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Subject: Re: [v6] coccinelle: semantic code search for missing put_device()
To:     Julia Lawall <julia.lawall@lip6.fr>,
        Wen Yang <yellowriver2010@hotmail.com>
Cc:     Gilles Muller <Gilles.Muller@lip6.fr>,
        Nicolas Palix <nicolas.palix@imag.fr>,
        Michal Marek <michal.lkml@markovi.net>,
        Masahiro Yamada <yamada.masahiro@socionext.com>,
        Wen Yang <wen.yang99@zte.com.cn>,
        Cheng Shengyu <cheng.shengyu@zte.com.cn>,
        kernel-janitors@vger.kernel.org,
        LKML <linux-kernel@vger.kernel.org>,
        Coccinelle <cocci@systeme.lip6.fr>
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From:   Markus Elfring <Markus.Elfring@web.de>
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Date:   Sun, 17 Feb 2019 14:14:38 +0100
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Sender: linux-kernel-owner@vger.kernel.org
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>> =E2=80=A6
>> +@search exists@
>> +local idexpression id;
>> +expression x,e,e1;
>> +position p1,p2;
>> =E2=80=A6
>> +@@
>> +
>> +id =3D of_find_device_by_node@p1(x)
>> +... when !=3D e =3D id
>> =E2=80=A6
>>
>> Or:
>>
>> =E2=80=A6
>> + ... when !=3D id =3D e
>> =E2=80=A6
>>
>>
>> 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 ne=
ed
> to be freed just because the original local variable goes out of scope a=
t
> the end of the function.

I find this description reasonable to some degree.

(I am unsure if a programmer would like to fiddle with return value storag=
e
in a data structure member from a local variable.)


> when !=3D e =3D id achieves this behavior.

I can not agree to this view completely because of the meaning that is con=
nected
with these variable identifiers.

Both metavariables share the kind =E2=80=9Cexpression=E2=80=9D. So I can i=
magine
that there is an intersection for the source code match possibility.
But one was intentionally restricted to the kind =E2=80=9Clocal idexpressi=
on=E2=80=9D so far.

Which data element should not get reassigned here (before a corresponding
null pointer check)?

Regards,
Markus