linux-kernel - Re: [PATCH v2] linux/bits.h: GENMASK_INPUT_CHECK: reduce W=2 noise by 31% treewide

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Message-ID: <CAHk-=whvGWbpsTa538CvQ9e=VF+m8WPQmES2y6-=0=-64uGkgg@mail.gmail.com>
Date:   Tue, 8 Mar 2022 10:13:02 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Vincent Mailhol <mailhol.vincent@...adoo.fr>
Cc:     Rikard Falkeborn <rikard.falkeborn@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Kees Cook <keescook@...omium.org>,
        Alexander Lobakin <alexandr.lobakin@...el.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Emil Velikov <emil.l.velikov@...il.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        kernel test robot <lkp@...el.com>,
        Syed Nayyar Waris <syednwaris@...il.com>,
        William Breathitt Gray <vilhelm.gray@...il.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>
Subject: Re: [PATCH v2] linux/bits.h: GENMASK_INPUT_CHECK: reduce W=2 noise by
 31% treewide

On Tue, Mar 8, 2022 at 6:12 AM Vincent Mailhol
<mailhol.vincent@...adoo.fr> wrote:
>
> This patch silences a -Wtypes-limits warning in GENMASK_INPUT_CHECK()
> which is accountable for 31% of all warnings when compiling with W=2.

Please, just make the patch be "remote -Wtypes-limits".

Instead of making an already complicated check more complicated, and
making it more fragile.

I don't see why that int cast on h would be valid, for example. Why
just h? And should you not then check that the cast doesn't actually
change the value?

But the basic issue is that the compiler warns about bad things, and
the problem isn't the code, but the compiler.

                      Linus