我试图重现GTK教程的“example-4.c”在这里描述：https://docs.gtk.org/gtk4/getting_started.html
一个简单的例子，使用XML描述的UI +一些c代码。而不是使用GTK 4，我使用GTK 3，所以，编译：

gcc `pkg-config --libs --cflags gtk+-3.0` exemple4.c -o hello `pkg-config --libs gtk+-3.0`

example4.c和builder.ui（类似xml的文件）都在同一个文件夹中。

主窗口弹出但为空，我得到以下错误（两次）：

(hello:19840): GLib-GObject-WARNING **: 19:38:31.985: invalid (NULL) pointer instance

(hello:19840): GLib-GObject-CRITICAL **: 19:38:31.985: g_signal_connect_data: assertion 'G_TYPE_CHECK_INSTANCE (instance)' failed

(hello:19840): GLib-GObject-WARNING **: 19:38:31.985: invalid (NULL) pointer instance

(hello:19840): GLib-GObject-CRITICAL **: 19:38:31.985: g_signal_connect_data: assertion 'G_TYPE_CHECK_INSTANCE (instance)' failed

我猜这是简单的东西有关的两个按钮，但我错过了为什么。
下面是后两个文件的内容：example4.c：

#include <gtk-3.0/gtk/gtk.h>
#include <glib/gstdio.h>

static void
print_hello (GtkWidget *widget,
             gpointer   data)
{
  g_print ("Hello World\n");
}

static void
quit_cb (GtkWindow *window)
{
  gtk_window_close (window);
}

static void
activate (GtkApplication *app,
          gpointer        user_data)
{
  /* Construct a GtkBuilder instance and load our UI description */
  GtkBuilder *builder = gtk_builder_new ();
  gtk_builder_add_from_file (builder, "builder.ui", NULL);

  /* Connect signal handlers to the constructed widgets. */
  GObject *window = gtk_builder_get_object (builder, "window");
  gtk_window_set_application (GTK_WINDOW (window), app);

  GObject *button = gtk_builder_get_object (builder, "button1");
  g_signal_connect (button, "clicked", G_CALLBACK (print_hello), NULL);

  button = gtk_builder_get_object (builder, "button2");
  g_signal_connect (button, "clicked", G_CALLBACK (print_hello), NULL);

  button = gtk_builder_get_object (builder, "quit");
  g_signal_connect_swapped (button, "clicked", G_CALLBACK (quit_cb), window);

  gtk_widget_show (GTK_WIDGET (window));

  /* We do not need the builder any more */
  g_object_unref (builder);
}

int
main (int   argc,
      char *argv[])
{
#ifdef GTK_SRCDIR
  g_chdir (GTK_SRCDIR);
#endif

  GtkApplication *app = gtk_application_new ("org.gtk.example", G_APPLICATION_FLAGS_NONE);
  g_signal_connect (app, "activate", G_CALLBACK (activate), NULL);

  int status = g_application_run (G_APPLICATION (app), argc, argv);
  g_object_unref (app);

  return status;
}

和builder.ui文件：

<?xml version="1.0" encoding="UTF-8"?>
<interface>
  <object id="window" class="GtkWindow">
    <property name="title">Grid</property>
    <child>
      <object id="grid" class="GtkGrid">
        <child>
          <object id="button1" class="GtkButton">
            <property name="label">Button 1</property>
            <layout>
              <property name="column">0</property>
              <property name="row">0</property>
            </layout>
          </object>
        </child>
        <child>
          <object id="button2" class="GtkButton">
            <property name="label">Button 2</property>
            <layout>
              <property name="column">1</property>
              <property name="row">0</property>
            </layout>
          </object>
        </child>
        <child>
          <object id="quit" class="GtkButton">
            <property name="label">Quit</property>
            <layout>
              <property name="column">0</property>
              <property name="row">1</property>
              <property name="column-span">2</property>
            </layout>
          </object>
        </child>
      </object>
    </child>
  </object>
</interface>