Xcode: LLVM's flag -Wunreachable-code not working?

Question

In light of the Apple's recent goto fail, I've decided to add -Wunreachable-code to existing LLVM flags (-Wall and -Wextra). However, the flag doesn't (seem to) work. For example, placing code after return; doesn't trigger the warning. Is the flag even functional (GCC supposedly removed it)? What am I missing?

Answer 1

It works for me when:

1. I enter the flag here
2. Then clean project
3. I receive this warning when I do a rebuild