From 53cb2cfaa62d122fa9d92398926a6b7e8f052844 Mon Sep 17 00:00:00 2001 From: "Gustavo A. R. Silva" Date: Fri, 28 Feb 2020 07:59:59 -0600 Subject: [PATCH] cfg802154: 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 Signed-off-by: Stefan Schmidt --- include/net/cfg802154.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/net/cfg802154.h b/include/net/cfg802154.h index 6f86073a5d7d..6ed07844eb24 100644 --- a/include/net/cfg802154.h +++ b/include/net/cfg802154.h @@ -214,7 +214,7 @@ struct wpan_phy { /* the network namespace this phy lives in currently */ possible_net_t _net; - char priv[0] __aligned(NETDEV_ALIGN); + char priv[] __aligned(NETDEV_ALIGN); }; static inline struct net *wpan_phy_net(struct wpan_phy *wpan_phy)