linux-kernel - Re: [PATCH 02/10] compiler.h: add is_const() as a replacement of __is

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Message-ID: <CAMZ6RqJGqBqvgxzp5yPFY1pk0WkkwEMM34qU-dZ3kXfsnKaqEg@mail.gmail.com>
Date: Sat, 7 Dec 2024 21:45:05 +0900
From: Vincent Mailhol <vincent.mailhol@...il.com>
To: Martin Uecker <muecker@...g.de>
Cc: David Laight <David.Laight@...lab.com>, Linus Torvalds <torvalds@...ux-foundation.org>, 
	Luc Van Oostenryck <luc.vanoostenryck@...il.com>, Nathan Chancellor <nathan@...nel.org>, 
	Nick Desaulniers <ndesaulniers@...gle.com>, Bill Wendling <morbo@...gle.com>, 
	Justin Stitt <justinstitt@...gle.com>, Yury Norov <yury.norov@...il.com>, 
	Rasmus Villemoes <linux@...musvillemoes.dk>, Kees Cook <kees@...nel.org>, 
	"Gustavo A. R. Silva" <gustavoars@...nel.org>, Jani Nikula <jani.nikula@...ux.intel.com>, 
	Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>, Rodrigo Vivi <rodrigo.vivi@...el.com>, 
	Tvrtko Ursulin <tursulin@...ulin.net>, David Airlie <airlied@...il.com>, 
	Simona Vetter <simona@...ll.ch>, Suzuki K Poulose <suzuki.poulose@....com>, 
	Mike Leach <mike.leach@...aro.org>, James Clark <james.clark@...aro.org>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, 
	Rikard Falkeborn <rikard.falkeborn@...il.com>, 
	"linux-sparse@...r.kernel.org" <linux-sparse@...r.kernel.org>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, 
	"llvm@...ts.linux.dev" <llvm@...ts.linux.dev>, 
	"linux-hardening@...r.kernel.org" <linux-hardening@...r.kernel.org>, 
	"intel-gfx@...ts.freedesktop.org" <intel-gfx@...ts.freedesktop.org>, 
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>, 
	"coresight@...ts.linaro.org" <coresight@...ts.linaro.org>, 
	"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 02/10] compiler.h: add is_const() as a replacement of __is_constexpr()

On Sat. 7 Dec. 2024 at 17:39, Martin Uecker <muecker@...g.de> wrote:
> Am Freitag, dem 06.12.2024 um 16:26 +0900 schrieb Vincent Mailhol:
> > > On Fri. 6 Dec. 2024 at 15:40, Martin Uecker <muecker@...g.de> wrote:
> > > > > Am Freitag, dem 06.12.2024 um 02:25 +0000 schrieb David Laight:
> > > > > > > From: Vincent Mailhol
> > > > > > > > > Sent: 05 December 2024 15:31

(...)

> > > > > > > > > @Martin, do you agree that I remove the accreditation?
> > >
> > > So, do you agree to have the accreditation removed in compiler.h?
> > > Personally, I do not mind. I am also OK to remove you from the
> > > documentation and add you to the CREDITS file if you'd like to.
>
> Sorry, I somehow didn't read this part. Please do whatever you think is
> most appropriate (but please update my email to the new above if it
> still appears anywhere).

OK. Then I will remove the accreditation from the  compiler.h
documentation and instead add an entry in the CREDITS file in a
separate patch. I think this is the most appropriate way.

> I find it amazing how much time the Linux kernel community spends
> revising code to make it work perfectly.
>
> Still, I am wondering whether some of this time and effort should not
> be targeted at C compilers and language work to make these macro
> hacks unnecessary?

It seems to me that the long term solution to this problem are the
constexpr functions.

But the core issue is that before getting this support in Linux, we
have to wait for this to be added to the C2Y draft, then implemented
in the compilers (probably just reusing the C++ constexpr functions)
and finally wait maybe one more decade for the C2Y support to reach
the kernel. For reference the kernel supports C11 only from 2022… So
maybe we will see those in the kernel around 2037? Meanwhile, we have
to deal with those hacks.


Yours sincerely,
Vincent Mailhol