example of copy constructor and assignment operator in c

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Copy constructors and copy assignment operators (C++)

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Starting in C++11, two kinds of assignment are supported in the language: copy assignment and move assignment . In this article "assignment" means copy assignment unless explicitly stated otherwise. For information about move assignment, see Move Constructors and Move Assignment Operators (C++) .

Both the assignment operation and the initialization operation cause objects to be copied.

Assignment : When one object's value is assigned to another object, the first object is copied to the second object. So, this code copies the value of b into a :

Initialization : Initialization occurs when you declare a new object, when you pass function arguments by value, or when you return by value from a function.

You can define the semantics of "copy" for objects of class type. For example, consider this code:

The preceding code could mean "copy the contents of FILE1.DAT to FILE2.DAT" or it could mean "ignore FILE2.DAT and make b a second handle to FILE1.DAT." You must attach appropriate copying semantics to each class, as follows:

Use an assignment operator operator= that returns a reference to the class type and takes one parameter that's passed by const reference—for example ClassName& operator=(const ClassName& x); .

Use the copy constructor.

If you don't declare a copy constructor, the compiler generates a member-wise copy constructor for you. Similarly, if you don't declare a copy assignment operator, the compiler generates a member-wise copy assignment operator for you. Declaring a copy constructor doesn't suppress the compiler-generated copy assignment operator, and vice-versa. If you implement either one, we recommend that you implement the other one, too. When you implement both, the meaning of the code is clear.

The copy constructor takes an argument of type ClassName& , where ClassName is the name of the class. For example:

Make the type of the copy constructor's argument const ClassName& whenever possible. This prevents the copy constructor from accidentally changing the copied object. It also lets you copy from const objects.

Compiler generated copy constructors

Compiler-generated copy constructors, like user-defined copy constructors, have a single argument of type "reference to class-name ." An exception is when all base classes and member classes have copy constructors declared as taking a single argument of type const class-name & . In such a case, the compiler-generated copy constructor's argument is also const .

When the argument type to the copy constructor isn't const , initialization by copying a const object generates an error. The reverse isn't true: If the argument is const , you can initialize by copying an object that's not const .

Compiler-generated assignment operators follow the same pattern for const . They take a single argument of type ClassName& unless the assignment operators in all base and member classes take arguments of type const ClassName& . In this case, the generated assignment operator for the class takes a const argument.

When virtual base classes are initialized by copy constructors, whether compiler-generated or user-defined, they're initialized only once: at the point when they are constructed.

The implications are similar to the copy constructor. When the argument type isn't const , assignment from a const object generates an error. The reverse isn't true: If a const value is assigned to a value that's not const , the assignment succeeds.

For more information about overloaded assignment operators, see Assignment .

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Copy constructor in c++.

A copy constructor is a type of constructor that initializes an object using another object of the same class. In simple terms, a constructor which creates an object by initializing it with an object of the same class, which has been created previously is known as a copy constructor .

The process of initializing members of an object through a copy constructor is known as copy initialization . It is also called member-wise initialization because the copy constructor initializes one object with the existing object, both belonging to the same class on a member-by-member copy basis.

Syntax of Copy Constructor in C++

Copy constructor takes a reference to an object of the same class as an argument:

Here, the const qualifier is optional but is added so that we do not modify the obj by mistake.

Syntax of Copy Constructor

For a deeper understanding of constructors and memory management, check out our Complete C++ Course , which covers constructors, destructors, and advanced object management techniques.

Examples of Copy Constructor in C++

Example 1: user defined copy constructor.

If the programmer does not define the copy constructor, the compiler does it for us.

Example 2: Default Copy Constructor

An implicitly defined copy constructor will copy the bases and members of an object in the same order that a constructor would initialize the bases and members of the object.

Need of User Defined Copy Constructor

If we don’t define our own copy constructor, the C++ compiler creates a default copy constructor for each class which works fine in general. However, we need to define our own copy constructor only if an object has pointers or any runtime allocation of the resource like a file handle , a network connection, etc because the default constructor does only shallow copy.

Shallow Copy means that only the pointers will be copied not the actual resources that the pointers are pointing to. This can lead to dangling pointers if the original object is deleted.

Deep copy is possible only with a user-defined copy constructor. In a user-defined copy constructor, we make sure that pointers (or references) of copied objects point to new copy of the dynamic resource allocated manually in the copy constructor using new operators.

Example: Class Where a Copy Constructor is Required

Following is a complete C++ program to demonstrate the use of the Copy constructor. In the following String class, we must write a copy constructor.

Note: Such classes also need the overloaded assignment operator. See this article for more info – C++ Assignment Operator Overloading

What would be the problem if we remove the copy constructor from the above code?

If we remove the copy constructor from the above program, we don’t get the expected output. The c hanges made to str2 reflect in str1 as well which is never expected. Also, if the str1 is destroyed, the str2’s data member s will be pointing to the deallocated memory.

When is the Copy Constructor Called?

