title: Do not #include both <GL/glcorearb.h> and either of <GL/gl.h> or <GL/glext.h>
body: <p>In GL/glcorearb.h, the following comment can be found.</p>
  
  <blockquote>
    <p>Do not #include both GL/glcorearb.h and either of GL/gl.h or
    GL/glext.h in the same source file.</p>
  </blockquote>
  
  <p>However, this is the only way I can get my code to work. I have in display.h a declaration of wglCreateContextAttribsARB. This requires GL/wglext.h. However, GL/wglext.h gets undefined errors unless GL/glcorearb.h or GL/gl.h is included.</p>
  
  <p>What is the problem here? Does 'source file' perhaps only refer to the .cpp (which worked fine anyway)?</p>