linux-kernel - Re: [PATCH 1/4 RESEND] mfd: arizona: fix undefined behavior

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Date:   Wed, 12 Jun 2019 09:31:38 +0100
From:   Lee Jones <lee.jones@...aro.org>
To:     Charles Keepax <ckeepax@...nsource.cirrus.com>
Cc:     arnd@...db.de, natechancellor@...il.com, ottosabart@...erm.com,
        linux-kernel@...r.kernel.org, patches@...nsource.cirrus.com
Subject: Re: [PATCH 1/4 RESEND] mfd: arizona: fix undefined behavior

On Mon, 20 May 2019, Charles Keepax wrote:

> From: Arnd Bergmann <arnd@...db.de>
> 
> When the driver is used with a subdevice that is disabled in the
> kernel configuration, clang gets a little confused about the
> control flow and fails to notice that n_subdevs is only
> uninitialized when subdevs is NULL, and we check for that,
> leading to a false-positive warning:
> 
> drivers/mfd/arizona-core.c:1423:19: error: variable 'n_subdevs' is uninitialized when used here
>       [-Werror,-Wuninitialized]
>                               subdevs, n_subdevs, NULL, 0, NULL);
>                                        ^~~~~~~~~
> drivers/mfd/arizona-core.c:999:15: note: initialize the variable 'n_subdevs' to silence this warning
>         int n_subdevs, ret, i;
>                      ^
>                       = 0
> 
> Ideally, we would rearrange the code to avoid all those early
> initializations and have an explicit exit in each disabled case,
> but it's much easier to chicken out and add one more initialization
> here to shut up the warning.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> Reviewed-by: Nathan Chancellor <natechancellor@...il.com>
> Signed-off-by: Charles Keepax <ckeepax@...nsource.cirrus.com>
> ---
>  drivers/mfd/arizona-core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Applied, thanks.

-- 
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
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