linux-kernel - Re: [PATCH][next] watchdog: cros-ec: Avoid -Wflex-array-member-not-at-end warning

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Message-ID: <Z-TvvUsB0eK2p8YJ@google.com>
Date: Thu, 27 Mar 2025 06:27:09 +0000
From: Tzung-Bi Shih <tzungbi@...nel.org>
To: "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc: Lukasz Majczak <lma@...omium.org>,
	Wim Van Sebroeck <wim@...ux-watchdog.org>,
	Guenter Roeck <linux@...ck-us.net>,
	Benson Leung <bleung@...omium.org>, chrome-platform@...ts.linux.dev,
	linux-watchdog@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: Re: [PATCH][next] watchdog: cros-ec: Avoid
 -Wflex-array-member-not-at-end warning

On Wed, Mar 26, 2025 at 04:35:13PM -0600, Gustavo A. R. Silva wrote:
> -Wflex-array-member-not-at-end was introduced in GCC-14, and we are
> getting ready to enable it, globally.
> 
> Use the `DEFINE_RAW_FLEX()` helper for an on-stack definition of
> a flexible structure where the size of the flexible-array member
> is known at compile-time, and refactor the rest of the code,
> accordingly.
> 
> So, with these changes, fix the following warning:
> 
> rivers/watchdog/cros_ec_wdt.c:29:40: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
 ^
 d truncated.

> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>

With minor comments,
Reviewed-by: Tzung-Bi Shih <tzungbi@...nel.org>

> +	DEFINE_RAW_FLEX(struct cros_ec_command, buf, data,
> +			sizeof(union cros_ec_wdt_data));

s/buf/msg/g makes much sense.

> +	((union cros_ec_wdt_data *)buf->data)->req = arg->req;

Or,
*(struct ec_params_hang_detect *)buf->data = arg->req;

> -	arg->resp = buf.data.resp;
> +	arg->resp = ((union cros_ec_wdt_data *)buf->data)->resp;

Or,
arg->resp = *(struct ec_response_hang_detect *)buf->data;