boost serialiaze input stream error

Question

I am working on a simple serialization class. I keep throwing an exception on the input stream. I have put together the below example of what I am attempting to accomplish in simple terms.

I have this simple example of boost serialization that I am getting an 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 that I am getting is:

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

Any help would be appreciated.

Answer 1

You're reading from an empty stream:

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

Also, you leak this object:

base *b1 = new derived();

---

Here's a fixed example, notes:

• it's very good practice/important to close archives before using the streamed data
• BOOST_CLASS_EXPORT_GUID(derived, "derived") doesn't add anything beyond BOOST_CLASS_EXPORT(derived)

• you can print the v2 conditionally:

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

• I've used bla() as an example to print the values instead

• NVP() is a bit iffy there. Why not just leave it out for non-tagged archives (ie. other than XML)? If you intend to support XML, just use BOOST_SERIALIZATION_NVP, boost::serialization::make_nvp etc.

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

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

• the mix of public: and friend in your types didn't really 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