netdev - RE: [EXT] [PATCH][next] wireless: marvell: Replace zero-length array with flexible-array member

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Message-ID: <DB7PR04MB52428EFEFA7CD058331CFF848FFF0@DB7PR04MB5242.eurprd04.prod.outlook.com>
Date:   Tue, 10 Mar 2020 04:28:14 +0000
From:   Ganapathi Bhat <ganapathi.bhat@....com>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        "David S. Miller" <davem@...emloft.net>,
        Amitkumar Karwar <amitkarwar@...il.com>,
        Xinming Hu <huxinming820@...il.com>,
        Lennert Buytenhek <buytenh@...tstofly.org>
CC:     "linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [EXT] [PATCH][next] wireless: marvell: Replace zero-length array
 with flexible-array member

Hi Gustavo,

> 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 inadvertently
> introduced[3] to the codebase from now on.
> 
> Also, notice that, dynamic memory allocations won't be affected by this
> change:
> 
> "Flexible array members have incomplete type, and so the sizeof operator
> may not be applied. As a quirk of the original implementation of zero-length
> arrays, sizeof evaluates to zero."[1]

Thanks for this path.

Acked-by: Ganapathi Bhat <ganapathi.bhat@....com>