致命错误LNK1169:在游戏编程中发现一个或多个乘法定义符号
fatal error LNK1169: one or more multiply defined symbols found in game programming
我一直在训练在c++中使用面向对象编程，但我一直得到这个错误:
1>main.obj : error LNK2005: "int WIDTH" (?WIDTH@@3HA) already defined in GameObject.obj
1>main.obj : error LNK2005: "int HEIGHT" (?HEIGHT@@3HA) already defined in GameObject.obj
1>Spaceship.obj : error LNK2005: "int WIDTH" (?WIDTH@@3HA) already defined in GameObject.obj
1>Spaceship.obj : error LNK2005: "int HEIGHT" (?HEIGHT@@3HA) already defined in GameObject.obj
1>C:Usersteddocumentsvisual studio 2010ProjectsfullSpaceDebugfullSpace.exe : fatal error LNK1169: one or more multiply defined symbols found
然而，对我来说，整个代码似乎写得很好，两个int只在Global头中提到，所有对象似乎都继承得很好。然而，就像我刚才说的，我是一个面向对象的初学者，所以我真的需要一个意见:值得一提的是，我正在使用allegro 5来创建一个侧面射击游戏。
这是代码:
(主要):
#include <allegro5/allegro.h>
#include <allegro5/allegro_image.h>
#include <allegro5/allegro_primitives.h>
#include <allegro5/allegro_font.h>
#include <allegro5allegro_ttf.h>
#include <allegro5allegro_audio.h>
#include <allegro5allegro_acodec.h>
#include <list>
#include "GameObject.h"
#include "Spaceship.h"
#include "Globals.h"
//controls
bool keys[] = {false, false, false, false, false};
enum KEYS{UP, DOWN, LEFT, RIGHT, SPACE};
//globals
Spaceship *ship;
std::list <GameObject *> objects;
std::list <GameObject *>::iterator iter;
std::list <GameObject *>::iterator iter2;
//prototypes
//main function
int main(int argc, char **argv)
{
//shell variables
bool done = false;
bool render = false;
float gameTime = 0;
int frames = 0;
int gameFPS = 0;
//project variables
ship = new Spaceship();
ALLEGRO_BITMAP *shipImage = NULL;
ALLEGRO_BITMAP *cometImage= NULL;
ALLEGRO_BITMAP *explImage = NULL;
ALLEGRO_BITMAP *bgImage = NULL;
ALLEGRO_BITMAP *mgImage = NULL;
ALLEGRO_BITMAP *plImage = NULL;
ALLEGRO_BITMAP *mgImage2 = NULL;
ALLEGRO_BITMAP *fgImage = NULL;
ALLEGRO_BITMAP *titleImage= NULL;
ALLEGRO_BITMAP *lostImage = NULL;
//allegro variables
ALLEGRO_DISPLAY *display = NULL;
ALLEGRO_EVENT_QUEUE *event_queue = NULL;
ALLEGRO_TIMER *timer;
ALLEGRO_FONT *font18;
//initiate variables
if(!al_init())
return -1;
display = al_create_display(WIDTH, HEIGHT);
if(!display)
return -1;
//addon installation
al_install_keyboard();
al_init_image_addon();
al_init_font_addon();
al_init_ttf_addon();
al_init_primitives_addon();
al_install_audio();
al_init_acodec_addon();
//project init
font18 = al_load_font("arial.ttf", 18, 0);
al_reserve_samples(15);
bgImage = al_load_bitmap("layer1.png");
mgImage = al_load_bitmap("layer2.png");
plImage = al_load_bitmap("starMG.png");
mgImage2 = al_load_bitmap("layer3.png");
fgImage = al_load_bitmap("layer4.png");
shipImage = al_load_bitmap("spaceship.png");
al_convert_mask_to_alpha(shipImage, al_map_rgb(255, 0, 255));
cometImage = al_load_bitmap("asteroid-1-96.png");
