Comment by bri3d
1 day ago
I tried this with clang ASAN. Nothing happens. It won't catch this bug. ASAN detects the presence of incorrect behavior, not the absence of correct behavior.
There's no use-after-free, use-after-return, use-after-scope, or OOB access here. It's a case of "an allocated stack variable is dynamically read without being initialized only in a runtime case," which afaik no standard analyzer will catch.
The best way to identify this would be to require all locals to be initialized as a matter of policy (very unlikely to fly in a games studio, especially back then, due to the perceived performance overhead) or to debug with a form of stack initialization enabled, like "-ftrivial-auto-var-init=pattern" which while it doesn't catch the issue statically, does make it appear pretty quickly in QA (I tested).
Thanks for the investigation. Oops, it seems like MSan (memory sanitizer) is the appropriate tool that detects uninitialized reads? https://stackoverflow.com/questions/68576464/clang-sanitizer...
I only use UBSan and ASan on my own programs because I tend not to make mistakes about initialization. So my knowledge is incomplete with respect to auditing other people's code, which can have different classes of errors than mine.
Thank goodness that every language that is newer than C and C++ doesn't repeat these design mistakes, and doesn't require these awkward sanitizer tools that are introduced decades after the fact.