char *makeString (char *s)
     /*@ensures MaxSet(result) == 12 @*/
     /*@requires MaxRead (s) == 3@*/
     /*@ensures notnull result@*/
{
  return s; /* should warn about ensures MaxSet not satisfied */
} 

int test (char *s)
{
  char *t = makeString (s);

  t[3] = 'a';
  t[12] = 'b';
  t[13] = 'c'; /* error */
}