explImage = al_load_bitmap("explosion_3_40_128.png");
titleImage = al_load_bitmap("Shooter_Title.png");
lostImage = al_load_bitmap("Shooter_Lose.png");
//object init
ship->init(shipImage);
//iter list
objects.push_back(ship);
srand(time(NULL));
//timer init and startup
event_queue = al_create_event_queue();
timer = al_create_timer(1.0 / 60);
al_register_event_source(event_queue, al_get_timer_event_source(timer));
al_register_event_source(event_queue, al_get_keyboard_event_source());
al_start_timer(timer);
gameTime = al_current_time();
while(!done)
{
ALLEGRO_EVENT ev;
al_wait_for_event(event_queue, &ev);
//input
if(ev.type == ALLEGRO_EVENT_KEY_DOWN)
{
switch(ev.keyboard.keycode)
{
case ALLEGRO_KEY_ESCAPE:
done = true;
break;
case ALLEGRO_KEY_LEFT:
keys[LEFT] = true;
break;
case ALLEGRO_KEY_RIGHT:
keys[RIGHT] = true;
break;
case ALLEGRO_KEY_UP:
keys[UP] = true;
break;
case ALLEGRO_KEY_DOWN:
keys[DOWN] = true;
break;
case ALLEGRO_KEY_SPACE:
keys[SPACE] = true;
break;
}
} else if(ev.type == ALLEGRO_EVENT_KEY_UP)
{
switch(ev.keyboard.keycode)
{
case ALLEGRO_KEY_ESCAPE:
done = true;
break;
case ALLEGRO_KEY_LEFT:
keys[LEFT] = false;
break;
case ALLEGRO_KEY_RIGHT:
keys[RIGHT] = false;
break;
case ALLEGRO_KEY_UP:
keys[UP] = false;
break;
case ALLEGRO_KEY_DOWN:
keys[DOWN] = false;
break;
case ALLEGRO_KEY_SPACE:
keys[SPACE] = false;
break;
}
}
else if (ev.type == ALLEGRO_EVENT_TIMER)
{
render = true;
//fps
frames++;
if(al_current_time() - gameTime >= 1)
{
gameTime = al_current_time();
gameFPS = frames;
frames = 0;
}
//shipUpdate
if(keys[UP])
ship ->moveUp();
else if(keys[DOWN])
ship ->moveDown();
else
ship->resetAnim(1);
if(keys[LEFT])
ship ->moveLeft();
else if(keys[RIGHT])
ship -> moveRight();
else
ship ->resetAnim(0);
}
//render
if(render && al_is_event_queue_empty(event_queue))
{
render = false;
//begin render
for(iter = objects.begin(); iter != objects.end(); ++iter)
(*iter)->render();
//Flip Buffers
al_flip_display();
al_clear_to_color(al_map_rgb(0,0,0));
}
}
//destroy objects
//visual objects
al_destroy_bitmap(cometImage);
for(iter = objects.begin(); iter != objects.end(); ++iter)
(*iter)->destroy(shipImage);
iter = objects.erase(iter);
al_destroy_bitmap(explImage);
al_destroy_bitmap(bgImage);
al_destroy_bitmap(mgImage);
al_destroy_bitmap(fgImage);
al_destroy_bitmap(titleImage);
al_destroy_bitmap(lostImage);
//audio objects
/*
al_destroy_sample(shot);
al_destroy_sample(boom);
al_destroy_sample(song);
al_destroy_sample_instance(songInstance);
*/
//shell objects
al_destroy_font(font18);
al_destroy_timer(timer);
al_destroy_event_queue(event_queue);
al_destroy_display(display);
return 0;
}
(上面):
#pragma once
int WIDTH = 1024;
int HEIGHT = 800;
enum ID{PLAYER, ENEMY, BULLET, BORDER, MISC};
enum STATES{TITLE, PLAYING, LOST};
