USE="smx mmxext sse sse2 dts ffmpeg mpeg4 usb win32codecs  xvmc acpi dvd dvdread  x86  apm mad mikmod motif mpeg oggvorbis  X  zlib quicktime"


localhost frog # emerge --update --deep --newuse world
Calculating world dependencies... done!
[nomerge      ] sys-apps/less-394  USE="unicode" 
[nomerge      ]  sys-libs/ncurses-5.6  USE="gpm unicode -bootstrap -build -debug -doc -minimal -nocxx -trace" 
[ebuild  N    ]   sys-libs/gpm-1.20.1-r5  USE="(-selinux)" 
[ebuild  N    ]    sys-libs/ncurses-5.6  USE="gpm unicode -bootstrap -build -debug -doc -minimal -nocxx -trace" 
!!! Error: circular dependencies:

('ebuild', '/', 'sys-libs/ncurses-5.6', 'merge') depends on
   ('ebuild', '/', 'sys-libs/gpm-1.20.1-r5', 'merge') (hard)
('ebuild', '/', 'sys-libs/gpm-1.20.1-r5', 'merge') depends on
   ('ebuild', '/', 'sys-libs/ncurses-5.6', 'merge') (hard)

!!! Note that circular dependencies can often be avoided by temporarily
!!! disabling USE flags that trigger optional dependencies.