bf-sign-1.c

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

main ()
{
  struct  {
    signed int s:3;
    unsigned int u:3;
    int i:3;
  } x = {-1, -1, -1};

  if (x.u != 7)
    abort ();
  if (x.s != - 1)
    abort ();

  if (x.i != -1 && x.i != 7)
    abort ();

  exit (0);
}