Self assignment check in assignment operator

Copy Constructor vs Assignment Operator in C++

Last Updated : 13 Aug, 2024

Copy constructor and Assignment operator are similar as they are both used to initialize one object using another object. But, there are some basic differences between them:

Copy constructor	Assignment operator
It is called when a new object is created from an existing object, as a copy of the existing object	This operator is called when an already initialized object is assigned a new value from another existing object.
It creates a separate memory block for the new object.	It does not automatically create a separate memory block or new memory space. However, if the class involves dynamic memory management, the assignment operator must first release the existing memory on the left-hand side and then allocate new memory as needed to copy the data from the right-hand side.
It is an overloaded constructor.	It is a bitwise operator.
C++ compiler implicitly provides a copy constructor, if no copy constructor is defined in the class.	A bitwise copy gets created, if the Assignment operator is not overloaded.
Syntax: className(const className &obj) { // body }	Syntax: className obj1, obj2; obj2 = obj1;

Consider the following C++ program.

CPP

// CPP Program to demonstrate the use of copy constructor
// and assignment operator
#include <iostream>
#include <stdio.h>
using namespace std;

class Test {
public:
    Test() {}
    Test(const Test& t)
    {
        cout << "Copy constructor called " << endl;
    }

    Test& operator=(const Test& t)
    {
        cout << "Assignment operator called " << endl;
        return *this;
    }
};

// Driver code
int main()
{
    Test t1, t2;
    t2 = t1;
    Test t3 = t1;
    getchar();
    return 0;
}

Output

Assignment operator called 
Copy constructor called

Explanation: Here, t2 = t1; calls the assignment operator, same as t2.operator=(t1); and Test t3 = t1; calls the copy constructor, same as Test t3(t1);

Must Read: When is a Copy Constructor Called in C++?

Self assignment check in assignment operator

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