(GameObject.h):
#pragma once
#include "Globals.h"
#include <iostream>
#include <allegro5/allegro5.h>
#include <allegro5/allegro_primitives.h>
class GameObject
{
private:
int ID;
bool alive;
bool collidable;
protected:
float x;
float y;
float velX;
float velY;
int dirX;
int dirY;
int boundX;
int boundY;
int maxFrame;
int curFrame;
int frameCount;
int frameDelay;
int frameWidth;
int frameHeight;
int animationColumns;
int animationDirection;
ALLEGRO_BITMAP *image;
public:
GameObject();
void virtual destroy(ALLEGRO_BITMAP *image);
void init(float x, float y, float velX, float velY, int dirX, int dirY, int boundX, int boundY);
void virtual update();
void virtual render();
float getX() {return x;}
float getY() {return y;}
void setX(float x) {GameObject::x = x;}
void setY(float y) {GameObject::y = y;}
int getBoundX() {return boundX;}
int getBoundY() {return boundY;}
int getID() {return ID;}
void setID(int ID) {GameObject::ID = ID;}
bool getAlive() {return alive;}
void setAlive(bool alive) {GameObject::alive = alive;}
bool getCollidable() {return collidable;}
void setCollidable(bool collidable) {GameObject::collidable = collidable;}
bool checkCollisions(GameObject *otherObject);
void virtual collided(int objectID);
bool collidableCheck();
};
(GameObject.cpp):
#include "GameObject.h"
GameObject::GameObject()
{
x = 0;
y = 0;
velX = 0;
velY = 0;
dirX = 0;
dirY = 0;
boundX = 0;
boundY = 0;
maxFrame = 0;
curFrame = 0;
frameCount = 0;
frameDelay = 0;
frameWidth = 0;
frameHeight = 0;
animationColumns = 0;
animationDirection = 0;
image = NULL;
alive = true;
collidable = true;
}
void GameObject::destroy(ALLEGRO_BITMAP *image)
{
if(image != NULL)
al_destroy_bitmap(image);
}
void GameObject::init(float x, float y, float velX, float velY, int dirX, int dirY, int boundX, int boundY)
{
GameObject::x = x;
GameObject::y = y;
GameObject::velX = velX;
GameObject::velY = velY;
GameObject::dirX = dirX;
GameObject::dirY = dirY;
GameObject::boundX = boundX;
GameObject::boundY = boundY;
}
void GameObject::update()
{
x += velX*dirX;
y += velY*dirY;
}
void GameObject::render()
{
}
bool GameObject::checkCollisions(GameObject *otherObject)
{
float oX = otherObject->getX();
float oY = otherObject->getY();
int obX = otherObject->getBoundX();
int obY = otherObject->getBoundY();
if(x + boundX > oX - obX &&
x - boundX < oX + obX &&
y + boundY > oY - obY &&
y - boundY < oY + obY
)
return true;
else
return false;
}
void GameObject::collided(int objectID)
{
}
bool GameObject::collidableCheck()
{
return alive && collidable;
}
(SpaceShip.h):
#pragma once
#include "GameObject.h"
class Spaceship : public GameObject
{
private :
int lives;
int score;
int animationRow;
public :
Spaceship();
void destroy(ALLEGRO_BITMAP *image);
void init(ALLEGRO_BITMAP *image = NULL);
