1//
2// Copyright 2019 The Abseil Authors.
3//
4// Licensed under the Apache License, Version 2.0 (the "License");
5// you may not use this file except in compliance with the License.
6// You may obtain a copy of the License at
7//
8// https://www.apache.org/licenses/LICENSE-2.0
9//
10// Unless required by applicable law or agreed to in writing, software
11// distributed under the License is distributed on an "AS IS" BASIS,
12// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13// See the License for the specific language governing permissions and
14// limitations under the License.
15//
16// -----------------------------------------------------------------------------
17// File: declare.h
18// -----------------------------------------------------------------------------
19//
20// This file defines the ABSL_DECLARE_FLAG macro, allowing you to declare an
21// `absl::Flag` for use within a translation unit. You should place this
22// declaration within the header file associated with the .cc file that defines
23// and owns the `Flag`.
24
25#ifndef ABSL_FLAGS_DECLARE_H_
26#define ABSL_FLAGS_DECLARE_H_
27
28#include "absl/strings/string_view.h"
29
30namespace absl {
31namespace flags_internal {
32
33// absl::Flag<T> represents a flag of type 'T' created by ABSL_FLAG.
34template <typename T>
35class Flag;
36
37} // namespace flags_internal
38
39// Flag
40//
41// Forward declaration of the `absl::Flag` type for use in defining the macro.
42template <typename T>
43using Flag = flags_internal::Flag<T>;
44
45} // namespace absl
46
47// ABSL_DECLARE_FLAG()
48//
49// This macro is a convenience for declaring use of an `absl::Flag` within a
50// translation unit. This macro should be used within a header file to
51// declare usage of the flag within any .cc file including that header file.
52//
53// The ABSL_DECLARE_FLAG(type, name) macro expands to:
54//
55// extern absl::Flag<type> FLAGS_name;
56#define ABSL_DECLARE_FLAG(type, name) extern ::absl::Flag<type> FLAGS_##name
57
58#endif // ABSL_FLAGS_DECLARE_H_
59