pthread_cancel and EH: let's try this again

[Alexander Terekhov]

Peter Dimov wrote:
[...]
> Keeping the cancellation request active doesn't need to be done by
> reasserting in the destructor. It can simply be left active. Since
> cancellation is implicitly disabled during stack unwinding, 

No. Intelligent cancel delivery aside for a moment, it's explicitly
disabled only after delivery (and pthread_exit()). Consider:

  some_dtor() throw() {
    if (active_exception<thread_cancel_request>(0)) {
      pthread_cancel(pthread_self());
      pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, &errno);
      try {
        fclose(temp_dataset); // no need to flush 
      }
      catch(...) { }
    }
    else {
      try {
        fclose(temp_dataset); // no need to flush if we hit cancel
      }
      catch(...) { // canceled
        pthread_cancel(pthread_self());
      }
    }
  }

regards,
alexander.