linux-kernel - Re: [RFC PATCH 03/13] usb: remove the usage of the list iterator after the loop

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Date:   Sat, 26 Feb 2022 23:14:15 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Segher Boessenkool <segher@...nel.crashing.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Jakob <jakobkoschel@...il.com>, Arnd Bergmann <arnd@...db.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Kees Cook <keescook@...omium.org>,
        Mike Rapoport <rppt@...nel.org>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Brian Johannesmeyer <bjohannesmeyer@...il.com>,
        Cristiano Giuffrida <c.giuffrida@...nl>,
        "Bos, H.J." <h.j.bos@...nl>
Subject: Re: [RFC PATCH 03/13] usb: remove the usage of the list iterator
 after the loop

On Sat, Feb 26, 2022 at 1:42 PM Segher Boessenkool
<segher@...nel.crashing.org> wrote:
> On Wed, Feb 23, 2022 at 11:23:39AM -0800, Linus Torvalds wrote:

> > That said, we seem to only have two cases of it in the kernel, at
> > least by a x86-64 allmodconfig build. So we could examine the types
> > there, or we could just add '-Wno-shift-negative-value".
>
> Yes.
>
> The only reason the warning exists is because it is undefined behaviour
> (not implementation-defined or anything).  The reason it is that in the
> standard is that it is hard to implement and even describe for machines
> that are not two's complement.  However relevant that is today :-)

Could gcc follow the clang behavior then and skip the warning and
sanitizer for this case when -fno-strict-overflow or -fwrapv are used?

         Arnd