Why no negative hex?

I'd write something like this:

  long long parseLongSomehow(char *s) {
      if (isspace(s[0])) {
          return parseLongSomehow(s + 1);
      } else if (s[0] == '-') {
          return -parseLongSomehow(s + 1);
      } else if (s[0] == '0' && s[1] == 'x') {
          return strtoull(s + 2, 16);
      } else {
          return strtoull(s, 10);
      }
  }

That doesn't handle negative values smaller than LONG_LONG_MIN gracefully, though. Also doesn't do error handling.