to-be-closed variables as resources from a library.

[Jorge Visca <xxopxe@...>]

I'm trying to understand to-be-closed variables and got a bit stumped.

Let's suppose I am writing a library that produces an object that locks 
some resource I want released when the object can not be used anymore.

---------------------------------------------------------------------------------

-- library
local M = {
    get_object = function ()
        local obj = setmetatable( {resource=acquire_resource() },
                {__close=function (self) 
release_resource(self.resource) end }  )
        return obj
    end
}

-- user
do
    local obj <close> = M.get_object()
    -- do stuff with obj
end
-- obj does not exist anymore and was closed

---------------------------------------------------------------------------------

My intention was to spare the library's user from having to release 
resources, just get a variable and use it. But now if the user forgets 
to tag the variable as <close> when using my library then my __closes 
are useless!

Is there a way for releasing library resources transparently for the 
user (that works better than __gc)?

(I SO wanted using the <close> inside the library's method to work, it 
just made sense to me. OR just skip the <close> altogether, and if 
there's a __toclose use it when getting unreferenced).


Jorge