casting MPlugArray into a list don't hold the MPlugs in memory?

[Rudi Hammad]

hello,

I though about sharing someting strange that occured to me. I had a method that contained

MPlug.destinations() which as an art requieres an MPlugArray(). For some reason, probably because I was in a hurry and I didn't thought about it, I casted all the MPlugs from MPlug.destinations() into a python list. Let's call it foo=list().

And that's where I started getting crashes. For instance, if I did something like

foo[0], which is supposed to hold an MPlug, maya return the MPlug okey, but if I did foo[0].isNull() it returned True and then crashed.

Whereas if you don't use a python list,  and query directly the MPlugArray  (e.g, myMPlugArr[0].isNull) it returns False and everything is ok.

So my question more out curiosity than anything else. I know python lists are mutable objects, but not sure how or if that could be related.

Cheers,

R

[Justin Israel]

If foo[0] gives you an object, but foo[0].isNull() crashes, then it could be a bug in the C++ wrapper and how it reference counts. Does it crash if you first save the object in a variable? 

    p = foo[0]

    p.isNull()

I think either way it may be a bug in the wrappers around the C++ memory and the reference counting. 

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[Rudi Hammad]

yes, it does crash if you save the object in the variable. But it depends on how many times you run p.isNull(). I executed that in maya's script editor around 6 or 7 times without crash.

But it crashed at the 8th time or so. What I find strange is that the list actually holds the MPlugs, but they become null. Maybe that's why they did the MPlugArray for MPlug.destinations()??

Anyways, after almost getting a nervious break down I realised that it was coming from there XD. I just spent around 3 hours trying to figure it out. Also I tried to read the MayaCrashLog.log file

and it was like reading Klingon. No idea how to underst what it says.