In C++, a copy constructor may be called in the following cases:

When an object of the class is returned by value.
When an object of the class is passed (to a function) by value as an argument.
When an object is constructed based on another object of the same class.
When the compiler generates a temporary object.

It is, however, not guaranteed that a copy constructor will be called in all these cases, because the C++ Standard allows the compiler to optimize the copy away in certain cases, one example is the return value optimization (sometimes referred to as RVO).

Refer to this article for more details – When is a Copy Constructor Called in C++?

Copy Elision

In copy elision, the compiler prevents the making of extra copies by making the use to techniques such as NRVO and RVO which results in saving space and better the program complexity (both time and space); Hence making the code more optimized.

Copy Constructor vs Assignment Operator

The main difference between Copy Constructor and Assignment Operator is that the Copy constructor makes a new memory storage every time it is called while the assignment operator does not make new memory storage.

Which of the following two statements calls the copy constructor and which one calls the assignment operator?

A copy constructor is called when a new object is created from an existing object, as a copy of the existing object. The assignment operator is called when an already initialized object is assigned a new value from another existing object. In the above example (1) calls the copy constructor and (2) calls the assignment operator.

Frequently Asked Questions in C++ Copy Constructors

Can we make the copy constructor private .

Yes, a copy constructor can be made private. When we make a copy constructor private in a class, objects of that class become non-copyable. This is particularly useful when our class has pointers or dynamically allocated resources. In such situations, we can either write our own copy constructor like the above String example or make a private copy constructor so that users get compiler errors rather than surprises at runtime.

Why argument to a copy constructor must be passed as a reference?

If you pass the object by value in the copy constructor, it will result in a recursive call to the copy constructor itself. This happens because passing by value involves making a copy, and making a copy involves calling the copy constructor, leading to an infinite recursion. Using a reference avoids this recursion. So, we use reference of objects to avoid infinite calls.

Why argument to a copy constructor should be const?

One reason for passing const reference is, that we should use const in C++ wherever possible so that objects are not accidentally modified. This is one good reason for passing reference as const , but there is more to it than ‘ Why argument to a copy constructor should be const?’

Constructors in C++

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C++ Control Statements

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C++ Functions

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C++ Pointers and References

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C++ Strings

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C++ Structures and Unions

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Structures in C++ We often come around situations where we need to store a group of data whether of similar data types or non-similar data types. We have seen Arrays in C++ which are used to store set of data of similar data types at contiguous memory locations.Unlike Arrays, Structures in C++ are user defined data t 5 min read
C++ - Pointer to Structure Pointer to structure in C++ can also be referred to as Structure Pointer. A structure Pointer in C++ is defined as the pointer which points to the address of the memory block that stores a structure. Below is an example of the same: Syntax: struct name_of_structure *ptr; // Initialization of structu 2 min read
Self Referential Structures Self Referential structures are those structures that have one or more pointers which point to the same type of structure, as their member. In other words, structures pointing to the same type of structures are self-referential in nature Example: [GFGTABS] CPP struct node { int data1; char data2; s 8 min read
Difference Between C Structures and C++ Structures Let's discuss, what are the differences between structures in C and structures in C++? In C++, structures are similar to classes. Differences Between the C and C++ StructuresC Structures C++ Structures Only data members are allowed, it cannot have member functions.Can hold both: member functions and 6 min read
Enumeration in C++ Enumeration (Enumerated type) is a user-defined data type that can be assigned some limited values. These values are defined by the programmer at the time of declaring the enumerated type. If we assign a float value to a character value, then the compiler generates an error. In the same way, if we t 3 min read
typedef in C++ typedef keyword in C++ is used for aliasing existing data types, user-defined data types, and pointers to a more meaningful name. Typedefs allow you to give descriptive names to standard data types, which can also help you self-document your code. Mostly typedefs are used for aliasing, only if the p 6 min read
Array of Structures vs Array within a Structure in C Both Array of Structures and Array within a Structure in C programming is a combination of arrays and structures but both are used to serve different purposes. Array within a StructureA structure is a data type in C that allows a group of related variables to be treated as a single unit instead of s 5 min read

C++ Dynamic Memory Management

Dynamic Memory Allocation in C using malloc(), calloc(), free() and realloc() Since C is a structured language, it has some fixed rules for programming. One of them includes changing the size of an array. An array is a collection of items stored at contiguous memory locations. As can be seen, the length (size) of the array above is 9. But what if there is a requirement to cha 9 min read
new and delete Operators in C++ For Dynamic Memory Dynamic memory allocation in C/C++ refers to performing memory allocation manually by a programmer. Dynamically allocated memory is allocated on Heap, and non-static and local variables get memory allocated on Stack (Refer to Memory Layout C Programs for details). What are applications? One use of d 6 min read
new vs malloc() and free() vs delete in C++ We use new and delete operators in C++ to dynamically allocate memory whereas malloc() and free() functions are also used for the same purpose in C and C++. The functionality of the new or malloc() and delete or free() seems to be the same but they differ in various ways.The behavior with respect to 5 min read
What is Memory Leak? How can we avoid? A memory leak occurs when programmers create a memory in a heap and forget to delete it. The consequence of the memory leak is that it reduces the performance of the computer by reducing the amount of available memory. Eventually, in the worst case, too much of the available memory may become alloca 3 min read
Difference between Static and Dynamic Memory Allocation in C Memory Allocation: Memory allocation is a process by which computer programs and services are assigned with physical or virtual memory space. The memory allocation is done either before or at the time of program execution. There are two types of memory allocations: Compile-time or Static Memory Allo 3 min read

