1  /* Tail call optimizations would convert func() into the moral equivalent of:
       2  
       3         double acc = 0.0;
       4         for (int i = 0; i <= n; i++)
       5  	 acc += d;
       6         return acc;
       7  
       8     which mishandles the case where 'd' is -0.  They also initialised 'acc'
       9     to a zero int rather than a zero double.  */
      10  
      11  double func (double d, int n)
      12  {
      13    if (n == 0)
      14      return d;
      15    else
      16      return d + func (d, n - 1);
      17  }
      18  
      19  int main ()
      20  {
      21    if (__builtin_copysign (1.0, func (0.0 / -5.0, 10)) != -1.0)
      22      abort ();
      23    exit (0);
      24  }