C++ Tutorial Index

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C++ Control Statements

C++ If C++ Nested if C++ If-else C++ If-else-if C++ Switch C++ Break C++ Continue C++ Goto C++ For loop C++ While loop C++ Do while loop

C++ Functions

C++ Call by Value C++ Call by Reference C++ Recursion Function C++ Inline function C++ Friend function

C++ Arrays

Single dimension array Two dimension array

C++ Strings

C++ Strings

C++ Inheritance

C++ Inheritance Single level Inheritance Multilevel Inheritance Multiple Inheritance Hierarchical Inheritance Hybrid Inheritance

C++ Polymorphism

C++ Polymorphism C++ Overloading C++ Overriding C++ Virtual Function

C++ Pointers

C++ Pointers C++ this pointer

C++ Exception Handling

C++ Exception Handling

C++ Constructors

C++ Constructors Default Constructor Parameterize Constructor Copy constructor Constructor Overloading Destructor

C++ File Handling

C++ File Handling C++ Writing to file C++ Reading file C++ Close file

Miscellaneous

C Vs C++ C++ Comments C++ Data Abstraction C++ Identifier C++ Memory Management C++ Storage Classes C++ Void Pointer C++ Array To Function C++ Expressions C++ Features C++ Interfaces C++ Encapsulation std::min in C++ External merge sort in C++ Remove duplicates from sorted array in C++ Precision of floating point numbers Using these functions floor(), ceil(), trunc(), round() and setprecision() in C++ C++ References C++ Friend Functions C++ Mutable keyword Unary Operators in C++ Initialize Array of objects with parameterized constructors in C++ Differences between #define & const in C/C++ C++ Program to Implement Shell Sort C++ Program to Implement Merge Sort Storage Classes in C Vector resize() in C++ Passing by Reference Vs. Passing by the pointer in C++ Free vs delete() in C++ goto statement in C and C++ C++ program to read string using cin.getline() C++ String Concatenation Heap Sort in C++ Swap numbers in C++ Input Iterators in C++ Fibonacci Series in C++ C ++ Program: Alphabet Triangle and Number Triangle C++ Program: Matrix Multiplication C++ Program to Print Fibonacci Triangle Stack in C++ Maps in C++ Queue in C++ C++ Bitset C++ Algorithms Priority Queue in C++ C++ Multimap C++ Deque Function Pointer in C++ Sizeof() Operators in C++ C++ array of Pointers free() Vs delete in C Timsort Implementation Using C++ CPP Templates C++ Aggregation C++ Enumeration C++ Math Functions C++ Object Class C++ Queue Initialize Vector in C++ Vector in C++ C++ STL Components Function overloading in C++ C++ Maximum Index Problem C++ find missing in the second array C++ Program to find the product array puzzle C++ Program To Find Largest Subarray With 0 Sum C++ Program To Move All Zeros To The End Of The Array C++ Program to find the element that occurs once C++ Program to find the largest number formed from an array Constructor Vs Destructor C++ Namespaces C++ OOPs Concept C++ Static C++ Structs C++ Try-Catch C++ User Defined Exceptions C++ Virtual Destructor C++ vs C# Malloc() and new in C++ Palindrome Number Program in C++ Snake Code in C++ Splitting a string in C++ Structure Vs Class in C++ Virtual Function Vs Pure Virtual Function C++ Bidirectional Iterators C++ Forward Iterators C++ Iterators C++ Output Iterators C++ Range-based For Loop Converting string into integer in C++ LCM Program in C++ Type conversion in C++ Add two numbers using the function in C++ Advantage and disadvantage friend function C++ Armstrong Number Program in C++ ATM machine program in C++ using functions Binary to Decimal in C++ Bit Manipulation in C++ C++ Constructor C++ Dijkstra Algorithm Using the Priority Queue C++ int into String C++ Signal Handling Decimal to Binary in C++ Decimal to Hexadecimal in C++ Decimal to Octal in C++ Factorial Program in C++ Function in C++ Hexadecimal to Decimal in C++ Octal to Decimal in C++ Reverse a Number in C++ Structure Vs Class in C++ C++ Forward Iterators C++ Output Iterators C++ Prime number program Char Array to String in C++ Constructor Overloading in C++ Default arguments in C++ Different Ways to Compare Strings in C++ Dynamic Binding in C++ Program to convert infix to postfix expression in C++ SET Data Structure in C++ Upcasting and Downcasting in C++ Reverse an Array in C++ Fast Input and Output in C++ Delete Operator in C++ Copy elision in C++ C++ Date and Time C++ Bitwise XOR Operator Array of sets in C++ Binary Operator Overloading in C++ Binary Search in C++ Implementing the sets without C++ STL containers Scope Resolution Operator in C++ Smart pointers in C++ Types of polymorphism in C++ Exception Handling in C++ vs Java Const Keyword in C++ Type Casting in C++ Static keyword in C++ vs Java Inheritance in C++ vs Java How to concatenate two strings in C++ Programs to Print Pyramid Patterns in C++ swap() function in C++ Structure of C++ Program Stringstream in C++ and its applications rand() and srand() in C / C++ C++ Ternary Operator C++ Scope of Variables While Loop Examples in C++ Star pattern in C++ using For Loops For Loop Examples in C++ Do-While Loop Examples in C++ Top 5 IDEs for C++ That You Should Try Once Assertions in C/C++ C++ Convert Int to String Continue in C++ While loop Diamond Pattern in C++ using For Loop How to Reverse a String in C++ using Do-While Loop How to Reverse a String in C++ using For Loop How to Reverse a String in C++ using While Loop Infinite loop in C++ Loops in C++ Returning Multiple Values from a Function using Tuple and Pair in C++ wcscpy(), wcslen(), wcscmp() Functions in C++

