src/mjson.c: unused variable suspected by clang

[git001]

Clang creates a warning about unused variables which was discovered by HAPoxy community https://github.com/haproxy/haproxy/issues/1868

One suggestion is to create a pragma for clang https://github.com/haproxy/haproxy/issues/1868#issuecomment-1250049715
Another option is to add a new option like -D MJSON_DEBUG=1 and change the code accordingly.

Something like the code below instead of this block https://github.com/cesanta/mjson/blob/master/src/mjson.c#L186-L192.

static int plen1(const char *s) {
  int i = 0;
#if MJSON_DEBUG
  int n = 0;
#endif

  while (s[i] != '\0' && s[i] != '.' && s[i] != '[') {
    i += s[i] == '\\' ? 2 : 1;
#if MJSON_DEBUG
    n++;
#endif
  }

#if MJSON_DEBUG
  printf("PLEN1: s: [%s], [%.*s] => %d\n", s, i, s, n);
#endif

  return n;
}

As I would like to create a Pull Request to mjson and then add the new version to HAProxy please let me know what's your preferred way is to solve the clang warning.

[chipitsine]

this has raised just few days ago because is was detected by Fedora Rawhide which has switched to clang-15. I guess it is new rule in clang-15

[jcorporation]

I stumbled also about this issue:

/myMPD/dist/mjson/mjson.c:195:14: error: variable 'n' set but not used [-Werror,-Wunused-but-set-variable]
  int i = 0, n = 0;
             ^
/myMPD/dist/mjson/mjson.c:743:17: error: variable 'n' set but not used [-Werror,-Wunused-but-set-variable]
  int sign = 1, n = 0;