Hi I’m building agame engine out of the book SDL Game Programming. I’m adding polymorphism to the engine in the chapter I’m doing at the moment but when I compile with $ g++ main.cpp -std=c++98 -fpermissive -Wall -lSDL2 -lSDL2_image
I get the error:
/tmp/ccGeKxTV.o: In function Enemy::Enemy()': main.cpp:(.text._ZN5EnemyC2Ev[_ZN5EnemyC5Ev]+0x1b): undefined reference tovtable for Enemy’
collect2: error: ld returned 1 exit status
can anyone tell me the cause of this obscure error and how to fix it?
Thanks.
Enemy.h
#ifndef __Enemy__
#define __Enemy__
#include "GameObject.h"
class Enemy : public GameObject
{
public:
void load(int x, int y, int width, int height, std::string textureID);
void draw(SDL_Renderer* pRenderer);
void update();
void clean();
};
#endif // defined __Enemy_h__
Enemy.cpp
#include "Enemy.h"
void Enemy::update()
{
m_y += 1;
m_x += 1;
m_currentFrame = int((SDL_GetTicks() / 100) % 6);
}
Game.h
#ifndef __Game__
#define __Game__
#include"GameObject.h"
class Game
{
public:
Game() {}
~Game() {}
bool init(const char* title, int xpos, int ypos, int width,
int height, bool fullscreen);
void render();
void update();
void handleEvents();
void clean();
void draw();
// a function to access the private running variable
bool running() {return m_bRunning;}
private:
std::vector<GameObject*> m_GameObjects;
GameObject* m_player;
GameObject* m_enemy1;
GameObject* m_enemy2;
GameObject* m_enemy3;
SDL_Window * m_pWindow;
SDL_Renderer * m_pRenderer;
SDL_Surface * pTempSurface;
int m_currentFrame;
bool m_bRunning;
};
GameObject * m_go;
GameObject * m_player;
#endif /* defined(__Game_h__) */
Game.cpp
#include "Game.h"
#include "Enemy.h"
#include "GameObject.h"
#include "Game.h"
bool Game::init(const char* title, int xpos, int ypos, int width,
int height, bool fullscreen)
{
m_player = new Player();
m_enemy1 = new Enemy();
m_enemy2 = new Enemy();
m_enemy3 = new Enemy();
m_GameObjects.push_back(m_player);
m_GameObjects.push_back(m_enemy1);
m_GameObjects.push_back(m_enemy2);
m_GameObjects.push_back(m_enemy3);
int flags = 0;
if (fullscreen)
{
flags = SDL_WINDOW_FULLSCREEN;
}
// attempt to initialize SDL
if(SDL_Init(SDL_INIT_EVERYTHING) == 0)
{
std::cout<<"SDL Init Success\n";
// init the window
m_pWindow = SDL_CreateWindow(title, xpos,
ypos,width,height,flags);
}
else
{
std::cout<<"Window Init Fail\n";
return false; //window init fail
}
if(m_pWindow != 0) //window init success
{
std::cout<<"Window Creation Success\n";
m_pRenderer = SDL_CreateRenderer(m_pWindow, -1, 0);
if(m_pRenderer !=0) // render init success
{
std::cout<<"Renderer Creation Success\n";
SDL_SetRenderDrawColor(m_pRenderer, 255,0,0,255);
}
else
{
std::cout<<"Renderer Init Fail\n";
return false; // renderer init fail
}
}
else
{
std::cout<<"SDL Init Fail\n";
return false; // SDL init fail
}
//to load
if(!TheTextureManager::Instance()->load("assets/animate-alpha.png","animate", m_pRenderer))
{
return false;
}
m_go = new GameObject();
m_player = new Player();
m_go->load(100,100,128,82, "animate");
m_player->load(300,300,128,82, "animate");
m_GameObjects.push_back(m_go);
m_GameObjects.push_back(m_player);
GameObject* m_enemy;
m_enemy = new Enemy();
m_enemy ->load(0,0,128,82,"animate");
m_GameObjects.push_back(m_enemy);
std::cout<<"Init success\n";
m_bRunning = true; // everything inited successfully
// start the main loop
return true;
}
void Game::render()
{
SDL_RenderClear(m_pRenderer);
// loop through our objects and draw them
for(std::vector<GameObject*>::size_type i =0; i!=m_GameObjects.size(); i++)
{
m_GameObjects[i]->draw(m_pRenderer);
}
//to draw
//TheTextureManager::Instance()->draw("animate",0,0, 128, 82, m_pRenderer);
//to animate
//TheTextureManager::Instance()->drawFrame("animate",100,100,128,82,1,m_currentFrame, m_pRenderer);
//m_go.draw(m_pRenderer);
//m_player.draw(m_pRenderer);
SDL_RenderPresent(m_pRenderer);
}
void Game::update()
{
//m_currentFrame = int(((SDL_GetTicks() / 100) % 6));
//m_go.update();
//m_player.update();
for(std::vector<GameObject*>::size_type i = 0; i != m_GameObjects.size(); i++)
{
m_GameObjects[i]->update();
}
}
void Game::clean()
{
std::cout<<"Cleaning game\n";
SDL_DestroyWindow(m_pWindow);
SDL_DestroyRenderer(m_pRenderer);
SDL_Quit();
}
void Game::handleEvents()
{
SDL_Event event;
if(SDL_PollEvent(&event))
{
switch (event.type)
{
case SDL_QUIT:
m_bRunning = false;
break;
}
}
}
void Game::draw()
{
for(std::vector<GameObject*>::size_type i = 0; i != m_GameObjects.size(); i++)
{
m_GameObjects[i]->draw(m_pRenderer);
}
}
GameObject.h
#ifndef __GameObject__
