drop_monitor: 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")

Gustavo A. R. Silva committed 6 years ago

Commit 17766581 parent 2e83abd1 file · +2 −2Browse files

Unified · Split

include/uapi/linux/net_dropmon.h+2−2

@@ -29,12 +29,12 @@ struct net_dm_config_entry { · 28 unmodified lines
29		29
30	struct net_dm_config_msg {	30	struct net_dm_config_msg {
31	__u32 entries;	31	__u32 entries;
32	struct net_dm_config_entry options[0];	32	struct net_dm_config_entry options[];
33	};	33	};
34		34
35	struct net_dm_alert_msg {	35	struct net_dm_alert_msg {
36	__u32 entries;	36	__u32 entries;
37	struct net_dm_drop_point points[0];	37	struct net_dm_drop_point points[];
38	};	38	};
39		39
40	struct net_dm_user_msg {	40	struct net_dm_user_msg {