G# destroy method and garbage collector both crash labview (2011) after second run

[Saint_Anger]

I have a series of G# objects which draw shapes on a 2d picture. But i have noticed that garbage collector was crashing labview altogether. at first i thought i was changing the references but they are the same

i tracked down the error and noticed if i disable the method reading the attributes of object about to be destroyed, in the destroy method, it works fine. Any suggestions?

[Mattias_Ericsson]

Hi,

This a really annoying problem. If you use the garbage collector,you actually don't have much control of the order of destruction. It will try to destroy objects in the correct order, not destroying object that other objects still have references to it, but it is hard to get this perfect. It can't sense other than G# objects etc. I don't think it actually is the garbage collector itself that causes the crash, but most likely something that happens in the destructor code that is being called. I would try to kill the objects using the ordinary destroy method before running the garbage collector. This way you can control the order of destruction and make a more graceful closing of you system. Does you get an error or does entire LabVIEW crash and "vanishes"? What LabVIEW version are you using and is it somekind of reference you are trying to read when you get the crash?

Thanks,

Mattias

[Saint_Anger]

using labview 2011

labview vanishes completely without throwing any errors

it is actually not the garbage collector itself but it is the destroy method of the object causing the crash

because if i disable the "protected" getclassattributes.vi inside the destroy method both destroy.vi and garbage collector works fine.

but i must say getclassattributes.vi also works fine within lets say get name vi of that class

in addition to that i don't think it has anything to do with the order of destruction cause there is only one object in the main vi at the moment

[Mattias_Ericsson]

Hi,

Ah, you did write LV2011 in the title, sorry missed that. Really strange behaviour, I've never heard of any crash problems with the garbage collector. It must be something with LabVIEW and puting a 2D picture in a DVR.

Alright,you are using the class attributes. This is the way class attributes and garbage collector works. When executing the garbage collector, all Destroy methods are executed killing all the objects. However, the garbage collector has one more important feature, it will kill also kill the class attributes DVR reference and class queue (the class attributes uses a one element queue that holds the DVR reference in order to take advance of the "lookup existing" using a named queue) and also one common queue used by G# to keep track of all classes existing. This is what is happening in the last step in garbage collector calling the "Clear" method.I would like you to test the following:

1) In the garbage collector, put a breakpoint just before it enters the "Clear" method. Does the crash appear in the "Clear" before it reaches the "Clear" or does it crash inside "Clear" when the class attributes internal DVR reference is actually destroyed as the last step.

Would it be possible for you to post an isolated piece of code that causes the crash? Or perhaps mail me? I would very much try to repeat your crash and report (if possible) to NI for investigastion. G# is just pure LabVIEW code and should never crash. It could be something special in the combination Queue->DVR->2D picture that might be a LabVIEW bug.

Thanks,

Mattias

[Saint_Anger]

Strange thing about this problem is after isolating the code from my main project, now i can not reproduce the problem. But still sending the isolated code to you for your observations. thank you.

[Mattias_Ericsson]

Thanks,

I will have a look at it. Maybe a plain old  recompile of the code did the work!

Thanks,

Mattias