请问在main函数中用户自定义类的默认构造函数总共被调用了几次？

Question

请问在main函数中用户自定义类的默认构造函数总共被调用了几次？

#include <iostream>
using namespace std

class Animal {
public:
    Animal() { }
    virtual void eat()
    {
        cout << "Animal" << "eat" << endl
    }
}

class Mammal : public virtual Animal {
public:
    Mammal() {}
    virtual void breathe()
    {}
    virtual void eat()
    {
        cout << "Mammal" << "eat" << endl
    }
}

class WingedAnimal : public virtual  Animal {
public:
    WingedAnimal() { }
    virtual void flap()
    {}
    virtual void eat()
    {
        cout << "WingedAnimal" << "eat" << endl
    }
}
class Bat : public Mammal, public WingedAnimal
{
public:
    Bat() { }

    virtual void eat()
    {
        cout<<"Bat"<<" eat"<<endl
    }
}
int main()
{
    Bat b
    WingedAnimal bb
    Animal &a = b

    Animal &aa = bb
    aa.eat()

    return 0
}