Workaround for incorrect `use_count()`s with `shared_ptr_converter`. To be integrated in Oberon00/luabind.

shared_ptr_converter.hpp

// Copyright Daniel Wallin 2009. Use, modification and distribution is
// subject to the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

#ifndef LUABIND_SHARED_PTR_CONVERTER_090211_HPP
# define LUABIND_SHARED_PTR_CONVERTER_090211_HPP

# include <luabind/detail/decorate_type.hpp>  // for LUABIND_DECORATE_TYPE
# include <luabind/detail/policy.hpp>    // for default_converter, etc
# include <luabind/detail/yes_no.hpp>
# include <luabind/get_main_thread.hpp>  // for get_main_thread
# include <luabind/handle.hpp>           // for handle

# include <boost/mpl/bool.hpp>           // for bool_, false_
# include <boost/smart_ptr/shared_ptr.hpp>  // for shared_ptr, get_deleter

namespace luabind {

namespace detail
{

  struct shared_ptr_deleter
  {
      shared_ptr_deleter(lua_State* L, int index)
        : life_support(get_main_thread(L), L, index)
      {}

      void operator()(void const*)
      {
          handle().swap(life_support);
      }

      handle life_support;
  };

  // From http://stackoverflow.com/a/1007175/2128694
  // (by Johannes Schaub - litb, "based on a brilliant idea of someone on
  // usenet")
  template <typename T>
  struct has_shared_from_this_aux
  { 
  private:
      struct fallback { int shared_from_this; }; // introduce member name
      struct derived : T, fallback
      {
          derived(); // not implemented; silence MSVC warnings C4510 and C4610
      };

      template<typename C, C> struct check; 

      template<typename C> static no_t f(
          check<int fallback::*, &C::shared_from_this>*); 
      template<typename C> static yes_t f(...); 

  public:
      BOOST_STATIC_CONSTANT(bool, value =
          sizeof(f<derived>(0)) == sizeof(yes_t));
    };

  template <typename T>
  struct has_shared_from_this:
      boost::mpl::bool_<has_shared_from_this_aux<T>::value>
  {};

} // namespace detail

template <class T>
struct default_converter<boost::shared_ptr<T> >
  : default_converter<T*>
{
private:
    typedef boost::shared_ptr<T> ptr_t;
    detail::value_converter m_val_cv;
    int m_val_score;

    // no shared_from_this() available
    ptr_t shared_from_raw(T* raw, lua_State* L, int index, boost::mpl::false_)
    {
        return boost::shared_ptr<T>(
            raw, detail::shared_ptr_deleter(L, index));
    }

    // shared_from_this() available.
    ptr_t shared_from_raw(T* raw, lua_State*, int, boost::mpl::true_)
    {
        return raw->shared_from_this();
    }

public:
    default_converter(): m_val_score(-1) {}

    typedef boost::mpl::false_ is_native;

    template <class U>
    int match(lua_State* L, U, int index)
    {
        // Check if the value on the stack is a holder with exactly ptr_t
        // as pointer type.
        m_val_score = m_val_cv.match(L, LUABIND_DECORATE_TYPE(ptr_t), index);
        if (m_val_score >= 0)
            return m_val_score;

        // Fall back to raw_ptr.
        return default_converter<T*>::match(
            L, LUABIND_DECORATE_TYPE(T*), index);
    }

    template <class U>
    boost::shared_ptr<T> apply(lua_State* L, U, int index)
    {
        // First, check if we got away without upcasting.
        if (m_val_score >= 0)
        {
            ptr_t ptr = m_val_cv.apply(
                L, LUABIND_DECORATE_TYPE(ptr_t), index);
            return ptr;
        }

        // If not obtain, a raw pointer and construct are shared one from it.
        T* raw_ptr = default_converter<T*>::apply(
            L, LUABIND_DECORATE_TYPE(T*), index);
        if (!raw_ptr)
            return boost::shared_ptr<T>();

        return shared_from_raw(
            raw_ptr, L, index, detail::has_shared_from_this<T>());
    }

    void apply(lua_State* L, boost::shared_ptr<T> const& p)
    {
        if (detail::shared_ptr_deleter* d =
                boost::get_deleter<detail::shared_ptr_deleter>(p))
        {
            d->life_support.push(L);
        }
        else
        {
            detail::value_converter().apply(L, p);
        }
    }

    template <class U>
    void converter_postcall(lua_State*, U const&, int)
    {}
};

template <class T>
struct default_converter<boost::shared_ptr<T> const&>
  : default_converter<boost::shared_ptr<T> >
{};

#ifdef BOOST_HAS_RVALUE_REFS
template <class T>
struct default_converter<boost::shared_ptr<T>&&>
  : default_converter<boost::shared_ptr<T> >
{};
#endif

} // namespace luabind

#endif // LUABIND_SHARED_PTR_CONVERTER_090211_HPP