While emerging media-sound/lilypond-1.14.2, get below errors. This is because it emerges media-libs/openjpeg-1.5.0. To fix this I had to "emerge =openjpeg-1.4-r1" /usr/lib/gcc/x86_64-pc-linux-gnu/4.5.3/../../../../x86_64-pc-linux-gnu/bin/ld: warning: libopenjpeg.so.1.4, needed by /usr/lib/gcc/x86_64-pc-linux-gnu/4.5.3/../../../../lib64/libpoppler.so, not found (try using -rpath or -rpath-link) /usr/lib/gcc/x86_64-pc-linux-gnu/4.5.3/../../../../lib64/libpoppler.so: undefined reference to `opj_set_event_mgr'
revdep-rebuild is your friend.