Code in C++/gtkmm but it is the same bad for plain C:

    const char* path = "/var/tmp";
    Gtk::FileChooserButton btn("Select folder", Gtk::FILE_CHOOSER_ACTION_SELECT_FOLDER);

    assert( btn.set_filename(path) );

    //Gtk::Window win;
    //win.show_all();
    //Gtk::Main::run(win);
    while( Gtk::Main::instance()->events_pending() )
        Gtk::Main::instance()->iteration();
    
    // now btn.get_filename() == "/var", not "/var/tmp"!!!
    // CRASH!!!
    assert( strcmp(btn.get_filename().c_str(), path) == 0 );

This bug was introduced since 2.19; it is all ok for gtk+ <= 2.18.

The bug is not reproduced if I use:
- GTK_FILE_CHOOSER_ACTION_OPEN
- gtk_file_chooser_set_current_folder() instead of gtk_file_chooser_set_filename()

So, should I use gtk_file_chooser_set_current_folder() & gtk_file_chooser_get_filename() pair in SELECT_FOLDER mode (I think this is quite unnatural)? 
Is there is a policy/HIG for that?

For my application, Bombono DVD, this is the blocker because I use GtkFileChooser for temporary and empty folder. So, if the preference was "/home/user/tmp" I suggest now to delete contents of "/home/user" folder (Home Folder).