GtkTreeView warnings

gtk_tree_view.c

#include <gtk/gtk.h>

static void activate_main (GtkApplication *app, gpointer user_data);
static void setup_tree_view (GtkWidget *treeview);
static void populate_tree_store (GtkTreeStore *store);

int
main (int   argc,
      char  **argv)
{
    GtkApplication  *app;
    int status;

    app = gtk_application_new (NULL, G_APPLICATION_FLAGS_NONE);
    g_signal_connect(app, "activate", G_CALLBACK (activate_main), NULL);
    status = g_application_run (G_APPLICATION (app), argc, argv);
    g_object_unref (app);

    return status;
}

static void
activate_main (GtkApplication *app,
               gpointer user_data)
{
    GtkWidget *window, *scrolled_win;
    GtkWidget *treeview;
    GtkWidget *toolbar;
    GtkToolItem *expand_tree_view_button, *collapse_tree_view_button;
    GtkWidget *image;
    GtkWidget *status_bar;
    guint context_id;
    GtkWidget *master_grid;

    window = gtk_application_window_new (app);
    gtk_window_set_title (GTK_WINDOW (window), "Gtk Tree View");
    gtk_widget_set_size_request(window, 1280, 720);
    gtk_container_set_border_width (GTK_CONTAINER (window), 10);

    GtkTreeStore *store;
    store = gtk_tree_store_new (3, G_TYPE_STRING, G_TYPE_STRING, G_TYPE_STRING);
    populate_tree_store (store);

    treeview = gtk_tree_view_new_with_model (GTK_TREE_MODEL (store));
    g_object_unref (store);
    gtk_widget_set_hexpand (treeview, TRUE);
    gtk_widget_set_vexpand (treeview, TRUE);
    setup_tree_view (treeview);

    scrolled_win = gtk_scrolled_window_new (NULL, NULL);
    gtk_container_add (GTK_CONTAINER (scrolled_win), treeview);

    toolbar = gtk_toolbar_new ();

    image = gtk_image_new_from_icon_name ("list-add", GTK_ICON_SIZE_SMALL_TOOLBAR);
    expand_tree_view_button = gtk_tool_button_new (image, NULL);

    image = gtk_image_new_from_icon_name ("list-remove", GTK_ICON_SIZE_SMALL_TOOLBAR);
    collapse_tree_view_button = gtk_tool_button_new (image, NULL);

    gtk_toolbar_insert (GTK_TOOLBAR (toolbar), expand_tree_view_button, -1);
    gtk_toolbar_insert (GTK_TOOLBAR (toolbar), collapse_tree_view_button, -1);

    g_signal_connect_swapped (expand_tree_view_button, "clicked", 
                      G_CALLBACK (gtk_tree_view_expand_all), GTK_TREE_VIEW (treeview));
    g_signal_connect_swapped (collapse_tree_view_button, "clicked", 
                      G_CALLBACK (gtk_tree_view_collapse_all), GTK_TREE_VIEW (treeview));

    status_bar = gtk_statusbar_new ();
    context_id = gtk_statusbar_get_context_id (GTK_STATUSBAR (status_bar), "Status Message");
    gtk_statusbar_push (GTK_STATUSBAR (status_bar), context_id, "A status message.");

    master_grid = gtk_grid_new ();
    gtk_grid_attach (GTK_GRID (master_grid), toolbar, 0, 0, 1, 1);
    gtk_grid_attach (GTK_GRID (master_grid), scrolled_win, 0, 1, 1, 1);
    gtk_grid_attach (GTK_GRID (master_grid), status_bar, 0, 2, 1, 1);

    gtk_container_add (GTK_CONTAINER (window), master_grid);

    gtk_widget_show_all (window);
}

static void
populate_tree_store (GtkTreeStore *store)
{
    GtkTreeIter item1, item2, item3;
    for (int i = 0; i < 100; i++)
    {
        gtk_tree_store_append (store, &item1, NULL);
        gtk_tree_store_set (store, &item1,
                            0, g_strdup_printf ("Window %d", i + 1),
                            1, "12345678",
                            2, "ClassName",
                            -1);
        for (int j = 0; j < 3; j++)
        {
            gtk_tree_store_append (store, &item2, &item1);
            gtk_tree_store_set (store, &item2,
                                0, g_strdup_printf ("Window %d%d", i + 1, i + 2),
                                1, "12345678",
                                2, "ClassName",
                                -1);
            for (int k = 0; k < 5; k++)
            {
                gtk_tree_store_append (store, &item3, &item2);
                gtk_tree_store_set (store, &item3,
                                    0, g_strdup_printf ("Window %d%d%d", i + 1, j + 1, k+ 1),
                                    1, "12345678",
                                    2, "ClassName",
                                    -1);
            }
        }
    }
}

static void
setup_tree_view (GtkWidget *treeview)
{
    GtkTreeViewColumn *window_column, *handle_column, *class_column;
    GtkCellRenderer *renderer;

    renderer = gtk_cell_renderer_text_new ();
    window_column = gtk_tree_view_column_new_with_attributes
        ("Window", renderer, "text", 0, NULL);
    gtk_tree_view_column_set_resizable (window_column, TRUE);

    renderer = gtk_cell_renderer_text_new ();
    handle_column = gtk_tree_view_column_new_with_attributes
        ("Handle", renderer, "text", 1, NULL);

    renderer = gtk_cell_renderer_text_new ();
    class_column = gtk_tree_view_column_new_with_attributes
        ("Class", renderer, "text", 2, NULL);

    gtk_tree_view_append_column (GTK_TREE_VIEW (treeview), handle_column);
    gtk_tree_view_append_column (GTK_TREE_VIEW (treeview), window_column);
    gtk_tree_view_append_column (GTK_TREE_VIEW (treeview), class_column);
}

Problem appears even in GTKmm... Somebody, report bug...