Re: [greybus-dev] [PATCH] Kbuild: remove -std=gnu89 from compiler arguments

From: Alex Elder <elder@linaro.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Arnd Bergmann <arnd@kernel.org>,
	Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
	Arnd Bergmann <arnd@arndb.de>,
	Masahiro Yamada <masahiroy@kernel.org>,
	llvm@lists.linux.dev, Jonathan Corbet <corbet@lwn.net>,
	Federico Vaga <federico.vaga@vaga.pv.it>,
	Alex Shi <alexs@kernel.org>, Hu Haowen <src.res@email.cn>,
	Michal Marek <michal.lkml@markovi.net>,
	Nick Desaulniers <ndesaulniers@google.com>,
	"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-doc-tw-discuss@lists.sourceforge.net,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	intel-gfx <intel-gfx@lists.freedesktop.org>,
	dri-devel <dri-devel@lists.freedesktop.org>,
	greybus-dev@lists.linaro.org, linux-staging@lists.linux.dev,
	linux-btrfs <linux-btrfs@vger.kernel.org>
Subject: Re: [greybus-dev] [PATCH] Kbuild: remove -std=gnu89 from compiler arguments
Date: Sun, 27 Feb 2022 17:57:52 -0600	[thread overview]
Message-ID: <72ff1b04-4f37-9851-a6e6-aded72b46c83@linaro.org> (raw)
In-Reply-To: <CAHk-=wg_r01OASRuSFfbEk_YHjve2BsBbkDYiEiKTaX2jm=53g@mail.gmail.com>

On 2/27/22 5:11 PM, Linus Torvalds wrote:
> On Sun, Feb 27, 2022 at 3:04 PM Alex Elder <elder@linaro.org> wrote:
>>
>> Glancing at the Greybus code, I don't believe there's any
>> reason it needs to shift a negative value.  Such warnings
>> could be fixed by making certain variables unsigned, for
>> example.
> 
> As mentioned in the original thread, making things unsigned actually
> is likely to introduce bugs and make things worse.

Understood.  What I meant is that the shifts were producing
single-bit masks from plain int values that range from 0 to 10
or something (in a for loop).  Looking again though, that it's
not so simple.  Regardless, your point about the warning is
good and I won't plan to "fix" this.

Thanks.

					-Alex
> 
> The warning is simply bogus, and the fact that it was enabled by
> -Wextra in gcc for std=gnu99 and up was a mistake that looks likely to
> be fixed in gcc.
> 
> So don't try to "fix" the code to make any possible warnings go away.
> You may just make things worse.
> 
> (That is often true in general for the more esoteric warnings, but in
> this case it's just painfully more obvious).
> 
>                Linus

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