#include <gtk/gtk.h>

static void destroy( GtkWidget *widget,
                     gpointer   data )
{
    gtk_main_quit ();
}

int main( int   argc,
          char *argv[] )
{
    GtkWidget *window;
    GtkWidget *button;

    /* This is called in all GTK applications. Arguments are parsed
     * from the command line and are returned to the application. */
    gtk_init (&argc, &argv);

    /* create a new window */
    window = gtk_window_new (GTK_WINDOW_TOPLEVEL);

    /* Here we connect the "destroy" event to a signal handler.
     * This event occurs when we call gtk_widget_destroy() on the window,
     * or if we return FALSE in the "delete_event" callback. */
    g_signal_connect (G_OBJECT (window), "destroy",
              G_CALLBACK (destroy), NULL);

    /* Sets the border width of the window. */
    gtk_container_set_border_width (GTK_CONTAINER (window), 10);

    /* Creates a new button with the label "Hello World". */
    button = gtk_button_new_with_label ("Hello World");

    /* This packs the button into the window (a gtk container). */
    gtk_container_add (GTK_CONTAINER (window), button);

    /* The final step is to display this newly created widget. */
    // ***** FOLLOWING LINE CAUSES ERROR UNLESS COMMENTED OUT ****
    gtk_widget_show (button);

    /* and the window */
    gtk_widget_show (window);

    /* All GTK applications must have a gtk_main(). Control ends here
     * and waits for an event to occur (like a key press or
     * mouse event). */
    gtk_main ();

    return 0;
}

gcc -o test -Wall -g main.c `pkg-config gtk+-2.0 --cflags --libs`