There is a comparison between a pointer and a char in MethodMatcher::canonicalize:

bool MethodMatcher::canonicalize(char * line, const char *& error_msg) {
  char* colon = strstr(line, "::");
  bool have_colon = (colon != NULL);
  if (have_colon) {
    // Don't allow multiple '::'
    if (colon + 2 != '\0') {
      if (strstr(colon+2, "::")) {
        error_msg = "Method pattern only allows one '::' allowed";
        return false;
      }
    }

The proper if check would `if (colon[2] != '\0')`. This was also reported by Yasumasa Suenaga.