C++ Object-Oriented Programming

Object Oriented Programming in C++ Object-oriented programming - As the name suggests uses objects in programming. Object-oriented programming aims to implement real-world entities like inheritance, hiding, polymorphism, etc. in programming. The main aim of OOP is to bind together the data and the functions that operate on them so th 10 min read
C++ Classes and Objects In C++, classes and objects are the basic building block that leads to Object-Oriented programming in C++. In this article, we will learn about C++ classes, objects, look at how they work and how to implement them in our C++ program. What is a Class in C++?A class is a user-defined data type, which 10 min read
Access Modifiers in C++ Access modifiers are used to implement an important aspect of Object-Oriented Programming known as Data Hiding. Consider a real-life example: The Research and Analysis Wing (R&AW), having 10 core members, has come into possession of sensitive confidential information regarding national security. 6 min read
Friend Class and Function in C++ A friend class can access private and protected members of other classes in which it is declared as a friend. It is sometimes useful to allow a particular class to access private and protected members of other classes. For example, a LinkedList class may be allowed to access private members of Node. 6 min read
Constructors in C++ Constructor in C++ is a special method that is invoked automatically at the time an object of a class is created. It is used to initialize the data members of new objects generally. The constructor in C++ has the same name as the class or structure. It constructs the values i.e. provides data for th 7 min read
Default Constructors in C++ A default constructor is a constructor that either takes no arguments or has default values for all its parameters. It is also referred to as a zero-argument constructor when it explicitly accepts no arguments. If a default constructor is not explicitly defined by the programmer in the source code, 4 min read
Copy Constructor in C++ A copy constructor is a type of constructor that initializes an object using another object of the same class. In simple terms, a constructor which creates an object by initializing it with an object of the same class, which has been created previously is known as a copy constructor. The process of 7 min read
Destructors in C++ Destructor is an instance member function that is invoked automatically whenever an object is going to be destroyed. Meaning, a destructor is the last function that is going to be called before an object is destroyed. In this article, we will learn about the destructors in C++, how they work, how an 5 min read
Private Destructor in C++ Destructors with the access modifier as private are known as Private Destructors. Whenever we want to prevent the destruction of an object, we can make the destructor private. What is the use of private destructor? Whenever we want to control the destruction of objects of a class, we make the destru 4 min read
When is a Copy Constructor Called in C++? A copy constructor is a member function that initializes an object using another object of the same class. The Copy constructor is called mainly when a new object is created from an existing object, as a copy of the existing object. In C++, a Copy Constructor may be called for the following cases: 1 2 min read
Shallow Copy and Deep Copy in C++ In general, creating a copy of an object means to create an exact replica of the object having the same literal value, data type, and resources. There are two ways that are used by C++ compiler to create a copy of objects. Copy ConstructorAssignment Operator// Copy ConstructorGeeks Obj1(Obj);orGeeks 6 min read
When Should We Write Our Own Copy Constructor in C++? A copy constructor is a member function that initializes an object using another object of the same class. (See this article for reference). When should we write our own copy constructor?C++ compiler provides a default copy constructor (and assignment operator) with class. When we don't provide an i 2 min read
Does C++ compiler create default constructor when we write our own? No, the C++ compiler doesn't create a default constructor when we define any type of constructor manually in the class. ExplanationThe default constructor is used to create an object's instance without any arguments. In C++, the compiler implicitly creates a default constructor for every class which 2 min read
C++ Static Data Members Static data members are class members that are declared using static keywords. A static member has certain special characteristics which are as follows: Only one copy of that member is created for the entire class and is shared by all the objects of that class, no matter how many objects are created 6 min read
Static Member Function in C++ The static keyword is used with a variable to make the memory of the variable static once a static variable is declared its memory can't be changed. To know more about static keywords refer to the article static Keyword in C++. Static Member in C++ Static members of a class are not associated with t 4 min read
'this' pointer in C++ In C++, 'this' pointers is a pointer to the current instance of a class. It is used to refer to the object within its own member functions. In this article, we will learn how to use 'this' pointer in C++. Let's take a look at an example: [GFGTABS] C++ #include <iostream> using namespace std; / 6 min read
Scope Resolution Operator vs this pointer in C++ Scope resolution operator is for accessing static or class members and this pointer is for accessing object members when there is a local variable with the same name. Consider below C++ program: C/C++ Code // C++ program to show that local parameters hide // class members #include <iostream> u 3 min read
Local Classes in C++ A class declared inside a function becomes local to that function and is called Local Class in C++. A local class name can only be used locally i.e., inside the function and not outside it.The methods of a local class must be defined inside it only.A local class can have static functions but, not st 6 min read
Nested Classes in C++ A nested class is a class which is declared in another enclosing class. A nested class is a member and as such has the same access rights as any other member. The members of an enclosing class have no special access to members of a nested class; the usual access rules shall be obeyed. For example, p 1 min read
Enum Classes in C++ and Their Advantage over Enum DataType Enums, or enumerated types, are user-defined data types in C++ that allow the programmer to define a set of named values. These values are fixed and predetermined at the time of declaration. However, traditional enums have some limitations, which have been addressed by the introduction of Enum Class 5 min read
Difference Between Structure and Class in C++ In C++, a structure works the same way as a class, except for just two small differences. The most important of them is hiding implementation details. A structure will by default not hide its implementation details from whoever uses it in code, while a class by default hides all its implementation d 3 min read
Why C++ is partially Object Oriented Language? The basic thing which are the essential feature of an object oriented programming are Inheritance, Polymorphism and Encapsulation. Any programming language that supports these feature completely are complete Object-oriented programming language whereas any language that supports all three feature bu 3 min read

