[c++-pthreads] Re: pthread_cancel and EH: let's try this again

[Peter Dimov]

Peter Dimov wrote:

> It's certainly questionable whether a cleanup handler (TSD
> destructor) that explicitly enables cancellation and calls a
> cancellation point should re-cancel itself... and if it does, whether
> it should re-invoke itself, so it might be argued that this
> clarification introduced a new problem instead of fixing the old.

Scratch that, if this:

"The cancelability state shall remain set to PTHREAD_CANCEL_DISABLE until 
the thread has terminated. The behavior is undefined if a cancellation 
cleanup handler or thread-specific data destructor routine changes the 
cancelability state to PTHREAD_CANCEL_ENABLE."

made it into the TC, it specifically prohibits the scenario I described. It 
also appears to prohibit enabling cancellation after catch(pthread_cancel_e) 
without rethrow, effectively disallowing catch without rethrow ("shall 
remain set to...").

int pthread_cancelenabled(void);

RETURN VALUE

Nonzero if the current thread's cancelability state is PTHREAD_CANCEL_ENABLE 
and the call is not made from within a cleanup handler or a TSD destructor, 
zero otherwise.

could have been much simpler.