create

Pods/abseil/absl/flags/commandlineflag.cc

@@ -0,0 +1,34 @@
+//
+// Copyright 2020 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/flags/commandlineflag.h"
+
+#include <string>
+
+#include "absl/base/config.h"
+#include "absl/flags/internal/commandlineflag.h"
+#include "absl/strings/string_view.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+bool CommandLineFlag::IsRetired() const { return false; }
+bool CommandLineFlag::ParseFrom(absl::string_view value, std::string* error) {
+  return ParseFrom(value, flags_internal::SET_FLAGS_VALUE,
+                   flags_internal::kProgrammaticChange, *error);
+}
+
+ABSL_NAMESPACE_END
+}  // namespace absl

Pods/abseil/absl/flags/commandlineflag.h

@@ -0,0 +1,200 @@
+//
+// Copyright 2020 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// -----------------------------------------------------------------------------
+// File: commandlineflag.h
+// -----------------------------------------------------------------------------
+//
+// This header file defines the `CommandLineFlag`, which acts as a type-erased
+// handle for accessing metadata about the Abseil Flag in question.
+//
+// Because an actual Abseil flag is of an unspecified type, you should not
+// manipulate or interact directly with objects of that type. Instead, use the
+// CommandLineFlag type as an intermediary.
+#ifndef ABSL_FLAGS_COMMANDLINEFLAG_H_
+#define ABSL_FLAGS_COMMANDLINEFLAG_H_
+
+#include <memory>
+#include <string>
+
+#include "absl/base/config.h"
+#include "absl/base/internal/fast_type_id.h"
+#include "absl/flags/internal/commandlineflag.h"
+#include "absl/strings/string_view.h"
+#include "absl/types/optional.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace flags_internal {
+class PrivateHandleAccessor;
+}  // namespace flags_internal
+
+// CommandLineFlag
+//
+// This type acts as a type-erased handle for an instance of an Abseil Flag and
+// holds reflection information pertaining to that flag. Use CommandLineFlag to
+// access a flag's name, location, help string etc.
+//
+// To obtain an absl::CommandLineFlag, invoke `absl::FindCommandLineFlag()`
+// passing it the flag name string.
+//
+// Example:
+//
+//   // Obtain reflection handle for a flag named "flagname".
+//   const absl::CommandLineFlag* my_flag_data =
+//        absl::FindCommandLineFlag("flagname");
+//
+//   // Now you can get flag info from that reflection handle.
+//   std::string flag_location = my_flag_data->Filename();
+//   ...
+class CommandLineFlag {
+ public:
+  constexpr CommandLineFlag() = default;
+
+  // Not copyable/assignable.
+  CommandLineFlag(const CommandLineFlag&) = delete;
+  CommandLineFlag& operator=(const CommandLineFlag&) = delete;
+
+  // absl::CommandLineFlag::IsOfType()
+  //
+  // Return true iff flag has type T.
+  template <typename T>
+  inline bool IsOfType() const {
+    return TypeId() == base_internal::FastTypeId<T>();
+  }
+
+  // absl::CommandLineFlag::TryGet()
+  //
+  // Attempts to retrieve the flag value. Returns value on success,
+  // absl::nullopt otherwise.
+  template <typename T>
+  absl::optional<T> TryGet() const {
+    if (IsRetired() || !IsOfType<T>()) {
+      return absl::nullopt;
+    }
+
+    // Implementation notes:
+    //
+    // We are wrapping a union around the value of `T` to serve three purposes:
+    //
+    //  1. `U.value` has correct size and alignment for a value of type `T`
+    //  2. The `U.value` constructor is not invoked since U's constructor does
+    //     not do it explicitly.
+    //  3. The `U.value` destructor is invoked since U's destructor does it
+    //     explicitly. This makes `U` a kind of RAII wrapper around non default
+    //     constructible value of T, which is destructed when we leave the
+    //     scope. We do need to destroy U.value, which is constructed by
+    //     CommandLineFlag::Read even though we left it in a moved-from state
+    //     after std::move.
+    //
+    // All of this serves to avoid requiring `T` being default constructible.
+    union U {
+      T value;
+      U() {}
+      ~U() { value.~T(); }
+    };
+    U u;
+
+    Read(&u.value);
+    // allow retired flags to be "read", so we can report invalid access.
+    if (IsRetired()) {
+      return absl::nullopt;
+    }
+    return std::move(u.value);
+  }
+
+  // absl::CommandLineFlag::Name()
+  //
+  // Returns name of this flag.
+  virtual absl::string_view Name() const = 0;
+
+  // absl::CommandLineFlag::Filename()
+  //
+  // Returns name of the file where this flag is defined.
+  virtual std::string Filename() const = 0;
+
+  // absl::CommandLineFlag::Help()
+  //
+  // Returns help message associated with this flag.
+  virtual std::string Help() const = 0;
+
+  // absl::CommandLineFlag::IsRetired()
+  //
+  // Returns true iff this object corresponds to retired flag.
+  virtual bool IsRetired() const;
+
+  // absl::CommandLineFlag::DefaultValue()
+  //
+  // Returns the default value for this flag.
+  virtual std::string DefaultValue() const = 0;
+
+  // absl::CommandLineFlag::CurrentValue()
+  //
+  // Returns the current value for this flag.
+  virtual std::string CurrentValue() const = 0;
+
+  // absl::CommandLineFlag::ParseFrom()
+  //
+  // Sets the value of the flag based on specified string `value`. If the flag
+  // was successfully set to new value, it returns true. Otherwise, sets `error`
+  // to indicate the error, leaves the flag unchanged, and returns false.
+  bool ParseFrom(absl::string_view value, std::string* error);
+
+ protected:
+  ~CommandLineFlag() = default;
+
+ private:
+  friend class flags_internal::PrivateHandleAccessor;
+
+  // Sets the value of the flag based on specified string `value`. If the flag
+  // was successfully set to new value, it returns true. Otherwise, sets `error`
+  // to indicate the error, leaves the flag unchanged, and returns false. There
+  // are three ways to set the flag's value:
+  //  * Update the current flag value
+  //  * Update the flag's default value
+  //  * Update the current flag value if it was never set before
+  // The mode is selected based on `set_mode` parameter.
+  virtual bool ParseFrom(absl::string_view value,
+                         flags_internal::FlagSettingMode set_mode,
+                         flags_internal::ValueSource source,
+                         std::string& error) = 0;
+
+  // Returns id of the flag's value type.
+  virtual flags_internal::FlagFastTypeId TypeId() const = 0;
+
+  // Interface to save flag to some persistent state. Returns current flag state
+  // or nullptr if flag does not support saving and restoring a state.
+  virtual std::unique_ptr<flags_internal::FlagStateInterface> SaveState() = 0;
+
+  // Copy-construct a new value of the flag's type in a memory referenced by
+  // the dst based on the current flag's value.
+  virtual void Read(void* dst) const = 0;
+
+  // To be deleted. Used to return true if flag's current value originated from
+  // command line.
+  virtual bool IsSpecifiedOnCommandLine() const = 0;
+
+  // Validates supplied value using validator or parseflag routine
+  virtual bool ValidateInputValue(absl::string_view value) const = 0;
+
+  // Checks that flags default value can be converted to string and back to the
+  // flag's value type.
+  virtual void CheckDefaultValueParsingRoundtrip() const = 0;
+};
+
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_FLAGS_COMMANDLINEFLAG_H_

Pods/abseil/absl/flags/config.h

@@ -0,0 +1,68 @@
+//
+//  Copyright 2019 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_FLAGS_CONFIG_H_
+#define ABSL_FLAGS_CONFIG_H_
+
+// Determine if we should strip string literals from the Flag objects.
+// By default we strip string literals on mobile platforms.
+#if !defined(ABSL_FLAGS_STRIP_NAMES)
+
+#if defined(__ANDROID__)
+#define ABSL_FLAGS_STRIP_NAMES 1
+
+#elif defined(__APPLE__)
+#include <TargetConditionals.h>
+#if defined(TARGET_OS_IPHONE) && TARGET_OS_IPHONE
+#define ABSL_FLAGS_STRIP_NAMES 1
+#elif defined(TARGET_OS_EMBEDDED) && TARGET_OS_EMBEDDED
+#define ABSL_FLAGS_STRIP_NAMES 1
+#endif  // TARGET_OS_*
+#endif
+
+#endif  // !defined(ABSL_FLAGS_STRIP_NAMES)
+
+#if !defined(ABSL_FLAGS_STRIP_NAMES)
+// If ABSL_FLAGS_STRIP_NAMES wasn't set on the command line or above,
+// the default is not to strip.
+#define ABSL_FLAGS_STRIP_NAMES 0
+#endif
+
+#if !defined(ABSL_FLAGS_STRIP_HELP)
+// By default, if we strip names, we also strip help.
+#define ABSL_FLAGS_STRIP_HELP ABSL_FLAGS_STRIP_NAMES
+#endif
+
+// These macros represent the "source of truth" for the list of supported
+// built-in types.
+#define ABSL_FLAGS_INTERNAL_BUILTIN_TYPES(A) \
+  A(bool, bool)                              \
+  A(short, short)                            \
+  A(unsigned short, unsigned_short)          \
+  A(int, int)                                \
+  A(unsigned int, unsigned_int)              \
+  A(long, long)                              \
+  A(unsigned long, unsigned_long)            \
+  A(long long, long_long)                    \
+  A(unsigned long long, unsigned_long_long)  \
+  A(double, double)                          \
+  A(float, float)
+
+#define ABSL_FLAGS_INTERNAL_SUPPORTED_TYPES(A) \
+  ABSL_FLAGS_INTERNAL_BUILTIN_TYPES(A)         \
+  A(std::string, std_string)                   \
+  A(std::vector<std::string>, std_vector_of_string)
+
+#endif  // ABSL_FLAGS_CONFIG_H_

Pods/abseil/absl/flags/declare.h

@@ -0,0 +1,68 @@
+//
+//  Copyright 2019 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// -----------------------------------------------------------------------------
+// File: declare.h
+// -----------------------------------------------------------------------------
+//
+// This file defines the ABSL_DECLARE_FLAG macro, allowing you to declare an
+// `absl::Flag` for use within a translation unit. You should place this
+// declaration within the header file associated with the .cc file that defines
+// and owns the `Flag`.
+
+#ifndef ABSL_FLAGS_DECLARE_H_
+#define ABSL_FLAGS_DECLARE_H_
+
+#include "absl/base/config.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace flags_internal {
+
+// absl::Flag<T> represents a flag of type 'T' created by ABSL_FLAG.
+template <typename T>
+class Flag;
+
+}  // namespace flags_internal
+
+// Flag
+//
+// Forward declaration of the `absl::Flag` type for use in defining the macro.
+template <typename T>
+using Flag = flags_internal::Flag<T>;
+
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+// ABSL_DECLARE_FLAG()
+//
+// This macro is a convenience for declaring use of an `absl::Flag` within a
+// translation unit. This macro should be used within a header file to
+// declare usage of the flag within any .cc file including that header file.
+//
+// The ABSL_DECLARE_FLAG(type, name) macro expands to:
+//
+//   extern absl::Flag<type> FLAGS_name;
+#define ABSL_DECLARE_FLAG(type, name) ABSL_DECLARE_FLAG_INTERNAL(type, name)
+
+// Internal implementation of ABSL_DECLARE_FLAG to allow macro expansion of its
+// arguments. Clients must use ABSL_DECLARE_FLAG instead.
+#define ABSL_DECLARE_FLAG_INTERNAL(type, name)               \
+  extern absl::Flag<type> FLAGS_##name;                      \
+  namespace absl /* block flags in namespaces */ {}          \
+  /* second redeclaration is to allow applying attributes */ \
+  extern absl::Flag<type> FLAGS_##name
+
+#endif  // ABSL_FLAGS_DECLARE_H_

