[Boost-bugs] [Boost C++ Libraries] #5340: Patch to support concrete base classes becomming abstract classes

Subject: [Boost-bugs] [Boost C++ Libraries] #5340: Patch to support concrete base classes becomming abstract classes
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2011-03-19 00:26:28

#5340: Patch to support concrete base classes becomming abstract classes
---------------------------------------------+------------------------------
 Reporter:  Aaron Barany <akb825@…>          |       Owner:  ramey        
     Type:  Patches                          |      Status:  new          
Milestone:  To Be Determined                 |   Component:  serialization
  Version:  Boost 1.46.0                     |    Severity:  Problem      
 Keywords:  serialization abstract concrete  |  
---------------------------------------------+------------------------------
 If you are serializing a pointer to a polymorphic object as a pointer to
 its base class, and that base class is concrete, it will fail to load if
 that base class later becomes abstract. That is because the serializer for
 the base class is automatically registered if it is concrete, but not if
 it is abstract, making a mismatch in the class id for the object. I have
 attached a patch that detects this case and registers the serializer for
 the abstract class if it occurs.

 This patch contains multiple pieces. Fist, basic_iarchive.cpp is patched
 in load_pointer() to detect that mismatch in class ids and register the
 serializer. Second, iserializer.hpp is patched so that register_type() for
 abstract classes returns the proper pointer serializer. (though it isn't
 directly registered) Third, pointer_iserializer::load_object_pointer() now
 uses templates to split into two implementations: one for abstract and one
 for non-abstract classes. The abstract implementation throws an
 archive_exception, to which an abstract_class_error field has been added.

 This patch does not handle going from an abstract base class to a concrete
 base class, as that would break backwards compatibility. However, it
 should be more common to go from concrete to abstract than the other way
 around, and having this support can solve a lot of debugging headaches
 when it comes up. (headaches that prompted me adding this support)

 I have tried to keep consistent with your coding style and techniques to
 make it as seamless to patch as possible.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/5340>
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