C++ Encapsulation and Abstraction

Encapsulation in C++ Encapsulation in C++ is defined as the wrapping up of data and information in a single unit. In Object Oriented Programming, Encapsulation is defined as binding together the data and the functions that manipulate them. Consider a real-life example of encapsulation, in a company, there are different 5 min read
Abstraction in C++ Data abstraction is one of the most essential and important features of object-oriented programming in C++. Abstraction means displaying only essential information and ignoring the details. Data abstraction refers to providing only essential information about the data to the outside world, ignoring 4 min read
Difference between Abstraction and Encapsulation in C++ Abstraction: In OOPs, Abstraction is the method of getting information where the information needed will be taken in such a simplest way that solely the required components are extracted, and also the ones that are considered less significant are unnoticed. The concept of abstraction only shows nece 3 min read
C++ Polymorphism The word "polymorphism" means having many forms. In simple words, we can define polymorphism as the ability of a message to be displayed in more than one form. A real-life example of polymorphism is a person who at the same time can have different characteristics. A man at the same time is a father, 7 min read
Function Overriding in C++ A function is a block of statements that together performs a specific task by taking some input and producing a particular output. Function overriding in C++ is termed as the redefinition of base class function in its derived class with the same signature i.e. return type and parameters. It can be o 7 min read
Virtual Functions and Runtime Polymorphism in C++ A virtual function is a member function that is declared in the base class using the keyword virtual and is re-defined (Overridden) in the derived class. It tells the compiler to perform late binding where the compiler matches the object with the right called function and executes it during the runt 8 min read
Difference between Inheritance and Polymorphism Inheritance is one in which a new class is created that inherits the properties of the already exist class. It supports the concept of code reusability and reduces the length of the code in object-oriented programming. Types of Inheritance are:Single inheritanceMulti-level inheritanceMultiple inheri 5 min read
Function Overloading in C++ Function overloading is a feature of object-oriented programming where two or more functions can have the same name but different parameters. When a function name is overloaded with different jobs it is called Function Overloading. In Function Overloading “Function” name should be the same and the a 4 min read
Constructor Overloading in C++ Prerequisites: Constructors in C++ In C++, We can have more than one constructor in a class with same name, as long as each has a different list of arguments.This concept is known as Constructor Overloading and is quite similar to function overloading. Overloaded constructors essentially have the sa 2 min read
Functions that cannot be overloaded in C++ In C++, following function declarations cannot be overloaded. 1) Function declarations that differ only in the return type. For example, the following program fails in compilation. C/C++ Code #include<iostream> int foo() { return 10; } char foo() { return 'a'; } int main() { char x = f 3 min read
Function overloading and const keyword Function overloading is a feature of object-oriented programming where two or more functions can have the same name but different parameters. When a function name is overloaded with different jobs it is called Function Overloading. In Function Overloading “Function” name should be the same and the a 5 min read
Function Overloading and Return Type in C++ Function overloading is possible in C++ and Java but only if the functions must differ from each other by the types and the number of arguments in the argument list. However, functions can not be overloaded if they differ only in the return type. Why is Function overloading not possible with differe 2 min read
Function Overloading and float in C++ Although polymorphism is a widely useful phenomena in C++ yet it can be quite complicated at times. For instance consider the following code snippet: C/C++ Code #include<iostream> using namespace std; void test(float s,float t) { cout << "Function with float call 2 min read
Can main() be overloaded in C++? Predict the output of following C++ program. #include <iostream> using namespace std; int main(int a) { cout << a << "\n"; return 0; } int main(char *a) { cout << a << endl; return 0; } int main(int a, int b) { cout << a << " " << b 2 min read
Function Overloading vs Function Overriding in C++ Function Overloading (achieved at compile time) Function Overloading provides multiple definitions of the function by changing signature i.e. changing number of parameters, change datatype of parameters, return type doesn’t play any role. It can be done in base as well as derived class.Example: void 3 min read
Advantages and Disadvantages of Function Overloading in C++ Function overloading is one of the important features of object-oriented programming. It allows users to have more than one function having the same name but different properties. Overloaded functions enable users to supply different semantics for a function, depending on the signature of functions. 3 min read

