[boost] Re: [boost::serialization] - serialization + shared_ptrs

From: Robert Ramey (ramey_at_[hidden])
Date: 2005-04-04 10:47:21

martin.ecker_at_[hidden] wrote:
> also the fact that a special export macro BOOST_SHARED_POINTER_EXPORT
> is needed to export classes used with shared_ptr. It's especially
> cumbersome when shared_ptr is used polymorphically, i.e. we use
> shared_ptr<Base> that actually points to an instance of class Derived.

Note that this should be required ONLY when shared_ptr is used
polymorphically.

> there should be proper, built-in support in boost::serialization for it.

agreed.

> No extra macro or intrusive hack to shared_ptr should be required
> in order to be able to use it.

The macro described above is required to instantiate code not explicitly
referred to.  This occurs with the serialization of derived pointers through
a polymorphic base class.  There are two ways to do this: explicit
registration and export.  Each one has its drawbacks.  The only alternative
that has been suggested is to use the type_info name as a class identifier.
I didn't do this as it would inhibit portability of archives across
compilers and namespaces.

> As was discussed before, a good way to
> achieve this is to use a pointer-to-shared_ptr map in the input
> archive when loading archives that contain shared_ptrs. This is
> actually the approach that we've hacked into the version of
> boost::serialization here at work. We've been using it for a couple of
> months
> now like this and have not experienced any problems with it.

Gee, wouldn't it have been easier just to add a friend to the share_ptr?

>And it also works for serializing weak_ptr.

> However, I would really appreciate an 'official' solution to shared_ptr
(and weak_ptr) serialization.

Me too - but I can't see how this is going to happen

Robert Ramey