Using Glew in multiple files

Somehow I can't get Glew in multiple header files. It i开发者_运维知识库s just complaining about Gl is already defined before GLEW.

I have the following file structure in short:

1. Program.h

   includes: <GL/glew.h>, <GL/freeglut.h> and "SceneManager.h".

2. SceneManager.h

   includes: "GameObject.h"

3. GameObject.h

   includes: <GL/glew.h>, <GL/freeglut.h>.

I do understand that freeglut is in front of glew, but I would like to have the GL_BGR extension for example.

How do I get the glew.h in the GameObject as well?

Must be a bug in glew.h.

I use GLee instead, which doesn't have this problem. GLee's test looks like this:

#ifndef __glee_h_
#define __glee_h_

#ifdef __gl_h_
    #error gl.h included before glee.h
#endif

#ifdef __glext_h_
    #error glext.h included before glee.h
#endif

#ifdef __wglext_h_
    #error wglext.h included before glee.h
#endif

#ifdef __glxext_h_
    #error glxext.h included before glee.h
#endif

//...
#endif /* !defined(__glee_h_) */

So the tests are only done the first time glee.h is included.

Apparently glew improperly does the tests outside the header multiple inclusion guard.

I switched from glew to GLee the first time I ran an OpenGL trace (glslDevil, actually) and saw glew calling glGetString(GL_EXTENSIONS) hundreds of times at startup.

I did it a bit different myself right now:

I created a precompiled header with glew and freeglut in it. It looks like this:

#ifndef _STDAFX_H_
#define _STDAFX_H_

#include <GL/glew.h>
#include <GL/freeglut.h>

#endif

Could someone confirm if this is a solid and well know method to do so?