Increase serialization error

I came across this post while trying to use boost :: serialization. However, I am not doing it wrong. Could you point this out?

Thank,

Error message:

    boost/include/boost/archive/detail/check.hpp:162: error: invalid application of 'sizeof' to incomplete type 'boost::STATIC_ASSERTION_FAILURE<false>'

      

        
        
        
      

    

Below is my code:

    template<class Archive>
    void nDB::serialize(Archive &ar, const unsigned int version) {
    boost::unordered_map<string,macro*,myhash,cmp_str>::const_iterator M_IT;
    boost::unordered_map<string,layer*,myhash,cmp_str>::const_iterator L_IT;
    for (M_IT = _MACROS.begin();M_IT != _MACROS.end();M_IT++) {
     ar & M_IT->first;
     ar & *(M_IT->second);

    } 
    for (L_IT = _LAYERS.begin();L_IT != _LAYERS.end();L_IT++) {
      ar & L_IT->first;
      ar & *(L_IT->second);
    }
    }