From 3fc131663cec7ca8e05bf25d99cecc2ab56bc50d Mon Sep 17 00:00:00 2001 From: "Gustavo A. R. Silva" Date: Mon, 9 Mar 2020 15:27:15 -0500 Subject: [PATCH] udf: udf_sb.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") Link: https://lore.kernel.org/r/20200309202715.GA9428@embeddedor Signed-off-by: Gustavo A. R. Silva Signed-off-by: Jan Kara --- fs/udf/udf_sb.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/udf/udf_sb.h b/fs/udf/udf_sb.h index 3d83be54c474..758efe557a19 100644 --- a/fs/udf/udf_sb.h +++ b/fs/udf/udf_sb.h @@ -83,7 +83,7 @@ struct udf_virtual_data { struct udf_bitmap { __u32 s_extPosition; int s_nr_groups; - struct buffer_head *s_block_bitmap[0]; + struct buffer_head *s_block_bitmap[]; }; struct udf_part_map {