clang version 6.0.0 (trunk 317263)

This code:

    int main(int argc, char** argv) {
      if (argc > 4);   // <-- Note semicolon!
      return 0;
    }

Gives:

    eraseme.cc:2:16: warning: if statement has empty body [-Wempty-body]
      if (argc > 4);
                   ^
    eraseme.cc:2:16: note: put the semicolon on a separate line to silence this
          warning
    1 warning generated.

This is good! And it also works for "else if" cases. But I just did the same bug and put a semicolon after a bare else:

    int main(int argc, char** argv) {
      if (argc > 4)
        return 1;
      else;  // <- Semicolon
        return 2;
      return 0;
    }

And there is no warning. This was pretty tricky to find and it seems like the same rule for "if" semicolons should just also be applied to "else".