From: David Laight <David.Laight@ACULAB.COM>
To: 'Linus Torvalds' <torvalds@linuxfoundation.org>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Matthew Wilcox (Oracle)" <willy@infradead.org>,
Christoph Hellwig <hch@infradead.org>,
Andrew Morton <akpm@linux-foundation.org>,
"Andy Shevchenko" <andriy.shevchenko@linux.intel.com>,
Dan Carpenter <dan.carpenter@linaro.org>,
Arnd Bergmann <arnd@kernel.org>,
"Jason@zx2c4.com" <Jason@zx2c4.com>,
"pedro.falcato@gmail.com" <pedro.falcato@gmail.com>,
Mateusz Guzik <mjguzik@gmail.com>,
"linux-mm@kvack.org" <linux-mm@kvack.org>
Subject: RE: [PATCH 3/7] compiler.h: Add __if_constexpr(expr, if_const, if_not_const)
Date: Thu, 25 Jul 2024 08:45:07 +0000 [thread overview]
Message-ID: <db4143302c0847aabb15a621b60a59c0@AcuMS.aculab.com> (raw)
In-Reply-To: <CAHk-=wiQr8U7nCnUci3_20vKyU2cx0BQ7HRNqxsHm+EP-6PCPQ@mail.gmail.com>
From: Linus Torvalds
> Sent: 24 July 2024 20:49
>
> On Wed, 24 Jul 2024 at 07:30, David Laight <David.Laight@aculab.com> wrote:
> >
> > Implemented using _Generic() for portibility.
>
> I do think this is ultimately the clearer implementation, if only
> because the underlying trick it uses does very much depend on a very
> special oddity in the C type system.
>
> So then using the type comparison with _Generic() is rather natural,
> and allows for picking other things than 0/1 as a result.
>
> However, there is NO WAY this is a "portability" enhancement.
The old code relied on sizeof(void) which is invalid C.
So this version can be used when that gcc extension isn't enabled.
While the linux kernel rather assumes it other builds (eg nolibc) don't.
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
next prev parent reply other threads:[~2024-07-25 8:45 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-07-24 14:26 [PATCH 0/7] minmax: reduce compilation time David Laight
2024-07-24 14:28 ` [PATCH 1/7] minmax: Put all the clamp() definitions together David Laight
2024-07-24 14:29 ` [PATCH 2/7] minmax: Use _Static_assert() instead of static_assert() David Laight
2024-07-24 14:29 ` [PATCH 3/7] compiler.h: Add __if_constexpr(expr, if_const, if_not_const) David Laight
2024-07-24 17:32 ` Arnd Bergmann
2024-07-25 9:12 ` David Laight
2024-07-24 19:48 ` Linus Torvalds
2024-07-25 8:45 ` David Laight [this message]
2024-07-24 14:30 ` [PATCH 4/7] minmax: Simplify signedness check David Laight
2024-07-24 16:48 ` Arnd Bergmann
2024-07-24 20:02 ` Linus Torvalds
2024-07-25 9:00 ` David Laight
2024-07-25 17:02 ` Linus Torvalds
2024-07-26 9:43 ` Lorenzo Stoakes
2024-07-26 12:57 ` David Laight
2024-07-26 13:27 ` Lorenzo Stoakes
2024-07-25 13:24 ` kernel test robot
2024-07-25 16:39 ` David Laight
2024-07-24 14:31 ` [PATCH 5/7] minmax: Factor out the zero-extension logic from umin/umax David Laight
2024-07-24 14:32 ` [PATCH 6/7] minmax: Optimise _Static_assert() check in clamp() David Laight
2024-07-24 14:33 ` [PATCH 7/7] minmax: minmax: Add __types_ok3() and optimise defines with 3 arguments David Laight
2024-07-24 17:03 ` Arnd Bergmann
2024-07-25 9:07 ` David Laight
2024-07-24 19:34 ` [PATCH 0/7] minmax: reduce compilation time Lorenzo Stoakes
2024-07-24 19:52 ` Linus Torvalds
2024-07-26 18:12 ` Lorenzo Stoakes
2024-07-26 18:24 ` Linus Torvalds
2024-07-26 18:56 ` Lorenzo Stoakes
2024-07-26 19:21 ` Lorenzo Stoakes
2024-07-26 21:36 ` Linus Torvalds
2024-07-26 21:46 ` Jens Axboe
2024-07-26 22:48 ` Linus Torvalds
2024-07-27 15:30 ` Jens Axboe
2024-07-27 15:38 ` Jens Axboe
2024-07-27 16:31 ` Lorenzo Stoakes
2024-07-27 16:36 ` Jens Axboe
2024-07-27 16:41 ` Lorenzo Stoakes
2024-07-27 16:52 ` Jens Axboe
2024-07-27 16:56 ` Lorenzo Stoakes
2024-07-28 11:32 ` David Laight
2024-07-27 4:13 ` Linus Torvalds
2024-07-27 4:14 ` Linus Torvalds
2024-07-27 8:08 ` David Laight
2024-07-27 18:58 ` Lorenzo Stoakes
2024-07-27 19:21 ` Linus Torvalds
2024-07-28 11:17 ` David Laight
2024-07-28 13:07 ` Lorenzo Stoakes
2024-07-27 17:33 ` Matthew Wilcox
2024-07-27 18:16 ` Linus Torvalds
2024-07-27 8:07 ` Lorenzo Stoakes
2024-07-27 16:26 ` Linus Torvalds
2024-07-27 18:44 ` Lorenzo Stoakes
2024-07-30 4:10 ` Linus Torvalds
2024-07-30 10:36 ` Arnd Bergmann
2024-07-28 17:57 ` Geert Uytterhoeven
2024-07-28 18:43 ` Lorenzo Stoakes
2024-07-26 21:32 ` David Laight
2024-07-26 21:38 ` Linus Torvalds
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