"Andreas Huber" <ah2003@gmx.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