https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95057
--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> --- It can't. The warning isn't flow sensitive, doesn't know about assignments, conditionals etc. What you are thinking of is something that can be only done much later, but at that point one risks that there is compiler-introduced dead code that wasn't really the fault of the user.
