RE: Issues with the garbage collector

["Jerome Vuarand" <jerome.vuarand@...>]

Wesley Smith wrote:
> As a quick follow up just to be more precise, what's the 
> difference between this:
> --------------script global scope
> function cb(event)
>    print(event)
> end
> 
> myvar = 1
> local myvar2 = 1
> --------------end script
> 
> I load this script with a loadstring and pcall and everything is fine.
>  Now, I have in C a callback mechanism that does a getglobal 
> on cb and passes in some args.  In the process, I create a 
> table, so eventually the GC gets called.  When that happens, 
> myvar2 will disappear and obviously myvar won't.  It was my 
> (apparently wrong) understanding that local values at global 
> scope would persist at the global level.
> However, this isn't the case.  Where do they exist and to 
> what extent do they exist?

A script is a chunk, and its like any anonymous function. A global
environment is en entry in the function/chunk/script environment table.
A local variable only exist during the execution of the
function/chunk/script. So local variables are collectable as soon as the
function/chunk/script has been executed, whereas global variables are
collectable only when the environment table is collected. If the
environment table is the global one (_G), which is the default, then
they are not collectable before you close the Lua interpreter.