Is the advantage over an enum not kind of small? We're seeing bugs here because people tried to do the right thing but the tooling has absolutely no way of helping anybody to do that. Simply preventing accidental mistakes would prevent these. Adding complexity to make it harder (though never impossible) for consumers to misuse the API in a complex way seems like it's potentially going to far.

Then again, it's been years since I used this kind of C, so maybe my instincts are rusty here (no rust-pun intended!)