test virtual

virtual_test.cpp

#include <iostream>

using namespace std;

struct A1
{
    virtual void Test() = 0;
    virtual ~A1()
    {
        std::cout << "~A1\n";
    }
};

struct A2
{
    A1* const m_a1;
    
    A2(A1* a1) : m_a1(a1) {}
    bool IsTest() const { return true; }
    virtual ~A2()
    {
        std::cout << "~A2\n";
        if (m_a1 && IsTest())
        {
            m_a1->Test();
        }
    }
};

struct B1 
  : public A2
  , private A1
{
    B1() : A2(this) {}
    void Test() override
    {
        std::cout << "B1::Test\n";
    }
};

int main()
{
   A2* b1 = new B1();
   delete b1;

   return 0;
}