On Tuesday, 16 October 2018 at 21:19:26 UTC, Steven Schveighoffer
wrote:
OK, so here is where I think I misunderstood your point. When
you said a lock-free queue would be unusable if it wasn't
shared, I thought you meant it would be unusable if we didn't
allow the implicit cast. But I realize now, you meant you
should be able to use a lock-free queue without it being
actually shared anywhere.
What I say to this is that it doesn't need to be usable. I
don't care to use a lock-free queue in a thread-local capacity.
I'll just use a normal queue, which is easy to implement, and
doesn't have to worry about race conditions or using atomics. A
lock free queue is a special thing, very difficult to get
right, and only really necessary if you are going to share it.
And used for performance reasons!
I think this comes up where the queue was originally shared, you
acquired a lock on the thing it is a member of, and you want to
continue using it through your exclusive reference.
