funtoo ~ # emerge -uvDN xorg-server

These are the packages that would be merged, in order:

Calculating dependencies... done!
[ebuild UD ] x11-libs/libdrm-2.4.33 [2.4.40] USE="-libkms
-static-libs" VIDEO_CARDS="nouveau -intel (-omap) -radeon -vmware
(-exynos%)" 437 kB
[ebuild R ] virtual/udev-171 USE="acl%* gudev -hwdb -introspection
-keymap (-selinux) -static-libs" 0 kB
[ebuild R ] sys-apps/file-5.11 USE="python zlib -static-libs"
PYTHON_ABIS="2.7 3.2 -2.5 -2.6 -2.7-pypy-1.8% -2.7-pypy-1.9 -3.1 (-3.3)
(-2.7-pypy-2.0%) (-3.4%)" 0 kB

Total: 3 packages (1 downgrade, 2 reinstalls), Size of downloads: 437 kB

!!! Multiple package instances within a single package slot have been pulled
!!! into the dependency graph, resulting in a slot conflict:

x11-libs/libdrm:0

(x11-libs/libdrm-2.4.40::gentoo, installed) pulled in by
>=x11-libs/libdrm-2.4.34[video_cards_nouveau] required by
(x11-drivers/xf86-video-nouveau-1.0.4::gentoo, installed)

(x11-libs/libdrm-2.4.33::gentoo, ebuild scheduled for merge) pulled in by
<x11-libs/libdrm-2.4.34 required by
(media-libs/mesa-8.0.4-r1::gentoo, installed)

It may be possible to solve this problem by using package.mask to
prevent one of those packages from being selected. However, it is also
possible that conflicting dependencies exist such that they are
impossible to satisfy simultaneously. If such a conflict exists in
the dependencies of two different packages, then those packages can
not be installed simultaneously. You may want to try a larger value of
the --backtrack option, such as --backtrack=30, in order to see if
that will solve this conflict automatically.

For more information, see MASKED PACKAGES section in the emerge man
page or refer to the Gentoo Handbook.

