Encountered it while building stages, autotools.eclass DEPENDs on sys-devel/libtool, and libtool-2.2.6a.ebuild uses the autotools.eclass. Reproducible by unmerging libtool and trying to emerge it again: dschubba / # emerge libtool Calculating dependencies... done! [ebuild N ] sys-devel/libtool-2.2.6a USE="-vanilla" * Error: circular dependencies: ('ebuild', '/', 'sys-devel/libtool-2.2.6a', 'merge') depends on ('ebuild', '/', 'sys-devel/libtool-2.2.6a', 'merge') (hard) * Note that circular dependencies can often be avoided by temporarily * disabling USE flags that trigger optional dependencies. Emerges just fine if --nodeps.
hacked in autotools.eclass http://sources.gentoo.org/eclass/autotools.eclass?r1=1.81&r2=1.82