C++ Operator Overloading

Operator Overloading in C++ in C++, Operator overloading is a compile-time polymorphism. It is an idea of giving special meaning to an existing operator in C++ without changing its original meaning. In this article, we will further discuss about operator overloading in C++ with examples and see which operators we can or cannot 9 min read
Types of Operator Overloading in C++ C++ provides a special function to change the current functionality of some operators within its class which is often called as operator overloading. Operator Overloading is the method by which we can change some specific operators' functions to do different tasks. Syntax: Return_Type classname :: o 4 min read
Functors in C++ Please note that the title is Functors (Not Functions)!! Consider a function that takes only one argument. However, while calling this function we have a lot more information that we would like to pass to this function, but we cannot as it accepts only one parameter. What can be done? One obvious an 3 min read
What are the Operators that Can be and Cannot be Overloaded in C++? There are various ways to overload Operators in C++ by implementing any of the following types of functions: 1) Member Function 2) Non-Member Function 3) Friend Function List of operators that can be overloaded are: + - * ? % ? & | ~ ! = < > += -= *= ?= %= ?= &= |= << >> 4 min read
Inheritance in C++ The capability of a class to derive properties and characteristics from another class is called Inheritance. Inheritance is one of the most important features of Object Oriented Programming in C++. In this article, we will learn about inheritance in C++, its modes and types along with the informatio 15+ min read
C++ Inheritance Access Prerequisites: Class-Object in C++Inheritance in C++Before learning about Inheritance Access we need to know about access specifiers. There are three Access specifiers in C++. These are: public - members are accessible from outside the class, and members can be accessed from anywhere.private - membe 4 min read
Multiple Inheritance in C++ Multiple Inheritance is a feature of C++ where a class can inherit from more than one classes. The constructors of inherited classes are called in the same order in which they are inherited. For example, in the following program, B's constructor is called before A's constructor. A class can be deriv 5 min read
C++ Hierarchical Inheritance Inheritance is a feature of Object-Oriented-programming in which a derived class (child class) inherits the property (data member and member functions) of the Base class (parent class). For example, a child inherits the traits of their parents. In Hierarchical inheritance, more than one sub-class in 4 min read
C++ Multilevel Inheritance Multilevel Inheritance in C++ is the process of deriving a class from another derived class. When one class inherits another class it is further inherited by another class. It is known as multi-level inheritance. For example, if we take Grandfather as a base class then Father is the derived class th 2 min read
Constructor in Multiple Inheritance in C++ Constructor is a class member function with the same name as the class. The main job of the constructor is to allocate memory for class objects. Constructor is automatically called when the object is created. Multiple Inheritance: Multiple Inheritance is a feature of C++ where a class can derive fro 2 min read
Inheritance and Friendship in C++ Inheritance in C++: This is an OOPS concept. It allows creating classes that are derived from other classes so that they automatically include some of the functionality of its base class and some functionality of its own. (See this article for reference) Friendship in C++: Usually, private and prote 2 min read
Does overloading work with Inheritance? If we have a function in base class and another function with the same name in derived class, can the base class function be called from derived class object? This is an interesting question and as an experiment, predict the output of the following C++ program: [GFGTABS] C++ #include <iostream 5 min read

