[c++-pthreads] Re: FW: RE: Re: I'm Lost

[David Abrahams]

Jason Merrill <jason at redhat.com> writes:

>> As far as I remember, Ulrich is the only person who has really argued
>> that it is unambiguously wrong to consider the situation in which a
>> thread catches a cancellation exception.
>
> I don't think he's opposed to catching it, just to doing anything that 
> would involve backing out of the cancellation once it's started.

The inability to do that would prevent several systems that Dave
B. and I have cited from working properly.  These systems, if allowed
to "back out" from a language/library point-of-view, will unwind
completely and terminate the thread as though there was no logical
"backing out," but otherwise will exhibit undefined behavior.  So I
don't think preventing "backing out" at any level that can be enforced
by the language or library is tenable if you actually want
cancellation to be able to cancel threads.

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com