c++ - 正在解决错误 LNK2019；未解析的外部符号

Question

我使用 SDL 编写了这段代码，但存在一些错误。

这是代码

#include <SDL.h>
#include <SDL_image.h>
#include <SDL_ttf.h>
#include <SDL_mixer.h>
#include <fstream>
#include <iostream>
using namespace std;


///////////////////////////////////    functions & global variable   ////////////////////////////////

SDL_Window* window;
SDL_Renderer* renderer;
SDL_Color textColor;
TTF_Font* font;
SDL_Surface* surface=SDL_GetWindowSurface(window);
SDL_Event event;




SDL_Texture* LoadTexture(char* path)
{
    SDL_Surface* surface = IMG_Load(path);
    SDL_Texture* texture = SDL_CreateTextureFromSurface(renderer,surface);
    SDL_FreeSurface(surface);
    return texture;
}



/////////////////////////////////////  Cell  /////////////////////////////////////

class Cell
{
private:
    char num;

public:
    Cell();
    Cell(int ,int ,char);
    char * img;
    pair <int ,int> cor;
    int flag;
    int size;
    void display();
    bool indomain(int ,int);
};


Cell :: Cell(int x ,int y ,char n){
    num=n;
    cor.first=x;
    cor.second=y;
    size=40;
    flag=0;
    if (num == '#')
        img="0.png";
    else if (num == '!')
        img="1.png";
    else
        img="street.png";
}

bool Cell :: indomain(int x ,int y){
    if ( (cor.first<=x && x<=cor.first+size) && (cor.second<=y && y<=cor.second+size))
        return true;
    return false;
}


void Cell :: display(){
    SDL_Rect rect;
    rect.x=cor.first;
    rect.y=cor.second;
    SDL_Texture* texture = LoadTexture(img);
    SDL_RenderCopy(renderer,texture,NULL,&rect);
}


////////////////////////////////////////////   Tower   /////////////////////////////////////////

class Tower
{
public:
    Tower();
    Tower(int ,int ,int ,int ,char* ,int ,int ,int);
    ~Tower();
    int price;
    int up_cost;
    char * img;
    int power;
    int domain;
    int grade;
    int index;
    pair <int ,int> cor;
    void upgrade();
    void display();
    bool mark(int ,int);
};


Tower :: Tower(int pr ,int co ,int pow ,int dom ,char* im ,int x ,int y ,int i){
    price=pr;
    up_cost=co;
    power=pow;
    domain=dom;
    img=im;
    cor.first=x;
    cor.second=y;
    grade=1;
    index=i;
}

void Tower :: upgrade(){
    if (grade<5)
    {
        grade+=1;
        power*=2;
        domain*=1.2;
        price*=1.2;
    }
}

void Tower :: display(){
    SDL_Rect rect;
    rect.x=cor.first;
    rect.y=cor.second;
    SDL_Texture* texture = LoadTexture(img);
    SDL_RenderCopy(renderer,texture,NULL,&rect);
}   

bool Tower :: mark(int x, int y){
    if ((cor.first<=x && x<=cor.first+40) && (cor.second<=y && x<=cor.second+80))
        return true;
    return false;
}





////////////////////////////////   Enemy   //////////////////////////////////////

class Enemy
{
public:
    Enemy();
    Enemy(int ,char* ,int ,int ,int);
    ~Enemy();
    char * img;
    int health;
    int cellNum;
    int index;
    pair <int ,int> cor;
    bool live();
    void display();
    void damge(Tower t);
};


Enemy :: Enemy(int h ,char* im ,int x ,int y ,int i){
    health=h;
    img=im;
    cor.first=x;
    cor.second=y;
    cellNum=0;
    index=i;
}

bool Enemy :: live(){
    if (health>0) 
        return true;
    return false;
}

void Enemy :: damge(Tower t){
    health-=t.power;
}

void Enemy :: display(){
    SDL_Rect rect;
    rect.x=cor.first;
rect.y=cor.second;
SDL_Texture* texture = LoadTexture(img);
SDL_RenderCopy(renderer,texture,NULL,&rect);
}




/////////////////////////////////////////////  Map  ///////////////////////////////////////

class Map
{
private:
char * file;
int len;

public:
Map();
Map(char* ,int);
~Map();
Cell map[15][20];
pair <int ,int> * path;
void display();
void put_tower(Tower ,Cell);
void put_enemy(Enemy ,Cell);
void remove(Cell);
void enemyMove(Enemy);
void pathFinder(int);
};