#define __GameObject__
//#include <SDL_image.h>
#include "TextureManager.h"
class GameObject
{
public:
virtual void load(int x, int y, int width, int height, std::string textureID);
virtual void draw(SDL_Renderer* pRenderer);
virtual void update();
virtual void clean();
protected:
std::string m_textureID;
int m_currentFrame;
int m_currentRow;
int m_x;
int m_y;
int width;
int height;
int m_width;
int m_height;
};
#endif /* defined(__GameObject_h__) */
GameObject.cpp
#include "GameObject.h"
void GameObject::load(int x, int y, int width, int height, std::string textureID)
{
m_x = x;
m_y = y;
m_width = width;
m_height = height;
m_textureID = textureID;
m_currentRow = 1;
m_currentFrame = 1;
}
void GameObject::draw(SDL_Renderer* pRenderer)
{
TextureManager::Instance()->drawFrame(m_textureID, m_x, m_y, m_width, m_height, m_currentRow,
m_currentFrame, pRenderer);
}
void GameObject::update()
{
m_x += 1;
}
void GameObject::clean()
{
// Do Something
}
main.cpp
#include <SDL2/SDL.h>
#include <SDL2/SDL_image.h>
#include <iostream>
#include <string>
#include <map>
#include <vector>
#include "TextureManager.h"
#include "TextureManager.cpp"
#include "GameObject.h"
#include "GameObject.cpp"
#include "Player.h"
#include "Player.cpp"
#include "Game.h"
#include "Game.cpp"
#include "Enemy.h"
#include "Enemy.cpp"
int main(int argc, char * args[])
{
Game * g_game = new Game;
g_game->init("Chapter 1", 100,100,640,480,false);
while(g_game->running())
{
g_game->handleEvents();
g_game->update();
g_game->render();
SDL_Delay(10);
}
g_game->clean();
return 0;
}
Player.h
#ifndef __Player__
#define __Player__
#include "GameObject.h"
class Player : public GameObject
{
public:
void load(int x, int y, int width, int height, std::string textureID);
void draw(SDL_Renderer* pRenderer);
void update();
void clean()
{
GameObject::clean();
std::cout<<"clean object\n";
}
};
#endif /*defined Player.h */
Player.cpp
#include "Player.h"
void Player::load(int x, int y, int width, int height, std::string textureID)
{
GameObject::load(x,y, width, height, textureID);
}
void Player::draw(SDL_Renderer* pRenderer)
{
GameObject::draw(pRenderer);
}
void Player::update()
{
m_x -=1;
}
TextureManager.h
#ifndef __TextureManager__
#define __TextureManager__
class TextureManager
{
public:
TextureManager(){}
bool load(std::string fileName, std::string id, SDL_Renderer* pRenderer);
//draw
void draw(std::string id, int x, int y, int width, int height, SDL_Renderer* pRenderer, SDL_RendererFlip flip = SDL_FLIP_NONE);
// drawframe
void drawFrame(std::string id, int x, int y, int width, int height, int currentRow, int currentFrame, SDL_Renderer* pRenderer, SDL_RendererFlip flip = SDL_FLIP_NONE);
std::map<std::string, SDL_Texture*> m_textureMap;
static TextureManager *s_pInstance;
static TextureManager* Instance()
{
if(s_pInstance == 0)
{
s_pInstance = new TextureManager();
return s_pInstance;
}
return s_pInstance;
}
private:
~TextureManager(){}
};
typedef TextureManager TheTextureManager;
#endif /* defined(__TextureManager_h__) */
TextureManager.cpp
#include "TextureManager.h"
TextureManager* TextureManager::s_pInstance = 0;
bool TextureManager::load(std::string fileName, std::string id, SDL_Renderer* pRenderer)
{
SDL_Surface* pTempSurface = IMG_Load(fileName.c_str());
if(pTempSurface == 0)
{
return false;
printf("IMG_Load Error %s\n", SDL_GetError());
}
else
{
std::cout <<"IMG_Load Success!\n";
}
SDL_Texture* pTexture =
SDL_CreateTextureFromSurface(pRenderer, pTempSurface);
SDL_FreeSurface(pTempSurface);
// everything went ok, add texture to our list
if(pTexture !=0)
{
m_textureMap[id] = pTexture;
return true;
}
// reaching here means something went wrong
return false;
}
void TextureManager::draw(std::string id, int x, int y, int width, int height, SDL_Renderer* pRenderer, SDL_RendererFlip flip)
{
SDL_Rect srcRect;
SDL_Rect destRect;
srcRect.x =0;
srcRect.y =0;
srcRect.w = destRect.w = width;
srcRect.h = destRect.h = height;
destRect.x =x;
destRect.y =y;
SDL_RenderCopyEx(pRenderer, m_textureMap[id], &srcRect, &destRect, 0, 0, flip);
}
void TextureManager::drawFrame(std::string id, int x, int y, int width, int height, int currentRow,
int currentFrame, SDL_Renderer *pRenderer, SDL_RendererFlip flip)
{
SDL_Rect srcRect;
SDL_Rect destRect;
srcRect.x = width * currentFrame;
srcRect.y = height * (currentRow -1);
srcRect.w = destRect.w = width;
srcRect.h = destRect.h = height;
destRect.x = x;
destRect.y = y;
SDL_RenderCopyEx(pRenderer, m_textureMap[id], &srcRect, &destRect, 0,0, flip);
}