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From: Lee Jones <lee.jones@linaro.org>
To: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Cc: Tony Lindgren <tony@atomide.com>,
	linux-omap@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mfd: omap-usb-tll: Replace zero-length array with flexible-array member
Date: Mon, 24 Feb 2020 10:48:45 +0000	[thread overview]
Message-ID: <20200224104845.GP3494@dell> (raw)
In-Reply-To: <20200212235642.GA19206@embeddedor.com>

On Wed, 12 Feb 2020, 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
> 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]
> 
> 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>
> ---
>  drivers/mfd/omap-usb-tll.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Applied, thanks.

-- 
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog

      reply	other threads:[~2020-02-24 10:48 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-12 23:56 Gustavo A. R. Silva
2020-02-24 10:48 ` Lee Jones [this message]

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