多个程序文件造成重复include的问题

macarthor

共有list.h、queue.h、queue.cpp、stack.h、stack.cpp、main.cpp这些文件

3个cpp共同生成可执行文件

queue.h与stack.h都#include "list.h"

main.cpp里#include "queue.h"与#include "stack.h"

编译的时候报告错误：

In file included from queue.h:1,
               from main.cpp:4:
list.h:2: error: redefinition of `struct list'
list.h:2: error: previous definition of `struct list'
make: *** [doit] 错误 1

怎么解决呢？

herberteuler

1. #ifndef SOMETHING
   
2. #define SOMETHING
   
3. 
   
4. /* contents of your header file */
   
5. 
   
6. #endif

复制代码

macarthor

具体怎么加啊？

herberteuler

Replace 'SOMETHING' with an unique ID and '/* contents of your header file */' with whatever you want to write in your header file.

macarthor

还是不太懂

在哪个文件加呢？

加在什么位置呢？

thx

herberteuler

Here is an example:

1. #ifndef EXAMPLE_H__
   
2. #define EXAMPLE_H__
   
3. 
   
4. struct example {
   
5.     int value;
   
6.     struct example *next;
   
7. };
   
8. 
   
9. #endif  /* EXAMPLE_H__ */

复制代码

As you see, the first time including this file will define a preprocessor macro EXAMPLE_H__, which will prevent the structure definition being included for the second time.

macarthor

thx

ok le

any principles here?

herberteuler

You should choose the preprocessor macro (EXAMPLE_H__ in the above example) carefully to avoid name duplicating. What's more, you'd better add comment like '/* EXAMPLE_H__ */ after the last #endif since it will be a bit harder to find the matched #ifndef if the header file is very long.

macarthor

关于这个，C/C++有没有专有的名词？

就象继承、派生等

thx

herberteuler

No. It is just a skill.