linux-kernel - Re: [PATCH 06/12] s390: ctcm: fix ctcm_new

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Date:   Wed, 10 Apr 2019 18:00:07 +0200
From:   Martin Schwidefsky <schwidefsky@...ibm.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Heiko Carstens <heiko.carstens@...ibm.com>,
        Julian Wiedmann <jwi@...ux.ibm.com>,
        Ursula Braun <ubraun@...ux.ibm.com>,
        clang-built-linux@...glegroups.com,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nathan Chancellor <natechancellor@...il.com>,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 06/12] s390: ctcm: fix ctcm_new_device error return code

On Mon,  8 Apr 2019 23:26:19 +0200
Arnd Bergmann <arnd@...db.de> wrote:

> clang points out that the return code from this function is
> undefined for one of the error paths:
> 
> ../drivers/s390/net/ctcm_main.c:1595:7: warning: variable 'result' is used uninitialized whenever 'if' condition is true
>       [-Wsometimes-uninitialized]
>                 if (priv->channel[direction] == NULL) {
>                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> ../drivers/s390/net/ctcm_main.c:1638:9: note: uninitialized use occurs here
>         return result;
>                ^~~~~~
> ../drivers/s390/net/ctcm_main.c:1595:3: note: remove the 'if' if its condition is always false
>                 if (priv->channel[direction] == NULL) {
>                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> ../drivers/s390/net/ctcm_main.c:1539:12: note: initialize the variable 'result' to silence this warning
>         int result;
>                   ^
> 
> Make it return -ENODEV here, as in the related failure cases.
> gcc has a known bug in underreporting some of these warnings
> when it has already eliminated the assignment of the return code
> based on some earlier optimization step.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Added to our internal tree for Julian to pick up.

-- 
blue skies,
   Martin.

"Reality continues to ruin my life." - Calvin.