Map :: Map(char * f ,int l){
file=f;
len=l;
ifstream infile;
infile.open(file);
char * line=new char;
for (int i=0;i<15;i++)
{
    infile >> line;
    for (int j=0;j<20;j++)
        map[i][j]=Cell(j*40 ,i*40 ,line[j]);
}
this->pathFinder(len);
}

void Map :: put_enemy(Enemy e ,Cell c){
e.cor=c.cor;
e.display();
}

void Map :: put_tower(Tower t ,Cell c){
t.cor=c.cor;
t.display();
}

void Map :: remove(Cell c){
c.display();
}

void Map :: enemyMove(Enemy e){
e.cellNum+=1;
e.cor=path[e.cellNum];
}

void Map :: pathFinder(int l){
path=new pair<int ,int> [l];
ifstream infile;
infile.open(file);
char ** lines=new char* [15];
for (int i=0;i<15;i++)
    infile >> lines[i];
for (int i=0;i<20;i++)
    if (lines[0][i]=='0')
    {
        path[0]=make_pair(0,i);
        break;
    }
int x=0;
int y=path[0].second;
int ord=48;
for (int i=1;i<l;i++)
{
    if (int(lines[x-1][y])==((ord-47)%10)+48)
        x-=1;
    else if (int(lines[x+1][y])==((ord-47)%10)+48)
        x+=1;
    else if (int(lines[x][y-1])==((ord-47)%10)+48)
        y-=1;
    else if (int(lines[x][y+1])==((ord-47)%10)+48)
        y+=1;
    path[i]=make_pair(x,y);
    ord+=1;
}
}

void Map :: display(){
for (int i=0;i<15;i++)
    for (int j=0;j<20;j++)
        map[i][j].display();
}





////////////////////////////////////////////////////   Game   ////////////////////////////////////////

class Game
{
private:
int health;
int money;
int score;
int step;

public:
Game(int ,int);
~Game();
bool End;
int enemyNum;
int towerNum;
Enemy enemys[20];
Tower towers[50];
int getHealth();
int getMoney();
int getScore();
int getStep();
void setHealth(int);
void setMoney(int);
void setScore(int);
void setStep(int);
void distroy_enemy(Enemy ,Cell);
void distroy_tower(Tower ,Cell);
void shooting(Tower);
void drag_drop(Tower);
void upgradeTower(Tower);
void buyTower(Tower);
void sellTower(Tower ,Cell);
void display(Map);
void displayMenu();
void endDisplay();
bool checkEnd();
void animation();
};

Game :: Game(int h ,int m){
health=h;
money=m;
step=1;
score=0;
enemyNum=0;
towerNum=0;
End=false;
}

int Game :: getHealth(){
return health;
}
int Game :: getMoney(){
return money;
}

int Game :: getScore(){
return score;
}

int Game :: getStep(){
return step;
}

void Game :: setHealth(int h){
health=h;
}

void Game :: setMoney(int m){
money=m;
}

void Game :: setScore(int s){
score=s;
}

void Game :: setStep (int s){
step=s;
}

void Game :: distroy_enemy(Enemy e,Cell c){
for (int i=e.index;i<enemyNum-1;i++)
    enemys[i]=enemys[i+1];
enemyNum-=1;
c.display();
}

void Game :: distroy_tower(Tower t ,Cell c){
for (int i=t.index;i<towerNum-1;i++)
    towers[i]=towers[i+1];
towerNum-=1;
c.display();
}

void Game :: shooting(Tower t){
for(int i=0;i<enemyNum;i++)
{
    if (sqrt(pow(enemys[i].cor.first,2)+pow(enemys[i].cor.second,2)) <= t.domain)
        enemys[i].health-=t.power;
}
}

void Game :: upgradeTower(Tower t){
t.upgrade();
money-=t.up_cost;
}

void Game :: buyTower(Tower t){
money-=t.price;
towers[towerNum]=t;
towerNum+=1;
t.display();
}

void Game :: sellTower(Tower t ,Cell c){
distroy_tower(t,c);
money+=t.price/2;
}

void Game :: endDisplay(){
End=true;
SDL_FillRect(surface,&surface->clip_rect,SDL_MapRGB(surface->format,0XFF,0XFF,0XFF));
SDL_Surface* text;
font=TTF_OpenFont("AV.TTF",40);
textColor.b=20;
textColor.g=10;
textColor.r=0;
if (health<=0)
{
    text=TTF_RenderText_Solid(font ,"You lose" ,textColor);
}
else if (health>0)
{
    text=TTF_RenderText_Solid(font ,"Complete the mission" ,textColor);
}
SDL_Rect rect;
rect.x=300;
rect.y=300;
SDL_BlitSurface(text,NULL,surface,&rect);
}

bool Game :: checkEnd(){
if (health<=0 || step==20)
    return true;
return false;
}    

void Game :: displayMenu(){
SDL_Rect rect;
rect.x=800;
rect.y=0;
SDL_Texture* texture = LoadTexture("menu.png");
SDL_RenderCopy(renderer,texture,NULL,&rect);
}


void Game :: display(Map m){
m.display();
for (int i=0;i<towerNum;i++)
    towers[i].display();
for (int i=0;i<enemyNum;i++)
    enemys[i].display();
this->displayMenu();
/////////// ttf
}

void Game :: animation(){
SDL_Rect Lrect;
Lrect.x=83;
Lrect.y=0;
SDL_Rect Rrect;
Rrect.x=915;
Rrect.y=0;
SDL_Texture* leftpic = LoadTexture("left.png");
SDL_Texture* rightpic = LoadTexture("right.png");
for (int i=0;i<12;i++)
{
    SDL_RenderCopy(renderer,leftpic,NULL,&Lrect);
    SDL_RenderCopy(renderer,rightpic,NULL,&Rrect);
    Rrect.x-=20;
    Lrect.x+=60;
    SDL_RendererFlip();
    SDL_Delay(300);
}
}





