From 35e032462bf8c7847d4ef7b70a3c8dc17f814c97 Mon Sep 17 00:00:00 2001 From: "Gustavo A. R. Silva" Date: Fri, 14 Feb 2020 11:13:02 -0600 Subject: [PATCH] dmanegine: ioat/dca: Replace zero-length array with flexible-array member The current codebase makes use of the zero-length array language extension to the C90 standard, but the preferred mechanism to declare variable-length types such as these ones is a flexible array member[1][2], introduced in C99: struct foo { int stuff; struct boo array[]; }; By making use of the mechanism above, we will get a compiler warning in case the flexible array does not occur last in the structure, which will help us prevent some kind of undefined behavior bugs from being inadvertently introduced[3] to the codebase from now on. Also, notice that, dynamic memory allocations won't be affected by this change: "Flexible array members have incomplete type, and so the sizeof operator may not be applied. As a quirk of the original implementation of zero-length arrays, sizeof evaluates to zero."[1] This issue was found with the help of Coccinelle. [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html [2] https://github.com/KSPP/linux/issues/21 [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour") Signed-off-by: Gustavo A. R. Silva Link: https://lore.kernel.org/r/20200214171302.GA20586@embeddedor Signed-off-by: Vinod Koul --- drivers/dma/ioat/dca.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/dma/ioat/dca.c b/drivers/dma/ioat/dca.c index be61c32a876f..0be385587c4c 100644 --- a/drivers/dma/ioat/dca.c +++ b/drivers/dma/ioat/dca.c @@ -102,7 +102,7 @@ struct ioat_dca_priv { int max_requesters; int requester_count; u8 tag_map[IOAT_TAG_MAP_LEN]; - struct ioat_dca_slot req_slots[0]; + struct ioat_dca_slot req_slots[]; }; static int ioat_dca_dev_managed(struct dca_provider *dca,