copy-constructor

i am new to C++ programming, when i am doing some C++ programs i have got a doubt that is why copy constructor is called when i pass an object as argument by value to a function. please see my below code in that i am passing a object of class as an argument by value to a function display() but it calling copy constructor and then control is hitting the display() function but i am understanding why it so please help. #include "stdafx.h" #include <iostream> using namespace std; class ClassA { private: int a, b; public: ClassA() { a = 10, b = 20; } ClassA(ClassA &obj) { cout << "copy constructor

I am passing an unnamed temporary object to a function defined with const ref parameter. The copy ctor of the class is private, and I get a compilation error. I don't understand why a copy constructor is called in this situation. class A { public: A(int i) {} private: A(const A&) {} }; void f(const A& a) { } int main() { f(A(1)); // <-- error here: 'A::A(const A&)' is private } As expected, when I change the main to: A a(1); f(a); it works. EDIT: the compiler is gcc 4.1.2 etarion You can find the answer to your question in Copy Constructor Needed with temp object or go directly to http://gcc

Given a base class that is inherited by plethora of derived classes, and a program structure that requires you manage these via base class pointers to each entity. Is there a simple way to copy the entire derived object when only the base class pointer is known? Looking around it would seem possible (if incredibly tedious) to use the dynamic_cast call to check if a base pointer can be cast as the appropriate derived class, then copy it using the derived class's copy constructor. However this is not really an optimal solution partly due to the excessive use of dynamic_cast and also it would see

I searched around and seems in order to perform this I need to change my Base class and want to know if this is the best approach. For example, I have a Base class: class Base {} Then a long line of derived classes: class Derived_1:: public Base {} class Derived_2:: public Derived_1{} ... ... class Derived_n:: public Derived_M{} And then I have another class: class DeepCopy { Base * basePtr; public: DeepCopy(DeepCopy & dc) {} } Assuming the Base class and Derived_x class copy constructors are properly coded, what is the best way to write the copy constructor for DeepCopy. How can we know about

I understand that when we define a class copy constructor of the class is necessary as Rule of three states. I also notice that the argument of the copy constructor is usually const as the following codes illustrate: class ABC { public: int a; int b; ABC(const ABC &other) { a = other.a; b = other.b; } } My question is what would happen if the argument of the copy constructor is not const: class ABC { public: int a; int b; ABC(ABC &other) { a = other.a; b = other.b; } } I understand that in some cases if the argument of the copy constructor is const then the second implementation would fail.