: Correctly pass target size, not size change to ASan annotator

[Curtis J Bezault (cbezault)]

Jonathan Emmett (@joemmett) experienced ASan errors while attempting to build and run the compiler under ASan after my ASan vector change.
Upon inspection of the failure point Casey Carter (@CaseyCarter) noticed that we were passing the change of the size to the ASan annotator guard instead of the absolute target size in both _Resize and assign.

Casey and I also would like to see more vector tests running with ASan turned on but it is difficult to insert /fsanitize=address into an arbitrary matrix because it currently only supports the default IDLs and clang-cl currently does not support debug flavors of the CRT.

[Stephan T. Lavavej (StephanTLavavej)]

I think we should consider renaming _Asan_extend_guard/_ASAN_VECTOR_EXTEND_GUARD since the "absolute size" usage is not obvious, especially when _Modify_annotation/_ASAN_VECTOR_MODIFY takes a relative size. However, that can be done in another PR.

[Curtis J Bezault (cbezault)]

Thanks for the quick review guys.

[Curtis J Bezault (cbezault)]

Stephan T. Lavavej (@StephanTLavavej) I totally agree. I think I named it extend guard because I had gotten mixed up between refactors whether it took a new absolute size or a delta, which is exactly the same refactor that missed these three call sites.

[Stephan T. Lavavej (StephanTLavavej)]

I'm mirroring this to the MSVC-internal repo - please notify me if any further changes are pushed.

[Stephan T. Lavavej (StephanTLavavej)]

Thanks Curtis J Bezault (@cbezault), Jonathan Emmett (@joemmett), and Casey Carter (@CaseyCarter) for finding and fixing this bug! 🐞 ✅ 😻