Eigen-3.2.6 was released on 1th October: http://eigen.tuxfamily.org/index.php?title=ChangeLog#Eigen_3.2.6 It's a bugfix release and the old 3.2.5::gentoo ebuild works for me here. Reproducible: Always
Thanks, fixed in git. https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=fe45934b8cc4479661e2996086fc82f2fd0f8db5