C++ Virtual Functions

Virtual Function in C++ A virtual function (also known as virtual methods) is a member function that is declared within a base class and is re-defined (overridden) by a derived class. When you refer to a derived class object using a pointer or a reference to the base class, you can call a virtual function for that object a 6 min read
Virtual Functions in Derived Classes in C++ A virtual function is a member function of a base class that is overridden by a derived class. When you use a pointer or a reference to the base class to refer to a derived class object, you can call a virtual function for that object and have it run the derived class's version of the function. In C 2 min read
Default Arguments and Virtual Function in C++ Default Arguments are the values provided during function declaration, such that values can be automatically assigned if no argument is passed to them. In case any value is passed the default value is overridden and it becomes a parameterized argument. Virtual function is a member function that is d 3 min read
Can Virtual Functions be Inlined in C++? Virtual functions are member functions that are declared in the base class using the keyword virtual and can be overridden by the derived class. They are used to achieve Runtime polymorphism or say late binding or dynamic binding. Inline functions are used to replace the function calling location wi 2 min read
Virtual Destructor Deleting a derived class object using a pointer of base class type that has a non-virtual destructor results in undefined behavior. To correct this situation, the base class should be defined with a virtual destructor. For example, the following program results in undefined behavior. C/C++ Code // C 2 min read
Advanced C++ | Virtual Constructor In C++, we CANNOT make a constructor virtual. The reason is that C++ is a statically typed language, so the concept of a virtual constructor is a contradiction because the compiler needs to know the exact type at compile time to allocate the correct amount of memory and initialize the object correct 8 min read
Advanced C++ | Virtual Copy Constructor In the virtual constructor idiom we have seen the way to construct an object whose type is not determined until runtime. Is it possible to create an object without knowing it's exact class type? The virtual copy constructor address this question.Sometimes we may need to construct an object from anot 5 min read
Pure Virtual Functions and Abstract Classes in C++ Sometimes implementation of all functions cannot be provided in a base class because we don't know the implementation. Such a class is called an abstract class.For example, let Shape be a base class. We cannot provide the implementation of function draw() in Shape, but we know every derived class mu 6 min read
Pure Virtual Destructor in C++ A pure virtual destructor can be declared in C++. After a destructor has been created as a pure virtual object(instance of a class), where the destructor body is provided. This is due to the fact that destructors will not be overridden in derived classes, but will instead be called in reverse order. 4 min read
Can Static Functions Be Virtual in C++? In C++, a static member function of a class cannot be virtual. Virtual functions are invoked when you have a pointer or reference to an instance of a class. Static functions aren't tied to the instance of a class but they are tied to the class. C++ doesn't have pointers-to-class, so there is no scen 1 min read
RTTI (Run-Time Type Information) in C++ In C++, RTTI (Run-time type information) is a mechanism that exposes information about an object's data type at runtime and is available only for the classes which have at least one virtual function. It allows the type of an object to be determined during program execution. Runtime Casts The runtime 3 min read
Can Virtual Functions be Private in C++? A virtual function can be private as C++ has access control, but not visibility control. As mentioned virtual functions can be overridden by the derived class but under all circumstances will only be called within the base class. Example 1: Calling Private Virtual Function from Base Class Pointer to 4 min read

C++ Exception Handling

Exception Handling in C++ In C++, exceptions are runtime anomalies or abnormal conditions that a program encounters during its execution. The process of handling these exceptions is called exception handling. Using the exception handling mechanism, the control from one part of the program where the exception occurred can be 11 min read
Exception Handling using classes in C++ In this article, we will discuss how to handle the exceptions using classes. Exception Handling: Exceptions are run-time anomalies or abnormal conditions that a program encounters during its execution.There are two types of exceptions:Synchronous ExceptionAsynchronous Exception(Ex: which are beyond 3 min read
Stack Unwinding in C++ Stack Unwinding is the process of removing function entries from function call stack at run time. The local objects are destroyed in reverse order in which they were constructed. Stack Unwinding is generally related to Exception Handling. In C++, when an exception occurs, the function call stack is 3 min read
User-defined Custom Exception with class in C++ We can use Exception handling with class too. Even we can throw an exception of user defined class types. For throwing an exception of say demo class type within try block we may write throw demo(); Example 1: Program to implement exception handling with single class C/C++ Code #include <iostream 3 min read

C++ Files and Streams

File Handling through C++ Classes File handling is used to store data permanently in a computer. Using file handling we can store our data in secondary memory (Hard disk).How to achieve the File HandlingFor achieving file handling we need to follow the following steps:- STEP 1-Naming a file STEP 2-Opening a file STEP 3-Writing data 8 min read
I/O Redirection in C++ In C, we could use the function freopen() to redirect an existing FILE pointer to another stream. The prototype for freopen() is given as FILE * freopen ( const char * filename, const char * mode, FILE * stream ); For Example, to redirect the stdout to say a textfile, we could write : freopen ("text 3 min read
Templates in C++ with Examples A template is a simple yet very powerful tool in C++. The simple idea is to pass the data type as a parameter so that we don't need to write the same code for different data types. For example, a software company may need to sort() for different data types. Rather than writing and maintaining multip 10 min read
Using Keyword in C++ STL The using keyword in C++ is a tool that allows developers to specify the use of a particular namespace. This is especially useful when working with large codebases or libraries where there may be many different namespaces in use. The using keyword can be used to specify the use of a single namespace 6 min read

C++ Standard Template Library (STL)

C++ Standard Template Library (STL) The C++ Standard Template Library (STL) is a set of template classes and functions that provides the implementation of common data structures and algorithms such as lists, stacks, arrays, sorting, searching, etc. It also provides the iterators and functors which makes it easier to work with algorith 9 min read
Containers in C++ STL (Standard Template Library) A container is a holder object that stores a collection of other objects (its elements). They are implemented as class templates, which allows great flexibility in the types supported as elements. The container manages the storage space for its elements and provides member functions to access them, 2 min read
Introduction to Iterators in C++ An iterator is an object (like a pointer) that points to an element inside the container. We can use iterators to move through the contents of the container. They can be visualized as something similar to a pointer pointing to some location and we can access the content at that particular location u 6 min read
Algorithm Library | C++ Magicians STL Algorithm For all those who aspire to excel in competitive programming, only having a knowledge about containers of STL is of less use till one is not aware what all STL has to offer. STL has an ocean of algorithms, for all < algorithm > library functions : Refer here.Some of the most used algorithms on 7 min read

