "absl/types/span.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace random_internal {
 
 // Each instance of NonsecureURBGBase<URBG> will be seeded by variates produced
@@ -143,6 +144,7 @@ class NonsecureURBGBase {
 };
 
 }  // namespace random_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_RANDOM_INTERNAL_NONSECURE_BASE_H_
diff --git a/absl/random/internal/pcg_engine.h b/absl/random/internal/pcg_engine.h
index b5df4eafffa4..53c23fe1b492 100644
--- a/absl/random/internal/pcg_engine.h
+++ b/absl/random/internal/pcg_engine.h
@@ -24,6 +24,7 @@
 #include "absl/random/internal/iostream_state_saver.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace random_internal {
 
 // pcg_engine is a simplified implementation of Melissa O'Neil's PCG engine in
@@ -300,6 +301,7 @@ using pcg32_2018_engine = pcg_engine<
     random_internal::pcg_xsh_rr_64_32>;
 
 }  // namespace random_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_RANDOM_INTERNAL_PCG_ENGINE_H_
diff --git a/absl/random/internal/pool_urbg.cc b/absl/random/internal/pool_urbg.cc
index f2e1c1f6fe26..5bee530770eb 100644
--- a/absl/random/internal/pool_urbg.cc
+++ b/absl/random/internal/pool_urbg.cc
@@ -37,6 +37,7 @@ using absl::base_internal::SpinLock;
 using absl::base_internal::SpinLockHolder;
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace random_internal {
 namespace {
 
@@ -249,4 +250,5 @@ template class RandenPool<uint32_t>;
 template class RandenPool<uint64_t>;
 
 }  // namespace random_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/random/internal/pool_urbg.h b/absl/random/internal/pool_urbg.h
index 9b2dd4bfceeb..05721929f54e 100644
--- a/absl/random/internal/pool_urbg.h
+++ b/absl/random/internal/pool_urbg.h
@@ -22,6 +22,7 @@
 #include "absl/types/span.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace random_internal {
 
 // RandenPool is a thread-safe random number generator [random.req.urbg] that
@@ -124,6 +125,7 @@ class PoolURBG {
 };
 
 }  // namespace random_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_RANDOM_INTERNAL_POOL_URBG_H_
diff --git a/absl/random/internal/randen.cc b/absl/random/internal/randen.cc
index bab8075a54f8..78a1e00c0832 100644
--- a/absl/random/internal/randen.cc
+++ b/absl/random/internal/randen.cc
@@ -41,6 +41,7 @@
 // structured/low-entropy counters to digits of Pi.
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace random_internal {
 namespace {
 
@@ -86,4 +87,5 @@ Randen::Randen() {
 }
 
 }  // namespace random_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/random/internal/randen.h b/absl/random/internal/randen.h
index a4ff25459688..c2834aaf3d2c 100644
--- a/absl/random/internal/randen.h
+++ b/absl/random/internal/randen.h
@@ -23,6 +23,7 @@
 #include "absl/random/internal/randen_traits.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace random_internal {
 
 // RANDen = RANDom generator or beetroots in Swiss German.
@@ -95,6 +96,7 @@ class Randen {
 };
 
 }  // namespace random_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_RANDOM_INTERNAL_RANDEN_H_
diff --git a/absl/random/internal/randen_detect.cc b/absl/random/internal/randen_detect.cc
index d5946b219cc2..d63230c25583 100644
--- a/absl/random/internal/randen_detect.cc
+++ b/absl/random/internal/randen_detect.cc
@@ -95,6 +95,7 @@ static uint32_t GetAuxval(uint32_t hwcap_type) {
 #endif
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace random_internal {
 
 // The default return at the end of the function might be unreachable depending
@@ -216,4 +217,5 @@ bool CPUSupportsRandenHwAes() {
 #endif
 
 }  // namespace random_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/random/internal/randen_detect.h b/absl/random/internal/randen_detect.h
index 44c5c6672391..f283f4322647 100644
--- a/absl/random/internal/randen_detect.h
+++ b/absl/random/internal/randen_detect.h
@@ -15,7 +15,10 @@
 #ifndef ABSL_RANDOM_INTERNAL_RANDEN_DETECT_H_
 #define ABSL_RANDOM_INTERNAL_RANDEN_DETECT_H_
 
+#include "absl/base/config.h"
+
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace random_internal {
 
 // Returns whether the current CPU supports RandenHwAes implementation.
@@ -24,6 +27,7 @@ namespace random_internal {
 bool CPUSupportsRandenHwAes();
 
 }  // namespace random_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_RANDOM_INTERNAL_RANDEN_DETECT_H_
diff --git a/absl/random/internal/randen_engine.h b/absl/random/internal/randen_engine.h
index 02212a137c36..6b33731336e7 100644
--- a/absl/random/internal/randen_engine.h
+++ b/absl/random/internal/randen_engine.h
@@ -28,6 +28,7 @@
 #include "absl/random/internal/randen.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace random_internal {
 
 // Deterministic pseudorandom byte generator with backtracking resistance
@@ -223,6 +224,7 @@ class alignas(16) randen_engine {
 };
 
 }  // namespace random_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_RANDOM_INTERNAL_RANDEN_ENGINE_H_
diff --git a/absl/random/internal/randen_hwaes.cc b/absl/random/internal/randen_hwaes.cc
index 6cc36fd39b5e..e23844f12e56 100644
--- a/absl/random/internal/randen_hwaes.cc
+++ b/absl/random/internal/randen_hwaes.cc
@@ -75,6 +75,7 @@
 #include <cstdlib>
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace random_internal {
 
 // No accelerated implementation.
@@ -106,6 +107,7 @@ void RandenHwAes::Generate(const void*, void*) {
 }
 
 }  // namespace random_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #else  // defined(ABSL_RANDEN_HWAES_IMPL)
@@ -518,6 +520,7 @@ inline ABSL_TARGET_CRYPTO void Permute(
 }  // namespace
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace random_internal {
 
 bool HasRandenHwAesImplementation() { return true; }
@@ -629,6 +632,7 @@ void ABSL_TARGET_CRYPTO RandenHwAes::Generate(const void* keys,
 #endif
 
 }  // namespace random_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // (ABSL_RANDEN_HWAES_IMPL)
diff --git a/absl/random/internal/randen_hwaes.h b/absl/random/internal/randen_hwaes.h
index d8e6055f01a9..bce36b522609 100644
--- a/absl/random/internal/randen_hwaes.h
+++ b/absl/random/internal/randen_hwaes.h
@@ -15,12 +15,15 @@
 #ifndef ABSL_RANDOM_INTERNAL_RANDEN_HWAES_H_
 #define ABSL_RANDOM_INTERNAL_RANDEN_HWAES_H_
 
+#include "absl/base/config.h"
+
 // HERMETIC NOTE: The randen_hwaes target must not introduce duplicate
 // symbols from arbitrary system and other headers, since it may be built
 // with different flags from other targets, using different levels of
 // optimization, potentially introducing ODR violations.
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace random_internal {
 
 // RANDen = RANDom generator or beetroots in Swiss German.
@@ -41,6 +44,7 @@ class RandenHwAes {
 bool HasRandenHwAesImplementation();
 
 }  // namespace random_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_RANDOM_INTERNAL_RANDEN_HWAES_H_
diff --git a/absl/random/internal/randen_slow.cc b/absl/random/internal/randen_slow.cc
index e7959c7e0525..8d07458254a5 100644
--- a/absl/random/internal/randen_slow.cc
+++ b/absl/random/internal/randen_slow.cc
@@ -462,6 +462,7 @@ inline ABSL_RANDOM_INTERNAL_ATTRIBUTE_ALWAYS_INLINE void Permute(
 }  // namespace
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace random_internal {
 
 const void* RandenSlow::GetKeys() {
@@ -501,4 +502,5 @@ void RandenSlow::Generate(const void* keys, void* state_void) {
 }
 
 }  // namespace random_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/random/internal/randen_slow.h b/absl/random/internal/randen_slow.h
index 305861308003..72f92b54ad23 100644
--- a/absl/random/internal/randen_slow.h
+++ b/absl/random/internal/randen_slow.h
@@ -17,7 +17,10 @@
 
 #include <cstddef>
 
+#include "absl/base/config.h"
+
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace random_internal {
 
 // RANDen = RANDom generator or beetroots in Swiss German.
@@ -38,6 +41,7 @@ class RandenSlow {
 };
 
 }  // namespace random_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_RANDOM_INTERNAL_RANDEN_SLOW_H_
diff --git a/absl/random/internal/randen_traits.h b/absl/random/internal/randen_traits.h
index 4f1f408d1917..2b8bbe73830e 100644
--- a/absl/random/internal/randen_traits.h
+++ b/absl/random/internal/randen_traits.h
@@ -22,7 +22,10 @@
 
 #include <cstddef>
 
+#include "absl/base/config.h"
+
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace random_internal {
 
 // RANDen = RANDom generator or beetroots in Swiss German.
@@ -54,6 +57,7 @@ struct RandenTraits {
 };
 
 }  // namespace random_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_RANDOM_INTERNAL_RANDEN_TRAITS_H_
diff --git a/absl/random/internal/salted_seed_seq.h b/absl/random/internal/salted_seed_seq.h
index 864870069254..5953a090f80c 100644
--- a/absl/random/internal/salted_seed_seq.h
+++ b/absl/random/internal/salted_seed_seq.h
@@ -30,6 +30,7 @@
 #include "absl/types/span.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace random_internal {
 
 // This class conforms to the C++ Standard "Seed Sequence" concept
@@ -160,6 +161,7 @@ SaltedSeedSeq<typename std::decay<SSeq>::type> MakeSaltedSeedSeq(SSeq&& seq) {
 }
 
 }  // namespace random_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_RANDOM_INTERNAL_SALTED_SEED_SEQ_H_
diff --git a/absl/random/internal/seed_material.cc b/absl/random/internal/seed_material.cc
index ab4dd0c26b07..4d38a57419ec 100644
--- a/absl/random/internal/seed_material.cc
+++ b/absl/random/internal/seed_material.cc
@@ -61,6 +61,7 @@
 #endif
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace random_internal {
 namespace {
 
@@ -214,4 +215,5 @@ absl::optional<uint32_t> GetSaltMaterial() {
 }
 
 }  // namespace random_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/random/internal/seed_material.h b/absl/random/internal/seed_material.h
index 57de8a24d5e0..4be10e925685 100644
--- a/absl/random/internal/seed_material.h
+++ b/absl/random/internal/seed_material.h
@@ -27,6 +27,7 @@
 #include "absl/types/span.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace random_internal {
 
 // Returns the number of 32-bit blocks needed to contain the given number of
@@ -97,6 +98,7 @@ void MixIntoSeedMaterial(absl::Span<const uint32_t> sequence,
 absl::optional<uint32_t> GetSaltMaterial();
 
 }  // namespace random_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_RANDOM_INTERNAL_SEED_MATERIAL_H_
diff --git a/absl/random/internal/sequence_urbg.h b/absl/random/internal/sequence_urbg.h
index 9a9b57738da4..bc96a12cd29c 100644
--- a/absl/random/internal/sequence_urbg.h
+++ b/absl/random/internal/sequence_urbg.h
@@ -21,7 +21,10 @@
 #include <type_traits>
 #include <vector>
 
+#include "absl/base/config.h"
+
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace random_internal {
 
 // `sequence_urbg` is a simple random number generator which meets the
@@ -51,6 +54,7 @@ class sequence_urbg {
 };
 
 }  // namespace random_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_RANDOM_INTERNAL_SEQUENCE_URBG_H_
diff --git a/absl/random/internal/traits.h b/absl/random/internal/traits.h
index 40eb011f195f..75772bd9abb4 100644
--- a/absl/random/internal/traits.h
+++ b/absl/random/internal/traits.h
@@ -22,6 +22,7 @@
 #include "absl/base/config.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace random_internal {
 
 // random_internal::is_widening_convertible<A, B>
@@ -94,6 +95,7 @@ struct make_unsigned_bits {
 };
 
 }  // namespace random_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_RANDOM_INTERNAL_TRAITS_H_
diff --git a/absl/random/internal/uniform_helper.h b/absl/random/internal/uniform_helper.h
index f68b1823ef00..663107cb3a63 100644
--- a/absl/random/internal/uniform_helper.h
+++ b/absl/random/internal/uniform_helper.h
@@ -22,6 +22,7 @@
 #include "absl/meta/type_traits.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 template <typename IntType>
 class uniform_int_distribution;
 
@@ -173,6 +174,7 @@ struct UniformDistributionWrapper : public UniformDistribution<NumType> {
 };
 
 }  // namespace random_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_RANDOM_INTERNAL_UNIFORM_HELPER_H_
diff --git a/absl/random/internal/wide_multiply.h b/absl/random/internal/wide_multiply.h
index ebbfa1f2c10e..6e4cf1be0af4 100644
--- a/absl/random/internal/wide_multiply.h
+++ b/absl/random/internal/wide_multiply.h
@@ -31,6 +31,7 @@
 #include "absl/random/internal/traits.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace random_internal {
 
