Why copy constructor is required

Direct initialization. Aggregate initialization. Constant initialization. Reference initialization. Value categories. Order of evaluation. Operator precedence. Alternative representations. Boolean - Integer - Floating-point. Implicit conversions - Explicit conversions. Class declaration. Access specifiers. Virtual function. Default constructor. Copy assignment. Class template. Function template. Template specialization.

Data members. The this pointer. Nested classes. Member templates. Member functions. Member access specifiers. Constructors and member initializer lists. Converting constructor. Copy assignment operator. Base and derived classes. This is what happens in shallow copy constructor.

Both objects will point to same memory location. Shallow copy copies references to original objects. The compiler provides a default copy constructor. Default copy constructor provides a shallow copy as shown in below example. It is a bit-wise copy of an object. Shallow copy constructor is used when class is not dealing with any dynamically allocated memory.

In the below example you can see both objects, c1 and c2, points to same memory location. When c1. So both c1. Let's consider an example for explaining deep copy constructor. You are supposed to submit an assignment tomorrow and you are running short of time, so you copied it from your friend. Now you and your friend have same assignment content, but separate copies. Therefore any modifications made in your copy of assignment will not be reflected in your friend's copy.

This is what happens in deep copy constructor. Deep copy allocates separate memory for copied information. So the source and copy are different. In user defined copy constructor, we make sure that pointers or references of copied object point to new memory locations.

Copy constructor vs Assignment Operator Which of the following two statements call copy constructor and which one calls assignment operator? Assignment operator is called when an already initialized object is assigned a new value from another existing object. In the above example 1 calls copy constructor and 2 calls assignment operator. See this for more details.

Write an example class where copy constructor is needed? In the following String class, we must write copy constructor. The changes made to str2 reflect in str1 as well which is never expected. 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 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? A copy constructor is called when an object is passed by value.

Copy constructor itself is a function. So if we pass an argument by value in a copy constructor, a call to copy constructor would be made to call copy constructor which becomes a non-terminating chain of calls. Why argument to a copy constructor should be const?