linux-kernel - Re: [PATCH] ASoC: wm0010: Replace zero-length array with flexible-array member

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Message-ID: <20200212092030.GE4098@ediswmail.ad.cirrus.com>
Date:   Wed, 12 Feb 2020 09:20:30 +0000
From:   Charles Keepax <ckeepax@...nsource.cirrus.com>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>
CC:     Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>, <patches@...nsource.cirrus.com>,
        <alsa-devel@...a-project.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ASoC: wm0010: Replace zero-length array with
 flexible-array member

On Tue, Feb 11, 2020 at 02:05:49PM -0600, Gustavo A. R. Silva wrote:
> The current codebase makes use of the zero-length array language
> extension to the C90 standard, but the preferred mechanism to declare
> variable-length types such as these ones is a flexible array member[1][2],
> introduced in C99:
> 
> struct foo {
>         int stuff;
>         struct boo array[];
> };
> 
> By making use of the mechanism above, we will get a compiler warning
> in case the flexible array does not occur last in the structure, which
> will help us prevent some kind of undefined behavior bugs from being
> inadvertenly introduced[3] to the codebase from now on.
> 
> This issue was found with the help of Coccinelle.
> 
> [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
> [2] https://github.com/KSPP/linux/issues/21
> [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")
> 
> Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
> ---

Acked-by: Charles Keepax <ckeepax@...nsource.cirrus.com>

Thanks,
Charles