linux-kernel - Re: -Wsometimes-uninitialized Clang warning in drivers/tty/serial/qcom_geni

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Message-ID: <20190308084022.GA31474@kroah.com>
Date:   Fri, 8 Mar 2019 09:40:22 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Nathan Chancellor <natechancellor@...il.com>
Cc:     Andy Gross <andy.gross@...aro.org>,
        David Brown <david.brown@...aro.org>,
        Karthikeyan Ramasubramanian <kramasub@...eaurora.org>,
        Douglas Anderson <dianders@...omium.org>,
        Ryan Case <ryandcase@...omium.org>,
        linux-arm-msm@...r.kernel.org, linux-serial@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        clang-built-linux@...glegroups.com
Subject: Re: -Wsometimes-uninitialized Clang warning in
 drivers/tty/serial/qcom_geni_serial.c

On Thu, Mar 07, 2019 at 05:45:26PM -0700, Nathan Chancellor wrote:
> Hi all,
> 
> We are trying to get Clang's -Wsometimes-uninitialized turned on for the
> kernel as it can catch some bugs that GCC can't. This warning came up:
> 
> drivers/tty/serial/qcom_geni_serial.c:1079:6: warning: variable 'baud' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
>         if (options)
>             ^~~~~~~
> drivers/tty/serial/qcom_geni_serial.c:1082:37: note: uninitialized use occurs here
>         return uart_set_options(uport, co, baud, parity, bits, flow);
>                                            ^~~~
> drivers/tty/serial/qcom_geni_serial.c:1079:2: note: remove the 'if' if its condition is always true
>         if (options)
>         ^~~~~~~~~~~~
> drivers/tty/serial/qcom_geni_serial.c:1053:10: note: initialize the variable 'baud' to silence this warning
>         int baud;
>                 ^
>                  = 0
> 1 warning generated.
> 
> While this is probably not an issue in practice (I assume baud is always
> supplied as an option), we should clean up this warning. I would fix it
> myself but I have no idea what baud's initial value should be as it
> seems it is dependent on the driver. Your input would be much
> appreciated.

this function can be called with the option variable set to NULL, so
there could not be a default baud rate set, nice catch.

As for the default, let's just be sane and set it to 9600 as that's a
normal default baudrate.

Do you want to make up a patch for this, or do you need me to?

thanks,

greg k-h