Panic on 32bit ARM processor

[james7272]

The following Unaligned panic occurs on a 32 bit ARM processor

runtime/internal/atomic.panicUnaligned()
	/usr/lib/go/src/runtime/internal/atomic/unaligned.go:8 +0x24
runtime/internal/atomic.Load64(0xf482b4)
	/usr/lib/go/src/runtime/internal/atomic/atomic_arm.s:286 +0x14
github.com/qmuntal/stateless.(*StateMachine).Firing(...)
	/home/andy/Documents/werk/software/products/xte/xte_dev/vendor/github.com/qmuntal/stateless/statemachine.go:268
	

A simple workaround is to re-arrange the StateMachine struct to place the 'ops' field first where it has the correct byte alignment.

type StateMachine struct {
	ops                    uint64
	stateConfig            map[State]*stateRepresentation
	triggerConfig          map[Trigger]triggerWithParameters
	stateAccessor          func(context.Context) (State, error)
	stateMutator           func(context.Context, State) error
	unhandledTriggerAction UnhandledTriggerActionFunc
	onTransitioningEvents  onTransitionEvents
	onTransitionedEvents   onTransitionEvents
	eventQueue             *list.List
	firingMode             FiringMode
	firingMutex            sync.Mutex
}

[qmuntal]

This is unfortunate. Related to golang/go#23345.

The workaround is to move ops to the beginning of the struct, as @james7272 recommended.

I'll cut a new release with this fixed soon.

[james7272]

Thanks for the prompt fix, much appreciated.