mail-client/roundcube-1.3.3 depends on dev-lang/php[crypt]. The crypt USE flag was removed from php 7.2 (bug 639286) because upstream removed it: https://wiki.php.net/rfc/mcrypt-viking-funeral Looking through https://github.com/roundcube/roundcubemail/blob/1.3.3 it doesn't look like mcrypt is used, so simply updating the ebuild to remove this requirement should suffice.
Also, I've tested roundcube with PHP 7.2 and haven't experienced any problems.
The bug has been closed via the following commit(s): https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=19b244aeb7fe3eba32a301d329091c065ea1c750 commit 19b244aeb7fe3eba32a301d329091c065ea1c750 Author: Craig Andrews <candrews@gentoo.org> AuthorDate: 2017-12-01 17:04:54 +0000 Commit: Craig Andrews <candrews@gentoo.org> CommitDate: 2017-12-07 15:49:11 +0000 mail-client/roundcube: Don't depend on dev-lang/php[crypt] The crypt use flag was removed in dev-lang/php-7.2 and roundcube doesn't use it Closes: https://bugs.gentoo.org/639394 Package-Manager: Portage-2.3.16, Repoman-2.3.6 mail-client/roundcube/Manifest | 10 ++-- mail-client/roundcube/roundcube-1.3.3-r1.ebuild | 76 +++++++++++++++++++++++++ 2 files changed, 81 insertions(+), 5 deletions(-)