--- /usr/portage/eclass/gems.eclass	2008-02-17 09:05:59.000000000 +0000
+++ gems.eclass	2008-07-04 23:03:09.000000000 +0100
@@ -10,10 +10,13 @@
 # the Gentoo Linux system.
 #
 # - Features:
-# gems_location()	  - Set ${GEMSDIR} with gem install dir and ${GEM_SRC} with path to gem to install
+# gems_location()	  - Set ${GEMSDIR} with gem install dir and ${GEM_SRC} with
+# 						path to gem to install. Optionally takes a ruby version string, like 
+#						"ruby18" as a parameter.
 # gems_src_unpack()	  - Does nothing.
 # gems_src_compile()  - Does nothing.
-# gems_src_install()  - installs a gem into ${D}
+# gems_src_install()  - installs a gem into ${D} using each ruby version that is both 
+# 						installed and specified in USE_RUBY.
 #
 # NOTE:
 # See http://dev.gentoo.org/~pythonhead/ruby/gems.html for notes on using gems with portage
@@ -33,9 +36,14 @@
 
 gems_location() {
 	local sitelibdir
-	sitelibdir=$(ruby -r rbconfig -e 'print Config::CONFIG["sitelibdir"]')
+	local ruby_version
+	if [[ -z "$1" ]]; then
+		ruby_version="ruby"
+	else
+		ruby_version=$1
+	fi
+	sitelibdir=$(/usr/bin/${ruby_version} -r rbconfig -e 'print Config::CONFIG["sitelibdir"]')
 	export GEMSDIR=${sitelibdir/site_ruby/gems}
-
 }
 
 gems_src_unpack() {
@@ -47,16 +55,6 @@
 }
 
 gems_src_install() {
-	gems_location
-
-	if [[ -z "${MY_P}" ]]; then
-		[[ -z "${GEM_SRC}" ]] && GEM_SRC="${DISTDIR}/${P}"
-		spec_path="${D}/${GEMSDIR}/specifications/${P}.gemspec"
-	else
-		[[ -z "${GEM_SRC}" ]] && GEM_SRC="${DISTDIR}/${MY_P}"
-		spec_path="${D}/${GEMSDIR}/specifications/${MY_P}.gemspec"
-	fi
-
 	local myconf
 	if use doc; then
 		myconf="--rdoc --ri"
@@ -64,16 +62,46 @@
 		myconf="--no-rdoc --no-ri"
 	fi
 
-	dodir ${GEMSDIR}
-	gem install ${GEM_SRC} --version ${PV} ${myconf} \
-		--local --install-dir "${D}/${GEMSDIR}" || die "gem install failed"
-
-	if [[ -d "${D}/${GEMSDIR}/bin" ]] ; then
-		exeinto /usr/bin
-		for exe in ${D}/${GEMSDIR}/bin/* ; do
-			doexe ${exe}
-		done
+	# I'm not sure how many ebuilds have correctly set USE_RUBY - let's assume
+	# ruby18 if they haven't, since even pure Ruby gems that have been written
+	# against 1.8 can explode under 1.9.
+	if [[ -z "${USE_RUBY}" ]]; then
+		USE_RUBY="ruby18"
+	elif [[ "${USE_RUBY}" == "any" ]]; then
+		# Get the installed versions.
+		USE_RUBY=`ls /usr/bin/ruby* | grep -E 'ruby1(8|9)' | sed -e 's@/usr/bin/@@g'`
 	fi
+
+	local num_ruby_slots=$(echo "${USE_RUBY}" | wc -w)
+
+	for ruby_version in ${USE_RUBY} ; do
+		einfo "Installing for ${ruby_version}..."
+		gems_location ${ruby_version}
+		dodir ${GEMSDIR}
+
+		if [[ -z "${MY_P}" ]]; then
+			[[ -z "${GEM_SRC}" ]] && GEM_SRC="${DISTDIR}/${P}"
+			spec_path="${D}/${GEMSDIR}/specifications/${P}.gemspec"
+		else
+			[[ -z "${GEM_SRC}" ]] && GEM_SRC="${DISTDIR}/${MY_P}"
+			spec_path="${D}/${GEMSDIR}/specifications/${MY_P}.gemspec"
+		fi
+
+		/usr/bin/${ruby_version} /usr/bin/gem install ${GEM_SRC} --version ${PV} ${myconf} \
+			--local --install-dir "${D}/${GEMSDIR}" || die "gem install failed"
+
+		if [[ -d "${D}/${GEMSDIR}/bin" ]] ; then
+			exeinto /usr/bin
+			for exe in ${D}/${GEMSDIR}/bin/* ; do
+				if [ "$num_ruby_slots" -ge 2 ] ; then
+					# Ensures that the exe file gets run using the currently
+					# selected version of ruby.
+					sed -i -e 's@^#!/usr/bin/ruby.*$@#!/usr/bin/ruby@' "${exe}"
+				fi
+				doexe ${exe}
+			done
+		fi
+	done
 }
 
 EXPORT_FUNCTIONS src_unpack src_compile src_install