emerge world -uDpv

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

Calculating world dependencies... done!
[ebuild     U ] sys-libs/libieee1284-0.2.8 [0.2.1] USE="doc" 0 kB
[ebuild  N    ] net-misc/mDNSResponder-107.6-r5  USE="doc java -debug" 0 kB
[ebuild  N    ] dev-cpp/cairomm-1.2.4  USE="doc examples" 0 kB
[ebuild     U ] dev-cpp/gtkmm-2.10.9 [2.8.3] USE="accessibility%* doc%* examples%* -debug" 0 kB
[ebuild     U ] dev-cpp/libglademm-2.6.3 [2.6.2] USE="doc%* examples%* -debug" 0 kB
[ebuild  N    ] net-dns/avahi-0.6.20  USE="autoipd bookmarks dbus doc gdbm gtk howl-compat mdnsresponder-compat mono python qt3 qt4 test" 0 kB
[ebuild     U ] app-text/gocr-0.43 [0.40-r2] USE="doc gtk tk%*" 0 kB
[blocks B     ] net-dns/avahi (is blocking net-misc/mDNSResponder-107.6-r5)
[blocks B     ] net-misc/mDNSResponder (is blocking net-dns/avahi-0.6.20)

Total: 7 packages (4 upgrades, 3 new, 2 blocks), Size of downloads: 0 kB