test_weak_table_and_gc.lua

local a = setmetatable({}, {__mode = "kv"})
local c = nil

local b =  setmetatable({}, {
        __gc = function (self)
            print("self:", self)
            print("weak value:", a.test_value)
            c = self
        end
    })
print("b", b)

a.test_value = b
b = nil

collectgarbage("collect")

print("end:", a.test_value, "c:", c)