linux-kernel - Re: [PATCH] Kbuild: Move -Wmaybe-uninitialized to W=1

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Message-ID: <20160728175647.GB316@x4>
Date:	Thu, 28 Jul 2016 19:56:47 +0200
From:	Markus Trippelsdorf <markus@...ppelsdorf.de>
To:	Borislav Petkov <bp@...en8.de>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Sam Ravnborg <sam@...nborg.org>,
	lkml <linux-kernel@...r.kernel.org>, Michael Matz <matz@...e.de>,
	linux-kbuild@...r.kernel.org, x86-ml <x86@...nel.org>
Subject: Re: [PATCH] Kbuild: Move -Wmaybe-uninitialized to W=1

On 2016.07.28 at 10:46 +0200, Borislav Petkov wrote:
> On Thu, Jul 28, 2016 at 10:29:15AM +0200, Ingo Molnar wrote:
> > BUT, isn't this the natural state of things, that the 'final' warnings
> > that don't get fixed are the obnoxious, false positive ones - because
> > anyone who looks at them will say "oh crap, idiotic compiler!"?
> 
> Hmm, so my experience is like Linus' - that -Wmaybe thing generates too
> much noise and a lot of false positives. The thing is, as Micha (on CC)
> explained it to me, that warning simply says that GCC sometimes *cannot*
> know whether the variable will be used uninitialized or not and eagerly
> issues the warning message, just in case.

Another issue is that the number of warnings you get depend on the
optimization level. So -Os may be different from -O2 and once you use
-O3 (I know it is not officially supported) you will drown in false
positives...

-- 
Markus