Re: [pygccxml-development] Parameter passing, ownership semantics

[Gustavo C. <gjc...@gm...>]

On 2/19/07, Roman Yakovenko <rom...@gm...> wrote:
>
> Hi. Unfortunately I reproduced the error and was not able to  fix it
> :-(((((.


  Hey, thanks a lot anyway; it is now a problem in boost, but you solved the
Py++ part of the problem with commendable speed.

There is something I don't understand  and I think  this is  Boost.Pythonbug.
>
> I do made some progress.
>
> 1. When you derive Python class from a C++ one you have to define __init__
>
>     method, otherwise your code will not work:


  Since when does a subclass have to define __init__ in order to get the
parent class __init__ called?  What you say goes against all my python
knowledge...

class MyEvent(EventImpl):
>     def __init__( self ):
>         EventImpl.__init__( self )
>
>     def Notify(self):
>         print "Notify!"
>
> 2. I did small research for you. Read this post:
>    http://aspn.activestate.com/ASPN/Mail/Message/cpp-sig/1331901
>    and take a look on Boost.Python unit tests:
>
> http://boost.cvs.sourceforge.net/boost/boost/libs/python/test/auto_ptr.cpp?view=markup
>
> http://boost.cvs.sourceforge.net/boost/boost/libs/python/test/auto_ptr.py?view=markup
>
> What I found is:
> The ownership is really transfered. You can check this using simple
> technique:



        Add new function to EventImpl:
>           virtual std::string class_name() const { return "EventImpl"; }
>         Add free function:
>            std::string get_class_name( const std::auto_ptr<EventImpl>& e
> ){
>                if( e.get() ){
>                    return e->class_name();
>                }
>                else{
>                   return "no object";
>                }
>            }
>         You will get the answer "no object", after "Schedule" call.
> So, may be you don't have to delete the Python object.


  I can't help it;  I can't prevent the programmer  from deleting the object
prematurely; it's out of my control.

I will submit the bug to the Boost.Python mailing list, hope somebody will
> be able to help.


   Thanks, I will subscribe to that list too.

-- 
Gustavo J. A. M. Carneiro
"The universe is always one step beyond logic."