[C++-sig] A wrapped class contains another wrapped class. Hilarity ensues.

[Matthew Scouten]

I have 2 c++ classes called foo and bar. I wrapped both. bar contains a foo
as a public data member. foo contains a function called get_buffer that is
exported as "__str__" and as the getter of the property 'buffer'

if I construct a foo, I can call that function with no problem.
if I create a bar and try to call the function on its foo I get an error.

My C++ and B::P code:

class foo
{
public:

    foo() {std::strcpy(buffer, "good bye cruel world!\0\0");}
    char buffer[24];
};

struct foo_wrapper : foo , wrapper<foo>
{
        foo_wrapper(const foo& f);
        foo_wrapper();

        //property getters
        std::string get_buffer() const;
};

foo_wrapper::foo_wrapper(const foo& exch): foo(exch), wrapper<foo>(){}

foo_wrapper::foo_wrapper(): foo(), wrapper<foo>(){}

std::string foo_wrapper::get_buffer() const
{
    return std::string(foo::buffer);
}


class bar
{
public:
    foo f;
};

class bar_wrapper: public bar, public wrapper<bar>
{
public:
    bar_wrapper();
    bar_wrapper(const bar &);
};

bar_wrapper::bar_wrapper() : bar(), wrapper<bar>(){}

bar_wrapper::bar_wrapper(const bar &bb ) : bar(bb), wrapper<bar>(){}

BOOST_PYTHON_MODULE(BusyBox)
{

    class_<foo_wrapper>("foo")
        .def(init<>())
        .add_property("buffer", &foo_wrapper::get_buffer)
        .def("__str__", &foo_wrapper::get_buffer)
        ;

    class_<bar_wrapper>("bar")
        .def_readwrite("f", &bar::f)
        ;
}

A REPL session that demos the errors:>>> from BusyBox import *
>>> f1 = foo()
>>>
>>> f1.buffer
'good bye cruel world!'
>>> str(f1)
'good bye cruel world!'
>>>
>>> b1 = bar()
>>>
>>> b1.f.buffer #Generates error
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
Boost.Python.ArgumentError: Python argument types in
    None.None(foo)
did not match C++ signature:
    None(struct foo_wrapper {lvalue})
>>> str(b1.f)   #Generates error
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
Boost.Python.ArgumentError: Python argument types in
    foo.__str__(foo)
did not match C++ signature:
    __str__(struct foo_wrapper {lvalue})
>>>
>>> f2 = b1.f
>>>
>>> b2.buffer   #Generates error
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'b2' is not defined
>>> str(f2)     #Generates error
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
Boost.Python.ArgumentError: Python argument types in
    foo.__str__(foo)
did not match C++ signature:
    __str__(struct foo_wrapper {lvalue})
>>>

I feel like I must be doing something stupid. What is wrong?
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