rem: if (output_stream == NULL)
add: fopen_ok = (output_stream != NULL); fopen_errno = errno; files_created += fopen_ok; sigprocmask (SIG_SETMASK, &oldset, NULL);  if (! fopen_ok)
context: create_output_file (void){  output_filename = make_filename (files_created);  output_stream = fopen (output_filename, "w");  if (output_stream == NULL)    {      error (0, errno, "%s", output_filename);      cleanup_fatal ();    }  files_created++;  bytes_written = 0;}