Christoph Heindl wrote:
#include <boost/archive/xml_iarchive.hpp> #include <boost/archive/polymorphic_iarchive.hpp> #include <boost/archive/polymorphic_oarchive.hpp> #include <boost/serialization/export.hpp> #include "demo_polymorphic_A.hpp" BOOST_CLASS_EXPORT(A);
the compiler breaks with "cannot convert parameter 1 from 'boost::archive::xml_iarchive' to 'boost::archive::polymorphic_iarchive &" in 'boost/serialization/access.hpp'
I took this example and indeed it failed to compile. It took me quite a while to discover the cause. demo_polymorphic_A.hpp includes class A { ... void serialization(boost::archive::polymorphic_iarchive &ar, const unsigned version); ... }; When BOOST_CLASS_EXPORT(A) is encountered, it attempts to "register" All the archives included. This means xml_iarchive with the type A. But class A includes declaration only for polymorphic_iarchive. So during the "register" process, it tries to convert a reference to xml_iarchive to a reference to polymorphic_iarchive - which fails with a compile time error. So the appropriate fix is not to include xml_iarchive - (maybe to enforce the usage of polymorphic archives all the time- or whatever reason) or use replace the serialize above with: ttemplate<class Archive> void serialize(Archive & ar, const unsigned int version); This WILL compile without problem. However it will fail to link as the serialization function will not have been instantiated with xml_iarchive. This can be addressed by altering demo_polymorphic_A.cpp to look like the following: #include <boost/archive/polymorphic_iarchive.hpp> #include <boost/archive/polymorphic_oarchive.hpp> #include "demo_polymorphic_A.hpp" // explicitly instantiate templates for polymorphic archives // used by this demo. template void A::serialize<boost::archive::polymorphic_iarchive>( boost::archive::polymorphic_iarchive &, const unsigned int ); template void A::serialize<boost::archive::polymorphic_oarchive>( boost::archive::polymorphic_oarchive &, const unsigned int ); This will compiler and link as expected. Perhaps this explanation will help with your own application. At the bottom of its is the EXPORT(A) requires that templates or declarations exist which match all archive classes included. Robert Ramey