像这样在 C 中使用 extern 有什么问题吗？
我已经搜索过一些关于这个的东西，但我仍然不明白它..
file1.h
extern int *game_array[5];
Player.c
#include "file1.h"
void *delete_player(player_struct *player)
{
... //some code
game_array[5] = 5; //undefined reference to `game_array`
... //some code
}
当我不使用 extern 时，它“工作正常”=我可以毫无错误地构建它，但程序不是完成的 .. 我想使用 extern 没问题，但出了点问题.. 我想使用我的所有 .c 源文件中的 game_array ...服务器上的游戏数组，我的应用程序中只有该数组的一个实例。
I've already searched something abou this but I've still don't understand it..
file1.h
extern int *game_array[5];
Player.c
#include "file1.h"
void *delete_player(player_struct *player)
{
... //some code
game_array[5] = 5; //undefined reference to `game_array`
... //some code
}
When I don't use extern it "work's fine" = I can build it withou errors, but the program's not finished ..
I suppose the using extern is fine but something is wrong ..
I want to use this game_array ... array of games on server from all my .c source files, there's only one instance of this array in my aplication.
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您需要在
.c文件之一中定义game_array，并将该文件编译/链接到可执行文件中。定义将如下所示：
您的
file1.h所说的基本上是“我的项目中某处存在一个名为game_array的变量，并且它具有这样的内容 -以及这样的类型”。但是，该变量实际上并不存在，除非您在某处（通常是在.c文件中）定义了它。You need to define
game_arrayin one of your.cfiles, and compile/link that file into your executable.The definition will look like this:
What your
file1.his saying is basically "There exists a variable calledgame_arraysomewhere in my project, and it has such-and-such type". However, the variable doesn't actually exist until you've defined it somewhere (typically, in a.cfile).extern关键字基本上意味着编译器不应该抱怨该符号，即使它没有定义，因为它在链接时可用。因此，如果它没有在链接时定义，显然会出现错误。
您需要在您的 C 文件之一中提供一个实现：
类似于：
The
externkeyword basically means that the compiler should not complain about the symbol, even if it's not defined, because it will be available at link-time.So if it's not defined at link-time, you'll obviously have errors.
You need to provide an implementation in one of your C file:
Something like:
编写
extern int *game_array[5];意味着在某个文件中的某个地方，有一个game-array的实际定义 - 即没有的声明extern。您未能提供该信息，因此链接器会抱怨实际变量在任何地方都不存在。Writing
extern int *game_array[5];means that somewhere, in some file, there's an actual definition forgame-array-- i.e., a declaration without theextern.You're failing to provide that, so the linker complains that the actual variable doesn't exist anywhere.