[vidarh]

Message passing in the OOP sense does not imply there's no call stack. Whether or not there's a call stack is an implementation detail.

The same holds true if you actually pass async messages on a bus - nothing stops you from attaching call details to the message. In fact, we have one very prominent async messaging system that does exactly that: E-mail (via "Received:" headers). (And yes, I've used e-mail as a message bus for applications before - Qmail worked great for that)