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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Sat, 26 Feb 2022 15:03:09 -0800
Message-ID: <CAHk-=wjAG2TZj5rEhiHyuD7KoffTLhikXy7OSj2f8QXAf7M=2A@mail.gmail.com>
Subject: Re: [RFC PATCH 03/13] usb: remove the usage of the list iterator
 after the loop
To:     Arnd Bergmann <arnd@arndb.de>
Cc:     Segher Boessenkool <segher@kernel.crashing.org>,
        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>
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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, 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.
But we'll have to do it manually for the existing situation.

          Linus