共享C数组的最优雅的方式

问题描述

我有一个源模块，其中包含一个源模块很多时候，我们称之为 utilities.h 和 utilities.c
其中，我有一个重要的数组，我们称之为

  #define IMPORTANT_ARRAY_LENGTH 10000 
 char important_array [IMPORTANT_ARRAY_LENGTH]; 
  

这个实用程序中有很多其他函数模块，并且它们都工作正常。但是，在其他源文件之一中，我们称之为 worker.c ，我必须使用这个数组。什么是官方，优雅的方式来做到这一点，而不必在 worker中放置 extern char important_array [IMPORTANT_ARRAY_LENGTH] 和宏定义。 c ？

如果我执行以下操作：

utilities.h p>

  #ifndef _UTILITIES_H_ 
 #define _UTILITIES_H_ 
 
 #define IMPORTANT_ARRAY_LENGTH 10000 
 extern char important_array [IMPORTANT_ARRAY_LENGTH]; 
 
 // ... 
  

utilities.c

  #ifndef _UTILITIES_C_ 
 #define _UTILITIES_C_ 
 
 #includeutilities.h
 
 char important_array [IMPORTANT_ARRAY_LENGTH]; 
 
 // ... 
  

worker.c

  #includeutilities.h
 // ... 
 important_array [0] = 0; 
  

那么我的数组将是 worker.c 。如果我在 utilities.h 中不使用 extern 关键字，那么它当然是一个重复的符号。 （奇怪的是，它只编译了一个警告，我可以从链接文件中看到大小被分配了多次。）



我真的必须声明我的数组在 worker.c 中？我想保持一切都干净，并且只将所有声明放在一个地方：在一个头文件中。我希望只有一次宏定义（这是次要的，因为我可以使用const，但我希望预处理器能够处理它，而不是占据位置）。


解决方案

你拥有的是规范的方法：在头文件中有一个 extern 声明，并在 .c 文件。

不，它不会。你的代码会编译并链接就好。

I have to turn back to (embedded) C after some lengthy time with C++, and have the following problem:

I have a source module which is included a lot of times, let's call it utilities.h and utilities.cIn it, I have an important array, let's call it

#define IMPORTANT_ARRAY_LENGTH  10000
char important_array[IMPORTANT_ARRAY_LENGTH];

I have a lot of other functions in this utilities module, and they all work fine. However, in one of the other source files, let's call it worker.c, I have to use this array. What is the "official", elegant way to do this, without having to put extern char important_array[IMPORTANT_ARRAY_LENGTH] and the macro definition in the worker.c ?

If I do the following:

utilities.h

#ifndef _UTILITIES_H_
#define _UTILITIES_H_

#define IMPORTANT_ARRAY_LENGTH  10000
extern char important_array[IMPORTANT_ARRAY_LENGTH];

// ...

utilities.c

#ifndef _UTILITIES_C_
#define _UTILITIES_C_

#include "utilities.h"

char important_array[IMPORTANT_ARRAY_LENGTH];

// ...

worker.c

#include "utilities.h"
// ...
important_array[0] = 0;

then my array will be an undefined symbol in worker.c. If I don't use the extern keyword in utilities.h, then of course, it's a duplicate symbol. (Strangely, it compiles with just a warning, and I can see from the linker file that the size is allocated multiple times.)

Do I really have to declare my array in worker.c? I want to keep everything clean, and have all declarations in one place only: in a header file. And I want to have the macro definition only once (this is secondary, because I could use a const, but I want the preprocessor to handle it, and not take up place)

解决方案

What you have is the canonical way to do it: have an extern declaration in the header file, and define the variable in the .c file.

No, it won't. Your code will compile and link just fine.

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