compiler.h

/*
 * compiler.h - compiler specific macros
 *
 * This software is distributed under a BSD-style license. See the
 * file "COPYING" in the toop-level directory of the distribution for details.
 */
#ifndef _GPSD_COMPILER_H_
#define _GPSD_COMPILER_H_

/*
 * 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

#include "gpsd_config.h"	/* is HAVE_STDATOMIC defined? */

/* 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 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 */
#define ignore_return(funcall) \
    do { \
        UNUSED ssize_t locresult = (funcall); \
        assert(locresult != -23); \
    } while (0)

#ifdef HAVE_STDATOMIC_H
#if !defined(__COVERITY__)
#if !defined(__cplusplus)
    #include <stdatomic.h>
#elif __cplusplus >= 201103L
    /* C++ before C++11 can not handle stdatomic.h or atomic */
    /* atomic is just C++ for stdatomic.h */
    #include <atomic>
#endif /* __cplusplus */
#endif /* __COVERITY__ */
#endif /* HAVE_STDATOMIC_H */

#ifdef HAVE_OSATOMIC_H
#include <libkern/OSAtomic.h>
#endif /* HAVE_OSATOMIC_H */

static inline void memory_barrier(void)
/* prevent instruction reordering across any call to this function */
{
#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
}

#endif /* _GPSD_COMPILER_H_ */