Confusion on Virtual function,copy constructor,and type conversion

[Visame]

#include <iostream>
using namespace std;
 
class   A
{
public:
    A() {cout << "constructor A" << endl;}
    A(A& a) {cout<<"copy A"<<endl;}
    virtual   void   Test(){cout <<"A   test" <<endl;}
};
 
class   B:public   A
{
public:
    B() {cout << "constructor B" << endl;}
    B(B& b) {cout<<"copy B"<<endl;}
    void   func(){Test();}
    virtual   void   Test(){cout <<"B   test" <<endl;}
};
 
 
class   C:public   B
{
public:
    C() {cout << "constructor C" << endl;}
    C(C& c) {cout<<"copy C"<<endl;}
    virtual void   Test(){cout <<"C   test" <<endl;}
};
 
 
void   main()
{
    C   c;
    ((B*)(&c))-> func();
    ((B)c).func();
    cout.flush();
 
    int i;
    cin >> i;
}
 
//output is here:
 
constructor A
constructor B
constructor C
C   test
constructor A//Here is my question
copy B
B   test

I can't understand the above output, especially the latter part:
((B)c).func(); gives out the following results:
constructor A//Here is my question
copy B
B test

Please help me.Thanks!

[RRick]

The problem is in line 35.

((B)c).func();

You are telling the compiler to construct an object B from c. This will cause the compiler to make a copy of c using B's copy constructor which will first call the A constructor.

If you want a dynamic cast from C to B without the construction of a new object, you need to convert the pointer (or possibly the reference) to c. The code looks like

((B*)(&c))->func();

.