It is documented in the gcc and clang documentation. It's also described in the gcc manpage, but not the clang one. I don't know how "common" it is, but when d

It is documented in the gcc and clang documentation. It's also described in the gcc manpage, but not the clang one. I don't know how "common" it is, but when dealing with third party code, I run across <> / "" confusion quite commonly, so when that's a significant part of your job, you'll probably stumble upon this flag eventually.