Which version of glext.h (look for "GL_GLEXT_VERSION")?

In version 20140810 it's defined on line 469:

typedef ptrdiff_t GLintptr;

/usr/include/GL/glext.h:#define GL_GLEXT_VERSION 20140810

But we're including "GL/glx.h" which includes "GL/glxext.h", not "GL/glext.h".  Too many x's floating around here.

# grep '^typedef .* GLintptr;' /usr/include/GL/*.h
/usr/include/GL/glcorearb.h:typedef ptrdiff_t GLintptr;
/usr/include/GL/glext.h:typedef ptrdiff_t GLintptr;

I'll keep digging.

#include "GL/glx.h" should pull in GL/gl.h (line 32) which should include GL/glext.h  So by time we hit the use of GLintptr, it should have been defined.

When I compile a trivial test program like this:

#include <GL/glx.h>
int main(void)
{
   GLintptr p;
   return 0;
}

it seems to work.

It seems that in GL/glx.h, GL/glext.h is only included when
GL_GLEXT_LEGACY is not defined (line 2049).
Unfortunatly, GL_GLEXT_LEGACY is defined in Rendering/OpenGL/vtkOpenGL.h 
(line 22) and 
vtkOpenGL.h is included in vtkXOpenGLRenderWindow.cxx that makes GL/glext.h 
not included and GLintptr not declared.

This seems a little strange to me.

So, make the test:

$ cat gltest.c
#define GL_GLEXT_LEGACY
#include <GL/glx.h>
int main(void)
{
   GLintptr p;
   return 0;
}

$ gcc gltest.c
In file included from /usr/include/GL/glx.h:333:0,
                 from gltest.c:2:
/usr/include/GL/glxext.h:480:143: error: unknown type name ‘GLintptr’
 typedef void ( *PFNGLXCOPYBUFFERSUBDATANVPROC) (Display *dpy, GLXContext readCtx, GLXContext writeCtx, GLenum readTarget, GLenum writeTarget, GLintptr readOffset, GLintptr writeOffset, GLsizeiptr size);
                                                                                                                                               ^
....


Now, I suppose it is kind of strange to define GL_GLEXT_LEGACY (not GLXEXT) and then include glx.h, but...

I ran in to this problem trying to build OpenCASCADE for FreeCAD. Not sure if this is helpful or not, but the comment there says:

// exclude modern definitions and system-provided glext.h, should be defined before gl.h inclusion
#define GL_GLEXT_LEGACY

I too ran into this bug when trying to install opencascade for freecad on Arch linux.

I added the following typedefs to a section of code that had been added in 10.3:
# diff glxext.h.saved glxext.h
479a480,481
> typedef ptrdiff_t GLsizeiptr;
> typedef ptrdiff_t GLintptr;

opencascade then compiled, installed with no issues.

With all due respect guys, should one take a closer look and remove the need for GL_GLEXT_LEGACY and its friends GL_GLEXT_PROTOTYPES/GLX_GLXEXT_PROTOTYPES.

Iirc those were added as a workaround for ABI non-compliant users some ~10 years ago.

Dropping the defines and fixing the build issues (not too many, I hope) seems like a better solution than adding another workaround/hack.

Emil is correct.  If your code defines GL_EXT_LEGACY you are also certainly doing it wrong.

What happens if you remove that define from your build?

Seems to be working now.