gcc/testsuite/gcc.c-torture/execute/991228-1.c

   1 void abort (void);
   2 void exit (int);
   3
   4 __extension__ union { double d; int i[2]; } u = { d: -0.25 };
   5
   6 /* This assumes the endianness of words in a long long is the same as
   7    that for doubles, which doesn't hold for a few platforms, but we
   8    can probably special case them here, as appropriate.  */
   9 long long endianness_test = 1;
  10 #define MSW (*(int*)&endianness_test)
  11
  12 int
  13 signbit(double x)
  14 {
  15   __extension__ union { double d; int i[2]; } u = { d: x };
  16   return u.i[MSW] < 0;
  17 }
  18
  19 int main(void)
  20 {
  21   if (2*sizeof(int) != sizeof(double) || u.i[MSW] >= 0)
  22     exit(0);
  23
  24   if (!signbit(-0.25))
  25     abort();
  26
  27   exit(0);
  28 }