[gstreamer-bugs] [Bug 357432] New: [libs] GstController needs to keep controlled objects alive

[GStreamer (bugzilla.gnome.org)]

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GStreamer | gstreamer (core) | Ver: HEAD CVS

           Summary: [libs] GstController needs to keep controlled objects
                    alive
           Product: GStreamer
           Version: HEAD CVS
          Platform: Other
        OS/Version: All
            Status: UNCONFIRMED
          Severity: normal
          Priority: Normal
         Component: gstreamer (core)
        AssignedTo: gstreamer-bugs at lists.sourceforge.net
        ReportedBy: mail at renestadler.de
         QAContact: gstreamer-bugs at lists.sourceforge.net
     GNOME version: Unspecified
   GNOME milestone: Unspecified


The pointer to the controlled object that controllers store is not backed by a
reference, thus the object can be destructed without the controller being
notified.  It's clear that one would not want to create a controller for an
object and then would drop all references to the object before
uncontrolling/disposing the controller, which is why this bug has no negative
side effects in C code so far.  In bindings to higher level languages (with
garbage collectors) however, one is not necessarily in control over the exact
order in which objects as destroyed (or one does not care).  Attaching a patch
that turns this little python session

>>> import pygst; pygst.require ("0.10"); import gst, gc
>>> gst.Controller (gst.element_factory_make ("volume"), "volume")
<gst.Controller object (GstController) at 0xb76855f4>
>>> gc.collect ()
1
>>> gc.collect ()
__main__:1: Warning: instance with invalid (NULL) class pointer
__main__:1: Warning: g_signal_handler_disconnect: assertion
`G_TYPE_CHECK_INSTANCE (instance)' failed
__main__:1: Warning: g_object_set_qdata: assertion `G_IS_OBJECT (object)'
failed
1
>>> gc.collect ()
0

...into this...

>>> import pygst; pygst.require ("0.10"); import gst, gc
>>> gst.Controller (gst.element_factory_make ("volume"), "volume")
<gst.Controller object (GstController) at 0xb75d59dc>
>>> gc.collect ()
0
>>> gc.collect ()
1
>>> gc.collect ()
1
>>> gc.collect ()
0


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