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

Showing the changes to include/uapi/linux (1 of 1 file). Show all

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include/uapi/linux/net_dropmon.h+2−2

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