linux-kernel - Re: [PATCH] coccinelle: tests: unsigned value cannot be lesser than zero

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Date:	Wed, 16 Sep 2015 11:11:45 +0200
From:	Andrzej Hajda <a.hajda@...sung.com>
To:	Julia Lawall <julia.lawall@...6.fr>
Cc:	SF Markus Elfring <elfring@...rs.sourceforge.net>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	Gilles Muller <Gilles.Muller@...6.fr>,
	Joe Perches <joe@...ches.com>,
	Nicolas Palix <nicolas.palix@...g.fr>,
	Michal Marek <mmarek@...e.com>, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org, cocci@...teme.lip6.fr
Subject: Re: [PATCH] coccinelle: tests: unsigned value cannot be lesser than
 zero

On 09/15/2015 03:57 PM, Julia Lawall wrote:
> 
> 
> On Tue, 15 Sep 2015, Andrzej Hajda wrote:
> 
>> On 09/15/2015 03:31 PM, Julia Lawall wrote:
>>> On Tue, 15 Sep 2015, SF Markus Elfring wrote:
>>>
>>>>>>  v@p
>>>>>> (
>>>>>> *< 0
>>>>>> |
>>>>>> *<= 0
>>>>>> )
>>>>> It does not, and is not intended to, work.  The branches of a disjunction
>>>>> should be complete expressions.
>>>> Will the following SmPL approach be more appropriate then?
>>>>
>>>> (
>>>> *v@p < 0
>>>> |
>>>> *v@p <= 0
>>>> )
>>> Actually, all of
>>>
>>> v < 0 (never true)
>>> v <= 0 (same as v == 0)
>>> v >= 0 (always true)
>>>
>>> would seem to merit attention.  Andrzej, what do you think?
>>
>> You are right, the 2nd case should be also addressed,
>> such code is misleading.
>> I will prepare then 2nd version of the patch.
> 
> It could be reasonable to change the options to --all-includes?  Although
> it could be somewhat slow.

I have tested the patch with 'v <= 0', it spotted hundreds places with this
check. It seems to be quite common practice to use such checks with counters,
iterators, quantities, range checking. In fact it is negation of 'v > 0' which
seems to be acceptable even if it really means 'v != 0'. So maybe we should not
warn about it? What do you think?

On the other side it spotted also real bugs, but maybe I can make separate, more
specific test for such cases.

Regards
Andrzej

> 
> julia
> 
>>
>> Regards
>> Andrzej
>>
>>>
>>> julia
>>>
>>>
>>>> Regards,
>>>> Markus
>>>> --
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>>>>
>>
>>
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