Re: [PATCH v5 1/1] x86/cpu: Make sure flag_is_changeable_p() is always being used

[H. Peter Anvin]

On November 8, 2024 5:29:52 PM GMT+01:00, Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx> wrote:
>On Fri, Nov 08, 2024 at 04:48:16PM +0100, H. Peter Anvin wrote:
>> On November 8, 2024 4:41:16 PM GMT+01:00, Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx> wrote:
>> >On Fri, Nov 08, 2024 at 04:35:17PM +0100, H. Peter Anvin wrote:
>> >> On November 8, 2024 4:30:10 PM GMT+01:00, Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx> wrote:
>
>...
>
>> >> >See also commit 6863f5643dd7 ("kbuild: allow Clang to find unused static
>> >> >inline functions for W=1 build").
>
>^^^ (1)
>
>...
>
>> >> But another question: why the hell does clang complain about an unused static inline function?!
>> >
>> >Does (1) shed a bit of light to this?
>> 
>> How on earth is that supposed to work?! We have static inline functions in
>> headers all over the place that are only used in certain circumstances.
>> 
>> Is this a good thing, really? Or is it noise?
>
>This is a good question and IIRC somebody else already asked something similar.
>
>Clang people are Cc'ed here, I leave this to them to comment on,
>I am not an expert here.
>

So there are two questions:

1. How? How does this work, technically? 
2. Why? Is this really the right thing to do, or will it result in a bunch of unnecessary #ifdeffery instead?