linux-kernel - Re: [PATCH] linux/find: ignore -Wtype-limits to reduce W=2 warnings by 34% tree-wide

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Date:   Wed, 27 Apr 2022 11:32:53 +0900
From:   Vincent MAILHOL <mailhol.vincent@...adoo.fr>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Yury Norov <yury.norov@...il.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] linux/find: ignore -Wtype-limits to reduce W=2 warnings
 by 34% tree-wide

On Wed. 27 Apr 2022 at 03:56, Arnd Bergmann <arnd@...db.de> wrote:
> On Tue, Apr 26, 2022 at 6:16 PM Vincent Mailhol
> <mailhol.vincent@...adoo.fr> wrote:
>
> > +__diag_push();
> > +__diag_ignore(GCC, 8, "-Wtype-limits",
> > +             "GENMASK(size - 1, 0) yields 'comparison of unsigned expression in < 0 is always false' which is OK");
> > +
>
> Are you sure gcc-8 is the correct version to check for?
> If older versions had this
> already, you may have to add the magic bits in the compiler-gcc.h header.

Right, I used GCC-8 because this is what is available off the
shelf in compiler-gcc.h (and I CC'd you on purpose because I
though you might have relevant comments).

-Wtype-limits was introduced in GCC 4.3. Need to check if this
specific check existed back then, but I strongly expect the older
version to also trigger the warning.  It might take me a bit of
time to set up an environment with an old GCC (nothing hard, just
need to get access to the good machine). So do not worry if I
stay silent on this subject for the next couple of days.

Yours sincerely,
Vincent Mailhol