Pods/abseil/absl/flags/flag.h

@@ -0,0 +1,301 @@
+//
+//  Copyright 2019 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// -----------------------------------------------------------------------------
+// File: flag.h
+// -----------------------------------------------------------------------------
+//
+// This header file defines the `absl::Flag<T>` type for holding command-line
+// flag data, and abstractions to create, get and set such flag data.
+//
+// It is important to note that this type is **unspecified** (an implementation
+// detail) and you do not construct or manipulate actual `absl::Flag<T>`
+// instances. Instead, you define and declare flags using the
+// `ABSL_FLAG()` and `ABSL_DECLARE_FLAG()` macros, and get and set flag values
+// using the `absl::GetFlag()` and `absl::SetFlag()` functions.
+
+#ifndef ABSL_FLAGS_FLAG_H_
+#define ABSL_FLAGS_FLAG_H_
+
+#include <string>
+#include <type_traits>
+
+#include "absl/base/attributes.h"
+#include "absl/base/config.h"
+#include "absl/base/optimization.h"
+#include "absl/flags/config.h"
+#include "absl/flags/internal/flag.h"
+#include "absl/flags/internal/registry.h"
+#include "absl/strings/string_view.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+// Flag
+//
+// An `absl::Flag` holds a command-line flag value, providing a runtime
+// parameter to a binary. Such flags should be defined in the global namespace
+// and (preferably) in the module containing the binary's `main()` function.
+//
+// You should not construct and cannot use the `absl::Flag` type directly;
+// instead, you should declare flags using the `ABSL_DECLARE_FLAG()` macro
+// within a header file, and define your flag using `ABSL_FLAG()` within your
+// header's associated `.cc` file. Such flags will be named `FLAGS_name`.
+//
+// Example:
+//
+//    .h file
+//
+//      // Declares usage of a flag named "FLAGS_count"
+//      ABSL_DECLARE_FLAG(int, count);
+//
+//    .cc file
+//
+//      // Defines a flag named "FLAGS_count" with a default `int` value of 0.
+//      ABSL_FLAG(int, count, 0, "Count of items to process");
+//
+// No public methods of `absl::Flag<T>` are part of the Abseil Flags API.
+//
+// For type support of Abseil Flags, see the marshalling.h header file, which
+// discusses supported standard types, optional flags, and additional Abseil
+// type support.
+
+template <typename T>
+using Flag = flags_internal::Flag<T>;
+
+// GetFlag()
+//
+// Returns the value (of type `T`) of an `absl::Flag<T>` instance, by value. Do
+// not construct an `absl::Flag<T>` directly and call `absl::GetFlag()`;
+// instead, refer to flag's constructed variable name (e.g. `FLAGS_name`).
+// Because this function returns by value and not by reference, it is
+// thread-safe, but note that the operation may be expensive; as a result, avoid
+// `absl::GetFlag()` within any tight loops.
+//
+// Example:
+//
+//   // FLAGS_count is a Flag of type `int`
+//   int my_count = absl::GetFlag(FLAGS_count);
+//
+//   // FLAGS_firstname is a Flag of type `std::string`
+//   std::string first_name = absl::GetFlag(FLAGS_firstname);
+template <typename T>
+ABSL_MUST_USE_RESULT T GetFlag(const absl::Flag<T>& flag) {
+  return flags_internal::FlagImplPeer::InvokeGet<T>(flag);
+}
+
+// SetFlag()
+//
+// Sets the value of an `absl::Flag` to the value `v`. Do not construct an
+// `absl::Flag<T>` directly and call `absl::SetFlag()`; instead, use the
+// flag's variable name (e.g. `FLAGS_name`). This function is
+// thread-safe, but is potentially expensive. Avoid setting flags in general,
+// but especially within performance-critical code.
+template <typename T>
+void SetFlag(absl::Flag<T>* flag, const T& v) {
+  flags_internal::FlagImplPeer::InvokeSet(*flag, v);
+}
+
+// Overload of `SetFlag()` to allow callers to pass in a value that is
+// convertible to `T`. E.g., use this overload to pass a "const char*" when `T`
+// is `std::string`.
+template <typename T, typename V>
+void SetFlag(absl::Flag<T>* flag, const V& v) {
+  T value(v);
+  flags_internal::FlagImplPeer::InvokeSet(*flag, value);
+}
+
+// GetFlagReflectionHandle()
+//
+// Returns the reflection handle corresponding to specified Abseil Flag
+// instance. Use this handle to access flag's reflection information, like name,
+// location, default value etc.
+//
+// Example:
+//
+//   std::string = absl::GetFlagReflectionHandle(FLAGS_count).DefaultValue();
+
+template <typename T>
+const CommandLineFlag& GetFlagReflectionHandle(const absl::Flag<T>& f) {
+  return flags_internal::FlagImplPeer::InvokeReflect(f);
+}
+
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+
+// ABSL_FLAG()
+//
+// This macro defines an `absl::Flag<T>` instance of a specified type `T`:
+//
+//   ABSL_FLAG(T, name, default_value, help);
+//
+// where:
+//
+//   * `T` is a supported flag type (see the list of types in `marshalling.h`),
+//   * `name` designates the name of the flag (as a global variable
+//     `FLAGS_name`),
+//   * `default_value` is an expression holding the default value for this flag
+//     (which must be implicitly convertible to `T`),
+//   * `help` is the help text, which can also be an expression.
+//
+// This macro expands to a flag named 'FLAGS_name' of type 'T':
+//
+//   absl::Flag<T> FLAGS_name = ...;
+//
+// Note that all such instances are created as global variables.
+//
+// For `ABSL_FLAG()` values that you wish to expose to other translation units,
+// it is recommended to define those flags within the `.cc` file associated with
+// the header where the flag is declared.
+//
+// Note: do not construct objects of type `absl::Flag<T>` directly. Only use the
+// `ABSL_FLAG()` macro for such construction.
+#define ABSL_FLAG(Type, name, default_value, help) \
+  ABSL_FLAG_IMPL(Type, name, default_value, help)
+
+// ABSL_FLAG().OnUpdate()
+//
+// Defines a flag of type `T` with a callback attached:
+//
+//   ABSL_FLAG(T, name, default_value, help).OnUpdate(callback);
+//
+// `callback` should be convertible to `void (*)()`.
+//
+// After any setting of the flag value, the callback will be called at least
+// once. A rapid sequence of changes may be merged together into the same
+// callback. No concurrent calls to the callback will be made for the same
+// flag. Callbacks are allowed to read the current value of the flag but must
+// not mutate that flag.
+//
+// The update mechanism guarantees "eventual consistency"; if the callback
+// derives an auxiliary data structure from the flag value, it is guaranteed
+// that eventually the flag value and the derived data structure will be
+// consistent.
+//
+// Note: ABSL_FLAG.OnUpdate() does not have a public definition. Hence, this
+// comment serves as its API documentation.
+
+// -----------------------------------------------------------------------------
+// Implementation details below this section
+// -----------------------------------------------------------------------------
+
+// ABSL_FLAG_IMPL macro definition conditional on ABSL_FLAGS_STRIP_NAMES
+#define ABSL_FLAG_IMPL_FLAG_PTR(flag) flag
+#define ABSL_FLAG_IMPL_HELP_ARG(name)                      \
+  absl::flags_internal::HelpArg<AbslFlagHelpGenFor##name>( \
+      FLAGS_help_storage_##name)
+#define ABSL_FLAG_IMPL_DEFAULT_ARG(Type, name) \
+  absl::flags_internal::DefaultArg<Type, AbslFlagDefaultGenFor##name>(0)
+
+#if ABSL_FLAGS_STRIP_NAMES
+#define ABSL_FLAG_IMPL_FLAGNAME(txt) ""
+#define ABSL_FLAG_IMPL_FILENAME() ""
+#define ABSL_FLAG_IMPL_REGISTRAR(T, flag)                                      \
+  absl::flags_internal::FlagRegistrar<T, false>(ABSL_FLAG_IMPL_FLAG_PTR(flag), \
+                                                nullptr)
+#else
+#define ABSL_FLAG_IMPL_FLAGNAME(txt) txt
+#define ABSL_FLAG_IMPL_FILENAME() __FILE__
+#define ABSL_FLAG_IMPL_REGISTRAR(T, flag)                                     \
+  absl::flags_internal::FlagRegistrar<T, true>(ABSL_FLAG_IMPL_FLAG_PTR(flag), \
+                                               __FILE__)
+#endif
+
+// ABSL_FLAG_IMPL macro definition conditional on ABSL_FLAGS_STRIP_HELP
+
+#if ABSL_FLAGS_STRIP_HELP
+#define ABSL_FLAG_IMPL_FLAGHELP(txt) absl::flags_internal::kStrippedFlagHelp
+#else
+#define ABSL_FLAG_IMPL_FLAGHELP(txt) txt
+#endif
+
+// AbslFlagHelpGenFor##name is used to encapsulate both immediate (method Const)
+// and lazy (method NonConst) evaluation of help message expression. We choose
+// between the two via the call to HelpArg in absl::Flag instantiation below.
+// If help message expression is constexpr evaluable compiler will optimize
+// away this whole struct.
+// TODO(rogeeff): place these generated structs into local namespace and apply
+// ABSL_INTERNAL_UNIQUE_SHORT_NAME.
+// TODO(rogeeff): Apply __attribute__((nodebug)) to FLAGS_help_storage_##name
+#define ABSL_FLAG_IMPL_DECLARE_HELP_WRAPPER(name, txt)                       \
+  struct AbslFlagHelpGenFor##name {                                          \
+    /* The expression is run in the caller as part of the   */               \
+    /* default value argument. That keeps temporaries alive */               \
+    /* long enough for NonConst to work correctly.          */               \
+    static constexpr absl::string_view Value(                                \
+        absl::string_view absl_flag_help = ABSL_FLAG_IMPL_FLAGHELP(txt)) {   \
+      return absl_flag_help;                                                 \
+    }                                                                        \
+    static std::string NonConst() { return std::string(Value()); }           \
+  };                                                                         \
+  constexpr auto FLAGS_help_storage_##name ABSL_INTERNAL_UNIQUE_SMALL_NAME() \
+      ABSL_ATTRIBUTE_SECTION_VARIABLE(flags_help_cold) =                     \
+          absl::flags_internal::HelpStringAsArray<AbslFlagHelpGenFor##name>( \
+              0);
+
+#define ABSL_FLAG_IMPL_DECLARE_DEF_VAL_WRAPPER(name, Type, default_value)     \
+  struct AbslFlagDefaultGenFor##name {                                        \
+    Type value = absl::flags_internal::InitDefaultValue<Type>(default_value); \
+    static void Gen(void* absl_flag_default_loc) {                            \
+      new (absl_flag_default_loc) Type(AbslFlagDefaultGenFor##name{}.value);  \
+    }                                                                         \
+  };
+
+// ABSL_FLAG_IMPL
+//
+// Note: Name of registrar object is not arbitrary. It is used to "grab"
+// global name for FLAGS_no<flag_name> symbol, thus preventing the possibility
+// of defining two flags with names foo and nofoo.
+#define ABSL_FLAG_IMPL(Type, name, default_value, help)                       \
+  extern ::absl::Flag<Type> FLAGS_##name;                                     \
+  namespace absl /* block flags in namespaces */ {}                           \
+  ABSL_FLAG_IMPL_DECLARE_DEF_VAL_WRAPPER(name, Type, default_value)           \
+  ABSL_FLAG_IMPL_DECLARE_HELP_WRAPPER(name, help)                             \
+  ABSL_CONST_INIT absl::Flag<Type> FLAGS_##name{                              \
+      ABSL_FLAG_IMPL_FLAGNAME(#name), ABSL_FLAG_IMPL_FILENAME(),              \
+      ABSL_FLAG_IMPL_HELP_ARG(name), ABSL_FLAG_IMPL_DEFAULT_ARG(Type, name)}; \
+  extern absl::flags_internal::FlagRegistrarEmpty FLAGS_no##name;             \
+  absl::flags_internal::FlagRegistrarEmpty FLAGS_no##name =                   \
+      ABSL_FLAG_IMPL_REGISTRAR(Type, FLAGS_##name)
+
+// ABSL_RETIRED_FLAG
+//
+// Designates the flag (which is usually pre-existing) as "retired." A retired
+// flag is a flag that is now unused by the program, but may still be passed on
+// the command line, usually by production scripts. A retired flag is ignored
+// and code can't access it at runtime.
+//
+// This macro registers a retired flag with given name and type, with a name
+// identical to the name of the original flag you are retiring. The retired
+// flag's type can change over time, so that you can retire code to support a
+// custom flag type.
+//
+// This macro has the same signature as `ABSL_FLAG`. To retire a flag, simply
+// replace an `ABSL_FLAG` definition with `ABSL_RETIRED_FLAG`, leaving the
+// arguments unchanged (unless of course you actually want to retire the flag
+// type at this time as well).
+//
+// `default_value` is only used as a double check on the type. `explanation` is
+// unused.
+// 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)      \
+  static absl::flags_internal::RetiredFlag<type> RETIRED_FLAGS_##name; \
+  ABSL_ATTRIBUTE_UNUSED static const auto RETIRED_FLAGS_REG_##name =   \
+      (RETIRED_FLAGS_##name.Retire(#name),                             \
+       ::absl::flags_internal::FlagRegistrarEmpty{})
+
+#endif  // ABSL_FLAGS_FLAG_H_

Pods/abseil/absl/flags/internal/commandlineflag.cc

@@ -0,0 +1,26 @@
+//
+// Copyright 2020 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/flags/internal/commandlineflag.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace flags_internal {
+
+FlagStateInterface::~FlagStateInterface() = default;
+
+}  // namespace flags_internal
+ABSL_NAMESPACE_END
+}  // namespace absl

Pods/abseil/absl/flags/internal/commandlineflag.h

@@ -0,0 +1,68 @@
+//
+// Copyright 2019 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_FLAGS_INTERNAL_COMMANDLINEFLAG_H_
+#define ABSL_FLAGS_INTERNAL_COMMANDLINEFLAG_H_
+
+#include "absl/base/config.h"
+#include "absl/base/internal/fast_type_id.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace flags_internal {
+
+// An alias for flag fast type id. This value identifies the flag value type
+// similarly to typeid(T), without relying on RTTI being available. In most
+// cases this id is enough to uniquely identify the flag's value type. In a few
+// cases we'll have to resort to using actual RTTI implementation if it is
+// available.
+using FlagFastTypeId = absl::base_internal::FastTypeIdType;
+
+// Options that control SetCommandLineOptionWithMode.
+enum FlagSettingMode {
+  // update the flag's value unconditionally (can call this multiple times).
+  SET_FLAGS_VALUE,
+  // update the flag's value, but *only if* it has not yet been updated
+  // with SET_FLAGS_VALUE, SET_FLAG_IF_DEFAULT, or "FLAGS_xxx = nondef".
+  SET_FLAG_IF_DEFAULT,
+  // set the flag's default value to this.  If the flag has not been updated
+  // yet (via SET_FLAGS_VALUE, SET_FLAG_IF_DEFAULT, or "FLAGS_xxx = nondef")
+  // change the flag's current value to the new default value as well.
+  SET_FLAGS_DEFAULT
+};
+
+// Options that control ParseFrom: Source of a value.
+enum ValueSource {
+  // Flag is being set by value specified on a command line.
+  kCommandLine,
+  // Flag is being set by value specified in the code.
+  kProgrammaticChange,
+};
+
+// Handle to FlagState objects. Specific flag state objects will restore state
+// of a flag produced this flag state from method CommandLineFlag::SaveState().
+class FlagStateInterface {
+ public:
+  virtual ~FlagStateInterface();
+
+  // Restores the flag originated this object to the saved state.
+  virtual void Restore() const = 0;
+};
+
+}  // namespace flags_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_FLAGS_INTERNAL_COMMANDLINEFLAG_H_

