From a1c4b9247ddfb62fe3a23eb53d250382e82fae77 Mon Sep 17 00:00:00 2001 From: "Gustavo A. R. Silva" Date: Mon, 23 Mar 2020 19:12:17 -0500 Subject: [PATCH] rio.h: 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 --- include/linux/rio.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/include/linux/rio.h b/include/linux/rio.h index 317bace5ac64..2cd637268b4f 100644 --- a/include/linux/rio.h +++ b/include/linux/rio.h @@ -100,7 +100,7 @@ struct rio_switch { u32 port_ok; struct rio_switch_ops *ops; spinlock_t lock; - struct rio_dev *nextdev[0]; + struct rio_dev *nextdev[]; }; /** @@ -201,7 +201,7 @@ struct rio_dev { u8 hopcount; struct rio_dev *prev; atomic_t state; - struct rio_switch rswitch[0]; /* RIO switch info */ + struct rio_switch rswitch[]; /* RIO switch info */ }; #define rio_dev_g(n) list_entry(n, struct rio_dev, global_list) -- 2.34.1