x11/kde4-workspace build with clang

[ 96%] Building CXX object kwin/CMakeFiles/kdeinit_kwin.dir/glxbackend.cpp.o
/usr/ports/x11/kde4-workspace/work/kde-workspace-4.11.2/kwin/scene_opengl.cpp:309:10: error: use of undeclared identifier
      'GL_GUILTY_CONTEXT_RESET_ARB'
    case GL_GUILTY_CONTEXT_RESET_KWIN:
         ^
/usr/ports/x11/kde4-workspace/work/kde-workspace-4.11.2/kwin/scene_opengl.cpp:297:43: note: expanded from macro 'GL_GUILTY_CONTEXT_RESET_KWIN'
#  define GL_GUILTY_CONTEXT_RESET_KWIN    GL_GUILTY_CONTEXT_RESET_ARB
                                          ^
/usr/ports/x11/kde4-workspace/work/kde-workspace-4.11.2/kwin/scene_opengl.cpp:313:10: error: use of undeclared identifier
      'GL_INNOCENT_CONTEXT_RESET_ARB'
    case GL_INNOCENT_CONTEXT_RESET_KWIN:
         ^
/usr/ports/x11/kde4-workspace/work/kde-workspace-4.11.2/kwin/scene_opengl.cpp:298:43: note: expanded from macro
      'GL_INNOCENT_CONTEXT_RESET_KWIN'
#  define GL_INNOCENT_CONTEXT_RESET_KWIN  GL_INNOCENT_CONTEXT_RESET_ARB
                                          ^
/usr/ports/x11/kde4-workspace/work/kde-workspace-4.11.2/kwin/scene_opengl.cpp:317:10: error: use of undeclared identifier
      'GL_UNKNOWN_CONTEXT_RESET_ARB'
    case GL_UNKNOWN_CONTEXT_RESET_KWIN:
         ^
/usr/ports/x11/kde4-workspace/work/kde-workspace-4.11.2/kwin/scene_opengl.cpp:299:43: note: expanded from macro
      'GL_UNKNOWN_CONTEXT_RESET_KWIN'
#  define GL_UNKNOWN_CONTEXT_RESET_KWIN   GL_UNKNOWN_CONTEXT_RESET_ARB
                                          ^
/usr/ports/x11/kde4-workspace/work/kde-workspace-4.11.2/kwin/scene_opengl.cpp:1098:37: warning: offset of on non-POD type 'KWin::GLVertex2D'
      [-Winvalid-offsetof]
        { VA_Position, 2, GL_FLOAT, offsetof(GLVertex2D, position) },
                                    ^                    ~~~~~~~~
/usr/include/stddef.h:62:32: note: expanded from macro 'offsetof'
#define offsetof(type, member)  __offsetof(type, member)
                                ^
/usr/include/sys/cdefs.h:449:34: note: expanded from macro '__offsetof'
#define __offsetof(type, field)  __builtin_offsetof(type, field)
                                 ^
/usr/ports/x11/kde4-workspace/work/kde-workspace-4.11.2/kwin/scene_opengl.cpp:1099:37: warning: offset of on non-POD type 'KWin::GLVertex2D'
      [-Winvalid-offsetof]
        { VA_TexCoord, 2, GL_FLOAT, offsetof(GLVertex2D, texcoord) },
                                    ^                    ~~~~~~~~
/usr/include/stddef.h:62:32: note: expanded from macro 'offsetof'
#define offsetof(type, member)  __offsetof(type, member)
                                ^
/usr/include/sys/cdefs.h:449:34: note: expanded from macro '__offsetof'
#define __offsetof(type, field)  __builtin_offsetof(type, field)
                                 ^
/usr/ports/x11/kde4-workspace/work/kde-workspace-4.11.2/kwin/scene_opengl.cpp:2485:17: warning: unused variable 'bottomRight'
      [-Wunused-variable]
    const QSize bottomRight(shadowPixmap(ShadowElementBottomRight).size());
                ^
In file included from /usr/ports/x11/kde4-workspace/work/kde-workspace-4.11.2/kwin/scene_opengl.cpp:24:
/usr/ports/x11/kde4-workspace/work/kde-workspace-4.11.2/kwin/scene_opengl.h:350:18: warning: private field 'm_scene' is not used
      [-Wunused-private-field]
    SceneOpenGL *m_scene;
                 ^
4 warnings and 3 errors generated.
gmake[4]: *** [kwin/CMakeFiles/kdeinit_kwin.dir/scene_opengl.cpp.o] Error 1
gmake[4]: *** Waiting for unfinished jobs....