 // Helper object to multiply two 64-bit values to a 128-bit value.
@@ -104,6 +105,7 @@ struct wide_multiply<uint64_t> {
 #endif
 
 }  // namespace random_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_RANDOM_INTERNAL_WIDE_MULTIPLY_H_
diff --git a/absl/random/log_uniform_int_distribution.h b/absl/random/log_uniform_int_distribution.h
index de58bdbe14ca..960816e2f8ff 100644
--- a/absl/random/log_uniform_int_distribution.h
+++ b/absl/random/log_uniform_int_distribution.h
@@ -30,6 +30,7 @@
 #include "absl/random/uniform_int_distribution.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // log_uniform_int_distribution:
 //
@@ -247,6 +248,7 @@ std::basic_istream<CharT, Traits>& operator>>(
   return is;
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_RANDOM_LOG_UNIFORM_INT_DISTRIBUTION_H_
diff --git a/absl/random/mock_distributions.h b/absl/random/mock_distributions.h
index 1af98a24a7f0..d36d5ba03cab 100644
--- a/absl/random/mock_distributions.h
+++ b/absl/random/mock_distributions.h
@@ -53,6 +53,7 @@
 #include "absl/random/mocking_bit_gen.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // -----------------------------------------------------------------------------
 // absl::MockUniform
@@ -254,6 +255,7 @@ using MockZipf =
                                      IntType(MockingBitGen&, IntType, double,
                                              double)>;
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_RANDOM_MOCK_DISTRIBUTIONS_H_
diff --git a/absl/random/mocking_bit_gen.cc b/absl/random/mocking_bit_gen.cc
index 73144528a78e..6bb1e414aeab 100644
--- a/absl/random/mocking_bit_gen.cc
+++ b/absl/random/mocking_bit_gen.cc
@@ -18,6 +18,7 @@
 #include <string>
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 MockingBitGen::~MockingBitGen() {
 
   for (const auto& del : deleters_) {
@@ -25,4 +26,5 @@ MockingBitGen::~MockingBitGen() {
   }
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/random/mocking_bit_gen.h b/absl/random/mocking_bit_gen.h
index d1b524a993dc..36cef91113e3 100644
--- a/absl/random/mocking_bit_gen.h
+++ b/absl/random/mocking_bit_gen.h
@@ -51,6 +51,7 @@
 #include "absl/utility/utility.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 namespace random_internal {
 
@@ -189,6 +190,7 @@ struct DistributionCaller<absl::MockingBitGen> {
 };
 
 }  // namespace random_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_RANDOM_MOCKING_BIT_GEN_H_
diff --git a/absl/random/poisson_distribution.h b/absl/random/poisson_distribution.h
index 23a953ff253c..cb5f5d5d0ff7 100644
--- a/absl/random/poisson_distribution.h
+++ b/absl/random/poisson_distribution.h
@@ -28,6 +28,7 @@
 #include "absl/random/internal/iostream_state_saver.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // absl::poisson_distribution:
 // Generates discrete variates conforming to a Poisson distribution.
@@ -251,6 +252,7 @@ std::basic_istream<CharT, Traits>& operator>>(
   return is;
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_RANDOM_POISSON_DISTRIBUTION_H_
diff --git a/absl/random/random.h b/absl/random/random.h
index dc6852f4adf3..c8f326e64252 100644
--- a/absl/random/random.h
+++ b/absl/random/random.h
@@ -41,6 +41,7 @@
 #include "absl/random/seed_sequences.h"  // IWYU pragma: export
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // -----------------------------------------------------------------------------
 // absl::BitGen
@@ -182,6 +183,7 @@ using InsecureBitGen =
 // discards the intermediate results.
 // ---------------------------------------------------------------------------
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_RANDOM_RANDOM_H_
diff --git a/absl/random/seed_gen_exception.cc b/absl/random/seed_gen_exception.cc
index e4271baaa07f..fdcb54a86cdd 100644
--- a/absl/random/seed_gen_exception.cc
+++ b/absl/random/seed_gen_exception.cc
@@ -19,6 +19,7 @@
 #include "absl/base/config.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 static constexpr const char kExceptionMessage[] =
     "Failed generating seed-material for URBG.";
@@ -41,4 +42,5 @@ void ThrowSeedGenException() {
 }
 
 }  // namespace random_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/random/seed_gen_exception.h b/absl/random/seed_gen_exception.h
index b464d52fb954..535390056437 100644
--- a/absl/random/seed_gen_exception.h
+++ b/absl/random/seed_gen_exception.h
@@ -28,7 +28,10 @@
 
 #include <exception>
 
+#include "absl/base/config.h"
+
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 //------------------------------------------------------------------------------
 // SeedGenException
@@ -46,6 +49,7 @@ namespace random_internal {
 [[noreturn]] void ThrowSeedGenException();
 
 }  // namespace random_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_RANDOM_SEED_GEN_EXCEPTION_H_
diff --git a/absl/random/seed_sequences.cc b/absl/random/seed_sequences.cc
index 9f319615289a..426eafd3c8de 100644
--- a/absl/random/seed_sequences.cc
+++ b/absl/random/seed_sequences.cc
@@ -17,6 +17,7 @@
 #include "absl/random/internal/pool_urbg.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 SeedSeq MakeSeedSeq() {
   SeedSeq::result_type seed_material[8];
@@ -24,4 +25,5 @@ SeedSeq MakeSeedSeq() {
   return SeedSeq(std::begin(seed_material), std::end(seed_material));
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/random/seed_sequences.h b/absl/random/seed_sequences.h
index 631d1ecd4ea9..ff1340cc8eed 100644
--- a/absl/random/seed_sequences.h
+++ b/absl/random/seed_sequences.h
@@ -34,6 +34,7 @@
 #include "absl/types/span.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // -----------------------------------------------------------------------------
 // absl::SeedSeq
@@ -103,6 +104,7 @@ SeedSeq CreateSeedSeqFrom(URBG* urbg) {
 //
 SeedSeq MakeSeedSeq();
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_RANDOM_SEED_SEQUENCES_H_
diff --git a/absl/random/uniform_int_distribution.h b/absl/random/uniform_int_distribution.h
index dc8ba8c1e2a2..da66564a6b3c 100644
--- a/absl/random/uniform_int_distribution.h
+++ b/absl/random/uniform_int_distribution.h
@@ -40,6 +40,7 @@
 #include "absl/random/internal/wide_multiply.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // absl::uniform_int_distribution<T>
 //
@@ -268,6 +269,7 @@ uniform_int_distribution<IntType>::Generate(
   return helper::hi(product);
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_RANDOM_UNIFORM_INT_DISTRIBUTION_H_
diff --git a/absl/random/uniform_real_distribution.h b/absl/random/uniform_real_distribution.h
index bf2ed2c5ad36..5ba17b2341cf 100644
--- a/absl/random/uniform_real_distribution.h
+++ b/absl/random/uniform_real_distribution.h
@@ -45,6 +45,7 @@
 #include "absl/random/internal/iostream_state_saver.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // absl::uniform_real_distribution<T>
 //
@@ -195,6 +196,7 @@ std::basic_istream<CharT, Traits>& operator>>(
   }
   return is;
 }
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_RANDOM_UNIFORM_REAL_DISTRIBUTION_H_
diff --git a/absl/random/zipf_distribution.h b/absl/random/zipf_distribution.h
index d7b4ac38edac..22ebc756cfef 100644
--- a/absl/random/zipf_distribution.h
+++ b/absl/random/zipf_distribution.h
@@ -26,6 +26,7 @@
 #include "absl/random/uniform_real_distribution.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // absl::zipf_distribution produces random integer-values in the range [0, k],
 // distributed according to the discrete probability function:
@@ -264,6 +265,7 @@ std::basic_istream<CharT, Traits>& operator>>(
   return is;
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_RANDOM_ZIPF_DISTRIBUTION_H_
diff --git a/absl/strings/BUILD.bazel b/absl/strings/BUILD.bazel
index e38c8ad6ce66..8d0a6b6d4ef2 100644
--- a/absl/strings/BUILD.bazel
+++ b/absl/strings/BUILD.bazel
@@ -94,6 +94,7 @@ cc_library(
     ],
     copts = ABSL_DEFAULT_COPTS,
     deps = [
+        "//absl/base:config",
         "//absl/base:core_headers",
         "//absl/base:endian",
         "//absl/meta:type_traits",
@@ -413,6 +414,7 @@ cc_test(
     deps = [
         ":pow10_helper",
         ":strings",
+        "//absl/base:config",
         "//absl/base:raw_logging_internal",
         "//absl/random",
         "//absl/random:distributions",
@@ -489,6 +491,7 @@ cc_test(
     copts = ABSL_TEST_COPTS,
     deps = [
         ":strings",
+        "//absl/base:config",
         "//absl/base:raw_logging_internal",
         "@com_google_googletest//:gtest_main",
     ],
@@ -504,6 +507,7 @@ cc_test(
     copts = ABSL_TEST_COPTS,
     deps = [
         ":strings",
+        "//absl/base:config",
         "@com_google_googletest//:gtest_main",
     ],
 )
@@ -668,6 +672,7 @@ cc_library(
     srcs = ["internal/pow10_helper.cc"],
     hdrs = ["internal/pow10_helper.h"],
     visibility = ["//visibility:private"],
+    deps = ["//absl/base:config"],
 )
 
 cc_test(
diff --git a/absl/strings/CMakeLists.txt b/absl/strings/CMakeLists.txt
index cd52a472f499..98101573acdb 100644
--- a/absl/strings/CMakeLists.txt
+++ b/absl/strings/CMakeLists.txt
@@ -81,6 +81,7 @@ absl_cc_library(
   COPTS
     ${ABSL_DEFAULT_COPTS}
   DEPS
+    absl::config
     absl::core_headers
     absl::endian
     absl::type_traits
@@ -276,6 +277,7 @@ absl_cc_test(
     absl::strings
     absl::core_headers
     absl::pow10_helper
+    absl::config
     absl::raw_logging_internal
     absl::random_random
     absl::random_distributions
@@ -331,6 +333,7 @@ absl_cc_test(
     ${ABSL_TEST_COPTS}
   DEPS
     absl::strings
+    absl::config
     absl::raw_logging_internal
     gmock_main
 )
@@ -346,6 +349,7 @@ absl_cc_test(
     ${ABSL_TEST_COPTS}
   DEPS
     absl::strings
+    absl::config
     gmock_main
 )
 
@@ -502,6 +506,8 @@ absl_cc_library(
     "internal/pow10_helper.cc"
   COPTS
     ${ABSL_TEST_COPTS}
+  DEPS
+    absl::config
   TESTONLY
 )
 
diff --git a/absl/strings/ascii.cc b/absl/strings/ascii.cc
index 3f7c581f139f..abea3e4fd38c 100644
--- a/absl/strings/ascii.cc
+++ b/absl/strings/ascii.cc
@@ -15,6 +15,7 @@
 #include "absl/strings/ascii.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace ascii_internal {
 
 // # Table generated by this Python code (bit 0x02 is currently unused):
@@ -195,4 +196,5 @@ void RemoveExtraAsciiWhitespace(std::string* str) {
   str->erase(output_it - &(*str)[0]);
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/strings/ascii.h b/absl/strings/ascii.h
index f9e4fd1dbcaf..792aabe5364a 100644
--- a/absl/strings/ascii.h
+++ b/absl/strings/ascii.h
@@ -59,6 +59,7 @@
 #include "absl/strings/string_view.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace ascii_internal {
 
 // Declaration for an array of bitfields holding character information.
@@ -234,6 +235,7 @@ inline void StripAsciiWhitespace(std::string* str) {
 // Removes leading, trailing, and consecutive internal whitespace.
 void RemoveExtraAsciiWhitespace(std::string*);
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_STRINGS_ASCII_H_
diff --git a/absl/strings/charconv.cc b/absl/strings/charconv.cc
index bc07e7ab9e4f..d9bc2dd20828 100644
--- a/absl/strings/charconv.cc
+++ b/absl/strings/charconv.cc
@@ -57,6 +57,7 @@
 // narrower mantissas.
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace {
 
 template <typename FloatType>
@@ -980,4 +981,5 @@ const int16_t kPower10ExponentTable[] = {
 };
 
 }  // namespace
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/strings/charconv.h b/absl/strings/charconv.h
index 3f5891ba7f3f..e04be32f9514 100644
--- a/absl/strings/charconv.h
+++ b/absl/strings/charconv.h
@@ -17,7 +17,10 @@
 
 #include <system_error>  // NOLINT(build/c++11)
 
+#include "absl/base/config.h"
+
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // Workalike compatibilty version of std::chars_format from C++17.
 //
@@ -110,6 +113,7 @@ inline chars_format& operator^=(chars_format& lhs, chars_format rhs) {
   return lhs;
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_STRINGS_CHARCONV_H_
diff --git a/absl/strings/escaping.cc b/absl/strings/escaping.cc
index 18b746e37d2a..d2fcd9c111bc 100644
--- a/absl/strings/escaping.cc
+++ b/absl/strings/escaping.cc
@@ -33,6 +33,7 @@
 #include "absl/strings/string_view.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace {
 
