Wrapping classes with pure virtual functions

[gabriel.becedillas at gmail.com]

Hi,
I'm having problems wrapping a hierarchy of classes, actually having
problems wrapping the base class. I don't need to use the WrapClass
mechanism since I don't want to override classes in Python. My code
boils down to:

class Base
{
public:
	virtual ~Base()
	{}

	virtual void f() = 0;
};

class Derived :
	public Base
{
public:
	virtual void f()
	{}

	void g()
	{}
};

int main()
{
	boost::python::class_<Base> class_base("Base");
	boost::python::class_<Derived> class_derived("Derived");
	return 0;
}

The first line inside main (the one exporting Base) is causing the
compile time error:
error C2259: 'Base' : cannot instantiate abstract class...
The probem seems to be that struct value_holder<Base> holds a Base
member instance by value, and this is not possible since Base can't be
instantiated.
I'm using Visual Studio 2005 and boost 1.33.1.
Thanks