boost::shared_ptr and Return Type Resolver idiom

问题

I am currently working on a concept of Object known in Java or C# for C++. It would be similar to variant type like boost::any, however having wider functionality. For that purpose I am using boost::shared_ptr to internaly store actual data and I wanted to provide Return Type Resolver idiom for easily obtaining this data, as it is stored in actual implementation. I know I could use boost::shared_ptr automatic conversion during assigment operator or constructor but as I said shared_ptr is not avaiable at this stage.

Implementing RtR I have encountered a problem with linux platform. For simplicity of code I provide just a simple code which reflects what I want to do basically and what is working under VS2010 and not under GCC. Any comments or solutions woud be appriciate.

struct RtR
{
    template<typename Ptr>
    operator Ptr()
    {
        return Ptr();
    }

    template<typename Ptr>
    operator Ptr() const
    {
        return Ptr();
    }
};

class TestRtR
{
    void test()
    {
        boost::shared_ptr<int> intPtr(new int);
        intPtr = get();
    }

    void test() const
    {
        boost::shared_ptr<const int> intPtr(new int);
        intPtr = get();
    }

    RtR get()
    {
        RtR ret;
        return ret;
    }

    const RtR get() const
    {
        const RtR ret;
        return ret;
    }
};

As I said - if You compile it under VS2010 everything goes ok, but under linux I get:

In member function ‘void TestRtR::test()':
error: ambiguous overload for ‘operator=’ in ‘intPtr = TestRtR::get()’
note: candidates are:
note: boost::shared_ptr<T>& boost::shared_ptr<T>::operator=(const boost::shared_ptr<T>&) [with T = int, boost::shared_ptr<T> = boost::shared_ptr<int>]
note: boost::shared_ptr<T>& boost::shared_ptr<T>::operator=(boost::shared_ptr<T>&&) [with T = int, boost::shared_ptr<T> = boost::shared_ptr<int>]
note: boost::shared_ptr<T>& boost::shared_ptr<T>::operator=(boost::detail::sp_nullptr_t) [with T = int, boost::shared_ptr<T> = boost::shared_ptr<int>, boost::detail::sp_nullptr_t = std::nullptr_t]
In member function ‘void TestRtR::test() const’:
error: ambiguous overload for ‘operator=’ in ‘intPtr = TestRtR::get()’
note: candidates are:
note: boost::shared_ptr<T>& boost::shared_ptr<T>::operator=(const boost::shared_ptr<T>&) [with T = const int, boost::shared_ptr<T> = boost::shared_ptr<const int>]
note: boost::shared_ptr<T>& boost::shared_ptr<T>::operator=(boost::shared_ptr<T>&&) [with T = const int, boost::shared_ptr<T> = boost::shared_ptr<const int>]
note: boost::shared_ptr<T>& boost::shared_ptr<T>::operator=(boost::detail::sp_nullptr_t) [with T = const int, boost::shared_ptr<T> = boost::shared_ptr<const int>, boost::detail::sp_nullptr_t = std::nullptr_t]

Are definitions of boost::shared_ptr different under GCC and VS2010? What is the ground of this ambiguity and how to solve it?

来源：https://stackoverflow.com/questions/16981131/boostshared-ptr-and-return-type-resolver-idiom

标签

c++

boost

shared-ptr

operator-keyword

ambiguity