Why gtk_label_set_justify(GTK_LABEL(label), GTK_JUSTIFY_LEFT) does not work?

["Ye Chao" <yeajchao gmail com>]

Hello  all:
        In my application ,
        I want the label's text left align,
       So i use gtk_label_set_justify(GTK_LABEL(label),GTK_JUSTIFY_LEFT) ,
       but it does not work ,
       why?
     Thank you very much!