From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Rikard Falkeborn <rikard.falkeborn@gmail.com>,
Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
Yury Norov <yury.norov@gmail.com>,
linux-kernel@vger.kernel.org, Ard Biesheuvel <ardb@kernel.org>,
Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH] linux/bits.h: Fix compilation error with GENMASK
Date: Fri, 21 May 2021 14:59:03 +0300 [thread overview]
Message-ID: <YKeghxRY4FeOKuwb@smile.fi.intel.com> (raw)
In-Reply-To: <20210520134112.ee15f156f1b7dbd3d8f16471@linux-foundation.org>
On Thu, May 20, 2021 at 01:41:12PM -0700, Andrew Morton wrote:
> On Tue, 11 May 2021 22:37:15 +0200 Rikard Falkeborn <rikard.falkeborn@gmail.com> wrote:
>
> > --- a/include/linux/const.h
> > +++ b/include/linux/const.h
> > @@ -3,4 +3,12 @@
> >
> > #include <vdso/const.h>
> >
> > +/*
> > + * This returns a constant expression while determining if an argument is
> > + * a constant expression, most importantly without evaluating the argument.
> > + * Glory to Martin Uecker <Martin.Uecker@med.uni-goettingen.de>
> > + */
> > +#define __is_constexpr(x) \
> > + (sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int *)8)))
>
> Boggle.
>
> Could someone please sometime enhance that comment a bit? What need
> does this thing satisfy and how on earth does it work?
Some summary based on (links from) https://vegard.wiki/w/is_constexpr() ?
--
With Best Regards,
Andy Shevchenko
next prev parent reply other threads:[~2021-05-21 11:59 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-11 20:37 [PATCH] linux/bits.h: Fix compilation error with GENMASK Rikard Falkeborn
2021-05-12 12:53 ` Ard Biesheuvel
2021-05-20 18:46 ` Rikard Falkeborn
2021-05-20 19:44 ` Yury Norov
2021-05-20 20:15 ` Arnd Bergmann
2021-05-20 20:41 ` Andrew Morton
2021-05-21 11:59 ` Andy Shevchenko [this message]
2021-05-21 10:15 ` Andy Shevchenko
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