[gstreamer-bugs] [Bug 506643] New: crash in fixate_value/gst_value_init_and_copy on empty list GValues

[GStreamer (bugzilla.gnome.org)]

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  GStreamer | gstreamer (core) | Ver: 0.10.16
           Summary: crash in fixate_value/gst_value_init_and_copy on empty
                    list GValues
           Product: GStreamer
           Version: 0.10.16
          Platform: Other
        OS/Version: Linux
            Status: UNCONFIRMED
          Severity: critical
          Priority: Normal
         Component: gstreamer (core)
        AssignedTo: gstreamer-bugs at lists.sourceforge.net
        ReportedBy: qq at kuku.eu.org
         QAContact: gstreamer-bugs at lists.sourceforge.net
                CC: qq at kuku.eu.org
     GNOME version: Unspecified
   GNOME milestone: Unspecified


GStreamer fails an assertion and then crashes on the following pipeline:
v4l2src ! fakesink

A relevant fragment of the stack-trace (gstreamer 0.10.16) :
#0  gst_value_init_and_copy (dest=0x7fffd7cc3b90, src=0x0) at gstvalue.c:3216
#1  0x00002ae1d2f4c2e5 in fixate_value (dest=0x7fffd7cc3bf0, src=0x5ba328) at
gstpad.c:2113
#2  0x00002ae1d2f4c36b in gst_pad_default_fixate (field_id=489, value=0x0,
data=0x0) at gstpad.c:2151
#3  0x00002ae1d2f5f7b0 in gst_structure_foreach (structure=0x5bb770,
func=0x2ae1d2f4c330 <gst_pad_default_fixate>, 
    user_data=0x5bb770) at gststructure.c:914
#4  0x00002ae1d2f4fa0d in gst_pad_fixate_caps (pad=<value optimized out>,
caps=0x54de00) at gstpad.c:2188

And the assertion: gst_value_list_get_value: assertion `index <
gst_value_list_get_size (value)'.

When fixate_value finds a list, it attempts to read its first element, which
doesn't exist. This triggers the assertion failed. Then the NULL value is
passed to gst_value_init_and_copy, which crashes gstreamer. It's quite possible
that the empty list itself is a sign of a problem with the v4l2src, but
gstreamer should survive such problems. Unfortunately I don't really understand
what fixate_value is supposed to do, so I can't fix it myself.
The last line of the debug output confirms that an empty list triggers the bug: 
gstv4l2src.c:384:gst_v4l2src_fixate:<v4l2src0> fixating caps video/x-raw-yuv,
format=(fourcc)UYVY, width=(int)640, height=(int)480, framerate=(int){  }

This seems related to the 505799 bug, although I'm not sure if it's the same
problem.


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