linux-kernel - Re: [PATCH v3 1/1] RDMA/rxe: Avoid -Wflex-array-member-not-at-end warnings

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Message-ID: <d4f60741-b0af-4a51-a1dc-cded1f34f309@embeddedor.com>
Date: Wed, 24 Dec 2025 01:59:39 +0900
From: "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To: Greg Sword <gregsword0@...il.com>
Cc: Zhu Yanjun <yanjun.zhu@...ux.dev>, zyjzyj2000@...il.com, jgg@...pe.ca,
 leon@...nel.org, linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org,
 "Gustavo A. R. Silva" <gustavoars@...nel.org>
Subject: Re: [PATCH v3 1/1] RDMA/rxe: Avoid -Wflex-array-member-not-at-end
 warnings



On 12/24/25 01:38, Greg Sword wrote:
> On Tue, Dec 23, 2025 at 5:35 PM Gustavo A. R. Silva
> <gustavo@...eddedor.com> wrote:
>>
>>
>>
>> On 12/23/25 13:41, Zhu Yanjun wrote:
>>> From: "Gustavo A. R. Silva" <gustavoars@...nel.org>
>>>
>>> -Wflex-array-member-not-at-end was introduced in GCC-14, and we are
>>> getting ready to enable it, globally.
>>>
>>> Use the new TRAILING_OVERLAP() helper to fix the following warning:
>>>
>>> 21 drivers/infiniband/sw/rxe/rxe_verbs.h:271:33: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
>>>
>>> This helper creates a union between a flexible-array member (FAM) and a
>>> set of MEMBERS that would otherwise follow it.
>>>
>>> This overlays the trailing MEMBER struct ib_sge sge[RXE_MAX_SGE]; onto
>>> the FAM struct rxe_recv_wqe::dma.sge, while keeping the FAM and the
>>> start of MEMBER aligned.
>>>
>>> The static_assert() ensures this alignment remains, and it's
>>> intentionally placed inmediately after the related structure --no
>>> blank line in between.
>>>
>>> Lastly, move the conflicting declaration struct rxe_resp_info resp;
>>> to the end of the corresponding structure.
>>>
>>> Reviewed-by: Zhu Yanjun <yanjun.zhu@...ux.dev>
>>> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
>>
>> NACK.
> 
> Just a small reminder about community conventions: reviewers can NACK
> a patch, but authors generally should not NACK their own patches.

It's obvious that you don't understand what's going on here.

>> I didn't write this patch.

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
This line should've given you a clue.

-Gustavo

>>
>> Please, don't ever submit modified patches on my behalf.
>>
>>> ---
>>> V2->V3: Replace struct ib_sge with struct rxe_sge
>>
>> Patch granularity is a fundamental thing. Changes addressing different
>> issues should not be mixed together. Previously existing issues (if any)
>> must be addressed in separate patches.
>>
>> -Gustavo
>>
>>> ---
>>>    drivers/infiniband/sw/rxe/rxe_verbs.h | 18 +++++++++++-------
>>>    1 file changed, 11 insertions(+), 7 deletions(-)
>>>
>>> diff --git a/drivers/infiniband/sw/rxe/rxe_verbs.h b/drivers/infiniband/sw/rxe/rxe_verbs.h
>>> index fd48075810dd..3ffd7be8e7b1 100644
>>> --- a/drivers/infiniband/sw/rxe/rxe_verbs.h
>>> +++ b/drivers/infiniband/sw/rxe/rxe_verbs.h
>>> @@ -219,12 +219,6 @@ struct rxe_resp_info {
>>>        u32                     rkey;
>>>        u32                     length;
>>>
>>> -     /* SRQ only */
>>> -     struct {
>>> -             struct rxe_recv_wqe     wqe;
>>> -             struct ib_sge           sge[RXE_MAX_SGE];
>>> -     } srq_wqe;
>>> -
>>>        /* Responder resources. It's a circular list where the oldest
>>>         * resource is dropped first.
>>>         */
>>> @@ -232,7 +226,15 @@ struct rxe_resp_info {
>>>        unsigned int            res_head;
>>>        unsigned int            res_tail;
>>>        struct resp_res         *res;
>>> +
>>> +     /* SRQ only */
>>> +     /* Must be last as it ends in a flexible-array member. */
>>> +     TRAILING_OVERLAP(struct rxe_recv_wqe, wqe, dma.sge,
>>> +             struct rxe_sge          sge[RXE_MAX_SGE];
>>> +     ) srq_wqe;
>>>    };
>>> +static_assert(offsetof(struct rxe_resp_info, srq_wqe.wqe.dma.sge) ==
>>> +           offsetof(struct rxe_resp_info, srq_wqe.sge));
>>>
>>>    struct rxe_qp {
>>>        struct ib_qp            ibqp;
>>> @@ -269,7 +271,6 @@ struct rxe_qp {
>>>
>>>        struct rxe_req_info     req;
>>>        struct rxe_comp_info    comp;
>>> -     struct rxe_resp_info    resp;
>>>
>>>        atomic_t                ssn;
>>>        atomic_t                skb_out;
>>> @@ -289,6 +290,9 @@ struct rxe_qp {
>>>        spinlock_t              state_lock; /* guard requester and completer */
>>>
>>>        struct execute_work     cleanup_work;
>>> +
>>> +     /* Must be last as it ends in a flexible-array member. */
>>> +     struct rxe_resp_info    resp;
>>>    };
>>>
>>>    enum {
>>
>>