Gtk 2.8.19 GLIB 2.10.3 GCC 4.1.1 
xfdesktop revision 22820

CFLAGS="-march=prescott -O0 -g"

#0  0x080befbb in ?? ()
#1  0xb7e7862e in xfce_rc_close () from /usr/lib/libxfce4util.so.4
#2  0xb7e79780 in xfce_rc_write_list_entry () from
/usr/lib/libxfce4util.so.4
#3  0xb7e7862e in xfce_rc_close () from /usr/lib/libxfce4util.so.4
#4  0xb752b9f1 in desktop_menu_cache_is_valid ()
   from /usr/lib/xfce4/modules/xfce4_desktop_menu.so
#5  0xb752a564 in ?? () from /usr/lib/xfce4/modules/xfce4_desktop_menu.so
#6  0x080b9500 in ?? ()
#7  0x080820e0 in ?? ()
#8  0x08082100 in ?? ()
#9  0x080b7434 in ?? ()
#10 0xb7762ff4 in ?? () from /lib/tls/libc.so.6
#11 0xb7764840 in __malloc_initialize_hook () from /lib/tls/libc.so.6
#12 0x080a9ad0 in ?? ()
#13 0xbfeb9548 in ?? ()
#14 0x00000001 in ?? ()
#15 0x00000000 in ?? ()

CFLAGS="-march=prescott -O2 -pipe"

#0  0x080b8fb1 in ?? ()
#1  0x080b8fb0 in ?? ()
#2  0xb7eb362e in xfce_rc_close () from /usr/lib/libxfce4util.so.4
#3  0xb7eb4780 in xfce_rc_write_list_entry () from
/usr/lib/libxfce4util.so.4
#4  0xb7eb362e in xfce_rc_close () from /usr/lib/libxfce4util.so.4
#5  0xb7567c6c in desktop_menu_cache_is_valid ()
   from /usr/lib/xfce4/modules/xfce4_desktop_menu.so
#6  0xb7566d30 in xfce_desktop_menu_destroy_impl ()
   from /usr/lib/xfce4/modules/xfce4_desktop_menu.so
#7  0xb7566f18 in xfce_desktop_menu_new_impl ()
   from /usr/lib/xfce4/modules/xfce4_desktop_menu.so
#8  0xb77c51de in g_list_remove_link () from /usr/lib/libglib-2.0.so.0
#9  0xb77c699e in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#10 0xb77c9a79 in g_main_context_check () from /usr/lib/libglib-2.0.so.0
#11 0xb77c9dae in g_main_loop_run () from /usr/lib/libglib-2.0.so.0
#12 0xb7cf346d in gtk_main () from /usr/lib/libgtk-x11-2.0.so.0
#13 0x08055191 in main ()


It's odd that not using debugging
flags generated less ?? in the backtrace. When built with debugging
xfdesktop died with a segmentation fault. When built without debugging,
it died with an illegal instruction.