垃圾收集器收集死对象时会做什么？

Question

请按照我的输入评论（使用Lua 5.3.2 JDoodle）：

local table = {};

local weakvalues = setmetatable(
{
    table
},
{
    -- Let weakvalues values
    -- be weak, so that they fade when dead objects are g-c.
    __mode = 'v'
});

table = _;

-- Now the previously ref. table is unreachable
-- since there are no other references, I think so...

-- Sychronously wait this loop statements
-- in order to execute a next statement (maybe the
-- garbage-collector would have collected the unreachable table above
-- while this loop executes).
for i = 1, 5e7 do end

-- Expected to log 0, but it logs 1. Is the unreachable table
-- still reachable?
print(#weakvalues);

我认为table后的表格会在weakvalues[1]与table分配后删除nil。

Answer 1

您的代码不会调用collect garbage。 试试这段代码

local t = {}
local weakvalues = setmetatable({t},{ __mode = 'v'})
t = nil
collectgarbage() collectgarbage()
print(#weakvalues);