this excerpt of code
.....
	m_gst_subtitlebin = gst_bin_new("subtitle_bin");
	
	GstElement *appsink = gst_element_factory_make("appsink", "subtitle_sink");

	if (!appsink)
		eDebug("eServiceMP3::sorry, can't play: missing gst-plugin-appsink");

	GstElement *dvdsubdec = gst_element_factory_make("dvdsubdec", "vobsubtitle_decoder");
	if ( !dvdsubdec )
		eDebug("eServiceMP3::sorry, can't play: missing gst-plugin-dvdsub");

	gst_bin_add_many(GST_BIN(m_gst_subtitlebin), dvdsubdec, appsink, NULL);
	GstPad *ghostpad = gst_ghost_pad_new_no_target("ghost_sink", GST_PAD_SINK);

//! 	gst_element_add_pad (m_gst_subtitlebin, ghostpad); // with this line missing
	eDebug("gstCBsubtitleCAPS:: dvdsubdec=%p, appsink=%p, ghostpad=%p,", dvdsubdec, appsink, ghostpad);

	g_signal_connect (ghostpad, "notify::caps", G_CALLBACK (gstCBsubtitleCAPS), this);

	GstCaps* caps = gst_caps_from_string("text/plain; text/x-pango-markup; video/x-dvd-subpicture; video/x-raw-rgb");
	g_object_set (G_OBJECT (appsink), "caps", caps, NULL);
	gst_caps_unref(caps);

	g_object_set (G_OBJECT (m_gst_playbin), "text-sink", m_gst_subtitlebin, NULL);
	m_subs_to_pull_handler_id = g_signal_connect (appsink, "new-buffer", G_CALLBACK (gstCBsubtitleAvail), this);
....

leads to a crash

0:00:26.172806000  1906  0x14e7b60 INFO     GST_ELEMENT_FACTORY gstelementfactory.c:401:gst_element_factory_create: creating element "bin" named "tbin"
0:00:26.173060000  1906  0x14e7b60 INFO              GST_STATES gstelement.c:2238:gst_element_continue_state:<subtitle_sink> completed state change to READY
0:00:26.173503000  1906  0x14e7b60 INFO              GST_STATES gstelement.c:2251:gst_element_continue_state:<subtitle_sink> posting state-changed NULL to READY
0:00:26.174130000  1906  0x14e7b60 INFO              GST_STATES gstbin.c:2425:gst_bin_change_state_func:<subtitle_bin> child 'subtitle_sink' changed state to 2(READY) successfully
0:00:26.174615000  1906  0x14e7b60 INFO              GST_STATES gstelement.c:2238:gst_element_continue_state:<vobsubtitle_decoder> completed state change to READY
0:00:26.175046000  1906  0x14e7b60 INFO              GST_STATES gstelement.c:2251:gst_element_continue_state:<vobsubtitle_decoder> posting state-changed NULL to READY
0:00:26.175621000  1906  0x14e7b60 INFO              GST_STATES gstbin.c:2425:gst_bin_change_state_func:<subtitle_bin> child 'vobsubtitle_decoder' changed state to 2(READY) successfully
0:00:26.176390000  1906  0x14e7b60 INFO              GST_STATES gstelement.c:2238:gst_element_continue_state:<subtitle_bin> completed state change to READY
0:00:26.176900000  1906  0x14e7b60 INFO              GST_STATES gstelement.c:2251:gst_element_continue_state:<subtitle_bin> posting state-changed NULL to READY
0:00:26.179441000  1906  0x14e7b60 INFO                playsink gstplaysink.c:828:find_property:<subtitle_sink> found async with sink property
0:00:26.179527000  1906   0x5b4b10 DEBUG               playbin2 gstplaybin2.c:2001:gst_play_bin_update_cached_duration_from_query:<playbin> Updating cached duration from query
0:00:26.181324000  1906  0x14e7b60 INFO        GST_ELEMENT_PADS gstelement.c:970:gst_element_get_static_pad: no such pad 'sink' in element "subtitle_bin"
0:00:26.182087000  1906  0x14e7b60 WARN                playsink gstplaysink.c:1214:gen_text_chain:<playsink0> can't find a sink pad on custom text sink
PC: 2d3b4214
 00000000 10008700 2d3b0000 00000002
 00000000 2d3dc218 00000014 00000014
 00000001 00000000 2b1938f4 014cfff8
 00000000 00000048 00000001 00000001
 00000000 2d3dc218 00000014 2d3e0000
 013bf6c0 2d3dc1ec 2d3e0000 0000078b
 00000000 2af13584 00000001 00000000
 2d3fa6a0 2dfe55e8 00000000 2d3b45e0
As a final action, i will try to dump a bit of code.
I just hope that this won't crash.
2d3b4214: 00 00 84 8c 21 88 c0 00 09 f8 20 03 21 90 a0 00 28 00 bc 8f 18 00 40 14 21 98 40 00 cc 85 84 8f (end)