 // These are used for the leave_nulls_escaped argument to CUnescapeInternal().
@@ -1106,4 +1107,5 @@ std::string BytesToHexString(absl::string_view from) {
   return result;
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/strings/escaping.h b/absl/strings/escaping.h
index 198b934875e5..f5ca26c5dadb 100644
--- a/absl/strings/escaping.h
+++ b/absl/strings/escaping.h
@@ -33,6 +33,7 @@
 #include "absl/strings/string_view.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // CUnescape()
 //
@@ -157,6 +158,7 @@ std::string HexStringToBytes(absl::string_view from);
 // `2*from.size()`.
 std::string BytesToHexString(absl::string_view from);
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_STRINGS_ESCAPING_H_
diff --git a/absl/strings/internal/char_map.h b/absl/strings/internal/char_map.h
index b9108b8cddd0..a76e60362b11 100644
--- a/absl/strings/internal/char_map.h
+++ b/absl/strings/internal/char_map.h
@@ -28,6 +28,7 @@
 #include "absl/base/port.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace strings_internal {
 
 class Charmap {
@@ -149,6 +150,7 @@ constexpr Charmap GraphCharmap() { return PrintCharmap() & ~SpaceCharmap(); }
 constexpr Charmap PunctCharmap() { return GraphCharmap() & ~AlnumCharmap(); }
 
 }  // namespace strings_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_STRINGS_INTERNAL_CHAR_MAP_H_
diff --git a/absl/strings/internal/charconv_bigint.cc b/absl/strings/internal/charconv_bigint.cc
index 95d471d9e22c..860c27b25681 100644
--- a/absl/strings/internal/charconv_bigint.cc
+++ b/absl/strings/internal/charconv_bigint.cc
@@ -19,6 +19,7 @@
 #include <string>
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace strings_internal {
 
 namespace {
@@ -354,4 +355,5 @@ template class BigUnsigned<4>;
 template class BigUnsigned<84>;
 
 }  // namespace strings_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/strings/internal/charconv_bigint.h b/absl/strings/internal/charconv_bigint.h
index 7da9a7e75ace..108e1eb29049 100644
--- a/absl/strings/internal/charconv_bigint.h
+++ b/absl/strings/internal/charconv_bigint.h
@@ -25,6 +25,7 @@
 #include "absl/strings/string_view.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace strings_internal {
 
 // The largest power that 5 that can be raised to, and still fit in a uint32_t.
@@ -414,6 +415,7 @@ extern template class BigUnsigned<4>;
 extern template class BigUnsigned<84>;
 
 }  // namespace strings_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_STRINGS_INTERNAL_CHARCONV_BIGINT_H_
diff --git a/absl/strings/internal/charconv_bigint_test.cc b/absl/strings/internal/charconv_bigint_test.cc
index 745714aca1b3..363bcb03d938 100644
--- a/absl/strings/internal/charconv_bigint_test.cc
+++ b/absl/strings/internal/charconv_bigint_test.cc
@@ -19,6 +19,7 @@
 #include "gtest/gtest.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace strings_internal {
 
 TEST(BigUnsigned, ShiftLeft) {
@@ -200,4 +201,5 @@ TEST(BigUnsigned, TenToTheNth) {
 
 
 }  // namespace strings_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/strings/internal/charconv_parse.cc b/absl/strings/internal/charconv_parse.cc
index fa9a8965fe6b..d9a57a782206 100644
--- a/absl/strings/internal/charconv_parse.cc
+++ b/absl/strings/internal/charconv_parse.cc
@@ -22,6 +22,7 @@
 #include "absl/strings/internal/memutil.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace {
 
 // ParseFloat<10> will read the first 19 significant digits of the mantissa.
@@ -499,4 +500,5 @@ template ParsedFloat ParseFloat<16>(const char* begin, const char* end,
                                     chars_format format_flags);
 
 }  // namespace strings_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/strings/internal/charconv_parse.h b/absl/strings/internal/charconv_parse.h
index 44d06b2e9bd4..505998b5394a 100644
--- a/absl/strings/internal/charconv_parse.h
+++ b/absl/strings/internal/charconv_parse.h
@@ -17,9 +17,11 @@
 
 #include <cstdint>
 
+#include "absl/base/config.h"
 #include "absl/strings/charconv.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace strings_internal {
 
 // Enum indicating whether a parsed float is a number or special value.
@@ -92,5 +94,6 @@ extern template ParsedFloat ParseFloat<16>(const char* begin, const char* end,
                                            absl::chars_format format_flags);
 
 }  // namespace strings_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 #endif  // ABSL_STRINGS_INTERNAL_CHARCONV_PARSE_H_
diff --git a/absl/strings/internal/escaping_test_common.h b/absl/strings/internal/escaping_test_common.h
index bd8030318173..7b18017a0890 100644
--- a/absl/strings/internal/escaping_test_common.h
+++ b/absl/strings/internal/escaping_test_common.h
@@ -22,6 +22,7 @@
 #include "absl/strings/string_view.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace strings_internal {
 
 struct base64_testcase {
@@ -126,6 +127,7 @@ inline const std::array<base64_testcase, 5>& base64_strings() {
 }
 
 }  // namespace strings_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_STRINGS_INTERNAL_ESCAPING_TEST_COMMON_H_
diff --git a/absl/strings/internal/memutil.cc b/absl/strings/internal/memutil.cc
index 77aa63c2c372..2519c6881e35 100644
--- a/absl/strings/internal/memutil.cc
+++ b/absl/strings/internal/memutil.cc
@@ -17,6 +17,7 @@
 #include <cstdlib>
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace strings_internal {
 
 int memcasecmp(const char* s1, const char* s2, size_t len) {
@@ -107,4 +108,5 @@ const char* memmatch(const char* phaystack, size_t haylen, const char* pneedle,
 }
 
 }  // namespace strings_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/strings/internal/memutil.h b/absl/strings/internal/memutil.h
index 7c071a8201fa..9ad05358086c 100644
--- a/absl/strings/internal/memutil.h
+++ b/absl/strings/internal/memutil.h
@@ -69,6 +69,7 @@
 #include "absl/strings/ascii.h"  // for absl::ascii_tolower
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace strings_internal {
 
 inline char* memcat(char* dest, size_t destlen, const char* src,
@@ -141,6 +142,7 @@ const char* memmatch(const char* phaystack, size_t haylen, const char* pneedle,
                      size_t neelen);
 
 }  // namespace strings_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_STRINGS_INTERNAL_MEMUTIL_H_
diff --git a/absl/strings/internal/numbers_test_common.h b/absl/strings/internal/numbers_test_common.h
index a263219e27b4..1a1e50c4d899 100644
--- a/absl/strings/internal/numbers_test_common.h
+++ b/absl/strings/internal/numbers_test_common.h
@@ -23,7 +23,10 @@
 #include <limits>
 #include <string>
 
+#include "absl/base/config.h"
+
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace strings_internal {
 
 template <typename IntType>
@@ -175,6 +178,7 @@ inline const std::array<uint64_test_case, 34>& strtouint64_test_cases() {
 }
 
 }  // namespace strings_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_STRINGS_INTERNAL_NUMBERS_TEST_COMMON_H_
diff --git a/absl/strings/internal/ostringstream.cc b/absl/strings/internal/ostringstream.cc
index d0f0f84b6ae4..05324c780c60 100644
--- a/absl/strings/internal/ostringstream.cc
+++ b/absl/strings/internal/ostringstream.cc
@@ -15,6 +15,7 @@
 #include "absl/strings/internal/ostringstream.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace strings_internal {
 
 OStringStream::Buf::int_type OStringStream::overflow(int c) {
@@ -31,4 +32,5 @@ std::streamsize OStringStream::xsputn(const char* s, std::streamsize n) {
 }
 
 }  // namespace strings_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/strings/internal/ostringstream.h b/absl/strings/internal/ostringstream.h
index 207920151b78..d25d60473f6d 100644
--- a/absl/strings/internal/ostringstream.h
+++ b/absl/strings/internal/ostringstream.h
@@ -23,6 +23,7 @@
 #include "absl/base/port.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace strings_internal {
 
 // The same as std::ostringstream but appends to a user-specified std::string,
@@ -82,6 +83,7 @@ class OStringStream : private std::basic_streambuf<char>, public std::ostream {
 };
 
 }  // namespace strings_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_STRINGS_INTERNAL_OSTRINGSTREAM_H_
diff --git a/absl/strings/internal/pow10_helper.cc b/absl/strings/internal/pow10_helper.cc
index 03ed8d07cd42..42e96c3425d2 100644
--- a/absl/strings/internal/pow10_helper.cc
+++ b/absl/strings/internal/pow10_helper.cc
@@ -17,6 +17,7 @@
 #include <cmath>
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace strings_internal {
 
 namespace {
@@ -117,4 +118,5 @@ double Pow10(int exp) {
 }
 
 }  // namespace strings_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/strings/internal/pow10_helper.h b/absl/strings/internal/pow10_helper.h
index 9d1aa710db5a..c37c2c3ffee5 100644
--- a/absl/strings/internal/pow10_helper.h
+++ b/absl/strings/internal/pow10_helper.h
@@ -22,7 +22,10 @@
 
 #include <vector>
 
+#include "absl/base/config.h"
+
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace strings_internal {
 
 // Computes the precise value of 10^exp. (I.e. the nearest representable
@@ -31,6 +34,7 @@ namespace strings_internal {
 double Pow10(int exp);
 
 }  // namespace strings_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_STRINGS_INTERNAL_POW10_HELPER_H_
diff --git a/absl/strings/internal/pow10_helper_test.cc b/absl/strings/internal/pow10_helper_test.cc
index a4a68b5dab31..a4ff76d31e10 100644
--- a/absl/strings/internal/pow10_helper_test.cc
+++ b/absl/strings/internal/pow10_helper_test.cc
@@ -20,6 +20,7 @@
 #include "absl/strings/str_format.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace strings_internal {
 
 namespace {
@@ -117,4 +118,5 @@ TEST(Pow10HelperTest, Works) {
 
 }  // namespace
 }  // namespace strings_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/strings/internal/resize_uninitialized.h b/absl/strings/internal/resize_uninitialized.h
index 0f5e964d62bc..e42628e3949a 100644
--- a/absl/strings/internal/resize_uninitialized.h
+++ b/absl/strings/internal/resize_uninitialized.h
@@ -25,6 +25,7 @@
 #include "absl/meta/type_traits.h"  //  for void_t
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace strings_internal {
 
 // Is a subclass of true_type or false_type, depending on whether or not
@@ -66,6 +67,7 @@ inline void STLStringResizeUninitialized(string_type* s, size_t new_size) {
 }
 
 }  // namespace strings_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_STRINGS_INTERNAL_RESIZE_UNINITIALIZED_H_
diff --git a/absl/strings/internal/stl_type_traits.h b/absl/strings/internal/stl_type_traits.h
index 202ab374a833..6035ca45cbd2 100644
--- a/absl/strings/internal/stl_type_traits.h
+++ b/absl/strings/internal/stl_type_traits.h
@@ -40,6 +40,7 @@
 #include "absl/meta/type_traits.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace strings_internal {
 
 template <typename C, template <typename...> class T>
@@ -242,5 +243,6 @@ struct IsStrictlyBaseOfAndConvertibleToSTLContainer
                         IsConvertibleToSTLContainer<C>> {};
 
 }  // namespace strings_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 #endif  // ABSL_STRINGS_INTERNAL_STL_TYPE_TRAITS_H_
diff --git a/absl/strings/internal/str_format/arg.cc b/absl/strings/internal/str_format/arg.cc
index b567a5c5bcf0..875bd99c4286 100644
--- a/absl/strings/internal/str_format/arg.cc
+++ b/absl/strings/internal/str_format/arg.cc
@@ -14,6 +14,7 @@
 #include "absl/strings/internal/str_format/float_conversion.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace str_format_internal {
 namespace {
 
@@ -386,4 +387,5 @@ ABSL_INTERNAL_FORMAT_DISPATCH_OVERLOADS_EXPAND_();
 
 }  // namespace str_format_internal
 
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/strings/internal/str_format/arg.h b/absl/strings/internal/str_format/arg.h
index a209a9275417..b672a2294416 100644
--- a/absl/strings/internal/str_format/arg.h
+++ b/absl/strings/internal/str_format/arg.h
@@ -19,6 +19,7 @@
 #include "absl/strings/string_view.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 class Cord;
 class FormatCountCapture;
@@ -426,6 +427,7 @@ ABSL_INTERNAL_FORMAT_DISPATCH_OVERLOADS_EXPAND_(extern);
 
 
 }  // namespace str_format_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_STRINGS_INTERNAL_STR_FORMAT_ARG_H_
diff --git a/absl/strings/internal/str_format/arg_test.cc b/absl/strings/internal/str_format/arg_test.cc
index 3421fac11bf9..96c9cfd335b5 100644
--- a/absl/strings/internal/str_format/arg_test.cc
+++ b/absl/strings/internal/str_format/arg_test.cc
@@ -14,6 +14,7 @@
 #include "absl/strings/str_format.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace str_format_internal {
 namespace {
 
