I tweeted this Stack Overflow answer about getting exception backtraces
yesterday and got so much favorite/retweet love that I figured I should mention
it here, too.
In Xcode 4.2 and iOS 5, exceptions that crash your application are no longer
breaking on the line where the exception occurred. The debugger just dumps you
main() and no backtrace is printed out or navigatable on the left
side panel. Well, as this answer demonstrates, that old out-of-the-box
feature has been converted into exception breakpoints. You need to create one
yourself and then you’ll get the old useful behavior back!