funtoo ~ # emerge --info
Portage 2.3.5-r5 (funtoo/1.0/linux-gnu/arch/x86-64bit, gcc-4.6.3,
glibc-2.15-r3, 3.5.7-gentoo x86_64)
=================================================================
System uname:
Linux-3.5.7-gentoo-x86_64-Intel-R-Core-TM-_i7_CPU_Q_720@_1.60GHz-with-gentoo-2.2.0
Timestamp of tree: Wed, 19 Dec 2012 18:45:01 +0000
ld GNU ld (GNU Binutils) 2.22
ccache version 3.1.8 [enabled]
app-shells/bash: 4.2_p37
dev-lang/python: 2.7.3-r1000, 3.2.3-r1000
dev-util/ccache: 3.1.8
dev-util/cmake: 2.8.9
dev-util/pkgconfig: 0.27.1
sys-apps/baselayout: 2.2.0-r3
sys-apps/openrc: 0.10.2-r7
sys-apps/sandbox: 2.5
sys-devel/autoconf: 2.13, 2.68
sys-devel/automake: 1.11.6
sys-devel/binutils: 2.22-r1
sys-devel/gcc: 4.6.3
sys-devel/gcc-config: 1.5-r1
sys-devel/libtool: 2.4-r3
sys-devel/make: 3.82-r4
sys-kernel/linux-headers: 3.4-r2 (virtual/os-headers)
sys-libs/glibc: 2.15-r3
Repositories: gentoo
ACCEPT_KEYWORDS="amd64"
ACCEPT_LICENSE="* -@EULA"
CBUILD="x86_64-pc-linux-gnu"
CFLAGS="-march=native -msse4 -mcx16 -msahf -O2 -pipe"
CHOST="x86_64-pc-linux-gnu"
CONFIG_PROTECT="/etc /usr/share/gnupg/qualified.txt"
CONFIG_PROTECT_MASK="/etc/ca-certificates.conf /etc/dconf /etc/env.d
/etc/fonts/fonts.conf /etc/gconf /etc/gentoo-release /etc/revdep-rebuild
/etc/sandbox.d /etc/terminfo /etc/texmf/language.dat.d
/etc/texmf/language.def.d /etc/texmf/updmap.d /etc/texmf/web2c
/etc/udev/rules.d"
CXXFLAGS="-march=native -msse4 -mcx16 -msahf -O2 -pipe"
DISTDIR="/usr/portage/distfiles"
FEATURES="assume-digests binpkg-logs ccache config-protect-if-modified
distlocks ebuild-locks fixlafiles merge-sync news parallel-fetch
preserve-libs protect-owned sandbox sfperms strict unknown-features-warn
unmerge-logs unmerge-orphans userfetch"
FFLAGS=""
GENTOO_MIRRORS="rsync://mirrors.xmu.edu.cn/gentoo/
http://mirrors.xmu.edu.cn/gentoo ftp://mirrors.xmu.edu.cn/gentoo"
LANG="en_US.UTF-8"
LDFLAGS="Wl,-O1 -Wl,sort-common -Wl,-as-needed"
LINGUAS="en zh zh_CN"
MAKEOPTS="-j9"
PKGDIR="/usr/portage/packages"
PORTAGE_CONFIGROOT="/"
PORTAGE_TMPDIR="/var/tmp"
PORTDIR="/usr/portage"
PORTDIR_OVERLAY=""
SYNC="git://github.com/funtoo/ports-2012.git"
SYNC_USER="root"
USE="X acl alsa amd64 berkdb bzip2 cdr cracklib crypt cups cxx dbus dri
dvd dvdr dvdread flac gdbm gif gpm hal iconv icu ipv6 jpeg lame mad mmx
modules mp3 mpeg mudflap multilib ncurses nls nptl ogg opengl openmp pam
pcre png policykit pppd python readline resolvconf sse sse2 ssl tcpd
tiff truetype udev unicode vorbis wavpack xml xorg zlib"
ALSA_CARDS="ali5451 als4000 atiixp atiixp-modem bt87x ca0106 cmipci
emu10k1x ens1370 ens1371 es1938 es1968 fm801 hda-intel intel8x0
intel8x0m maestro3 trident usb-audio via82xx via82xx-modem ymfpci"
ALSA_PCM_PLUGINS="adpcm alaw asym copy dmix dshare dsnoop empty extplug
file hooks iec958 ioplug ladspa lfloat linear meter mmap_emul mulaw
multi null plug rate route share shm softvol" APACHE2_MODULES="actions
alias auth_basic authn_alias authn_anon authn_dbm authn_default
authn_file authz_dbm authz_default authz_groupfile authz_host
authz_owner authz_user autoindex cache cgi cgid dav dav_fs dav_lock
deflate dir disk_cache env expires ext_filter file_cache filter headers
include info log_config logio mem_cache mime mime_magic negotiation
rewrite setenvif speling status unique_id userdir usertrack vhost_alias
authn_core authz_core socache_shmcb unixd" CALLIGRA_FEATURES="kexi words
flow plan sheets stage tables krita karbon braindump" CAMERAS="ptp2"
COLLECTD_PLUGINS="df interface irq load memory rrdtool swap syslog"
ELIBC="glibc" GPSD_PROTOCOLS="ashtech aivdm earthmate evermore fv18
garmin garmintxt gpsclock itrax mtk3301 nmea ntrip navcom oceanserver
oldstyle oncore rtcm104v2 rtcm104v3 sirf superstar2 timing tsip tripmate
tnt ubx" INPUT_DEVICES="mouse keyboard evdev synaptics" KERNEL="linux"
LCD_DEVICES="bayrad cfontz cfontz633 glk hd44780 lb216 lcdm001 mtxorb
ncurses text" LIBREOFFICE_EXTENSIONS="presenter-console
presenter-minimizer" LINGUAS="en zh zh_CN" PHP_TARGETS="php5-3"
PYTHON_ABIS="2.7 3.2" PYTHON_SINGLE_TARGET="python2_7"
PYTHON_TARGETS="python2_7 python3_2" QEMU_SOFTMMU_TARGETS="i386 x86_64"
QEMU_USER_TARGETS="i386 x86_64" RUBY_TARGETS="ruby18 ruby19"
USERLAND="GNU" VIDEO_CARDS="nouveau" XTABLES_ADDONS="quota2 psd pknock
lscan length2 ipv4options ipset ipp2p iface geoip fuzzy condition tee
tarpit sysrq steal rawnat logmark ipmark dhcpmac delude chaos account"
Unset: CPPFLAGS, CTARGET, EMERGE_DEFAULT_OPTS, INSTALL_MASK, LC_ALL,
PORTAGE_BUNZIP2_COMMAND, PORTAGE_COMPRESS, PORTAGE_COMPRESS_FLAGS,
SYNC_UMASK

funtoo ~ # cat /var/lib/portage/world
app-admin/sudo
app-editors/vim
app-i18n/scim
app-i18n/scim-tables
app-misc/screen
app-portage/gentoolkit
app-text/evince
app-vim/vim-latex
dev-lang/go
dev-lang/ruby
dev-python/markdown
dev-python/pysqlite
dev-tex/latex-beamer
dev-texlive/texlive-xetex
dev-util/ccache
mail-client/mutt
mail-client/thunderbird
media-libs/mesa
media-sound/alsa-utils
media-video/mplayer
net-irc/irssi
net-misc/dhcpcd
net-misc/htpdate
net-p2p/rtorrent
net-wireless/wpa_supplicant
sci-electronics/ghdl
sys-apps/openrc
sys-apps/pcmciautils
sys-apps/portage
sys-boot/grub
sys-fs/btrfs-progs
sys-kernel/genkernel
sys-kernel/gentoo-sources
www-client/firefox
www-plugins/adobe-flash
www-plugins/google-talkplugin
x11-apps/xmodmap
x11-base/xorg-server
x11-terms/terminal
xfce-base/xfce4-meta