nodejs/node · error

missing servers

Error message

missing servers

What it means

Printed by ahost's main() at ahost.c:120 when the -s flag is passed but state.optarg is NULL — meaning no argument was supplied for the -s option. The message 'missing servers' is printed to stderr, followed by a call to usage(). The optarg being NULL typically indicates a malformed command line where -s is the last token with no following value.

Source

Thrown at deps/cares/src/tools/ahost.c:120

        options.ndomains++;
        options.domains = (char **)realloc(
          options.domains, (size_t)options.ndomains * sizeof(char *));
        options.domains[options.ndomains - 1] = strdup(state.optarg);
        break;
      case 't':
        if (ares_strcaseeq(state.optarg, "a")) {
          addr_family = AF_INET;
        } else if (ares_strcaseeq(state.optarg, "aaaa")) {
          addr_family = AF_INET6;
        } else if (ares_strcaseeq(state.optarg, "u")) {
          addr_family = AF_UNSPEC;
        } else {
          usage();
        }
        break;
      case 's':
        if (state.optarg == NULL) {
          fprintf(stderr, "%s", "missing servers");
          usage();
          break;
        }
        if (servers) {
          free(servers);
        }
        servers = strdup(state.optarg);
        break;
      case 'h':
      case '?':
        print_help_info_ahost();
        break;
      default:
        usage();
        break;
    }
  }

View on GitHub (pinned to 1b2de5e052)

Solutions

  1. Provide a valid server IP after -s: 'ahost -s 8.8.8.8 example.com'.
  2. If building the command in a script, check that the server variable is non-empty before including -s.
  3. Quote the argument properly: 'ahost -s "$SERVER_IP" example.com'.
  4. Review the full command line for option ordering issues — put -s and its value before positional arguments.

Example fix

// before: missing -s argument
ahost -s example.com
// -> 'missing servers' + usage

// after: provide server IP
ahost -s 8.8.8.8 example.com
Defensive patterns

Strategy: validation

Validate before calling

// Validate -s argument presence before invoking ahost
if [ -z "$SERVER_IP" ]; then
    echo "error: server IP is required for -s" >&2
    exit 1
fi
ahost -s "$SERVER_IP" "$DOMAIN"

Prevention

When it happens

Trigger: Invoking ahost with '-s' as the last argument or followed by another flag (e.g., 'ahost -s -t a example.com' where -t is consumed as the -s argument by some getopt implementations, or 'ahost -s' with nothing after). The ares_getopt parser sets state.optarg to NULL when no value follows the option.

Common situations: A user forgets to provide the server list after -s. A shell script constructs the command dynamically and the server variable is empty, producing a command where no argument is bound to -s. Option ordering causes another flag to be interpreted as the -s argument.

Related errors

AI-assisted analysis of nodejs/node@1b2de5e052 (2026-08-13). Data as JSON: /api/errors/cdf7be4bb8905cbb. Report an issue: GitHub.