linux-kernel - Re: drivers/net/can/usb/etas_es58x/es58x_fd.c:174:8: warning: Uninitialized variable: rx_event

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Message-ID: <20220302130423.ddd2ulldffpo5lb2@pengutronix.de>
Date:   Wed, 2 Mar 2022 14:04:23 +0100
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     Vincent MAILHOL <mailhol.vincent@...adoo.fr>
Cc:     kernel test robot <yujie.liu@...el.com>, kbuild-all@...ts.01.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Arunachalam Santhanam <Arunachalam.Santhanam@...bosch.com>,
        linux-can <linux-can@...r.kernel.org>
Subject: Re: drivers/net/can/usb/etas_es58x/es58x_fd.c:174:8: warning:
 Uninitialized variable: rx_event_msg [uninitvar]

On 02.03.2022 21:49:27, Vincent MAILHOL wrote:
> > I think it's possible to assign rx_event_msg before the
> > es58x_check_msg_len().
> 
> Yes, I will do so. Even if this is a false positive, this pattern
> can be misleading. e.g. during a code review, this does indeed
> look incorrect at first glance.
> 
> Also, doing such change would be consistent with was is done in
> other functions:
> https://elixir.bootlin.com/linux/latest/source/drivers/net/can/usb/etas_es58x/es58x_fd.c#L210
> 
> This not being a bug fix, is it fine to send it to net-next?

ACK

> Or do you see a need to backport this?

Don't think so.

> > I think (hope?) the compiler will not optimize
> > anything away. :)
> 
> With a function call and a return statement, the compiler would
> need to be severely defective to try to optimize this away :)

I was thinking of this:

| void *foo = bar->baz;
| 
| if (!bar)
|         return;
| 
| printf("%p", foo);

There were/are compilers that optimize the bar NULL pointer check away,
because bar has already been de-referenced.

Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde           |
Embedded Linux                   | https://www.pengutronix.de  |
Vertretung West/Dortmund         | Phone: +49-231-2826-924     |
Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-5555 |

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