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authorGustavo A. R. Silva <gustavo@embeddedor.com>2020-03-06 16:13:33 -0600
committerDavid Sterba <dsterba@suse.com>2020-03-23 17:01:54 +0100
commita8753ee3a859a519613641963464b38b9a79dc9c (patch)
tree6ba657cf3151b7a359406074231c2442feadc8d7 /fs
parent7593f4c53c699699c6968a5fdd795d0fdf99a65d (diff)
btrfs: scrub: 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 <gustavo@embeddedor.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Diffstat (limited to 'fs')
-rw-r--r--fs/btrfs/scrub.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index 16aa680134fd..adaf8ab694d5 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -149,7 +149,7 @@ struct scrub_parity {
*/
unsigned long *ebitmap;
- unsigned long bitmap[0];
+ unsigned long bitmap[];
};
struct scrub_ctx {