/usr/ports/x11/kde4-workspace/work/kde-workspace-4.11.2/kwin/glxbackend.cpp:48:11: warning: expression which evaluates to zero treated as a
      null pointer constant of type 'GLXContext' (aka '__GLXcontextRec *') [-Wnon-literal-null-conversion]
    , ctx(None)
          ^~~~
/usr/ports/x11/kde4-workspace/work/kde-workspace-4.11.2/kwin/glxbackend.cpp:160:58: error: use of undeclared identifier
      'GLX_CONTEXT_ROBUST_ACCESS_BIT_ARB'
            GLX_CONTEXT_FLAGS_ARB,                       GLX_CONTEXT_ROBUST_ACCESS_BIT_ARB,
                                                         ^
/usr/ports/x11/kde4-workspace/work/kde-workspace-4.11.2/kwin/glxbackend.cpp:161:13: error: use of undeclared identifier
      'GLX_CONTEXT_RESET_NOTIFICATION_STRATEGY_ARB'
            GLX_CONTEXT_RESET_NOTIFICATION_STRATEGY_ARB, GLX_LOSE_CONTEXT_ON_RESET_ARB,
            ^
/usr/ports/x11/kde4-workspace/work/kde-workspace-4.11.2/kwin/glxbackend.cpp:161:58: error: use of undeclared identifier
      'GLX_LOSE_CONTEXT_ON_RESET_ARB'
            GLX_CONTEXT_RESET_NOTIFICATION_STRATEGY_ARB, GLX_LOSE_CONTEXT_ON_RESET_ARB,
                                                         ^
/usr/ports/x11/kde4-workspace/work/kde-workspace-4.11.2/kwin/glxbackend.cpp:172:58: error: use of undeclared identifier
      'GLX_CONTEXT_ROBUST_ACCESS_BIT_ARB'
            GLX_CONTEXT_FLAGS_ARB,                       GLX_CONTEXT_ROBUST_ACCESS_BIT_ARB,
                                                         ^
/usr/ports/x11/kde4-workspace/work/kde-workspace-4.11.2/kwin/glxbackend.cpp:173:13: error: use of undeclared identifier
      'GLX_CONTEXT_RESET_NOTIFICATION_STRATEGY_ARB'
            GLX_CONTEXT_RESET_NOTIFICATION_STRATEGY_ARB, GLX_LOSE_CONTEXT_ON_RESET_ARB,
            ^
/usr/ports/x11/kde4-workspace/work/kde-workspace-4.11.2/kwin/glxbackend.cpp:173:58: error: use of undeclared identifier
      'GLX_LOSE_CONTEXT_ON_RESET_ARB'
            GLX_CONTEXT_RESET_NOTIFICATION_STRATEGY_ARB, GLX_LOSE_CONTEXT_ON_RESET_ARB,
                                                         ^
1 warning and 6 errors generated.
gmake[4]: *** [kwin/CMakeFiles/kdeinit_kwin.dir/glxbackend.cpp.o] Error 1
gmake[4]: Leaving directory `/usr/ports/x11/kde4-workspace/work/.build'
gmake[3]: *** [kwin/CMakeFiles/kdeinit_kwin.dir/all] Error 2
gmake[3]: Leaving directory `/usr/ports/x11/kde4-workspace/work/.build'
gmake[2]: *** [all] Error 2
gmake[2]: Leaving directory `/usr/ports/x11/kde4-workspace/work/.build'
===> Compilation failed unexpectedly.
Try to set MAKE_JOBS_UNSAFE=yes and rebuild before reporting the failure to
the maintainer.
*** Error code 1