@@ -108,4 +109,5 @@ const char kMyArray[] = "ABCDE";
 
 }  // namespace
 }  // namespace str_format_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/strings/internal/str_format/bind.cc b/absl/strings/internal/str_format/bind.cc
index 45e335a30948..1ee281af9c16 100644
--- a/absl/strings/internal/str_format/bind.cc
+++ b/absl/strings/internal/str_format/bind.cc
@@ -6,6 +6,7 @@
 #include <string>
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace str_format_internal {
 
 namespace {
@@ -236,4 +237,5 @@ int SnprintF(char* output, size_t size, const UntypedFormatSpecImpl format,
 }
 
 }  // namespace str_format_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/strings/internal/str_format/bind.h b/absl/strings/internal/str_format/bind.h
index dafcd6102f91..2bf0c0855034 100644
--- a/absl/strings/internal/str_format/bind.h
+++ b/absl/strings/internal/str_format/bind.h
@@ -13,6 +13,7 @@
 #include "absl/types/span.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 class UntypedFormatSpec;
 
@@ -202,6 +203,7 @@ class StreamedWrapper {
 };
 
 }  // namespace str_format_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_STRINGS_INTERNAL_STR_FORMAT_BIND_H_
diff --git a/absl/strings/internal/str_format/bind_test.cc b/absl/strings/internal/str_format/bind_test.cc
index 2574801a5c38..f6817419feb4 100644
--- a/absl/strings/internal/str_format/bind_test.cc
+++ b/absl/strings/internal/str_format/bind_test.cc
@@ -6,6 +6,7 @@
 #include "gtest/gtest.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace str_format_internal {
 namespace {
 
@@ -138,4 +139,5 @@ TEST_F(FormatBindTest, FormatPack) {
 
 }  // namespace
 }  // namespace str_format_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/strings/internal/str_format/checker.h b/absl/strings/internal/str_format/checker.h
index 04a888275185..8993a79b9580 100644
--- a/absl/strings/internal/str_format/checker.h
+++ b/absl/strings/internal/str_format/checker.h
@@ -14,6 +14,7 @@
 #endif  // ABSL_INTERNAL_ENABLE_FORMAT_CHECKER
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace str_format_internal {
 
 constexpr bool AllOf() { return true; }
@@ -319,6 +320,7 @@ constexpr bool ValidFormatImpl(string_view format) {
 #endif  // ABSL_INTERNAL_ENABLE_FORMAT_CHECKER
 
 }  // namespace str_format_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_STRINGS_INTERNAL_STR_FORMAT_CHECKER_H_
diff --git a/absl/strings/internal/str_format/checker_test.cc b/absl/strings/internal/str_format/checker_test.cc
index 7aa194a7fa90..c309e20310a1 100644
--- a/absl/strings/internal/str_format/checker_test.cc
+++ b/absl/strings/internal/str_format/checker_test.cc
@@ -5,6 +5,7 @@
 #include "absl/strings/str_format.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace str_format_internal {
 namespace {
 
@@ -147,4 +148,5 @@ TEST(StrFormatChecker, LongFormat) {
 
 }  // namespace
 }  // namespace str_format_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/strings/internal/str_format/convert_test.cc b/absl/strings/internal/str_format/convert_test.cc
index 5f198059fe5f..ca99434679cf 100644
--- a/absl/strings/internal/str_format/convert_test.cc
+++ b/absl/strings/internal/str_format/convert_test.cc
@@ -11,6 +11,7 @@
 #include "absl/strings/internal/str_format/bind.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace str_format_internal {
 namespace {
 
@@ -646,4 +647,5 @@ TEST_F(FormatConvertTest, ExpectedFailures) {
 
 }  // namespace
 }  // namespace str_format_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/strings/internal/str_format/extension.cc b/absl/strings/internal/str_format/extension.cc
index d7f58159d5fb..559011bf4a97 100644
--- a/absl/strings/internal/str_format/extension.cc
+++ b/absl/strings/internal/str_format/extension.cc
@@ -20,6 +20,7 @@
 #include <string>
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace str_format_internal {
 namespace {
 // clang-format off
@@ -81,4 +82,5 @@ bool FormatSinkImpl::PutPaddedString(string_view v, int w, int p, bool l) {
 }
 
 }  // namespace str_format_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/strings/internal/str_format/extension.h b/absl/strings/internal/str_format/extension.h
index 3f4788c9f502..5726ea5c100b 100644
--- a/absl/strings/internal/str_format/extension.h
+++ b/absl/strings/internal/str_format/extension.h
@@ -26,6 +26,7 @@
 #include "absl/strings/string_view.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 class Cord;
 
@@ -406,6 +407,7 @@ inline size_t Excess(size_t used, size_t capacity) {
 
 }  // namespace str_format_internal
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_STRINGS_INTERNAL_STR_FORMAT_EXTENSION_H_
diff --git a/absl/strings/internal/str_format/float_conversion.cc b/absl/strings/internal/str_format/float_conversion.cc
index 9236acdc74cb..ebe4da5b4233 100644
--- a/absl/strings/internal/str_format/float_conversion.cc
+++ b/absl/strings/internal/str_format/float_conversion.cc
@@ -9,6 +9,7 @@
 #include "absl/base/config.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace str_format_internal {
 
 namespace {
@@ -482,4 +483,5 @@ bool ConvertFloatImpl(double v, const ConversionSpec &conv,
 }
 
 }  // namespace str_format_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/strings/internal/str_format/float_conversion.h b/absl/strings/internal/str_format/float_conversion.h
index 8ba5566d3eef..49a6a63630ee 100644
--- a/absl/strings/internal/str_format/float_conversion.h
+++ b/absl/strings/internal/str_format/float_conversion.h
@@ -4,6 +4,7 @@
 #include "absl/strings/internal/str_format/extension.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace str_format_internal {
 
 bool ConvertFloatImpl(float v, const ConversionSpec &conv,
@@ -16,6 +17,7 @@ bool ConvertFloatImpl(long double v, const ConversionSpec &conv,
                       FormatSinkImpl *sink);
 
 }  // namespace str_format_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_STRINGS_INTERNAL_STR_FORMAT_FLOAT_CONVERSION_H_
diff --git a/absl/strings/internal/str_format/output.cc b/absl/strings/internal/str_format/output.cc
index 38987b6385dd..c4b24706132c 100644
--- a/absl/strings/internal/str_format/output.cc
+++ b/absl/strings/internal/str_format/output.cc
@@ -18,6 +18,7 @@
 #include <cstring>
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace str_format_internal {
 
 namespace {
@@ -67,4 +68,5 @@ void FILERawSink::Write(string_view v) {
 }
 
 }  // namespace str_format_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/strings/internal/str_format/output.h b/absl/strings/internal/str_format/output.h
index 6dc2f3f721f6..28b288b7dde3 100644
--- a/absl/strings/internal/str_format/output.h
+++ b/absl/strings/internal/str_format/output.h
@@ -29,6 +29,7 @@
 #include "absl/strings/string_view.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 class Cord;
 
@@ -97,6 +98,7 @@ auto InvokeFlush(T* out, string_view s)
 }
 
 }  // namespace str_format_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_STRINGS_INTERNAL_STR_FORMAT_OUTPUT_H_
diff --git a/absl/strings/internal/str_format/output_test.cc b/absl/strings/internal/str_format/output_test.cc
index 6e04abef4d91..e54e6f70a511 100644
--- a/absl/strings/internal/str_format/output_test.cc
+++ b/absl/strings/internal/str_format/output_test.cc
@@ -21,6 +21,7 @@
 #include "gtest/gtest.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace {
 
 TEST(InvokeFlush, String) {
@@ -67,5 +68,6 @@ TEST(BufferRawSink, Limits) {
 }
 
 }  // namespace
+ABSL_NAMESPACE_END
 }  // namespace absl
 
diff --git a/absl/strings/internal/str_format/parser.cc b/absl/strings/internal/str_format/parser.cc
index 9ef5615cc9ee..eff68f35c032 100644
--- a/absl/strings/internal/str_format/parser.cc
+++ b/absl/strings/internal/str_format/parser.cc
@@ -14,6 +14,7 @@
 #include <unordered_set>
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace str_format_internal {
 
 using CC = ConversionChar::Id;
@@ -300,4 +301,5 @@ bool ParsedFormatBase::MatchesConversions(
 }
 
 }  // namespace str_format_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/strings/internal/str_format/parser.h b/absl/strings/internal/str_format/parser.h
index 4b441f7193a5..116dda06d4e2 100644
--- a/absl/strings/internal/str_format/parser.h
+++ b/absl/strings/internal/str_format/parser.h
@@ -16,6 +16,7 @@
 #include "absl/strings/internal/str_format/extension.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace str_format_internal {
 
 // The analyzed properties of a single specified conversion.
@@ -317,6 +318,7 @@ class ExtendedParsedFormat : public str_format_internal::ParsedFormatBase {
       : ParsedFormatBase(s, allow_ignored, {C...}) {}
 };
 }  // namespace str_format_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_STRINGS_INTERNAL_STR_FORMAT_PARSER_H_
diff --git a/absl/strings/internal/str_format/parser_test.cc b/absl/strings/internal/str_format/parser_test.cc
index 6d356093ce60..33ed8f094436 100644
--- a/absl/strings/internal/str_format/parser_test.cc
+++ b/absl/strings/internal/str_format/parser_test.cc
@@ -7,6 +7,7 @@
 #include "absl/base/macros.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace str_format_internal {
 
 namespace {
@@ -389,4 +390,5 @@ TEST_F(ParsedFormatTest, ParsingFlagOrder) {
 
 }  // namespace
 }  // namespace str_format_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/strings/internal/str_join_internal.h b/absl/strings/internal/str_join_internal.h
index 7c35f4de05ed..31dbf672f0b6 100644
--- a/absl/strings/internal/str_join_internal.h
+++ b/absl/strings/internal/str_join_internal.h
@@ -43,6 +43,7 @@
 #include "absl/strings/str_cat.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace strings_internal {
 
 //
@@ -307,6 +308,7 @@ std::string JoinRange(const Range& range, absl::string_view separator) {
 }
 
 }  // namespace strings_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_STRINGS_INTERNAL_STR_JOIN_INTERNAL_H_
diff --git a/absl/strings/internal/str_split_internal.h b/absl/strings/internal/str_split_internal.h
index 52f6222615ce..b54f6ebe09e0 100644
--- a/absl/strings/internal/str_split_internal.h
+++ b/absl/strings/internal/str_split_internal.h
@@ -47,6 +47,7 @@
 #endif  // _GLIBCXX_DEBUG
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace strings_internal {
 
 // This class is implicitly constructible from everything that absl::string_view
@@ -448,6 +449,7 @@ class Splitter {
 };
 
 }  // namespace strings_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_STRINGS_INTERNAL_STR_SPLIT_INTERNAL_H_
diff --git a/absl/strings/internal/utf8.cc b/absl/strings/internal/utf8.cc
index 82d36c24b34f..8fd8edc1ec6f 100644
--- a/absl/strings/internal/utf8.cc
+++ b/absl/strings/internal/utf8.cc
@@ -17,6 +17,7 @@
 #include "absl/strings/internal/utf8.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace strings_internal {
 
 size_t EncodeUTF8Char(char *buffer, char32_t utf8_char) {
@@ -48,4 +49,5 @@ size_t EncodeUTF8Char(char *buffer, char32_t utf8_char) {
 }
 
 }  // namespace strings_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/strings/internal/utf8.h b/absl/strings/internal/utf8.h
index 0423630473b1..32fb1093bea3 100644
--- a/absl/strings/internal/utf8.h
+++ b/absl/strings/internal/utf8.h
@@ -20,7 +20,10 @@
 #include <cstddef>
 #include <cstdint>
 
+#include "absl/base/config.h"
+
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace strings_internal {
 
 // For Unicode code points 0 through 0x10FFFF, EncodeUTF8Char writes
@@ -41,6 +44,7 @@ enum { kMaxEncodedUTF8Size = 4 };
 size_t EncodeUTF8Char(char *buffer, char32_t utf8_char);
 
