# File lib/execjs/external_runtime.rb, line 22
      def exec(source, options = {})
        source = source.encode('UTF-8') if source.respond_to?(:encode)
        source = "#{@source}\n#{source}" if @source

        compile_to_tempfile(source) do |file|
          extract_result(@runtime.send(:exec_runtime, file.path))
        end
      end