From: Daniel Lezcano <daniel.lezcano@linaro.org>
To: "Gustavo A. R. Silva" <gustavo@embeddedor.com>,
Andy Gross <agross@kernel.org>,
Bjorn Andersson <bjorn.andersson@linaro.org>,
Amit Kucheria <amit.kucheria@linaro.org>,
Zhang Rui <rui.zhang@intel.com>
Cc: linux-arm-msm@vger.kernel.org, linux-pm@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] thermal: qcom: tsens.h: Replace zero-length array with flexible-array member
Date: Thu, 19 Mar 2020 21:43:05 +0100 [thread overview]
Message-ID: <dc2d025f-0d26-b91c-975a-6c815a7682ef@linaro.org> (raw)
In-Reply-To: <20200319184838.GA25767@embeddedor.com>
On 19/03/2020 19:48, 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>
Applied, thanks
> ---
> drivers/thermal/qcom/tsens.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/thermal/qcom/tsens.h b/drivers/thermal/qcom/tsens.h
> index e24a865fbc34..92503712596a 100644
> --- a/drivers/thermal/qcom/tsens.h
> +++ b/drivers/thermal/qcom/tsens.h
> @@ -488,7 +488,7 @@ struct tsens_priv {
> struct dentry *debug_root;
> struct dentry *debug;
>
> - struct tsens_sensor sensor[0];
> + struct tsens_sensor sensor[];
> };
>
> char *qfprom_read(struct device *dev, const char *cname);
>
--
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prev parent reply other threads:[~2020-03-19 20:43 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-19 18:48 [PATCH] thermal: qcom: tsens.h: Replace zero-length array with flexible-array member Gustavo A. R. Silva
2020-03-19 19:56 ` Amit Kucheria
2020-03-19 20:43 ` Daniel Lezcano [this message]
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