linux-kernel - Re: [PATCH] linux/container_of.h: switch to static

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Message-ID: <YWl+hQTa4Pd1A7zg@smile.fi.intel.com>
Date:   Fri, 15 Oct 2021 16:13:41 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Rasmus Villemoes <linux@...musvillemoes.dk>
Cc:     akpm@...ux-foundation.org,
        Miguel Ojeda <miguel.ojeda.sandonis@...il.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] linux/container_of.h: switch to static_assert

On Fri, Oct 15, 2021 at 04:11:01PM +0300, Andy Shevchenko wrote:
> On Fri, Oct 15, 2021 at 11:05:30AM +0200, Rasmus Villemoes wrote:
> > _Static_assert() is evaluated already in the compiler's frontend, and
> > gives a somehat more to-the-point error, compared to the BUILD_BUG_ON
> > macro, which only fires after the optimizer has had a chance to
> > eliminate calls to functions marked with
> > __attribute__((error)). In theory, this might make builds a tiny bit
> > faster.
> > 
> > There's also a little less gunk in the error message emitted:
> > 
> > lib/sort.c: In function ‘foo’:
> > ./include/linux/build_bug.h:78:41: error: static assertion failed: "pointer type mismatch in container_of()"
> >    78 | #define __static_assert(expr, msg, ...) _Static_assert(expr, msg)
> > 
> > compared to
> > 
> > lib/sort.c: In function ‘foo’:
> > ././include/linux/compiler_types.h:322:38: error: call to ‘__compiletime_assert_2’ declared with attribute error: pointer type mismatch in container_of()
> >   322 |  _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
> > 
> > While at it, fix the copy-pasto in container_of_safe().
> 
> Thanks, Rasmus!
> Make sense to me.

Btw, shouldn't we also remove build_bug.h in the container_of.h with this?
(Or if this goes first, do we still need bug.h?)

-- 
With Best Regards,
Andy Shevchenko