Pods/abseil/absl/flags/internal/flag.cc

@@ -0,0 +1,615 @@
+//
+// Copyright 2019 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/flags/internal/flag.h"
+
+#include <assert.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <string.h>
+
+#include <array>
+#include <atomic>
+#include <memory>
+#include <new>
+#include <string>
+#include <typeinfo>
+
+#include "absl/base/call_once.h"
+#include "absl/base/casts.h"
+#include "absl/base/config.h"
+#include "absl/base/dynamic_annotations.h"
+#include "absl/base/optimization.h"
+#include "absl/flags/config.h"
+#include "absl/flags/internal/commandlineflag.h"
+#include "absl/flags/usage_config.h"
+#include "absl/memory/memory.h"
+#include "absl/strings/str_cat.h"
+#include "absl/strings/string_view.h"
+#include "absl/synchronization/mutex.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace flags_internal {
+
+// The help message indicating that the commandline flag has been
+// 'stripped'. It will not show up when doing "-help" and its
+// variants. The flag is stripped if ABSL_FLAGS_STRIP_HELP is set to 1
+// before including absl/flags/flag.h
+const char kStrippedFlagHelp[] = "\001\002\003\004 (unknown) \004\003\002\001";
+
+namespace {
+
+// Currently we only validate flag values for user-defined flag types.
+bool ShouldValidateFlagValue(FlagFastTypeId flag_type_id) {
+#define DONT_VALIDATE(T, _) \
+  if (flag_type_id == base_internal::FastTypeId<T>()) return false;
+  ABSL_FLAGS_INTERNAL_SUPPORTED_TYPES(DONT_VALIDATE)
+#undef DONT_VALIDATE
+
+  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_;
+};
+
+}  // namespace
+
+///////////////////////////////////////////////////////////////////////////////
+// Persistent state of the flag data.
+
+class FlagImpl;
+
+class FlagState : public flags_internal::FlagStateInterface {
+ public:
+  template <typename V>
+  FlagState(FlagImpl& flag_impl, const V& v, bool modified,
+            bool on_command_line, int64_t counter)
+      : flag_impl_(flag_impl),
+        value_(v),
+        modified_(modified),
+        on_command_line_(on_command_line),
+        counter_(counter) {}
+
+  ~FlagState() override {
+    if (flag_impl_.ValueStorageKind() != FlagValueStorageKind::kAlignedBuffer &&
+        flag_impl_.ValueStorageKind() != FlagValueStorageKind::kSequenceLocked)
+      return;
+    flags_internal::Delete(flag_impl_.op_, value_.heap_allocated);
+  }
+
+ private:
+  friend class FlagImpl;
+
+  // Restores the flag to the saved state.
+  void Restore() const override {
+    if (!flag_impl_.RestoreState(*this)) return;
+
+    ABSL_INTERNAL_LOG(INFO,
+                      absl::StrCat("Restore saved value of ", flag_impl_.Name(),
+                                   " to: ", flag_impl_.CurrentValue()));
+  }
+
+  // Flag and saved flag data.
+  FlagImpl& flag_impl_;
+  union SavedValue {
+    explicit SavedValue(void* v) : heap_allocated(v) {}
+    explicit SavedValue(int64_t v) : one_word(v) {}
+
+    void* heap_allocated;
+    int64_t one_word;
+  } value_;
+  bool modified_;
+  bool on_command_line_;
+  int64_t counter_;
+};
+
+///////////////////////////////////////////////////////////////////////////////
+// Flag implementation, which does not depend on flag value type.
+
+DynValueDeleter::DynValueDeleter(FlagOpFn op_arg) : op(op_arg) {}
+
+void DynValueDeleter::operator()(void* ptr) const {
+  if (op == nullptr) return;
+
+  Delete(op, ptr);
+}
+
+void FlagImpl::Init() {
+  new (&data_guard_) absl::Mutex;
+
+  auto def_kind = static_cast<FlagDefaultKind>(def_kind_);
+
+  switch (ValueStorageKind()) {
+    case FlagValueStorageKind::kValueAndInitBit:
+    case FlagValueStorageKind::kOneWordAtomic: {
+      alignas(int64_t) std::array<char, sizeof(int64_t)> buf{};
+      if (def_kind == FlagDefaultKind::kGenFunc) {
+        (*default_value_.gen_func)(buf.data());
+      } else {
+        assert(def_kind != FlagDefaultKind::kDynamicValue);
+        std::memcpy(buf.data(), &default_value_, Sizeof(op_));
+      }
+      if (ValueStorageKind() == FlagValueStorageKind::kValueAndInitBit) {
+        // We presume here the memory layout of FlagValueAndInitBit struct.
+        uint8_t initialized = 1;
+        std::memcpy(buf.data() + Sizeof(op_), &initialized,
+                    sizeof(initialized));
+      }
+      // Type can contain valid uninitialized bits, e.g. padding.
+      ABSL_ANNOTATE_MEMORY_IS_INITIALIZED(buf.data(), buf.size());
+      OneWordValue().store(absl::bit_cast<int64_t>(buf),
+                           std::memory_order_release);
+      break;
+    }
+    case FlagValueStorageKind::kSequenceLocked: {
+      // For this storage kind the default_value_ always points to gen_func
+      // during initialization.
+      assert(def_kind == FlagDefaultKind::kGenFunc);
+      (*default_value_.gen_func)(AtomicBufferValue());
+      break;
+    }
+    case FlagValueStorageKind::kAlignedBuffer:
+      // For this storage kind the default_value_ always points to gen_func
+      // during initialization.
+      assert(def_kind == FlagDefaultKind::kGenFunc);
+      (*default_value_.gen_func)(AlignedBufferValue());
+      break;
+  }
+  seq_lock_.MarkInitialized();
+}
+
+absl::Mutex* FlagImpl::DataGuard() const {
+  absl::call_once(const_cast<FlagImpl*>(this)->init_control_, &FlagImpl::Init,
+                  const_cast<FlagImpl*>(this));
+
+  // data_guard_ is initialized inside Init.
+  return reinterpret_cast<absl::Mutex*>(&data_guard_);
+}
+
+void FlagImpl::AssertValidType(FlagFastTypeId rhs_type_id,
+                               const std::type_info* (*gen_rtti)()) const {
+  FlagFastTypeId lhs_type_id = flags_internal::FastTypeId(op_);
+
+  // `rhs_type_id` is the fast type id corresponding to the declaration
+  // visible at the call site. `lhs_type_id` is the fast type id
+  // corresponding to the type specified in flag definition. They must match
+  //  for this operation to be well-defined.
+  if (ABSL_PREDICT_TRUE(lhs_type_id == rhs_type_id)) return;
+
+  const std::type_info* lhs_runtime_type_id =
+      flags_internal::RuntimeTypeId(op_);
+  const std::type_info* rhs_runtime_type_id = (*gen_rtti)();
+
+  if (lhs_runtime_type_id == rhs_runtime_type_id) return;
+
+#ifdef ABSL_INTERNAL_HAS_RTTI
+  if (*lhs_runtime_type_id == *rhs_runtime_type_id) return;
+#endif
+
+  ABSL_INTERNAL_LOG(
+      FATAL, absl::StrCat("Flag '", Name(),
+                          "' is defined as one type and declared as another"));
+}
+
+std::unique_ptr<void, DynValueDeleter> FlagImpl::MakeInitValue() const {
+  void* res = nullptr;
+  switch (DefaultKind()) {
+    case FlagDefaultKind::kDynamicValue:
+      res = flags_internal::Clone(op_, default_value_.dynamic_value);
+      break;
+    case FlagDefaultKind::kGenFunc:
+      res = flags_internal::Alloc(op_);
+      (*default_value_.gen_func)(res);
+      break;
+    default:
+      res = flags_internal::Clone(op_, &default_value_);
+      break;
+  }
+  return {res, DynValueDeleter{op_}};
+}
+
+void FlagImpl::StoreValue(const void* src) {
+  switch (ValueStorageKind()) {
+    case FlagValueStorageKind::kValueAndInitBit:
+    case FlagValueStorageKind::kOneWordAtomic: {
+      // Load the current value to avoid setting 'init' bit manually.
+      int64_t one_word_val = OneWordValue().load(std::memory_order_acquire);
+      std::memcpy(&one_word_val, src, Sizeof(op_));
+      OneWordValue().store(one_word_val, std::memory_order_release);
+      seq_lock_.IncrementModificationCount();
+      break;
+    }
+    case FlagValueStorageKind::kSequenceLocked: {
+      seq_lock_.Write(AtomicBufferValue(), src, Sizeof(op_));
+      break;
+    }
+    case FlagValueStorageKind::kAlignedBuffer:
+      Copy(op_, src, AlignedBufferValue());
+      seq_lock_.IncrementModificationCount();
+      break;
+  }
+  modified_ = true;
+  InvokeCallback();
+}
+
+absl::string_view FlagImpl::Name() const { return name_; }
+
+std::string FlagImpl::Filename() const {
+  return flags_internal::GetUsageConfig().normalize_filename(filename_);
+}
+
+std::string FlagImpl::Help() const {
+  return HelpSourceKind() == FlagHelpKind::kLiteral ? help_.literal
+                                                    : help_.gen_func();
+}
+
+FlagFastTypeId FlagImpl::TypeId() const {
+  return flags_internal::FastTypeId(op_);
+}
+
+int64_t FlagImpl::ModificationCount() const {
+  return seq_lock_.ModificationCount();
+}
+
+bool FlagImpl::IsSpecifiedOnCommandLine() const {
+  absl::MutexLock l(DataGuard());
+  return on_command_line_;
+}
+
+std::string FlagImpl::DefaultValue() const {
+  absl::MutexLock l(DataGuard());
+
+  auto obj = MakeInitValue();
+  return flags_internal::Unparse(op_, obj.get());
+}
+
+std::string FlagImpl::CurrentValue() const {
+  auto* guard = DataGuard();  // Make sure flag initialized
+  switch (ValueStorageKind()) {
+    case FlagValueStorageKind::kValueAndInitBit:
+    case FlagValueStorageKind::kOneWordAtomic: {
+      const auto one_word_val =
+          absl::bit_cast<std::array<char, sizeof(int64_t)>>(
+              OneWordValue().load(std::memory_order_acquire));
+      return flags_internal::Unparse(op_, one_word_val.data());
+    }
+    case FlagValueStorageKind::kSequenceLocked: {
+      std::unique_ptr<void, DynValueDeleter> cloned(flags_internal::Alloc(op_),
+                                                    DynValueDeleter{op_});
+      ReadSequenceLockedData(cloned.get());
+      return flags_internal::Unparse(op_, cloned.get());
+    }
+    case FlagValueStorageKind::kAlignedBuffer: {
+      absl::MutexLock l(guard);
+      return flags_internal::Unparse(op_, AlignedBufferValue());
+    }
+  }
+
+  return "";
+}
+
+void FlagImpl::SetCallback(const FlagCallbackFunc mutation_callback) {
+  absl::MutexLock l(DataGuard());
+
+  if (callback_ == nullptr) {
+    callback_ = new FlagCallback;
+  }
+  callback_->func = mutation_callback;
+
+  InvokeCallback();
+}
+
+void FlagImpl::InvokeCallback() const {
+  if (!callback_) return;
+
+  // Make a copy of the C-style function pointer that we are about to invoke
+  // before we release the lock guarding it.
+  FlagCallbackFunc cb = callback_->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
+  // re-locked back after call to callback is completed. Callback invocation is
+  // guarded by flag's secondary mutex instead which prevents concurrent
+  // callback invocation. Note that it is possible for other thread to grab the
+  // primary lock and update flag's value at any time during the callback
+  // invocation. This is by design. Callback can get a value of the flag if
+  // necessary, but it might be different from the value initiated the callback
+  // 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.
+  MutexRelock relock(*DataGuard());
+  absl::MutexLock lock(&callback_->guard);
+  cb();
+}
+
+std::unique_ptr<FlagStateInterface> FlagImpl::SaveState() {
+  absl::MutexLock l(DataGuard());
+
+  bool modified = modified_;
+  bool on_command_line = on_command_line_;
+  switch (ValueStorageKind()) {
+    case FlagValueStorageKind::kValueAndInitBit:
+    case FlagValueStorageKind::kOneWordAtomic: {
+      return absl::make_unique<FlagState>(
+          *this, OneWordValue().load(std::memory_order_acquire), modified,
+          on_command_line, ModificationCount());
+    }
+    case FlagValueStorageKind::kSequenceLocked: {
+      void* cloned = flags_internal::Alloc(op_);
+      // Read is guaranteed to be successful because we hold the lock.
+      bool success =
+          seq_lock_.TryRead(cloned, AtomicBufferValue(), Sizeof(op_));
+      assert(success);
+      static_cast<void>(success);
+      return absl::make_unique<FlagState>(*this, cloned, modified,
+                                          on_command_line, ModificationCount());
+    }
+    case FlagValueStorageKind::kAlignedBuffer: {
+      return absl::make_unique<FlagState>(
+          *this, flags_internal::Clone(op_, AlignedBufferValue()), modified,
+          on_command_line, ModificationCount());
+    }
+  }
+  return nullptr;
+}
+
+bool FlagImpl::RestoreState(const FlagState& flag_state) {
+  absl::MutexLock l(DataGuard());
+  if (flag_state.counter_ == ModificationCount()) {
+    return false;
+  }
+
+  switch (ValueStorageKind()) {
+    case FlagValueStorageKind::kValueAndInitBit:
+    case FlagValueStorageKind::kOneWordAtomic:
+      StoreValue(&flag_state.value_.one_word);
+      break;
+    case FlagValueStorageKind::kSequenceLocked:
+    case FlagValueStorageKind::kAlignedBuffer:
+      StoreValue(flag_state.value_.heap_allocated);
+      break;
+  }
+
+  modified_ = flag_state.modified_;
+  on_command_line_ = flag_state.on_command_line_;
+
+  return true;
+}
+
+template <typename StorageT>
+StorageT* FlagImpl::OffsetValue() const {
+  char* p = reinterpret_cast<char*>(const_cast<FlagImpl*>(this));
+  // The offset is deduced via Flag value type specific op_.
+  ptrdiff_t offset = flags_internal::ValueOffset(op_);
+
+  return reinterpret_cast<StorageT*>(p + offset);
+}
+
+void* FlagImpl::AlignedBufferValue() const {
+  assert(ValueStorageKind() == FlagValueStorageKind::kAlignedBuffer);
+  return OffsetValue<void>();
+}
+
+std::atomic<uint64_t>* FlagImpl::AtomicBufferValue() const {
+  assert(ValueStorageKind() == FlagValueStorageKind::kSequenceLocked);
+  return OffsetValue<std::atomic<uint64_t>>();
+}
+
+std::atomic<int64_t>& FlagImpl::OneWordValue() const {
+  assert(ValueStorageKind() == FlagValueStorageKind::kOneWordAtomic ||
+         ValueStorageKind() == FlagValueStorageKind::kValueAndInitBit);
+  return OffsetValue<FlagOneWordValue>()->value;
+}
+
+// Attempts to parse supplied `value` string using parsing routine in the `flag`
+// 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'
+std::unique_ptr<void, DynValueDeleter> FlagImpl::TryParse(
+    absl::string_view value, std::string& err) const {
+  std::unique_ptr<void, DynValueDeleter> tentative_value = MakeInitValue();
+
+  std::string parse_err;
+  if (!flags_internal::Parse(op_, value, tentative_value.get(), &parse_err)) {
+    absl::string_view err_sep = parse_err.empty() ? "" : "; ";
+    err = absl::StrCat("Illegal value '", value, "' specified for flag '",
+                       Name(), "'", err_sep, parse_err);
+    return nullptr;
+  }
+
+  return tentative_value;
+}
+
+void FlagImpl::Read(void* dst) const {
+  auto* guard = DataGuard();  // Make sure flag initialized
+  switch (ValueStorageKind()) {
+    case FlagValueStorageKind::kValueAndInitBit:
+    case FlagValueStorageKind::kOneWordAtomic: {
+      const int64_t one_word_val =
+          OneWordValue().load(std::memory_order_acquire);
+      std::memcpy(dst, &one_word_val, Sizeof(op_));
+      break;
+    }
+    case FlagValueStorageKind::kSequenceLocked: {
+      ReadSequenceLockedData(dst);
+      break;
+    }
+    case FlagValueStorageKind::kAlignedBuffer: {
+      absl::MutexLock l(guard);
+      flags_internal::CopyConstruct(op_, AlignedBufferValue(), dst);
+      break;
+    }
+  }
+}
+
+int64_t FlagImpl::ReadOneWord() const {
+  assert(ValueStorageKind() == FlagValueStorageKind::kOneWordAtomic ||
+         ValueStorageKind() == FlagValueStorageKind::kValueAndInitBit);
+  auto* guard = DataGuard();  // Make sure flag initialized
+  (void)guard;
+  return OneWordValue().load(std::memory_order_acquire);
+}
+
+bool FlagImpl::ReadOneBool() const {
+  assert(ValueStorageKind() == FlagValueStorageKind::kValueAndInitBit);
+  auto* guard = DataGuard();  // Make sure flag initialized
+  (void)guard;
+  return absl::bit_cast<FlagValueAndInitBit<bool>>(
+             OneWordValue().load(std::memory_order_acquire))
+      .value;
+}
+
+void FlagImpl::ReadSequenceLockedData(void* dst) const {
+  size_t size = Sizeof(op_);
+  // Attempt to read using the sequence lock.
+  if (ABSL_PREDICT_TRUE(seq_lock_.TryRead(dst, AtomicBufferValue(), size))) {
+    return;
+  }
+  // We failed due to contention. Acquire the lock to prevent contention
+  // and try again.
+  absl::ReaderMutexLock l(DataGuard());
+  bool success = seq_lock_.TryRead(dst, AtomicBufferValue(), size);
+  assert(success);
+  static_cast<void>(success);
+}
+
+void FlagImpl::Write(const void* src) {
+  absl::MutexLock l(DataGuard());
+
+  if (ShouldValidateFlagValue(flags_internal::FastTypeId(op_))) {
+    std::unique_ptr<void, DynValueDeleter> obj{flags_internal::Clone(op_, src),
+                                               DynValueDeleter{op_}};
+    std::string ignored_error;
+    std::string src_as_str = flags_internal::Unparse(op_, src);
+    if (!flags_internal::Parse(op_, src_as_str, obj.get(), &ignored_error)) {
+      ABSL_INTERNAL_LOG(ERROR, absl::StrCat("Attempt to set flag '", Name(),
+                                            "' to invalid value ", src_as_str));
+    }
+  }
+
+  StoreValue(src);
+}
+
+// Sets the value of the flag based on specified string `value`. If the flag
+// was successfully set to new value, it returns true. Otherwise, sets `err`
+// to indicate the error, leaves the flag unchanged, and returns false. There
+// are three ways to set the flag's value:
+//  * Update the current flag value
+//  * Update the flag's default value
+//  * Update the current flag value if it was never set before
+// The mode is selected based on 'set_mode' parameter.
+bool FlagImpl::ParseFrom(absl::string_view value, FlagSettingMode set_mode,
+                         ValueSource source, std::string& err) {
+  absl::MutexLock l(DataGuard());
+
+  switch (set_mode) {
+    case SET_FLAGS_VALUE: {
+      // set or modify the flag's value
+      auto tentative_value = TryParse(value, err);
+      if (!tentative_value) return false;
+
+      StoreValue(tentative_value.get());
+
+      if (source == kCommandLine) {
+        on_command_line_ = true;
+      }
+      break;
+    }
+    case SET_FLAG_IF_DEFAULT: {
+      // set the flag's value, but only if it hasn't been set by someone else
+      if (modified_) {
+        // TODO(rogeeff): review and fix this semantic. Currently we do not fail
+        // in this case if flag is modified. This is misleading since the flag's
+        // value is not updated even though we return true.
+        // *err = absl::StrCat(Name(), " is already set to ",
+        //                     CurrentValue(), "\n");
+        // return false;
+        return true;
+      }
+      auto tentative_value = TryParse(value, err);
+      if (!tentative_value) return false;
+
+      StoreValue(tentative_value.get());
+      break;
+    }
+    case SET_FLAGS_DEFAULT: {
+      auto tentative_value = TryParse(value, err);
+      if (!tentative_value) return false;
+
+      if (DefaultKind() == FlagDefaultKind::kDynamicValue) {
+        void* old_value = default_value_.dynamic_value;
+        default_value_.dynamic_value = tentative_value.release();
+        tentative_value.reset(old_value);
+      } else {
+        default_value_.dynamic_value = tentative_value.release();
+        def_kind_ = static_cast<uint8_t>(FlagDefaultKind::kDynamicValue);
+      }
+
+      if (!modified_) {
+        // Need to set both default value *and* current, in this case.
+        StoreValue(default_value_.dynamic_value);
+        modified_ = false;
+      }
+      break;
+    }
+  }
+
+  return true;
+}
+
+void FlagImpl::CheckDefaultValueParsingRoundtrip() const {
+  std::string v = DefaultValue();
+
+  absl::MutexLock lock(DataGuard());
+
+  auto dst = MakeInitValue();
+  std::string error;
+  if (!flags_internal::Parse(op_, v, dst.get(), &error)) {
+    ABSL_INTERNAL_LOG(
+        FATAL,
+        absl::StrCat("Flag ", Name(), " (from ", Filename(),
+                     "): string form of default value '", v,
+                     "' could not be parsed; error=", error));
+  }
+
+  // We do not compare dst to def since parsing/unparsing may make
+  // small changes, e.g., precision loss for floating point types.
+}
+
+bool FlagImpl::ValidateInputValue(absl::string_view value) const {
+  absl::MutexLock l(DataGuard());
+
+  auto obj = MakeInitValue();
+  std::string ignored_error;
+  return flags_internal::Parse(op_, value, obj.get(), &ignored_error);
+}
+
+}  // namespace flags_internal
+ABSL_NAMESPACE_END
+}  // namespace absl

