Gentoo's Bugzilla –
Attachment 390490 Details for
Bug 530978x11-drivers/xf86-video-vmware-13.0.2 - In file included from .../work/xf86-video-vmware-13.0.2/vmwgfx/vmwgfx_overlay.c:38 : /usr/include/xorg/os.h:579:1: error: expected identifier or '(' before '__extension__'