共享C数组的最优雅的方式 [英] Most elegant way to share a C array

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。

我的数组在worker中是一个未定义的符号。 c

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.c In 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.

my array will be an undefined symbol in worker.c

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

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