Hi Micheal,
On 27 May 2013 17:39, michael kapelko <[email protected]> wrote:
> I've stripped down my OSG app to the attached archive. Upon exit there's
> some threading error, not real crash. But when I make my mCamera
> reference-count-controlled by osg::ref_ptr my app crashes. So may be I'm
> having my threading exit hanging due to not using osg::ref_ptr.
I've just looked at your example and it really is convoluted and wrong
in a number of ways, we aren't talking OSG bugs, we are talking bugs
in your code.
1) You have an event handler that "has a" Viewer, and you attach this
event handler to the Viewer, which takes a reference, via ref_ptr<>,
to that event handler creating a
circular reference.
2) You take a C pointer to the a Camera that you assign to the viewer,
which takes a referecence, via ref_ptr<>, so the Viewer takes
ownership and will destruct it
it automatically once the Viewer gets destructed, but... you
manually call unref() and the event handler to force destruction of
the viewer's Camera. This will either
cause a dangling pointer in the Viewer or a dangling pointer in
the event handler, both of which will attempt to unref() it.
The code is crazy. We have lots of OSG example that show as sensible
way to use the OSG, none of them have an event handler owning the
viewer. Also you'll almost next see examples of code explicitly
calling unref(), it's only in very rare cases where you might want to
not use ref_ptr<> and directly call ref() and unref(), and where you
do you have to be very careful about management of the pointers
involved. I almost never write code that explicitly calls ref() and
unref(), instead ref_ptr<> is my tool, it's robust and easy to use.
I'm guessing you've resorted to using the unref() because you created
a circular reference without realizing it and tried to hack your way
out of this design/implementation error.
In you own I strongly recommend that you make the viewer the topmost
object in the chain, *always* leave the event handler as a child of
the viewer, and *never* use ref()/unref() - use ref_ptr<> instead.
Robert.
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