gcc/testsuite/gcc.dg/pr18520-1.c

/* PR middle-end/18520 */
/* { dg-do compile } */
/* { dg-options "-O2 -ffast-math" } */

extern int isnan (double __value) __attribute__ ((__const__));

int gsl_isnan (const double x)
{
  return isnan(x);
}