为什么一个人工作和一个崩溃？ [英] Why does one work and one crash?

问题描述

这已经驱使我坚持了一个多星期。以下是游戏中的机器人播放器的两个Lua代码片段 Bitfighter （使用C ++编写，使用LuaWrapper的变体绑定）。

This has been driving me nuts for over a week. Below are two snippets of Lua code from a robot player in the game Bitfighter (written in C++, using a variant of LuaWrapper for binding).

当我第一次启动Lua脚本时，两者的工作方式完全相同。但是经过几分钟的强烈的对象创建和破坏，变体2停止工作，并给我以下错误：

When I first start the Lua script, both work exactly as expected. But after some minutes of intense object creation and destruction, variant 2 stops working, and gives me the following error:

robot.lua:253: attempt to call missing or unknown method 'getEnergy' (a nil value)

这些应该功能相同。谁能解释这些差异？

To my eyes these should function identically. Who can explain the difference?

注意：target是一个表示C ++对象的（重）userdata。 getEnergy和getHealth是正确注册的C ++函数。我可以很容易地再现这种不同的行为。这是Lua 5.1，使用luavec mod。

Notes: target is a (heavy) userdata representing a C++ object. getEnergy and getHealth are properly registered C++ functions. I can reproduce this differing behavior easily. This is Lua 5.1, using the luavec mod.

变体1 - 总是工作

Variant 1 - always works

local mt = getmetatable(target)
local pow = mt.getEnergy(target) + mt.getHealth(target)

变体2 - 在脚本运行任意时间后启动失败

Variant 2 - starts failing after script has been running for an arbitrary amount of time

 local pow = target:getEnergy() + target:getHealth()

推荐答案

要跟踪停止工作时会发生什么，您可以在 pcall 中打包调用，并查看目标 value：

To track what happens when it stops working you can wrap the call in pcall and explore what happened with the target value:

local ok, res = pcall(function() return target:getEnergy() + target:getHealth() end)
if not ok then
  local s = "Invalid target value: "..tostring(target).." "..type(target).."\n"
  for k, v in pairs(target) do s = s.."target "..tostring(k).." "..tostring(v).."\n" end
  for k, v in pairs(getmetatable(target)) do s = s.."meta "..tostring(k).." "..tostring(v).."\n" end
  -- add anything else that helps you figure out what happened to target
  error(res..s)
end
local pow = res

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