Pods/abseil/absl/flags/internal/flag.h

@@ -0,0 +1,796 @@
+//
+// Copyright 2019 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_FLAGS_INTERNAL_FLAG_H_
+#define ABSL_FLAGS_INTERNAL_FLAG_H_
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include <atomic>
+#include <cstring>
+#include <memory>
+#include <new>
+#include <string>
+#include <type_traits>
+#include <typeinfo>
+
+#include "absl/base/attributes.h"
+#include "absl/base/call_once.h"
+#include "absl/base/casts.h"
+#include "absl/base/config.h"
+#include "absl/base/optimization.h"
+#include "absl/base/thread_annotations.h"
+#include "absl/flags/commandlineflag.h"
+#include "absl/flags/config.h"
+#include "absl/flags/internal/commandlineflag.h"
+#include "absl/flags/internal/registry.h"
+#include "absl/flags/internal/sequence_lock.h"
+#include "absl/flags/marshalling.h"
+#include "absl/meta/type_traits.h"
+#include "absl/strings/string_view.h"
+#include "absl/synchronization/mutex.h"
+#include "absl/utility/utility.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+///////////////////////////////////////////////////////////////////////////////
+// Forward declaration of absl::Flag<T> public API.
+namespace flags_internal {
+template <typename T>
+class Flag;
+}  // namespace flags_internal
+
+template <typename T>
+using Flag = flags_internal::Flag<T>;
+
+template <typename T>
+ABSL_MUST_USE_RESULT T GetFlag(const absl::Flag<T>& flag);
+
+template <typename T>
+void SetFlag(absl::Flag<T>* flag, const T& v);
+
+template <typename T, typename V>
+void SetFlag(absl::Flag<T>* flag, const V& v);
+
+template <typename U>
+const CommandLineFlag& GetFlagReflectionHandle(const absl::Flag<U>& f);
+
+///////////////////////////////////////////////////////////////////////////////
+// Flag value type operations, eg., parsing, copying, etc. are provided
+// by function specific to that type with a signature matching FlagOpFn.
+
+namespace flags_internal {
+
+enum class FlagOp {
+  kAlloc,
+  kDelete,
+  kCopy,
+  kCopyConstruct,
+  kSizeof,
+  kFastTypeId,
+  kRuntimeTypeId,
+  kParse,
+  kUnparse,
+  kValueOffset,
+};
+using FlagOpFn = void* (*)(FlagOp, const void*, void*, void*);
+
+// Forward declaration for Flag value specific operations.
+template <typename T>
+void* FlagOps(FlagOp op, const void* v1, void* v2, void* v3);
+
+// Allocate aligned memory for a flag value.
+inline void* Alloc(FlagOpFn op) {
+  return op(FlagOp::kAlloc, nullptr, nullptr, nullptr);
+}
+// Deletes memory interpreting obj as flag value type pointer.
+inline void Delete(FlagOpFn op, void* obj) {
+  op(FlagOp::kDelete, nullptr, obj, nullptr);
+}
+// Copies src to dst interpreting as flag value type pointers.
+inline void Copy(FlagOpFn op, const void* src, void* dst) {
+  op(FlagOp::kCopy, src, dst, nullptr);
+}
+// Construct a copy of flag value in a location pointed by dst
+// based on src - pointer to the flag's value.
+inline void CopyConstruct(FlagOpFn op, const void* src, void* dst) {
+  op(FlagOp::kCopyConstruct, src, dst, nullptr);
+}
+// Makes a copy of flag value pointed by obj.
+inline void* Clone(FlagOpFn op, const void* obj) {
+  void* res = flags_internal::Alloc(op);
+  flags_internal::CopyConstruct(op, obj, res);
+  return res;
+}
+// Returns true if parsing of input text is successful.
+inline bool Parse(FlagOpFn op, absl::string_view text, void* dst,
+                  std::string* error) {
+  return op(FlagOp::kParse, &text, dst, error) != nullptr;
+}
+// Returns string representing supplied value.
+inline std::string Unparse(FlagOpFn op, const void* val) {
+  std::string result;
+  op(FlagOp::kUnparse, val, &result, nullptr);
+  return result;
+}
+// Returns size of flag value type.
+inline size_t Sizeof(FlagOpFn op) {
+  // This sequence of casts reverses the sequence from
+  // `flags_internal::FlagOps()`
+  return static_cast<size_t>(reinterpret_cast<intptr_t>(
+      op(FlagOp::kSizeof, nullptr, nullptr, nullptr)));
+}
+// Returns fast type id corresponding to the value type.
+inline FlagFastTypeId FastTypeId(FlagOpFn op) {
+  return reinterpret_cast<FlagFastTypeId>(
+      op(FlagOp::kFastTypeId, nullptr, nullptr, nullptr));
+}
+// Returns fast type id corresponding to the value type.
+inline const std::type_info* RuntimeTypeId(FlagOpFn op) {
+  return reinterpret_cast<const std::type_info*>(
+      op(FlagOp::kRuntimeTypeId, nullptr, nullptr, nullptr));
+}
+// Returns offset of the field value_ from the field impl_ inside of
+// absl::Flag<T> data. Given FlagImpl pointer p you can get the
+// location of the corresponding value as:
+//      reinterpret_cast<char*>(p) + ValueOffset().
+inline ptrdiff_t ValueOffset(FlagOpFn op) {
+  // This sequence of casts reverses the sequence from
+  // `flags_internal::FlagOps()`
+  return static_cast<ptrdiff_t>(reinterpret_cast<intptr_t>(
+      op(FlagOp::kValueOffset, nullptr, nullptr, nullptr)));
+}
+
+// Returns an address of RTTI's typeid(T).
+template <typename T>
+inline const std::type_info* GenRuntimeTypeId() {
+#ifdef ABSL_INTERNAL_HAS_RTTI
+  return &typeid(T);
+#else
+  return nullptr;
+#endif
+}
+
+///////////////////////////////////////////////////////////////////////////////
+// Flag help auxiliary structs.
+
+// This is help argument for absl::Flag encapsulating the string literal pointer
+// or pointer to function generating it as well as enum descriminating two
+// cases.
+using HelpGenFunc = std::string (*)();
+
+template <size_t N>
+struct FixedCharArray {
+  char value[N];
+
+  template <size_t... I>
+  static constexpr FixedCharArray<N> FromLiteralString(
+      absl::string_view str, absl::index_sequence<I...>) {
+    return (void)str, FixedCharArray<N>({{str[I]..., '\0'}});
+  }
+};
+
+template <typename Gen, size_t N = Gen::Value().size()>
+constexpr FixedCharArray<N + 1> HelpStringAsArray(int) {
+  return FixedCharArray<N + 1>::FromLiteralString(
+      Gen::Value(), absl::make_index_sequence<N>{});
+}
+
+template <typename Gen>
+constexpr std::false_type HelpStringAsArray(char) {
+  return std::false_type{};
+}
+
+union FlagHelpMsg {
+  constexpr explicit FlagHelpMsg(const char* help_msg) : literal(help_msg) {}
+  constexpr explicit FlagHelpMsg(HelpGenFunc help_gen) : gen_func(help_gen) {}
+
+  const char* literal;
+  HelpGenFunc gen_func;
+};
+
+enum class FlagHelpKind : uint8_t { kLiteral = 0, kGenFunc = 1 };
+
+struct FlagHelpArg {
+  FlagHelpMsg source;
+  FlagHelpKind kind;
+};
+
+extern const char kStrippedFlagHelp[];
+
+// These two HelpArg overloads allows us to select at compile time one of two
+// way to pass Help argument to absl::Flag. We'll be passing
+// AbslFlagHelpGenFor##name as Gen and integer 0 as a single argument to prefer
+// first overload if possible. If help message is evaluatable on constexpr
+// context We'll be able to make FixedCharArray out of it and we'll choose first
+// overload. In this case the help message expression is immediately evaluated
+// and is used to construct the absl::Flag. No additional code is generated by
+// ABSL_FLAG Otherwise SFINAE kicks in and first overload is dropped from the
+// consideration, in which case the second overload will be used. The second
+// overload does not attempt to evaluate the help message expression
+// immediately and instead delays the evaluation by returning the function
+// pointer (&T::NonConst) generating the help message when necessary. This is
+// evaluatable in constexpr context, but the cost is an extra function being
+// generated in the ABSL_FLAG code.
+template <typename Gen, size_t N>
+constexpr FlagHelpArg HelpArg(const FixedCharArray<N>& value) {
+  return {FlagHelpMsg(value.value), FlagHelpKind::kLiteral};
+}
+
+template <typename Gen>
+constexpr FlagHelpArg HelpArg(std::false_type) {
+  return {FlagHelpMsg(&Gen::NonConst), FlagHelpKind::kGenFunc};
+}
+
+///////////////////////////////////////////////////////////////////////////////
+// Flag default value auxiliary structs.
+
+// Signature for the function generating the initial flag value (usually
+// based on default value supplied in flag's definition)
+using FlagDfltGenFunc = void (*)(void*);
+
+union FlagDefaultSrc {
+  constexpr explicit FlagDefaultSrc(FlagDfltGenFunc gen_func_arg)
+      : gen_func(gen_func_arg) {}
+
+#define ABSL_FLAGS_INTERNAL_DFLT_FOR_TYPE(T, name) \
+  T name##_value;                                  \
+  constexpr explicit FlagDefaultSrc(T value) : name##_value(value) {}  // NOLINT
+  ABSL_FLAGS_INTERNAL_BUILTIN_TYPES(ABSL_FLAGS_INTERNAL_DFLT_FOR_TYPE)
+#undef ABSL_FLAGS_INTERNAL_DFLT_FOR_TYPE
+
+  void* dynamic_value;
+  FlagDfltGenFunc gen_func;
+};
+
+enum class FlagDefaultKind : uint8_t {
+  kDynamicValue = 0,
+  kGenFunc = 1,
+  kOneWord = 2  // for default values UP to one word in size
+};
+
+struct FlagDefaultArg {
+  FlagDefaultSrc source;
+  FlagDefaultKind kind;
+};
+
+// 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 =
+              ((void)GenT{}, 0)>
+constexpr FlagDefaultArg DefaultArg(int) {
+  return {FlagDefaultSrc(GenT{}.value), FlagDefaultKind::kOneWord};
+}
+
+template <typename ValueT, typename GenT>
+constexpr FlagDefaultArg DefaultArg(char) {
+  return {FlagDefaultSrc(&GenT::Gen), FlagDefaultKind::kGenFunc};
+}
+
+///////////////////////////////////////////////////////////////////////////////
+// Flag current value auxiliary structs.
+
+constexpr int64_t UninitializedFlagValue() {
+  return static_cast<int64_t>(0xababababababababll);
+}
+
+template <typename T>
+using FlagUseValueAndInitBitStorage =
+    std::integral_constant<bool, std::is_trivially_copyable<T>::value &&
+                                     std::is_default_constructible<T>::value &&
+                                     (sizeof(T) < 8)>;
+
+template <typename T>
+using FlagUseOneWordStorage =
+    std::integral_constant<bool, std::is_trivially_copyable<T>::value &&
+                                     (sizeof(T) <= 8)>;
+
+template <class T>
+using FlagUseSequenceLockStorage =
+    std::integral_constant<bool, std::is_trivially_copyable<T>::value &&
+                                     (sizeof(T) > 8)>;
+
+enum class FlagValueStorageKind : uint8_t {
+  kValueAndInitBit = 0,
+  kOneWordAtomic = 1,
+  kSequenceLocked = 2,
+  kAlignedBuffer = 3,
+};
+
+template <typename T>
+static constexpr FlagValueStorageKind StorageKind() {
+  return FlagUseValueAndInitBitStorage<T>::value
+             ? FlagValueStorageKind::kValueAndInitBit
+         : FlagUseOneWordStorage<T>::value
+             ? FlagValueStorageKind::kOneWordAtomic
+         : FlagUseSequenceLockStorage<T>::value
+             ? FlagValueStorageKind::kSequenceLocked
+             : FlagValueStorageKind::kAlignedBuffer;
+}
+
+struct FlagOneWordValue {
+  constexpr explicit FlagOneWordValue(int64_t v) : value(v) {}
+  std::atomic<int64_t> value;
+};
+
+template <typename T>
+struct alignas(8) FlagValueAndInitBit {
+  T value;
+  // Use an int instead of a bool to guarantee that a non-zero value has
+  // a bit set.
+  uint8_t init;
+};
+
+template <typename T,
+          FlagValueStorageKind Kind = flags_internal::StorageKind<T>()>
+struct FlagValue;
+
+template <typename T>
+struct FlagValue<T, FlagValueStorageKind::kValueAndInitBit> : FlagOneWordValue {
+  constexpr FlagValue() : FlagOneWordValue(0) {}
+  bool Get(const SequenceLock&, T& dst) const {
+    int64_t storage = value.load(std::memory_order_acquire);
+    if (ABSL_PREDICT_FALSE(storage == 0)) {
+      return false;
+    }
+    dst = absl::bit_cast<FlagValueAndInitBit<T>>(storage).value;
+    return true;
+  }
+};
+
+template <typename T>
+struct FlagValue<T, FlagValueStorageKind::kOneWordAtomic> : FlagOneWordValue {
+  constexpr FlagValue() : FlagOneWordValue(UninitializedFlagValue()) {}
+  bool Get(const SequenceLock&, T& dst) const {
+    int64_t one_word_val = value.load(std::memory_order_acquire);
+    if (ABSL_PREDICT_FALSE(one_word_val == UninitializedFlagValue())) {
+      return false;
+    }
+    std::memcpy(&dst, static_cast<const void*>(&one_word_val), sizeof(T));
+    return true;
+  }
+};
+
+template <typename T>
+struct FlagValue<T, FlagValueStorageKind::kSequenceLocked> {
+  bool Get(const SequenceLock& lock, T& dst) const {
+    return lock.TryRead(&dst, value_words, sizeof(T));
+  }
+
+  static constexpr int kNumWords =
+      flags_internal::AlignUp(sizeof(T), sizeof(uint64_t)) / sizeof(uint64_t);
+
+  alignas(T) alignas(
+      std::atomic<uint64_t>) std::atomic<uint64_t> value_words[kNumWords];
+};
+
+template <typename T>
+struct FlagValue<T, FlagValueStorageKind::kAlignedBuffer> {
+  bool Get(const SequenceLock&, T&) const { return false; }
+
+  alignas(T) char value[sizeof(T)];
+};
+
+///////////////////////////////////////////////////////////////////////////////
+// Flag callback auxiliary structs.
+
+// Signature for the mutation callback used by watched Flags
+// The callback is noexcept.
+// TODO(rogeeff): add noexcept after C++17 support is added.
+using FlagCallbackFunc = void (*)();
+
+struct FlagCallback {
+  FlagCallbackFunc func;
+  absl::Mutex guard;  // Guard for concurrent callback invocations.
+};
+
+///////////////////////////////////////////////////////////////////////////////
+// Flag implementation, which does not depend on flag value type.
+// The class encapsulates the Flag's data and access to it.
+
+struct DynValueDeleter {
+  explicit DynValueDeleter(FlagOpFn op_arg = nullptr);
+  void operator()(void* ptr) const;
+
+  FlagOpFn op;
+};
+
+class FlagState;
+
+class FlagImpl final : public CommandLineFlag {
+ public:
+  constexpr FlagImpl(const char* name, const char* filename, FlagOpFn op,
+                     FlagHelpArg help, FlagValueStorageKind value_kind,
+                     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>(default_arg.kind)),
+        modified_(false),
+        on_command_line_(false),
+        callback_(nullptr),
+        default_value_(default_arg.source),
+        data_guard_{} {}
+
+  // Constant access methods
+  int64_t ReadOneWord() const ABSL_LOCKS_EXCLUDED(*DataGuard());
+  bool ReadOneBool() const ABSL_LOCKS_EXCLUDED(*DataGuard());
+  void Read(void* dst) const override ABSL_LOCKS_EXCLUDED(*DataGuard());
+  void Read(bool* value) const ABSL_LOCKS_EXCLUDED(*DataGuard()) {
+    *value = ReadOneBool();
+  }
+  template <typename T,
+            absl::enable_if_t<flags_internal::StorageKind<T>() ==
+                                  FlagValueStorageKind::kOneWordAtomic,
+                              int> = 0>
+  void Read(T* value) const ABSL_LOCKS_EXCLUDED(*DataGuard()) {
+    int64_t v = ReadOneWord();
+    std::memcpy(value, static_cast<const void*>(&v), sizeof(T));
+  }
+  template <typename T,
+            typename std::enable_if<flags_internal::StorageKind<T>() ==
+                                        FlagValueStorageKind::kValueAndInitBit,
+                                    int>::type = 0>
+  void Read(T* value) const ABSL_LOCKS_EXCLUDED(*DataGuard()) {
+    *value = absl::bit_cast<FlagValueAndInitBit<T>>(ReadOneWord()).value;
+  }
+
+  // Mutating access methods
+  void Write(const void* src) ABSL_LOCKS_EXCLUDED(*DataGuard());
+
+  // Interfaces to operate on callbacks.
+  void SetCallback(const FlagCallbackFunc mutation_callback)
+      ABSL_LOCKS_EXCLUDED(*DataGuard());
+  void InvokeCallback() const ABSL_EXCLUSIVE_LOCKS_REQUIRED(*DataGuard());
+
+  // Used in read/write operations to validate source/target has correct type.
+  // For example if flag is declared as absl::Flag<int> FLAGS_foo, a call to
+  // absl::GetFlag(FLAGS_foo) validates that the type of FLAGS_foo is indeed
+  // int. To do that we pass the "assumed" type id (which is deduced from type
+  // int) as an argument `type_id`, which is in turn is validated against the
+  // type id stored in flag object by flag definition statement.
+  void AssertValidType(FlagFastTypeId type_id,
+                       const std::type_info* (*gen_rtti)()) const;
+
+ private:
+  template <typename T>
+  friend class Flag;
+  friend class FlagState;
+
+  // Ensures that `data_guard_` is initialized and returns it.
+  absl::Mutex* DataGuard() const
+      ABSL_LOCK_RETURNED(reinterpret_cast<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());
+  // Flag initialization called via absl::call_once.
+  void Init();
+
+  // Offset value access methods. One per storage kind. These methods to not
+  // respect const correctness, so be very carefull using them.
+
+  // This is a shared helper routine which encapsulates most of the magic. Since
+  // it is only used inside the three routines below, which are defined in
+  // flag.cc, we can define it in that file as well.
+  template <typename StorageT>
+  StorageT* OffsetValue() const;
+  // This is an accessor for a value stored in an aligned buffer storage
+  // used for non-trivially-copyable data types.
+  // Returns a mutable pointer to the start of a buffer.
+  void* AlignedBufferValue() const;
+
+  // The same as above, but used for sequencelock-protected storage.
+  std::atomic<uint64_t>* AtomicBufferValue() const;
+
+  // This is an accessor for a value stored as one word atomic. Returns a
+  // mutable reference to an atomic value.
+  std::atomic<int64_t>& OneWordValue() const;
+
+  // Attempts to parse supplied `value` string. If parsing is successful,
+  // returns new value. Otherwise returns nullptr.
+  std::unique_ptr<void, DynValueDeleter> TryParse(absl::string_view value,
+                                                  std::string& err) const
+      ABSL_EXCLUSIVE_LOCKS_REQUIRED(*DataGuard());
+  // Stores the flag value based on the pointer to the source.
+  void StoreValue(const void* src) ABSL_EXCLUSIVE_LOCKS_REQUIRED(*DataGuard());
+
+  // Copy the flag data, protected by `seq_lock_` into `dst`.
+  //
+  // REQUIRES: ValueStorageKind() == kSequenceLocked.
+  void ReadSequenceLockedData(void* dst) const
+      ABSL_LOCKS_EXCLUDED(*DataGuard());
+
+  FlagHelpKind HelpSourceKind() const {
+    return static_cast<FlagHelpKind>(help_source_kind_);
+  }
+  FlagValueStorageKind ValueStorageKind() const {
+    return static_cast<FlagValueStorageKind>(value_storage_kind_);
+  }
+  FlagDefaultKind DefaultKind() const
+      ABSL_EXCLUSIVE_LOCKS_REQUIRED(*DataGuard()) {
+    return static_cast<FlagDefaultKind>(def_kind_);
+  }
+
+  // CommandLineFlag interface implementation
+  absl::string_view Name() const override;
+  std::string Filename() const override;
+  std::string Help() const override;
+  FlagFastTypeId TypeId() const override;
+  bool IsSpecifiedOnCommandLine() const override
+      ABSL_LOCKS_EXCLUDED(*DataGuard());
+  std::string DefaultValue() const override ABSL_LOCKS_EXCLUDED(*DataGuard());
+  std::string CurrentValue() const override ABSL_LOCKS_EXCLUDED(*DataGuard());
+  bool ValidateInputValue(absl::string_view value) const override
+      ABSL_LOCKS_EXCLUDED(*DataGuard());
+  void CheckDefaultValueParsingRoundtrip() const override
+      ABSL_LOCKS_EXCLUDED(*DataGuard());
+
+  int64_t ModificationCount() const ABSL_EXCLUSIVE_LOCKS_REQUIRED(*DataGuard());
+
+  // Interfaces to save and restore flags to/from persistent state.
+  // Returns current flag state or nullptr if flag does not support
+  // saving and restoring a state.
+  std::unique_ptr<FlagStateInterface> SaveState() override
+      ABSL_LOCKS_EXCLUDED(*DataGuard());
+
+  // Restores the flag state to the supplied state object. If there is
+  // nothing to restore returns false. Otherwise returns true.
+  bool RestoreState(const FlagState& flag_state)
+      ABSL_LOCKS_EXCLUDED(*DataGuard());
+
+  bool ParseFrom(absl::string_view value, FlagSettingMode set_mode,
+                 ValueSource source, std::string& error) override
+      ABSL_LOCKS_EXCLUDED(*DataGuard());
+
+  // Immutable flag's state.
+
+  // Flags name passed to ABSL_FLAG as second arg.
+  const char* const name_;
+  // The file name where ABSL_FLAG resides.
+  const char* const filename_;
+  // Type-specific operations "vtable".
+  const FlagOpFn op_;
+  // Help message literal or function to generate it.
+  const FlagHelpMsg help_;
+  // Indicates if help message was supplied as literal or generator func.
+  const uint8_t help_source_kind_ : 1;
+  // Kind of storage this flag is using for the flag's value.
+  const uint8_t value_storage_kind_ : 2;
+
+  uint8_t : 0;  // The bytes containing the const bitfields must not be
+                // shared with bytes containing the mutable bitfields.
+
+  // Mutable flag's state (guarded by `data_guard_`).
+
+  // def_kind_ is not guard by DataGuard() since it is accessed in Init without
+  // locks.
+  uint8_t def_kind_ : 2;
+  // Has this flag's value been modified?
+  bool modified_ : 1 ABSL_GUARDED_BY(*DataGuard());
+  // Has this flag been specified on command line.
+  bool on_command_line_ : 1 ABSL_GUARDED_BY(*DataGuard());
+
+  // Unique tag for absl::call_once call to initialize this flag.
+  absl::once_flag init_control_;
+
+  // Sequence lock / mutation counter.
+  flags_internal::SequenceLock seq_lock_;
+
+  // Optional flag's callback and absl::Mutex to guard the invocations.
+  FlagCallback* callback_ ABSL_GUARDED_BY(*DataGuard());
+  // Either a pointer to the function generating the default value based on the
+  // value specified in ABSL_FLAG or pointer to the dynamically set default
+  // value via SetCommandLineOptionWithMode. def_kind_ is used to distinguish
+  // these two cases.
+  FlagDefaultSrc default_value_;
+
+  // 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)];
+};
+
+///////////////////////////////////////////////////////////////////////////////
+// The Flag object parameterized by the flag's value type. This class implements
+// flag reflection handle interface.
+
+template <typename T>
+class Flag {
+ public:
+  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_arg),
+        value_() {}
+
+  // CommandLineFlag interface
+  absl::string_view Name() const { return impl_.Name(); }
+  std::string Filename() const { return impl_.Filename(); }
+  std::string Help() const { return impl_.Help(); }
+  // Do not use. To be removed.
+  bool IsSpecifiedOnCommandLine() const {
+    return impl_.IsSpecifiedOnCommandLine();
+  }
+  std::string DefaultValue() const { return impl_.DefaultValue(); }
+  std::string CurrentValue() const { return impl_.CurrentValue(); }
+
+ private:
+  template <typename, bool>
+  friend class FlagRegistrar;
+  friend class FlagImplPeer;
+
+  T Get() const {
+    // See implementation notes in CommandLineFlag::Get().
+    union U {
+      T value;
+      U() {}
+      ~U() { value.~T(); }
+    };
+    U u;
+
+#if !defined(NDEBUG)
+    impl_.AssertValidType(base_internal::FastTypeId<T>(), &GenRuntimeTypeId<T>);
+#endif
+
+    if (ABSL_PREDICT_FALSE(!value_.Get(impl_.seq_lock_, u.value))) {
+      impl_.Read(&u.value);
+    }
+    return std::move(u.value);
+  }
+  void Set(const T& v) {
+    impl_.AssertValidType(base_internal::FastTypeId<T>(), &GenRuntimeTypeId<T>);
+    impl_.Write(&v);
+  }
+
+  // Access to the reflection.
+  const CommandLineFlag& Reflect() const { return impl_; }
+
+  // Flag's data
+  // The implementation depends on value_ field to be placed exactly after the
+  // impl_ field, so that impl_ can figure out the offset to the value and
+  // access it.
+  FlagImpl impl_;
+  FlagValue<T> value_;
+};
+
+///////////////////////////////////////////////////////////////////////////////
+// Trampoline for friend access
+
+class FlagImplPeer {
+ public:
+  template <typename T, typename FlagType>
+  static T InvokeGet(const FlagType& flag) {
+    return flag.Get();
+  }
+  template <typename FlagType, typename T>
+  static void InvokeSet(FlagType& flag, const T& v) {
+    flag.Set(v);
+  }
+  template <typename FlagType>
+  static const CommandLineFlag& InvokeReflect(const FlagType& f) {
+    return f.Reflect();
+  }
+};
+
+///////////////////////////////////////////////////////////////////////////////
+// Implementation of Flag value specific operations routine.
+template <typename T>
+void* FlagOps(FlagOp op, const void* v1, void* v2, void* v3) {
+  switch (op) {
+    case FlagOp::kAlloc: {
+      std::allocator<T> alloc;
+      return std::allocator_traits<std::allocator<T>>::allocate(alloc, 1);
+    }
+    case FlagOp::kDelete: {
+      T* p = static_cast<T*>(v2);
+      p->~T();
+      std::allocator<T> alloc;
+      std::allocator_traits<std::allocator<T>>::deallocate(alloc, p, 1);
+      return nullptr;
+    }
+    case FlagOp::kCopy:
+      *static_cast<T*>(v2) = *static_cast<const T*>(v1);
+      return nullptr;
+    case FlagOp::kCopyConstruct:
+      new (v2) T(*static_cast<const T*>(v1));
+      return nullptr;
+    case FlagOp::kSizeof:
+      return reinterpret_cast<void*>(static_cast<uintptr_t>(sizeof(T)));
+    case FlagOp::kFastTypeId:
+      return const_cast<void*>(base_internal::FastTypeId<T>());
+    case FlagOp::kRuntimeTypeId:
+      return const_cast<std::type_info*>(GenRuntimeTypeId<T>());
+    case FlagOp::kParse: {
+      // Initialize the temporary instance of type T based on current value in
+      // destination (which is going to be flag's default value).
+      T temp(*static_cast<T*>(v2));
+      if (!absl::ParseFlag<T>(*static_cast<const absl::string_view*>(v1), &temp,
+                              static_cast<std::string*>(v3))) {
+        return nullptr;
+      }
+      *static_cast<T*>(v2) = std::move(temp);
+      return v2;
+    }
+    case FlagOp::kUnparse:
+      *static_cast<std::string*>(v2) =
+          absl::UnparseFlag<T>(*static_cast<const T*>(v1));
+      return nullptr;
+    case FlagOp::kValueOffset: {
+      // Round sizeof(FlagImp) to a multiple of alignof(FlagValue<T>) to get the
+      // offset of the data.
+      size_t round_to = alignof(FlagValue<T>);
+      size_t offset =
+          (sizeof(FlagImpl) + round_to - 1) / round_to * round_to;
+      return reinterpret_cast<void*>(offset);
+    }
+  }
+  return nullptr;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+// This class facilitates Flag object registration and tail expression-based
+// flag definition, for example:
+// ABSL_FLAG(int, foo, 42, "Foo help").OnUpdate(NotifyFooWatcher);
+struct FlagRegistrarEmpty {};
+template <typename T, bool do_register>
+class FlagRegistrar {
+ public:
+  explicit FlagRegistrar(Flag<T>& flag, const char* filename) : flag_(flag) {
+    if (do_register)
+      flags_internal::RegisterCommandLineFlag(flag_.impl_, filename);
+  }
+
+  FlagRegistrar OnUpdate(FlagCallbackFunc cb) && {
+    flag_.impl_.SetCallback(cb);
+    return *this;
+  }
+
+  // Make the registrar "die" gracefully as an empty struct on a line where
+  // registration happens. Registrar objects are intended to live only as
+  // temporary.
+  operator FlagRegistrarEmpty() const { return {}; }  // NOLINT
+
+ private:
+  Flag<T>& flag_;  // Flag being registered (not owned).
+};
+
+}  // namespace flags_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_FLAGS_INTERNAL_FLAG_H_

