posix_acl.h: 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")
Signed-off-by: Gustavo A. R. Silva <[email protected]>
diff --git a/include/linux/posix_acl.h b/include/linux/posix_acl.h
index 540595a..90797f1 100644
--- a/include/linux/posix_acl.h
+++ b/include/linux/posix_acl.h
@@ -28,7 +28,7 @@ struct posix_acl {
refcount_t a_refcount;
struct rcu_head a_rcu;
unsigned int a_count;
- struct posix_acl_entry a_entries[0];
+ struct posix_acl_entry a_entries[];
};
#define FOREACH_ACL_ENTRY(pa, acl, pe) \
