Boost C++ Libraries: Ticket #4681: can't serialize protected derived class

attachment set

mark.r.buda@… — Thu, 23 Sep 2010 15:51:49 GMT

attachment → c.cc

demonstration of the problem with serializing protected classes

Robert Ramey — Sat, 25 Sep 2010 17:13:02 GMT

Hmmm, it would be nice if you could share your workaround. Is it something that could be just rolled into export.hpp?

Robert Ramey

mark.r.buda@… — Mon, 27 Sep 2010 15:25:03 GMT

I took BOOST_CLASS_EXPORT_GUID and split it into two macros, removing the namespace bits:

#define BOOST_CLASS_EXPORT_PROTECTED_1(T)                              \
  static ::boost::archive::detail::guid_initializer< T > const         \
  & guid_initializer;                                                  \
#define BOOST_CLASS_EXPORT_PROTECTED_2(W, T, K)                        \
  ::boost::archive::detail::guid_initializer< W::T > const &           \
  W::guid_initializer =                                                \
           ::boost::serialization::singleton<                          \
               ::boost::archive::detail::guid_initializer< W::T >      \
    >::get_mutable_instance().export_guid(K)                           \
/**/
class foo {
  protected:
    class bar {
    // ...
    };
    BOOST_CLASS_EXPORT_PROTECTED_1(foo::bar)
};
BOOST_CLASS_EXPORT_PROTECTED_2(foo, bar, "foo::bar")

mark.r.buda@… — Wed, 29 Sep 2010 16:28:29 GMT

This workaround doesn't, in fact, work around. I don't understand what's going on well enough to make it work.

Robert Ramey — Wed, 29 Sep 2010 16:56:18 GMT

I looked at this a little bit and I don't see any easy fix.

I tried adding another friend to the protected class - but that doesn't work because init_guid is in an anonymous namespace. Of course you CAN work around by either not using a nested class or by making public (which I guess amounts to the same thing). Of course you don't want to do that. For now I'll just leave this open.

Robert Ramey

status changed

Robert Ramey — Sun, 03 Oct 2010 18:10:52 GMT

status new → assigned

status changed; resolution set

Robert Ramey — Sun, 04 Oct 2015 17:53:40 GMT

status assigned → closed
resolution → fixed

Note; recently I've had occasion to look in to this. Turns out that one can serialization private and protected base classes - just not through pointers. I've added a case study to the documentation so explain this. I also investigated what it would take to make this work for pointers and concluded that it's not possible in the current library with current C++. So I'm going to close this item.