linux-kernel - Re: [3/3] Coccinelle: pci_free_consistent: Extend when constraints for two SmPL ellipses

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Message-ID: <86e6bf17-966b-06fe-287a-3df7e35736cb@web.de>
Date:   Wed, 15 May 2019 13:18:29 +0200
From:   Markus Elfring <Markus.Elfring@....de>
To:     Julia Lawall <julia.lawall@...6.fr>
Cc:     Coccinelle <cocci@...teme.lip6.fr>,
        LKML <linux-kernel@...r.kernel.org>,
        Cheng Shengyu <cheng.shengyu@....com.cn>,
        Gilles Muller <Gilles.Muller@...6.fr>,
        Ma Jiang <ma.jiang@....com.cn>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Michal Marek <michal.lkml@...kovi.net>,
        Nicolas Palix <nicolas.palix@...g.fr>,
        Wen Yang <wen.yang99@....com.cn>,
        Yi Wang <wang.yi59@....com.cn>
Subject: Re: [3/3] Coccinelle: pci_free_consistent: Extend when constraints
 for two SmPL ellipses



Am 15.05.19 um 12:19 schrieb Julia Lawall:
>
>
> On Wed, 15 May 2019, Markus Elfring wrote:
>
>>>>> On the other hand, I do care about causing false negatives.
>>>>
>>>> Do you find the missing warning after the addition of such an exclusion
>>>> specification interesting?
>>>
>>> I already suggested how to improve the code.
>>
>> I find that the idea “e2->fld” needs further clarification.
>> Such a SmPL specification will be resolved also to an expression,
>> won't it?
>
> Saving in a local variable doesn't impact the need to free the object.

I suggest to reconsider this view.

Would we like to introduce additional case distinctions for the handling
of reassignments to local variables (as shown in Wen's test case)?


> A field is the most obvious case where the object may not need freeing.

A corresponding resource release should probably be performed by
an other function then.


> But there are many expressions that e2->fld will not match.

Data structure members can eventually belong also to a local variable.
Would they become relevant for further SmPL exclusion specifications?

Regards,
Markus