头文件2中需要头文件1中的struct，我该怎么做？

Question

I have a struct that I use in header file1. I now also need that struct in header file2 because it is used in function prototypes. I have included header file1 in header file2, but this give a lot of complaints of redefition of types after compiling? Is there a straightforward way to do it? I have googled about nested header files but this gives me rather complicated articles. I was wondering if there is a simple way to do this?

Answer 1

Sure there is. Use include guards .

file1.h

#ifndef FILE1_H
#define FILE1_H

/* Define everything here. */

#endif

This way you can include file1.h over and over. In particular, you should always use include guards if a header defines things.

As a side note, if you don't need the details of the struct (that is, it should be an opaque type), you can use an incomplete type and just say struct yourstruct; at the top.

Answer 2

I believe your header files are not guarded with include guards to prevent redefinitions. They should be

//header.h
#ifndef SOME_LONG_UNIQUE_NAME
#define SOME_LONG_UNIQUE_NAME

//header contents here

#endif

As a side note, you don't need all the header and struct definition just to declare function arguments. A forward declaration is enough.

struct C; //not including C.h
struct C* f(struct C* p);

This decreases code coupling and accelerated compilation

Answer 3

Header file 1:

#ifndef HEADERFILE1_H
#define HEADERFILE1_H

//...
#endif

Header file 2:

#ifndef HEADERFILE2_H
#define HEADERFILE2_H

#include "headerfile1.h"

//...
#endif