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    SubjectRe: [PATCH] net, llc: Avoid undefined behaviour in llc_conn_ac_inc_vr_by_1()
    On Sat, 25 Jun 2011, David Miller wrote:

    > From: Jesper Juhl <jj@chaosbits.net>
    > Date: Sun, 26 Jun 2011 00:11:12 +0200 (CEST)
    >
    > > Introduce a sequence point (;) between two writes to llc_sk(sk)->vR in
    > > net/llc/llc_c_ac.c:llc_conn_ac_inc_vr_by_1() so that the order in
    > > which the writes happen become well defined.
    > >
    > > While the code may work fine now it may break at any time with a
    > > different compiler, a new version of current compiler or even just a
    > > different optimization level of the current compiler. Much better to
    > > clearly express what's intended in a way that guarantees the result.
    > >
    > > Signed-off-by: Jesper Juhl <jj@chaosbits.net>
    >
    > How about fixing the macro so that it doesn't have side effects
    > like this?
    >
    > That's much better than a 6 line (improperly formatted, BTW) comment
    > every time someone tried to use that macros with an lvalue that isn't
    > a local variable.

    Sure, that's also a way to go - better probably.
    I just thought that I would fix up the one call site I found that was
    problematic...
    But gimme a couple of days (I don't have much free time) and I'll cook up
    a different patch.

    --
    Jesper Juhl <jj@chaosbits.net> http://www.chaosbits.net/
    Don't top-post http://www.catb.org/jargon/html/T/top-post.html
    Plain text mails only, please.



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