[111/166] lib/bch.c: replace zero-length array with flexible-array member

Commit Message

Andrew Morton April 7, 2020, 3:09 a.m. UTC

From: "Gustavo A. R. Silva" <[e-mail]>
Subject: lib/bch.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/20200211205119.GA21234@embeddedor
Signed-off-by: Gustavo A. R. Silva <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

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

Patch

--- a/lib/bch.c~lib-bch-replace-zero-length-array-with-flexible-array-member
+++ a/lib/bch.c
@@ -102,7 +102,7 @@ 
  */
 struct gf_poly {
 	unsigned int deg;    /* polynomial degree */
-	unsigned int c[0];   /* polynomial terms */
+	unsigned int c[];   /* polynomial terms */
 };
 
 /* given its degree, compute a polynomial size in bytes */