从sandbox内部分配给_ENV时，您不会覆盖全局环境，而是替换当前正在运行的代码的_ENV升值.将呼叫添加到print(_ENV)可能有助于您更好地了解所涉及表的身份.

When you assign to _ENV from within sandbox, you're not overwriting the global environment--you're replacing the _ENV upvalue of the currently running code. Adding calls to print(_ENV) may help you better understand the identities of the tables involved.

例如:

function print_env()
  print(_ENV)
end

function sandbox()
  print(_ENV) -- prints: "table: 0x100100610"
  -- need to keep access to a few globals:
  _ENV = { print = print, print_env = print_env, debug = debug, load = load }
  print(_ENV) -- prints: "table: 0x100105140"
  print_env() -- prints: "table: 0x100105140"
  local code1 = load('print(_ENV)')
  code1()     -- prints: "table: 0x100100610"
  debug.setupvalue(code1, 1, _ENV) -- set our modified env
  code1()     -- prints: "table: 0x100105140"
  local code2 = load('print(_ENV)', nil, nil, _ENV) -- pass 'env' arg
  code2()     -- prints: "table: 0x100105140"
end

loadin函数存在于Lua 5.2的某些预发行版本中，但在最终发行版本之前已被删除.相反，Lua 5.2 load和loadfile函数接受env参数.您还可以使用 debug.setupvalue修改另一个函数的_ENV .

The loadin function was present in some pre-release versions of Lua 5.2 but was removed before the final release. Instead, the Lua 5.2 load and loadfile functions take an env argument. You can also modify the _ENV of another function using debug.setupvalue.