Gentoo's Bugzilla –
Attachment 486152 Details for
Bug 625774net-libs/onion-0.8 will not build with USE libevent: /var/tmp/portage/net-libs/onion-0.8/work/onion-0.8/src/onion/poller_libevent.c:80:6: error: conflicting types for 'onion_poller_slot_set_type'