Version 2.8.7 is available upstream. Please consider updating! It seems that version 2.8.7 is available upstream, while the latest version in the Gentoo tree is 2.8.6. You think this warning is false? Read more about it here.
The p4est software library enables the dynamic management of a collection
of adaptive octrees, conveniently called a forest of octrees. p4est is
designed to work in parallel and scale to hundreds of thousands of
processor cores.