Re: Restating the Jason model

[David Abrahams <dave@xxxxxxxxxxxxxxxxxxxx>]

Wil Evers <wil@xxxxxxxxxxxxxx> writes:

> Jason Merrill wrote:
>
>> On Tue, 13 Jan 2004 07:47:17 -0500, Dave Butenhof <David.Butenhof@xxxxxx> wrote:
>  >
>>>Cancellation should NOT be disabled in destructors? Did you mean to say
>>>that?
>> Yes.  Destructors can be run under two different situations:  1)
>> when the object goes out of scope during normal execution;  2) when
>> unwinding the stack during exception handling.
>> In #1, an exception thrown out of a destructor is propagated
>> normally.  In
>> the #2, it causes a call to terminate().  So we need to suppress
>> cancellation for #2, but not (necessarily) #1.
>
> It is true that an exception escaping from a destructor will not
> trigger immediate program termination when the program/thread in
> question is not unwinding; however, that doesn't mean there's nothing
> to worry about. The most likely symptom is a resource leak; 

Yes, but it could be arbitrarily bad.  This is really the same point
I've been making from the beginning: functions which are assumed not
to throw can't suddenly start throwing; it's just as hard to manage
that as to manage asynchronous cancellations.  Everybody expects
destructors not to throw.

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