Statement includes itself

Question

I have 2 files that use each other in them, so I try to include each of them in each file, which doesn't work because the files would include themselves. I tried putting the relevant include statements inside the header guards, but that makes the compiler think that all the variable names are type identifiers.

Here's what I have when its inside the header guards

//MenuItem.h
#include <SDL.h>
#include <string>

#ifndef MENU_ITEM_H  //avoid multiple inclusion
#define MENU_ITEM_H

#include "window.h"
class MenuItem {
    bool selected = false;
    window containerWindow;
    etc

Window.h includes MenuItem.h within it's header guards.

In MenuItem.h I get errors such as

Error   1   error C2146: syntax error : missing ';' before identifier 'containerWindow' 
Error   2   error C4430: missing type specifier - int assumed. Note: C++ does not support default-int

When I have them outside the head guards (like so)

//MenuItem.h
#include <SDL.h>
#include <string>
#include "window.h"

#ifndef MENU_ITEM_H  //avoid multiple inclusion
#define MENU_ITEM_H

class MenuItem {
    bool selected = false;
    window containerWindow;
    etc

I get the following

Error   1   error C1014: too many include files : depth = 1024

I'm unsure how I can fix it.

What you really need to do is fix your code so that the headers don't depend on each other. — juanchopanza, Dec 28 '14 at 15:25
@juanchopanza I don't understand why putting the include within the header guard doesn't solve the problem, or why those errors come up — Matt, Dec 28 '14 at 15:32
I have another possible solution, unfortunatelly question was closed so I can't provide an answer. — mip, Dec 28 '14 at 15:41
@juanchopanza This question is not duplicate. My answer doesn't fit to one you marked as this ones duplicate. — mip, Dec 28 '14 at 15:45
@juanchopanza former one asks about circular inclusions, while this one asks about circular dependency of structures. It is subtle difference, but my answer does not make sense in the former one. — mip, Dec 28 '14 at 15:59

score 1 · Accepted Answer · answered Dec 28 '14 at 15:33

1

Avoid circular inclusion by using forward declaration: use a window pointer in your class MenuItem instead of an object.

Replace:

#include "window.h"
class MenuItem {
    bool selected = false;
    window containerWindow;
    etc

By:

class window; // or struct window if window is a struct
class MenuItem {
    bool selected = false;
    window* containerWindow;
    etc

Also, as commented, make sure you #ifdef has a #endif, but I don't think that was causing the problem you reported.

answered Dec 28 '14 at 15:33

jpo38

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Thanks a lot! That got it to work! I had tried using a forward declaration but that didn't work, I wasn't using a pointer though. I assume it works because you don't need to know what the default constructor is when initializing a pointer, correct? – Matt Dec 28 '14 at 15:36
It works with pointers because compiler does not need to know the actual size of the object (compiler knows the size of a pointer, it depends on your targetted platform, but does not know the size of a Window object...unless header file is included). – jpo38 Dec 28 '14 at 15:47
PLease also vote up if it fixed your problem. Thanks. – jpo38 Dec 28 '14 at 15:48
Don't have enough reputation to upvote, have enough reputation to do so. Would if I could – Matt Dec 28 '14 at 16:24

Statement includes itself

1 Answers1