复制 ctor 在下面被调用了多少次？

Question

In the book I read this question, the answer was 8 times .

• How?
• Please explain me. :)

---

Temp fun1(Temp x)
{
Temp y(x);
Temp z=y;
return z;
}
void main()
{
Temp a;
Temp b=fun1(a);
Temp c=fun1(b);
}

Answer 1

#include <iostream>
class Temp
{
public:
    int a;
    Temp() : a(0) {}
    Temp(const Temp &ref) : a(ref.a)
    {
      std::cout << "Temp(Temp&)" << std::endl;
    }
};

Temp fun1(Temp x)
{
Temp y(x);
Temp z=y;
return z;
}
int main(int ac, char**av)
{
Temp a;
Temp b=fun1(a);
Temp c=fun1(b);
}

Shows 6 calls for clang.

786_ g++ -std=c++11 test.cpp
787_ ./a.out
Temp(Temp&)
Temp(Temp&)
Temp(Temp&)
Temp(Temp&)
Temp(Temp&)
Temp(Temp&)