Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <202203021333.mMJpWPzx-lkp@intel.com> <5f13b914-e309-49ee-4f98-c81780c478b9@intel.com>
 <20220302103219.kvpfhc6qz42t3pvv@pengutronix.de> <CAMZ6Rq+HR=j2mD97etTgSapOix96P=pK70bTr9HeJu2Mjkn3+g@mail.gmail.com>
 <20220302130423.ddd2ulldffpo5lb2@pengutronix.de>
In-Reply-To: <20220302130423.ddd2ulldffpo5lb2@pengutronix.de>
From:   Vincent MAILHOL <mailhol.vincent@wanadoo.fr>
Date:   Wed, 2 Mar 2022 23:42:53 +0900
Message-ID: <CAMZ6Rq+J0CH_HvK1ax=VcWKqih+B_0Nfoc9jZMiq7OtuXL06hw@mail.gmail.com>
Subject: Re: drivers/net/can/usb/etas_es58x/es58x_fd.c:174:8: warning:
 Uninitialized variable: rx_event_msg [uninitvar]
To:     Marc Kleine-Budde <mkl@pengutronix.de>
Cc:     kernel test robot <yujie.liu@intel.com>, kbuild-all@lists.01.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Arunachalam Santhanam <Arunachalam.Santhanam@in.bosch.com>,
        linux-can <linux-can@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Wed. 2 Mar 2022 at 22:04, Marc Kleine-Budde <mkl@pengutronix.de> wrote:
> 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.

Sorry, I do not get your example. If bar is NULL,
| void *foo = bar->baz;
would segfault and thus the check is not reached.

If bar is not NULL, the check succeeds.

In both cases, the return statement of the if branch is never
executed making this some dead code. So I do not see why this is
an issue if the compiler removes it.


Yours sincerely,
Vincent Mailhol