linux-kernel - Re: [PATCH] ALSA: usb-midi: Replace zero-length array with flexible-array member

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Message-ID: <s5hftfg1djn.wl-tiwai@suse.de>
Date:   Wed, 12 Feb 2020 08:15:56 +0100
From:   Takashi Iwai <tiwai@...e.de>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Cc:     Clemens Ladisch <clemens@...isch.de>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>, alsa-devel@...a-project.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ALSA: usb-midi: Replace zero-length array with flexible-array member

On Tue, 11 Feb 2020 20:42:24 +0100,
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>

Applied, thanks.


Takashi