When you compile code with -fobjc-exceptions, you presumably do that to somewhere execute a throw. Lets say, this is my callstack:
| abort | // glibc |
| objc_exception_throw | // libobjc |
| -[MyClass methodThrowingAnException] | // myclass.so |
| myClassMethodBouncer | // myclass.so |
| function_with_a_callback | // thirdparty.so |
| -[MyClass waitingForAnException] | // myclass.so |
| main | // main |
What has happened ? I compiled all the MyClass code with -fobjc-exceptions and even did not forget to link the resulting shared library with --eh-frame-header. So all my code and libobjc.so has PT_GNU_EH_FRAME information, which is necessary for the "modern" C++ like stack unwinding.
Still not good enough. The third party library code function_with_a_callback, was not linked with --eh-frame-header and the unwinding stops right there. No catch handler can be found and objc_exception_throw treats this as an uncaught exception.
An example for the rule, that with every increase of complexity, there is also an increase in brittleness.