The difference between using GtkFileChooserButton and GtkFileChooserDialog

Question

I would like to let user choose two directories and then retrieve their URIs after the click of button so I could pass them to another function. For now I have tried to do something along of:

directory1 = gtk_file_chooser_button_new ("Choose directory 1",GTK_FILE_CHOOSER_ACTION_SELECT_FOLDER);

The same for directory2. Then put them inside struct

struct directories {
    GtkWidget *first;
    GtkWidget *second;
};

struct directories directory;
    directory.first = directory1;
    directory.second = directory2;

And after the click of a button pass it to function which currently does nothing but tries to retrieve URIs and print them.

g_signal_connect(button, "clicked", G_CALLBACK(print_test), &directory);

print_test (struct directories *dirc)
{
    g_print("%s\n", gtk_file_chooser_get_uri(GTK_FILE_CHOOSER(dirc->first)));
    g_print("%s\n", gtk_file_chooser_get_uri(GTK_FILE_CHOOSER(dirc->second)));
}

I have also tried replacing GTK_FILE_CHOOSER with GTK_FILE_CHOOSER_BUTTON but the result is the same: my program is compiled, I choose some directories and after activating the button it crashes having printed one

(null)

and the following debug info

GLib-GObject-WARNING **: 02:52:03.786: invalid uninstantiatable type 'gchararray' in cast to 'GtkFileChooserButton'
Gtk-CRITICAL **: 02:52:03.786: gtk_file_chooser_get_uri: assertion 'GTK_IS_FILE_CHOOSER (chooser)' failed

I thought that gtk_file_chooser_button was a good solution because it seemed simpler to use than to manually establish dialog but now I started to question whether I am allowed to use it that way or is the failure of my program the fault of wrong method of passing pointers to the print_test. Unfortunately all the examples I found focus on using dialogs so I did not find a good example from which I could learn how to use gtk_file_chooser_button.

EDIT: Per request I present my code sample. I only removed other types of buttons which are not a matter of this question AND performed changes described in the first comment thus you can observe minor differences in two lines compared to the question above.

#include <stdio.h>
#include <gtk/gtk.h>

struct directories {
    GtkWidget *first;
    GtkWidget *second;
};

static void
print_test (GtkWidget *somewidget, struct directories *dirc)
{
    g_print("%s\n", gtk_file_chooser_get_uri(GTK_FILE_CHOOSER(dirc->first)));
    g_print("%s\n", gtk_file_chooser_get_uri(GTK_FILE_CHOOSER(dirc->second)));
}

static void
set_expand (GtkWidget *widget)
{
    gtk_widget_set_hexpand(widget, 1);
    gtk_widget_set_vexpand(widget, 1);
}

static void
activate (GtkApplication* app,
          gpointer        user_data)
{
    GtkWidget *window;
    GtkWidget *grid;
    GtkWidget *frame;
    GtkWidget *settings;
    GtkWidget *directory1;
    GtkWidget *directory2;
    GtkWidget *button;

    //Prepare the window
    window = gtk_application_window_new (app);
    gtk_window_set_title (GTK_WINDOW (window), "Sagger");
    gtk_window_set_default_size (GTK_WINDOW (window), 400, 200);
    gtk_window_set_position(GTK_WINDOW(window),GTK_WIN_POS_CENTER);

    //Prepare the grid
    grid = gtk_grid_new();
    //gtk_grid_set_column_homogeneous(grid, 1);
    //gtk_widget_set_halign (grid, GTK_ALIGN_FILL);
    //gtk_widget_set_valign (grid, GTK_ALIGN_FILL);
    set_expand(grid);
    gtk_container_add(GTK_CONTAINER(window), grid);

    //Prepare directory chooser
    settings = gtk_box_new(GTK_ORIENTATION_VERTICAL, 0);
    frame = gtk_frame_new("Choose directories");
    set_expand(settings);
    gtk_container_add(GTK_CONTAINER(frame), settings);
    directory1 = gtk_file_chooser_button_new ("Source directory",GTK_FILE_CHOOSER_ACTION_SELECT_FOLDER);
    set_expand(directory1);
    gtk_container_add(GTK_CONTAINER(settings), directory1);
    directory2 = gtk_file_chooser_button_new ("Target directory",GTK_FILE_CHOOSER_ACTION_SELECT_FOLDER);
    set_expand(directory2);
    gtk_container_add(GTK_CONTAINER(settings), directory2);
    gtk_grid_attach(grid, frame, 0, 0, 2, 1);

    //Prepare the run button
    settings = gtk_button_box_new(GTK_ORIENTATION_HORIZONTAL);
    gtk_button_box_set_layout(GTK_BUTTON_BOX(settings), GTK_BUTTONBOX_EXPAND);
    set_expand(settings);
    gtk_grid_attach(grid, settings, 0, 2, 2, 1);
    button = gtk_button_new_with_label("RUN");

    //Try to pass the chosen directories
    struct directories directory;
    directory.first = directory1;
    directory.second = directory2;
    g_signal_connect(G_OBJECT(button), "clicked", G_CALLBACK(print_test), (gpointer) &directory);

    gtk_container_add(GTK_CONTAINER(settings), button);

    gtk_widget_show_all (window);
}

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

    app = gtk_application_new ("pl.etua.sagger", G_APPLICATION_FLAGS_NONE);
    g_signal_connect (app, "activate", G_CALLBACK (activate), NULL);
    status = g_application_run (G_APPLICATION (app), argc, argv);
    g_object_unref (app);

    return status;
}

Answer 1

directory is local to the activate() function, and, as mentioned in the comments, will get destroyed when it goes out of scope. Later on, when the print_test() function is invoked on button click, it will try to access this memory, leading to the segmentation fault.

Two easy ways out:

Make directory global:

struct directories {
    GtkWidget *first;
    GtkWidget *second;
};
struct directories directory;

Or make it static in activate():

static struct directories directory;