Re: GTK warning

[Stefan Kost <ensonic hora-obscura de>]

hi,

Jeffrey Barish schrieb:
> Dov Grobgeld wrote:
> > 2009/2/21 Jeffrey Barish <jeff_barish earthlink net>
> >
> > > I hate the warning messages that GTK provides because they rarely help me
> > > find the problem.  What does this one mean?
> > >
> > > /myprogram.py:118: Warning: g_object_unref: assertion `object->ref_count
> > > > 0' failed
> > >  self['myimage'].set_from_pixbuf(mypb)
> > >
> > > What object is producing the warning?  I suppose it must be myimage. 
> > > What am I supposed to do?  If I exit the program and run it again, 9
> > > times out of 10 I don't get the warning.
> > The message means exactly what it sais, that you try to reduce the ref
> > count of an object that doesn't exist.
>
> Of course.  My complaint is that the message doesn't tell me which object. 
> It refers me to a specific line in which it isn't obvious that any object
> is being unreferenced.  That line sets the pixbuf, which, if anything,
> would increase the ref count of something.  If the dereference occurs
> somewhere else, then the warning shouldn't refer me to this line of code.

How should gobject know the name of your variable? In GStreamer we have a
GstObejct which has a name property, that makes it easier.

> > But since the example you give is in Python this probably means that there
> > is an error in the python binding. You should try to create a minimum
> > example that triggers the problem and try to create a bug report.
>
> If there were an error in the Python binding, then I would expect the
> warning to be consistent.  For that matter, it should be consistent if the
> error were in my code or in GTK.
>
> I'm running my program with --g-fatal-warnings at the end of the command
> line.  I don't know whether that flag does anything in PyGTK, though.

That flag work on Glib level and makes warnings fatal to be able to get a
backtrace in gdb. For refcounts that is not always useful. Read the README in
refdb it explains types of refcount isssues and helps a bit for debug them.
Unfortunately its still not easy as you can't automatically tell which ref or
unref is wrong.

Stefan