[Swig-user] Clean reference counted pointers across C++/Python

[Daniel R. <dr...@gm...>]

I didn't get any response to my previous query, so I'll clarify it.

I would like to have reference counted objects that work across C++  
and Python both for objects which are purely C++ objects and Python  
objects which inherit from C++ base classes. This seems relatively  
easily to implement in SWIG by:
- Purely C++ objects or python objects extending C++ objects which  
don't have virtual functions are just treated like they currently  
are-- their reference count is incremented if there is a python  
reference to them and decremented if there is no python reference. If  
the python proxy object goes away before the C++ object, it is fine.  
The C++ object can't go away without all python references being  
destroyed.
- With Python objects which inherit from C++ objects with virtual  
functions work swig has to keep the python proxy object alive until  
the C++ object is destroyed. This can be done by SWIG keeping a  
reference to the python object until the C++ object is destroyed.  
Then the C++ director can use the call to the virtual C++ destructor  
(which needs  to be there on the C++ side anyway) to remove the  
reference to the python object so that it too goes away.

While it is straight forward, I don't see any way to easily turn on  
or provide this functionality for a large array of classes. I am  
quite new to SWIG so I might be missing something.
Any suggestions or alternatives? Thanks.