check_c_source_compiles("#include<math.h>\nint main(int n,char*v[]){return sqrt(n);}" HAVE_MATH)

check_c_source_compiles("
#include <math.h>

int
main(int argc, char *argv[])
{
	double d = 1.0;
	d = fabs(d);
	return (0);
}
" HAVE_MATH)

check_c_source_compiles("${LIBM_TEST_SOURCE}" HAVE_MATH)