compiler_hints.h

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/*
 * Copyright (C) 2014 Freie Universität Berlin
 *               2017 HAW-Hamburg
 *
 * This file is subject to the terms and conditions of the GNU Lesser
 * General Public License v2.1. See the file LICENSE in the top level
 * directory for more details.
 */
 
#ifndef COMPILER_HINTS_H
#define COMPILER_HINTS_H
 
#include <assert.h>
#include <stdint.h>
 
#ifdef __cplusplus
extern "C" {
#endif
 
#ifndef NORETURN
#ifdef __GNUC__
#define NORETURN  __attribute__((noreturn))
#else
#define NORETURN
#endif
#endif
 
#ifndef PURE
#ifdef __GNUC__
#define PURE  __attribute__((pure))
#else
#define PURE
#endif
#endif
 
#ifndef MAYBE_UNUSED
#ifdef __GNUC__
#define MAYBE_UNUSED  __attribute__((unused))
#else
#define MAYBE_UNUSED
#endif
#endif
 
#if defined(__llvm__) || defined(__clang__)
#define NO_SANITIZE_ARRAY __attribute__((no_sanitize("address")))
#else
#define NO_SANITIZE_ARRAY
#endif
 
#if ((__GNUC__ == 4) && (__GNUC_MINOR__ >= 5)) || (__GNUC__ >= 5) || defined(__clang__)
#define UNREACHABLE() __builtin_unreachable()
#else
#define UNREACHABLE() do { /* nothing */ } while (1)
#endif
 
#define WITHOUT_PEDANTIC(...) \
    _Pragma("GCC diagnostic push") \
    _Pragma("GCC diagnostic ignored \"-Wpedantic\"") \
    __VA_ARGS__ \
    _Pragma("GCC diagnostic pop")
#define WITHOUT_PEDANTIC(...) \ …
 
#define DECLARE_CONSTANT(identifier, const_expr) \
    WITHOUT_PEDANTIC(enum { identifier = const_expr };)
#define DECLARE_CONSTANT(identifier, const_expr) \ …
 
#if DOXYGEN
#define IS_CT_CONSTANT(expr) <IMPLEMENTATION>
#elif defined(__GNUC__)
/* both clang and gcc (which both define __GNUC__) support this */
#define IS_CT_CONSTANT(expr) __builtin_constant_p(expr)
#else
#define IS_CT_CONSTANT(expr) 0
#endif
 
#define likely(x)       __builtin_expect((uintptr_t)(x), 1)
 
#define unlikely(x)     __builtin_expect((uintptr_t)(x), 0)
 
#ifdef NDEBUG
#define assume(cond)    ((cond) ? (void)0 : UNREACHABLE())
#else
#define assume(cond)    assert(cond)
#endif
 
static inline unsigned may_be_zero(unsigned n)
{
    return n;
}
static inline unsigned may_be_zero(unsigned n) {…}
 
#ifdef __cplusplus
}
#endif
 
#endif /* COMPILER_HINTS_H */