g++ -fno-exceptions -fno-asynchronous-unwind-tables -S a.cc => no .cfi_* directive g++ -fno-exceptions -fno-asynchronous-unwind-tables -g -S a.cc => there are .cfi_* directive C++ exceptions passing through -fno-exceptions frames have undefined behaviors. Without .eh_frame, the traditional behavior is std::terminate() as a result of _Unwind_RaiseException returning _URC_END_OF_STACK. So -fno-asynchronous-unwind-tables is a good way to detect C++ exceptions passing through -fno-exceptions frames. -g (imagine a build which always turns on debug information) forcing .cfi_* defeats such usage. (I can understand that if .debug_frame is used (rare), -g always forces .cfi_*)
