Operator = overload trap (the assignment constructor does not actually perform the assignment operation)

Write a test case as follows:

#include<iostream>

using namespace std;

class Test
{
	public:
		Test &operator=(const Test&)
		{
			cout<<"operator="<<endl;
		};
};

int main()
{
	Test t1;
	Test t2 = t1;
}

After execution, the result is:

 It can be seen that when performing operator overloading on "=", there is no output statement executed in the operator execution overload when = is called in main 

After improving it, do a test:

#include<iostream>

using namespace std;

class Test
{
	public:
		Test()
		{
			cout<<"Constructor"<<endl;
		}
		Test &operator=(const Test&)
		{
			cout<<"operator="<<endl;
		};
};

int main()
{
	Test t1;
	Test t2 = t1;
}

After execution, the result is:

It can be seen that in Test t2 = t1; it is not the "=" assignment that is executed, but the constructor that is executed

More specifically:

#include<iostream>

using namespace std;

class Test
{
	public:
		Test()
		{
			cout<<"Constructor"<<endl;
		}
		
		Test(const Test&)
		{
			cout<<"Copy Constructor"<<endl;
		}
		
		Test &operator=(const Test&)
		{
			cout<<"operator="<<endl;
		};
};

int main()
{
	Test t1;
	Test t2 = t1;
}

The output is:

 It is found that the copy constructor is actually called, and the copy constructor will call the standard constructor again

Then the initial program should be modified as follows:

#include<iostream>

using namespace std;

class Test
{
	public:

		Test &operator=(const Test&)
		{
			cout<<"operator="<<endl;
		};
};

int main()
{
	Test t1;
	Test t2;
	t2 = t1;
}

The execution results are as follows:

 So it is found that Test t2 = t1 does not perform the assignment operation, but executes the copy constructor