net: sched: Replace zero-length array with flexible-array member (b90feaff) · Commits · 戴 / test

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 ("cxgb3/l2t: Fix undefined behaviour") Signed-off-by:

Gustavo A. R. Silva <gustavo@embeddedor.com> Signed-off-by:

David S. Miller <davem@davemloft.net>

include/net/pkt_sched.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -181,7 +181,7 @@ struct tc_taprio_qopt_offload {
		u64 cycle_time_extension;

		size_t num_entries;
		struct tc_taprio_sched_entry entries[0];
		struct tc_taprio_sched_entry entries[];
		};

		/* Reference counting */

net/sched/em_ipt.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -22,7 +22,7 @@ struct em_ipt_match {
		const struct xt_match *match;
		u32 hook;
		u8 nfproto;
		u8 match_data[0] __aligned(8);
		u8 match_data[] __aligned(8);
		};

		struct em_ipt_xt_match {

net/sched/em_nbyte.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -16,7 +16,7 @@

		struct nbyte_data {
		struct tcf_em_nbyte hdr;
		char pattern[0];
		char pattern[];
		};

		static int em_nbyte_change(struct net net, void data, int data_len,

net/sched/sch_atm.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -58,7 +58,7 @@ struct atm_flow_data {
		struct atm_flow_data excess; / flow for excess traffic;
		NULL to set CLP instead */
		int hdr_len;
		unsigned char hdr[0]; /* header data; MUST BE LAST */
		unsigned char hdr[]; /* header data; MUST BE LAST */
		};

		struct atm_qdisc_data {

net/sched/sch_netem.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -66,7 +66,7 @@

		struct disttable {
		u32 size;
		s16 table[0];
		s16 table[];
		};

		struct netem_sched_data {

Admin message