使用標題進行編譯時出現多重定義

Question

我的頭文件和編譯有很多問題。我有一切與標題守衛鏈接，但由於某種原因，我仍然收到了很多多重定義錯誤。我也在尋找更好的方式來組織代碼的幫助。無論幫助表示讚賞！

這是我的控制檯的OUT輸出，當我做了G ++調用：

g++ main.cpp close.cpp init.cpp load_media.cpp texture.cpp -w -lSDL2 -lSDL2_image -lSDL2_mixer -lSDL2_ttf -o run 
/tmp/cc3oNgPs.o:(.bss+0x0): multiple definition of `g_font' 
/tmp/ccg0hCKW.o:(.bss+0x0): first defined here 
/tmp/cc3oNgPs.o:(.bss+0x8): multiple definition of `g_window' 
/tmp/ccg0hCKW.o:(.bss+0x8): first defined here 
/tmp/cc3oNgPs.o:(.bss+0x10): multiple definition of `g_renderer' 
/tmp/ccg0hCKW.o:(.bss+0x10): first defined here 
/tmp/cc3oNgPs.o:(.bss+0x20): multiple definition of `g_text_texture' 
/tmp/ccg0hCKW.o:(.bss+0x20): first defined here 
/tmp/ccIgzhbZ.o:(.bss+0x0): multiple definition of `g_font' 
/tmp/ccg0hCKW.o:(.bss+0x0): first defined here 
/tmp/ccIgzhbZ.o:(.bss+0x8): multiple definition of `g_window' 
/tmp/ccg0hCKW.o:(.bss+0x8): first defined here 
/tmp/ccIgzhbZ.o:(.bss+0x10): multiple definition of `g_renderer' 
/tmp/ccg0hCKW.o:(.bss+0x10): first defined here 
/tmp/ccIgzhbZ.o:(.bss+0x20): multiple definition of `g_text_texture' 
/tmp/ccg0hCKW.o:(.bss+0x20): first defined here 
/tmp/ccQs9gPv.o:(.bss+0x0): multiple definition of `g_font' 
/tmp/ccg0hCKW.o:(.bss+0x0): first defined here 
/tmp/ccQs9gPv.o:(.bss+0x8): multiple definition of `g_window' 
/tmp/ccg0hCKW.o:(.bss+0x8): first defined here 
/tmp/ccQs9gPv.o:(.bss+0x10): multiple definition of `g_renderer' 
/tmp/ccg0hCKW.o:(.bss+0x10): first defined here 
/tmp/ccQs9gPv.o:(.bss+0x20): multiple definition of `g_text_texture' 
/tmp/ccg0hCKW.o:(.bss+0x20): first defined here 
/tmp/ccxzUgM2.o:(.bss+0x0): multiple definition of `g_font' 
/tmp/ccg0hCKW.o:(.bss+0x0): first defined here 
/tmp/ccxzUgM2.o:(.bss+0x8): multiple definition of `g_window' 
/tmp/ccg0hCKW.o:(.bss+0x8): first defined here 
/tmp/ccxzUgM2.o:(.bss+0x10): multiple definition of `g_renderer' 
/tmp/ccg0hCKW.o:(.bss+0x10): first defined here 
/tmp/ccxzUgM2.o:(.bss+0x20): multiple definition of `g_text_texture' 
/tmp/ccg0hCKW.o:(.bss+0x20): first defined here 
collect2: error: ld returned 1 exit status 

這裏是我的2頭文件：

isolation.h

//include //include guard 
#ifndef ISOLATION_H 
#define ISOLATION_H 

//include dependencies 
#include <SDL2/SDL.h> 
#include <SDL2/SDL_image.h> 
#include <SDL2/SDL_ttf.h> 
#include <stdio.h> 
#include <string> 

//include headers 
#include "texture.h" 

//Screen dimension constants 
const int SCREEN_WIDTH = 1280; 
const int SCREEN_HEIGHT = 800; 

//forward delcarlation 
//class Texture; 

//start up SDL create window 
bool init(); 

//load all media 
bool load_media(); 

//free all and shut down SDL 
void close(); 

//load global front 
TTF_Font* g_font = NULL; 

//window 
SDL_Window* g_window = NULL; 

//renderer 
SDL_Renderer* g_renderer = NULL; 

//load jpeg + font 
//Texture background_texture; 

//rendered font texture 
Texture g_text_texture; 

#endif 

texture.h

//include guard 
#ifndef TEXTURE_H 
#define TEXTURE_H 

//include dependencies 
#include <SDL2/SDL.h> 
#include <SDL2/SDL_image.h> 
#include <SDL2/SDL_ttf.h> 
#include <stdio.h> 
#include <string> 

//include headers 
//#include "isolation.h" 

class Texture { 
    public: 
    //initializes variables 
    Texture(); 

    //deallocates memory 
    ~Texture(); 

    //load image from path 
    bool load_from_file(std::string path); 

    //create image from font string 
    bool load_from_rendered_text(std::string textureText, SDL_Color text_color); 

    //deallocates texture 
    void free(); 

    //set color modulation 
    void set_color(Uint8 red, Uint8 green, Uint8 blue); 

    //set blend mode 
    void set_blend_mode(SDL_BlendMode blending); 

    //set alpha 
    void set_alpha(Uint8 alpha); 

