C++ SDL: Undefined reference to Game::Game()?

This is a discussion on C++ SDL: Undefined reference to Game::Game()? within the C++ Programming forums, part of the General Programming Boards category; I'm reading the book SDL Game Development. And where going to do this step. And then I'm got stuck my ...

  1. #1
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    C++ SDL: Undefined reference to Game::Game()?

    I'm reading the book SDL Game Development. And where going to do this step. And then I'm got stuck my compiler complained about that Game::Game() was undefined? And I'm not really sure what's wrong?

    I know that I have both main.cpp and Game.h in the same directory so it cannot be that, that is wrong.

    What does a "undefined reference" error even mean?


    The main.cpp file
    Code:
    #include <iostream>
    #include "SDL.h"
    #include "Game.h"
    
    
    using namespace std;
    
    
    Game *g_game = 0;
    
    
    int main(int argc, char* argv[])
    {
        g_game = new Game();
        return 0;
    }
    The Game.h file
    Code:
    #ifndef GAME_H_INCLUDED
    #define GAME_H_INCLUDED
    
    
    class Game
    {
        public:
            Game();
            ~Game();
    
    
            // Initialize
            void init() {m_bRunning = true;}
    
    
    
    
            void render() {}
            void update() {}
            void handleEvents() {}
    
    
            // To access the private running variable
            bool running() {return m_bRunning;}
    
    
        private:
            bool m_bRunning;
    };
    
    
    #endif // GAME_H_INCLUDED

  2. #2
    C++ Witch laserlight's Avatar
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    Where did you define the member functions of the Game class? Maybe it is that source file that was not included in the project, or otherwise compiled and linked.
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    In the main.cpp file. Is all of the member functions of the Game class. But I find that I don't have to use yet: g_game = new Game(); But however I have included the member functions in the main.cpp file. Should I create a Game.cpp file for the constructor and deconstructor? To initialize them?

  4. #4
    C++ Witch laserlight's Avatar
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    Quote Originally Posted by DecoratorFawn82
    In the main.cpp file. Is all of the member functions of the Game class.
    Since you did not show that part of your main.cpp file, I find it plausible that you may be mistaken, e.g., you forgot to define the default constructor.

    Quote Originally Posted by DecoratorFawn82
    But I find that I don't have to use yet: g_game = new Game();
    What do you mean?

    Quote Originally Posted by DecoratorFawn82
    Should I create a Game.cpp file for the constructor and deconstructor? To initialize them?
    We say "define", not "initialize" here. Also, "destructor", not "deconstructor". Anyway, I would likely have a separate game.cpp file for all the member function definitions of the Game class (at least those member functions that were not defined inline in the class definition), not just the constructor and destructor.
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  5. #5
    Registered User rogster001's Avatar
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    What does a "undefined reference" error even mean?
    If you don't know what that might be telling you then i think you might be running before you can walk.

    The definition of the constructor (or other functions) is the working code that defines what your function does - You could if you really wanted write it into the class without adding it to another source file, i would not do that very often personally but you do see this in tutorials about class basics for example. Also a constructor is special in that if you don't define one then a default is provided for you.
    Last edited by rogster001; 09-24-2013 at 12:04 PM.
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    OK thanks! And sorry if I'm used wrong words or spelled any words wrong. But you got what I mean however

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