CppAttributes.h

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/*
 * Copyright 2015-present Facebook, Inc.
 *
 * 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
 *
 *   http://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.
 */

#pragma once

#ifndef __has_attribute
#define FOLLY_HAS_ATTRIBUTE(x) 0
#else
#define FOLLY_HAS_ATTRIBUTE(x) __has_attribute(x)
#endif

#ifndef __has_cpp_attribute
#define FOLLY_HAS_CPP_ATTRIBUTE(x) 0
#else
#define FOLLY_HAS_CPP_ATTRIBUTE(x) __has_cpp_attribute(x)
#endif

#ifndef __has_extension
#define FOLLY_HAS_EXTENSION(x) 0
#else
#define FOLLY_HAS_EXTENSION(x) __has_extension(x)
#endif

#if FOLLY_HAS_CPP_ATTRIBUTE(fallthrough)
#define FOLLY_FALLTHROUGH [[fallthrough]]
#elif FOLLY_HAS_CPP_ATTRIBUTE(clang::fallthrough)
#define FOLLY_FALLTHROUGH [[clang::fallthrough]]
#elif FOLLY_HAS_CPP_ATTRIBUTE(gnu::fallthrough)
#define FOLLY_FALLTHROUGH [[gnu::fallthrough]]
#else
#define FOLLY_FALLTHROUGH
#endif

#if FOLLY_HAS_CPP_ATTRIBUTE(maybe_unused)
#define FOLLY_MAYBE_UNUSED [[maybe_unused]]
#elif FOLLY_HAS_ATTRIBUTE(__unused__) || __GNUC__
#define FOLLY_MAYBE_UNUSED __attribute__((__unused__))
#else
#define FOLLY_MAYBE_UNUSED
#endif

#if FOLLY_HAS_EXTENSION(nullability)
#define FOLLY_NULLABLE _Nullable
#define FOLLY_NONNULL _Nonnull
#else
#define FOLLY_NULLABLE
#define FOLLY_NONNULL
#endif

#if __GNUC__
#define FOLLY_COLD __attribute__((__cold__))
#else
#define FOLLY_COLD
#endif