private static BufferingPrologControl newEmptyMachine(ClassLoader cl) {
BufferingPrologControl ctl = new BufferingPrologControl();
ctl.setMaxArity(PrologEnvironment.MAX_ARITY);
ctl.setMaxDatabaseSize(DB_MAX);
ctl.setPrologClassLoader(new PrologClassLoader(cl));
ctl.setEnabled(EnumSet.allOf(Prolog.Feature.class), false);
// Bootstrap the interpreter and ensure there is clean state.
ctl.initialize(PACKAGE_LIST);
return ctl;