1  #define _GNU_SOURCE
       2  #include <math.h>
       3  #include <float.h>
       4  
       5  int isnansf (float x)       { return issignaling (x) ? 1 : 0; }
       6  int isnans  (double x)      { return issignaling (x) ? 1 : 0; }
       7  int isnansl (long double x) { return issignaling (x) ? 1 : 0; }
       8