Robert Ramey schrieb:
Martin Lederhilger wrote:
Hello Robert, hello Bogdan,
I have quite the same problem (Exception multiple_code_instantiation thrown in basic_serializer_map.cpp at line 48) as Bogdan. It can be reproduced by changing the pointer type from polymorphic_base to polymorphic_derived2 in the original test_dll_exported.cpp example, which comes with the library.
void save_exported(const char *testfile) { test_ostream os(testfile, TEST_STREAM_FLAGS); test_oarchive oa(os, TEST_ARCHIVE_FLAGS);
polymorphic_base *rb1 = new polymorphic_derived1; polymorphic_derived2 *rb2 = new polymorphic_derived2;
// export will permit correct serialization // through a pointer to a base class oa << BOOST_SERIALIZATION_NVP(rb1); oa << BOOST_SERIALIZATION_NVP(rb2);
delete rb1; delete rb2; }
I think the problem is that when oa << BOOST_SERIALIZATION_NVP(rb2); is called, that the system registers an type in oserializer.hpp, which leads to creation of the singletons also in the executeable.
Ahhhh - a very useful hint. So the rule would be that if a class is polymorphic is to be serialized through a pointer, it should ONLY be done through a base class pointer? That is, if ALL polymorphic base classes are abstract - this problem will never occur?
I'll have to think about this.
Thanks for your answer, in my case I want to be able to serialize an object with a pointer to its most derived type, a pointer to it's base class, a pointer to the base class of base class, ... Actually this problem should happen with all BOOST_CLASS_EXPORT_IMPLEMENTed classes which reside in one DLL, and are serialized (+automatic register_type) in another DLL or EXE. Is the intention of the exception to prevent useres from using BOOST_CLASS_EXPORT_IMPLEMENT multiple times? If so, then the quick solution for me is to ignore the exception (the serialisation seems to work then, but I know that a solution for the library itself is much trickier). Martin