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

From: Takashi Iwai <tiwai@suse.de>
To: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Cc: Clemens Ladisch <clemens@ladisch.de>,
	Jaroslav Kysela <perex@perex.cz>, Takashi Iwai <tiwai@suse.com>,
	alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] ALSA: usb-midi: Replace zero-length array with flexible-array member
Date: Wed, 12 Feb 2020 08:15:56 +0100	[thread overview]
Message-ID: <s5hftfg1djn.wl-tiwai@suse.de> (raw)
In-Reply-To: <20200211194224.GA9383@embeddedor>

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@embeddedor.com>

Applied, thanks.

Takashi