C++ Preprocessors

C Preprocessors Preprocessors are programs that process the source code before compilation. Several steps are involved between writing a program and executing a program in C. Let us have a look at these steps before we actually start learning about Preprocessors. You can see the intermediate steps in the above diag 10 min read
C Preprocessor Directives In almost every C program we come across, we see a few lines at the top of the program preceded by a hash (#) sign. They are called preprocessor directives and are preprocessed by the preprocessor before actual compilation begins. The end of these lines is identified by the newline character '\n', n 8 min read
#include in C #include is a way of including a standard or user-defined file in the program and is mostly written at the beginning of any C program. The #include preprocessor directive is read by the preprocessor and instructs it to insert the contents of a user-defined or system header file in our C program. The 5 min read
Difference between Preprocessor Directives and Function Templates in C++ Preprocessor Directives are programs that process our source code before compilation. There are a number of steps involved between writing a program and executing a program in C / C++. Below is the program to illustrate the functionality of Function Templates: [GFGTABS] C++ // C++ program to illustr 3 min read

C++ Namespace

Namespace in C++ | Set 1 (Introduction) Namespace provide the space where we can define or declare identifier i.e. variable, method, classes.Using namespace, you can define the space or context in which identifiers are defined i.e. variable, method, classes. In essence, a namespace defines a scope.Advantage of Namespace to avoid name coll 11 min read
namespace in C++ | Set 2 (Extending namespace and Unnamed namespace) We have introduced namespaces in below set 1.Namespace in C++ | Set 1 (Introduction) Defining a Namespace: A namespace definition begins with the keyword namespace followed by the namespace name as follows: namespace namespace_name {// code declarations i.e. variable (int a;)method (void add();)clas 4 min read
Namespace in C++ | Set 3 (Accessing, creating header, nesting and aliasing) Namespace in C++ | Set 1 (Introduction) Namespace in C++ | Set 2 (Extending namespace and Unnamed namespace) Different ways to access namespace: In C++, there are two ways of accessing namespace variables and functions. Defining a Namespace: A namespace definition begins with the keyword namespace f 5 min read
C++ Inline Namespaces and Usage of the "using" Directive Inside Namespaces Prerequisite: Namespaces in C++ In C++, namespaces can be nested, and the resolution of namespace variables is hierarchical. An inline namespace is a namespace that uses the optional keyword inline in its original-namespace definition. This allows the identifiers of the nested inline namespace to be 3 min read

Advanced C++

Multithreading in C++ Multithreading is a feature that allows concurrent execution of two or more parts of a program for maximum utilization of the CPU. Each part of such a program is called a thread. So, threads are lightweight processes within a process. Multithreading support was introduced in C++11. Prior to C++11, w 6 min read
Smart Pointers in C++ Prerequisite: Pointers in C++ Pointers are used for accessing the resources which are external to the program - like heap memory. So, for accessing the heap memory (if anything is created inside heap memory), pointers are used. When accessing any external resource we just use a copy of the resource. 9 min read
auto_ptr vs unique_ptr vs shared_ptr vs weak_ptr in C++ Prerequisite – Smart Pointers Smart Pointer is a pointer-wrapping stack-allocated object. Smart pointers, in plain terms, are classes that wrap a pointer, or scoped pointers. C++ libraries provide implementations of smart pointers in the following types: auto_ptrunique_ptrshared_ptrweak_ptr They all 7 min read
Type of 'this' Pointer in C++ In C++, this pointer refers to the current object of the class and passes it as a parameter to another method. 'this pointer' is passed as a hidden argument to all non-static member function calls. Type of 'this' pointer The type of this depends upon function declaration. The type of this pointer is 2 min read
"delete this" in C++ Ideally delete operator should not be used for this pointer. However, if used, then following points must be considered.1) delete operator works only for objects allocated using operator new (See this post). If the object is created using new, then we can do delete this, otherwise behavior is undefi 1 min read
Passing a Function as a Parameter in C++ A function is a set of statements that take inputs, perform some specific computation, and produce output. The idea to use functions is to perform some commonly or repeatedly done tasks together and make a function so that instead of writing the same code again and again for different inputs. The ge 4 min read
Signal Handling in C++ Signals are the interrupts that force an OS to stop its ongoing task and attend the task for which the interrupt has been sent. These interrupts can pause service in any program of an OS. Similarly, C++ also offers various signals which it can catch and process in a program. Here is a list of variou 3 min read
Generics in C++ Generics is the idea to allow type (Integer, String, … etc and user-defined types) to be a parameter to methods, classes and interfaces. For example, classes like an array, map, etc, which can be used using generics very efficiently. We can use them for any type. The method of Generic Programming is 3 min read
Difference between C++ and Objective C 1. C++ :C++ or CPP is a general-purpose statically typed object-oriented programming language. In 1979, a Danish computer scientist named Bjarne Stroustrup wanted to make an extension to C that would allow it to use classes. This seed has expanded since then and had become one of the most used and w 3 min read
Write a C program that won't compile in C++ Although C++ is designed to have backward compatibility with C, there can be many C programs that would produce compiler errors when compiled with a C++ compiler. Following is the list of the C programs that won’t compile in C++: Calling a function before the declarationUsing normal pointer with con 4 min read
Write a program that produces different results in C and C++ Write a program that compiles and runs both in C and C++, but produces different results when compiled by C and C++ compilers. There can be many such programs, following are some of them. 1) Character literals are treated differently in C and C++. In C character literals like 'a', 'b', ..etc are tre 2 min read
How does 'void*' differ in C and C++? C allows a void* pointer to be assigned to any pointer type without a cast, whereas in C++, it does not. We have to explicitly typecast the void* pointer in C++ For example, the following is valid in C but not C++: void* ptr; int *i = ptr; // Implicit conversion from void* to int* Similarly, int *j 1 min read
Type Difference of Character Literals in C and C++ Every literal (constant) in C/C++ will have a type of information associated with it. In both C and C++, numeric literals (e.g. 10) will have int as their type. It means sizeof(10) and sizeof(int) will return the same value.If we compile what we have said in terms of code then it will look something 2 min read
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C++ vs Java

