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Subject: Re: [PATCH 01/13] tools: disable -Wno-type-limits
To:     Yury Norov <yury.norov@gmail.com>, linux-kernel@vger.kernel.org
Cc:     linux-m68k@lists.linux-m68k.org, linux-arch@vger.kernel.org,
        linux-sh@vger.kernel.org, Alexey Klimov <aklimov@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Arnd Bergmann <arnd@arndb.de>, David Sterba <dsterba@suse.com>,
        Dennis Zhou <dennis@kernel.org>,
        Geert Uytterhoeven <geert@linux-m68k.org>,
        Jianpeng Ma <jianpeng.ma@intel.com>,
        Joe Perches <joe@perches.com>,
        John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Rich Felker <dalias@libc.org>,
        Stefano Brivio <sbrivio@redhat.com>,
        Wei Yang <richard.weiyang@linux.alibaba.com>,
        Wolfram Sang <wsa+renesas@sang-engineering.com>,
        Yoshinori Sato <ysato@users.sourceforge.jp>
References: <20210316015424.1999082-1-yury.norov@gmail.com>
 <20210316015424.1999082-2-yury.norov@gmail.com>
From:   Rasmus Villemoes <linux@rasmusvillemoes.dk>
Message-ID: <2ec71f83-f903-2775-bf04-7f0a83c9f4cb@rasmusvillemoes.dk>
Date:   Tue, 16 Mar 2021 09:17:24 +0100
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On 16/03/2021 02.54, Yury Norov wrote:
> GENMASK(h, l) may be passed with unsigned types. In such case, type-limits
> warning is generated for example in case of GENMASK(h, 0).
> 
> Signed-off-by: Yury Norov <yury.norov@gmail.com>
> ---
>  tools/scripts/Makefile.include | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/tools/scripts/Makefile.include b/tools/scripts/Makefile.include
> index 84dbf61a7eca..15e99905cb7d 100644
> --- a/tools/scripts/Makefile.include
> +++ b/tools/scripts/Makefile.include
> @@ -38,6 +38,7 @@ EXTRA_WARNINGS += -Wswitch-enum
>  EXTRA_WARNINGS += -Wundef
>  EXTRA_WARNINGS += -Wwrite-strings
>  EXTRA_WARNINGS += -Wformat
> +EXTRA_WARNINGS += -Wno-type-limits
>

I don't like that kind of collateral damage. I seem to recall another
instance where a macro was instead rewritten to avoid triggering the
type-limits warning (with a comment explaining the uglyness). Something like

foo > bar      is the same as
!(foo <= bar)  which is the same as
!(foo == bar || foo < bar)

Dunno if that would work here, but if it did, it would have the bonus
that when somebody builds the kernel proper with Wtype-limits enabled
(maybe W=1 or W=2) there would be no false positives from GENMASK to
wade through.

Alternatively, we really should consider making use of _Pragma to
locally disable/re-enable certain warnings.

Rasmus