 }  // namespace strings_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_STRINGS_INTERNAL_UTF8_H_
diff --git a/absl/strings/match.cc b/absl/strings/match.cc
index 7b24241adf5b..8127cb0c5e77 100644
--- a/absl/strings/match.cc
+++ b/absl/strings/match.cc
@@ -17,6 +17,7 @@
 #include "absl/strings/internal/memutil.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 bool EqualsIgnoreCase(absl::string_view piece1, absl::string_view piece2) {
   return (piece1.size() == piece2.size() &&
@@ -35,4 +36,5 @@ bool EndsWithIgnoreCase(absl::string_view text, absl::string_view suffix) {
          EqualsIgnoreCase(text.substr(text.size() - suffix.size()), suffix);
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/strings/match.h b/absl/strings/match.h
index 762f359f7967..90fca98ad2cf 100644
--- a/absl/strings/match.h
+++ b/absl/strings/match.h
@@ -20,7 +20,7 @@
 // This file contains simple utilities for performing string matching checks.
 // All of these function parameters are specified as `absl::string_view`,
 // meaning that these functions can accept `std::string`, `absl::string_view` or
-// nul-terminated C-style strings.
+// NUL-terminated C-style strings.
 //
 // Examples:
 //   std::string s = "foo";
@@ -38,6 +38,7 @@
 #include "absl/strings/string_view.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // StrContains()
 //
@@ -83,6 +84,7 @@ bool StartsWithIgnoreCase(absl::string_view text, absl::string_view prefix);
 // case in the comparison.
 bool EndsWithIgnoreCase(absl::string_view text, absl::string_view suffix);
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_STRINGS_MATCH_H_
diff --git a/absl/strings/numbers.cc b/absl/strings/numbers.cc
index 4890bd54a549..caab463161eb 100644
--- a/absl/strings/numbers.cc
+++ b/absl/strings/numbers.cc
@@ -40,6 +40,7 @@
 #include "absl/strings/str_cat.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 bool SimpleAtof(absl::string_view str, float* out) {
   *out = 0.0;
@@ -911,4 +912,5 @@ bool safe_strtou128_base(absl::string_view text, uint128* value, int base) {
 }
 
 }  // namespace numbers_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/strings/numbers.h b/absl/strings/numbers.h
index 7a0d6f50166d..612046838b8d 100644
--- a/absl/strings/numbers.h
+++ b/absl/strings/numbers.h
@@ -51,6 +51,7 @@
 #include "absl/strings/string_view.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // SimpleAtoi()
 //
@@ -95,11 +96,13 @@ ABSL_MUST_USE_RESULT bool SimpleAtod(absl::string_view str, double* out);
 // unspecified state.
 ABSL_MUST_USE_RESULT bool SimpleAtob(absl::string_view str, bool* out);
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 // End of public API.  Implementation details follow.
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace numbers_internal {
 
 // Digit conversion.
@@ -254,6 +257,7 @@ ABSL_MUST_USE_RESULT inline bool SimpleAtoi(absl::string_view str,
   return numbers_internal::safe_strtou128_base(str, out, 10);
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_STRINGS_NUMBERS_H_
diff --git a/absl/strings/str_cat.cc b/absl/strings/str_cat.cc
index 4bd56f5f4386..d9afe2f38520 100644
--- a/absl/strings/str_cat.cc
+++ b/absl/strings/str_cat.cc
@@ -25,6 +25,7 @@
 #include "absl/strings/numbers.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 AlphaNum::AlphaNum(Hex hex) {
   static_assert(numbers_internal::kFastToBufferSize >= 32,
@@ -241,4 +242,5 @@ void StrAppend(std::string* dest, const AlphaNum& a, const AlphaNum& b,
   assert(out == begin + dest->size());
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/strings/str_cat.h b/absl/strings/str_cat.h
index 663a1945baad..292fa235974b 100644
--- a/absl/strings/str_cat.h
+++ b/absl/strings/str_cat.h
@@ -64,6 +64,7 @@
 #include "absl/strings/string_view.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 namespace strings_internal {
 // AlphaNumBuffer allows a way to pass a string to StrCat without having to do
@@ -401,6 +402,7 @@ SixDigits(double d) {
   return result;
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_STRINGS_STR_CAT_H_
diff --git a/absl/strings/str_format.h b/absl/strings/str_format.h
index c11c93a24837..fbbfe43d6cb7 100644
--- a/absl/strings/str_format.h
+++ b/absl/strings/str_format.h
@@ -82,6 +82,7 @@
 #include "absl/strings/internal/str_format/parser.h"  // IWYU pragma: export
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // UntypedFormatSpec
 //
@@ -530,6 +531,7 @@ ABSL_MUST_USE_RESULT inline bool FormatUntyped(
       str_format_internal::UntypedFormatSpecImpl::Extract(format), args);
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_STRINGS_STR_FORMAT_H_
diff --git a/absl/strings/str_format_test.cc b/absl/strings/str_format_test.cc
index cfd81bb34be3..d33bcaa2e466 100644
--- a/absl/strings/str_format_test.cc
+++ b/absl/strings/str_format_test.cc
@@ -10,6 +10,7 @@
 #include "absl/strings/string_view.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace {
 using str_format_internal::FormatArgImpl;
 
@@ -622,6 +623,7 @@ TEST_F(FormatWrapperTest, ParsedFormat) {
 }
 
 }  // namespace
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 // Some codegen thunks that we can use to easily dump the generated assembly for
diff --git a/absl/strings/str_join.h b/absl/strings/str_join.h
index 4772f5d17c89..ae5731a42b3d 100644
--- a/absl/strings/str_join.h
+++ b/absl/strings/str_join.h
@@ -60,6 +60,7 @@
 #include "absl/strings/string_view.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // -----------------------------------------------------------------------------
 // Concept: Formatter
@@ -286,6 +287,7 @@ std::string StrJoin(const std::tuple<T...>& value,
   return strings_internal::JoinAlgorithm(value, separator, AlphaNumFormatter());
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_STRINGS_STR_JOIN_H_
diff --git a/absl/strings/str_replace.cc b/absl/strings/str_replace.cc
index 280f63d32a9e..2bd5fa98218c 100644
--- a/absl/strings/str_replace.cc
+++ b/absl/strings/str_replace.cc
@@ -17,6 +17,7 @@
 #include "absl/strings/str_cat.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace strings_internal {
 
 using FixedMapping =
@@ -77,4 +78,5 @@ int StrReplaceAll(strings_internal::FixedMapping replacements,
   return StrReplaceAll<strings_internal::FixedMapping>(replacements, target);
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/strings/str_replace.h b/absl/strings/str_replace.h
index 30540d02cdf4..273c7077353e 100644
--- a/absl/strings/str_replace.h
+++ b/absl/strings/str_replace.h
@@ -46,6 +46,7 @@
 #include "absl/strings/string_view.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // StrReplaceAll()
 //
@@ -212,6 +213,7 @@ int StrReplaceAll(const StrToStrMapping& replacements, std::string* target) {
   return substitutions;
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_STRINGS_STR_REPLACE_H_
diff --git a/absl/strings/str_split.cc b/absl/strings/str_split.cc
index 25931307f4eb..d0f8666910aa 100644
--- a/absl/strings/str_split.cc
+++ b/absl/strings/str_split.cc
@@ -27,6 +27,7 @@
 #include "absl/strings/ascii.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 namespace {
 
@@ -134,4 +135,5 @@ absl::string_view ByLength::Find(absl::string_view text,
   return absl::string_view(substr.data() + length_, 0);
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/strings/str_split.h b/absl/strings/str_split.h
index 7333078938b9..a79cd4a0ce0d 100644
--- a/absl/strings/str_split.h
+++ b/absl/strings/str_split.h
@@ -49,6 +49,7 @@
 #include "absl/strings/strip.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 //------------------------------------------------------------------------------
 // Delimiters
@@ -506,6 +507,7 @@ StrSplit(strings_internal::ConvertibleToStringView text, Delimiter d,
       std::move(text), DelimiterType(d), std::move(p));
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_STRINGS_STR_SPLIT_H_
diff --git a/absl/strings/string_view.cc b/absl/strings/string_view.cc
index d5e1a3de9ff3..c5f5de936deb 100644
--- a/absl/strings/string_view.cc
+++ b/absl/strings/string_view.cc
@@ -24,6 +24,7 @@
 #include "absl/strings/internal/memutil.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 namespace {
 void WritePadding(std::ostream& o, size_t pad) {
@@ -228,6 +229,7 @@ constexpr string_view::size_type string_view::npos;
 ABSL_STRING_VIEW_SELECTANY
 constexpr string_view::size_type string_view::kMaxSize;
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_USES_STD_STRING_VIEW
diff --git a/absl/strings/string_view.h b/absl/strings/string_view.h
index 6a650874aa27..4b34e5634f13 100644
--- a/absl/strings/string_view.h
+++ b/absl/strings/string_view.h
@@ -35,7 +35,9 @@
 #include <string_view>  // IWYU pragma: export
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 using std::string_view;
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #else  // ABSL_USES_STD_STRING_VIEW
@@ -61,6 +63,7 @@ using std::string_view;
 #include "absl/base/port.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // absl::string_view
 //
@@ -109,10 +112,10 @@ namespace absl {
 // example, when splitting a string, `std::vector<absl::string_view>` is a
 // natural data type for the output.
 //
-// When constructed from a source which is nul-terminated, the `string_view`
-// itself will not include the nul-terminator unless a specific size (including
-// the nul) is passed to the constructor. As a result, common idioms that work
-// on nul-terminated strings do not work on `string_view` objects. If you write
+// When constructed from a source which is NUL-terminated, the `string_view`
+// itself will not include the NUL-terminator unless a specific size (including
+// the NUL) is passed to the constructor. As a result, common idioms that work
+// on NUL-terminated strings do not work on `string_view` objects. If you write
 // code that scans a `string_view`, you must check its length rather than test
 // for nul, for example. Note, however, that nuls may still be embedded within
 // a `string_view` explicitly.
@@ -179,7 +182,7 @@ class string_view {
       // doesn't need to be reevaluated after `ptr_` is set.
       : string_view(str.data(), str.size()) {}
 
-  // Implicit constructor of a `string_view` from nul-terminated `str`. When
+  // 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)
@@ -309,8 +312,8 @@ class string_view {
   //
   // Returns a pointer to the underlying character array (which is of course
   // stored elsewhere). Note that `string_view::data()` may contain embedded nul
-  // characters, but the returned buffer may or may not be nul-terminated;
-  // therefore, do not pass `data()` to a routine that expects a nul-terminated
+  // characters, but the returned buffer may or may not be NUL-terminated;
+  // therefore, do not pass `data()` to a routine that expects a NUL-terminated
   // std::string.
   constexpr const_pointer data() const noexcept { return ptr_; }
 
@@ -577,6 +580,7 @@ constexpr bool operator>=(string_view x, string_view y) noexcept {
 // IO Insertion Operator
 std::ostream& operator<<(std::ostream& o, string_view piece);
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #undef ABSL_INTERNAL_STRING_VIEW_MEMCMP
@@ -584,6 +588,7 @@ std::ostream& operator<<(std::ostream& o, string_view piece);
 #endif  // ABSL_USES_STD_STRING_VIEW
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // ClippedSubstr()
 //
@@ -604,6 +609,7 @@ inline string_view NullSafeStringView(const char* p) {
   return p ? string_view(p) : string_view();
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_STRINGS_STRING_VIEW_H_
diff --git a/absl/strings/strip.h b/absl/strings/strip.h
index e1341e08ea76..111872ca54ba 100644
--- a/absl/strings/strip.h
+++ b/absl/strings/strip.h
@@ -30,6 +30,7 @@
 #include "absl/strings/string_view.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // ConsumePrefix()
 //
@@ -84,6 +85,7 @@ ABSL_MUST_USE_RESULT inline absl::string_view StripSuffix(
   return str;
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_STRINGS_STRIP_H_
diff --git a/absl/strings/substitute.cc b/absl/strings/substitute.cc
index 5d28c5286cf5..5b69a3ef0031 100644
--- a/absl/strings/substitute.cc
+++ b/absl/strings/substitute.cc
@@ -23,6 +23,7 @@
 #include "absl/strings/string_view.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace substitute_internal {
 
 void SubstituteAndAppendArray(std::string* output, absl::string_view format,
@@ -166,4 +167,5 @@ Arg::Arg(Dec dec) {
 }
 
 }  // namespace substitute_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/strings/substitute.h b/absl/strings/substitute.h
index 233e9dcf9386..766aca42b313 100644
--- a/absl/strings/substitute.h
+++ b/absl/strings/substitute.h
@@ -86,6 +86,7 @@
 #include "absl/strings/strip.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace substitute_internal {
 
