I would like to write a piece of code that shows all copy/assignment/delete etc. operations that are done on the object when passing it to a function.
I wrote this:
#include <iostream>
class A {
public:
A(){std::cout<<"A()"<<std::endl;}
void operator=(const A& a ){std::cout<<"A=A"<<std::endl;}
A(const A& a){std::cout<<"A(A)"<<std::endl;}
~A(){std::cout<<"~A"<<std::endl;}
};
void pv(A a){std::cout<<"pv(A a)"<<std::endl;}
void pr(A& a){std::cout<<"pr(A& a)"<<std::endl;}
void pp(A* a){std::cout<<"pp(A* a)"<<std::endl;}
void pc(const A& a){std::cout<<"pc(const A& a)"<<std::endl;}
int main() {
std::cout<<" -------- constr"<<std::endl;
A a = A();
std::cout<<" -------- copy constr"<<std::endl;
A b = A(a);
A c = a;
std::cout<<" -------- assignment"<<std::endl;
a = a;
a = b;
std::cout<<" -------- pass by value"<<std::endl;
pv(a);
std::cout<<" -------- pass by reference"<<std::endl;
pr(a);
std::cout<<" -------- pass by pointer"<<std::endl;
pp(&a);
std::cout<<" -------- pass by const reference"<<std::endl;
pc(a);
return 0;
}
Did I forget anything?
Is there anything else that has to be considered when comparing the different ways of passing an object?
See Question&Answers more detail:
os 与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…