linux-kernel - Re: [PATCH] marvell/mwifiex: replace one-element array with flexible-array member.

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Message-ID: <CA+ASDXPCcgfXQNGRQThKHSRcxZ7i6=1GM0+sZL+ZAid8e=+sRQ@mail.gmail.com>
Date:   Tue, 19 Jan 2021 11:11:27 -0800
From:   Brian Norris <briannorris@...omium.org>
To:     Jiapeng Zhong <abaci-bugfix@...ux.alibaba.com>
Cc:     amit karwar <amitkarwar@...il.com>,
        Ganapathi Bhat <ganapathi.bhat@....com>,
        Xinming Hu <huxinming820@...il.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        linux-wireless <linux-wireless@...r.kernel.org>,
        Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] marvell/mwifiex: replace one-element array with
 flexible-array member.

Hi,

On Fri, Jan 15, 2021 at 1:39 AM Jiapeng Zhong
<abaci-bugfix@...ux.alibaba.com> wrote:
>
> Fix the follow coccicheck warnings:
>
> ./drivers/net/wireless/marvell/mwifiex/fw.h: WARNING use flexible-array
> member instead(https://www.kernel.org/doc/html/latest/process/
> deprecated.html#zero-length-and-one-element-arrays)
>
> Reported-by: Abaci Robot <abaci@...ux.alibaba.com>
> Signed-off-by: Jiapeng Zhong <abaci-bugfix@...ux.alibaba.com>

Past experience unfortunately requires me to ask: did you test your
changes? I understand that's a mostly legit warning, and a good
deprecation notice, but that doesn't mean this is the right fix. One
probably should instead audit the usage sites to see if they *are*
already making proper sizeof (or other) comparisons, and if not, fix
those first. And if any sites *are* doing correct sizeof computations
using the existing struct layouts, then you are probably breaking
them.

Or if you have audited the usage of these structs, it's nice to make a
small explanation of why this is correct, so I (and other readers)
don't have to ask these questions :)

Regards,
Brian