From: Segher Boessenkool <segher@kernel.crashing.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Arnd Bergmann <arnd@arndb.de>, Jakob <jakobkoschel@gmail.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-arch <linux-arch@vger.kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Thomas Gleixner <tglx@linutronix.de>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
Kees Cook <keescook@chromium.org>,
Mike Rapoport <rppt@kernel.org>,
"Gustavo A. R. Silva" <gustavo@embeddedor.com>,
Brian Johannesmeyer <bjohannesmeyer@gmail.com>,
Cristiano Giuffrida <c.giuffrida@vu.nl>,
"Bos, H.J." <h.j.bos@vu.nl>
Subject: Re: [RFC PATCH 03/13] usb: remove the usage of the list iterator after the loop
Date: Sat, 26 Feb 2022 19:19:13 -0600 [thread overview]
Message-ID: <20220227011913.GX614@gate.crashing.org> (raw)
In-Reply-To: <CAHk-=wjAG2TZj5rEhiHyuD7KoffTLhikXy7OSj2f8QXAf7M=2A@mail.gmail.com>
On Sat, Feb 26, 2022 at 03:03:09PM -0800, Linus Torvalds wrote:
> On Sat, Feb 26, 2022 at 2:14 PM Arnd Bergmann <arnd@arndb.de> wrote:
> >
> > Could gcc follow the clang behavior then and skip the warning and
> > sanitizer for this case when -fno-strict-overflow or -fwrapv are used?
>
> Well, for the kernel, that horse has already left the barn, and we'd
> have to use -Wno-shift-negative-value anyway.
>
> But yes, from a sanity standpoint, it would be good to shut that
> warning up automatically if compiling for a 2's complement machine (ie
> "all of them") with -fwrapv.
>
> Considering that gcc doesn't support any non-2's-complement machines
> anyway afaik,
* 'Whether signed integer types are represented using sign and
magnitude, two's complement, or one's complement, and whether the
extraordinary value is a trap representation or an ordinary value
(C99 and C11 6.2.6.2).'
GCC supports only two's complement integer types, and all bit
patterns are ordinary values.
> and that the C standards people are also fixing the
> standard, and gcc has never done anything odd in this area in the
> first place, I think the warning is probably best removed entirely.
Well, not removed, it correctly identifies (formally) undefined
behaviour after all; but I agree it should not be in -Wextra.
-Wall should include the warnings that have a very good balance for
usefulness, number of false postives, seriousness of problems found.
-Wextra is exactly the same conditions, just a slightly lower bar.
-Wall should be useful for everyone. -Wall -W should be good for most
people.
> But we'll have to do it manually for the existing situation.
Yes, sorry about that :-/
Segher
next prev parent reply other threads:[~2022-02-27 1:24 UTC|newest]
Thread overview: 70+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-17 18:48 [RFC PATCH 00/13] Proposal for speculative safe list iterator Jakob Koschel
2022-02-17 18:48 ` [RFC PATCH 01/13] list: introduce speculative safe list_for_each_entry() Jakob Koschel
2022-02-17 19:29 ` Greg Kroah-Hartman
2022-02-18 16:29 ` Jann Horn
2022-02-18 16:29 ` Jann Horn
2022-02-23 14:32 ` Jakob
2022-02-19 19:44 ` Jann Horn
2022-02-17 18:48 ` [RFC PATCH 02/13] scripts: coccinelle: adapt to find list_for_each_entry nospec issues Jakob Koschel
2022-02-17 18:48 ` [RFC PATCH 03/13] usb: remove the usage of the list iterator after the loop Jakob Koschel
2022-02-17 19:28 ` Linus Torvalds
2022-02-23 14:13 ` Jakob
2022-02-23 14:16 ` Jakob
2022-02-24 10:33 ` Greg Kroah-Hartman
2022-02-24 17:56 ` Linus Torvalds
[not found] ` <6d191223d93249a98511177d4af08420@pexch012b.vu.local>
2022-02-24 10:46 ` Cristiano Giuffrida
2022-02-24 11:26 ` Greg Kroah-Hartman
2022-02-23 18:47 ` Linus Torvalds
2022-02-23 19:23 ` Linus Torvalds
2022-02-23 19:43 ` Linus Torvalds
2022-02-23 20:24 ` Arnd Bergmann
2022-02-23 20:43 ` Linus Torvalds
2022-02-23 20:48 ` Arnd Bergmann
2022-02-23 21:53 ` Linus Torvalds
2022-02-24 16:04 ` Nathan Chancellor
2022-02-23 20:54 ` Linus Torvalds
2022-02-23 22:21 ` David Laight
2022-02-25 21:36 ` Uecker, Martin
2022-02-25 22:02 ` Linus Torvalds
2022-02-26 1:21 ` Martin Uecker
2022-02-27 18:12 ` Miguel Ojeda
2022-02-28 7:08 ` Martin Uecker
2022-02-28 13:49 ` Miguel Ojeda
2022-03-01 20:26 ` Linus Torvalds
2022-03-02 7:27 ` Martin Uecker
2022-02-26 12:42 ` Segher Boessenkool
2022-02-26 22:14 ` Arnd Bergmann
2022-02-26 23:03 ` Linus Torvalds
2022-02-27 1:19 ` Segher Boessenkool [this message]
2022-02-27 1:09 ` Segher Boessenkool
2022-02-27 7:10 ` David Laight
2022-02-27 11:32 ` Segher Boessenkool
2022-02-27 18:09 ` Miguel Ojeda
2022-02-27 20:17 ` Segher Boessenkool
2022-02-27 21:04 ` Linus Torvalds
2022-02-28 6:15 ` David Laight
2022-02-27 22:43 ` Miguel Ojeda
2022-02-27 21:28 ` Arnd Bergmann
2022-02-27 22:43 ` Segher Boessenkool
2022-02-17 18:48 ` [RFC PATCH 04/13] vfio/mdev: " Jakob Koschel
2022-02-18 15:12 ` Jason Gunthorpe
2022-02-23 14:18 ` Jakob
2022-02-23 19:06 ` Linus Torvalds
2022-02-23 19:12 ` Jason Gunthorpe
2022-02-23 19:31 ` Linus Torvalds
2022-02-23 20:15 ` Jakob
2022-02-23 20:22 ` Linus Torvalds
2022-02-23 22:08 ` Jakob
2022-02-23 20:19 ` Rasmus Villemoes
2022-02-23 20:34 ` Linus Torvalds
2022-02-17 18:48 ` [RFC PATCH 05/13] drivers/perf: " Jakob Koschel
2022-02-17 18:48 ` [RFC PATCH 06/13] ARM: mmp: " Jakob Koschel
2022-02-17 18:48 ` [RFC PATCH 07/13] udp_tunnel: " Jakob Koschel
2022-02-23 20:00 ` Christophe JAILLET
2022-02-24 6:20 ` Dan Carpenter
2022-02-17 18:48 ` [RFC PATCH 08/13] net: dsa: future proof usage of " Jakob Koschel
2022-02-17 18:48 ` [RFC PATCH 09/13] drbd: " Jakob Koschel
2022-02-17 18:48 ` [RFC PATCH 10/13] powerpc/spufs: " Jakob Koschel
2022-02-17 18:48 ` [RFC PATCH 11/13] ath6kl: remove use " Jakob Koschel
2022-02-17 18:48 ` [RFC PATCH 12/13] staging: greybus: audio: Remove usage " Jakob Koschel
2022-02-17 18:48 ` [RFC PATCH 13/13] scsi: mpt3sas: comment about invalid usage of the list iterator Jakob Koschel
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