chromium/third_party/abseil-cpp/absl/flags/commandlineflag.h

//
// 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();
//   ...

// These are only used as constexpr global objects.
// They do not use a virtual destructor to simplify their implementation.
// They are not destroyed except at program exit, so leaks do not matter.
#if defined(__GNUC__) && !defined(__clang__)
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wnon-virtual-dtor"
#endif
class CommandLineFlag { … };
#if defined(__GNUC__) && !defined(__clang__)
#pragma GCC diagnostic pop
#endif

ABSL_NAMESPACE_END
}  // namespace absl

#endif  // ABSL_FLAGS_COMMANDLINEFLAG_H_