Inclusion Guards are just the beginning...not the end. There are lots of other problems. Here is another rule of thumb.

Don''t put #include statements in your header unless absolutely necessary. Put them in your .cpp files when possible. Predeclare a class instead of #including it in a header if you can.

To really solve the problem you have to understand the problem. The preprocessor replaces every #include with the contents of the file that you list. Consider FileA.h that includes FileB.h and visa-versa. Understanding this problem is the beginning of understanding the extent of the problem.

The following is a slightly complex solution that comes from lots of experience:
For each group of related files create two additional header files for the group. I will use the example of all Graphics files. Name them InternalGraphics.h and ExternalGraphics.h. Inside your group ONLY include your pch file and InternalGraphics.h (stdafx.h is a pch, if you don''t understand, don''t use one). Outside your group don''t include the class header files, ONLY include ExternalGraphics.h. Organize these two files so that they predeclare classes and then include the files in the correct order.

This solution is obviously overkill for small projects. But it''s a lifesaver for large ones.


// Example InternalGraphics.h
// This file contains ALL files necessary for ANY
// .cpp file in the Graphics Module

#include <list>
#include <map>
#include <math.h>
#include <float.h>
#include <DirectX.h>

// Header for another module
// Graphics Module needs to use parts of this module
#include "ExternalResourceLoader.h"

class VertexData;
class PixelShader;
class GraphicsEngine;

#include "PixelShader.h"
#include "VertexData.h"
#include "GraphicsInterface.h"
#include "GraphicsEngine.h"

// End InternalGraphics.h



// Example ExternalGraphics.h
// This file ONLY contains includes necessary for other
// modules to use the graphics engine

#include <list>

#include "GraphicsInterface.h"

// End ExternalGraphics.h





-----------
VenDrake

"My stupid jar is full. I can''t talk to you anymore."

What compiler/linker or IDE is that error message from? Dev-cpp? Just curious...

Well, I can't really tell why it says it's defined more then once. If you only defined it once in your .c file. Perhaps it was defined again in one of the modules that gets linked in.

One suggestion, when you make a global variable, you run the risk of it being declared in other places. And with the generic nature of the variable names (hInstance, hWnd, etc...) there is a big risk that someone else may have used those same names somewhere else.

I would say use namespaces, but it's apparent your using c. SO, you should try changing thier names to something more specific to your app. For example, change hInstance to g_MyGLWinInstance...

Also, you have included both gl.h and glu.h, now I'm not positive whats in both those headers... But do you really need both in the header? I see your using some GL datatypes in the header, but are they defined in both the headers? Or can you remove at least one header to the source file? Just a question.

Edited - Spelling

[edited by - pjcast on January 13, 2004 2:32:54 PM]