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Date:   Sat, 22 Oct 2016 08:55:48 +0200
From:   Jiri Pirko <>
To:     Linus Torvalds <>
Cc:     Arnd Bergmann <>,
        "David S. Miller" <>,
        Alexander Duyck <>,
        Tom Herbert <>,
        Jiri Pirko <>,
        Hadar Hen Zion <>,
        Gao Feng <>, Eric Garver <>,
        Amir Vadai <>,
        Network Development <>,
        Linux Kernel Mailing List <>
Subject: Re: [PATCH] flow_dissector: avoid uninitialized variable access

Sat, Oct 22, 2016 at 03:48:48AM CEST, wrote:
>On Fri, Oct 21, 2016 at 9:31 AM, Jiri Pirko <> wrote:
>> I don't see how vlan could be used uninitialized. But I understand that
>> this is impossible for gcc to track it. Please just use uninitialized_var()
>Actually, I think we should never use "uninitialized_var()" except
>possibly for arrays or structures that gcc can complain about.
>It's a horrible thing to use, in that it adds extra cruft to the
>source code, and then shuts up a compiler warning (even the _reliable_
>warnings from gcc).
>It's much better to just initialize the variable, and if gcc some day
>gets smarter and sees that it  is unnecessary and always overwritten,
>so much the better. The cost of initializing a single word is
>basically zero.

On the other hand, I would agrue that initializing a var to "some" value
that is never used might confuse the reader. He would naturally try to
understand the reason for that exact value in initialization.

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