Hi Robert, all, In some of our libs, we use serialization through a base pointer: We have a base (abstract) class "a::base" which is available from a shared library "liba". We have created a new class "b::foo", inherited from "a::base", hosted in another shared lib "libb", "libb" being explicitly linked to "liba". In "libb", class "b::foo" is exported through : BOOST_CLASS_EXPORT_KEY2(b::foo,"b::foo") (in header foo.hpp) BOOST_CLASS_EXPORT_IMPLEMENT(b::foo) (in some libb's foo-serial.cpp source file) which I think is the right way to process to register a class in a compilation unit. In a test program, I (de)serialize 'b::foo' instances through a 'a::base' pointer. This mechanism has worked for years in all of our software chains. And today it works with our current production software system (ubuntu linux 16.04, g++ 5.4.0, GNU ld 2.26.1, Boost 1.60). However, we now face a runtime error on *some* of our boxes. The message is: <pre> ...test_app...: /path/to/boost/install/include/boost/archive/detail/oserializer.hpp:436: static void boost::archive::detail::save_pointer_type<Archive>::polymorphic::save(Archive&, T&) [ with T = a::base; Archive = boost::archive::xml_oarchive]: Assertion `__null != bpos' failed. Abort (core dumped) </pre> This error only occurs with XML or txt archives, but works like a charm with Christian's EOS portable binary ars. What is strange is that the code works on some of our systems but failed on other ones with the same compiler/linker/boost versions. The exception suggests some problem with class registration but I don't understand this (apparently) arbitrary behaviour. If any of you have a hint to help us to find the solution, it would be appreciated. thanks regards -- François