linux-kernel - Re: [PATCH][next] wifi: iwlegacy: Avoid multiple -Wflex-array-member-not-at-end warnings

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Message-ID: <172431607671.2217900.17688660521871057596.kvalo@kernel.org>
Date: Thu, 22 Aug 2024 08:41:18 +0000 (UTC)
From: Kalle Valo <kvalo@...nel.org>
To: "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc: Stanislaw Gruszka <stf_xl@...pl>, linux-wireless@...r.kernel.org,
 linux-kernel@...r.kernel.org, "Gustavo A. R. Silva" <gustavoars@...nel.org>,
 linux-hardening@...r.kernel.org
Subject: Re: [PATCH][next] wifi: iwlegacy: Avoid multiple
 -Wflex-array-member-not-at-end warnings

"Gustavo A. R. Silva" <gustavoars@...nel.org> wrote:

> -Wflex-array-member-not-at-end was introduced in GCC-14, and we are
> getting ready to enable it, globally.
> 
> So, in order to avoid ending up with a flexible-array member in the
> middle of multiple other structs, we use the `__struct_group()`
> helper to create new tagged structures with the suffix `_hdr`.
> These structures group together all the members of the original
> flexible structures except the flexible arrays.
> 
> As a result, the arrays are effectively separated from the rest of the
> members without modifying the memory layout of the flexible structures.
> We then change the type of the middle struct members currently causing
> trouble from the original flex struct to the newly created structs with
> suffix `_hdr`.
> 
> We also want to ensure that when new members need to be added to the
> flexible structures, they are always included within the newly created
> tagged structs. For this, we use `static_assert()`. This ensures that the
> memory layout for both the flexible structure and the new tagged struct
> is the same after any changes.
> 
> This approach avoids having to implement the `_hdr` structures as
> completely separate structures, thus preventing having to maintain
> two independent but basically identical structures, closing the door
> to potential bugs in the future.
> 
> We also use `container_of()` whenever we need to retrieve a pointer to
> the flexible structure, through which we can access the flexible-array
> member, if necessary.
> 
> Also, remove a couple of unused zero-length arrays and flexible-array
> members.
> 
> So, with these changes, fix the following warnings:
> 
> drivers/net/wireless/intel/iwlegacy/commands.h:1196:38: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
> drivers/net/wireless/intel/iwlegacy/commands.h:1197:36: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
> drivers/net/wireless/intel/iwlegacy/commands.h:2505:30: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
> drivers/net/wireless/intel/iwlegacy/commands.h:2549:26: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
> drivers/net/wireless/intel/iwlegacy/commands.h:2654:31: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
> drivers/net/wireless/intel/iwlegacy/commands.h:2665:30: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
> drivers/net/wireless/intel/iwlegacy/commands.h:2673:26: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
> drivers/net/wireless/intel/iwlegacy/commands.h:3349:30: 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>

Patch applied to wireless-next.git, thanks.

a7e8997ae18c wifi: iwlegacy: Avoid multiple -Wflex-array-member-not-at-end warnings

-- 
https://patchwork.kernel.org/project/linux-wireless/patch/Zr2gxERA3RL3EwRe@elsanto/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches