unexpected index -1 comes up when copy a table with only one element

[xiangnanscu]

For me, this bug happens in my company computer resty command (Intel(R) Celeron(R) J4125 8GB ram win10x64 + wsl2 ubuntu 20.04+openresty 1.21.4 install from official apt)

It should be a luajit related bug because when I turn jit off for resty, there's no bug:

for ((i=1; i<=500; i++)); do resty -joff test.lua; done

BUG machine info:

设备名称 DESKTOP-S3UK088 处理器 Intel(R) Celeron(R) J4125 CPU @ 2.00GHz 2.00 GHz 机带 RAM 8.00 GB (7.85 GB 可用)

test.lua

local function jcopy(o)
  local function copy(v)
    if type(v) == "table" then
      local cv = {}
      for key, value in pairs(v) do
        if key == -1 then
          error(tostring(key))
        end
        cv[key] = copy(value)
      end
      return cv
    else
      return v
    end
  end

  return copy(o)
end

local function main()
  local n = 0
  for i = 1, 100, 1 do
    local c = jcopy { cond = { { "you shouldn't see this via index -1" } } }
    if c.cond[-1] then
      if n == 0 then
        -- print for the first time
        print(c.cond[-1][1])
      end
      n = n + 1
    end
  end
  if n > 0 then
    print("-1 index happends:" .. n)
  end
end

main()

then run test.lua 500 times

for ((i=1; i<=500; i++)); do resty test.lua; done

you will get output like:

root@DESKTOP-S3UK088:~/rsks# for ((i=1; i<=50; i++))
> do
>   resty test.lua
> done
you shouldn't see this via index -1
-1 index happends:77
you shouldn't see this via index -1
-1 index happends:29
you shouldn't see this via index -1
-1 index happends:8
you shouldn't see this via index -1
-1 index happends:6
you shouldn't see this via index -1
-1 index happends:38

But you shouldn't see any output if the copy work as expected. this is the minimal repo: https://github.com/xiangnanscu/luajit-bug