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

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Message-ID: <CAFULd4aEe2KU=UXEt2=GeLQq2uTSFvydBiwAdSa7B6T61Am=5w@mail.gmail.com>
Date: Mon, 4 Mar 2024 06:42:57 +0100
From: Uros Bizjak <ubizjak@...il.com>
To: Thomas Gleixner <tglx@...utronix.de>
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 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=...

[1] https://gcc.gnu.org/onlinedocs/gcc/Typeof.html

Uros.