[apple/libdispatch.git] / m4 / atomic.m4

AC_DEFUN([DISPATCH_C_ATOMIC_BUILTINS], [
#
# This is a bit subtle: on i386 systems without at least -march=i486 defined,
# certain built-in atomics fall back to depending on undefined symbols if
# their return values are used.
#
AC_CACHE_CHECK([for gcc atomic builtins],[dispatch_cv_atomic],
[AC_LINK_IFELSE([AC_LANG_PROGRAM([],[[
int i, x =0;
i = __sync_add_and_fetch(&x,1);
return x;]])],[dispatch_cv_atomic=yes],
  [saveCFLAGS="$CFLAGS"
  CFLAGS="$CFLAGS -march=i486"
  AC_LINK_IFELSE([AC_LANG_PROGRAM([],[[
  int i, x =0;
  i = __sync_add_and_fetch(&x,1);
  return x;]])],[CFLAGS="$saveCFLAGS"
dispatch_cv_atomic="-march=i486"
])])])

])
Commit	Line	Data
e85f4437 A	1	AC_DEFUN([DISPATCH_C_ATOMIC_BUILTINS], [
	2	#
	3	# This is a bit subtle: on i386 systems without at least -march=i486 defined,
	4	# certain built-in atomics fall back to depending on undefined symbols if
	5	# their return values are used.
	6	#
	7	AC_CACHE_CHECK([for gcc atomic builtins],[dispatch_cv_atomic],
	8	[AC_LINK_IFELSE([AC_LANG_PROGRAM([],[[
	9	int i, x =0;
	10	i = __sync_add_and_fetch(&x,1);
	11	return x;]])],[dispatch_cv_atomic=yes],
	12	[saveCFLAGS="$CFLAGS"
	13	CFLAGS="$CFLAGS -march=i486"
	14	AC_LINK_IFELSE([AC_LANG_PROGRAM([],[[
	15	int i, x =0;
	16	i = __sync_add_and_fetch(&x,1);
	17	return x;]])],[CFLAGS="$saveCFLAGS"
	18	dispatch_cv_atomic="-march=i486"
	19	])])])
	20
	21	])