builtin-types-compatible-p.c

this is a gcc file, you can download it and learn its usetility, for further detail please look at t

int i;
double d;

/* Make sure we return a constant.  */
float rootbeer[__builtin_types_compatible_p (int, typeof(i))];

typedef enum { hot, dog, poo, bear } dingos;
typedef enum { janette, laura, amanda } cranberry;

typedef float same1;
typedef float same2;

int main (void);

int main (void)
{
  /* Compatible types.  */
  if (!(__builtin_types_compatible_p (int, const int)
	&& __builtin_types_compatible_p (typeof (hot), int)
	&& __builtin_types_compatible_p (typeof (hot), typeof (laura))
	&& __builtin_types_compatible_p (int[5], int[])
	&& __builtin_types_compatible_p (typeof (dingos), typeof (cranberry))
	&& __builtin_types_compatible_p (same1, same2)))
    abort ();

  /* Incompatible types.  */
  if (__builtin_types_compatible_p (char *, int)
      || __builtin_types_compatible_p (char *, const char *)
      || __builtin_types_compatible_p (long double, double)
      || __builtin_types_compatible_p (typeof (i), typeof (d))
      || __builtin_types_compatible_p (char, int)
      || __builtin_types_compatible_p (char *, char **))
    abort ();
  exit (0);
}