 // Arg
@@ -681,6 +682,7 @@ std::string Substitute(
                      "format std::string doesn't contain all of $0 through $9");
 #endif  // ABSL_BAD_CALL_IF
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_STRINGS_SUBSTITUTE_H_
diff --git a/absl/synchronization/BUILD.bazel b/absl/synchronization/BUILD.bazel
index 36dc98f39e7a..3f876b9fdc90 100644
--- a/absl/synchronization/BUILD.bazel
+++ b/absl/synchronization/BUILD.bazel
@@ -43,6 +43,7 @@ cc_library(
     deps = [
         "//absl/base",
         "//absl/base:base_internal",
+        "//absl/base:config",
         "//absl/base:core_headers",
         "//absl/base:malloc_internal",
         "//absl/base:raw_logging_internal",
diff --git a/absl/synchronization/CMakeLists.txt b/absl/synchronization/CMakeLists.txt
index 3c47a1bca58b..dfe5d05df237 100644
--- a/absl/synchronization/CMakeLists.txt
+++ b/absl/synchronization/CMakeLists.txt
@@ -26,6 +26,7 @@ absl_cc_library(
   DEPS
     absl::base
     absl::base_internal
+    absl::config
     absl::core_headers
     absl::malloc_internal
     absl::raw_logging_internal
diff --git a/absl/synchronization/barrier.cc b/absl/synchronization/barrier.cc
index c2c539ac4acf..0dfd795e7b5f 100644
--- a/absl/synchronization/barrier.cc
+++ b/absl/synchronization/barrier.cc
@@ -18,6 +18,7 @@
 #include "absl/synchronization/mutex.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // Return whether int *arg is zero.
 static bool IsZero(void *arg) {
@@ -47,4 +48,5 @@ bool Barrier::Block() {
   return this->num_to_exit_ == 0;
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/synchronization/barrier.h b/absl/synchronization/barrier.h
index cb5d821a2192..d8e754406f4b 100644
--- a/absl/synchronization/barrier.h
+++ b/absl/synchronization/barrier.h
@@ -23,6 +23,7 @@
 #include "absl/synchronization/mutex.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // Barrier
 //
@@ -73,5 +74,6 @@ class Barrier {
   int num_to_exit_ ABSL_GUARDED_BY(lock_);
 };
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 #endif  // ABSL_SYNCHRONIZATION_BARRIER_H_
diff --git a/absl/synchronization/blocking_counter.cc b/absl/synchronization/blocking_counter.cc
index 481a06b2d24f..3cea7aed2441 100644
--- a/absl/synchronization/blocking_counter.cc
+++ b/absl/synchronization/blocking_counter.cc
@@ -17,6 +17,7 @@
 #include "absl/base/internal/raw_logging.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // Return whether int *arg is zero.
 static bool IsZero(void *arg) {
@@ -52,4 +53,5 @@ void BlockingCounter::Wait() {
   // after we return from this method.
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/synchronization/blocking_counter.h b/absl/synchronization/blocking_counter.h
index 77560fc05657..1f53f9f24045 100644
--- a/absl/synchronization/blocking_counter.h
+++ b/absl/synchronization/blocking_counter.h
@@ -24,6 +24,7 @@
 #include "absl/synchronization/mutex.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // BlockingCounter
 //
@@ -92,6 +93,7 @@ class BlockingCounter {
   int num_waiting_ ABSL_GUARDED_BY(lock_);
 };
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_SYNCHRONIZATION_BLOCKING_COUNTER_H_
diff --git a/absl/synchronization/blocking_counter_test.cc b/absl/synchronization/blocking_counter_test.cc
index c63e3392578a..2926224af750 100644
--- a/absl/synchronization/blocking_counter_test.cc
+++ b/absl/synchronization/blocking_counter_test.cc
@@ -22,6 +22,7 @@
 #include "absl/time/time.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace {
 
 void PauseAndDecreaseCounter(BlockingCounter* counter, int* done) {
@@ -63,4 +64,5 @@ TEST(BlockingCounterTest, BasicFunctionality) {
 }
 
 }  // namespace
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/synchronization/internal/create_thread_identity.cc b/absl/synchronization/internal/create_thread_identity.cc
index ec49d1ca715f..fa0070a9fc99 100644
--- a/absl/synchronization/internal/create_thread_identity.cc
+++ b/absl/synchronization/internal/create_thread_identity.cc
@@ -27,6 +27,7 @@
 #include "absl/synchronization/internal/per_thread_sem.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace synchronization_internal {
 
 // ThreadIdentity storage is persistent, we maintain a free-list of previously
@@ -133,6 +134,7 @@ base_internal::ThreadIdentity* CreateThreadIdentity() {
 }
 
 }  // namespace synchronization_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_LOW_LEVEL_ALLOC_MISSING
diff --git a/absl/synchronization/internal/create_thread_identity.h b/absl/synchronization/internal/create_thread_identity.h
index 97237a6ede9a..e121f68377b1 100644
--- a/absl/synchronization/internal/create_thread_identity.h
+++ b/absl/synchronization/internal/create_thread_identity.h
@@ -29,6 +29,7 @@
 #include "absl/base/port.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace synchronization_internal {
 
 // Allocates and attaches a ThreadIdentity object for the calling thread.
@@ -53,6 +54,7 @@ inline base_internal::ThreadIdentity* GetOrCreateCurrentThreadIdentity() {
 }
 
 }  // namespace synchronization_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_SYNCHRONIZATION_INTERNAL_CREATE_THREAD_IDENTITY_H_
diff --git a/absl/synchronization/internal/graphcycles.cc b/absl/synchronization/internal/graphcycles.cc
index 0c8c75644897..6a2bcdf68175 100644
--- a/absl/synchronization/internal/graphcycles.cc
+++ b/absl/synchronization/internal/graphcycles.cc
@@ -44,6 +44,7 @@
 // Do not use STL.   This module does not use standard memory allocation.
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace synchronization_internal {
 
 namespace {
@@ -690,6 +691,7 @@ int GraphCycles::GetStackTrace(GraphId id, void*** ptr) {
 }
 
 }  // namespace synchronization_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_LOW_LEVEL_ALLOC_MISSING
diff --git a/absl/synchronization/internal/graphcycles.h b/absl/synchronization/internal/graphcycles.h
index e08dc09df278..ceba33e4de89 100644
--- a/absl/synchronization/internal/graphcycles.h
+++ b/absl/synchronization/internal/graphcycles.h
@@ -40,7 +40,10 @@
 
 #include <cstdint>
 
+#include "absl/base/config.h"
+
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace synchronization_internal {
 
 // Opaque identifier for a graph node.
@@ -132,6 +135,7 @@ class GraphCycles {
 };
 
 }  // namespace synchronization_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif
diff --git a/absl/synchronization/internal/graphcycles_test.cc b/absl/synchronization/internal/graphcycles_test.cc
index 58e8477b6d1a..74eaffe7a806 100644
--- a/absl/synchronization/internal/graphcycles_test.cc
+++ b/absl/synchronization/internal/graphcycles_test.cc
@@ -25,6 +25,7 @@
 #include "absl/base/macros.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace synchronization_internal {
 
 // We emulate a GraphCycles object with a node vector and an edge vector.
@@ -459,4 +460,5 @@ TEST_F(GraphCyclesTest, ManyEdges) {
 }
 
 }  // namespace synchronization_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/synchronization/internal/kernel_timeout.h b/absl/synchronization/internal/kernel_timeout.h
index 61c72e75d13b..d6ac5db0af10 100644
--- a/absl/synchronization/internal/kernel_timeout.h
+++ b/absl/synchronization/internal/kernel_timeout.h
@@ -34,6 +34,7 @@
 #include "absl/time/time.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace synchronization_internal {
 
 class Futex;
@@ -148,6 +149,7 @@ class KernelTimeout {
 };
 
 }  // namespace synchronization_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_SYNCHRONIZATION_INTERNAL_KERNEL_TIMEOUT_H_
diff --git a/absl/synchronization/internal/mutex_nonprod.cc b/absl/synchronization/internal/mutex_nonprod.cc
index 267deaffa356..4590b98dbbed 100644
--- a/absl/synchronization/internal/mutex_nonprod.cc
+++ b/absl/synchronization/internal/mutex_nonprod.cc
@@ -31,6 +31,7 @@
 #include "absl/time/time.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace synchronization_internal {
 
 namespace {
@@ -315,4 +316,5 @@ bool Condition::Eval() const {
 
 void RegisterSymbolizer(bool (*)(const void*, char*, int)) {}
 
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/synchronization/internal/mutex_nonprod.inc b/absl/synchronization/internal/mutex_nonprod.inc
index b8d5af79ad38..85dae0ff5f49 100644
--- a/absl/synchronization/internal/mutex_nonprod.inc
+++ b/absl/synchronization/internal/mutex_nonprod.inc
@@ -36,6 +36,7 @@
 #endif
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 class Condition;
 
 namespace synchronization_internal {
@@ -256,4 +257,5 @@ class SynchronizationStorage {
 };
 
 }  // namespace synchronization_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/synchronization/internal/per_thread_sem.cc b/absl/synchronization/internal/per_thread_sem.cc
index 2a78b20fc883..821ca9b4e9c3 100644
--- a/absl/synchronization/internal/per_thread_sem.cc
+++ b/absl/synchronization/internal/per_thread_sem.cc
@@ -25,6 +25,7 @@
 #include "absl/synchronization/internal/waiter.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace synchronization_internal {
 
 void PerThreadSem::SetThreadBlockedCounter(std::atomic<int> *counter) {
@@ -62,6 +63,7 @@ void PerThreadSem::Tick(base_internal::ThreadIdentity *identity) {
 }
 
 }  // namespace synchronization_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 extern "C" {
diff --git a/absl/synchronization/internal/per_thread_sem.h b/absl/synchronization/internal/per_thread_sem.h
index 113cdfb7dc1e..8ab439153ac1 100644
--- a/absl/synchronization/internal/per_thread_sem.h
+++ b/absl/synchronization/internal/per_thread_sem.h
@@ -32,6 +32,7 @@
 #include "absl/synchronization/internal/kernel_timeout.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 class Mutex;
 
@@ -85,6 +86,7 @@ class PerThreadSem {
 };
 
 }  // namespace synchronization_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 // In some build configurations we pass --detect-odr-violations to the
diff --git a/absl/synchronization/internal/per_thread_sem_test.cc b/absl/synchronization/internal/per_thread_sem_test.cc
index dba72390d3d0..b5a2f6d4b5cb 100644
--- a/absl/synchronization/internal/per_thread_sem_test.cc
+++ b/absl/synchronization/internal/per_thread_sem_test.cc
@@ -33,6 +33,7 @@
 // primitives which might use PerThreadSem, most notably absl::Mutex.
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace synchronization_internal {
 
 class SimpleSemaphore {
@@ -175,4 +176,5 @@ TEST_F(PerThreadSemTest, Timeouts) {
 }  // namespace
 
 }  // namespace synchronization_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/synchronization/internal/thread_pool.h b/absl/synchronization/internal/thread_pool.h
index a00f2be8e892..0cb96dacde83 100644
--- a/absl/synchronization/internal/thread_pool.h
+++ b/absl/synchronization/internal/thread_pool.h
@@ -26,6 +26,7 @@
 #include "absl/synchronization/mutex.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace synchronization_internal {
 
 // A simple ThreadPool implementation for tests.
@@ -86,6 +87,7 @@ class ThreadPool {
 };
 
 }  // namespace synchronization_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_SYNCHRONIZATION_INTERNAL_THREAD_POOL_H_
diff --git a/absl/synchronization/internal/waiter.cc b/absl/synchronization/internal/waiter.cc
index e7000d3a56e1..ddd6081ed00c 100644
--- a/absl/synchronization/internal/waiter.cc
+++ b/absl/synchronization/internal/waiter.cc
@@ -49,6 +49,7 @@
 #include "absl/synchronization/internal/kernel_timeout.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace synchronization_internal {
 
 static void MaybeBecomeIdle() {
@@ -481,4 +482,5 @@ void Waiter::InternalCondVarPoke() {
 #endif
 
 }  // namespace synchronization_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/synchronization/internal/waiter.h b/absl/synchronization/internal/waiter.h
index 9540598be5d3..5af5c282ff2e 100644
--- a/absl/synchronization/internal/waiter.h
+++ b/absl/synchronization/internal/waiter.h
@@ -62,6 +62,7 @@
 #endif
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace synchronization_internal {
 
 // Waiter is an OS-specific semaphore.
@@ -157,6 +158,7 @@ class Waiter {
 };
 
 }  // namespace synchronization_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_SYNCHRONIZATION_INTERNAL_WAITER_H_
diff --git a/absl/synchronization/mutex.cc b/absl/synchronization/mutex.cc
index 100def2dd83b..46af8a52b3fd 100644
--- a/absl/synchronization/mutex.cc
+++ b/absl/synchronization/mutex.cc
@@ -71,6 +71,7 @@ ABSL_ATTRIBUTE_WEAK void AbslInternalMutexYield() { std::this_thread::yield(); }
 }  // extern "C"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 namespace {
 
@@ -295,7 +296,7 @@ static struct SynchEvent {     // this is a trivial hash table for the events
   bool log;             // logging turned on
 
   // Constant after initialization
-  char name[1];         // actually longer---null-terminated std::string
+  char name[1];         // actually longer---NUL-terminated std::string
 } * synch_event[kNSynchEvent] ABSL_GUARDED_BY(synch_event_mu);
 
