[boost] Re: Re: Re: [fsm] Why exit actions must not fail

From: Andreas Huber (ah2003_at_[hidden])
Date: 2004-06-03 13:37:15

Rob Stewart wrote:
> Assume that the state machine dtor only releases resources, that
> it doesn't do any FSM things like exit actions or transitions.
> Assume that the library states clearly and emphatically that
> state object dtors may only release resources, and that they may
> not do any FSM things like exit actions or transitions.
> Then, once the state machine has been halted (akin to
> std::terminate()) for any reason, the library can disallow
> further FSM behavior or it can just state that doing any such
> things once the state machine has been halted results in
> undefined behavior.

Ok, I think I got it. I don't like the undefined behavior part but in
general I agree that once an exception has left the state machine, the state
machine is essentially no longer usable. boost::fsm currently terminates the
state machine before the exception is propagated to the client. I agree that
termination may be too much, as this inevitably exits all states but I think
it is a good idea to put the state machine into a defined state whenever an
exception is propagated. This way there's much less room for error when
someone accidentially uses such a state machine object.

Regards,

Andreas