Forgive me for the basic question, but I'm not a gdb expert...
I'd like to have "break on NSExceptions" turned on by default... I see
the XCode Debug menu has an option for break on C++ exceptions, but no
option for Obj-C exceptions...
You can do this without touching gdb. Add "-[NSException raise]"
(without the quotes) in the breakpoints window by clicking the "New
Breakpoint" button. Sometimes when you add a new one the window
scrolls horizontally just enough to hide the checkbox column so make
sure to scroll over and check that new breakpoint is enabled.