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

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Message-ID: <CACRpkdYk25q9P5sErnfHcH49BT43vCCDihsZNEsf-6Gvpq+Pww@mail.gmail.com>
Date:   Thu, 17 Nov 2016 10:08:28 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Maxime Ripard <maxime.ripard@...e-electrons.com>
Cc:     Arnd Bergmann <arnd@...db.de>, 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 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.

Yours,
Linus Walleij