function dump_errors( $emask = null ) {
		foreach( $this->err_stack as $t => $ids ) {
			if( $emask !== NULL && ( $emask & $t ) == 0 ) {
				// ignore this error
				continue;
			}
			// dump these errors
			foreach( $ids as $id ){
				$Err = PLUGError::get_reference( $t, $id );
				echo (string) $Err;
				echo $Err->getTraceAsString(), "\n";
			}
		}
	}