chore(state-machine): Panic in the case of non-handled non-deferred e…

…vents

This adds a sanity check to verify that there are no non-deferred events left in
the event queue after the run_queue has been populated.

If there was, then we would have undefined behaviour in the state-machine, and
as such the best thing we can do in this instance is to panic. This is a serious
logic error in our code, and as such such cause a hard-fault.

Signed-off-by: Ole Petter <ole.orhagen@northern.tech>

src/common/state_machine.hpp

@@ -215,9 +215,27 @@ class StateMachineRunner : virtual public EventPoster<EventType> {
 		return run_queue;
 	}
 
+
+	void FailIfNonDeferredEventsLeftInEventQueue(queue<EventType> queue_copy) {
+		// Check if there are any non-deferred events in the queue - then fail if
+		while (not queue_copy.empty()) {
+			EventType event = queue_copy.front();
+			queue_copy.pop();
+			for (const auto machine : machines_) {
+				if (machine->deferred_events_.find(event) == machine->deferred_events_.end()) {
+					log::Fatal(
+						"The state machine has an unprocessed non-deferred event in the queue. This is a programming error!");
+				}
+			}
+		}
+	}
+
+
 	void RunOne() {
 		vector<State<ContextType, EventType> *> run_queue = FillRunQueueFrom(event_queue_);
 
+		FailIfNonDeferredEventsLeftInEventQueue(event_queue_);
+
 		if (!run_queue.empty()) {
 			for (auto &state : run_queue) {
 				log::Trace("Entering state " + common::BestAvailableTypeName(*state));