void update();
void render();
void moveUp();
void moveDown();
void moveLeft();
void moveRight();
void resetAnim(int pos);
int getLives(){return lives;}
int getScore() {return score;}
void looseLife() {lives--;}
void addPoint() {score++;}
void collide(int objectID);
};
(SpaceShip.cpp):
#include "Spaceship.h"
Spaceship::Spaceship()
{}
void Spaceship::destroy(ALLEGRO_BITMAP *image)
{
GameObject::destroy(image);
}
void Spaceship::init(ALLEGRO_BITMAP *image)
{
GameObject::init(20, 200, 6, 6, 0, 0, 10, 12);
setID(PLAYER);
setAlive(true);
lives = 3;
score = 0;
maxFrame = 3;
curFrame = 0;
frameWidth = 46;
frameHeight = 41;
animationColumns = 3;
animationDirection = 1;
animationRow = 1;
if(image != NULL)
{
Spaceship::image = image;
}
}
void Spaceship::update()
{
GameObject::update();
if(x < 0)
x=0;
else if ( x > WIDTH)
x = WIDTH;
if(y < 0)
y = 0;
else if (y > HEIGHT)
y = HEIGHT;
}
void Spaceship::render()
{
GameObject::render();
int fx = (curFrame % animationColumns) *frameWidth;
int fy = animationRow *frameHeight;
al_draw_bitmap_region(image, fx, fy, frameWidth, frameHeight,
x - frameWidth /2, y - frameHeight /2, 0);
}
void Spaceship::moveUp()
{
animationRow = 0;
dirY = -1;
}
void Spaceship::moveDown()
{
animationRow = 2;
dirY = 1;
}
void Spaceship::moveLeft()
{
curFrame = 2;
dirX = -1;
}
void Spaceship::moveRight()
{
curFrame = 1;
dirX = 1;
}
void Spaceship::resetAnim(int pos)
{
if(pos == 1)
{
animationRow = 1;
dirY = 0;
}
else
{
curFrame = 0;
dirX = 0;
}
}
void Spaceship::collide(int objectID)
{
if(objectID == ENEMY)
lives--;
}
两个int变量在头文件中定义。这意味着每个包含头文件的源文件都将包含它们的定义(头文件包含是纯文本的)。这当然会导致多重定义错误。
你有几个选项来解决这个问题。
-
使变量为
static(static int WIDTH = 1024;)。它们仍然存在于每个源文件中，但是它们的定义在源文件之外将不可见。 -
使用
extern(extern int WIDTH;)将它们的定义转换为声明，并将定义放入一个源文件:int WIDTH = 1024;. -
可能是最好的选择:使变量
const(const int WIDTH = 1024;)。这使得它们隐式地成为static，并且还允许它们被用作编译时常量，允许编译器直接使用它们的值，而不是发出代码从变量中读取它等。
你不能把变量定义放在头文件中，因为它们将成为你包含头文件的所有源文件的一部分。
#pragma once只是为了防止同一源文件中的多个包含，而不是防止多个源文件中的多个包含。
您可以在头文件中将变量声明为extern，然后在单个源文件中定义它们。或者您可以在头文件中将变量声明为const，然后编译器和链接器将管理它
我在这里回答了一个类似的问题。
在项目设置中，将/FORCE:MULTIPLE添加到链接器的命令行选项中。
从MSDN: "使用/FORCE:MULTIPLE创建一个输出文件，无论LINK是否为一个符号找到多个定义。"
这就是程序员所说的"快速和肮脏"。解决方案，但有时你只是想完成构建，稍后再解决问题，所以这是一种临时解决方案。要实际避免此错误，只要您想要
int WIDTH = 1024;
int HEIGHT = 800;
要在多个源文件中共享，只需在单个.c/.cpp文件中声明它们，并在头文件中引用它们:
extern int WIDTH;
extern int HEIGHT;
然后将头文件包含在您希望这些全局变量可用的任何其他源文件中。
const int WIDTH = 1024;
const int HEIGHT = 800;
在我的情况下，我得到了错误消息one or more multiply defined symbols found，我发现另一个错误消息显示xxx function is already defined in ooo.dll，但在我的项目中根本没有引用ooo.dll。
然后我记得我之前使用vcpkg可能全局安装ooo.dll，所以使用vcpkg删除卸载ooo.dll package，然后重新构建，错误解决了，构建成功。
只需添加/FORCE作为链接标志，就可以了。
例如，如果您正在编写CMakeLists.txt。然后添加以下行:
SET(CMAKE_EXE_LINKER_FLAGS "/FORCE")
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