Pods/abseil/absl/flags/internal/path_util.h

@@ -0,0 +1,62 @@
+//
+//  Copyright 2019 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_FLAGS_INTERNAL_PATH_UTIL_H_
+#define ABSL_FLAGS_INTERNAL_PATH_UTIL_H_
+
+#include "absl/base/config.h"
+#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
+// argument. It is similar to basename(3)
+// <https://linux.die.net/man/3/basename>.
+// For example:
+//     flags_internal::Basename("a/b/prog/file.cc")
+// returns "file.cc"
+//     flags_internal::Basename("file.cc")
+// returns "file.cc"
+inline absl::string_view Basename(absl::string_view filename) {
+  auto last_slash_pos = filename.find_last_of("/\\");
+
+  return last_slash_pos == absl::string_view::npos
+             ? filename
+             : filename.substr(last_slash_pos + 1);
+}
+
+// A portable interface that returns the directory name of the filename
+// passed as an argument, including the trailing slash.
+// Returns the empty string if a slash is not found in the input file name.
+// For example:
+//      flags_internal::Package("a/b/prog/file.cc")
+// returns "a/b/prog/"
+//      flags_internal::Package("file.cc")
+// returns ""
+inline absl::string_view Package(absl::string_view filename) {
+  auto last_slash_pos = filename.find_last_of("/\\");
+
+  return last_slash_pos == absl::string_view::npos
+             ? absl::string_view()
+             : filename.substr(0, last_slash_pos + 1);
+}
+
+}  // namespace flags_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_FLAGS_INTERNAL_PATH_UTIL_H_

Pods/abseil/absl/flags/internal/private_handle_accessor.cc

@@ -0,0 +1,65 @@
+//
+// Copyright 2020 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/flags/internal/private_handle_accessor.h"
+
+#include <memory>
+#include <string>
+
+#include "absl/base/config.h"
+#include "absl/flags/commandlineflag.h"
+#include "absl/flags/internal/commandlineflag.h"
+#include "absl/strings/string_view.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace flags_internal {
+
+FlagFastTypeId PrivateHandleAccessor::TypeId(const CommandLineFlag& flag) {
+  return flag.TypeId();
+}
+
+std::unique_ptr<FlagStateInterface> PrivateHandleAccessor::SaveState(
+    CommandLineFlag& flag) {
+  return flag.SaveState();
+}
+
+bool PrivateHandleAccessor::IsSpecifiedOnCommandLine(
+    const CommandLineFlag& flag) {
+  return flag.IsSpecifiedOnCommandLine();
+}
+
+bool PrivateHandleAccessor::ValidateInputValue(const CommandLineFlag& flag,
+                                               absl::string_view value) {
+  return flag.ValidateInputValue(value);
+}
+
+void PrivateHandleAccessor::CheckDefaultValueParsingRoundtrip(
+    const CommandLineFlag& flag) {
+  flag.CheckDefaultValueParsingRoundtrip();
+}
+
+bool PrivateHandleAccessor::ParseFrom(CommandLineFlag& flag,
+                                      absl::string_view value,
+                                      flags_internal::FlagSettingMode set_mode,
+                                      flags_internal::ValueSource source,
+                                      std::string& error) {
+  return flag.ParseFrom(value, set_mode, source, error);
+}
+
+}  // namespace flags_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+

Pods/abseil/absl/flags/internal/private_handle_accessor.h

@@ -0,0 +1,61 @@
+//
+// Copyright 2020 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_FLAGS_INTERNAL_PRIVATE_HANDLE_ACCESSOR_H_
+#define ABSL_FLAGS_INTERNAL_PRIVATE_HANDLE_ACCESSOR_H_
+
+#include <memory>
+#include <string>
+
+#include "absl/base/config.h"
+#include "absl/flags/commandlineflag.h"
+#include "absl/flags/internal/commandlineflag.h"
+#include "absl/strings/string_view.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace flags_internal {
+
+// This class serves as a trampoline to access private methods of
+// CommandLineFlag. This class is intended for use exclusively internally inside
+// of the Abseil Flags implementation.
+class PrivateHandleAccessor {
+ public:
+  // Access to CommandLineFlag::TypeId.
+  static FlagFastTypeId TypeId(const CommandLineFlag& flag);
+
+  // Access to CommandLineFlag::SaveState.
+  static std::unique_ptr<FlagStateInterface> SaveState(CommandLineFlag& flag);
+
+  // Access to CommandLineFlag::IsSpecifiedOnCommandLine.
+  static bool IsSpecifiedOnCommandLine(const CommandLineFlag& flag);
+
+  // Access to CommandLineFlag::ValidateInputValue.
+  static bool ValidateInputValue(const CommandLineFlag& flag,
+                                 absl::string_view value);
+
+  // Access to CommandLineFlag::CheckDefaultValueParsingRoundtrip.
+  static void CheckDefaultValueParsingRoundtrip(const CommandLineFlag& flag);
+
+  static bool ParseFrom(CommandLineFlag& flag, absl::string_view value,
+                        flags_internal::FlagSettingMode set_mode,
+                        flags_internal::ValueSource source, std::string& error);
+};
+
+}  // namespace flags_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_FLAGS_INTERNAL_PRIVATE_HANDLE_ACCESSOR_H_

Pods/abseil/absl/flags/internal/program_name.cc

@@ -0,0 +1,60 @@
+//
+//  Copyright 2019 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/flags/internal/program_name.h"
+
+#include <string>
+
+#include "absl/base/attributes.h"
+#include "absl/base/config.h"
+#include "absl/base/const_init.h"
+#include "absl/base/thread_annotations.h"
+#include "absl/flags/internal/path_util.h"
+#include "absl/strings/string_view.h"
+#include "absl/synchronization/mutex.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace flags_internal {
+
+ABSL_CONST_INIT static absl::Mutex program_name_guard(absl::kConstInit);
+ABSL_CONST_INIT static std::string* program_name
+    ABSL_GUARDED_BY(program_name_guard) = nullptr;
+
+std::string ProgramInvocationName() {
+  absl::MutexLock l(&program_name_guard);
+
+  return program_name ? *program_name : "UNKNOWN";
+}
+
+std::string ShortProgramInvocationName() {
+  absl::MutexLock l(&program_name_guard);
+
+  return program_name ? std::string(flags_internal::Basename(*program_name))
+                      : "UNKNOWN";
+}
+
+void SetProgramInvocationName(absl::string_view prog_name_str) {
+  absl::MutexLock l(&program_name_guard);
+
+  if (!program_name)
+    program_name = new std::string(prog_name_str);
+  else
+    program_name->assign(prog_name_str.data(), prog_name_str.size());
+}
+
+}  // namespace flags_internal
+ABSL_NAMESPACE_END
+}  // namespace absl

Pods/abseil/absl/flags/internal/program_name.h

@@ -0,0 +1,50 @@
+//
+//  Copyright 2019 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_FLAGS_INTERNAL_PROGRAM_NAME_H_
+#define ABSL_FLAGS_INTERNAL_PROGRAM_NAME_H_
+
+#include <string>
+
+#include "absl/base/config.h"
+#include "absl/strings/string_view.h"
+
+// --------------------------------------------------------------------
+// Program name
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace flags_internal {
+
+// Returns program invocation name or "UNKNOWN" if `SetProgramInvocationName()`
+// is never called. At the moment this is always set to argv[0] as part of
+// library initialization.
+std::string ProgramInvocationName();
+
+// Returns base name for program invocation name. For example, if
+//   ProgramInvocationName() == "a/b/mybinary"
+// then
+//   ShortProgramInvocationName() == "mybinary"
+std::string ShortProgramInvocationName();
+
+// Sets program invocation name to a new value. Should only be called once
+// during program initialization, before any threads are spawned.
+void SetProgramInvocationName(absl::string_view prog_name_str);
+
+}  // namespace flags_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_FLAGS_INTERNAL_PROGRAM_NAME_H_

Pods/abseil/absl/flags/internal/registry.h

@@ -0,0 +1,97 @@
+//
+// Copyright 2019 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_FLAGS_INTERNAL_REGISTRY_H_
+#define ABSL_FLAGS_INTERNAL_REGISTRY_H_
+
+#include <functional>
+
+#include "absl/base/config.h"
+#include "absl/flags/commandlineflag.h"
+#include "absl/flags/internal/commandlineflag.h"
+#include "absl/strings/string_view.h"
+
+// --------------------------------------------------------------------
+// Global flags registry API.
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace flags_internal {
+
+// Executes specified visitor for each non-retired flag in the registry. While
+// callback are executed, the registry is locked and can't be changed.
+void ForEachFlag(std::function<void(CommandLineFlag&)> visitor);
+
+//-----------------------------------------------------------------------------
+
+bool RegisterCommandLineFlag(CommandLineFlag&, const char* filename);
+
+void FinalizeRegistry();
+
+//-----------------------------------------------------------------------------
+// Retired registrations:
+//
+// Retired flag registrations are treated specially. A 'retired' flag is
+// provided only for compatibility with automated invocations that still
+// name it.  A 'retired' flag:
+//   - is not bound to a C++ FLAGS_ reference.
+//   - has a type and a value, but that value is intentionally inaccessible.
+//   - does not appear in --help messages.
+//   - is fully supported by _all_ flag parsing routines.
+//   - consumes args normally, and complains about type mismatches in its
+//     argument.
+//   - emits a complaint but does not die (e.g. LOG(ERROR)) if it is
+//     accessed by name through the flags API for parsing or otherwise.
+//
+// The registrations for a flag happen in an unspecified order as the
+// initializers for the namespace-scope objects of a program are run.
+// Any number of weak registrations for a flag can weakly define the flag.
+// One non-weak registration will upgrade the flag from weak to non-weak.
+// Further weak registrations of a non-weak flag are ignored.
+//
+// This mechanism is designed to support moving dead flags into a
+// 'graveyard' library.  An example migration:
+//
+//   0: Remove references to this FLAGS_flagname in the C++ codebase.
+//   1: Register as 'retired' in old_lib.
+//   2: Make old_lib depend on graveyard.
+//   3: Add a redundant 'retired' registration to graveyard.
+//   4: Remove the old_lib 'retired' registration.
+//   5: Eventually delete the graveyard registration entirely.
+//
+
+// Retire flag with name "name" and type indicated by ops.
+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>
+class RetiredFlag {
+ public:
+  void Retire(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
+}  // namespace absl
+
+#endif  // ABSL_FLAGS_INTERNAL_REGISTRY_H_

