[compiler-rt] [clang] [clang][UBSan] Add implicit conversion check for bitfields (PR #75481)

[Axel Lundberg via cfe-commits]

Zonotora wrote:

> Is is UB?

Don't think so? To quote [1]:
> Issues caught by these sanitizers are not undefined behavior, but are often unintentional.

where "these sanitizers" refer to `implicit-unsigned-integer-truncation`, `implicit-signed-integer-truncation` and `implicit-integer-sign-change`.

[1] https://clang.llvm.org/docs/UndefinedBehaviorSanitizer.html

https://github.com/llvm/llvm-project/pull/75481