C++ Namespace and Syntax Header File Errors

Question

I am having the usual errors within header files, as listed below.

Error   54  error C3083: 'Resources': the symbol to the left of a '::' must be a type   e:\users\nkosi\documents\visual studio 2010\projects\directx games\direct2d\dx2dhelper\dx2dhelper\sprite.h  28  1   DX2DHelper
Error   55  error C2039: 'DX2DImage' : is not a member of 'DX2DHelper'  e:\users\nkosi\documents\visual studio 2010\projects\directx games\direct2d\dx2dhelper\dx2dhelper\sprite.h  28  1   DX2DHelper
Error   56  error C2061: syntax error : identifier 'DX2DImage'  e:\users\nkosi\documents\visual studio 2010\projects\directx games\direct2d\dx2dhelper\dx2dhelper\sprite.h  28  1   DX2DHelper
Error   57  error C3083: 'Resources': the symbol to the left of a '::' must be a type   e:\users\nkosi\documents\visual studio 2010\projects\directx games\direct2d\dx2dhelper\dx2dhelper\sprite.h  32  1   DX2DHelper
Error   58  error C2039: 'DX2DImage' : is not a member of 'DX2DHelper'  e:\users\nkosi\documents\visual studio 2010\projects\directx games\direct2d\dx2dhelper\dx2dhelper\sprite.h  32  1   DX2DHelper
Error   59  error C2143: syntax error : missing ';' before '*'  e:\users\nkosi\documents\visual studio 2010\projects\directx games\direct2d\dx2dhelper\dx2dhelper\sprite.h  32  1   DX2DHelper
Error   60  error C4430: missing type specifier - int assumed. Note: C++ does not support default-int   e:\users\nkosi\documents\visual studio 2010\projects\directx games\direct2d\dx2dhelper\dx2dhelper\sprite.h  32  1   DX2DHelper
Error   61  error C2061: syntax error : identifier 'GameBase'   e:\users\nkosi\documents\visual studio 2010\projects\directx games\direct2d\dx2dhelper\dx2dhelper\systemclass.h 30  1   DX2DHelper

However, for the life of me, I can't figure out what I am doing wrong. I know I'm probably missing a semi-colon or something, but I really can't figure it out. All the header files are below.

DX2DHelper.h

#include "targetver.h"

#define WIN32_LEAN_AND_MEANheaders
// Windows Header Files:
#include <windows.h>

#include <iostream>

#include <D2D1.h>
#include <D2D1Helper.h>
#include <wincodec.h>
#include <D2DBaseTypes.h>
#include <D2Derr.h>

#define DLEX __declspec(dllexport)

#include "GameBase.h"
#include "SystemClass.h"
#include "DX2DImage.h"
#include "Sprite.h"

SystemClass.h

#ifndef SYSTEMCLASS_H
#define SYSTEMCLASS_H

#include "DX2DHelper.h"

namespace DX2DHelper
{
    namespace Core
    {
        class SystemClass;
        struct WindowOptions;

        struct DLEX WindowOptions {};

        class DLEX SystemClass
        {
        public:
            bool Initialize(WindowOptions options, HINSTANCE hInst);
            void Run(GameBase* game, DX2DInitOptions options);
        private:
            WindowOptions options;    
        };
    }
}
#endif

DX2DImage.h

#ifndef DX2DIMAGE_H
#define DX2DIMAGE_H

#include "DX2DHelper.h"

namespace DX2DHelper
{
    namespace Resources
    {
        class DX2DImage;
        class DX2DImageLoader;

        class DLEX DX2DImageLoader
        {
        public:
            HRESULT LoadFromFile(char* filePath, DX2DImage* image);
        };

        class DLEX DX2DImage
        {
        public:
            friend class DX2DImageLoader;
        };
    }
}

#endif

Sprite.h

#ifndef SPRITE_H
#define SPRITE_H

#include "DX2DHelper.h"

namespace DX2DHelper
{
    namespace GameComponents
    {
        class DLEX Sprite
        {
        public:
            void SetImage(DX2DHelper::Resources::DX2DImage* image);

        private:
            DX2DHelper::Resources::DX2DImage* image;
        };
    }
}
#endif

GameBase.h

#ifndef GAMEBASE_H
#define GAMEBASE_H

#include "DX2DHelper.h"

namespace DX2DHelper
{
    namespace Core
    {
        class DLEX GameBase
        {
        public:
            friend class SystemClass;

            HRESULT Initialize(HINSTANCE hInst, HWND winHandle, struct DX2DInitOptions options);
        };

        struct DLEX DX2DInitOptions {};
    }
}
#endif

If anyone could figure out the mistakes, I would be very grateful. I've been looking at the same files for probably close to an hour, hour and a half now, and I just can't fix it.

Answer 1

Your headers have (many) include cycle(s). For example, DX2DHelper.h includes Sprite.h includes DX2DHelper.h. This is probably what's causing your errors. This code isn't Java, and those aren't import statements: #include cycles totally kill compiles, even if you don't get a compile error specifically stating so. Pick an acyclic order for your header files.

I'd suggest that DX2DHelper.h not have any of the includes at the bottom. Sprite.h could include DX2DImage.h.

Where your objects have cyclic dependencies (as is the case with SystemClass and GameBase, for example), you'll need another solution. Forward declare the dependent class without giving its full declaration, e.g. in SystemClass.h you might add somewhere early:

namespace DX2DHelper { namespace Core { class DLEX GameBase; } }

and similarly in in GameBase.h:

namespace DX2DHelper { namespace Core { class DLEX SystemClass;} }

This can even be a good idea when there aren't cyclic object dependencies involved -- its usually an easy way around the type of header hell you've run into here. Of course, to get everything to compile, you'll probably need to #include the appropriate headers in the corresponding implementation files. But, assuming you don't #include any of your .cpp/.cc files, this should allow everything to compile without the #include hell you've gotten yourself into.