[LAD] opinions wanted on a couple of architecture questions

As I slowly figure out audio architecture, I've gotten to here: main() - sets up jack, instantiates and Engine class and a Controller class Engine - the engine is passed to the jack audio callback, and has a .tick() to calculate audio - engine will receive messages over ToEngineQueue ( with a ringbuffer ) - engine will send messages back to controller over a second queue, ToControllerQueue Controller - started in main thread - will handle all input and output and instantiate any guis - sends messages to engine over queue - receives messages from engine over the ToControllerQueue Message - struct for passing messages, holds simple numbers, keeping individual messages of known size for now I've seen a few ways now in tutorials of handling some things and would love opinions. - Should the ToEnqineQueue be a part of Engine? ie, do we pass messages to engine with engine->newMessage( msg ); - or should the queue's be instantiated in main and should Engine and Controller each get pointers to the queues? - I think the stk examples do the former and SuperCollider the second - is it a bad idea to have both engine and controller need pointers to each other? - is this an example of an undesired circular dependency? - is avoiding that by having them each only depend on Queue and Message a good plan? - or should I avoid it by using an ABC for MessageReceivingComponent and allow them each to have pointers of type MessageReceivingComponent? - how should one handle memory management of the messages? Is it ok for Engine to allocate memory for new messages and have them destroyed on receipt, - or should I have queue delete the memory and return by value when messages are fetched? - what is the crustimony proceedcake for allocated memory from an engine? thanks to anyone who feels like they have the time to answer these! iain