[clang] [Clang] Overflow Idiom Exclusions (PR #100272)

[Justin Stitt via cfe-commits]

JustinStitt wrote:

> > Right, unsigned overflow is well-defined. This isn't about the semantics of "undefined-ness". We want the unsigned sanitizer ON but some of the things it reports are noisy -- that's what this PR is about
> 
> "Idiom" seems to vague to me. kernel has own opinion on what is ideom, other users may have different ideoms.

What's a better word? Pattern?

> 
> Also so far we were able to avoid behavior tweaking flags in UBSAN. like `-fno-sanitize-overflow-idioms` (e.g. we have them in Asan). In UBSAN we were able to express as sets of checks. It would be nice to continue these way.
> 
> WDYT on splitting existing checks into smaller checks with verbose naming?

Yes, that's a good idea. Doing it that way, we can add more "idioms" in the future and users can opt into those ones.

https://github.com/llvm/llvm-project/pull/100272