C ++重复符号

Question

（苹果电脑）

我尝试了名称空间，包括警卫，编译指示一次等。

基本上，这是结构：

的CMakeLists.txt

add_executable(Game Game/main.cpp Game/rtexture.cpp)

游戏/ main.cpp中

#include "cleanup.h"

//...
cleanup(foobar);

游戏/ rtexture.cpp

#include "cleanup.h"

//...
cleanup(foobar);

cleanup.h

//various includes

template<typename T, typename... Args>
void cleanup(T *t, Args&&... args){
    //Cleanup the first item in the list
    cleanup(t);
    //Recurse to clean up the remaining arguments
    cleanup(std::forward<Args>(args)...);
}
/*
 * These specializations serve to free the passed argument and also provide the
 * base cases for the recursive call above, eg. when args is only a single item
 * one of the specializations below will be called by
 * Cleanup(std::forward<Args>(args)...), ending the recursion
 * We also make it safe to pass nullptrs to handle situations where we
 * don't want to bother finding out which values failed to load (and thus are null)
 * but rather just want to clean everything up and let cleanup sort it out
 */
template<>
void cleanup<SDL_Window>(SDL_Window *win){
    if (!win){
        return;
    }
    SDL_DestroyWindow(win);
}
template<>
void cleanup<SDL_Renderer>(SDL_Renderer *ren){
    if (!ren){ 
        return;
    }
    SDL_DestroyRenderer(ren);
}
template<>
void cleanup<SDL_Texture>(SDL_Texture *tex){
    if (!tex){
        return;
    }
    SDL_DestroyTexture(tex);
}
template<>
void cleanup<SDL_Surface>(SDL_Surface *surf){
    if (!surf){
        return;
    }
    SDL_FreeSurface(surf);
}

如果有人问，我确实从教程中获取了这个“cleanup.h”，但是没有找到将它包含在多个类中的方法，而没有声明重复的符号。

Home at cruz45488-y19-MBA13-12 in ~/desktop/sdlworkspace/tmp
$ make
Linking CXX executable Game
duplicate symbol __ZN5RUtil7cleanupI10SDL_WindowJEEEvPT_DpOT0_ in:
    CMakeFiles/Game.dir/Game/main.cpp.o
    CMakeFiles/Game.dir/Game/rtexture.cpp.o
duplicate symbol __ZN5RUtil7cleanupI12SDL_RendererJEEEvPT_DpOT0_ in:
    CMakeFiles/Game.dir/Game/main.cpp.o
    CMakeFiles/Game.dir/Game/rtexture.cpp.o
duplicate symbol __ZN5RUtil7cleanupI11SDL_TextureJEEEvPT_DpOT0_ in:
    CMakeFiles/Game.dir/Game/main.cpp.o
    CMakeFiles/Game.dir/Game/rtexture.cpp.o
duplicate symbol __ZN5RUtil7cleanupI11SDL_SurfaceJEEEvPT_DpOT0_ in:
    CMakeFiles/Game.dir/Game/main.cpp.o
    CMakeFiles/Game.dir/Game/rtexture.cpp.o

有帮助吗？ 谢谢。

Answer 1

显式函数模板特化取决于一个定义规则，就像常规函数一样。 添加inline以允许标题中的定义; 或者在源文件中定义它们，并在标题中添加声明。

Answer 2

我没有看到任何包括警卫。 此外，因为您将此标头包含在多个.cpp文件中，所以#ifdef并不存在 - 您需要使用inline关键字（告知链接器），可以在多个转换单元中定义特定函数。

#ifndef CLEANUP_H
#define CLEANUP_H

//includes...

template<>
inline void cleanup<SDL_Window>(SDL_Window *win){
    if (!win){
        return;
    }
    SDL_DestroyWindow(win);
}
template<>
inline void cleanup<SDL_Renderer>(SDL_Renderer *ren){
    if (!ren){ 
        return;
    }
    SDL_DestroyRenderer(ren);
}
template<>
inline void cleanup<SDL_Texture>(SDL_Texture *tex){
    if (!tex){
        return;
    }
    SDL_DestroyTexture(tex);
}
template<>
inline void cleanup<SDL_Surface>(SDL_Surface *surf){
    if (!surf){
        return;
    }
    SDL_FreeSurface(surf);
}

#endif /* CLEANUP_H */