Re: [Cocci] Challenges around asterisk usage in SmPL code

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

>> @check@
>> expression x;
>> statement es;
>> @@
>> *if ( \( !(x) \| x == NULL \) )
>> *   <+... *(x) ...+>;
>>  else
>>     es
>>
>>
>> Can it be avoided to express assignment variations explicitly?
>
> I don't know what you are trying to do.

Can you get the impression that I am trying also to achieve something
around the detection of null pointer usage?


> Previously, you had the beginning of an assignment before the ...
> I suggested to replace the ... before and after the *(x) by <+... ...+>.

This variant gets accepted by the Coccinelle software.


> Strangely you have deleted the assignment part as well.

I became curious if such an approach should also work.


> Your code line with the <+... ...+> ends with a ;.

Yes - for this test.


> So the <+... ...+> must match an expression (which could be an assignment).

This can be appropriate.


> But due to parsing priorities, <+... ...+> that is unknown is parsed as a statement.
> So the ; causes a parse error.  To force the <+... ...+> to be parsed as
> an expression, you have to surround it with ().  An isomorphism will
> normally cause the case without the parentheses to be considered as well.

Thanks for this explanation.


> None of this has anything to do with unary operators.

This view is reasonable.

I just put a search pattern with an asterisk into this SmPL construct.

Regards,
Markus
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