Guarda che te lo scrive quando fai emerge depclean...

*** WARNING *** : DEPCLEAN CAN SERIOUSLY IMPAIR YOUR SYSTEM. USE CAUTION.
*** WARNING *** : (Cancel: CONTROL-C) -- ALWAYS VERIFY ALL PACKAGES IN THE
*** WARNING *** : CANDIDATE LIST FOR SANITY BEFORE ALLOWING DEPCLEAN TO
*** WARNING *** : UNMERGE ANY PACKAGES.
*** WARNING *** :
*** WARNING *** : USE FLAGS MAY HAVE AN EXTREME EFFECT ON THE OUTPUT.
*** WARNING *** : SOME LIBRARIES MAY BE USED BY PACKAGES BUT ARE NOT
*** WARNING *** : CONSIDERED TO BE A DEPEND DUE TO USE FLAG SETTINGS.
*** WARNING *** :
*** WARNING *** : Packages in the list that are desired may be added
*** WARNING *** : directly to the world file to cause them to be ignored
*** WARNING *** : by depclean and maintained in the future. BREAKAGES DUE
*** WARNING *** : TO UNMERGING AN ==IN-USE LIBRARY== MAY BE REPAIRED BY
*** WARNING *** : MERGING *** THE PACKAGE THAT COMPLAINS *** ABOUT THE
*** WARNING *** : MISSING LIBRARY.