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Competitive Programming in C++

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copy-constructors-and-copy-assignment-operators-cpp.md

Latest commit, file metadata and controls, copy constructors and copy assignment operators (c++).

Both the assignment operation and the initialization operation cause objects to be copied.

Assignment : When one object's value is assigned to another object, the first object is copied to the second object. So, this code copies the value of b into a :

Initialization : Initialization occurs when you declare a new object, when you pass function arguments by value, or when you return by value from a function.

You can define the semantics of "copy" for objects of class type. For example, consider this code:

Use an assignment operator operator= that returns a reference to the class type and takes one parameter that's passed by const reference—for example ClassName& operator=(const ClassName& x); .

Use the copy constructor.

The copy constructor takes an argument of type ClassName& , where ClassName is the name of the class. For example:

Compiler generated copy constructors

When virtual base classes are initialized by copy constructors, whether compiler-generated or user-defined, they're initialized only once: at the point when they are constructed.

For more information about overloaded assignment operators, see Assignment .

21.12 — Overloading the assignment operator

The copy assignment operator (operator=) is used to copy values from one object to another already existing object .

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c++ - The copy constructor and assignment operator - Stack ...
The assignment operator is to deal with an already existing object. The assignment operator is used to change an existing instance to have the same values as the rvalue, which means that the instance has to be destroyed and re-initialized if it has internal dynamic memory. Useful link : Copy Constructors, Assignment Operators, and More
Copy Constructor vs Assignment Operator in C++ - GeeksforGeeks
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: 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.
Copy constructors and copy assignment operators (C++)
Use an assignment operator operator= that returns a reference to the class type and takes one parameter that's passed by const reference—for example ClassName& operator=(const ClassName& x);. Use the copy constructor.
Copy Constructors and Assignment Operators - Stanford University
C++ handles object copying and assignment through two functions called copy constructors and assignment operators. While C++ will automatically provide these functions if you don't explicitly define them, in many cases you'll need to manually control how your objects are duplicated.
Copy constructors, assignment operators, - C++ Articles
What is a copy constructor? A copy constructor is a special constructor for a class/struct that is used to make a copy of an existing instance. According to the C++ standard, the copy constructor for MyClass must have one of the following signatures:
Copy Constructor in C++ - GeeksforGeeks
The main difference between Copy Constructor and Assignment Operator is that the Copy constructor makes a new memory storage every time it is called while the assignment operator does not make new memory storage.
copy-constructors-and-copy-assignment-operators-cpp.md
Use an assignment operator operator= that returns a reference to the class type and takes one parameter that's passed by const reference—for example ClassName& operator=(const ClassName& x);. Use the copy constructor. If you don't declare a copy constructor, the compiler generates a member-wise copy constructor for you.
21.13 — Shallow vs. deep copying – Learn C++ - LearnCpp.com
Consequently, C++ will provide a default copy constructor and default assignment operator that do a shallow copy. The copy constructor will look something like this: MyString::MyString(const MyString& source) : m_length { source.m_length } , m_data { source.m_data } { }
Copy Constructors And Assignment Operator in C++">Copy Constructors And Assignment Operator in C++
In practice, if you have a copy constructor you should have a copy assignment operator with a machting implementation. Other than that, I was wondering when we write our own copy constructors(ClassName (const ClassName &old_obj); or so).
Overloading the assignment operator – Learn C++">21.12 — Overloading the assignment operator – Learn C++
Copy assignment vs Copy constructor. The purpose of the copy constructor and the copy assignment operator are almost equivalent -- both copy one object to another. However, the copy constructor initializes new objects, whereas the assignment operator replaces the contents of existing objects.

Copy constructors and copy assignment operators (C++)

Compiler generated copy constructors

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Syntax of Copy Constructor in C++

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Example: Class Where a Copy Constructor is Required

What would be the problem if we remove the copy constructor from the above code?

When is the Copy Constructor Called?

Copy Elision

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Why argument to a copy constructor must be passed as a reference?

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Compiler generated copy constructors

21.12 — Overloading the assignment operator

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