$ sudo emerge --oneshot portage
Password:
Calculating dependencies... done!
[ebuild     U  ] virtual/libiconv-0-r1 [0] ABI_X86="32%* (64%*) (-x32)"
[ebuild     U  ] dev-libs/libffi-3.0.13-r1 [3.0.13] ABI_X86="32%* (64%*) (-x32)"
[ebuild     U  ] sys-libs/zlib-1.2.8-r1 [1.2.8] ABI_X86="32%* (64%*) (-x32)"
[ebuild     U  ] virtual/libffi-3.0.13-r1 [3.0.11] ABI_X86="32%* (64%*) (-x32)"
[ebuild     U  ] sys-apps/attr-2.4.47-r1 [2.4.47] ABI_X86="32%* (64%*) (-x32)"
[ebuild     U  ] net-im/telepathy-logger-0.8.0 [0.6.0]
[ebuild     U  ] sys-apps/portage-2.2.7 [2.1.12.8]
[ebuild     U  ] dev-libs/glib-2.36.4-r1 [2.34.3] ABI_X86="32%* (64%*) (-x32)" PYTHON_TARGETS="python2_7%* -python2_6%"
[ebuild     U  ] net-libs/libsoup-2.42.2-r1 [2.40.3]
[ebuild     U  ] net-libs/gnome-online-accounts-3.8.3 [3.6.3]
[ebuild     U  ] gnome-extra/evolution-data-server-3.8.5 [3.6.4] USE="gtk%* vala*"
[ebuild     U  ] dev-libs/folks-0.9.3 [0.8.0] USE="-zeitgeist%"
[ebuild  r  U  ] net-im/empathy-3.8.4 [3.6.4]
[ebuild  r  U  ] app-emulation/wine-1.7.0 [1.6_rc2] USE="-dos%"
[blocks B      ] app-emulation/emul-linux-x86-baselibs[-abi_x86_32(-)] ("app-emulation/emul-linux-x86-baselibs[-abi_x86_32(-)]" is blocking dev-libs/libffi-3.0.13-r1)
[blocks B      ] app-emulation/emul-linux-x86-baselibs[-abi_x86_32(-)] ("app-emulation/emul-linux-x86-baselibs[-abi_x86_32(-)]" is blocking sys-apps/attr-2.4.47-r1)
[blocks B      ] <=app-emulation/emul-linux-x86-baselibs-20130224-r1 ("<=app-emulation/emul-linux-x86-baselibs-20130224-r1" is blocking dev-libs/libffi-3.0.13-r1)
[blocks B      ] <=app-emulation/emul-linux-x86-baselibs-20130224-r9 ("<=app-emulation/emul-linux-x86-baselibs-20130224-r9" is blocking sys-apps/attr-2.4.47-r1)

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

net-libs/gnome-online-accounts:0

  (net-libs/gnome-online-accounts-3.6.3::gentoo, installed) pulled in by
    (no parents that aren't satisfied by other packages in this slot)

  (net-libs/gnome-online-accounts-3.8.3::gentoo, ebuild scheduled for merge) pulled in by
    >=net-libs/gnome-online-accounts-3.7.90 required by (gnome-extra/evolution-data-server-3.8.5::gentoo, ebuild scheduled for merge)

dev-libs/glib:2

  (dev-libs/glib-2.34.3::gentoo, installed) pulled in by
    (no parents that aren't satisfied by other packages in this slot)

  (dev-libs/glib-2.36.4-r1::gentoo, ebuild scheduled for merge) pulled in by
    >=dev-libs/glib-2.36.0:2 required by (net-libs/libsoup-2.42.2-r1::gentoo, ebuild scheduled for merge)
    (and 1 more with the same problem)

net-libs/libsoup:2.4

  (net-libs/libsoup-2.42.2-r1::gentoo, ebuild scheduled for merge) pulled in by
    >=net-libs/libsoup-2.42:2.4 required by (net-libs/gnome-online-accounts-3.8.3::gentoo, ebuild scheduled for merge)

  (net-libs/libsoup-2.40.3::gentoo, installed) pulled in by
    ~net-libs/libsoup-2.40.3[introspection?] required by (net-libs/libsoup-gnome-2.40.3::gentoo, installed)

sys-libs/zlib:0

  (sys-libs/zlib-1.2.8-r1::gentoo, ebuild scheduled for merge) pulled in by
    sys-libs/zlib[abi_x86_32(-)?,abi_x86_64(-)?,abi_x86_x32(-)?,abi_mips_n32(-)?,abi_mips_n64(-)?,abi_mips_o32(-)?] required by (dev-libs/glib-2.36.4-r1::gentoo, ebuild scheduled for merge)

  (sys-libs/zlib-1.2.8::gentoo, installed) pulled in by
    (no parents that aren't satisfied by other packages in this slot)

gnome-extra/evolution-data-server:0

  (gnome-extra/evolution-data-server-3.6.4::gentoo, installed) pulled in by
    =gnome-extra/evolution-data-server-3.6* required by (mail-client/evolution-3.6.4::gentoo, installed)
    (and 1 more with the same problem)

  (gnome-extra/evolution-data-server-3.8.5::gentoo, ebuild scheduled for merge) pulled in by
    >=gnome-extra/evolution-data-server-3.8.1:=[vala] required by (dev-libs/folks-0.9.3::gentoo, ebuild scheduled for merge)


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.


