Re: [Boost-users] Subject : [Serialization] linker problem, serialization method cannot be found.

8 Aug 2007

      You need to explicitly instantiate the code,  see below

Robert Ramey

"Oliver Kania" <kania.oliver@googlemail.com> wrote in message news:1262c4ee0708080648w1f58627ercaffa141de529bb8@mail.gmail.com...
  Hello and thanks for the help I received so far.
  here is my current problem:

  The class I try to serialize is:

  class LIBPALO_NG_CLASS_EXPORT CubeCache : public CUBE_INFO { 
          public:
              friend class boost::serialization::access; 
              CubeCache();
              ~CubeCache();

              void setSequenceNumber( unsigned int sequenceNumber ) {
                  m_SequenceNumber = sequenceNumber; 
              }

              unsigned int getSequenceNumber() const { 
                  return m_SequenceNumber;
              }

          private:
              unsigned int m_SequenceNumber;
              template<class Archive>
              void serialize( Archive &ar, const unsigned int version ); 

          };

  the cpp file looks as follows:

  #include "CubeCache.h"
  #include <boost/serialization/base_object.hpp>
  namespace jedox {
      namespace palo                 /* palo */
      {
          template<class Archive>
          void CubeCache::serialize( Archive &ar, const unsigned int version ) { 
              // save/load base class information
              ar & boost::serialization::base_object<CUBE_INFO>( *this ); 
              ar & m_SequenceNumber;
          }

          CubeCache::CubeCache(){;}
          CubeCache::~CubeCache(){;}
      }
  }                                 /* jedox */ 

  The CUBE_INFO structure serializes just fine. There are no linkage problems with the following code:

  int main( int argc, char* argv[] ) { 
        CUBE_iNFO* const c = new CUBE_INFO();
      std::ofstream ofs("filename"); 
      // save data to archive
      {
          boost::archive::text_oarchive oa( ofs );
          // write class instance to archive
          oa << ( c );
          // archive and stream closed when destructors are called
      }
      return 0;
  }

  //////////////////// add this here - explicite instantiation
  template CubeCache::serialize<boost::archive::text_oarchive>;

  However, when I use CubeCache instead of CUBE_INFO in the above code, i get a linkage error:
  ======================================================================
  libpalo_ng.obj : error LNK2019: unresolved external symbol "private: void __thiscall jedox::palo::CubeCache::serialize<class boost::archive::text_oarchive>(class boost::archive::text_oarchive &,unsigned int)"  ... 
  ======================================================================

  There are no linkage problems with the library when i do not use boost::serialization. I guess this happens
  when the linker tries to link with the serialization library. LIBPALO_NG_CLASS_EXPORT is defined as: 
  #   define LIBPALO_NG_CLASS_EXPORT __declspec(dllexport)
  Regards, Oliver

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