USE=cxx was dropped from make.defaults in base profile. The usedep is required by multiple packages.
Th overhead will be around 30K on disk, sounds reasonable. A few users: $ git grep dev-libs/gmp | fgrep cxx app-office/libalkimia/libalkimia-7.0.2-r1.ebuild: gmp? ( dev-libs/gmp:0=[cxx] ) dev-lang/maude/maude-2.7.ebuild: dev-libs/gmp:0=[cxx] dev-libs/ppl/ppl-1.1.ebuild:RDEPEND=">=dev-libs/gmp-6[cxx] dev-libs/ppl/ppl-1.2-r1.ebuild:RDEPEND=">=dev-libs/gmp-6[cxx] dev-libs/ppl/ppl-1.2.ebuild:RDEPEND=">=dev-libs/gmp-6[cxx] sci-libs/givaro/givaro-4.1.1.ebuild:DEPEND="dev-libs/gmp:0[cxx]" sci-libs/libint/libint-2.0.5.ebuild: dev-libs/gmp[cxx] sci-mathematics/4ti2/4ti2-1.6.2.ebuild: dev-libs/gmp[cxx]" sci-mathematics/4ti2/4ti2-1.6.5.ebuild: dev-libs/gmp[cxx]" sci-mathematics/4ti2/4ti2-1.6.6.ebuild: dev-libs/gmp[cxx]" sci-mathematics/4ti2/4ti2-1.6.7.ebuild: dev-libs/gmp:0=[cxx]" sci-mathematics/cgal/cgal-4.11.3.ebuild: gmp? ( dev-libs/gmp:=[cxx] ) sci-mathematics/frobby/frobby-0.9.0-r2.ebuild:RDEPEND="dev-libs/gmp:0=[cxx]" sci-mathematics/gfan/gfan-0.5-r1.ebuild: dev-libs/gmp:0=[cxx] sci-mathematics/gfan/gfan-0.6.2.ebuild:DEPEND="dev-libs/gmp:0=[cxx] sci-mathematics/normaliz/normaliz-2.12.2.ebuild:RDEPEND="dev-libs/gmp[cxx]" sci-mathematics/normaliz/normaliz-3.1.1.ebuild:RDEPEND="dev-libs/gmp[cxx]" sci-mathematics/normaliz/normaliz-3.1.3.ebuild: dev-libs/gmp[cxx] sci-mathematics/normaliz/normaliz-3.3.0.ebuild: dev-libs/gmp:=[cxx] sci-mathematics/z3/z3-4.8.6.ebuild: gmp? ( dev-libs/gmp:0=[cxx,${MULTILIB_USEDEP}] )"
The bug has been closed via the following commit(s): https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=f8afd2fe54481894dd5f0b20219bfca0ae922e63 commit f8afd2fe54481894dd5f0b20219bfca0ae922e63 Author: Sergei Trofimovich <slyfox@gentoo.org> AuthorDate: 2020-03-26 21:47:08 +0000 Commit: Sergei Trofimovich <slyfox@gentoo.org> CommitDate: 2020-03-26 21:47:32 +0000 dev-libs/gmp: enable IUSE=+cxx by default, bug #714928 Reported-by: Andreas Sturmlechner Closes: https://bugs.gentoo.org/714928 Package-Manager: Portage-2.3.96, Repoman-2.3.22 Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org> dev-libs/gmp/gmp-6.1.2-r1.ebuild | 2 +- dev-libs/gmp/gmp-6.1.2.ebuild | 2 +- dev-libs/gmp/gmp-6.2.0-r1.ebuild | 2 +- 3 files changed, 3 insertions(+), 3 deletions(-)