From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Wed, 12 Feb 2020 18:22:39 -0600 From: "Gustavo A. R. Silva" Subject: [PATCH] rpmsg: virtio_rpmsg_bus: Replace zero-length array with flexible-array member Message-ID: <20200213002239.GA30190@embeddedor.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline To: Ohad Ben-Cohen , Bjorn Andersson Cc: linux-remoteproc@vger.kernel.org, linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" List-ID: 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 --- drivers/rpmsg/virtio_rpmsg_bus.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/rpmsg/virtio_rpmsg_bus.c b/drivers/rpmsg/virtio_rpmsg_bus.c index 376ebbf880d6..07d4f3374098 100644 --- a/drivers/rpmsg/virtio_rpmsg_bus.c +++ b/drivers/rpmsg/virtio_rpmsg_bus.c @@ -89,7 +89,7 @@ struct rpmsg_hdr { u32 reserved; u16 len; u16 flags; - u8 data[0]; + u8 data[]; } __packed; /** -- 2.23.0