glbinding, Qt and error "glbinding is not compatible with gl.h"

Question

I'm writing a new project and want to replace GLEW with glbinding.

My setup is like this: VS 2015, Qt 5.6, glbinding 2.0

I tried to compile quite simple code - only window (QWindow) with OpenGL context (QOpenGLContext) but got an error: glbinding is not compatible with gl.h

When I was tracking this bug I found out that file (which is imported by the glbinding/gl/gl.h) nogl.h is causing this message with the code below:

#ifdef __gl_h_
    #error "glbinding is not compatible with gl.h"
#else
    #define __gl_h_
#endif

Then I noticed that this is caused by the QtGui/qopenglcontext.h header (which I need for creating OpenGL context...). So when I don't include qopenglcontext.h my program compiles without error. I also noticed that this error message appears only when I include glbinding/gl/gl.h after QtGui/qopenglcontext.h. If I reverse the include order I get a bunch of errors like this:

1>C:\Qt\Qt5.6.0\5.6\msvc2015_64\include\QtGui/qopenglext.h(117): error C2065: 'GLenum': undeclared identifier
1>C:\Qt\Qt5.6.0\5.6\msvc2015_64\include\QtGui/qopenglext.h(117): error C2146: syntax error: missing ')' before identifier 'mode'
1>C:\Qt\Qt5.6.0\5.6\msvc2015_64\include\QtGui/qopenglext.h(118): error C2065: 'GLenum': undeclared identifier
1>C:\Qt\Qt5.6.0\5.6\msvc2015_64\include\QtGui/qopenglext.h(118): error C2146: syntax error: missing ')' before identifier 'target'

After all I still don't know how to solve this and what exactly is causing this error...

Answer 1

glbinding – like practically every other OpenGL loader – has to fiddle with the OpenGL symbol tokens to avoid namespace clashing. To this end it must interact with the OpenGL definitions in a specific way, which means you must not have included any OpenGL header, or something that includes such in turn at the moment you include the glbinding header. The preprocessor fiddling glbinding performs will prevent gl.h getting included in a way that causes trouble.

So what you must do is: Include the glbinding headers in your C++ compilation unit files before everything else (Qt headers, OpenGL helper libraries and so on).