bugfix

        if (file.is_open()) {

            std::string content((std::istreambuf_iterator<char>(file)),

                                 std::istreambuf_iterator<char>());

            // An included makefile is parsed in its own conditional context and

            // must have balanced conditionals; it may not close a conditional

            // opened by the parent. parse_string() resets cond_stack_/define

            // state, so save and restore the parent's parsing state around the

            // recursive parse to keep the enclosing conditional nesting intact.

            auto saved_cond = cond_stack_;

            bool saved_in_define = in_define_;

            std::string saved_dname = define_name_, saved_dop = define_op_;

            std::vector<std::string> saved_dbody = define_body_;

            std::string saved_base = mf.base_dir;

            parse_string(content, mf);

            cond_stack_ = saved_cond;

            in_define_ = saved_in_define;

            define_name_ = saved_dname;

            define_op_ = saved_dop;

            define_body_ = saved_dbody;

            mf.base_dir = saved_base;

        }

    }

}