Re: question on how are upvalues handled

[nobody <nobody+lua-list@...>]

On 12/05/2020 01.03, Andrea wrote:
> locals are pointers to the stack (just a number because the stack frame 
> is limited)
>
> upvalues are pointers to the stack that can later become pointers to the 
> heap, does this mean that every upvalue is made of 2 pointers (using 
> twice the space) or it is made of 1 pointer with a tag that is 
> changed/update when the upvalue is moved from the stack to the heap?

If I recall correctly, that's a yes.  (The upvalue either points into 
the stack or into itself, the extra indirection remains throughout its 
lifetime.) See also section 5 (pages 8ff.) of "The Implementation of Lua 
5.0" at https://www.lua.org/doc/jucs05.pdf

-- nobody
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