> what happens to MSM if guard returns `false`

If the guard returns false, then the state transition and transition action do not happen. This is not an error, it's expected behaviour.

> Regarding the const events

If you want event data to be mutable, pass a reference to mutable data in the immutable event object. If the lifetime of the mutable data is nondeterministic, hold a shared_ptr to shared mutable state in the event object.





On 28 May 2017 at 08:42, Ovanes Markarian via Boost-users <boost-users@lists.boost.org> wrote:
Hi *,

I am currently reading through the MSM docs and have one question, what happens to MSM if guard returns `false`.  Does the MSM enter an error state in orthogonal region (http://www.boost.org/doc/libs/1_64_0/libs/msm/doc/HTML/ch03s02.html#d0e577)? Even internals page describes, what happens if guard returns `true`, but not a single word on `false` case.

Regarding the const events: I am programming an MSM to proxy network traffic and once a message with data was received it'll be analysed and moved between different states. Message instances implement move semantics. Currently, the MSM has an initial state `ready` where the `message_in` event is handled. This event contains the message to be analysed. From my current understanding I either have to make message field in `message_in` event mutable or MSM needs to to support r-value references. Can somebody tell me what's going to happen if the action only accepts r-value reference to an event instance? Currently, it seems to work, but would like to understand the implications.

struct some_action_impl 
{
  template<class Fsm, class Event, class SourceState, class TargetState> 
  void operator()(Event&& ev, Fsm& fsm, SourceState& source, TargetState& target)
  { ... } 
}
My last question relates to multi-threading. I understand that MSM manages internal states, would it be safe to create MSM as a thread-local storage and restart the thread-local MSM if the new request comes in? It's more about, what happens to MSM after an error state? Is calling stop(), start() members enough?

Many thanks for help,
Ovanes


_______________________________________________
Boost-users mailing list
Boost-users@lists.boost.org
https://lists.boost.org/mailman/listinfo.cgi/boost-users