多重定义 (LNK2005) 错误
我最近尝试创建一个全局头文件，其中包含错误代码的所有定义(即 NO_ERROR、SDL_SCREEN_FLIP_ERROR 等)，这些只是我将在此处定义的整数.
I recently tried to create a global header file which would have all definitions of error codes (i.e. NO_ERROR, SDL_SCREEN_FLIP_ERROR, etc.) these would just be integers which I would define here.
我在我的两个 .cpp 文件中都包含了这些，但是我收到一个错误，指出我定义了两次.
I included these in both of my .cpp files, however I am getting an error where it is stated that I am defining then twice.
globals.h:
#pragma once
// error related globals
int SCREEN_LOAD_ERROR = 1;
int NO_ERROR = 0;
main.cpp:
#include "globals.h"
#include "cTile.h"
/* rest of the code */
cTile.h:
#pragma once
#include "globals.h"
class cTile {
};
它抱怨 SCREEN_LOAD_ERROR 和 NO_ERROR 被定义了两次，但据我所知，#pragma once 应该可以防止这种情况(我也尝试过 #ifndef，但这也不起作用).
It is complaining that SCREEN_LOAD_ERROR and NO_ERROR are defined twice, but as far as I know #pragma once should prevent this (I also tried #ifndef, but this also did not work).
编译器输出:
1>main.obj : error LNK2005: "int SCREEN_LOAD_ERROR" (?SCREEN_LOAD_ERROR@@3HA) 已经在 cTile.obj 中定义1>main.obj : error LNK2005: "int NO_ERROR" (?NO_ERROR@@3HA) 已经在 cTile.obj 中定义
1>main.obj : error LNK2005: "int SCREEN_LOAD_ERROR" (?SCREEN_LOAD_ERROR@@3HA) already defined in cTile.obj 1>main.obj : error LNK2005: "int NO_ERROR" (?NO_ERROR@@3HA) already defined in cTile.obj
我错过了什么吗?
推荐答案
不要在头文件中声明变量.
当您在头文件中声明变量时，会在包含头文件的每个翻译单元中创建该变量的副本.
Do not declare variables inside your header file.
When you declare a variable in header file a copy of the variable gets created in each translation unit where you include the header file.
解决方案是:
在您的头文件之一中声明它们 extern 并在您的 cpp 文件中定义它们.
Solution is:
Declare them extern inside one of your header file and define them in exactly one of your cpp file.
globals.h:
extern int SCREEN_LOAD_ERROR;
extern int NO_ERROR;
globals.cpp:
#include "globals.h"
int SCREEN_LOAD_ERROR = 0;
int NO_ERROR = 0;
ma??in.cpp:
#include "globals.h"
cTile.h:
#include "globals.h"
相关文章