Q:

Why would Xcode 4 not be breaking on exceptions?

Just recently Xcode 4 has stopped breaking on exceptions. Every exception causes the debugger to stop at UIApplicationMain with no stack trace.

I have a breakpoint set on objc_exception_throw (confirmed by GDB logs)
Breakpoints are turned on (confirmed by GDB and other breakpoints work fine)
LLVM GCC 4.2 is my compiler
Enable Objective-C Exceptions is turned on

Are there any reasons breakpoints may not be working? Any flags I'm missing?

A:

In Xcode 4, you add the breakpoint for exceptions via breakpoint tab in the left (hit Apple+6).  You add the new exception with the little plus in the bottom left.
See: "Run > Stop on Objective-C exception" in Xcode 4?
For more instructions.

