From 3c9210d45d50edd13aca45131522211b93c7812d Mon Sep 17 00:00:00 2001 From: "Gustavo A. R. Silva" Date: Wed, 1 Apr 2020 21:03:48 -0700 Subject: ocfs2: 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: Andrew Morton Acked-by: Joseph Qi Cc: Mark Fasheh Cc: Joel Becker Cc: Junxiao Bi Cc: Changwei Ge Cc: Gang He Cc: Jun Piao Link: http://lkml.kernel.org/r/20200213160244.GA6088@embeddedor Signed-off-by: Linus Torvalds --- fs/ocfs2/journal.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'fs/ocfs2/journal.c') diff --git a/fs/ocfs2/journal.c b/fs/ocfs2/journal.c index 68ba354cf361..b425f0b01dce 100644 --- a/fs/ocfs2/journal.c +++ b/fs/ocfs2/journal.c @@ -91,7 +91,7 @@ enum ocfs2_replay_state { struct ocfs2_replay_map { unsigned int rm_slots; enum ocfs2_replay_state rm_state; - unsigned char rm_replay_slots[0]; + unsigned char rm_replay_slots[]; }; static void ocfs2_replay_map_set_state(struct ocfs2_super *osb, int state) -- cgit v1.2.3