net: wireless: wl3501.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")

---
 drivers/net/wireless/wl3501.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index efdce9ae36ea..b446cb369557 100644
@@ -231,7 +231,7 @@ struct iw_mgmt_info_element {
 	u8 id; /* one of enum iw_mgmt_info_element_ids,
 		  but sizeof(enum) > sizeof(u8) :-( */
 	u8 len;
-	u8 data[0];
+	u8 data[];
 } __packed;
 
 struct iw_mgmt_essid_pset {

2.23.0

Patch applied to wireless-drivers-next.git, thanks.

53efdc9cb9e6 wl3501_cs: Replace zero-length array with flexible-array member

https://patchwork.kernel.org/patch/11448183/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches