I have to double check this, but the approach should be theoretically sound since we are quite strict with what functions are considered to have known call-site

I have to double check this, but the approach should be theoretically sound since we are quite strict with what functions are considered to have known call-sites: Function has to be internal (as in no visibility from outside) + no indirect uses (so no saving a pointer to the function somewhere). This should be enough to solve the problem you are thinking about.