[boost] shared_ptr inheritance query

From: Dave Handley (dave_at_[hidden])
Date: 2005-01-30 19:06:46

I wonder if anyone could help me with a particular problem I'm having with 
shared_ptr.  I'm working on a policy template, and I want the policy 
template to both privately inherit, and inject enable_shared_from_this - but 
the 2 things seem to be mutually exclusive.  Let me give you an idea of what 
I'm trying to do (with some gross simplification to make the code a little 
simpler):

template <class T>
class policy : public enable_shared_from_this<T>
{
};

template <class T>
class base : private policy<T>
{
public:
    shared_ptr<T> get_ptr() { return shared_from_this(); }
};

class MyClass : public base<MyClass>
{
};

test()
{
    shared_ptr<MyClass> obj( new MyClass );
    shared_ptr<MyClass> obj1 = obj->get_ptr();
}

If you run this you get a "conversion from MyClass* to 
boost::enable_shared_from_this<T> * exists, but is inaccessible" error (on 
VC++7.1).  The same is true with protected inheritance.  Is there any way 
around this?

Thanks

Dave Handley