compiler_gcc.h

/*
 * Copyright 2012 10gen 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

#define MONGO_COMPILER_NORETURN __attribute__((__noreturn__))

#define MONGO_COMPILER_VARIABLE_UNUSED __attribute__((__unused__))

#define MONGO_COMPILER_ALIGN_TYPE(ALIGNMENT) __attribute__((__aligned__(ALIGNMENT)))

#define MONGO_COMPILER_ALIGN_VARIABLE(ALIGNMENT) __attribute__((__aligned__(ALIGNMENT)))

// NOTE(schwerin): These visibility and calling-convention macro definitions assume we're not using
// GCC/CLANG to target native Windows. If/when we decide to do such targeting, we'll need to change
// compiler flags on Windows to make sure we use an appropriate calling convention, and configure
// MONGO_COMPILER_API_EXPORT, MONGO_COMPILER_API_IMPORT and MONGO_COMPILER_API_CALLING_CONVENTION
// correctly.  I believe "correctly" is the following:
//
// #ifdef _WIN32
// #define MONGO_COMIPLER_API_EXPORT __attribute__(( __dllexport__ ))
// #define MONGO_COMPILER_API_IMPORT __attribute__(( __dllimport__ ))
// #ifdef _M_IX86
// #define MONGO_COMPILER_API_CALLING_CONVENTION __attribute__((__cdecl__))
// #else
// #define MONGO_COMPILER_API_CALLING_CONVENTION
// #endif
// #else ... fall through to the definitions below.

#define MONGO_COMPILER_API_EXPORT __attribute__((__visibility__("default")))
#define MONGO_COMPILER_API_IMPORT
#define MONGO_COMPILER_API_CALLING_CONVENTION

// old versions of gcc and clang don't accept a message
#ifdef __clang__

// for compatibility with older versions of clang
#ifndef __has_extension
#define __has_extension __has_feature
#endif

// Technically __attribute__(deprecated) is supposed to come at the end of the declaration, but
// GCC and clang accept it at the start, which eases compatibility with MSVC

#if __has_extension(attribute_deprecated_with_message)
#define MONGO_COMPILER_API_DEPRECATED(MSG) __attribute__((deprecated(MSG)))
#else  // older clang doesn't support message
#define MONGO_COMPILER_API_DEPRECATED(MSG) __attribute__((deprecated))
#endif

#else  // we are using GCC

#if __GNUC__ > 4 || ((__GNUC__ == 4) && __GNUC_MINOR > 5)  // deprecation messages were added in 4.5
#define MONGO_COMPILER_API_DEPRECATED(MSG) __attribute__((deprecated(MSG)))
#else  // Older GCC doesn't support message
#define MONGO_COMPILER_API_DEPRECATED(MSG) __attribute__((deprecated))
#endif

#endif

#define MONGO_likely(x) static_cast<bool>(__builtin_expect(static_cast<bool>(x), 1))
#define MONGO_unlikely(x) static_cast<bool>(__builtin_expect(static_cast<bool>(x), 0))