提升：：shared_ptr<> "explicit shared_ptr( Y * p ): px( p ), pn() // Y must be complete"

当我试图在boost中以多态方式返回对象时，有人能帮我解决以下错误吗：：smart_ptr:

1>C:Program FilesBoostboost_1_54_0boost/smart_ptr/shared_ptr.hpp(352): error : a value of type "PBO *" cannot be used to initialize an entity of type "O*"
1>        explicit shared_ptr( Y * p ): px( p ), pn() // Y must be complete

这是代码，第一个方法是错误发生的地方是不是因为我缺少了一个复制构造函数或赋值运算符，而boost:：shared_ptr需要定义它们，因此"完成"

CE.cpp

#include "CE.h"
boost::shared_ptr<OB> CE::getObject(){
                                //THIS IS WHERE THE ABOVE ERROR OCCURS
    return boost::shared_ptr<OB>(new PBO);
}

CE.h

#include "E.h"
#include "PBO.h"
#include <boostshared_ptr.hpp>
#include <unordered_map>
class CE: public E{
public:
    virtual boost::shared_ptr<OB> getObject();
private:
};

E.h

#include "OB.h"
#include <boostshared_ptr.hpp>
#include <unordered_map>
class E{
public:
    virtual boost::shared_ptr<OB> getObject() = 0;
private:
};

OB.h

//The parent class in the polymorphic hierarchy:
class OB{
public:
    OB();
    virtual void c(boost::shared_ptr<OD> lo);
    virtual void d(std::unordered_map<double, long> a, std::set<double> b, boost::shared_ptr<OD> o) = 0;
protected:
};

PBO.h

#include "OD.h"
#include "OB.h"
//The child class in the polymorphic hierarchy:
class PBO : public OB{
public:
    PBO();
    virtual void c(boost::shared_ptr<OD> l);
private:
    virtual void d(std::unordered_map<double, long> a, std::set<double> b, boost::shared_ptr<OD> c);
};