linux-kernel - Re: [v6] coccinelle: semantic code search for missing put

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Date:   Sun, 17 Feb 2019 13:52:28 +0100 (CET)
From:   Julia Lawall <julia.lawall@...6.fr>
To:     Markus Elfring <Markus.Elfring@....de>
cc:     Wen Yang <yellowriver2010@...mail.com>,
        Gilles Muller <Gilles.Muller@...6.fr>,
        Nicolas Palix <nicolas.palix@...g.fr>,
        Michal Marek <michal.lkml@...kovi.net>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Wen Yang <wen.yang99@....com.cn>,
        Cheng Shengyu <cheng.shengyu@....com.cn>,
        kernel-janitors@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>,
        Coccinelle <cocci@...teme.lip6.fr>
Subject: Re: [v6] coccinelle: semantic code search for missing put_device()



On Sun, 17 Feb 2019, Markus Elfring wrote:

> >> If you would insist on the specification of such an assignment exclusion
> >> for a SmPL ellipsis:
> >> Can we agree on a correct order?
> >
> > I don't get your point.
>
> I propose to take another closer look at a bit of SmPL code.
>
>
> > There is no correct order.
>
> I have got an other software development view here.
>
>
> > Each order expresses something different.
>
> I agree to this information.
>
>
> > The order that is currently in the semantic patch is the one
> > that is more likely in practice.
>
> Please check once more.
>
> …
> +@...rch exists@
> +local idexpression id;
> +expression x,e,e1;
> +position p1,p2;
> …
> +@@
> +
> +id = of_find_device_by_node@p1(x)
> +... when != e = id
> …
>
> Or:
>
> …
> + ... when != id = e
> …
>
>
> Which SmPL specification will achieve the desired software behaviour?

The desired behavior is to check whether the allocated value is saved in
some other variable (typically a structure field) and thus it doesn't need
to be freed just because the original local variable goes out of scope at
the end of the function.  when != e = id achieves this behavior.

julia