Re: [cocci] Searching for lock calls without unlocking (with SmPL)?

[Markus Elfring <Markus.Elfring@web.de>]

Am 02.08.25 um 19:38 schrieb Julia Lawall:
> 
> 
> On Sat, 2 Aug 2025, Markus Elfring wrote:
> 
>>>>>>>      The one in the if is matching with the call closest to it,
>>>>>>
>>>>>> I interpret this hit as a false positive.
>>>>>> (The first lock call in the if branch is not the relevant companion call
>>>>>> from the function implementation.)
>>>>>>
>>>>>>
>>>>>>>                                                                 not the
>>>>>>> call at the beginning of the function.
>>>>>>
>>>>>> This is an essential requirement for the discussed source code search pattern,
>>>>>> isn't it?
>>>>>
>>>>> No.
>>>>
>>>> I hope still that a better common understanding can be achieved.
>>>>
>>>>
>>>>>      I don't understand why you think that.
>>>>
>>>> The source code search pattern tries to find a pair of lock calls.
>>>> Is the passed expression determined for the metavariable “y” after the second
>>>> lock call was found at the beginning of the function implementation?
>>>
>>> I don't understand this at all.
>>
>> Does this feedback indicate another communication problem?
>>
>>
>>>                                  Coccinelle doesn't care about the
>>> beginning of the function, unless you start the pattern with a function
>>> header or a ...
>>
>> Where does the statement “action_lock(&blockage1);” appear in the implementation
>> of the function “my_action_test”?
> 
> It is at the beginning of the function.

Thanks for another bit of positive feedback.


>                                          But that the fact that x matches
> &blockage1 n one place doesn't mean that it can't match something else
> when checking for a match at another place in the code.

This technical aspect can be usable for further source code search approaches.


>                                                          If you hava a
> function like
> 
> int f() {
>   a(1);
>   a(2);
>   a(3);
> }
> 
> and your semantic patch is:
> 
> @@
> expression x;
> @@
> 
> * a(x);
> 
> Then all calls to a will be marked, because the pattern can march in three
> different places, with three different bindings of x.

It seems that this software behaviour (according to the functionality “semantic match”)
was not officially documented so far.
https://gitlab.inria.fr/coccinelle/coccinelle/-/blob/3aa9a6ab3b035e31292be31399b99a8857480aef/docs/manual/cocci_syntax.tex#L1214-1225

Would it be cleaner to use the SmPL construct “<+... … ...+>” accordingly?


>> Would it be possible to determine that special control flow from an if branch
>> would be inappropriate according to the mentioned SmPL code?
> 
> If you don't want a match to go over an if,

There are further constraints to consider.


>                                             you have to add the if to the
> pattern to specify that.

I do not like this suggestion.

It should be possible in a simpler way to point source code places out
which start with a selected function call combination.

Regards,
Markus