 // Ensure that the object at "addr" has a SynchEvent struct associated with it,
@@ -2720,4 +2721,5 @@ bool Condition::GuaranteedEqual(const Condition *a, const Condition *b) {
          a->arg_ == b->arg_ && a->method_ == b->method_;
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/synchronization/mutex.h b/absl/synchronization/mutex.h
index ccd94618d4a5..8c70c4ce610b 100644
--- a/absl/synchronization/mutex.h
+++ b/absl/synchronization/mutex.h
@@ -82,6 +82,7 @@
 #endif
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 class Condition;
 struct SynchWaitParams;
@@ -1000,7 +1001,7 @@ void RegisterCondVarTracer(void (*fn)(const char *msg, const void *cv));
 //
 // 'pc' is the program counter being symbolized, 'out' is the buffer to write
 // into, and 'out_size' is the size of the buffer.  This function can return
-// false if symbolizing failed, or true if a null-terminated symbol was written
+// false if symbolizing failed, or true if a NUL-terminated symbol was written
 // to 'out.'
 //
 // This has the same memory ordering concerns as RegisterMutexProfiler() above.
@@ -1039,6 +1040,7 @@ enum class OnDeadlockCycle {
 // the manner chosen here.
 void SetMutexDeadlockDetectionMode(OnDeadlockCycle mode);
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 // In some build configurations we pass --detect-odr-violations to the
diff --git a/absl/synchronization/notification.cc b/absl/synchronization/notification.cc
index 1eb7f4161905..e91b90382271 100644
--- a/absl/synchronization/notification.cc
+++ b/absl/synchronization/notification.cc
@@ -22,6 +22,7 @@
 #include "absl/time/time.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 void Notification::Notify() {
   MutexLock l(&this->mutex_);
@@ -73,4 +74,5 @@ bool Notification::WaitForNotificationWithDeadline(absl::Time deadline) const {
   return notified;
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/synchronization/notification.h b/absl/synchronization/notification.h
index 36c2ce3dcefd..9a354ca2c023 100644
--- a/absl/synchronization/notification.h
+++ b/absl/synchronization/notification.h
@@ -57,6 +57,7 @@
 #include "absl/time/time.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // -----------------------------------------------------------------------------
 // Notification
@@ -116,6 +117,7 @@ class Notification {
   std::atomic<bool> notified_yet_;  // written under mutex_
 };
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_SYNCHRONIZATION_NOTIFICATION_H_
diff --git a/absl/synchronization/notification_test.cc b/absl/synchronization/notification_test.cc
index 059d4cd2521d..100ea76f33ac 100644
--- a/absl/synchronization/notification_test.cc
+++ b/absl/synchronization/notification_test.cc
@@ -21,6 +21,7 @@
 #include "absl/synchronization/mutex.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // A thread-safe class that holds a counter.
 class ThreadSafeCounter {
@@ -128,4 +129,5 @@ TEST(NotificationTest, SanityTest) {
   BasicTests(true, &local_notification2);
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/time/civil_time.cc b/absl/time/civil_time.cc
index 7b86fa8bb28f..ada82cbc8d01 100644
--- a/absl/time/civil_time.cc
+++ b/absl/time/civil_time.cc
@@ -21,6 +21,7 @@
 #include "absl/time/time.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 namespace {
 
@@ -170,4 +171,5 @@ std::ostream& operator<<(std::ostream& os, CivilSecond s) {
 
 }  // namespace time_internal
 
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/time/civil_time.h b/absl/time/civil_time.h
index 77c3be2eba6b..bb4600443445 100644
--- a/absl/time/civil_time.h
+++ b/absl/time/civil_time.h
@@ -76,6 +76,7 @@
 #include "absl/time/internal/cctz/include/cctz/civil_time.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 namespace time_internal {
 struct second_tag : cctz::detail::second_tag {};
@@ -531,6 +532,7 @@ std::ostream& operator<<(std::ostream& os, CivilSecond s);
 
 }  // namespace time_internal
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_TIME_CIVIL_TIME_H_
diff --git a/absl/time/clock.cc b/absl/time/clock.cc
index bc6f5ccf2763..9e9a0386e52b 100644
--- a/absl/time/clock.cc
+++ b/absl/time/clock.cc
@@ -34,6 +34,7 @@
 #include "absl/base/thread_annotations.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 Time Now() {
   // TODO(bww): Get a timespec instead so we don't have to divide.
   int64_t n = absl::GetCurrentTimeNanos();
@@ -43,6 +44,7 @@ Time Now() {
   }
   return time_internal::FromUnixDuration(absl::Nanoseconds(n));
 }
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 // Decide if we should use the fast GetCurrentTimeNanos() algorithm
@@ -71,9 +73,11 @@ Time Now() {
 
 #if !ABSL_USE_CYCLECLOCK_FOR_GET_CURRENT_TIME_NANOS
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 int64_t GetCurrentTimeNanos() {
   return GET_CURRENT_TIME_NANOS_FROM_SYSTEM();
 }
+ABSL_NAMESPACE_END
 }  // namespace absl
 #else  // Use the cyclecounter-based implementation below.
 
@@ -91,6 +95,7 @@ static int64_t stats_slow_paths;
 static int64_t stats_fast_slow_paths;
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace time_internal {
 // This is a friend wrapper around UnscaledCycleClock::Now()
 // (needed to access UnscaledCycleClock).
@@ -515,10 +520,12 @@ static uint64_t UpdateLastSample(uint64_t now_cycles, uint64_t now_ns,
 
   return estimated_base_ns;
 }
+ABSL_NAMESPACE_END
 }  // namespace absl
 #endif  // ABSL_USE_CYCLECLOCK_FOR_GET_CURRENT_TIME_NANOS
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace {
 
 // Returns the maximum duration that SleepOnce() can sleep for.
@@ -546,6 +553,7 @@ void SleepOnce(absl::Duration to_sleep) {
 }
 
 }  // namespace
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 extern "C" {
diff --git a/absl/time/clock.h b/absl/time/clock.h
index bb52e4f6ca99..27764a922d5e 100644
--- a/absl/time/clock.h
+++ b/absl/time/clock.h
@@ -26,6 +26,7 @@
 #include "absl/time/time.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // Now()
 //
@@ -49,6 +50,7 @@ int64_t GetCurrentTimeNanos();
 // * Returns immediately when passed a nonpositive duration.
 void SleepFor(absl::Duration duration);
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 // -----------------------------------------------------------------------------
diff --git a/absl/time/duration.cc b/absl/time/duration.cc
index f0b4631d6fa9..b1af84061a8b 100644
--- a/absl/time/duration.cc
+++ b/absl/time/duration.cc
@@ -71,6 +71,7 @@
 #include "absl/time/time.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 namespace {
 
@@ -917,4 +918,5 @@ bool ParseFlag(const std::string& text, Duration* dst, std::string* ) {
 
 std::string UnparseFlag(Duration d) { return FormatDuration(d); }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/time/duration_test.cc b/absl/time/duration_test.cc
index 5dce9ac8a557..49ebd1182ac5 100644
--- a/absl/time/duration_test.cc
+++ b/absl/time/duration_test.cc
@@ -762,11 +762,6 @@ TEST(Duration, DivisionByZero) {
   const double dbl_inf = std::numeric_limits<double>::infinity();
   const double dbl_denorm = std::numeric_limits<double>::denorm_min();
 
-  // IEEE 754 behavior
-  double z = 0.0, two = 2.0;
-  EXPECT_TRUE(std::isinf(two / z));
-  EXPECT_TRUE(std::isnan(z / z));  // We'll return inf
-
   // Operator/(Duration, double)
   EXPECT_EQ(inf, zero / 0.0);
   EXPECT_EQ(-inf, zero / -0.0);
diff --git a/absl/time/format.cc b/absl/time/format.cc
index ebe872cf7402..5997ef0c220f 100644
--- a/absl/time/format.cc
+++ b/absl/time/format.cc
@@ -22,6 +22,7 @@
 namespace cctz = absl::time_internal::cctz;
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 extern const char RFC3339_full[] = "%Y-%m-%dT%H:%M:%E*S%Ez";
 extern const char RFC3339_sec[] =  "%Y-%m-%dT%H:%M:%S%Ez";
@@ -145,4 +146,5 @@ std::string UnparseFlag(absl::Time t) {
   return absl::FormatTime(RFC3339_full, t, absl::UTCTimeZone());
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/time/internal/get_current_time_chrono.inc b/absl/time/internal/get_current_time_chrono.inc
index 5180230dee58..5eeb6406aaf3 100644
--- a/absl/time/internal/get_current_time_chrono.inc
+++ b/absl/time/internal/get_current_time_chrono.inc
@@ -16,6 +16,7 @@
 #include <cstdint>
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace time_internal {
 
 static int64_t GetCurrentTimeNanosFromSystem() {
@@ -26,4 +27,5 @@ static int64_t GetCurrentTimeNanosFromSystem() {
 }
 
 }  // namespace time_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/time/internal/get_current_time_posix.inc b/absl/time/internal/get_current_time_posix.inc
index 65474ca6da1e..42072000ae3c 100644
--- a/absl/time/internal/get_current_time_posix.inc
+++ b/absl/time/internal/get_current_time_posix.inc
@@ -7,6 +7,7 @@
 #include "absl/base/internal/raw_logging.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace time_internal {
 
 static int64_t GetCurrentTimeNanosFromSystem() {
@@ -19,4 +20,5 @@ static int64_t GetCurrentTimeNanosFromSystem() {
 }
 
 }  // namespace time_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/time/internal/test_util.cc b/absl/time/internal/test_util.cc
index fbddbb733698..9bffe121da69 100644
--- a/absl/time/internal/test_util.cc
+++ b/absl/time/internal/test_util.cc
@@ -24,6 +24,7 @@
 namespace cctz = absl::time_internal::cctz;
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace time_internal {
 
 TimeZone LoadTimeZone(const std::string& name) {
@@ -33,9 +34,11 @@ TimeZone LoadTimeZone(const std::string& name) {
 }
 
 }  // namespace time_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace time_internal {
 namespace cctz_extension {
 namespace {
@@ -123,4 +126,5 @@ ZoneInfoSourceFactory zone_info_source_factory = TestFactory;
 
 }  // namespace cctz_extension
 }  // namespace time_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/time/internal/test_util.h b/absl/time/internal/test_util.h
index d7319ea8f5bb..5c4bf1f680ee 100644
--- a/absl/time/internal/test_util.h
+++ b/absl/time/internal/test_util.h
@@ -20,12 +20,14 @@
 #include "absl/time/time.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace time_internal {
 
 // Loads the named timezone, but dies on any failure.
 absl::TimeZone LoadTimeZone(const std::string& name);
 
 }  // namespace time_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_TIME_INTERNAL_TEST_UTIL_H_
diff --git a/absl/time/time.cc b/absl/time/time.cc
index 60382be7b801..6bb36cb3e7ca 100644
--- a/absl/time/time.cc
+++ b/absl/time/time.cc
@@ -47,6 +47,7 @@
 namespace cctz = absl::time_internal::cctz;
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 namespace {
 
@@ -494,4 +495,5 @@ struct tm ToTM(absl::Time t, absl::TimeZone tz) {
   return tm;
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/time/time.h b/absl/time/time.h
index be0648134efd..7507b0cd4080 100644
--- a/absl/time/time.h
+++ b/absl/time/time.h
@@ -89,6 +89,7 @@ struct timeval;
 #include "absl/time/internal/cctz/include/cctz/time_zone.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 class Duration;  // Defined below
 class Time;      // Defined below
@@ -1574,6 +1575,7 @@ constexpr Time FromTimeT(time_t t) {
   return time_internal::FromUnixDuration(Seconds(t));
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_TIME_TIME_H_
diff --git a/absl/types/any.h b/absl/types/any.h
index f79676949d3d..16bda79cc7f3 100644
--- a/absl/types/any.h
+++ b/absl/types/any.h
@@ -61,10 +61,12 @@
 #include <any>  // IWYU pragma: export
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 using std::any;
 using std::any_cast;
 using std::bad_any_cast;
 using std::make_any;
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #else  // ABSL_USES_STD_ANY
@@ -91,6 +93,7 @@ using std::make_any;
 #endif  // !defined(__GNUC__) || defined(__GXX_RTTI)
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 namespace any_internal {
 
@@ -534,6 +537,7 @@ T* any_cast(any* operand) noexcept {
              : nullptr;
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #undef ABSL_ANY_DETAIL_HAS_RTTI
diff --git a/absl/types/bad_any_cast.cc b/absl/types/bad_any_cast.cc
index 2a5381266452..b0592cc9bcc5 100644
--- a/absl/types/bad_any_cast.cc
+++ b/absl/types/bad_any_cast.cc
@@ -22,6 +22,7 @@
 #include "absl/base/internal/raw_logging.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 bad_any_cast::~bad_any_cast() = default;
 
@@ -39,6 +40,7 @@ void ThrowBadAnyCast() {
 }
 
 }  // namespace any_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_USES_STD_ANY
diff --git a/absl/types/bad_any_cast.h b/absl/types/bad_any_cast.h
index 6a53c0108100..114cef80cdde 100644
--- a/absl/types/bad_any_cast.h
+++ b/absl/types/bad_any_cast.h
@@ -30,12 +30,15 @@
 #include <any>
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 using std::bad_any_cast;
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #else  // ABSL_USES_STD_ANY
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // -----------------------------------------------------------------------------
 // bad_any_cast
@@ -64,6 +67,7 @@ namespace any_internal {
 [[noreturn]] void ThrowBadAnyCast();
 
