language_feature_macros.h

// Copyright 2020 The Pigweed 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.
 
// Macros for using C++ features in older standards.
#pragma once
 
#if __cplusplus >= 202002L
#define PW_CONSTEXPR_CPP20 constexpr
#else
#define PW_CONSTEXPR_CPP20
#endif  // __cpp_constexpr >= 201304L
 
#if defined(__cpp_consteval) && __cpp_consteval >= 201811L
#define PW_CONSTEVAL consteval
#else
#define PW_CONSTEVAL constexpr
#endif  // __cpp_consteval >= 201811L
 
#if defined(__cpp_constinit) && __cpp_constinit >= 201907L
#define PW_CONSTINIT constinit
#elif defined(__clang__)
#define PW_CONSTINIT [[clang::require_constant_initialization]]
#elif defined(__GNUC__) && __GNUC__ >= 10
#define PW_CONSTINIT __constinit
#else
#define PW_CONSTINIT                                                \
  static_assert(false,                                              \
                "PW_CONSTINIT does not yet support this compiler; " \
                "implement PW_CONSTINIT for this compiler to use it.");
#endif  // __cpp_constinit
 
#if __cplusplus >= 202002L
#define PW_NODISCARD_STR(str) [[nodiscard(str)]]
#else
#define PW_NODISCARD_STR(str) [[nodiscard]]
#endif  // __cplusplus >= 202002L