 * Error: The above package list contains packages which cannot be
 * installed at the same time on the same system.

  (app-emulation/emul-linux-x86-baselibs-20130224::gentoo, installed) pulled in by
    ~app-emulation/emul-linux-x86-baselibs-20130224 required by (app-emulation/emul-linux-x86-xlibs-20130224-r1::gentoo, installed)
    ~app-emulation/emul-linux-x86-baselibs-20130224 required by (app-emulation/emul-linux-x86-db-20130224::gentoo, installed)
    ~app-emulation/emul-linux-x86-baselibs-20130224 required by (app-emulation/emul-linux-x86-medialibs-20130224::gentoo, installed)
    app-emulation/emul-linux-x86-baselibs[development] required by (x11-libs/libpciaccess-0.13.1-r1::gentoo, installed)
    ~app-emulation/emul-linux-x86-baselibs-20130224 required by (app-emulation/emul-linux-x86-gstplugins-20130224::gentoo, installed)
    >=app-emulation/emul-linux-x86-baselibs-20130224[development] required by (app-emulation/wine-1.7.0::gentoo, ebuild scheduled for merge)
    app-emulation/emul-linux-x86-baselibs[development] required by (media-libs/fontconfig-2.10.2-r1::gentoo, installed)
    app-emulation/emul-linux-x86-baselibs[development] required by (x11-libs/libSM-1.2.1-r1::gentoo, installed)
    ~app-emulation/emul-linux-x86-baselibs-20130224 required by (app-emulation/emul-linux-x86-soundlibs-20130224::gentoo, installed)
    app-emulation/emul-linux-x86-baselibs required by (media-libs/jasper-1.900.1-r6::gentoo, installed)
    ~app-emulation/emul-linux-x86-baselibs-20130224 required by (app-emulation/emul-linux-x86-qtlibs-20130224::gentoo, installed)
    app-emulation/emul-linux-x86-baselibs required by (net-misc/teamviewer-8.0.17147-r2::gentoo, installed)
    ~app-emulation/emul-linux-x86-baselibs-20130224 required by (app-emulation/emul-linux-x86-gtklibs-20130224::gentoo, installed)
    >=app-emulation/emul-linux-x86-baselibs-20120520 required by (net-im/skype-4.2.0.11::gentoo, installed)

  (dev-libs/libffi-3.0.13-r1::gentoo, ebuild scheduled for merge) pulled in by
    >=dev-libs/libffi-3.0.13-r1[abi_x86_32(-)?,abi_x86_64(-)?,abi_x86_x32(-)?,abi_mips_n32(-)?,abi_mips_n64(-)?,abi_mips_o32(-)?] (>=dev-libs/libffi-3.0.13-r1[abi_x86_32(-),abi_x86_64(-)]) required by (virtual/libffi-3.0.13-r1::gentoo, ebuild scheduled for merge)

  (sys-apps/attr-2.4.47-r1::gentoo, ebuild scheduled for merge) pulled in by
    sys-apps/attr required by (net-print/cups-1.6.2-r5::gentoo, installed)
    sys-apps/attr required by (sys-libs/libcap-2.22-r1::gentoo, installed)
    sys-apps/attr required by (sys-apps/shadow-4.1.5.1-r1::gentoo, installed)
    sys-apps/attr required by (net-misc/rsync-3.0.9-r2::gentoo, installed)
    sys-apps/attr required by (sys-apps/coreutils-8.21::gentoo, installed)
    sys-apps/attr required by (dev-libs/libisofs-1.3.0::gentoo, installed)
    sys-apps/attr required by (gnome-base/gnome-vfs-2.24.4-r1::gentoo, installed)
    >=sys-apps/attr-2.4 required by (sys-apps/acl-2.2.52::gentoo, installed)
    sys-apps/attr required by (dev-libs/glib-2.34.3::gentoo, installed)
    sys-apps/attr required by (sys-devel/patch-2.7.1-r1::gentoo, installed)
    sys-apps/attr required by (app-arch/libarchive-3.1.2-r1::gentoo, installed)
    sys-apps/attr[abi_x86_32(-)?,abi_x86_64(-)?,abi_x86_x32(-)?,abi_mips_n32(-)?,abi_mips_n64(-)?,abi_mips_o32(-)?] (sys-apps/attr[abi_x86_32(-),abi_x86_64(-)]) required by (dev-libs/glib-2.36.4-r1::gentoo, ebuild scheduled for merge)
    sys-apps/attr required by (app-arch/tar-1.26-r1::gentoo, installed)


For more information about Blocked Packages, please refer to the following
section of the Gentoo Linux x86 Handbook (architecture is irrelevant):

http://www.gentoo.org/doc/en/handbook/handbook-x86.xml?full=1#blocked