Boost C++ Libraries: Ticket #7474: compilation error in boost::serialization

status changed; resolution set

Robert Ramey — Sun, 21 Oct 2012 16:53:46 GMT

status new → closed
resolution → invalid

I'm guessing that the client code does something like

myclass x;

text_oarchive oa(...

oa << x; error - x must be const !!!

There is a long explanation in the rationale section of the manual which explains why this is so.

Of course, without the rest of the program I can't verify whether my presumption is right or wrong about this. But for now, I'm going to assume I'm corrected and close this ticket.

Robert Ramey

status changed; resolution deleted

Mon, 22 Oct 2012 20:30:27 GMT

status closed → reopened
resolution invalid

Hi, I report this bug as it can be produced in below code --- where it doesn't matter if we use "const" Class in the client code or not. Thanks, -Like

//============================================================================
// Name        : boost_bug.cpp
// Author      :
// Version     :
// Copyright   : Your copyright notice
//============================================================================
#include <iostream>
#include <tr1/memory>
#include <fstream>
#include <iostream>
#include <iostream>
#include <boost/archive/text_oarchive.hpp>
class MyClassA
{
public:
	MyClassA(int x):xx(x){};
	int xx;
private:
	friend class boost::serialization::access;
	template<class Archive>
	void save(Archive & ar, const unsigned int version) {
		//ar << xx;
	}
	template<class Archive>
	void load(Archive & ar, const unsigned int version) {
		//ar >> xx;
	}
	BOOST_SERIALIZATION_SPLIT_MEMBER();
};
int main() {
	 MyClassA clsA(12);
	std::ofstream f("/tmp/boost_clsA", std::ios::binary);
	if (f.fail()) return -1;
	boost::archive::text_oarchive oa(f);
	oa << clsA;
	f.close();
	return 0;
}

status changed; resolution set

Robert Ramey — Mon, 22 Oct 2012 21:00:09 GMT

status reopened → closed
resolution → invalid

int main() {
	const MyClassA clsA(12); // error - should be "const"
	std::ofstream f("/tmp/boost_clsA", std::ios::binary);
	if (f.fail()) return -1;
	boost::archive::text_oarchive oa(f);
	oa << clsA;
	f.close();
	return 0;
}

Exactly as I expected. For this to compile you have to have the "const".

The reason for this is explained in the Rationale section in the documentation. Please read it.

Robert Ramey

status changed; resolution deleted

Tue, 23 Oct 2012 20:08:49 GMT

status closed → reopened
resolution invalid

I have to report this again. Changing to const form also gave the exact same error:

const MyClassA clsA(12); // error - should be "const"

Please try this example with const form. I don't know if this work with VC but gcc always gave error even the const form.

As in my first post, the issue appears due to the one line change in /opt/local/include/boost/serialization/access.hpp:

    // pass calls to users's class implementation
    template<class Archive, class T>
    static void member_save(
        Archive & ar,
        //const T & t,   // change to below
        T & t,
        const unsigned int file_version
    ){
        t.save(ar, file_version);
    }

status changed; resolution set

Robert Ramey — Wed, 19 Feb 2014 19:33:40 GMT

status reopened → closed
resolution → invalid

The following compiles for me w/o problem.

Note that I made one change - I added "const" to the save member function.

//============================================================================
// Name        : boost_bug.cpp
// Author      :
// Version     :
// Copyright   : Your copyright notice
//============================================================================
#include <iostream>
#include <fstream>
#include <iostream>
#include <iostream>
#include <boost/archive/text_oarchive.hpp>
class MyClassA
{
public:
	MyClassA(int x):xx(x){};
	int xx;
private:
	friend class boost::serialization::access;
	template<class Archive>
	void save(Archive & ar, const unsigned int version) const {
		//ar << xx;
	}
	template<class Archive>
	void load(Archive & ar, const unsigned int version) {
		//ar >> xx;
	}
	BOOST_SERIALIZATION_SPLIT_MEMBER();
};
int main() {
	 MyClassA clsA(12);
	std::ofstream f("/tmp/boost_clsA", std::ios::binary);
	if (f.fail()) return -1;
	boost::archive::text_oarchive oa(f);
	oa << clsA;
	f.close();
	return 0;
}