[patch 112/166] lib/ts_bm.c: replace zero-length array with flexible-array member

Andrew Morton
2020-04-07T03:10:03Z

From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Subject: lib/ts_bm.c: 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
inadvertenly introduced[3] to the codebase from now on.

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")

Link: http://lkml.kernel.org/r/20200211205620.GA24694@embeddedor
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

lib/ts_bm.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/lib/ts_bm.c~lib-ts_bm-replace-zero-length-array-with-flexible-array-member
+++ a/lib/ts_bm.c
@@ -52,7 +52,7 @@ struct ts_bm
u8 * pattern;
unsigned int patlen;
unsigned int bad_shift[ASIZE];
- unsigned int good_shift[0];
+ unsigned int good_shift[];
};

static unsigned int bm_find(struct ts_config *conf, struct ts_state *state)
_