build/aclocal/atomic_builtins.m4

   1
   2 dnl Checks for availability of GCC's atomic operations builtins.
   3 dnl Defines HAVE_GCC_ATOMIC_BUILTINS if available.
   4
   5 AC_DEFUN([WX_ATOMIC_BUILTINS],
   6 [
   7   AC_REQUIRE([AC_PROG_CC])
   8   if test -n "$GCC"; then
   9     AC_MSG_CHECKING([for __sync_fetch_and_add and __sync_sub_and_fetch builtins])
  10     AC_CACHE_VAL(wx_cv_cc_gcc_atomic_builtins, [
  11       AC_TRY_LINK(
  12         [],
  13         [
  14           unsigned int value=0;
  15           /* wxAtomicInc doesn't use return value here */
  16           __sync_fetch_and_add(&value, 2);
  17           __sync_sub_and_fetch(&value, 1);
  18           /* but wxAtomicDec does, so mimic that: */
  19           unsigned int r2 = __sync_sub_and_fetch(&value, 1);
  20         ],
  21         wx_cv_cc_gcc_atomic_builtins=yes,
  22         wx_cv_cc_gcc_atomic_builtins=no)
  23       ])
  24     AC_MSG_RESULT([$wx_cv_cc_gcc_atomic_builtins])
  25     if test $wx_cv_cc_gcc_atomic_builtins = yes; then
  26       AC_DEFINE([HAVE_GCC_ATOMIC_BUILTINS])
  27     fi
  28   fi
  29 ])