NationalSecurityAgency/ghidra · error

%s: unrecognized option `--%s'

Error message

%s: unrecognized option `--%s'

What it means

GNU getopt emits this when a `--long-option` token matches no entry in the longopts table. The function walks all long options, finds no exact or prefix match, and (in getopt_long_only) confirms the first character isn't a valid short option. If opterr is non-zero (the default), it prints this diagnostic to stderr and returns '?' for the token.

Source

Thrown at GPL/DemanglerGnu/src/demangler_gnu_v2_24/c/getopt.c:764

	    {
	      *(pfound->flag) = pfound->val;
	      return 0;
	    }
	  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);

View on GitHub (pinned to d5f144c24d)

Solutions

  1. Run the tool with `--help` to list valid long options
  2. Correct the typo in the option name
  3. Confirm the tool version matches the documentation you followed

Example fix

// before
./c++filt --verbsoe input.txt
// after
./c++filt --verbose input.txt
Defensive patterns

Strategy: validation

Validate before calling

// Validate that all long options in argv exist in the longopts table
#include <string.h>
static int is_known_long_opt(const char *token, const struct option *longopts) {
    const char *name = token + 2; // skip "--"
    const char *eq = strchr(name, '=');
    size_t len = eq ? (size_t)(eq - name) : strlen(name);
    for (const struct option *o = longopts; o->name != NULL; o++) {
        if (strncmp(o->name, name, len) == 0 && strlen(o->name) == len)
            return 1;
    }
    return 0;
}
// Before calling getopt_long, scan argv for unknown --options
for (int i = 1; i < argc; i++) {
    if (argv[i][0] == '-' && argv[i][1] == '-' && argv[i][2] != '\0') {
        if (!is_known_long_opt(argv[i], longopts))
            fprintf(stderr, "Warning: unknown option %s\n", argv[i]);
    }
}

Type guard

static int is_valid_long_option(const char *opt, const struct option *longopts) {
    if (!opt || opt[0] != '-' || opt[1] != '-') return 0;
    const char *name = opt + 2;
    for (const struct option *o = longopts; o->name; o++) {
        if (strcmp(o->name, name) == 0) return 1;
    }
    return 0;
}

Try / catch

// Check getopt return value for '?'
int c;
while ((c = getopt_long(argc, argv, optstring, longopts, NULL)) != -1) {
    if (c == '?') {
        fprintf(stderr, "Usage: %s [--known-options] args\n", argv[0]);
        exit(EXIT_FAILURE);
    }
    // handle valid options...
}

Prevention

When it happens

Trigger: User passes `--foo` where `foo` is not the `name` field of any struct option in longopts. In getopt_long_only mode, also fires when the token isn't a valid short option either (my_index returns NULL). Requires opterr != 0.

Common situations: Typo in a long option name (e.g. `--verison` for `--version`); using an option from a newer/older tool version where it was renamed or removed; copy-pasting a command from docs for a different build.

Related errors

AI-assisted analysis of NationalSecurityAgency/ghidra@d5f144c24d (2026-08-14). Data as JSON: /api/errors/942ba314f4943d5e. Report an issue: GitHub.