 }  // namespace any_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_USES_STD_ANY
diff --git a/absl/types/bad_optional_access.cc b/absl/types/bad_optional_access.cc
index d9ec21bf42b9..26aca70d9cff 100644
--- a/absl/types/bad_optional_access.cc
+++ b/absl/types/bad_optional_access.cc
@@ -22,6 +22,7 @@
 #include "absl/base/internal/raw_logging.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 bad_optional_access::~bad_optional_access() = default;
 
@@ -41,6 +42,7 @@ void throw_bad_optional_access() {
 }
 
 }  // namespace optional_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_USES_STD_OPTIONAL
diff --git a/absl/types/bad_optional_access.h b/absl/types/bad_optional_access.h
index 32dd6a91ea65..a500286adc42 100644
--- a/absl/types/bad_optional_access.h
+++ b/absl/types/bad_optional_access.h
@@ -30,12 +30,15 @@
 #include <optional>
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 using std::bad_optional_access;
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #else  // ABSL_USES_STD_OPTIONAL
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // -----------------------------------------------------------------------------
 // bad_optional_access
@@ -67,6 +70,7 @@ namespace optional_internal {
 [[noreturn]] void throw_bad_optional_access();
 
 }  // namespace optional_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_USES_STD_OPTIONAL
diff --git a/absl/types/bad_variant_access.cc b/absl/types/bad_variant_access.cc
index dbaea9e9d1db..3dc88cc09f23 100644
--- a/absl/types/bad_variant_access.cc
+++ b/absl/types/bad_variant_access.cc
@@ -23,6 +23,7 @@
 #include "absl/base/internal/raw_logging.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 //////////////////////////
 // [variant.bad.access] //
@@ -57,6 +58,7 @@ void Rethrow() {
 }
 
 }  // namespace variant_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_USES_STD_VARIANT
diff --git a/absl/types/bad_variant_access.h b/absl/types/bad_variant_access.h
index 6935d01b99f7..095969f91eee 100644
--- a/absl/types/bad_variant_access.h
+++ b/absl/types/bad_variant_access.h
@@ -30,12 +30,15 @@
 #include <variant>
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 using std::bad_variant_access;
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #else  // ABSL_USES_STD_VARIANT
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // -----------------------------------------------------------------------------
 // bad_variant_access
@@ -71,6 +74,7 @@ namespace variant_internal {
 [[noreturn]] void Rethrow();
 
 }  // namespace variant_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_USES_STD_VARIANT
diff --git a/absl/types/compare.h b/absl/types/compare.h
index a213e0b0b682..c29ced5273a2 100644
--- a/absl/types/compare.h
+++ b/absl/types/compare.h
@@ -39,6 +39,7 @@
 #include "absl/meta/type_traits.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace compare_internal {
 
 using value_type = int8_t;
@@ -551,6 +552,7 @@ constexpr absl::weak_ordering do_three_way_comparison(const Compare &compare,
 }
 
 }  // namespace compare_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_TYPES_COMPARE_H_
diff --git a/absl/types/compare_test.cc b/absl/types/compare_test.cc
index ee396fc54d7c..955844b529bb 100644
--- a/absl/types/compare_test.cc
+++ b/absl/types/compare_test.cc
@@ -18,6 +18,7 @@
 #include "absl/base/casts.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace {
 
 // This is necessary to avoid a bunch of lint warnings suggesting that we use
@@ -334,4 +335,5 @@ TEST(Compare, StaticAsserts) {
 #endif  // __cpp_inline_variables
 
 }  // namespace
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/types/internal/conformance_aliases.h b/absl/types/internal/conformance_aliases.h
index 7d5d0e092a47..0cc6884e309e 100644
--- a/absl/types/internal/conformance_aliases.h
+++ b/absl/types/internal/conformance_aliases.h
@@ -26,6 +26,7 @@
 #include "absl/types/internal/conformance_profile.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace types_internal {
 
 // Creates both a Profile and a corresponding Archetype with root name "name".
@@ -438,6 +439,7 @@ using ExpandSupportedProfiles = Receiver<
 // (potentially) non-noexcept moves.
 
 }  // namespace types_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #undef ABSL_INTERNAL_PROFILE_AND_ARCHETYPE_ALIAS
diff --git a/absl/types/internal/conformance_archetype.h b/absl/types/internal/conformance_archetype.h
index 97ee726528aa..2349e0f72635 100644
--- a/absl/types/internal/conformance_archetype.h
+++ b/absl/types/internal/conformance_archetype.h
@@ -43,6 +43,7 @@
 #include "absl/types/internal/conformance_profile.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace types_internal {
 
 // A minimum-conforming implementation of a type with properties specified in
@@ -961,6 +962,7 @@ struct EnabledHash {
 };
 
 }  // namespace types_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 namespace std {
diff --git a/absl/types/internal/conformance_profile.h b/absl/types/internal/conformance_profile.h
index dce3bbee6908..e62004fdf271 100644
--- a/absl/types/internal/conformance_profile.h
+++ b/absl/types/internal/conformance_profile.h
@@ -44,6 +44,7 @@
 // TODO(calabrese) Add support for extending profiles.
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace types_internal {
 
 template <class T, class /*Enabler*/ = void>
@@ -369,6 +370,7 @@ template <class T>
 struct IsProfile : IsProfileImpl<T>::type {};
 
 }  // namespace types_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_TYPES_INTERNAL_CONFORMANCE_PROFILE_H_
diff --git a/absl/types/internal/optional.h b/absl/types/internal/optional.h
index d41ccc75f6f6..92932b6001b3 100644
--- a/absl/types/internal/optional.h
+++ b/absl/types/internal/optional.h
@@ -54,6 +54,7 @@
 #endif
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // Forward declaration
 template <typename T>
@@ -387,6 +388,7 @@ struct optional_hash_base<T, decltype(std::hash<absl::remove_const_t<T> >()(
 };
 
 }  // namespace optional_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #undef ABSL_OPTIONAL_USE_INHERITING_CONSTRUCTORS
diff --git a/absl/types/internal/span.h b/absl/types/internal/span.h
index d203aad59165..112612f4bdae 100644
--- a/absl/types/internal/span.h
+++ b/absl/types/internal/span.h
@@ -26,6 +26,7 @@
 #include "absl/meta/type_traits.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 namespace span_internal {
 // A constexpr min function
@@ -121,6 +122,7 @@ template <typename From, typename To>
 using EnableIfConvertibleTo =
     typename std::enable_if<IsConvertible<From, To>::value>::type;
 }  // namespace span_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_TYPES_INTERNAL_SPAN_H_
diff --git a/absl/types/internal/variant.h b/absl/types/internal/variant.h
index 58b385921f59..71bd3adfc6ef 100644
--- a/absl/types/internal/variant.h
+++ b/absl/types/internal/variant.h
@@ -40,6 +40,7 @@
 #if !defined(ABSL_USES_STD_VARIANT)
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 template <class... Types>
 class variant;
@@ -1638,6 +1639,7 @@ struct VariantHashBase<Variant,
 };
 
 }  // namespace variant_internal
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // !defined(ABSL_USES_STD_VARIANT)
diff --git a/absl/types/optional.h b/absl/types/optional.h
index 14032598d9b0..2025e29f86a9 100644
--- a/absl/types/optional.h
+++ b/absl/types/optional.h
@@ -43,11 +43,13 @@
 #include <optional>  // IWYU pragma: export
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 using std::bad_optional_access;
 using std::optional;
 using std::make_optional;
 using std::nullopt_t;
 using std::nullopt;
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #else  // ABSL_USES_STD_OPTIONAL
@@ -65,6 +67,7 @@ using std::nullopt;
 #include "absl/types/internal/optional.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // nullopt_t
 //
@@ -754,6 +757,7 @@ constexpr auto operator>=(const U& v, const optional<T>& x)
   return static_cast<bool>(x) ? static_cast<bool>(v >= *x) : true;
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 namespace std {
diff --git a/absl/types/optional_exception_safety_test.cc b/absl/types/optional_exception_safety_test.cc
index 0f7fae6cb4cf..8e5fe851dbb7 100644
--- a/absl/types/optional_exception_safety_test.cc
+++ b/absl/types/optional_exception_safety_test.cc
@@ -24,6 +24,7 @@
 #include "absl/base/internal/exception_safety_testing.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 namespace {
 
@@ -285,6 +286,7 @@ TEST(OptionalExceptionSafety, NothrowMoveAssign) {
 
 }  // namespace
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // #if !defined(ABSL_USES_STD_OPTIONAL) && defined(ABSL_HAVE_EXCEPTIONS)
diff --git a/absl/types/span.h b/absl/types/span.h
index b007fc1fd3df..3283145a56b4 100644
--- a/absl/types/span.h
+++ b/absl/types/span.h
@@ -71,6 +71,7 @@
 #include "absl/types/internal/span.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 //------------------------------------------------------------------------------
 // Span
@@ -707,5 +708,6 @@ template <int&... ExplicitArgumentBarrier, typename T, size_t N>
 constexpr Span<const T> MakeConstSpan(const T (&array)[N]) noexcept {
   return Span<const T>(array, N);
 }
+ABSL_NAMESPACE_END
 }  // namespace absl
 #endif  // ABSL_TYPES_SPAN_H_
diff --git a/absl/types/variant.h b/absl/types/variant.h
index f3558703a82a..776d19a1c524 100644
--- a/absl/types/variant.h
+++ b/absl/types/variant.h
@@ -50,6 +50,7 @@
 #include <variant>  // IWYU pragma: export
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 using std::bad_variant_access;
 using std::get;
 using std::get_if;
@@ -62,6 +63,7 @@ using std::variant_npos;
 using std::variant_size;
 using std::variant_size_v;
 using std::visit;
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #else  // ABSL_USES_STD_VARIANT
@@ -77,6 +79,7 @@ using std::visit;
 #include "absl/types/internal/variant.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // -----------------------------------------------------------------------------
 // absl::variant
@@ -795,6 +798,7 @@ operator>=(const variant<Types...>& a, const variant<Types...>& b) {
                    a.index());
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 namespace std {
@@ -815,6 +819,7 @@ struct hash<absl::variant<T...>>
 #endif  // ABSL_USES_STD_VARIANT
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace variant_internal {
 
 // Helper visitor for converting a variant<Ts...>` into another type (mostly
@@ -850,6 +855,7 @@ To ConvertVariantTo(Variant&& variant) {
                      std::forward<Variant>(variant));
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_TYPES_VARIANT_H_
diff --git a/absl/types/variant_benchmark.cc b/absl/types/variant_benchmark.cc
index a5f521644142..350b17536413 100644
--- a/absl/types/variant_benchmark.cc
+++ b/absl/types/variant_benchmark.cc
@@ -28,6 +28,7 @@
 #include "absl/utility/utility.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace {
 
 template <std::size_t I>
@@ -217,4 +218,5 @@ BENCHMARK_TEMPLATE(BM_RedundantVisit, 4, 2)
     ->DenseRange(0, integral_pow(4, 2) - 1);
 
 }  // namespace
+ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/types/variant_exception_safety_test.cc b/absl/types/variant_exception_safety_test.cc
index b486a71e5b72..439c6e1df367 100644
--- a/absl/types/variant_exception_safety_test.cc
+++ b/absl/types/variant_exception_safety_test.cc
@@ -34,6 +34,7 @@
 #if !defined(ABSL_INTERNAL_MSVC_2017_DBG_MODE)
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace {
 
 using ::testing::MakeExceptionSafetyTester;
@@ -523,6 +524,7 @@ TEST(VariantExceptionSafetyTest, Swap) {
 }
 
 }  // namespace
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // !defined(ABSL_INTERNAL_MSVC_2017_DBG_MODE)
diff --git a/absl/types/variant_test.cc b/absl/types/variant_test.cc
index 2913775a4e59..96393333b868 100644
--- a/absl/types/variant_test.cc
+++ b/absl/types/variant_test.cc
@@ -70,6 +70,7 @@ struct hash<Hashable> {
 struct NonHashable {};
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace {
 
 using ::testing::DoubleEq;
@@ -2709,6 +2710,7 @@ TEST(VariantTest, MoveCtorBug) {
 }
 
 }  // namespace
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // #if !defined(ABSL_USES_STD_VARIANT)
diff --git a/absl/utility/utility.h b/absl/utility/utility.h
index 5a98c2c39c41..e6647c7b2e61 100644
--- a/absl/utility/utility.h
+++ b/absl/utility/utility.h
@@ -51,6 +51,7 @@
 #include "absl/meta/type_traits.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 
 // integer_sequence
 //
@@ -343,6 +344,7 @@ constexpr T make_from_tuple(Tuple&& tup) {
           std::tuple_size<absl::decay_t<Tuple>>::value>{});
 }
 
+ABSL_NAMESPACE_END
 }  // namespace absl
 
 #endif  // ABSL_UTILITY_UTILITY_H_
author	Abseil Team <absl-team@google.com>	2019-12-12T18·36-0800
committer	Matt Calabrese <calabrese@x.team>	2019-12-12T20·37-0500
commit	12bc53e0318d80569270a5b26ccbc62b52022b89 (patch)
tree	703f7dd5e7fdea7db3eefe317b10b1f67ddd8212 /absl
parent	1e39f8626a4dadec1f56920b999dd4c3cfae333e (diff)