Boost.Python and Polymorphic Behaviour with std::shared_ptr

Question

I would like to know how classes A and B below can work polymorphically in python when using std::shared_ptr instead of boost::shared_ptr ?

struct A
{
    virtual ~A() {}
};

struct B : A
{
    B() {}
    virtual ~B() {}
};

void f(const std::shared_ptr<A>& ptr)
{}

BOOST_PYTHON_MODULE(test)
{
    class_<A, boost::noncopyable>("A", no_init);

    class_<B, std::shared_ptr<B>, bases<A>>("B")
        .def(init<>());

    def("f", f);
}

I am aware that the the boost::get_pointer method must be defined for std::shared_ptr , so I make sure that the following lines exist before a #include <boost/python.hpp> :

namespace boost {
template<class T> const T* get_pointer(const std::shared_ptr<T>& p)
{
    return p.get();
}

template<class T> T* get_pointer(std::shared_ptr<T>& p)
{
    return p.get();
}
} // namespace boost

Now, in python I try:

>>> from test import *
>>> b = B()
>>> f(b)
Traceback (most recent call last):
  File "<console>", line 1, in <module>
ArgumentError: Python argument types in
    test.f(B)
did not match C++ signature:
    f(std::shared_ptr<A>)

Note: The code above works fine for boost::shared_ptr , but I want to stick with the C++11 types instead.

Thanks.

Answer 1

Boost.Python has special magic built in to recognize a boost::shared_ptr. It does not currently recognize a std::shared_ptr. For now, just frown and use boost::shared_ptr.

Answer 2

I made once std::shared_ptr work with boost::python IIRC, using get_pointer as you write. (The relevant comment is here ). My guess is that you need to have class_<A,std::shared_ptr<A>,...> since that is what your function takes as argument.