Xcode debug with iPhone app is slow and laggy

Question

I am debugging an iPhone app I'm writing in Xcode, but sometimes now the debugger (which is GDB) slows a lot (doing a step-by-step debugging) and becomes unresponsive sometimes (the icons for stepping-in, stepping-over, stepping-out are not clickable), after sometimes it gets back to normal and continues and other times it stay like that forever or a message appears in console: "Timed out" (or something similar) and I can see my CPU from activity monitor going up to 90%. As a workaround I used to put a brekpoint after the line of code I was interested in and simply went with 'Continue' to 'Continue' (doing so it run perfectly fine and fast). Can this be code dependent? Is there a way I can debug the debugger (behaviour) ?

UPDATE: The complete message is

Timed out fetching data. Variable display may be inaccurate.

Googling for it i discovered that it happens when Xcode gdb is trying to look inside data formatters. Someone suggested to disable Run>Variable View>Use Data Formatter (in xcode 3.2, previous i guess it is Debug->Variables View->Enable Data Formatters) and it seems to work for me too (till now) So now I am asking: why? : D

UPDATE2: This solved the debugger from stopping on a specific part of the code but it stil hangs (with the same message) in another calling. It seems to me that this involves some CoreData API like (NSEntityDescription*)entityForName: inManagedObjectContext:

UPDATE3: Would it be best to cache the NSEntityDescription instead of creating always a new one?

Answer 1

I have observed very slow debugging when 'Queue Debugging' is enabled in the scheme. If you don't need queue debugging, consider disabling it.