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authorGustavo A. R. Silva <gustavo@embeddedor.com>2020-02-28 07:47:58 -0600
committerMarcel Holtmann <marcel@holtmann.org>2020-02-28 14:51:30 +0100
commit8788a1ee070ab9984015ac6ab6af49f2fbfb2cb3 (patch)
treebd8931aecd4b7a0a68e257173d00d5cd076f21fe /include/net/6lowpan.h
parent4b127bd5f2cc1b2da041f472dab6dc729cdd4711 (diff)
6lowpan: 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> Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Diffstat (limited to 'include/net/6lowpan.h')
-rw-r--r--include/net/6lowpan.h2
1 files changed, 1 insertions, 1 deletions
diff --git a/include/net/6lowpan.h b/include/net/6lowpan.h
index a71378007e61..c80539be1542 100644
--- a/include/net/6lowpan.h
+++ b/include/net/6lowpan.h
@@ -138,7 +138,7 @@ struct lowpan_dev {
struct lowpan_iphc_ctx_table ctx;
/* must be last */
- u8 priv[0] __aligned(sizeof(void *));
+ u8 priv[] __aligned(sizeof(void *));
};
struct lowpan_802154_neigh {