"Andreas Huber" <ah2003@[...].net>  writes:

> > That seems like a bad limitation, and for me it calls into question
> > the idea of mapping state exit to destructors.  Can you explain why
> > that's the right design?
> 
>  Yes, there's a lot of evidence that state exit actions must not fail:
> 
>  Say you have a state_machine<> subclass S and an object of that class, which
>  currently resides in state A and state B nested in A (see the picture under
>  Error handling in ratinale.html). Inside S::~S, the state machine is
>  terminated what leads to the exit actions of B and A being executed. If B's
>  exit action fails, what can you do with the resulting exception? I guess we
>  agree that you cannot propagate it out of S::~S.

You miss my point.  I know destructors must not fail.  I am suggesting
that it may have been the wrong decision to represent state exit
actions with destructors; you could've used some other protocol.

-- 
Dave Abrahams
Boost Consulting
http://www.boost-consulting.com

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