[Bf-python] Python bug with user counts

[Campbell Barton]

I dont think many scripts rely on it so much, but the possibility of a 
user removing an Object when the script is accessing it is still there.

This is mainly a problem for scripts that register a draw event,
These scripts should be changed to get the object (active object for 
instance) - on demand rather then storing it at launch.

Ken Hughes wrote:
> I think this might be a show-stopper bug, but before trying to fix 
> thought I should discuss here:
> 
> I chased a segfault/memcorruption problem for about three hours this 
> morning before finding the cause.  The problem is with Python objects 
> being users of Blender data (i.e., id.us).  To make a long story short, 
> when an exception happens Object_dealloc() isn't called, so any BPy 
> Objects existing at that point leave the real Blender objects with an 
> incorrect number of users.  After reloading the .blend file and running 
> the script again (or a few times, it varies) would cause a crash.
> 
> I verified this also happens with 2.42a.
> 
> The simplest solution is to get rid of the id.us manipulation.  But how 
> many script rely on this now?
> The next solution would be to correctly deallocate objects when an 
> exception is thrown.  But I don't know how to do that or if it's 
> possible.  If we go that route, does anyone know how to do it?
> 
> Ken
> 
> _______________________________________________
> Bf-python mailing list
> Bf-python at projects.blender.org
> http://projects.blender.org/mailman/listinfo/bf-python
> 


-- 
Campbell J Barton

133 Hope Street
Geelong West, Victoria 3218 Australia

URL:    http://www.metavr.com
e-mail: cbarton at metavr.com
phone: AU (03) 5229 0241