Export of internal Abseil changes

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53550735f5a943dfb99225e7c53f211c2d6e7951 by Gennadiy Rozental <rogeeff@google.com>:

Import of CCTZ from GitHub.

PiperOrigin-RevId: 309333648

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847bbf8a1d9cd322ec058c6f932d1f687fd3d331 by Gennadiy Rozental <rogeeff@google.com>:

Make Validation interfaces private in CommandLineFlag.

Calls are rewired via private interface access struct.

PiperOrigin-RevId: 309323013

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a600fc5051e0a0af50a7850450fd3ed1aef3f316 by Matthew Brown <matthewbr@google.com>:

Internal Change.

PiperOrigin-RevId: 309292207

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937d00ce3cf62c5f23f59b5377471fd01d6bfbc7 by Gennadiy Rozental <rogeeff@google.com>:

Make TypeId interface private in CommandLineFlag.

We also rewire the SaveState via the new PrivateHandleInterface trampoline class. This class will be the only way to access private methods of class CommandLineFlag.

PiperOrigin-RevId: 309282547

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796c4bd35073b6a8337762bdb13603dae12a4df1 by Derek Mauro <dmauro@google.com>:

Cleanup uses of kLinkerInitialized

PiperOrigin-RevId: 309274734

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c831446c52d9ef4bdcb1ea369840904620abc4b9 by Gennadiy Rozental <rogeeff@google.com>:

Eliminate the interface IsModified of CommndLineFlag.

PiperOrigin-RevId: 309256248

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a1db59d7f7aa39cb0a37dbf80f8c04e371da8465 by Gennadiy Rozental <rogeeff@google.com>:

Avoid default value generator if default value expression is constexpr.

If possible, we detect constexpr-ness of default value expression and avoid storing default value generator in side of flag and instead set the flag's value to the value of that expression at const initialization time of flag objects.

At the moment we only do this for flags of (all) integral, float and double value types

PiperOrigin-RevId: 309110630

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ae3b4a139aacd8fc165c9acd2a3cbae1f9e26af4 by Gennadiy Rozental <rogeeff@google.com>:

Make SaveState a private method of the CommandLineFlag and make it only accessible from FlagSaverImpl. There is no other call sites for this call.

PiperOrigin-RevId: 309073989

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cbc24b4dcc166dd6b0208e9d7620484eaaaa7ee0 by Abseil Team <absl-team@google.com>:

Eliminate the interface IsModified of CommndLineFlag.

PiperOrigin-RevId: 309064639

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08e79645a89d71785c5381cea9c413357db9824a by Gennadiy Rozental <rogeeff@google.com>:

Eliminate the interface IsModified of CommndLineFlag.

PiperOrigin-RevId: 309054430

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4a6c70233c60dc8c39b7fa9beb5fa687c215261f by Gennadiy Rozental <rogeeff@google.com>:

Internal change

PiperOrigin-RevId: 308900784

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13160efdf7710f142778d5a1e4c85aa309f019b6 by Abseil Team <absl-team@google.com>:

Provide definitions of static member variables -- improved C++11 support.

PiperOrigin-RevId: 308900290

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0343b8228657b9b313afdfe88c4a7b2137d56db4 by Gennadiy Rozental <rogeeff@google.com>:

Rename method Get<T> to TryGet<T> per approved spec before making interface public.

PiperOrigin-RevId: 308889113

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7b84e27fb857fc1296a05504970f506d47d2f2c1 by Derek Mauro <dmauro@google.com>:

Remove node_hash_* methods that were deprecated on release

PiperOrigin-RevId: 308837933

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599d44ee72c02b6bb6e1c1a1db72873841441416 by Gennadiy Rozental <rogeeff@google.com>:

Eliminate CommandLineFlag::Typename interface per approved spec before making CommandLineFlag public.

PiperOrigin-RevId: 308814376
GitOrigin-RevId: 53550735f5a943dfb99225e7c53f211c2d6e7951
Change-Id: Iae52c65b7322152c7e58f222d60eb5a21699a2cb

1 files changed, 71 insertions, 28 deletions

diff --git a/absl/flags/internal/flag.h b/absl/flags/internal/flag.h
index 6da25aa9454a..b2208824508d 100644
--- a/absl/flags/internal/flag.h
+++ b/absl/flags/internal/flag.h
@@ -206,12 +206,72 @@ using FlagDfltGenFunc = void (*)(void*);
 union FlagDefaultSrc {
   constexpr explicit FlagDefaultSrc(FlagDfltGenFunc gen_func_arg)
       : gen_func(gen_func_arg) {}
+  template <typename T>
+  constexpr explicit FlagDefaultSrc(T one_word_value)
+      : one_word(static_cast<int64_t>(one_word_value)) {}
+  constexpr explicit FlagDefaultSrc(float f) : float_value(f) {}
+  constexpr explicit FlagDefaultSrc(double d) : double_value(d) {}
 
   void* dynamic_value;
   FlagDfltGenFunc gen_func;
+  int64_t one_word;
+  float float_value;
+  double double_value;
+};
+
+enum class FlagDefaultKind : uint8_t {
+  kDynamicValue = 0,
+  kGenFunc = 1,
+  kOneWord = 2,
+  kFloat = 3,
+  kDouble = 4
+};
+
+struct FlagDefaultArg {
+  FlagDefaultSrc source;
+  FlagDefaultKind kind;
 };
 
