Dear Robert thank you for answering.

...

class A class B : public A class C : public virtual B class D : public virtual B class E : public C, public D

so, a classic diamond inheritance which the serialization lib is supposed to be able to tackle with. Now, if I have a piece of code like this

boost::serialization::xml_oarchive oa(somestream); A *a = new E(); oa << BOOST_SERIALIZATION_NVP(a);

it throws exception at the aforementioned line. Examining the template substitutions, template class T is substituted with const B* and template class U is substituted with const A. So, the program should do a downcast on a const A* to const B* which is ought to be possible.

Your example does indicate whether A has any pure virtual functions or not. The dynamic down cast will only function if A is polymorphic - that is has at least one virtual function. Soooo, I would expect this work if A has at least one virtual function and I would expect it to fail if has no virtual function. Double check this and get back to us.

Yes, A does have a virtual destructor. But originally A had more virtual member functions, I just trimmed them down when I wanted to locate the source of error. But yes, class A is still polymorphic. I try to attach the example code to this mail, I hope it will get through. Best regards Zoltan