[clang] [C2y] Claim partial conformance to WG14 N3244 (PR #98525)

[Aaron Ballman via cfe-commits]

AaronBallman wrote:

Thank you for letting me know, I've pushed a fix for that.

Curiously, it seems `_Alignof` on an expression always returns the *preferred* alignment and not the actual alignment. This is consistent with GCC, even if it's a bit surprising: https://godbolt.org/z/nvKx98ff9

https://github.com/llvm/llvm-project/pull/98525