rem: if (optind < argc) tsort (argv[optind]); else tsort ("-");
add: ok = tsort (optind == argc ? "-" : argv[optind]);
context: main (int argc, char **argv){  int opt;  program_name = argv[0];  setlocale (LC_ALL, "");  bindtextdomain (PACKAGE, LOCALEDIR);  textdomain (PACKAGE);  atexit (close_stdout);  exit_status = 0;  parse_long_options (argc, argv, PROGRAM_NAME, PACKAGE, VERSION,		      AUTHORS, usage);  while ((opt = getopt_long (argc, argv, "", long_options, NULL)) != -1)    switch (opt)      {      case 0:			/* long option */	break;      default:	usage (EXIT_FAILURE);      }  have_read_stdin = 0;  if (optind + 1 < argc)    {      error (0, 0, _("only one argument may be specified"));      usage (EXIT_FAILURE);    }  if (optind < argc)    tsort (argv[optind]);  else    tsort ("-");  if (have_read_stdin && fclose (stdin) == EOF)    error (EXIT_FAILURE, errno, _("standard input"));  exit (exit_status == 0 ? EXIT_SUCCESS : EXIT_FAILURE);}