Re: + uapi-linux-consth-prefer-iso-friendly-__typeof__.patch added to mm-nonmm-unstable branch

[Petr Vorel <pvorel@suse.cz>]

> On Wed, Apr 12, 2023 at 9:24 AM Andrew Morton <akpm@linux-foundation.org> wrote:


> > The patch titled
> >      Subject: uapi/linux/const.h: prefer ISO-friendly __typeof__
> > has been added to the -mm mm-nonmm-unstable branch.  Its filename is
> >      uapi-linux-consth-prefer-iso-friendly-__typeof__.patch

> > This patch will shortly appear at
> >      https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/uapi-linux-consth-prefer-iso-friendly-__typeof__.patch

> > This patch will later appear in the mm-nonmm-unstable branch at
> >     git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

> > Before you just go and hit "reply", please:
> >    a) Consider who else should be cc'ed
> >    b) Prefer to cc a suitable mailing list as well
> >    c) Ideally: find the original patch on the mailing list and do a
> >       reply-to-all to that, adding suitable additional cc's

> > *** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

> > The -mm tree is included into linux-next via the mm-everything
> > branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
> > and is updated there every 2-3 working days

> > ------------------------------------------------------
> > From: Kevin Brodsky <kevin.brodsky@arm.com>
> > Subject: uapi/linux/const.h: prefer ISO-friendly __typeof__
> > Date: Tue, 11 Apr 2023 10:27:47 +0100

> > typeof is (still) a GNU extension, which means that it cannot be used when
> > building ISO C (e.g.  -std=c99).  It should therefore be avoided in uapi
> > headers in favour of the ISO-friendly __typeof__.

> > Unfortunately this issue could not be detected by
> > CONFIG_UAPI_HEADER_TEST=y as the __ALIGN_KERNEL() macro is not expanded in
> > any uapi header.

> > Link: https://lkml.kernel.org/r/20230411092747.3759032-1-kevin.brodsky@arm.com
> > Fixes: d6fc9fcbaa65 ("kbuild: compile-test exported headers to ensure they are self-contained")


> This tag is wrong.

> The correct one is:

> Fixes: a85cbe6159ff ("uapi: move constants from <linux/kernel.h> to
> <linux/const.h>")

I'm sorry if I misinterpreted the history. The reason why I think it was
d6fc9fcbaa65 (which introduced -std=c90) is because there was already some
typeof() uses before this commit (uapi/linux/kernel.h and
uapi/linux/netfilter/x_tables.h).

Kind regards,
Petr

> Reviewed-by: Masahiro Yamada <masahiroy@kernel.org>




> > Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com>
> > Reported-by: Ruben Ayrapetyan <ruben.ayrapetyan@arm.com>
> > Tested-by: Ruben Ayrapetyan <ruben.ayrapetyan@arm.com>
> > Reviewed-by: Petr Vorel <pvorel@suse.cz>
> > Tested-by: Petr Vorel <pvorel@suse.cz>
> > Cc: Masahiro Yamada <masahiroy@kernel.org>
> > Cc: Sam Ravnborg <sam@ravnborg.org>
> > Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> > ---

> >  include/uapi/linux/const.h |    2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)

> > --- a/include/uapi/linux/const.h~uapi-linux-consth-prefer-iso-friendly-__typeof__
> > +++ a/include/uapi/linux/const.h
> > @@ -28,7 +28,7 @@
> >  #define _BITUL(x)      (_UL(1) << (x))
> >  #define _BITULL(x)     (_ULL(1) << (x))

> > -#define __ALIGN_KERNEL(x, a)           __ALIGN_KERNEL_MASK(x, (typeof(x))(a) - 1)
> > +#define __ALIGN_KERNEL(x, a)           __ALIGN_KERNEL_MASK(x, (__typeof__(x))(a) - 1)
> >  #define __ALIGN_KERNEL_MASK(x, mask)   (((x) + (mask)) & ~(mask))

> >  #define __KERNEL_DIV_ROUND_UP(n, d) (((n) + (d) - 1) / (d))
> > _

> > Patches currently in -mm which might be from kevin.brodsky@arm.com are

> > uapi-linux-consth-prefer-iso-friendly-__typeof__.patch