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On Sun, 2021-09-19 at 14:28 +0200, Marc Balmer wrote:
> Are may two assumptions below correct:
> - For many objects written in C, the __close and __gc metamethods can
> be the same?

Yes, but you need to take care to ensure that closed objects being
accessible won't cause issues (which is not the case for "traditional"
__gc metamethods). This includes attempting to close object twice in a
row, among other things.

> - If a <local> variable is closed (__close called), it will not be
> called by the garbagecollector?

No, as easily demonstrated:

local a <close> = setmetatable({}, {
    __close = function() print('closed') end;
    __gc = function() print('GCd') end;
end; --> closed
collectgarbage() --> GCd
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