Compiler.h

/*
 * Copyright 2003-2021 The Music Player Daemon Project
 * http://www.musicpd.org
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

#ifndef COMPILER_H
#define COMPILER_H

#define GCC_MAKE_VERSION(major, minor, patchlevel) ((major) * 10000 + (minor) * 100 + patchlevel)

#ifdef __GNUC__
#define GCC_VERSION GCC_MAKE_VERSION(__GNUC__, __GNUC_MINOR__, __GNUC_PATCHLEVEL__)
#else
#define GCC_VERSION 0
#endif

#ifdef __clang__
#  define CLANG_VERSION GCC_MAKE_VERSION(__clang_major__, __clang_minor__, __clang_patchlevel__)
#elif defined(__GNUC__)
#  define CLANG_VERSION 0
#endif

/**
 * Are we building with the specified version of gcc (not clang or any
 * other compiler) or newer?
 */
#define GCC_CHECK_VERSION(major, minor) \
	(CLANG_VERSION == 0 && \
	 GCC_VERSION >= GCC_MAKE_VERSION(major, minor, 0))

/**
 * Are we building with clang (any version) or at least the specified
 * gcc version?
 */
#define CLANG_OR_GCC_VERSION(major, minor) \
	(CLANG_VERSION > 0 || GCC_CHECK_VERSION(major, minor))

/**
 * Are we building with gcc (not clang or any other compiler) and a
 * version older than the specified one?
 */
#define GCC_OLDER_THAN(major, minor) \
	(GCC_VERSION > 0 && CLANG_VERSION == 0 && \
	 GCC_VERSION < GCC_MAKE_VERSION(major, minor, 0))

/**
 * Are we building with the specified version of clang or newer?
 */
#define CLANG_CHECK_VERSION(major, minor) \
	(CLANG_VERSION >= GCC_MAKE_VERSION(major, minor, 0))

#if CLANG_OR_GCC_VERSION(4,0)

/* GCC 4.x */

#define gcc_const __attribute__((const))
#define gcc_may_alias __attribute__((may_alias))
#define gcc_malloc __attribute__((malloc))
#define gcc_packed __attribute__((packed))
#define gcc_printf(a,b) __attribute__((format(printf, a, b)))
#define gcc_pure __attribute__((pure))
#define gcc_sentinel __attribute__((sentinel))

#define gcc_nonnull(...) __attribute__((nonnull(__VA_ARGS__)))
#define gcc_nonnull_all __attribute__((nonnull))
#define gcc_returns_nonnull __attribute__((returns_nonnull))
#define gcc_returns_twice __attribute__((returns_twice))

#define gcc_likely(x) __builtin_expect (!!(x), 1)
#define gcc_unlikely(x) __builtin_expect (!!(x), 0)

#define gcc_visibility_hidden __attribute__((visibility("hidden")))
#define gcc_visibility_default __attribute__((visibility("default")))

#define gcc_noinline __attribute__((noinline))
#define gcc_always_inline __attribute__((always_inline))

#else

/* generic C compiler */

#define gcc_const
#define gcc_may_alias
#define gcc_malloc
#define gcc_packed
#define gcc_printf(a,b)
#define gcc_pure
#define gcc_sentinel

#define gcc_nonnull(...)
#define gcc_nonnull_all
#define gcc_returns_nonnull
#define gcc_returns_twice

#define gcc_likely(x) (x)
#define gcc_unlikely(x) (x)

#define gcc_visibility_hidden
#define gcc_visibility_default

#define gcc_noinline
#define gcc_always_inline inline

#endif

#if CLANG_OR_GCC_VERSION(4,3)

#define gcc_hot __attribute__((hot))
#define gcc_cold __attribute__((cold))

#else /* ! GCC_UNUSED >= 40300 */

#define gcc_hot
#define gcc_cold

#endif /* ! GCC_UNUSED >= 40300 */

#if GCC_CHECK_VERSION(4,6)
#define gcc_flatten __attribute__((flatten))
#else
#define gcc_flatten
#endif

#if GCC_CHECK_VERSION(7,0)
#define gcc_fallthrough __attribute__((fallthrough))
#elif CLANG_CHECK_VERSION(10,0) && defined(__cplusplus)
#define gcc_fallthrough [[fallthrough]]
#else
#define gcc_fallthrough
#endif

#ifndef __cplusplus
/* plain C99 has "restrict" */
#define gcc_restrict restrict
#elif CLANG_OR_GCC_VERSION(4,0)
/* "__restrict__" is a GCC extension for C++ */
#define gcc_restrict __restrict__
#else
/* disable it on other compilers */
#define gcc_restrict
#endif

#ifndef __has_feature
  // define dummy macro for non-clang compilers
  #define __has_feature(x) 0
#endif

#if defined(__GNUC__) || defined(__clang__)
#define gcc_unreachable() __builtin_unreachable()
#else
#define gcc_unreachable()
#endif

#endif