-enum class FlagDefaultKind : uint8_t { kDynamicValue = 0, kGenFunc = 1 };
+// This struct and corresponding overload to InitDefaultValue are used to
+// facilitate usage of {} as default value in ABSL_FLAG macro.
+// TODO(rogeeff): Fix handling types with explicit constructors.
+struct EmptyBraces {};
+
+template <typename T>
+constexpr T InitDefaultValue(T t) {
+  return t;
+}
+
+template <typename T>
+constexpr T InitDefaultValue(EmptyBraces) {
+  return T{};
+}
+
+template <typename ValueT, typename GenT,
+          typename std::enable_if<std::is_integral<ValueT>::value, int>::type =
+              (GenT{}, 0)>
+constexpr FlagDefaultArg DefaultArg(int) {
+  return {FlagDefaultSrc(GenT{}.value), FlagDefaultKind::kOneWord};
+}
+
+template <typename ValueT, typename GenT,
+          typename std::enable_if<std::is_same<ValueT, float>::value,
+                                  int>::type = (GenT{}, 0)>
+constexpr FlagDefaultArg DefaultArg(int) {
+  return {FlagDefaultSrc(GenT{}.value), FlagDefaultKind::kFloat};
+}
+
+template <typename ValueT, typename GenT,
+          typename std::enable_if<std::is_same<ValueT, double>::value,
+                                  int>::type = (GenT{}, 0)>
+constexpr FlagDefaultArg DefaultArg(int) {
+  return {FlagDefaultSrc(GenT{}.value), FlagDefaultKind::kDouble};
+}
+
+template <typename ValueT, typename GenT>
+constexpr FlagDefaultArg DefaultArg(char) {
+  return {FlagDefaultSrc(&GenT::Gen), FlagDefaultKind::kGenFunc};
+}
 
 ///////////////////////////////////////////////////////////////////////////////
 // Flag current value auxiliary structs.
@@ -356,19 +416,19 @@ class FlagImpl final : public flags_internal::CommandLineFlag {
  public:
   constexpr FlagImpl(const char* name, const char* filename, FlagOpFn op,
                      FlagHelpArg help, FlagValueStorageKind value_kind,
-                     FlagDfltGenFunc default_value_gen)
+                     FlagDefaultArg default_arg)
       : name_(name),
         filename_(filename),
         op_(op),
         help_(help.source),
         help_source_kind_(static_cast<uint8_t>(help.kind)),
         value_storage_kind_(static_cast<uint8_t>(value_kind)),
-        def_kind_(static_cast<uint8_t>(FlagDefaultKind::kGenFunc)),
+        def_kind_(static_cast<uint8_t>(default_arg.kind)),
         modified_(false),
         on_command_line_(false),
         counter_(0),
         callback_(nullptr),
-        default_value_(default_value_gen),
+        default_value_(default_arg.source),
         data_guard_{} {}
 
   // Constant access methods
@@ -444,10 +504,8 @@ class FlagImpl final : public flags_internal::CommandLineFlag {
   // CommandLineFlag interface implementation
   absl::string_view Name() const override;
   std::string Filename() const override;
-  absl::string_view Typename() const override;
   std::string Help() const override;
   FlagFastTypeId TypeId() const override;
-  bool IsModified() const override ABSL_LOCKS_EXCLUDED(*DataGuard());
   bool IsSpecifiedOnCommandLine() const override
       ABSL_LOCKS_EXCLUDED(*DataGuard());
   std::string DefaultValue() const override ABSL_LOCKS_EXCLUDED(*DataGuard());
@@ -492,9 +550,10 @@ class FlagImpl final : public flags_internal::CommandLineFlag {
 
   // Mutable flag's state (guarded by `data_guard_`).
 
-  // If def_kind_ == kDynamicValue, default_value_ holds a dynamically allocated
-  // value.
-  uint8_t def_kind_ : 1 ABSL_GUARDED_BY(*DataGuard());
+  // def_kind_ is not guard by DataGuard() since it is accessed in Init without
+  // locks. If necessary we can decrease number of bits used to 2 by folding
+  // one_word storage cases.
+  uint8_t def_kind_ : 3;
   // Has this flag's value been modified?
   bool modified_ : 1 ABSL_GUARDED_BY(*DataGuard());
   // Has this flag been specified on command line.
@@ -530,10 +589,10 @@ class FlagImpl final : public flags_internal::CommandLineFlag {
 template <typename T>
 class Flag {
  public:
-  constexpr Flag(const char* name, const char* filename, const FlagHelpArg help,
-                 const FlagDfltGenFunc default_value_gen)
+  constexpr Flag(const char* name, const char* filename, FlagHelpArg help,
+                 const FlagDefaultArg default_arg)
       : impl_(name, filename, &FlagOps<T>, help,
-              flags_internal::StorageKind<T>(), default_value_gen),
+              flags_internal::StorageKind<T>(), default_arg),
         value_() {}
 
   T Get() const {
@@ -560,9 +619,7 @@ class Flag {
   // CommandLineFlag interface
   absl::string_view Name() const { return impl_.Name(); }
   std::string Filename() const { return impl_.Filename(); }
-  absl::string_view Typename() const { return ""; }
   std::string Help() const { return impl_.Help(); }
-  bool IsModified() const { return impl_.IsModified(); }
   bool IsSpecifiedOnCommandLine() const {
     return impl_.IsSpecifiedOnCommandLine();
   }
@@ -662,20 +719,6 @@ class FlagRegistrar {
   Flag<T>* flag_;  // Flag being registered (not owned).
 };
 
-// This struct and corresponding overload to MakeDefaultValue are used to
-// facilitate usage of {} as default value in ABSL_FLAG macro.
-struct EmptyBraces {};
-
-template <typename T>
-void MakeFromDefaultValue(void* dst, T t) {
-  new (dst) T(std::move(t));
-}
-
-template <typename T>
-void MakeFromDefaultValue(void* dst, EmptyBraces) {
-  new (dst) T{};
-}
-
 }  // namespace flags_internal
 ABSL_NAMESPACE_END
 }  // namespace absl