linux-kernel - Re: [PATCH][next] carl9170: Avoid -Wflex-array-member-not-at-end warning

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Message-ID: <20c2a143-3841-4839-b377-b90dfd8a031c@gmail.com>
Date: Thu, 20 Nov 2025 20:35:29 +0100
From: Christian Lamparter <chunkeey@...il.com>
To: "Gustavo A. R. Silva" <gustavoars@...nel.org>,
 Christian Lamparter <chunkeey@...glemail.com>
Cc: linux-wireless@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-hardening@...r.kernel.org
Subject: Re: [PATCH][next] carl9170: Avoid -Wflex-array-member-not-at-end
 warning

On 11/19/25 8:33 AM, 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.
> 
> Move the conflicting declaration (which happens to be in a union, so
> we're moving the entire union) to the end of the corresponding
> structure. Notice that `struct carl9170_rsp` is a flexible structure,
> this is a structure that contains a flexible-array member.
> 
> With these changes fix the following warning:
> 
> drivers/net/wireless/ath/carl9170/carl9170.h:382:9: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
> 
> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>

Sure, if this truly fixes the warning.

Acked-by: Christian Lamparter <chunkeey@...il.com>

> ---
>   drivers/net/wireless/ath/carl9170/carl9170.h | 12 +++++++-----
>   1 file changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/net/wireless/ath/carl9170/carl9170.h b/drivers/net/wireless/ath/carl9170/carl9170.h
> index ba29b4aebe9f..b13685e22a0d 100644
> --- a/drivers/net/wireless/ath/carl9170/carl9170.h
> +++ b/drivers/net/wireless/ath/carl9170/carl9170.h
> @@ -375,11 +375,6 @@ struct ar9170 {
>   	u8 *readbuf;
>   	spinlock_t cmd_lock;
>   	struct completion cmd_wait;
> -	union {
> -		__le32 cmd_buf[PAYLOAD_MAX + 1];
> -		struct carl9170_cmd cmd;
> -		struct carl9170_rsp rsp;
> -	};
>   
>   	/* statistics */
>   	unsigned int tx_dropped;
> @@ -463,6 +458,13 @@ struct ar9170 {
>   		unsigned int cache_idx;
>   	} rng;
>   #endif /* CONFIG_CARL9170_HWRNG */
> +
> +	/* Must be last as it ends in a flexible-array member. */
> +	union {
> +		__le32 cmd_buf[PAYLOAD_MAX + 1];
> +		struct carl9170_cmd cmd;
> +		struct carl9170_rsp rsp;
> +	};
>   };
>   
>   enum carl9170_ps_off_override_reasons {