This package could use some love, it's many versions out of date. The latest is version 7.0, released this past April.
missing ||die and local in the ebuild You can help the maintainer with further information: Does a simple bump [1] work on your system? Chances are high, because a first look on the bump revealed only small changes. [1] https://wiki.gentoo.org/wiki/Custom_repository#Simple_version_bump_of_an_ebuild_in_the_local_overlay
The bug has been closed via the following commit(s): https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=b0dfba538a60dc3e1f36179b5c825afa994096a2 commit b0dfba538a60dc3e1f36179b5c825afa994096a2 Author: Alon Bar-Lev <alonbl@gentoo.org> AuthorDate: 2018-05-01 19:14:02 +0000 Commit: Alon Bar-Lev <alonbl@gentoo.org> CommitDate: 2018-05-01 19:15:35 +0000 dev-libs/crypto++: version bump Closes: https://bugs.gentoo.org/show_bug.cgi?id=654550 Package-Manager: Portage-2.3.24, Repoman-2.3.6 dev-libs/crypto++/Manifest | 1 + dev-libs/crypto++/crypto++-7.0.0.ebuild | 47 +++++++++++++++++++++++++++++++++ dev-libs/crypto++/metadata.xml | 6 +++++ 3 files changed, 54 insertions(+)