//////////////////////////////////////////////////////////////    main    //////////////////////////////////////////////////////////////////////


int main()
{
window=SDL_CreateWindow("Frontline Defence",SDL_WINDOWPOS_UNDEFINED,
    SDL_WINDOWPOS_UNDEFINED,940,600,SDL_WINDOW_SHOWN);
Game game(1000,500);
Map map("map.txt",30);
while ( !game.checkEnd() )
    {
        if ( SDL_PollEvent(&event))
        {
            if (event.type == SDL_QUIT)
                return 0;
            if (event.type == SDL_MOUSEBUTTONDOWN )
            {
                SDL_Delay(3000);
            }
        }
    }
    game.endDisplay();
    return 0;
}

我已尽我所能，但没有任何改变!我试过包括库、在主文件中输入代码的所有部分以及许多其他方法，但没有帮助

这些是错误:

Error   12  error LNK1120: 8 unresolved externals   C:\Users\FUJITSU\Desktop\frontline defence\project\ConsoleApplication1\Debug\ConsoleApplication1.exe    ConsoleApplication1
Error   4   error LNK2019: unresolved external symbol "public: __thiscall Cell::Cell(void)" (??0Cell@@QAE@XZ) referenced in function "public: __thiscall Map::Map(char *,int)" (??0Map@@QAE@PADH@Z) C:\Users\FUJITSU\Desktop\frontline defence\project\ConsoleApplication1\ConsoleApplication1\classes.obj  ConsoleApplication1
Error   8   error LNK2019: unresolved external symbol "public: __thiscall Enemy::~Enemy(void)" (??1Enemy@@QAE@XZ) referenced in function "public: __thiscall Game::Game(int,int)" (??0Game@@QAE@HH@Z)   C:\Users\FUJITSU\Desktop\frontline defence\project\ConsoleApplication1\ConsoleApplication1\classes.obj  ConsoleApplication1
Error   7   error LNK2019: unresolved external symbol "public: __thiscall Enemy::Enemy(void)" (??0Enemy@@QAE@XZ) referenced in function "public: __thiscall Game::Game(int,int)" (??0Game@@QAE@HH@Z)    C:\Users\FUJITSU\Desktop\frontline defence\project\ConsoleApplication1\ConsoleApplication1\classes.obj  ConsoleApplication1
Error   10  error LNK2019: unresolved external symbol "public: __thiscall Game::~Game(void)" (??1Game@@QAE@XZ) referenced in function "int __cdecl SDL_main(void)" (?SDL_main@@YAHXZ)   C:\Users\FUJITSU\Desktop\frontline defence\project\ConsoleApplication1\ConsoleApplication1\classes.obj  ConsoleApplication1
Error   9   error LNK2019: unresolved external symbol "public: __thiscall Map::~Map(void)" (??1Map@@QAE@XZ) referenced in function "int __cdecl SDL_main(void)" (?SDL_main@@YAHXZ)  C:\Users\FUJITSU\Desktop\frontline defence\project\ConsoleApplication1\ConsoleApplication1\classes.obj  ConsoleApplication1
Error   6   error LNK2019: unresolved external symbol "public: __thiscall Tower::~Tower(void)" (??1Tower@@QAE@XZ) referenced in function "public: __thiscall Game::Game(int,int)" (??0Game@@QAE@HH@Z)   C:\Users\FUJITSU\Desktop\frontline defence\project\ConsoleApplication1\ConsoleApplication1\classes.obj  ConsoleApplication1
Error   5   error LNK2019: unresolved external symbol "public: __thiscall Tower::Tower(void)" (??0Tower@@QAE@XZ) referenced in function "public: __thiscall Game::Game(int,int)" (??0Game@@QAE@HH@Z)    C:\Users\FUJITSU\Desktop\frontline defence\project\ConsoleApplication1\ConsoleApplication1\classes.obj  ConsoleApplication1
Error   11  error LNK2019: unresolved external symbol _SDL_main referenced in function _main    C:\Users\FUJITSU\Desktop\frontline defence\project\ConsoleApplication1\ConsoleApplication1\SDL2main.lib(SDL_windows_main.obj)   ConsoleApplication1

Answer 1

您收到引用构造函数和析构函数的链接器错误，因为您没有为这些函数提供任何实现(正如 Michael Burr 在评论中指出的那样)。

函数_main中引用的未解析的外部符号_SDL_main是因为main函数需要有一个特定的签名:int main(int argc, char* argv []) 并检查链接器的输入中是否还有 SDL2main.lib。

最后，您似乎永远不会创建任何renderer(除非您创建的地方未包含在您的代码示例中)，因此您必须添加对SDL_CreateRenderer() 的调用。在 main 中创建 SDL_Window 之后。