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/*
* compiler.h - compiler specific macros
*
* This file is Copyright 2010 by the GPSD project
* SPDX-License-Identifier: BSD-2-clause
*
* Calling file needs to have previously included "gpsd_config.h"
*/
#ifndef _GPSD_COMPILER_H_
#define _GPSD_COMPILER_H_
#ifndef GPSD_CONFIG_H
#error "Missing GPSD_CONFIG_H"
#endif
/*
* Tell GCC that we want thread-safe behavior with _REENTRANT;
* in particular, errno must be thread-local.
* Tell POSIX-conforming implementations with _POSIX_THREAD_SAFE_FUNCTIONS.
* See http://www.unix.org/whitepapers/reentrant.html
*/
#ifndef _REENTRANT
#define _REENTRANT
#endif
#ifndef _POSIX_THREAD_SAFE_FUNCTIONS
#define _POSIX_THREAD_SAFE_FUNCTIONS
#endif
// Macro for declaring function with printf-like arguments.
# if __GNUC__ >= 3 || (__GNUC__ == 2 && __GNUC_MINOR__ >= 7)
#define PRINTF_FUNC(format_index, arg_index) \
__attribute__((__format__(__printf__, format_index, arg_index)))
#else
#define PRINTF_FUNC(format_index, arg_indx)
#endif
// Macro for declaring function arguments unused.
#if defined(__GNUC__) || defined(__clang__)
#define UNUSED __attribute__((unused))
#else
#define UNUSED
#endif
// Macro to suppress FALLTHROUGH warnings
#if defined(__GNUC__) && __GNUC__ >= 7
#define FALLTHROUGH __attribute__((fallthrough));
// At least one Clang 6 version advertises fallthrough and then chokes on it
#elif defined(__clang__) && __clang_major__ > 6
#ifndef __has_attribute // For backwards compatibility
#define __has_attribute(x) 0
#endif
#if __has_attribute(fallthrough)
#define FALLTHROUGH __attribute__((fallthrough));
#endif
#endif
#ifndef FALLTHROUGH
#define FALLTHROUGH
#endif
/*
* Macro for compile-time checking if argument is an array.
* It expands to constant expression with int value 0.
*/
#if defined(__GNUC__)
#define COMPILE_CHECK_IS_ARRAY(arr) ( \
0 * (int) sizeof(({ \
struct { \
int unused_int; \
__typeof__(arr) unused_arr; \
} zero_init = {0}; \
__typeof__(arr) arg_is_not_array UNUSED = { \
zero_init.unused_arr[0], \
}; \
1; \
})) \
)
#else
#define COMPILE_CHECK_IS_ARRAY(arr) 0
#endif
// Needed because 4.x versions of GCC are really annoying
// FIXME: in 20202, do we care about gcc 4?
#define ignore_return(funcall) \
do { \
UNUSED ssize_t locresult = (funcall); \
assert(locresult != -23); \
} while (0)
#ifdef __COVERITY__
// do nothing
#elif defined(__cplusplus)
// we are C++
#if __cplusplus >= 201103L
/* C++ before C++11 can not handle stdatomic.h or atomic
* atomic is just C++ for stdatomic.h */
#include <atomic>
#endif
#elif defined(HAVE_STDATOMIC_H)
// we are C and atomics are in C98 and newer
#include <stdatomic.h>
#elif defined(HAVE_OSATOMIC_H)
// do it the OS X way
#include <libkern/OSAtomic.h>
#endif // HAVE_OSATOMIC_H
// prevent instruction reordering across any call to this function
static inline void memory_barrier(void)
{
#ifdef __COVERITY__
// do nothing
#elif defined(__cplusplus)
// we are C++
#if __cplusplus >= 201103L
// C++11 and later has atomics, earlier do not
std::atomic_thread_fence(std::memory_order_seq_cst);
#endif
#elif defined HAVE_STDATOMIC_H
// we are C and atomics are in C98 and newer
atomic_thread_fence(memory_order_seq_cst);
#elif defined(HAVE_OSATOMIC_H)
// do it the OS X way
OSMemoryBarrier();
#elif defined(__GNUC__)
__asm__ __volatile__ ("" : : : "memory");
#endif
}
/* likely(), unlikely(), branch optimization
* https://kernelnewbies.org/FAQ/LikelyUnlikely
*/
#if defined(__GNUC__)
#define likely(x) __builtin_expect(!!(x), 1)
#define unlikely(x) __builtin_expect(!!(x), 0)
#else
#define likely(x) (x)
#define unlikely(x) (x)
#endif
#endif // _GPSD_COMPILER_H_
// vim: set expandtab shiftwidth=4
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