From: Baolin Wang <baolin.wang7@gmail.com>
To: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Cc: Vinod Koul <vkoul@kernel.org>,
Dan Williams <dan.j.williams@intel.com>,
Orson Zhai <orsonzhai@gmail.com>,
Chunyan Zhang <zhang.lyra@gmail.com>,
dmaengine@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] dmaengine: sprd: Replace zero-length array with flexible-array member
Date: Mon, 17 Feb 2020 09:55:17 +0800 [thread overview]
Message-ID: <CADBw62qTu2dGL+dGgC6WzsSusVfDKxUdd57f_1jn_A-Vf1-rrQ@mail.gmail.com> (raw)
In-Reply-To: <20200214171536.GA24077@embeddedor>
Hi,
On Sat, Feb 15, 2020 at 2:04 AM Gustavo A. R. Silva
<gustavo@embeddedor.com> 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")
Looks good to me. Thanks.
Reviewed-by: Baolin Wang <baolin.wang7@gmail.com>
> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
> ---
> drivers/dma/sprd-dma.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/dma/sprd-dma.c b/drivers/dma/sprd-dma.c
> index 9a31a315dbef..954eff32cc05 100644
> --- a/drivers/dma/sprd-dma.c
> +++ b/drivers/dma/sprd-dma.c
> @@ -212,7 +212,7 @@ struct sprd_dma_dev {
> struct clk *ashb_clk;
> int irq;
> u32 total_chns;
> - struct sprd_dma_chn channels[0];
> + struct sprd_dma_chn channels[];
> };
>
> static void sprd_dma_free_desc(struct virt_dma_desc *vd);
> --
> 2.25.0
>
next prev parent reply other threads:[~2020-02-17 1:55 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-14 17:15 [PATCH] dmaengine: sprd: Replace zero-length array with flexible-array member Gustavo A. R. Silva
2020-02-17 1:55 ` Baolin Wang [this message]
2020-02-19 12:20 ` Vinod Koul
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CADBw62qTu2dGL+dGgC6WzsSusVfDKxUdd57f_1jn_A-Vf1-rrQ@mail.gmail.com \
--to=baolin.wang7@gmail.com \
--cc=dan.j.williams@intel.com \
--cc=dmaengine@vger.kernel.org \
--cc=gustavo@embeddedor.com \
--cc=linux-kernel@vger.kernel.org \
--cc=orsonzhai@gmail.com \
--cc=vkoul@kernel.org \
--cc=zhang.lyra@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).