c++ - boost serialiaze input stream error -

i working on simple serialization class. keep throwing exception on input stream. have put below example of attempting accomplish in simple terms.

i have simple example of boost serialization getting exception on:

#include <boost/serialization/serialization.hpp>  #include <boost/archive/text_oarchive.hpp>  #include <boost/archive/text_iarchive.hpp>  #include <boost/serialization/export.hpp>  #define nvp(x) x   class base {  public:  friend class boost::serialization::access;  base (){ v1 = 10;}  int v1;  template<class archive>  void serialize(archive & ar, const unsigned int file_version)  {       ar & nvp(v1);  }  virtual void bla()=0;  };    class derived : public base {  public:  friend class boost::serialization::access;  int v2 ;  derived() { v2 = 100;}  template<class archive>  void serialize(archive & ar, const unsigned int file_version){      boost::serialization::base_object<base>(* this);      ar & nvp(v2);  }   virtual void bla(){}; }; boost_class_export(base); boost_class_export_guid(derived, "derived");  int main ( ) { std::stringstream ss; boost::archive::text_oarchive ar(ss); base *b = new derived(); ar << nvp(b); std::cout << ss.str()<<std::endl;    std::istringstream ssi; base *b1 = new derived(); { boost::archive::text_iarchive ar1(ssi); ar1 >> b1; } //std::cout << ssi.str(); std::cout << "v1: " << b1->v1 << std::endl;  } 

the exception getting is:

terminate called after throwing instance of 'boost::archive::archive_exception'   what():  input stream error 

any appreciated.

you're reading empty stream:

std::istringstream ssi; // ... boost::archive::text_iarchive ar1(ssi); 

also, leak object:

base *b1 = new derived(); 

---

here's fixed example, notes:

• it's practice/important close archives before using streamed data
• boost_class_export_guid(derived, "derived") doesn't add beyond boost_class_export(derived)

• you can print v2 conditionally:

  if (auto* d = dynamic_cast<derived*>(b1))     std::cout << "v2: " << d->v2 << std::endl; 

• i've used bla() example print values instead

• nvp() bit iffy there. why not leave out non-tagged archives (ie. other xml)? if intend support xml, use boost_serialization_nvp, boost::serialization::make_nvp etc.

• std::cout << "v2: " << b1->v2 << std::endl; out of place

• just initialize b1 null don't leak it; remember free pointers (use smart pointers!)

• the mix of public: , friend in types didn't mean much

live on coliru

#include <boost/serialization/serialization.hpp> #include <boost/archive/text_oarchive.hpp> #include <boost/archive/text_iarchive.hpp> #include <boost/serialization/export.hpp> #include <sstream>  class base {   public:     base(int v1) : v1(v1) {}     virtual void bla() const = 0;    private:     friend class boost::serialization::access;      template <class archive> void serialize(archive &ar, unsigned /*int const file_version*/) {         ar & boost_serialization_nvp(v1);     }   protected:     int v1; };  class derived : public base {   public:     derived(int v1 = 10, int v2 = 100) : base(v1), v2(v2) {}     virtual void bla() const {         std::cout << "v1: " << v1 << ", v2: " << v2 << "\n";     }    private:     friend class boost::serialization::access;     int v2;     template <class archive> void serialize(archive &ar, unsigned /*int const file_version*/) {         boost::serialization::base_object<base>(*this);         ar & boost_serialization_nvp(v2);     } };  boost_class_export(base) boost_class_export(derived)  int main() {     std::stringstream ss;     {         boost::archive::text_oarchive ar(ss);         base *b = new derived();         ar << boost::serialization::make_nvp("base", b);          delete b; // todo use raii instead     }      std::cout << ss.str() << std::endl;     base *deserialized = nullptr;     {         boost::archive::text_iarchive ar1(ss);         ar1 >> boost::serialization::make_nvp("base", deserialized);     }      deserialized->bla();     delete deserialized; } 

prints

22 serialization::archive 12 0 7 derived 1 0 0 100  v1: 10, v2: 100