forced3.c

this is a gcc file, you can download it and learn its usetility, for further detail please look at t

// { dg-do run }

// Test that forced unwinding calls std::unexpected going 
// throw a nothrow function.

#include <unwind.h>
#include <stdlib.h>
#include <exception>

static _Unwind_Reason_Code
force_unwind_stop (int version, _Unwind_Action actions,
                   _Unwind_Exception_Class exc_class,
                   struct _Unwind_Exception *exc_obj,
                   struct _Unwind_Context *context,
                   void *stop_parameter)
{
  if (actions & _UA_END_OF_STACK)
    abort ();
  return _URC_NO_REASON;
}

static void __attribute__((noreturn))
force_unwind ()
{
  _Unwind_Exception *exc = new _Unwind_Exception;
  exc->exception_class = 0;
  exc->exception_cleanup = 0;

#ifndef __USING_SJLJ_EXCEPTIONS__
  _Unwind_ForcedUnwind (exc, force_unwind_stop, 0);
#else
  _Unwind_SjLj_ForcedUnwind (exc, force_unwind_stop, 0);
#endif

  abort ();
}

static void
handle_unexpected ()
{
  exit (0);
}

static void
doit () throw()
{
  force_unwind ();
}

int main()
{ 
  std::set_unexpected (handle_unexpected);
  doit ();
  abort ();
}