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

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_

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_

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_

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

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_

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

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

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_

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_