On Fri, Jul 25, 2025 at 02:44:52PM +0200, Jimmy Assarsson wrote:

On 7/24/25 8:26 PM, Simon Horman wrote:

quoted

On Thu, Jul 24, 2025 at 11:24:55AM +0200, Jimmy Assarsson wrote:

...

quoted

GCC seems to know that:
* cmd was allocated sizeof(*cmd) = 32 bytes
* struct kvaser_cmd_ext is larger than this (96 bytes)

And it thinks that cmd->header.cmd_no might be CMD_EXTENDED.
This is not true, becuae .cmd_no is set to CMD_LED_ACTION_REQ
earlier in kvaser_usb_hydra_set_led. But still, GCC produces
a big fat warning.

On the one hand we might say this is a shortcoming in GCC,
a position I agree with. But on the other hand, we might follow
the pattern used elsewhere in this file for similar functions,
which seems to make GCC happy, I guess, and it is strictly a guess,
because less context is needed for it to analyse things correctly.

Thanks for finding this!

Marc Kleine-Budde actually sorted this out for other commands some years ago [1],
but I had completely forgotten.

[1] https://lore.kernel.org/all/20221219110104.1073881-1-mkl@pengutronix.de (local)

Nice, thanks for digging that up.