> But if you could make it unreachable on the sending end then there would be > no need to duplicate it, just to pass a reference to the worker, it would > take about < 1 ns.
Yes, but the sender might have gotten this value from anywhere. All other code using the value will have to know that it is going to be invalidated, or it will use it and break. This complicates APIs and leads to subtle bugs in a way comparable to C's memory management.
