m4_define([libcairo_openmp_program],[dnl
  #include <stdio.h>

  extern unsigned int lcg_seed;
  #pragma omp threadprivate(lcg_seed)
  unsigned int lcg_seed;

  unsigned function(unsigned a, unsigned b)
  {
	lcg_seed ^= b;
	return ((a + b) ^ a ) + lcg_seed;
  }

  int main(int argc, char **argv)
  {
	int i;
	int n1 = 0, n2 = argc;
	unsigned checksum = 0;
	int verbose = argv != NULL;
	unsigned (*test_function)(unsigned, unsigned);
	test_function = function;
	#pragma omp parallel for reduction(+:checksum) default(none) \
					shared(n1, n2, test_function, verbose)
	for (i = n1; i < n2; i++)
	{
		unsigned crc = test_function (i, 0);
		if (verbose)
			printf ("%d: %08X\n", i, crc);
		checksum += crc;
	}
	printf("%u\n", checksum);
	return 0;
  }
}])

AC_DEFUN([CAIRO_CHECK_OPENMP],[dnl
	 CAIRO_CC_TRY_LINK_WITH_ENV_SILENT(
		    [CFLAGS="$CFLAGS $2";
		     LIBS="$LIBS $3"],
		    [$4],
		    [$1_CFLAGS="$2";
		     $1_LIBS="$3";
		     $5],
		    [$1_CFLAGS="";
		     $1_LIBS="";
		     $6])
])

AC_DEFUN([CAIRO_CONFIGURE_OPENMP],[dnl
	if test "x$OPENMP_CFLAGS" = "x"; then
		OPENMP_CFLAGS="-fopenmp"
	fi
	if test "x$OPENMP_LIBS" = "x"; then
		OPENMP_LIBS="-lgomp"
	fi

	CAIRO_CHECK_OPENMP(
		[openmp], [$OPENMP_CFLAGS], [$OPENMP_LIBS],
		[libcairo_openmp_program],
		[have_openmp=yes],
		[have_openmp=no])
	OPENMP_CFLAGS=
	OPENMP_LIBS=

	dnl Tell autoconf about the results.
	if test "x$have_openmp" = "xyes"; then
		 AC_DEFINE([CAIRO_HAS_OPENMP], 1,
			[Define to 1 if we have openmp support])
	fi

	dnl Set the output variables for CAIRO_ENABLE.
	use_openmp="$have_openmp"
	openmp_REQUIRES=""
])