NationalSecurityAgency/ghidra · error

%s: unrecognized option `%c%s'

Error message

%s: unrecognized option `%c%s'

What it means

Counterpart to error 20 for the single-dash form. In getopt_long_only, when a token like `-foo` matches no long option AND its first character isn't a valid short option, getopt reports it as unrecognized. The `%c%s` format prints the leading character (usually `-` or `+`) followed by the option text.

Source

Thrown at GPL/DemanglerGnu/src/demangler_gnu_v2_24/c/getopt.c:768

	  return pfound->val;
	}

      /* Can't find it as a long option.  If this is not getopt_long_only,
	 or the option starts with '--' or is not a valid short
	 option, then it's an error.
	 Otherwise interpret it as a short option.  */
      if (!long_only || argv[optind][1] == '-'
	  || my_index (optstring, *nextchar) == NULL)
	{
	  if (opterr)
	    {
	      if (argv[optind][1] == '-')
		/* --option */
		fprintf (stderr, _("%s: unrecognized option `--%s'\n"),
			 argv[0], nextchar);
	      else
		/* +option or -option */
		fprintf (stderr, _("%s: unrecognized option `%c%s'\n"),
			 argv[0], argv[optind][0], nextchar);
	    }
	  nextchar = (char *) "";
	  optind++;
	  optopt = 0;
	  return '?';
	}
    }

  /* Look at and handle the next short option-character.  */

  {
    char c = *nextchar++;
    char *temp = my_index (optstring, c);

    /* Increment `optind' when we start to process its last character.  */
    if (*nextchar == '\0')
      ++optind;

View on GitHub (pinned to d5f144c24d)

Solutions

  1. Check `--help` for valid option names
  2. Use the correct dash convention (-- for long options, - for short)
  3. Fix the typo

Example fix

// before (getopt_long_only tool)
./c++filt -nstrip input
// after
./c++filt -n input  # or --strip-underscore
Defensive patterns

Strategy: validation

Validate before calling

// For getopt_long_only, check that single-dash tokens are valid long or short options
static int is_valid_opt_long_only(const char *token, const char *optstring, const struct option *longopts) {
    if (!token || token[0] != '-' || token[1] == '\0') return 1; // not an option
    const char *name = token + 1;
    for (const struct option *o = longopts; o->name; o++) {
        if (strcmp(o->name, name) == 0) return 1;
    }
    if (strchr(optstring, name[0]) != NULL) return 1;
    return 0;
}

Type guard

static int is_known_token(const char *tok, const char *optstring, const struct option *longopts) {
    if (!tok || tok[0] != '-') return 0;
    const char *name = tok + 1;
    for (const struct option *o = longopts; o->name; o++)
        if (strcmp(o->name, name) == 0) return 1;
    return strchr(optstring, name[0]) != NULL;
}

Try / catch

int c;
while ((c = getopt_long_only(argc, argv, optstring, longopts, NULL)) != -1) {
    if (c == '?') { exit(EXIT_FAILURE); }
}

Prevention

When it happens

Trigger: getopt_long_only is in use; user passes `-unknown` or `+unknown`; my_index(optstring, *nextchar) returns NULL (first char not a valid short option). opterr must be non-zero.

Common situations: Passing a single-dash long-style option that doesn't exist; using getopt_long_only (common in tools like c++filt) and mistyping an option; confusing the option syntax of getopt_long vs getopt_long_only.

Related errors

AI-assisted analysis of NationalSecurityAgency/ghidra@d5f144c24d (2026-08-14). Data as JSON: /api/errors/78fee5f816ad6fe4. Report an issue: GitHub.