bliss has a gmp useflag but at the moment it is ineffective. libbliss will be linked to gmp regardless of the value of the useflag. This is because there is a small mistake in the autotools patch +AC_ARG_WITH([gmp], + [AS_HELP_STRING([--with-gmp], [enable support for GNU Multiple Precision Arithmetic Library @<:@default=check@:>@])], + [], [with_readline=no]) +AS_IF([test "x$with_readline" != xno], + [AC_CHECK_HEADERS([gmp.h],,AC_MSG_ERROR([Cannot find gmp.h header])) + AC_CHECK_LIB([gmp],_init,,AC_MSG_ERROR([Cannot find gmp library])) + AC_SUBST([GMP],[-lgmp]) + [CPPFLAGS="$CPPFLAGS -DBLISS_USE_GMP"]]) Not that the default for AC_ARG_WITH is not with_gmp as it should be but with_readline. That would be ok if it was the only mistake but the substitution is repeated on the next line in the AS_IF statement. This will only work as expected if no --with-gmp or --without-gmp statement is passed to configure.
Fixed by https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=31ded7e602d4797cdd012e18bfeca3751ee5b875 Thank you Sébastian Fabbro.