C + +: The default constructor of a derived class and the mechanism by which the copy constructor calls the base class constructor (with program validation)

1. If the base class defines a default constructor with no parameters, the default constructor that the compiler automatically generates for the derived class invokes the default constructor for the base class.

2. If the base class defines a copy constructor, the copy constructor that the compiler automatically generates for the derived class also calls the copy constructor of the base class.

3, if the base class defines a constructor with parameters, the derived class does not define any constructors with parameters, you cannot call the parameter constructor of the base class directly, and the program compiles without passing.

The code is as follows:

#include <iostream>using namespace std;

Base class Game, which defines two constructors and a copy constructor class Game{public:game () {cout<< "constructor: Game () \ n";} Game (const game& game) {cout<< "copy constructor: Game (const game& game) \ n";} Game (int i) {cout<< "game (int i) \ n";}};/ /derived class Chess, no constructors and copy constructors are defined class Chess:public Game{};int main () {Chess ch1; Chess CH2 (CH1);//chess CH3 (1);cout<< "End!"; int I;cin>>i;return 0;}

The results of the operation are as follows:

If you do not comment out the " Chess CH3 (1) "This line, which calls the constructor with parameters directly, will cause an error: there is no constructor "Chess::chess" instance that matches the argument list, so the 3rd conclusion is validated.

C + +: The default constructor of a derived class and the mechanism by which the copy constructor calls the base class constructor (with program validation)