r8152: 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 <gustavo@embeddedor.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/usb/r8152.c b/drivers/net/usb/r8152.c
index 709578f..b8d2722 100644 (file)
--- a/drivers/net/usb/r8152.c
+++ b/drivers/net/usb/r8152.c
@@ -891,7 +891,7 @@ struct fw_block {
 struct fw_header {
        u8 checksum[32];
        char version[RTL_VER_SIZE];
-       struct fw_block blocks[0];
+       struct fw_block blocks[];
 } __packed;
 
 /**
@@ -930,7 +930,7 @@ struct fw_mac {
        __le32 reserved;
        __le16 fw_ver_reg;
        u8 fw_ver_data;
-       char info[0];
+       char info[];
 } __packed;
 
 /**
@@ -982,7 +982,7 @@ struct fw_phy_nc {
        __le16 bp_start;
        __le16 bp_num;
        __le16 bp[4];
-       char info[0];
+       char info[];
 } __packed;
 
 enum rtl_fw_type {