De-serialization of enable_shared_from_this through base class pointer fails

[Tim Regan]

Given the following class structure:

Base is a simple class. Derived inherits from Base. Derived also inherits from boost::enable_shared_from_this<Derived>. Base and Derived implement boost::serialization.

When deserializing an instance of Derived into a vector of boost::shared_ptr<Derived>:

Base and Derived members are reconstructed correctly. Derived::shared_from_this() works as expected.

But when deserializing an instance of Derived into a vector of boost::shared_ptr<Base>:

Base and Derived members are still reconstructed correctly. Derived::shared_from_this() throws a bad_weak_ptr exception. This is because enable_shared_from_this::weak_ptr is NOT reconstructed - It is zero.

See test code in attached file that demonstrates both of the above cases.

[t_regan@…]

Test demonstrating enable_shared_from_this deserialization problem

[t_regan@…]

Correction to original description: enable_shared_from_this::weak_this_::px is NOT reconstructed - It is zero.

[t_regan@…]

Workaround: weak_this_ can be reconstructed by calling _internal_accept_owner (which fortunately is public) on each deserialized instance of Derived.

[t_regan@…]

Added test case to demonstrate workaround

[Robert Ramey]

I compiled and ran your example on my machine and have reproduced the problem.

Looking at your example, it seems to me that the serialization function of Derived should be:

	template<class Archive>
	void serialize(Archive & ar, const unsigned int version)
	{
	       ar & BOOST_SERIALIZATION_BASE_OBJECT_NVP(Base);
               ar & boost::serialization::make_nvp(
                     enable_shared_from_this, 
                     boost::serialization::base_object<boost::enable_shared_from_this<Derived> >(*this) 
                )
		ar & BOOST_SERIALIZATION_NVP(m_derived);
         }

Of course this begs the question as to how serialization for boost::enable_shared_from_this<Derived> should be implemented. Of hand I don't remember what boost::enable_shared_from_this<Derived>does right now. ( could guess but I'm not going to waste your time). So my advice is to figure out how to implement serialization for boost::enable_shared_from_this<Derived> and re-submit.

maybe something like the following would work

	template<class Archive>
	void serialize(Archive & ar, const unsigned int version)
	{
              boost_shared_ptr<Derived> m_sp = shared_from_this;
	       ar & BOOST_SERIALIZATION_BASE_OBJECT_NVP(Base);
	       ar & BOOST_SERIALIZATION_NVP(m_sp);
	       ar & BOOST_SERIALIZATION_NVP(m_derived);
         }