From e76018cb604ace486de9cf85898c14bb2b47faff Mon Sep 17 00:00:00 2001 From: "Gustavo A. R. Silva" Date: Mon, 23 Mar 2020 16:48:10 -0500 Subject: [PATCH] can: dev: peak_canfd.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 --- include/linux/can/dev/peak_canfd.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/include/linux/can/dev/peak_canfd.h b/include/linux/can/dev/peak_canfd.h index 511a37302fea..5fd627e9da19 100644 --- a/include/linux/can/dev/peak_canfd.h +++ b/include/linux/can/dev/peak_canfd.h @@ -189,7 +189,7 @@ struct __packed pucan_rx_msg { u8 client; __le16 flags; __le32 can_id; - u8 d[0]; + u8 d[]; }; /* uCAN error types */ @@ -266,7 +266,7 @@ struct __packed pucan_tx_msg { u8 client; __le16 flags; __le32 can_id; - u8 d[0]; + u8 d[]; }; /* build the cmd opcode_channel field with respect to the correct endianness */