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How does Nim do thread-based GC if an object is shared across threads? Does it not allow that sharing references cross-thread (not sure how it would without lifetimes though)?

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You communicate via channels, like in Go. Objects passed through a channel are deep copied. To share an object, you can create an actor thread that owns it, or if you're sure the object won't be GCed (i.e. by exempting it with the `GC_ref` function), you can pass a pointer through the channel.

If I understand the Nim manual correctly, there is no sharing of objects across threads. Instead, Nim assumes message passing. When you communicate between threads, Nim makes a deep copy of the message.

In theory, that strategy could be very inefficient if the messages are large, but it also means the garbage collector is unaware of threads and therefore simpler.

>there is no sharing of objects across threads

You can message-pass a pointer if you are sure the referenced object won't be GCed.

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