NationalSecurityAgency/ghidra · error

%s: illegal option -- %c\n

Error message

%s: illegal option -- %c\n

What it means

GNU getopt's POSIX-mode diagnostic for an illegal short option. Printed (POSIX 1003.2 format) when posixly_correct is set and a short-option character is not found in optstring or is ':'. getopt then sets optopt and returns '?'. Only the diagnostic differs from the non-POSIX variant; behavior is identical.

Source

Thrown at GPL/DemanglerGnu/src/demangler_gnu_v2_41/c/getopt.c:793

    }

  /* 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;

    if (temp == NULL || c == ':')
      {
	if (opterr)
	  {
	    if (posixly_correct)
	      /* 1003.2 specifies the format of this message.  */
	      fprintf (stderr, _("%s: illegal option -- %c\n"),
		       argv[0], c);
	    else
	      fprintf (stderr, _("%s: invalid option -- %c\n"),
		       argv[0], c);
	  }
	optopt = c;
	return '?';
      }
    /* Convenience. Treat POSIX -W foo same as long option --foo */
    if (temp[0] == 'W' && temp[1] == ';')
      {
	char *nameend;
	const struct option *p;
	const struct option *pfound = NULL;
	int exact = 0;
	int ambig = 0;
	int indfound = 0;
	int option_index;

View on GitHub (pinned to d5f144c24d)

Solutions

1. Add the missing character to optstring.
2. Unset POSIXLY_CORRECT if POSIX message formatting is not required (changes the wording, not the return).
3. Set opterr = 0 to silence the diagnostic and branch on the '?' return / optopt yourself.
4. Correct the user's typo via the optopt value.

Example fix

// before: optstring omits 'z'; POSIXLY_CORRECT=1 prog -z
while ((c = getopt(argc, argv, "ab:c")) != -1) { ... }

// after
while ((c = getopt(argc, argv, "ab:cz")) != -1) { ... }

// guard the POSIX-mode illegal-option path
opterr = 0;
int c = getopt(argc, argv, "ab:c");
if (c == '?') { reportInvalidOption(optopt); }

When it happens

Trigger: POSIXLY_CORRECT (or posixly_correct) is in effect and the user passes a short option letter absent from optstring, or the reserved ':' character as an option.

Common situations: Programs run under a POSIXLY_CORRECT=1 environment, or built in an environment that defaults to POSIX mode; option letter typo; optstring not updated for a newly documented flag.

Related errors

• %s: illegal option -- %c
• %s: option `-W %s' is ambiguous
• %s: option `-W %s' doesn't allow an argument
• %s: unrecognized option `%c%s'\n
• %s: invalid option -- %c\n

AI-assisted analysis of NationalSecurityAgency/ghidra@d5f144c24d (2026-08-14). Data as JSON: /api/errors/3ab7182bacfa0810. Report an issue: GitHub.