clang emits a -Wunaligned-access warning on struct __packed
ems_cpc_msg.
The reason is that the anonymous union msg (not declared as packed) is
being packed right after some non naturally aligned variables (3*8
bits + 2*32) inside a packed struct:
| struct __packed ems_cpc_msg {
| u8 type; /* type of message */
| u8 length; /* length of data within union 'msg' */
| u8 msgid; /* confirmation handle */
| __le32 ts_sec; /* timestamp in seconds */
| __le32 ts_nsec; /* timestamp in nano seconds */
| /* ^ not naturally as aligned */
|
| union {
| /* ^ not declared as packed */
| u8 generic[64];
| struct cpc_can_msg can_msg;
| struct cpc_can_params can_params;
| struct cpc_confirm confirmation;
| struct cpc_overrun overrun;
| struct cpc_can_error error;
| struct cpc_can_err_counter err_counter;
| u8 can_state;
| } msg;
| };
Starting from LLVM 14, having an unpacked struct nested in a packed
struct triggers a warning. c.f. [1].
Fix the warning by marking the anonymous union as packed.
[1] https://github.com/llvm/llvm-project/issues/55520
Fixes: 702171adeed3 ("ems_usb: Added support for EMS CPC-USB/ARM7 CAN/USB interface")
Cc: Gerhard Uttenthaler <uttenthaler@xxxxxxxxxxxxxxxx>
Cc: Sebastian Haas <haas@xxxxxxxxxxxxxxxx>
Signed-off-by: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx>
---
drivers/net/can/usb/ems_usb.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/net/can/usb/ems_usb.c b/drivers/net/can/usb/ems_usb.c
index bbec3311d893..e09b6732117c 100644
--- a/drivers/net/can/usb/ems_usb.c
+++ b/drivers/net/can/usb/ems_usb.c
@@ -194,7 +194,7 @@ struct __packed ems_cpc_msg {
__le32 ts_sec; /* timestamp in seconds */
__le32 ts_nsec; /* timestamp in nano seconds */
- union {
+ union __packed {
u8 generic[64];
struct cpc_can_msg can_msg;
struct cpc_can_params can_params;
--
2.35.1
