lib/ts_fsm.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 4287773bdd7a ("cxgb3/l2t: Fix undefined behaviour")

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/20200211205813.GA25602@embeddedor
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/lib/ts_fsm.c b/lib/ts_fsm.c
index 9c873cadab7c6cb946044584398c9b8aa93134eb..ab749ec10ab538550729e5cc570107b683038a23 100644 (file)
--- a/lib/ts_fsm.c
+++ b/lib/ts_fsm.c
@@ -32,7 +32,7 @@
 struct ts_fsm
 {
        unsigned int            ntokens;
-       struct ts_fsm_token     tokens[0];
+       struct ts_fsm_token     tokens[];
 };
 
 /* other values derived from ctype.h */