Apple changed the NSXML/CFXML implementation in Snow Leopard to use libxml. Generally a good move, but so far it appears to have caused some problems:

• The notion of -[NSXMLDocument isStandalone] changed, at least in the sample code I’m using as a reproducible case for the bugs. In 10.5 the value is NO, in 10.6 it’s YES.
• Having the XML declaration contain standalone="yes", at least in the sample code, eventually causes the libxml parser to crash. Maybe not always, but if you send the sample code an AppleScript of

  tell application "SimpleScriptingPlugin"
      beep
  end tell

  the sample app will crash. Force [myNSXMLDocument setStandalone:NO] and no more crash. Or run it under Leopard regardless of the standalone setting and no crash.

It’s taken many months of investigation and going back and forth with Apple to figure out this OS bug, mostly because due to how the problem comes up we were chasing down other avenues (was this an AppleScripting problem? Still could be, at least in part.). But for now, it seems we’ve a few issues with how NSXMLDocument generates XML, how NSXMLDocument regards being standalone (and across the OS versions), and then how libxml ungracefully handles that specification. Hopefully with my further information, Apple will be able to properly remedy all of this. Yes, it’s all properly filed with Apple, so they’re aware.

I tell you. This crash problem has been plaguing me and our users for quite a while. We’ve been able to provide the users with ways to work around things, but it’s not optimal. My hope is now with this information we can provide a better solution in our code and hope that Apple will soon fix this in the OS. Finally hitting upon this last night was quite the euphoric moment. 🙂  Granted, there may still be other things to deal with for this, and I could be premature in celebrating… but certainly it’s more info for Apple towards fixing the problem, and it’s still a hopeful step in the right direction for me and the users of my product.