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

Leon Romanovsky
2025-11-11T11:56:26Z

On Tue, Nov 11, 2025 at 12:35:02PM +0900, 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 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.
>
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
> ---
> 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..6498d61e8956 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 ib_sge sge[RXE_MAX_SGE];
> + ) srq_wqe;

Will this change be enough?

diff --git a/drivers/infiniband/sw/rxe/rxe_verbs.h b/drivers/infiniband/sw/rxe/rxe_verbs.h
index fd48075810dd..9ab11421a585 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.
*/
@@ -232,6 +226,12 @@ struct rxe_resp_info {
unsigned int res_head;
unsigned int res_tail;
struct resp_res *res;
+
+ /* SRQ only */
+ struct {
+ struct ib_sge sge[RXE_MAX_SGE];
+ struct rxe_recv_wqe wqe;
+ } srq_wqe;
};

struct rxe_qp {
~