linux-kernel - Re: arch/x86/include/asm/processor.h:698:16: sparse: sparse: incorrect type in initializer (different address spaces)

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Date: Mon, 04 Mar 2024 08:07:43 +0100
From: Thomas Gleixner <tglx@...utronix.de>
To: Uros Bizjak <ubizjak@...il.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>, kernel test robot
 <lkp@...el.com>, oe-kbuild-all@...ts.linux.dev,
 linux-kernel@...r.kernel.org, Arjan van de Ven <arjan@...ux.intel.com>,
 x86@...nel.org, Luc Van Oostenryck <luc.vanoostenryck@...il.com>, Sparse
 Mailing-list <linux-sparse@...r.kernel.org>, "Paul E. McKenney"
 <paulmck@...nel.org>
Subject: Re: arch/x86/include/asm/processor.h:698:16: sparse: sparse:
 incorrect type in initializer (different address spaces)

On Mon, Mar 04 2024 at 06:42, Uros Bizjak wrote:

> On Mon, Mar 4, 2024 at 12:49 AM Thomas Gleixner <tglx@...utronix.de> wrote:
>>
>> On Sun, Mar 03 2024 at 21:24, Uros Bizjak wrote:
>> > On Sun, Mar 3, 2024 at 9:21 PM Uros Bizjak <ubizjak@...il.com> wrote:
>> >> On Sun, Mar 3, 2024 at 9:10 PM Thomas Gleixner <tglx@...utronix.de> wrote:
>> >> > That's so sad because it would provide us compiler based __percpu
>> >> > validation.
>> >>
>> >> Unfortunately, the c compiler can't strip qualifiers, so typeof() is
>> >> of limited use also when const and volatile qualifiers are used.
>> >> Perhaps some extension could be introduced to c standard to provide an
>> >> unqualified type, e.g. typeof_unqual().
>> >
>> > Oh, there is one in C23 [1].
>>
>> Yes. I found it right after ranting.
>>
>> gcc >= 14 and clang >= 16 have support for it of course only when adding
>> -std=c2x to the command line.
>>
>> Sigh. The name space qualifiers are non standard and then the thing
>> which makes them more useful is hidden behind a standard.
>
> With GCC, you can use __typeof_unqual__ (please note underscores)
> without -std=c2x [1]:
>
> "... Alternate spelling __typeof_unqual__ is available in all C modes
> and provides non-atomic unqualified version of what __typeof__
> operator returns..."
>
> Please also see the example in my last post. It can be compiled without -std=...

With gcc >= 14. Not so with clang...