Still happening in F23.

(gdb) bt
#0  0xb72f30b4 in _g_log_abort (breakpoint=1) at gmessages.c:324
#1  g_logv (log_domain=log_domain@entry=0xb7422624 "GLib-GObject", log_level=log_level@entry=G_LOG_LEVEL_ERROR, 
    format=format@entry=0xb7428d48 "cannot create instance of abstract (non-instantiatable) type '%s'", 
    args=args@entry=0xbf98aacc "L\027\020\200\200\247\032\267\200\247\032\267\300\345ցO\204\005\267") at gmessages.c:1081
#2  0xb72f3194 in g_log (log_domain=log_domain@entry=0xb7422624 "GLib-GObject", log_level=log_level@entry=G_LOG_LEVEL_ERROR, 
    format=format@entry=0xb7428d48 "cannot create instance of abstract (non-instantiatable) type '%s'") at gmessages.c:1119
#3  0xb7418a15 in g_type_create_instance (type=type@entry=2178350640) at gtype.c:1816
#4  0xb73f81a0 in g_object_constructor (type=2178350640, n_construct_properties=13, construct_params=0x81d6f448) at gobject.c:2064
#5  0x800c3da6 in gdm_display_constructor (type=2178350640, n_construct_properties=13, construct_properties=0x81d6f448) at gdm-display.c:1110
#6  0xb73f8545 in g_object_new_with_custom_constructor (n_params=6, params=0xbf98ae9c, class=0x81d72468) at gobject.c:1697
#7  g_object_new_internal (class=class@entry=0x81d72468, params=params@entry=0xbf98ae9c, n_params=n_params@entry=6) at gobject.c:1777
#8  0xb73faaa3 in g_object_new_valist (object_type=object_type@entry=2178350640, first_property_name=first_property_name@entry=0x800faf38 "remote-hostname", 
    var_args=0xbf98af98 "x\213Ձ", var_args@entry=0xbf98af68 "\230'ׁ\256\255\017\200\001") at gobject.c:2038
#9  0xb73fab20 in g_object_new (object_type=2178350640, first_property_name=first_property_name@entry=0x800faf38 "remote-hostname") at gobject.c:1622
#10 0x800df348 in gdm_xdmcp_display_new (hostname=hostname@entry=0x81d72798 "127.0.0.1", number=number@entry=1, address=address@entry=0x81d6e4c8, 
    session_number=1759478523) at gdm-xdmcp-display.c:276
#11 0x800dcfe9 in gdm_xdmcp_display_create (displaynum=<optimized out>, address=<optimized out>, hostname=<optimized out>, factory=<optimized out>)
    at gdm-xdmcp-display-factory.c:2149
#12 gdm_xdmcp_handle_request (len=<optimized out>, address=0x81d6e4c8, factory=0x81d2d190) at gdm-xdmcp-display-factory.c:2390
#13 decode_packet (source=0x81d45ea0, cond=G_IO_IN, factory=factory@entry=0x81d2d190) at gdm-xdmcp-display-factory.c:2995
#14 0xb7336f16 in g_io_unix_dispatch (source=source@entry=0x81d45ee8, callback=0x800db320 <decode_packet>, user_data=0x81d2d190) at giounix.c:165
#15 0xb72ec0c3 in g_main_dispatch (context=0x81d2ce00) at gmain.c:3154
#16 g_main_context_dispatch (context=context@entry=0x81d2ce00) at gmain.c:3769
#17 0xb72ec4a5 in g_main_context_iterate (context=0x81d2ce00, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at gmain.c:3840
#18 0xb72ec831 in g_main_loop_run (loop=0x81d338e0) at gmain.c:4034
#19 0x800be7cb in main (argc=1, argv=0xbf98b404) at main.c:404

I see this is https://bugzilla.gnome.org/show_bug.cgi?id=757714 upstream - would it be possible to bring this one-line patch into F23?

should be possible, but I'm not convinced xdmcp is functional, yet.  I need to do some testing.

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