A copy constructor call - c++

Question

I have declared a Point class like this :
class Point{
private :
int a,b;
public :
Point(Point const &p) {
a = p.a + 1;
b = 0;
}
Point(){a=2; b=3;}
int getX(){return a;}
int getY(){return b;}
};
int main(){
Point p1,p2;
p2=p1;
cout << p2.getX(); // 2
cout << p2.getY(); // 3
}
Why the copy constructor is not called ? as it's called here :
int main(){
Point p1;
Point p2=p1;
cout << p2.getX(); // 3
cout << p2.getY(); // 0
}

Answer 1

This is copy construction
Point p2=p1; // p2 is constructed here.
// This is shorthand for Point p2(p1);
This is assignment
p2=p1; // p2 already exists (it was created on the previous line).
The assignment operator is defined with:
// If you don't define this the compiler will generate one for you.
Point& operator=(Point const& rhs)
{
// Copy for rhs into this.
return *this;
}
// The compiler generated one looks like this:
Point& operator=(Point const& rhs)
{
a = rhs.a;
b = rhs.b;
return *this;
}

Answer 2

In the first program
int main(){
Point p1,p2;
p2=p1;
^^^^^
there is called the copy assignment operator created by the compiler implicitly.
In this program object p2 was already created using the default constructor
Point p1,p2;
In tfhe second program
int main(){
Point p1;
Point p2=p1;
^^^^^^^^^^^
there is indeed called the copy constructor.

Answer 3

Point p1,p2;
p2=p1;
p2 is already constructed so the second statement invokes the assignment operator
Point p1;
Point p2=p1;
Here p2 is copy-constructed since it had not been constructed before.
Consider this code:
#include <iostream>
class A {
public:
A() { std::cout << "Ctor called\n"; }
A(const A&) { std::cout << "Copy Ctor called\n"; }
A& operator=(const A&) { std::cout << "Assignment operator called\n"; return *this;}
};
int main() {
A a,b;
b = a;
A c;
A d = c;
}
the output of which is enlightening:
Argento:Desktop marinos$ clang++ test.cpp -o test
Argento:Desktop marinos$ ./test
Ctor called
Ctor called
Assignment operator called
Ctor called
Copy Ctor called