| Message ID | 20200319225133.GA29672@embeddedor.com |
|---|---|
| State | New |
| Headers | show |
| Series | [next] atmel: at76c50x-usb.h: Replace zero-length array with flexible-array member | expand |
diff --git a/drivers/net/wireless/atmel/at76c50x-usb.h b/drivers/net/wireless/atmel/at76c50x-usb.h index f56863403b05..746e64dfd8aa 100644 --- a/drivers/net/wireless/atmel/at76c50x-usb.h +++ b/drivers/net/wireless/atmel/at76c50x-usb.h @@ -151,7 +151,7 @@ struct at76_command { u8 cmd; u8 reserved; __le16 size; - u8 data[0]; + u8 data[]; } __packed; /* Length of Atmel-specific Rx header before 802.11 frame */
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> --- drivers/net/wireless/atmel/at76c50x-usb.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)