What is a copy constructor in C++?

Question

On page 6 of Scott Meyers's Effective C++, the term 'copy constructor' is defined. I've been using Schiltdt's book as my reference and I can find no mention of copy constructors. I get the idea but is this a standard part of c++? Will such constructors get called when a pass a class by value?

Answer 1

A copy constructor is a constructor which does deep copy. You should write your own copy constructor when there is a pointer type variable inside the class. Compiler will insert copy constructor automatically when there is no explicit copy constructor written inside the code. The type of a copy constructor parameter should always be reference type, this to avoid infinite recursion due to the pass by value type.

below program explains the use of copy constructor

#include <iostream>
#pragma warning(disable : 4996)
using namespace std;
class SampleTest {
private:
    char* name;
    int age;
public:   
    SampleTest(char *name1, int age) {
        int l = strlen(name1);
        name = new char[l + 1];
        strcpy(this->name, name1);
        this->age = age;
    }
        SampleTest(const SampleTest& s) { //copy constructor 
            int l = strlen(s.name);
            name = new char[l + 1];
            strcpy(this->name, s.name);
            this->age = s.age;
        }
    void displayDetails() {
        cout << "Name is " << this->name << endl;
        cout << "Age is " << this->age << endl;
    }
    void changeName(char* newName) {
        int l = strlen(newName);
        name = new char[l + 1];
        strcpy(this->name, newName);
    }
};
int main() {
    SampleTest s("Test", 10);
    s.displayDetails();
    SampleTest s1(s);
    cout << "From copy constructor" << endl;
    s1.displayDetails();
    s1.changeName("Test1");
    cout << "after changing name s1:";
    s1.displayDetails();
    s.displayDetails();
    cin.get();
    return 0;
}