Pods/abseil/absl/flags/internal/sequence_lock.h

@@ -0,0 +1,187 @@
+//
+// Copyright 2020 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_FLAGS_INTERNAL_SEQUENCE_LOCK_H_
+#define ABSL_FLAGS_INTERNAL_SEQUENCE_LOCK_H_
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include <atomic>
+#include <cassert>
+#include <cstring>
+
+#include "absl/base/optimization.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace flags_internal {
+
+// Align 'x' up to the nearest 'align' bytes.
+inline constexpr size_t AlignUp(size_t x, size_t align) {
+  return align * ((x + align - 1) / align);
+}
+
+// A SequenceLock implements lock-free reads. A sequence counter is incremented
+// before and after each write, and readers access the counter before and after
+// accessing the protected data. If the counter is verified to not change during
+// the access, and the sequence counter value was even, then the reader knows
+// that the read was race-free and valid. Otherwise, the reader must fall back
+// to a Mutex-based code path.
+//
+// This particular SequenceLock starts in an "uninitialized" state in which
+// TryRead() returns false. It must be enabled by calling MarkInitialized().
+// This serves as a marker that the associated flag value has not yet been
+// initialized and a slow path needs to be taken.
+//
+// The memory reads and writes protected by this lock must use the provided
+// `TryRead()` and `Write()` functions. These functions behave similarly to
+// `memcpy()`, with one oddity: the protected data must be an array of
+// `std::atomic<uint64>`. This is to comply with the C++ standard, which
+// considers data races on non-atomic objects to be undefined behavior. See "Can
+// Seqlocks Get Along With Programming Language Memory Models?"[1] by Hans J.
+// Boehm for more details.
+//
+// [1] https://www.hpl.hp.com/techreports/2012/HPL-2012-68.pdf
+class SequenceLock {
+ public:
+  constexpr SequenceLock() : lock_(kUninitialized) {}
+
+  // Mark that this lock is ready for use.
+  void MarkInitialized() {
+    assert(lock_.load(std::memory_order_relaxed) == kUninitialized);
+    lock_.store(0, std::memory_order_release);
+  }
+
+  // Copy "size" bytes of data from "src" to "dst", protected as a read-side
+  // critical section of the sequence lock.
+  //
+  // Unlike traditional sequence lock implementations which loop until getting a
+  // clean read, this implementation returns false in the case of concurrent
+  // calls to `Write`. In such a case, the caller should fall back to a
+  // locking-based slow path.
+  //
+  // Returns false if the sequence lock was not yet marked as initialized.
+  //
+  // NOTE: If this returns false, "dst" may be overwritten with undefined
+  // (potentially uninitialized) data.
+  bool TryRead(void* dst, const std::atomic<uint64_t>* src, size_t size) const {
+    // Acquire barrier ensures that no loads done by f() are reordered
+    // above the first load of the sequence counter.
+    int64_t seq_before = lock_.load(std::memory_order_acquire);
+    if (ABSL_PREDICT_FALSE(seq_before & 1) == 1) return false;
+    RelaxedCopyFromAtomic(dst, src, size);
+    // Another acquire fence ensures that the load of 'lock_' below is
+    // strictly ordered after the RelaxedCopyToAtomic call above.
+    std::atomic_thread_fence(std::memory_order_acquire);
+    int64_t seq_after = lock_.load(std::memory_order_relaxed);
+    return ABSL_PREDICT_TRUE(seq_before == seq_after);
+  }
+
+  // Copy "size" bytes from "src" to "dst" as a write-side critical section
+  // of the sequence lock. Any concurrent readers will be forced to retry
+  // until they get a read that does not conflict with this write.
+  //
+  // This call must be externally synchronized against other calls to Write,
+  // but may proceed concurrently with reads.
+  void Write(std::atomic<uint64_t>* dst, const void* src, size_t size) {
+    // We can use relaxed instructions to increment the counter since we
+    // are extenally synchronized. The std::atomic_thread_fence below
+    // ensures that the counter updates don't get interleaved with the
+    // copy to the data.
+    int64_t orig_seq = lock_.load(std::memory_order_relaxed);
+    assert((orig_seq & 1) == 0);  // Must be initially unlocked.
+    lock_.store(orig_seq + 1, std::memory_order_relaxed);
+
+    // We put a release fence between update to lock_ and writes to shared data.
+    // Thus all stores to shared data are effectively release operations and
+    // update to lock_ above cannot be re-ordered past any of them. Note that
+    // this barrier is not for the fetch_add above.  A release barrier for the
+    // fetch_add would be before it, not after.
+    std::atomic_thread_fence(std::memory_order_release);
+    RelaxedCopyToAtomic(dst, src, size);
+    // "Release" semantics ensure that none of the writes done by
+    // RelaxedCopyToAtomic() can be reordered after the following modification.
+    lock_.store(orig_seq + 2, std::memory_order_release);
+  }
+
+  // Return the number of times that Write() has been called.
+  //
+  // REQUIRES: This must be externally synchronized against concurrent calls to
+  // `Write()` or `IncrementModificationCount()`.
+  // REQUIRES: `MarkInitialized()` must have been previously called.
+  int64_t ModificationCount() const {
+    int64_t val = lock_.load(std::memory_order_relaxed);
+    assert(val != kUninitialized && (val & 1) == 0);
+    return val / 2;
+  }
+
+  // REQUIRES: This must be externally synchronized against concurrent calls to
+  // `Write()` or `ModificationCount()`.
+  // REQUIRES: `MarkInitialized()` must have been previously called.
+  void IncrementModificationCount() {
+    int64_t val = lock_.load(std::memory_order_relaxed);
+    assert(val != kUninitialized);
+    lock_.store(val + 2, std::memory_order_relaxed);
+  }
+
+ private:
+  // Perform the equivalent of "memcpy(dst, src, size)", but using relaxed
+  // atomics.
+  static void RelaxedCopyFromAtomic(void* dst, const std::atomic<uint64_t>* src,
+                                    size_t size) {
+    char* dst_byte = static_cast<char*>(dst);
+    while (size >= sizeof(uint64_t)) {
+      uint64_t word = src->load(std::memory_order_relaxed);
+      std::memcpy(dst_byte, &word, sizeof(word));
+      dst_byte += sizeof(word);
+      src++;
+      size -= sizeof(word);
+    }
+    if (size > 0) {
+      uint64_t word = src->load(std::memory_order_relaxed);
+      std::memcpy(dst_byte, &word, size);
+    }
+  }
+
+  // Perform the equivalent of "memcpy(dst, src, size)", but using relaxed
+  // atomics.
+  static void RelaxedCopyToAtomic(std::atomic<uint64_t>* dst, const void* src,
+                                  size_t size) {
+    const char* src_byte = static_cast<const char*>(src);
+    while (size >= sizeof(uint64_t)) {
+      uint64_t word;
+      std::memcpy(&word, src_byte, sizeof(word));
+      dst->store(word, std::memory_order_relaxed);
+      src_byte += sizeof(word);
+      dst++;
+      size -= sizeof(word);
+    }
+    if (size > 0) {
+      uint64_t word = 0;
+      std::memcpy(&word, src_byte, size);
+      dst->store(word, std::memory_order_relaxed);
+    }
+  }
+
+  static constexpr int64_t kUninitialized = -1;
+  std::atomic<int64_t> lock_;
+};
+
+}  // namespace flags_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_FLAGS_INTERNAL_SEQUENCE_LOCK_H_

Pods/abseil/absl/flags/marshalling.cc

@@ -0,0 +1,291 @@
+//
+//  Copyright 2019 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/flags/marshalling.h"
+
+#include <stddef.h>
+
+#include <cmath>
+#include <limits>
+#include <sstream>
+#include <string>
+#include <type_traits>
+#include <vector>
+
+#include "absl/base/config.h"
+#include "absl/base/log_severity.h"
+#include "absl/base/macros.h"
+#include "absl/numeric/int128.h"
+#include "absl/strings/ascii.h"
+#include "absl/strings/match.h"
+#include "absl/strings/numbers.h"
+#include "absl/strings/str_cat.h"
+#include "absl/strings/str_format.h"
+#include "absl/strings/str_join.h"
+#include "absl/strings/str_split.h"
+#include "absl/strings/string_view.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace flags_internal {
+
+// --------------------------------------------------------------------
+// AbslParseFlag specializations for boolean type.
+
+bool AbslParseFlag(absl::string_view text, bool* dst, std::string*) {
+  const char* kTrue[] = {"1", "t", "true", "y", "yes"};
+  const char* kFalse[] = {"0", "f", "false", "n", "no"};
+  static_assert(sizeof(kTrue) == sizeof(kFalse), "true_false_equal");
+
+  text = absl::StripAsciiWhitespace(text);
+
+  for (size_t i = 0; i < ABSL_ARRAYSIZE(kTrue); ++i) {
+    if (absl::EqualsIgnoreCase(text, kTrue[i])) {
+      *dst = true;
+      return true;
+    } else if (absl::EqualsIgnoreCase(text, kFalse[i])) {
+      *dst = false;
+      return true;
+    }
+  }
+  return false;  // didn't match a legal input
+}
+
+// --------------------------------------------------------------------
+// AbslParseFlag for integral types.
+
+// Return the base to use for parsing text as an integer.  Leading 0x
+// puts us in base 16.  But leading 0 does not put us in base 8. It
+// caused too many bugs when we had that behavior.
+static int NumericBase(absl::string_view text) {
+  if (text.empty()) return 0;
+  size_t num_start = (text[0] == '-' || text[0] == '+') ? 1 : 0;
+  const bool hex = (text.size() >= num_start + 2 && text[num_start] == '0' &&
+                    (text[num_start + 1] == 'x' || text[num_start + 1] == 'X'));
+  return hex ? 16 : 10;
+}
+
+template <typename IntType>
+inline bool ParseFlagImpl(absl::string_view text, IntType& dst) {
+  text = absl::StripAsciiWhitespace(text);
+
+  return absl::numbers_internal::safe_strtoi_base(text, &dst,
+                                                  NumericBase(text));
+}
+
+bool AbslParseFlag(absl::string_view text, short* dst, std::string*) {
+  int val;
+  if (!ParseFlagImpl(text, val)) return false;
+  if (static_cast<short>(val) != val)  // worked, but number out of range
+    return false;
+  *dst = static_cast<short>(val);
+  return true;
+}
+
+bool AbslParseFlag(absl::string_view text, unsigned short* dst, std::string*) {
+  unsigned int val;
+  if (!ParseFlagImpl(text, val)) return false;
+  if (static_cast<unsigned short>(val) !=
+      val)  // worked, but number out of range
+    return false;
+  *dst = static_cast<unsigned short>(val);
+  return true;
+}
+
+bool AbslParseFlag(absl::string_view text, int* dst, std::string*) {
+  return ParseFlagImpl(text, *dst);
+}
+
+bool AbslParseFlag(absl::string_view text, unsigned int* dst, std::string*) {
+  return ParseFlagImpl(text, *dst);
+}
+
+bool AbslParseFlag(absl::string_view text, long* dst, std::string*) {
+  return ParseFlagImpl(text, *dst);
+}
+
+bool AbslParseFlag(absl::string_view text, unsigned long* dst, std::string*) {
+  return ParseFlagImpl(text, *dst);
+}
+
+bool AbslParseFlag(absl::string_view text, long long* dst, std::string*) {
+  return ParseFlagImpl(text, *dst);
+}
+
+bool AbslParseFlag(absl::string_view text, unsigned long long* dst,
+                   std::string*) {
+  return ParseFlagImpl(text, *dst);
+}
+
+bool AbslParseFlag(absl::string_view text, absl::int128* dst, std::string*) {
+  text = absl::StripAsciiWhitespace(text);
+
+  // check hex
+  int base = NumericBase(text);
+  if (!absl::numbers_internal::safe_strto128_base(text, dst, base)) {
+    return false;
+  }
+
+  return base == 16 ? absl::SimpleHexAtoi(text, dst)
+                    : absl::SimpleAtoi(text, dst);
+}
+
+bool AbslParseFlag(absl::string_view text, absl::uint128* dst, std::string*) {
+  text = absl::StripAsciiWhitespace(text);
+
+  // check hex
+  int base = NumericBase(text);
+  if (!absl::numbers_internal::safe_strtou128_base(text, dst, base)) {
+    return false;
+  }
+
+  return base == 16 ? absl::SimpleHexAtoi(text, dst)
+                    : absl::SimpleAtoi(text, dst);
+}
+
+// --------------------------------------------------------------------
+// AbslParseFlag for floating point types.
+
+bool AbslParseFlag(absl::string_view text, float* dst, std::string*) {
+  return absl::SimpleAtof(text, dst);
+}
+
+bool AbslParseFlag(absl::string_view text, double* dst, std::string*) {
+  return absl::SimpleAtod(text, dst);
+}
+
+// --------------------------------------------------------------------
+// AbslParseFlag for strings.
+
+bool AbslParseFlag(absl::string_view text, std::string* dst, std::string*) {
+  dst->assign(text.data(), text.size());
+  return true;
+}
+
+// --------------------------------------------------------------------
+// AbslParseFlag for vector of strings.
+
+bool AbslParseFlag(absl::string_view text, std::vector<std::string>* dst,
+                   std::string*) {
+  // An empty flag value corresponds to an empty vector, not a vector
+  // with a single, empty std::string.
+  if (text.empty()) {
+    dst->clear();
+    return true;
+  }
+  *dst = absl::StrSplit(text, ',', absl::AllowEmpty());
+  return true;
+}
+
+// --------------------------------------------------------------------
+// AbslUnparseFlag specializations for various builtin flag types.
+
+std::string Unparse(bool v) { return v ? "true" : "false"; }
+std::string Unparse(short v) { return absl::StrCat(v); }
+std::string Unparse(unsigned short v) { return absl::StrCat(v); }
+std::string Unparse(int v) { return absl::StrCat(v); }
+std::string Unparse(unsigned int v) { return absl::StrCat(v); }
+std::string Unparse(long v) { return absl::StrCat(v); }
+std::string Unparse(unsigned long v) { return absl::StrCat(v); }
+std::string Unparse(long long v) { return absl::StrCat(v); }
+std::string Unparse(unsigned long long v) { return absl::StrCat(v); }
+std::string Unparse(absl::int128 v) {
+  std::stringstream ss;
+  ss << v;
+  return ss.str();
+}
+std::string Unparse(absl::uint128 v) {
+  std::stringstream ss;
+  ss << v;
+  return ss.str();
+}
+
+template <typename T>
+std::string UnparseFloatingPointVal(T v) {
+  // digits10 is guaranteed to roundtrip correctly in string -> value -> string
+  // conversions, but may not be enough to represent all the values correctly.
+  std::string digit10_str =
+      absl::StrFormat("%.*g", std::numeric_limits<T>::digits10, v);
+  if (std::isnan(v) || std::isinf(v)) return digit10_str;
+
+  T roundtrip_val = 0;
+  std::string err;
+  if (absl::ParseFlag(digit10_str, &roundtrip_val, &err) &&
+      roundtrip_val == v) {
+    return digit10_str;
+  }
+
+  // max_digits10 is the number of base-10 digits that are necessary to uniquely
+  // represent all distinct values.
+  return absl::StrFormat("%.*g", std::numeric_limits<T>::max_digits10, v);
+}
+std::string Unparse(float v) { return UnparseFloatingPointVal(v); }
+std::string Unparse(double v) { return UnparseFloatingPointVal(v); }
+std::string AbslUnparseFlag(absl::string_view v) { return std::string(v); }
+std::string AbslUnparseFlag(const std::vector<std::string>& v) {
+  return absl::StrJoin(v, ",");
+}
+
+}  // namespace flags_internal
+
+bool AbslParseFlag(absl::string_view text, absl::LogSeverity* dst,
+                   std::string* err) {
+  text = absl::StripAsciiWhitespace(text);
+  if (text.empty()) {
+    *err = "no value provided";
+    return false;
+  }
+  if (absl::EqualsIgnoreCase(text, "dfatal")) {
+    *dst = absl::kLogDebugFatal;
+    return true;
+  }
+  if (absl::EqualsIgnoreCase(text, "klogdebugfatal")) {
+    *dst = absl::kLogDebugFatal;
+    return true;
+  }
+  if (text.front() == 'k' || text.front() == 'K') text.remove_prefix(1);
+  if (absl::EqualsIgnoreCase(text, "info")) {
+    *dst = absl::LogSeverity::kInfo;
+    return true;
+  }
+  if (absl::EqualsIgnoreCase(text, "warning")) {
+    *dst = absl::LogSeverity::kWarning;
+    return true;
+  }
+  if (absl::EqualsIgnoreCase(text, "error")) {
+    *dst = absl::LogSeverity::kError;
+    return true;
+  }
+  if (absl::EqualsIgnoreCase(text, "fatal")) {
+    *dst = absl::LogSeverity::kFatal;
+    return true;
+  }
+  std::underlying_type<absl::LogSeverity>::type numeric_value;
+  if (absl::ParseFlag(text, &numeric_value, err)) {
+    *dst = static_cast<absl::LogSeverity>(numeric_value);
+    return true;
+  }
+  *err =
+      "only integers, absl::LogSeverity enumerators, and DFATAL are accepted";
+  return false;
+}
+
+std::string AbslUnparseFlag(absl::LogSeverity v) {
+  if (v == absl::NormalizeLogSeverity(v)) return absl::LogSeverityName(v);
+  return absl::UnparseFlag(static_cast<int>(v));
+}
+
+ABSL_NAMESPACE_END
+}  // namespace absl

