>> drivers/infiniband/hw/qib/qib_sysfs.c:411:1: warning: performing pointer subtraction with a null pointer has undefined behavior +[-Wnull-pointer-subtraction] QIB_DIAGC_ATTR(rc_resends); ^~~~~~~~~~~~~~~~~~~~~~~~~~ drivers/infiniband/hw/qib/qib_sysfs.c:408:51: note: expanded from macro 'QIB_DIAGC_ATTR' .counter = &((struct qib_ibport *)0)->rvp.n_##N - (u64 *)0, \ Use offsetof and accomplish the type check using static_assert. Fixes: 4a7aaf88c89f ("RDMA/qib: Use attributes for the port sysfs") Reported-by: kernel test robot Signed-off-by: Jason Gunthorpe --- drivers/infiniband/hw/qib/qib_sysfs.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/infiniband/hw/qib/qib_sysfs.c b/drivers/infiniband/hw/qib/qib_sysfs.c index d57e49de6650be..452e2355d24eeb 100644 --- a/drivers/infiniband/hw/qib/qib_sysfs.c +++ b/drivers/infiniband/hw/qib/qib_sysfs.c @@ -403,9 +403,11 @@ static ssize_t diagc_attr_store(struct ib_device *ibdev, u32 port_num, } #define QIB_DIAGC_ATTR(N) \ + static_assert(&((struct qib_ibport *)0)->rvp.n_##N != (u64 *)NULL); \ static struct qib_diagc_attr qib_diagc_attr_##N = { \ .attr = __ATTR(N, 0664, diagc_attr_show, diagc_attr_store), \ - .counter = &((struct qib_ibport *)0)->rvp.n_##N - (u64 *)0, \ + .counter = \ + offsetof(struct qib_ibport, rvp.n_##N) / sizeof(u64) \ } QIB_DIAGC_ATTR(rc_resends); base-commit: 6a217437f9f5482a3f6f2dc5fcd27cf0f62409ac -- 2.33.0