linux-kernel - Re: [PATCH] pinctrl: sunxi: fix theoretical uninitialized variable access

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Message-ID: <6865471.komOtxkTtZ@wuerfel>
Date:   Thu, 17 Nov 2016 10:24:28 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Linus Walleij <linus.walleij@...aro.org>
Cc:     Maxime Ripard <maxime.ripard@...e-electrons.com>,
        Chen-Yu Tsai <wens@...e.org>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] pinctrl: sunxi: fix theoretical uninitialized variable access

On Thursday, November 17, 2016 10:08:28 AM CET Linus Walleij wrote:
> On Wed, Nov 16, 2016 at 9:33 PM, Maxime Ripard
> <maxime.ripard@...e-electrons.com> wrote:
> 
> > On Wed, Nov 16, 2016 at 03:18:18PM +0100, Arnd Bergmann wrote:
> >> gcc warns about a  way that it could use an uninitialized variable:
> >>
> >> drivers/pinctrl/sunxi/pinctrl-sunxi.c: In function 'sunxi_pinctrl_init':
> >> drivers/pinctrl/sunxi/pinctrl-sunxi.c:1191:8: error: 'best_div' may be used uninitialized in this function [-Werror=maybe-uninitialized]
> >>
> >> This cannot really happen except if 'freq' is UINT_MAX and 'clock' is
> >> zero, and both of these are forbidden. To shut up the warning anyway,
> >> this changes the logic to initialize the return code to the first
> >> divider value before looking at the others.
> >>
> >> Fixes: 7c926492d38a ("pinctrl: sunxi: Add support for interrupt debouncing")
> >> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> >
> > Thanks for that patch.
> >
> > Just out of curiosity, which gcc gives those warnings? I have 6.2 and
> > it didn't output anything..
> 
> Context: Arnd re-enabled -Werror=maybe-uninitialized
> in the kernel build and this kind of stuff started to appear so
> it needs to be fixed up.

Right, it was disabled from linux-4.8-rc1 to linux-4.9-rc4 and is now back
in the default builds when using gcc-4.9 or higher. You should get the
warning if you test with linux-next or -rc4.

	Arnd