Pods/abseil/absl/flags/marshalling.h

@@ -0,0 +1,361 @@
+//
+//  Copyright 2019 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// -----------------------------------------------------------------------------
+// File: marshalling.h
+// -----------------------------------------------------------------------------
+//
+// This header file defines the API for extending Abseil flag support to
+// custom types, and defines the set of overloads for fundamental types.
+//
+// Out of the box, the Abseil flags library supports the following types:
+//
+// * `bool`
+// * `int16_t`
+// * `uint16_t`
+// * `int32_t`
+// * `uint32_t`
+// * `int64_t`
+// * `uint64_t`
+// * `float`
+// * `double`
+// * `std::string`
+// * `std::vector<std::string>`
+// * `std::optional<T>`
+// * `absl::LogSeverity` (provided natively for layering reasons)
+//
+// Note that support for integral types is implemented using overloads for
+// variable-width fundamental types (`short`, `int`, `long`, etc.). However,
+// you should prefer the fixed-width integral types (`int32_t`, `uint64_t`,
+// etc.) we've noted above within flag definitions.
+//
+// In addition, several Abseil libraries provide their own custom support for
+// Abseil flags. Documentation for these formats is provided in the type's
+// `AbslParseFlag()` definition.
+//
+// The Abseil time library provides the following support for civil time values:
+//
+// * `absl::CivilSecond`
+// * `absl::CivilMinute`
+// * `absl::CivilHour`
+// * `absl::CivilDay`
+// * `absl::CivilMonth`
+// * `absl::CivilYear`
+//
+// and also provides support for the following absolute time values:
+//
+// * `absl::Duration`
+// * `absl::Time`
+//
+// Additional support for Abseil types will be noted here as it is added.
+//
+// You can also provide your own custom flags by adding overloads for
+// `AbslParseFlag()` and `AbslUnparseFlag()` to your type definitions. (See
+// below.)
+//
+// -----------------------------------------------------------------------------
+// Optional Flags
+// -----------------------------------------------------------------------------
+//
+// The Abseil flags library supports flags of type `std::optional<T>` where
+// `T` is a type of one of the supported flags. We refer to this flag type as
+// an "optional flag." An optional flag is either "valueless", holding no value
+// of type `T` (indicating that the flag has not been set) or a value of type
+// `T`. The valueless state in C++ code is represented by a value of
+// `std::nullopt` for the optional flag.
+//
+// Using `std::nullopt` as an optional flag's default value allows you to check
+// whether such a flag was ever specified on the command line:
+//
+//   if (absl::GetFlag(FLAGS_foo).has_value()) {
+//     // flag was set on command line
+//   } else {
+//     // flag was not passed on command line
+//   }
+//
+// Using an optional flag in this manner avoids common workarounds for
+// indicating such an unset flag (such as using sentinel values to indicate this
+// state).
+//
+// An optional flag also allows a developer to pass a flag in an "unset"
+// valueless state on the command line, allowing the flag to later be set in
+// binary logic. An optional flag's valueless state is indicated by the special
+// notation of passing the value as an empty string through the syntax `--flag=`
+// or `--flag ""`.
+//
+//   $ binary_with_optional --flag_in_unset_state=
+//   $ binary_with_optional --flag_in_unset_state ""
+//
+// Note: as a result of the above syntax requirements, an optional flag cannot
+// be set to a `T` of any value which unparses to the empty string.
+//
+// -----------------------------------------------------------------------------
+// Adding Type Support for Abseil Flags
+// -----------------------------------------------------------------------------
+//
+// To add support for your user-defined type, add overloads of `AbslParseFlag()`
+// and `AbslUnparseFlag()` as free (non-member) functions to your type. If `T`
+// is a class type, these functions can be friend function definitions. These
+// overloads must be added to the same namespace where the type is defined, so
+// that they can be discovered by Argument-Dependent Lookup (ADL).
+//
+// Example:
+//
+//   namespace foo {
+//
+//   enum OutputMode { kPlainText, kHtml };
+//
+//   // AbslParseFlag converts from a string to OutputMode.
+//   // Must be in same namespace as OutputMode.
+//
+//   // Parses an OutputMode from the command line flag value `text`. Returns
+//   // `true` and sets `*mode` on success; returns `false` and sets `*error`
+//   // on failure.
+//   bool AbslParseFlag(absl::string_view text,
+//                      OutputMode* mode,
+//                      std::string* error) {
+//     if (text == "plaintext") {
+//       *mode = kPlainText;
+//       return true;
+//     }
+//     if (text == "html") {
+//       *mode = kHtml;
+//      return true;
+//     }
+//     *error = "unknown value for enumeration";
+//     return false;
+//  }
+//
+//  // AbslUnparseFlag converts from an OutputMode to a string.
+//  // Must be in same namespace as OutputMode.
+//
+//  // Returns a textual flag value corresponding to the OutputMode `mode`.
+//  std::string AbslUnparseFlag(OutputMode mode) {
+//    switch (mode) {
+//      case kPlainText: return "plaintext";
+//      case kHtml: return "html";
+//    }
+//    return absl::StrCat(mode);
+//  }
+//
+// Notice that neither `AbslParseFlag()` nor `AbslUnparseFlag()` are class
+// members, but free functions. `AbslParseFlag/AbslUnparseFlag()` overloads
+// for a type should only be declared in the same file and namespace as said
+// type. The proper `AbslParseFlag/AbslUnparseFlag()` implementations for a
+// given type will be discovered via Argument-Dependent Lookup (ADL).
+//
+// `AbslParseFlag()` may need, in turn, to parse simpler constituent types
+// using `absl::ParseFlag()`. For example, a custom struct `MyFlagType`
+// consisting of a `std::pair<int, std::string>` would add an `AbslParseFlag()`
+// overload for its `MyFlagType` like so:
+//
+// Example:
+//
+//   namespace my_flag_type {
+//
+//   struct MyFlagType {
+//     std::pair<int, std::string> my_flag_data;
+//   };
+//
+//   bool AbslParseFlag(absl::string_view text, MyFlagType* flag,
+//                      std::string* err);
+//
+//   std::string AbslUnparseFlag(const MyFlagType&);
+//
+//   // Within the implementation, `AbslParseFlag()` will, in turn invoke
+//   // `absl::ParseFlag()` on its constituent `int` and `std::string` types
+//   // (which have built-in Abseil flag support).
+//
+//   bool AbslParseFlag(absl::string_view text, MyFlagType* flag,
+//                      std::string* err) {
+//     std::pair<absl::string_view, absl::string_view> tokens =
+//         absl::StrSplit(text, ',');
+//     if (!absl::ParseFlag(tokens.first, &flag->my_flag_data.first, err))
+//         return false;
+//     if (!absl::ParseFlag(tokens.second, &flag->my_flag_data.second, err))
+//         return false;
+//     return true;
+//   }
+//
+//   // Similarly, for unparsing, we can simply invoke `absl::UnparseFlag()` on
+//   // the constituent types.
+//   std::string AbslUnparseFlag(const MyFlagType& flag) {
+//     return absl::StrCat(absl::UnparseFlag(flag.my_flag_data.first),
+//                         ",",
+//                         absl::UnparseFlag(flag.my_flag_data.second));
+//   }
+#ifndef ABSL_FLAGS_MARSHALLING_H_
+#define ABSL_FLAGS_MARSHALLING_H_
+
+#include "absl/base/config.h"
+#include "absl/numeric/int128.h"
+
+#if defined(ABSL_HAVE_STD_OPTIONAL) && !defined(ABSL_USES_STD_OPTIONAL)
+#include <optional>
+#endif
+#include <string>
+#include <vector>
+
+#include "absl/strings/string_view.h"
+#include "absl/types/optional.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+// Forward declaration to be used inside composable flag parse/unparse
+// implementations
+template <typename T>
+inline bool ParseFlag(absl::string_view input, T* dst, std::string* error);
+template <typename T>
+inline std::string UnparseFlag(const T& v);
+
+namespace flags_internal {
+
+// Overloads of `AbslParseFlag()` and `AbslUnparseFlag()` for fundamental types.
+bool AbslParseFlag(absl::string_view, bool*, std::string*);
+bool AbslParseFlag(absl::string_view, short*, std::string*);           // NOLINT
+bool AbslParseFlag(absl::string_view, unsigned short*, std::string*);  // NOLINT
+bool AbslParseFlag(absl::string_view, int*, std::string*);             // NOLINT
+bool AbslParseFlag(absl::string_view, unsigned int*, std::string*);    // NOLINT
+bool AbslParseFlag(absl::string_view, long*, std::string*);            // NOLINT
+bool AbslParseFlag(absl::string_view, unsigned long*, std::string*);   // NOLINT
+bool AbslParseFlag(absl::string_view, long long*, std::string*);       // NOLINT
+bool AbslParseFlag(absl::string_view, unsigned long long*,             // NOLINT
+                   std::string*);
+bool AbslParseFlag(absl::string_view, absl::int128*, std::string*);    // NOLINT
+bool AbslParseFlag(absl::string_view, absl::uint128*, std::string*);   // NOLINT
+bool AbslParseFlag(absl::string_view, float*, std::string*);
+bool AbslParseFlag(absl::string_view, double*, std::string*);
+bool AbslParseFlag(absl::string_view, std::string*, std::string*);
+bool AbslParseFlag(absl::string_view, std::vector<std::string>*, std::string*);
+
+template <typename T>
+bool AbslParseFlag(absl::string_view text, absl::optional<T>* f,
+                   std::string* err) {
+  if (text.empty()) {
+    *f = absl::nullopt;
+    return true;
+  }
+  T value;
+  if (!absl::ParseFlag(text, &value, err)) return false;
+
+  *f = std::move(value);
+  return true;
+}
+
+#if defined(ABSL_HAVE_STD_OPTIONAL) && !defined(ABSL_USES_STD_OPTIONAL)
+template <typename T>
+bool AbslParseFlag(absl::string_view text, std::optional<T>* f,
+                   std::string* err) {
+  if (text.empty()) {
+    *f = std::nullopt;
+    return true;
+  }
+  T value;
+  if (!absl::ParseFlag(text, &value, err)) return false;
+
+  *f = std::move(value);
+  return true;
+}
+#endif
+
+template <typename T>
+bool InvokeParseFlag(absl::string_view input, T* dst, std::string* err) {
+  // Comment on next line provides a good compiler error message if T
+  // does not have AbslParseFlag(absl::string_view, T*, std::string*).
+  return AbslParseFlag(input, dst, err);  // Is T missing AbslParseFlag?
+}
+
+// Strings and std:: containers do not have the same overload resolution
+// considerations as fundamental types. Naming these 'AbslUnparseFlag' means we
+// can avoid the need for additional specializations of Unparse (below).
+std::string AbslUnparseFlag(absl::string_view v);
+std::string AbslUnparseFlag(const std::vector<std::string>&);
+
+template <typename T>
+std::string AbslUnparseFlag(const absl::optional<T>& f) {
+  return f.has_value() ? absl::UnparseFlag(*f) : "";
+}
+
+#if defined(ABSL_HAVE_STD_OPTIONAL) && !defined(ABSL_USES_STD_OPTIONAL)
+template <typename T>
+std::string AbslUnparseFlag(const std::optional<T>& f) {
+  return f.has_value() ? absl::UnparseFlag(*f) : "";
+}
+#endif
+
+template <typename T>
+std::string Unparse(const T& v) {
+  // Comment on next line provides a good compiler error message if T does not
+  // have UnparseFlag.
+  return AbslUnparseFlag(v);  // Is T missing AbslUnparseFlag?
+}
+
+// Overloads for builtin types.
+std::string Unparse(bool v);
+std::string Unparse(short v);               // NOLINT
+std::string Unparse(unsigned short v);      // NOLINT
+std::string Unparse(int v);                 // NOLINT
+std::string Unparse(unsigned int v);        // NOLINT
+std::string Unparse(long v);                // NOLINT
+std::string Unparse(unsigned long v);       // NOLINT
+std::string Unparse(long long v);           // NOLINT
+std::string Unparse(unsigned long long v);  // NOLINT
+std::string Unparse(absl::int128 v);
+std::string Unparse(absl::uint128 v);
+std::string Unparse(float v);
+std::string Unparse(double v);
+
+}  // namespace flags_internal
+
+// ParseFlag()
+//
+// Parses a string value into a flag value of type `T`. Do not add overloads of
+// this function for your type directly; instead, add an `AbslParseFlag()`
+// free function as documented above.
+//
+// Some implementations of `AbslParseFlag()` for types which consist of other,
+// constituent types which already have Abseil flag support, may need to call
+// `absl::ParseFlag()` on those consituent string values. (See above.)
+template <typename T>
+inline bool ParseFlag(absl::string_view input, T* dst, std::string* error) {
+  return flags_internal::InvokeParseFlag(input, dst, error);
+}
+
+// UnparseFlag()
+//
+// Unparses a flag value of type `T` into a string value. Do not add overloads
+// of this function for your type directly; instead, add an `AbslUnparseFlag()`
+// free function as documented above.
+//
+// Some implementations of `AbslUnparseFlag()` for types which consist of other,
+// constituent types which already have Abseil flag support, may want to call
+// `absl::UnparseFlag()` on those constituent types. (See above.)
+template <typename T>
+inline std::string UnparseFlag(const T& v) {
+  return flags_internal::Unparse(v);
+}
+
+// Overloads for `absl::LogSeverity` can't (easily) appear alongside that type's
+// definition because it is layered below flags.  See proper documentation in
+// base/log_severity.h.
+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_

