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Date: Mon, 20 Sep 2021 14:30:29 +0200
From: Arnd Bergmann <arnd@...nel.org>
To: Vincent Mailhol <mailhol.vincent@...adoo.fr>,
Wolfgang Grandegger <wg@...ndegger.com>,
Marc Kleine-Budde <mkl@...gutronix.de>,
"David S. Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>
Cc: Arnd Bergmann <arnd@...db.de>,
Arunachalam Santhanam <arunachalam.santhanam@...bosch.com>,
linux-can@...r.kernel.org, netdev@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH] can: etas_es58x: avoid -Wzero-length-bounds warning
From: Arnd Bergmann <arnd@...db.de>
gcc complains when writing into a zero-length array:
drivers/net/can/usb/etas_es58x/es581_4.c: In function 'es581_4_tx_can_msg':
drivers/net/can/usb/etas_es58x/es581_4.c:374:42: warning: array subscript 65535 is outside the bounds of an interior zero-length array 'u8[0]' {aka 'unsigned char[]'} [-Wzero-length-bounds]
374 | tx_can_msg = (typeof(tx_can_msg))&es581_4_urb_cmd->raw_msg[msg_len];
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from drivers/net/can/usb/etas_es58x/es58x_core.h:21,
from drivers/net/can/usb/etas_es58x/es581_4.c:15:
drivers/net/can/usb/etas_es58x/es581_4.h:195:20: note: while referencing 'raw_msg'
195 | u8 raw_msg[0];
| ^~~~~~~
CC [M] drivers/net/can/usb/etas_es58x/es58x_fd.o
drivers/net/can/usb/etas_es58x/es58x_fd.c: In function 'es58x_fd_tx_can_msg':
drivers/net/can/usb/etas_es58x/es58x_fd.c:360:42: warning: array subscript 65535 is outside the bounds of an interior zero-length array 'u8[0]' {aka 'unsigned char[]'} [-Wzero-length-bounds]
360 | tx_can_msg = (typeof(tx_can_msg))&es58x_fd_urb_cmd->raw_msg[msg_len];
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from drivers/net/can/usb/etas_es58x/es58x_core.h:22,
from drivers/net/can/usb/etas_es58x/es58x_fd.c:17:
drivers/net/can/usb/etas_es58x/es58x_fd.h:222:20: note: while referencing 'raw_msg'
222 | u8 raw_msg[0];
| ^~~~~~~
The solution is usually to use a flexible-array member the struct, but
we can't directly have that inside of a union, nor can it be the only
member of a struct, so add a dummy struct with another zero-length
member to get the intended behavior.
If someone has a better workaround, let me know and I can send a new
patch, as this version is rather ugly.
Fixes: f4f5247daa45 ("can: etas_es58x: rewrite the message cast in es58{1,_fd}_tx_can_msg to increase readability")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
drivers/net/can/usb/etas_es58x/es581_4.h | 5 ++++-
drivers/net/can/usb/etas_es58x/es58x_fd.h | 5 ++++-
2 files changed, 8 insertions(+), 2 deletions(-)
diff --git a/drivers/net/can/usb/etas_es58x/es581_4.h b/drivers/net/can/usb/etas_es58x/es581_4.h
index 4bc60a6df697..ac5ef88db565 100644
--- a/drivers/net/can/usb/etas_es58x/es581_4.h
+++ b/drivers/net/can/usb/etas_es58x/es581_4.h
@@ -192,7 +192,10 @@ struct es581_4_urb_cmd {
struct es581_4_rx_cmd_ret rx_cmd_ret;
__le64 timestamp;
u8 rx_cmd_ret_u8;
- u8 raw_msg[0];
+ struct {
+ u8 __pad[0];
+ u8 raw_msg[];
+ };
} __packed;
__le16 reserved_for_crc16_do_not_use;
diff --git a/drivers/net/can/usb/etas_es58x/es58x_fd.h b/drivers/net/can/usb/etas_es58x/es58x_fd.h
index a191891b8777..253e7bafd0b6 100644
--- a/drivers/net/can/usb/etas_es58x/es58x_fd.h
+++ b/drivers/net/can/usb/etas_es58x/es58x_fd.h
@@ -219,7 +219,10 @@ struct es58x_fd_urb_cmd {
struct es58x_fd_tx_ack_msg tx_ack_msg;
__le64 timestamp;
__le32 rx_cmd_ret_le32;
- u8 raw_msg[0];
+ struct {
+ u8 __pad[0];
+ u8 raw_msg[];
+ };
} __packed;
__le16 reserved_for_crc16_do_not_use;
--
2.29.2
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