    //render texture at point 
    void render(int x, int y, SDL_Rect* clip = NULL, double angle = 0.0, SDL_Point* center = NULL, SDL_RendererFlip flip = SDL_FLIP_NONE) const; 

    //get image dimensions 
    int get_width() const; 
    int get_height() const; 

    private: 
    //texture pointer 
    SDL_Texture* m_texture; 

    //dimensions 
    int m_width; 
    int m_height; 
}; 

#endif 

init.cpp

#include "isolation.h" 
//#include "texture.h" 

bool init() { 
    //initialization flag 
    bool success = true; 

    //initialize SDL 
    if (SDL_Init(SDL_INIT_VIDEO) < 0) { 
    printf("SDL could not initialized. SDL Error: %s\n", SDL_GetError()); 
    success = false; 
    } 
    else { 
    //set texture filtering linear 
    if (!SDL_SetHint(SDL_HINT_RENDER_SCALE_QUALITY, "1")) { 
     printf("Warning: Linear filtering not enabled\n"); 
    } 

    //create window 
    g_window = SDL_CreateWindow("Isolation", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, SCREEN_WIDTH, SCREEN_HEIGHT, SDL_WINDOW_SHOWN); 
    if (g_window == NULL) { 
     printf("Window could not be created. SDL Error: %s\n", SDL_GetError()); 
     success = false; 
    } 
    else { 
     //create vsynced renderer 
     g_renderer = SDL_CreateRenderer(g_window, -1, SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC); 
     if (g_renderer == NULL) { 
     printf("Renderer could not be created. SDL Error: %s\n", SDL_GetError()); 
     success = false; 
     } 
     else { 
     //initialize renderer color 
     SDL_SetRenderDrawColor (g_renderer, 0xFF, 0xFF, 0xFF, 0xFF); 

     //initialize JPEG loading 
     int img_flags = IMG_INIT_JPG; 
     if (!(IMG_Init(img_flags) & img_flags)) { 
      printf("SDL_image could not be initialize. SDL_image Error: %s\n", IMG_GetError()); 
      success = false; 
     } 

     //initialize SDL_ttf 
     if (TTF_Init() == -1) { 
      printf("SDL_ttf could not be initialize. SDL_ttf Error: %s\n", TTF_GetError()); 
     } 
     } 
    } 
    } 

    return success; 
} 

load_media.cpp

#include "isolation.h" 
//s#include "texture.h" 

bool load_media() { 
    bool success = true; 

    //load background img 
    //if(!background_texture.load_from_file("img/vancouver.jpg")) { 
    // printf("Failed to load background texture!\n"); 
    // success = false; 
    //} 

    //open font 
    g_font = TTF_OpenFont("lazy.ttf", 28); 
    if (g_font == NULL) { 
    printf("Failed to load lazy font. SDL_ttf Error: %s\n", TTF_GetError()); 
    success = false; 
    } 
    else { 
    //render texture 
    SDL_Color text_color = { 0, 0, 0 }; 
    if (!g_text_texture.load_from_rendered_text("hello from the other side ", text_color)) { 
     printf("Failed to render text texture\n"); 
     success = false; 
    } 
    } 

    return success; 
} 

close.cpp

#include "isolation.h" 
//#include "texture.h" 

void close() { 
    //free loaded text 
    g_text_texture.free(); 

    //free font 
    TTF_CloseFont(g_font); 
    g_font = NULL; 

    //destroy window 
    SDL_DestroyWindow(g_window); 
    SDL_DestroyRenderer(g_renderer); 
    g_window = NULL; 
    g_renderer = NULL; 

    //quit SDL subsystems 
    TTF_Quit(); 
    IMG_Quit(); 
    SDL_Quit(); 
} 

的main.cpp

#include "isolation.h" 
//#include "texture.h" 

int main(int argc, char* args[]) { 
    //start up SDL 
    if (!init()) { 
    printf("Failed to initialize.\n"); 
    } 
    else { 
    //load media 
    if (!load_media()) { 
     printf("Failed to load media.\n"); 
    } 
    else{ 
     //main loop flag 
     bool quit = false; 

     //event handler 
     SDL_Event e; 

     //while running 
     while (!quit) { 
     //handle events on queue 
     while (SDL_PollEvent(&e) != 0) { 
      //user quit 
      if (e.type == SDL_QUIT) { 
      quit = true; 
      } 
     } 

     //clear screen 
     SDL_SetRenderDrawColor(g_renderer, 0xFF, 0xFF, 0xFF, 0xFF); 
     SDL_RenderClear(g_renderer); 

     //render frame 
     g_text_texture.render((SCREEN_WIDTH - g_text_texture.get_width())/2, (SCREEN_HEIGHT - g_text_texture.get_height())/2); 

     //update screen 
     SDL_RenderPresent(g_renderer); 
     } 
    } 
    } 

    //free memory and close SDL 
    close(); 

    return 0; 
} 

Answer 1

請勿混用定義/實例在聲明一個.h文件。您正在實例化g_font,g_window和g_renderer的isolation.h文件。正確的實例是隻有一次，通常在一個.cpp

解決您的問題，改變isolation.h宣佈這些變量外部鏈接：

//load global front 
extern TTF_Font* g_font; 

//window 
extern SDL_Window* g_window; 

//renderer 
extern SDL_Renderer* g_renderer; 

，並在apppropriated .cpp文件實例他們只有一次，例如，init.cpp