Pods/abseil/absl/flags/reflection.cc

@@ -0,0 +1,355 @@
+//
+//  Copyright 2020 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/flags/reflection.h"
+
+#include <assert.h>
+
+#include <atomic>
+#include <string>
+
+#include "absl/base/config.h"
+#include "absl/base/no_destructor.h"
+#include "absl/base/thread_annotations.h"
+#include "absl/container/flat_hash_map.h"
+#include "absl/flags/commandlineflag.h"
+#include "absl/flags/internal/private_handle_accessor.h"
+#include "absl/flags/internal/registry.h"
+#include "absl/flags/usage_config.h"
+#include "absl/strings/str_cat.h"
+#include "absl/strings/string_view.h"
+#include "absl/synchronization/mutex.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace flags_internal {
+
+// --------------------------------------------------------------------
+// FlagRegistry
+//    A FlagRegistry singleton object holds all flag objects indexed by their
+//    names so that if you know a flag's name, you can access or set it. If the
+//    function is named FooLocked(), you must own the registry lock before
+//    calling the function; otherwise, you should *not* hold the lock, and the
+//    function will acquire it itself if needed.
+// --------------------------------------------------------------------
+
+class FlagRegistry {
+ public:
+  FlagRegistry() = default;
+  ~FlagRegistry() = default;
+
+  // Store a flag in this registry. Takes ownership of *flag.
+  void RegisterFlag(CommandLineFlag& flag, const char* filename);
+
+  void Lock() ABSL_EXCLUSIVE_LOCK_FUNCTION(lock_) { lock_.Lock(); }
+  void Unlock() ABSL_UNLOCK_FUNCTION(lock_) { lock_.Unlock(); }
+
+  // Returns the flag object for the specified name, or nullptr if not found.
+  // Will emit a warning if a 'retired' flag is specified.
+  CommandLineFlag* FindFlag(absl::string_view name);
+
+  static FlagRegistry& GlobalRegistry();  // returns a singleton registry
+
+ private:
+  friend class flags_internal::FlagSaverImpl;  // reads all the flags in order
+                                               // to copy them
+  friend void ForEachFlag(std::function<void(CommandLineFlag&)> visitor);
+  friend void FinalizeRegistry();
+
+  // The map from name to flag, for FindFlag().
+  using FlagMap = absl::flat_hash_map<absl::string_view, CommandLineFlag*>;
+  using FlagIterator = FlagMap::iterator;
+  using FlagConstIterator = FlagMap::const_iterator;
+  FlagMap flags_;
+  std::vector<CommandLineFlag*> flat_flags_;
+  std::atomic<bool> finalized_flags_{false};
+
+  absl::Mutex lock_;
+
+  // Disallow
+  FlagRegistry(const FlagRegistry&);
+  FlagRegistry& operator=(const FlagRegistry&);
+};
+
+namespace {
+
+class FlagRegistryLock {
+ public:
+  explicit FlagRegistryLock(FlagRegistry& fr) : fr_(fr) { fr_.Lock(); }
+  ~FlagRegistryLock() { fr_.Unlock(); }
+
+ private:
+  FlagRegistry& fr_;
+};
+
+}  // namespace
+
+CommandLineFlag* FlagRegistry::FindFlag(absl::string_view name) {
+  if (finalized_flags_.load(std::memory_order_acquire)) {
+    // We could save some gcus here if we make `Name()` be non-virtual.
+    // We could move the `const char*` name to the base class.
+    auto it = std::partition_point(
+        flat_flags_.begin(), flat_flags_.end(),
+        [=](CommandLineFlag* f) { return f->Name() < name; });
+    if (it != flat_flags_.end() && (*it)->Name() == name) return *it;
+  }
+
+  FlagRegistryLock frl(*this);
+  auto it = flags_.find(name);
+  return it != flags_.end() ? it->second : nullptr;
+}
+
+void FlagRegistry::RegisterFlag(CommandLineFlag& flag, const char* filename) {
+  if (filename != nullptr &&
+      flag.Filename() != GetUsageConfig().normalize_filename(filename)) {
+    flags_internal::ReportUsageError(
+        absl::StrCat(
+            "Inconsistency between flag object and registration for flag '",
+            flag.Name(),
+            "', likely due to duplicate flags or an ODR violation. Relevant "
+            "files: ",
+            flag.Filename(), " and ", filename),
+        true);
+    std::exit(1);
+  }
+
+  FlagRegistryLock registry_lock(*this);
+
+  std::pair<FlagIterator, bool> ins =
+      flags_.insert(FlagMap::value_type(flag.Name(), &flag));
+  if (ins.second == false) {  // means the name was already in the map
+    CommandLineFlag& old_flag = *ins.first->second;
+    if (flag.IsRetired() != old_flag.IsRetired()) {
+      // All registrations must agree on the 'retired' flag.
+      flags_internal::ReportUsageError(
+          absl::StrCat(
+              "Retired flag '", flag.Name(), "' was defined normally in file '",
+              (flag.IsRetired() ? old_flag.Filename() : flag.Filename()), "'."),
+          true);
+    } else if (flags_internal::PrivateHandleAccessor::TypeId(flag) !=
+               flags_internal::PrivateHandleAccessor::TypeId(old_flag)) {
+      flags_internal::ReportUsageError(
+          absl::StrCat("Flag '", flag.Name(),
+                       "' was defined more than once but with "
+                       "differing types. Defined in files '",
+                       old_flag.Filename(), "' and '", flag.Filename(), "'."),
+          true);
+    } else if (old_flag.IsRetired()) {
+      return;
+    } else if (old_flag.Filename() != flag.Filename()) {
+      flags_internal::ReportUsageError(
+          absl::StrCat("Flag '", flag.Name(),
+                       "' was defined more than once (in files '",
+                       old_flag.Filename(), "' and '", flag.Filename(), "')."),
+          true);
+    } else {
+      flags_internal::ReportUsageError(
+          absl::StrCat(
+              "Something is wrong with flag '", flag.Name(), "' in file '",
+              flag.Filename(), "'. One possibility: file '", flag.Filename(),
+              "' is being linked both statically and dynamically into this "
+              "executable. e.g. some files listed as srcs to a test and also "
+              "listed as srcs of some shared lib deps of the same test."),
+          true);
+    }
+    // All cases above are fatal, except for the retired flags.
+    std::exit(1);
+  }
+}
+
+FlagRegistry& FlagRegistry::GlobalRegistry() {
+  static absl::NoDestructor<FlagRegistry> global_registry;
+  return *global_registry;
+}
+
+// --------------------------------------------------------------------
+
+void ForEachFlag(std::function<void(CommandLineFlag&)> visitor) {
+  FlagRegistry& registry = FlagRegistry::GlobalRegistry();
+
+  if (registry.finalized_flags_.load(std::memory_order_acquire)) {
+    for (const auto& i : registry.flat_flags_) visitor(*i);
+  }
+
+  FlagRegistryLock frl(registry);
+  for (const auto& i : registry.flags_) visitor(*i.second);
+}
+
+// --------------------------------------------------------------------
+
+bool RegisterCommandLineFlag(CommandLineFlag& flag, const char* filename) {
+  FlagRegistry::GlobalRegistry().RegisterFlag(flag, filename);
+  return true;
+}
+
+void FinalizeRegistry() {
+  auto& registry = FlagRegistry::GlobalRegistry();
+  FlagRegistryLock frl(registry);
+  if (registry.finalized_flags_.load(std::memory_order_relaxed)) {
+    // Was already finalized. Ignore the second time.
+    return;
+  }
+  registry.flat_flags_.reserve(registry.flags_.size());
+  for (const auto& f : registry.flags_) {
+    registry.flat_flags_.push_back(f.second);
+  }
+  std::sort(std::begin(registry.flat_flags_), std::end(registry.flat_flags_),
+            [](const CommandLineFlag* lhs, const CommandLineFlag* rhs) {
+              return lhs->Name() < rhs->Name();
+            });
+  registry.flags_.clear();
+  registry.finalized_flags_.store(true, std::memory_order_release);
+}
+
+// --------------------------------------------------------------------
+
+namespace {
+
+class RetiredFlagObj final : public CommandLineFlag {
+ public:
+  constexpr RetiredFlagObj(const char* name, FlagFastTypeId type_id)
+      : name_(name), type_id_(type_id) {}
+
+ private:
+  absl::string_view Name() const override { return name_; }
+  std::string Filename() const override {
+    OnAccess();
+    return "RETIRED";
+  }
+  FlagFastTypeId TypeId() const override { return type_id_; }
+  std::string Help() const override {
+    OnAccess();
+    return "";
+  }
+  bool IsRetired() const override { return true; }
+  bool IsSpecifiedOnCommandLine() const override {
+    OnAccess();
+    return false;
+  }
+  std::string DefaultValue() const override {
+    OnAccess();
+    return "";
+  }
+  std::string CurrentValue() const override {
+    OnAccess();
+    return "";
+  }
+
+  // Any input is valid
+  bool ValidateInputValue(absl::string_view) const override {
+    OnAccess();
+    return true;
+  }
+
+  std::unique_ptr<flags_internal::FlagStateInterface> SaveState() override {
+    return nullptr;
+  }
+
+  bool ParseFrom(absl::string_view, flags_internal::FlagSettingMode,
+                 flags_internal::ValueSource, std::string&) override {
+    OnAccess();
+    return false;
+  }
+
+  void CheckDefaultValueParsingRoundtrip() const override { OnAccess(); }
+
+  void Read(void*) const override { OnAccess(); }
+
+  void OnAccess() const {
+    flags_internal::ReportUsageError(
+        absl::StrCat("Accessing retired flag '", name_, "'"), false);
+  }
+
+  // Data members
+  const char* const name_;
+  const FlagFastTypeId type_id_;
+};
+
+}  // namespace
+
+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, nullptr);
+}
+
+// --------------------------------------------------------------------
+
+class FlagSaverImpl {
+ public:
+  FlagSaverImpl() = default;
+  FlagSaverImpl(const FlagSaverImpl&) = delete;
+  void operator=(const FlagSaverImpl&) = delete;
+
+  // Saves the flag states from the flag registry into this object.
+  // It's an error to call this more than once.
+  void SaveFromRegistry() {
+    assert(backup_registry_.empty());  // call only once!
+    flags_internal::ForEachFlag([&](CommandLineFlag& flag) {
+      if (auto flag_state =
+              flags_internal::PrivateHandleAccessor::SaveState(flag)) {
+        backup_registry_.emplace_back(std::move(flag_state));
+      }
+    });
+  }
+
+  // Restores the saved flag states into the flag registry.
+  void RestoreToRegistry() {
+    for (const auto& flag_state : backup_registry_) {
+      flag_state->Restore();
+    }
+  }
+
+ private:
+  std::vector<std::unique_ptr<flags_internal::FlagStateInterface>>
+      backup_registry_;
+};
+
+}  // namespace flags_internal
+
+FlagSaver::FlagSaver() : impl_(new flags_internal::FlagSaverImpl) {
+  impl_->SaveFromRegistry();
+}
+
+FlagSaver::~FlagSaver() {
+  if (!impl_) return;
+
+  impl_->RestoreToRegistry();
+  delete impl_;
+}
+
+// --------------------------------------------------------------------
+
+CommandLineFlag* FindCommandLineFlag(absl::string_view name) {
+  if (name.empty()) return nullptr;
+  flags_internal::FlagRegistry& registry =
+      flags_internal::FlagRegistry::GlobalRegistry();
+  return registry.FindFlag(name);
+}
+
+// --------------------------------------------------------------------
+
+absl::flat_hash_map<absl::string_view, absl::CommandLineFlag*> GetAllFlags() {
+  absl::flat_hash_map<absl::string_view, absl::CommandLineFlag*> res;
+  flags_internal::ForEachFlag([&](CommandLineFlag& flag) {
+    if (!flag.IsRetired()) res.insert({flag.Name(), &flag});
+  });
+  return res;
+}
+
+ABSL_NAMESPACE_END
+}  // namespace absl

Pods/abseil/absl/flags/reflection.h

@@ -0,0 +1,90 @@
+//
+// Copyright 2020 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// -----------------------------------------------------------------------------
+// File: reflection.h
+// -----------------------------------------------------------------------------
+//
+// This file defines the routines to access and operate on an Abseil Flag's
+// reflection handle.
+
+#ifndef ABSL_FLAGS_REFLECTION_H_
+#define ABSL_FLAGS_REFLECTION_H_
+
+#include <string>
+
+#include "absl/base/config.h"
+#include "absl/container/flat_hash_map.h"
+#include "absl/flags/commandlineflag.h"
+#include "absl/flags/internal/commandlineflag.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace flags_internal {
+class FlagSaverImpl;
+}  // namespace flags_internal
+
+// FindCommandLineFlag()
+//
+// Returns the reflection handle of an Abseil flag of the specified name, or
+// `nullptr` if not found. This function will emit a warning if the name of a
+// 'retired' flag is specified.
+absl::CommandLineFlag* FindCommandLineFlag(absl::string_view name);
+
+// Returns current state of the Flags registry in a form of mapping from flag
+// name to a flag reflection handle.
+absl::flat_hash_map<absl::string_view, absl::CommandLineFlag*> GetAllFlags();
+
+//------------------------------------------------------------------------------
+// FlagSaver
+//------------------------------------------------------------------------------
+//
+// A FlagSaver object stores the state of flags in the scope where the FlagSaver
+// is defined, allowing modification of those flags within that scope and
+// automatic restoration of the flags to their previous state upon leaving the
+// scope.
+//
+// A FlagSaver can be used within tests to temporarily change the test
+// environment and restore the test case to its previous state.
+//
+// Example:
+//
+//   void MyFunc() {
+//    absl::FlagSaver fs;
+//    ...
+//    absl::SetFlag(&FLAGS_myFlag, otherValue);
+//    ...
+//  } // scope of FlagSaver left, flags return to previous state
+//
+// This class is thread-safe.
+
+class FlagSaver {
+ public:
+  FlagSaver();
+  ~FlagSaver();
+
+  FlagSaver(const FlagSaver&) = delete;
+  void operator=(const FlagSaver&) = delete;
+
+ private:
+  flags_internal::FlagSaverImpl* impl_;
+};
+
+//-----------------------------------------------------------------------------
+
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_FLAGS_REFLECTION_H_

Pods/abseil/absl/flags/usage_config.cc

@@ -0,0 +1,165 @@
+//
+//  Copyright 2019 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/flags/usage_config.h"
+
+#include <functional>
+#include <iostream>
+#include <string>
+
+#include "absl/base/attributes.h"
+#include "absl/base/config.h"
+#include "absl/base/const_init.h"
+#include "absl/base/thread_annotations.h"
+#include "absl/flags/internal/path_util.h"
+#include "absl/flags/internal/program_name.h"
+#include "absl/strings/match.h"
+#include "absl/strings/string_view.h"
+#include "absl/strings/strip.h"
+#include "absl/synchronization/mutex.h"
+
+extern "C" {
+
+// Additional report of fatal usage error message before we std::exit. Error is
+// fatal if is_fatal argument to ReportUsageError is true.
+ABSL_ATTRIBUTE_WEAK void ABSL_INTERNAL_C_SYMBOL(
+    AbslInternalReportFatalUsageError)(absl::string_view) {}
+
+}  // extern "C"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace flags_internal {
+
+namespace {
+
+// --------------------------------------------------------------------
+// Returns true if flags defined in the filename should be reported with
+// -helpshort flag.
+
+bool ContainsHelpshortFlags(absl::string_view filename) {
+  // By default we only want flags in binary's main. We expect the main
+  // routine to reside in <program>.cc or <program>-main.cc or
+  // <program>_main.cc, where the <program> is the name of the binary
+  // (without .exe on Windows).
+  auto suffix = flags_internal::Basename(filename);
+  auto program_name = flags_internal::ShortProgramInvocationName();
+  absl::string_view program_name_ref = program_name;
+#if defined(_WIN32)
+  absl::ConsumeSuffix(&program_name_ref, ".exe");
+#endif
+  if (!absl::ConsumePrefix(&suffix, program_name_ref))
+    return false;
+  return absl::StartsWith(suffix, ".") || absl::StartsWith(suffix, "-main.") ||
+         absl::StartsWith(suffix, "_main.");
+}
+
+// --------------------------------------------------------------------
+// Returns true if flags defined in the filename should be reported with
+// -helppackage flag.
+
+bool ContainsHelppackageFlags(absl::string_view filename) {
+  // TODO(rogeeff): implement properly when registry is available.
+  return ContainsHelpshortFlags(filename);
+}
+
+// --------------------------------------------------------------------
+// Generates program version information into supplied output.
+
+std::string VersionString() {
+  std::string version_str(flags_internal::ShortProgramInvocationName());
+
+  version_str += "\n";
+
+#if !defined(NDEBUG)
+  version_str += "Debug build (NDEBUG not #defined)\n";
+#endif
+
+  return version_str;
+}
+
+// --------------------------------------------------------------------
+// Normalizes the filename specific to the build system/filesystem used.
+
+std::string NormalizeFilename(absl::string_view filename) {
+  // Skip any leading slashes
+  auto pos = filename.find_first_not_of("\\/");
+  if (pos == absl::string_view::npos) return "";
+
+  filename.remove_prefix(pos);
+  return std::string(filename);
+}
+
+// --------------------------------------------------------------------
+
+ABSL_CONST_INIT absl::Mutex custom_usage_config_guard(absl::kConstInit);
+ABSL_CONST_INIT FlagsUsageConfig* custom_usage_config
+    ABSL_GUARDED_BY(custom_usage_config_guard) = nullptr;
+
+}  // namespace
+
+FlagsUsageConfig GetUsageConfig() {
+  absl::MutexLock l(&custom_usage_config_guard);
+
+  if (custom_usage_config) return *custom_usage_config;
+
+  FlagsUsageConfig default_config;
+  default_config.contains_helpshort_flags = &ContainsHelpshortFlags;
+  default_config.contains_help_flags = &ContainsHelppackageFlags;
+  default_config.contains_helppackage_flags = &ContainsHelppackageFlags;
+  default_config.version_string = &VersionString;
+  default_config.normalize_filename = &NormalizeFilename;
+
+  return default_config;
+}
+
+void ReportUsageError(absl::string_view msg, bool is_fatal) {
+  std::cerr << "ERROR: " << msg << std::endl;
+
+  if (is_fatal) {
+    ABSL_INTERNAL_C_SYMBOL(AbslInternalReportFatalUsageError)(msg);
+  }
+}
+
+}  // namespace flags_internal
+
+void SetFlagsUsageConfig(FlagsUsageConfig usage_config) {
+  absl::MutexLock l(&flags_internal::custom_usage_config_guard);
+
+  if (!usage_config.contains_helpshort_flags)
+    usage_config.contains_helpshort_flags =
+        flags_internal::ContainsHelpshortFlags;
+
+  if (!usage_config.contains_help_flags)
+    usage_config.contains_help_flags = flags_internal::ContainsHelppackageFlags;
+
+  if (!usage_config.contains_helppackage_flags)
+    usage_config.contains_helppackage_flags =
+        flags_internal::ContainsHelppackageFlags;
+
+  if (!usage_config.version_string)
+    usage_config.version_string = flags_internal::VersionString;
+
+  if (!usage_config.normalize_filename)
+    usage_config.normalize_filename = flags_internal::NormalizeFilename;
+
+  if (flags_internal::custom_usage_config)
+    *flags_internal::custom_usage_config = usage_config;
+  else
+    flags_internal::custom_usage_config = new FlagsUsageConfig(usage_config);
+}
+
+ABSL_NAMESPACE_END
+}  // namespace absl

Pods/abseil/absl/flags/usage_config.h

@@ -0,0 +1,135 @@
+//
+//  Copyright 2019 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// -----------------------------------------------------------------------------
+// File: usage_config.h
+// -----------------------------------------------------------------------------
+//
+// This file defines the main usage reporting configuration interfaces and
+// documents Abseil's supported built-in usage flags. If these flags are found
+// when parsing a command-line, Abseil will exit the program and display
+// appropriate help messages.
+#ifndef ABSL_FLAGS_USAGE_CONFIG_H_
+#define ABSL_FLAGS_USAGE_CONFIG_H_
+
+#include <functional>
+#include <string>
+
+#include "absl/base/config.h"
+#include "absl/strings/string_view.h"
+
+// -----------------------------------------------------------------------------
+// Built-in Usage Flags
+// -----------------------------------------------------------------------------
+//
+// Abseil supports the following built-in usage flags. When passed, these flags
+// exit the program and :
+//
+// * --help
+//     Shows help on important flags for this binary
+// * --helpfull
+//     Shows help on all flags
+// * --helpshort
+//     Shows help on only the main module for this program
+// * --helppackage
+//     Shows help on all modules in the main package
+// * --version
+//     Shows the version and build info for this binary and exits
+// * --only_check_args
+//     Exits after checking all flags
+// * --helpon
+//     Shows help on the modules named by this flag value
+// * --helpmatch
+//     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)>;
+}  // namespace flags_internal
+
+// FlagsUsageConfig
+//
+// This structure contains the collection of callbacks for changing the behavior
+// of the usage reporting routines in Abseil Flags.
+struct FlagsUsageConfig {
+  // Returns true if flags defined in the given source code file should be
+  // reported with --helpshort flag. For example, if the file
+  // "path/to/my/code.cc" defines the flag "--my_flag", and
+  // contains_helpshort_flags("path/to/my/code.cc") returns true, invoking the
+  // program with --helpshort will include information about --my_flag in the
+  // program output.
+  flags_internal::FlagKindFilter contains_helpshort_flags;
+
+  // Returns true if flags defined in the filename should be reported with
+  // --help flag. For example, if the file
+  // "path/to/my/code.cc" defines the flag "--my_flag", and
+  // contains_help_flags("path/to/my/code.cc") returns true, invoking the
+  // program with --help will include information about --my_flag in the
+  // program output.
+  flags_internal::FlagKindFilter contains_help_flags;
+
+  // Returns true if flags defined in the filename should be reported with
+  // --helppackage flag. For example, if the file
+  // "path/to/my/code.cc" defines the flag "--my_flag", and
+  // contains_helppackage_flags("path/to/my/code.cc") returns true, invoking the
+  // program with --helppackage will include information about --my_flag in the
+  // program output.
+  flags_internal::FlagKindFilter contains_helppackage_flags;
+
+  // Generates string containing program version. This is the string reported
+  // when user specifies --version in a command line.
+  std::function<std::string()> version_string;
+
+  // Normalizes the filename specific to the build system/filesystem used. This
+  // routine is used when we report the information about the flag definition
+  // location. For instance, if your build resides at some location you do not
+  // want to expose in the usage output, you can trim it to show only relevant
+  // part.
+  // For example:
+  //   normalize_filename("/my_company/some_long_path/src/project/file.cc")
+  // might produce
+  //   "project/file.cc".
+  std::function<std::string(absl::string_view)> normalize_filename;
+};
+
+// SetFlagsUsageConfig()
+//
+// Sets the usage reporting configuration callbacks. If any of the callbacks are
+// not set in usage_config instance, then the default value of the callback is
+// used.
+void SetFlagsUsageConfig(FlagsUsageConfig usage_config);
+
+namespace flags_internal {
+
+FlagsUsageConfig GetUsageConfig();
+
+void ReportUsageError(absl::string_view msg, bool is_fatal);
+
+}  // namespace flags_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+extern "C" {
+
+// Additional report of fatal usage error message before we std::exit. Error is
+// fatal if is_fatal argument to ReportUsageError is true.
+void ABSL_INTERNAL_C_SYMBOL(AbslInternalReportFatalUsageError)(
+    absl::string_view);
+
+}  // extern "C"
+
+#endif  // ABSL_FLAGS_USAGE_CONFIG_H_