Export of internal Abseil changes

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e1d2e93a3328d9e4362c5510e81bd15ddd0dcf00 by Derek Mauro <dmauro@google.com>:

ROLLBACK: Use auto-detected sanitizer attributes for ASAN, MSAN, and TSAN builds

PiperOrigin-RevId: 323612219

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6fe0914715bcb680ac1dc533aae3461e2ca1ad50 by Derek Mauro <dmauro@google.com>:

Use auto-detected sanitizer attributes for ASAN, MSAN, and TSAN builds

PiperOrigin-RevId: 323597765

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9ad74e277348585f06a511aac31fff917a89a5d7 by Mark Barolak <mbar@google.com>:

Import of CCTZ from GitHub.

PiperOrigin-RevId: 323594550

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9e77ccb5adf7e9867cfa254105930f8fed19699d by Evan Brown <ezb@google.com>:

Remove an unnecessary nullptr check in Cord::PrependTree().

We already check for nullptr at all callsites.

PiperOrigin-RevId: 323583641

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31ab2355c1b91e474b67ff88b8597ad99f346511 by Gennadiy Rozental <rogeeff@google.com>:

Avoid memory allocations while registering retired flags.

PiperOrigin-RevId: 323523011

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33435e9b97b31763a80d3e41b5ab2459e862e99a by Jorg Brown <jorg@google.com>:

Allow ABSL_PREDICT_FALSE to be used with a type that's explicitly convertible to bool.

So far ABSL_PREDICT_TRUE could be used with these, but not ABSL_PREDICT_FALSE.

PiperOrigin-RevId: 323514860
GitOrigin-RevId: e1d2e93a3328d9e4362c5510e81bd15ddd0dcf00
Change-Id: Iee5b030d9aec1ae2c0fe8997763cee7bd84b4090

4 files changed, 23 insertions, 24 deletions

diff --git a/absl/flags/flag.h b/absl/flags/flag.h
index 90dc2894..e1707252 100644
--- a/absl/flags/flag.h
+++ b/absl/flags/flag.h
@@ -379,11 +379,10 @@ ABSL_NAMESPACE_END
 //
 // `default_value` is only used as a double check on the type. `explanation` is
 // unused.
-// TODO(rogeeff): Return an anonymous struct instead of bool, and place it into
-// the unnamed namespace.
-#define ABSL_RETIRED_FLAG(type, flagname, default_value, explanation) \
-  ABSL_ATTRIBUTE_UNUSED static const bool ignored_##flagname =        \
-      ([] { return type(default_value); },                            \
-       absl::flags_internal::RetiredFlag<type>(#flagname))
+// TODO(rogeeff): replace RETIRED_FLAGS with FLAGS once forward declarations of
+// retired flags are cleaned up.
+#define ABSL_RETIRED_FLAG(type, name, default_value, explanation)            \
+  ABSL_ATTRIBUTE_UNUSED static const absl::flags_internal::RetiredFlag<type> \
+      RETIRED_FLAGS_##name(#name)
 
 #endif  // ABSL_FLAGS_FLAG_H_
diff --git a/absl/flags/flag_test_defs.cc b/absl/flags/flag_test_defs.cc
index 49f91dee..3366c580 100644
--- a/absl/flags/flag_test_defs.cc
+++ b/absl/flags/flag_test_defs.cc
@@ -20,5 +20,3 @@
 
 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/registry.h b/absl/flags/internal/registry.h
index 6f5006a0..5f85ded5 100644
--- a/absl/flags/internal/registry.h
+++ b/absl/flags/internal/registry.h
@@ -74,13 +74,22 @@ bool RegisterCommandLineFlag(CommandLineFlag&);
 //
 
 // Retire flag with name "name" and type indicated by ops.
-bool Retire(const char* name, FlagFastTypeId type_id);
+void Retire(const char* name, FlagFastTypeId type_id, char* buf);
+
+constexpr size_t kRetiredFlagObjSize = 3 * sizeof(void*);
+constexpr size_t kRetiredFlagObjAlignment = alignof(void*);
 
 // Registered a retired flag with name 'flag_name' and type 'T'.
 template <typename T>
-inline bool RetiredFlag(const char* flag_name) {
-  return flags_internal::Retire(flag_name, base_internal::FastTypeId<T>());
-}
+class RetiredFlag {
+ public:
+  explicit RetiredFlag(const char* flag_name) {
+    flags_internal::Retire(flag_name, base_internal::FastTypeId<T>(), buf_);
+  }
+
+ private:
+  alignas(kRetiredFlagObjAlignment) char buf_[kRetiredFlagObjSize];
+};
 
 }  // namespace flags_internal
 ABSL_NAMESPACE_END
diff --git a/absl/flags/reflection.cc b/absl/flags/reflection.cc
index 1b025835..e4145b34 100644
--- a/absl/flags/reflection.cc
+++ b/absl/flags/reflection.cc
@@ -99,8 +99,6 @@ class FlagRegistryLock {
   FlagRegistry& fr_;
 };
 
-void DestroyRetiredFlag(CommandLineFlag& flag);
-
 }  // namespace
 
 void FlagRegistry::RegisterFlag(CommandLineFlag& flag) {
@@ -125,8 +123,6 @@ void FlagRegistry::RegisterFlag(CommandLineFlag& flag) {
                        old_flag.Filename(), "' and '", flag.Filename(), "'."),
           true);
     } else if (old_flag.IsRetired()) {
-      // Retired flag can just be deleted.
-      DestroyRetiredFlag(flag);
       return;
     } else if (old_flag.Filename() != flag.Filename()) {
       flags_internal::ReportUsageError(
@@ -241,17 +237,14 @@ class RetiredFlagObj final : public CommandLineFlag {
   const FlagFastTypeId type_id_;
 };
 
-void DestroyRetiredFlag(CommandLineFlag& flag) {
-  assert(flag.IsRetired());
-  delete static_cast<RetiredFlagObj*>(&flag);
-}
-
 }  // namespace
 
-bool Retire(const char* name, FlagFastTypeId type_id) {
-  auto* flag = new flags_internal::RetiredFlagObj(name, type_id);
+void Retire(const char* name, FlagFastTypeId type_id, char* buf) {
+  static_assert(sizeof(RetiredFlagObj) == kRetiredFlagObjSize, "");
+  static_assert(alignof(RetiredFlagObj) == kRetiredFlagObjAlignment, "");
+  auto* flag = ::new (static_cast<void*>(buf))
+      flags_internal::RetiredFlagObj(name, type_id);
   FlagRegistry::GlobalRegistry().RegisterFlag(*flag);
-  return true;
 }
 
 // --------------------------------------------------------------------