linux-kernel - Re: [v5] Coccinelle: semantic code search for missing put

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Date:   Fri, 15 Feb 2019 14:15:17 +0100
From:   Markus Elfring <Markus.Elfring@....de>
To:     Julia Lawall <julia.lawall@...6.fr>,
        Wen Yang <wen.yang99@....com.cn>
Cc:     Gilles Muller <Gilles.Muller@...6.fr>,
        Nicolas Palix <nicolas.palix@...g.fr>,
        Michal Marek <michal.lkml@...kovi.net>,
        Yi Wang <wang.yi59@....com.cn>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Wen Yang <yellowriver2010@...mail.com>,
        Cheng Shengyu <cheng.shengyu@....com.cn>,
        cocci@...teme.lip6.fr, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: Re: [v5] Coccinelle: semantic code search for missing put_device()

>>> +id = of_find_device_by_node@p1(x)
…
>>> +if (id == NULL || ...) { ... return ...; }
>>> +... when != put_device(&id->dev)
>> …
>>> +    when != if (id) { ... put_device(&id->dev) ... }
>> …
>>
>> I would interpret this SmPL code in the way that the if statement
>> for the pointer check is “optional” in this line.
>> Is it an extra and redundant SmPL specification when the reference
>> release function could eventually be found just anywhere within
>> an implementation?
>
> The proposed when code is correct.

I agree that this SmPL code can work in the way it was designed.


> It is not redundant, because it checks for a particular control-flow pattern.

It took another moment until I dared to express a different software
development opinion also on this implementation detail.

Does the first SmPL when specification include the case that a call
of the function “put_device” can occur within a branch of an if statement?

Regards,
Markus