class BaseCl { some virtual functions };
class DerivedClass : public BaseCl { ... };

BaseCl * b1 = new DerivedClass();
BaseCl * b2 = new "copy of b1"; (just pseudocode)

virtual BaseCl *clone() = 0;

DerivedCl *clone() {return new DerivedCl(*this);}

class BaseCl
{
    virtual BaseCl* clone() {return new BaseC1(*this);}
};
class DerivedClass : public BaseCl
{
    virtual BaseCl* clone() {return new DerivedClass(*this);}
};