C++ Virtual Destructor

In C++, a destructor is a class member function that is used to free up space or remove an object of the class that has gone out of scope. The name of a destructor is the same as the name of a class's function Object () {[native code]} function, but the destructor uses a tilde (~) symbol before its function name.

What do you mean by Virtual Destructor?

When the derivative class instances are destroyed using a base class pointer object, a virtual destroyer is used to free up the memory space allocated by the derived class object or instance. A virtual keyword is used in a base or parent class destructor to guarantee that both the base and derived class destructors are invoked at run time, but the derived class is called first and subsequently the base class to free up the space used by both destructors.

Why do we utilize Virtual Destructors?

When an object in the class is no longer in space or the main () function is about to exit, the program automatically calls the destructor to free the memory used by the class destructor method. Due to the initial binding of the compiler, only the parent class destroyer is executed while a pointer object of the base class that refers to the derived class is removed. This avoids invoking the destructor of the derived class, which causes memory leaks in the application. When the virtual keyword is followed by the destructor tilde (~) symbol inside the base class, it ensures that the destructor of the derived class is invoked first. The destructor of the base class is then called to free the space taken up by both destructors in the inheritance class.

In C++, here's an example of a program that shows destructor without utilizing virtual destructor:

#include<iostream> 
#include<bits/sdtc++.h>
#include<stdlib> 
using namespace std;  
class Virtual  
{                              
    public: /* A public access specifier defines Constructor and Destructor function to call by any object in the class. */  
    Virtual() // Constructor function.   
{  
    cout<< "\n Constructor Virtual class";  
}  
 ~Virtual() // Destructor function   
{  
    cout<< "\n Destructor Virtual class";  
}  
};  
  
class Derived: public Virtual  
{  
    public: /* A public access specifier defines Constructor and Destructor function to call by any object in the class. */  
    Derived() // Constructor function   
{  
    cout << "\n Constructor Derived class" ;  
}  
 ~Derived() // Destructor function   
{  
    cout << "\n Destructor Derived class" ; /* Destructor function is not called to release its space. */  
}         
};  
int main()  
{  
    Virtual *Vptr = new Derived; // Create a Virtual class pointer object   
       delete Vptr; /* Here pointer object is called to delete the space occupied by the destructor.*/  
}  

OUTPUT:

Constructor Virtual class
Constructor Derived class
Destructor Virtual class
……………………………………...
Process exited in 0.7344 seconds with return value 0
Press any key to continue……

Explanation:

When the compiler generates the code, it calls a pointer object in the main method that references to the Virtual class, as seen in the preceding output. As a result, it runs the function Object () {[native code]} () method of the Virtual class before moving on to the function Object () {[native code]} () code of the derived class. The pointer held by the Virtual Class Destroyer and Derived Class Destroyer is then discarded. Virtual class pointers only call. Destroyer of Virtual class not destroyer of derived class. As a result, the program's memory is leaked.

Important: Because the pointer object points to the Virtual class, only the Virtual class destroyer will be called or its occupied space will be removed if the Virtual class destroyer does not use the virtual keyword. Consequently, the derivative class does not call the destroyer to free the memory used by the derivative class, resulting in memory leakage.

In C++, here's an example of a program that shows destructor utilizing virtual destructor:

#include<iostream>
#include<bits/sdtc++.h>
#include<stdlib>  
using namespace std;  
class Virt  
{  
    public:  
    Virt() // Constructor member function.    
{  
    cout << "\n Constructor Virtual class";  // It prints first.  
}  
 virtual ~Virt() // Define the virtual destructor function to call the Destructor Derived function.  
{  
    cout << "\n Destructor Base class";  /  
}  
};  
// Inheritance concept  
class Derived: public Virt  
{  
    public:  
    Derived() // Constructor function.  
{  
    cout << "\n Constructor Derived class" ; /* After print the Constructor Virt, now it will prints. */  
}  
 ~Derived() // Destructor function   
{  
    cout << "\n Destructor Derived class"; /* The virtual Virt Class? Destructor calls it before calling the Virt Class Destructor. */  
}         
};  
int main()  
{  
    Virt *Vptr = new Derived; // A pointer object reference the Virt class.  
    delete Vptr; // Delete the pointer object.  
}  

OUTPUT:

Constructor Virt class
Constructor Derived class
Destructor Derived class
Destructor Virt class
………………………………………..
Process exited in 0.4535 seconds with return value 0
Press any key to exit.

Explanation:

In the program above, we used a virtual destroyer within a base class that calls a derivative class destroyer before calling a base class destroyer to free up space or fix a memory leak.



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