aaron.ballman added a comment.

In D124726#3516346 <https://reviews.llvm.org/D124726#3516346>, @nathanchance 
wrote:

> I see an instance of this warning in the Linux kernel due to the "Now, for 
> unknown directives inside a skipped conditional block, we diagnose the 
> unknown directive as a warning if it is sufficiently similar to a directive 
> specific to preprocessor conditional blocks" part of this change:
>
>   arch/x86/crypto/aesni-intel_asm.S:532:8: warning: invalid preprocessing 
> directive, did you mean '#if'? [-Wunknown-directives]
>                                           # in in order to perform
>                                             ^
>   arch/x86/crypto/aesni-intel_asm.S:547:8: warning: invalid preprocessing 
> directive, did you mean '#if'? [-Wunknown-directives]
>                                           # in in order to perform
>                                             ^
>   2 warnings generated.

Oh wow, that's a really neat one!

> This is a comment within an assembler file that will be preprocessed (this is 
> a 32-bit x86 build and the block is guarded by `#ifdef __x86_64__` on line 
> 500):
>
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/x86/crypto/aesni-intel_asm.S?h=v5.18-rc7#n532
>
> Is there anything that can be done to improve this heuristic for this case? I 
> can try to push a patch to change the comment style for this one instance but 
> I always worry that a warning of this nature will appear in the future and 
> result in the kernel disabling this warning entirely.

Ah, and we don't get an error for those because of special logic: 
https://github.com/llvm/llvm-project/blob/main/clang/lib/Lex/PPDirectives.cpp#L1243
 and it looks like we may need similar logic before issuing the warnings as 
well.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D124726/new/

https://reviews.llvm.org/D124726

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