来自抽象基础的反序列化对于 boost 序列化失败答案

【问题标题】：deserialization from an abstract base fails for boost serialization来自抽象基础的反序列化对于 boost 序列化失败
【发布时间】：2019-08-12 11:42:15
【问题描述】：

我可以使用 boost::serialization 通过抽象基础序列化对象。但是，当我尝试添加反序列化时，会收到关于抽象库的编译错误。这是我的有效序列化代码：

/*
    g++ -Iinclude/ -Llib -lboost_serialization ~/Desktop/ser_ex.cpp -o stest
*/

#include <boost/serialization/serialization.hpp>
#include <boost/serialization/nvp.hpp>
#include <boost/archive/binary_oarchive.hpp>
#include <boost/serialization/vector.hpp>

#include <iostream>
#include <sstream>
#include <string>
#include <vector>
#include <boost/serialization/export.hpp>
#include <boost/serialization/shared_ptr.hpp>
#include <memory>

namespace bser = boost::serialization;
using namespace std;
namespace foo {
class AA
{
public:
    virtual void foo() = 0;
    virtual ~AA() {}
    std::string name;

    template<class Archive>
    void serialize(Archive & ar, unsigned int )
    {
        ar & name;
    }
};
BOOST_SERIALIZATION_ASSUME_ABSTRACT( AA );

class BB : public AA
{
public:
    virtual void foo() = 0;
    virtual void bar() = 0;
    virtual ~BB () {}
    int thing;

    template<class Archive>
    void serialize(Archive & ar, unsigned int )
    {
        ar.template register_type< AA >();
        ar & boost::serialization::base_object<AA>(*this);
        ar & thing;
    }
};
BOOST_SERIALIZATION_ASSUME_ABSTRACT( BB );

class CC : public BB
{
public:
    virtual void foo() {}
    virtual void bar() {}
    virtual ~CC() {}
    int otherThing;

    template<class Archive>
    void serialize(Archive & ar, unsigned int )
    {
        ar.template register_type< BB >();
        ar & boost::serialization::base_object<BB>(*this);
        ar & otherThing;
    }
};
}

BOOST_CLASS_EXPORT_KEY(foo::CC)
BOOST_CLASS_EXPORT_IMPLEMENT(foo::CC)


int main (int , char const **)
{
    std::vector< shared_ptr<foo::AA> > vv;
    vv.push_back( make_shared<foo::CC>() );

    std::ostringstream oss;
    boost::archive::binary_oarchive out_archive( oss );
    out_archive << vv;
    std::cout << oss.str() << std::endl;
}

只需将这一行添加到 binary_oarchive.hpp 的 include 正下方，就会导致代码无法编译。

#include <boost/archive/binary_iarchive.hpp>

dawilcox-macOS:debug dawilcox$ make foo
dependencies: foo_main.o
building: foo_main.o
In file included from /Users/dawilcox/src/axle/foo_main.cpp:5:
In file included from /usr/local/include/boost/serialization/serialization.hpp:43:
/usr/local/include/boost/serialization/access.hpp:130:17: error: allocating an object of abstract class type 'foo::AA'
        ::new(t)T;

Boost 抱怨它无法实例化我的基本类型。这就是重点——它是一个抽象基类型。

反序列化抽象基的正确方法是什么？

【问题讨论】：

我不熟悉这个库，但从概念上讲你不能反序列化一个抽象基。反序列化意味着创建一个抽象类型不可能的实例。您需要反序列化为实际的派生类型。也许您的意思是反序列化派生类型的基本部分，这在反序列化派生类型的上下文中很好。
我不是很肯定，但我在文档中看到了很多注释，您需要将它们反序列化到您序列化的同一类中。文档中还提到了很多抽象类以及一些关于抽象的宏（请参阅上面我使用的宏）。由于这些原因，如果 boost 不支持这一点，我会感到有点惊讶。这有点奇怪。

标签： c++ serialization boost polymorphism deserialization

【解决方案1】：

看起来我错的是我在反序列化函数中注册基类。所以，我摆脱了：

 ar.template register_type< AA >();

改变了

ar.template register_type< BB >();

到

ar.template register_type< CC >();

这是我的完整代码：

/*
    g++ -Iinclude/ -Llib -lboost_serialization ~/Desktop/ser_ex.cpp -o stest
*/

#include <boost/serialization/serialization.hpp>
#include <boost/serialization/nvp.hpp>
#include <boost/archive/binary_oarchive.hpp>
#include <boost/archive/binary_iarchive.hpp>
#include <boost/serialization/vector.hpp>
#include <OMNIMAKE/lib/boost_serialization>

#include <iostream>
#include <sstream>
#include <string>
#include <vector>
#include <boost/serialization/export.hpp>
#include <boost/serialization/shared_ptr.hpp>
#include <memory>

namespace bser = boost::serialization;
using namespace std;
namespace foo {
class AA
{
public:
    virtual void foo() = 0;
    virtual ~AA() {}
    std::string name;

    template<class Archive>
    void serialize(Archive & ar, unsigned int )
    {
        ar & name;
    }
};
BOOST_SERIALIZATION_ASSUME_ABSTRACT( AA );

class BB : public AA
{
public:
    virtual void foo() = 0;
    virtual void bar() = 0;
    virtual ~BB () {}
    int thing;

    template<class Archive>
    void serialize(Archive & ar, unsigned int )
    {
        ar & boost::serialization::base_object<AA>(*this);
        ar & thing;
    }
};
BOOST_SERIALIZATION_ASSUME_ABSTRACT( BB );

class CC : public BB
{
public:
    virtual void foo() {}
    virtual void bar() {}
    virtual ~CC() {}
    int otherThing;

    template<class Archive>
    void serialize(Archive & ar, unsigned int )
    {
        ar.template register_type< CC >();
        ar & boost::serialization::base_object<BB>(*this);
        ar & otherThing;
    }
};
}

BOOST_CLASS_EXPORT_KEY(foo::CC)
BOOST_CLASS_EXPORT_IMPLEMENT(foo::CC)


int main (int , char const **)
{
    std::vector< shared_ptr<foo::AA> > vv;
    vv.push_back( make_shared<foo::CC>() );

    std::ostringstream oss;
    boost::archive::binary_oarchive out_archive( oss );
    out_archive << vv;
    std::cout << oss.str() << std::endl;
}

【讨论】：