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

["Gustavo A. R. Silva" <gustavo@embeddedor.com>]

On 12/24/25 02:19, Greg Sword wrote:
> On Wed, Dec 24, 2025 at 12:59 AM Gustavo A. R. Silva
> <gustavo@embeddedor.com> wrote:
>>
>>
>>
>> On 12/24/25 01:38, Greg Sword wrote:
>>> On Tue, Dec 23, 2025 at 5:35 PM Gustavo A. R. Silva
>>> <gustavo@embeddedor.com> wrote:
>>>>
>>>>
>>>>
>>>> On 12/23/25 13:41, Zhu Yanjun wrote:
>>>>> From: "Gustavo A. R. Silva" <gustavoars@kernel.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@linux.dev>
>>>>> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.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’ve read through the full discussion and understand how this evolved.
> Based on that, I believe there may be a misunderstanding on your side.

Okay, thanks for your contribution then.

-Gustavo

> 
>>
>>>> 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 {
>>>>
>>>>
>>