pthread_cancel and EH: let's try this again

[Alexander Terekhov]

Jason Merrill wrote:
> 
> On Wed, 13 Jul 2005 17:28:50 +0200, Alexander Terekhov <terekhov at web.de> wrote:
> 
> > Jason Merrill wrote:
> > [...]
> >> while (true)
> >>  try
> >>   {
> >>    body();
> >>   }
> >>  catch (...)
> >>   {
> >>    recover();
> >>   }
> >>
> >> Under the old non-EH implementation this thread cancelled properly.
> >
> > You mean with omitted recovery? That's hardly "properly".
> >
> > Cancel-unaware code is not meant to be canceled.
> >
> > It's as simply as that.
> 
> A customer of ours has code along those lines in a package that uses
> pthread_cleanup_push/pop to handle cleanups on cancellation.  It works fine
> under Solaris, tru64, and older linux systems.
                 ^^^^^

Uhmm, regarding Compaq Tru64 UNIX V5.1B (Rev. 2650)...

> 
> It IS cancel-aware.  The problem is that allowing catch(...) to catch
> cancellation changes what it MEANS to be cancel-aware in an incompatible
> way.

spe147.testdrive.hp.com> cxx -pthread -o jason jason.cpp
spe147.testdrive.hp.com> ./jason
Throwing cancel exception...
C++ catch...
Throwing cancel exception...
PTHREAD_CATCH_NP(pthread_cancel_e)...
Exception: Thread has been canceled (dce / thd)
pthread_cancel_e has been raised and swallowed twice, Jason.
spe147.testdrive.hp.com> cat jason.cpp
#include <stdio.h>
#include <pthread.h>
#include <pthread_exception.h>

extern "C" void tru64_native_pthread_exception_handling() {
  pthread_cancel(pthread_self());
  PTHREAD_TRY_NP {
    printf("Throwing cancel exception...\n");
    pthread_testcancel();
  }
  PTHREAD_CATCH_NP(pthread_cancel_e) {
    printf("PTHREAD_CATCH_NP(pthread_cancel_e)...\n");
    pthread_exc_report_np(PTHREAD_THIS_CATCH_NP);
  }
  PTHREAD_ENDTRY_NP
}

int main() {
  pthread_cancel(pthread_self());
  try {
    printf("Throwing cancel exception...\n");
    pthread_testcancel();
  }
  catch(...) {
    int state;
    printf("C++ catch...\n");
    pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, &state);
    tru64_native_pthread_exception_handling();
  }
  printf("pthread_cancel_e has been raised and swallowed twice, Jason.\n");
}
spe147.testdrive.hp.com>

regards,
alexander.