It looks like (a) this is a warning, not an error (why? the code is always wrong) and (b) the warning was added in clang 21 which came out this year. I also suspect that it wouldn't be able to detect complex cases that require interprocedural analysis.

The bug I saw happened a few years ago, and convinced me to switch to Rust where it simply cannot happen.

A warning in C, C++ is the compiler saying "this is terribly broken, won't do what you want and I will exploit this". As opposed to an error, which means "I don't even know what you mean". Taking warnings lightly isn't the way to go in C or C++.