[Unity-v2] Bug: Check failed: Handle not reset in first callback. See comments on |v8::WeakCallbackInfo|..

[chexiongsheng]

前置阅读 | Pre-reading

• 文档/Doc
• Issues
• FAQ

Puer的版本 | Puer Version

v2.0.0

Unity的版本 | Unity Version

all

发生在哪个平台 | Platform

All

错误信息 | Error Message

Check failed: Handle not reset in first callback. See comments on |v8::WeakCallbackInfo|..

问题重现 | Bug reproduce

脚本1

using System;
using DefaultNamespace;
using UnityEngine;
using UnityEngine.SceneManagement;

public class Scene1Script : MonoBehaviour
{
    public Vector3[] TestArray = {new (0, 0, 0), new (0, 0, 0) };

    private Action<Scene1Script> callback;

    public void gotoScene2()
    {
        SceneManager.LoadSceneAsync("Scene2");
    }
    void Start()
    {
        callback = JsEngine.Vm.Eval<Action<Scene1Script>>(@"(function(mono) {
            const len = mono.TestArray.Length;
            for (let j = 0; j < 40000; ++j) {
            for (let i = 0; i < len; ++i) {
                const vec = mono.TestArray.get_Item(i);
            }
            }
        })");
    }

    // Update is called once per frame
    void Update()
    {
        callback(this);
    }
}

脚本2

using System;
using DefaultNamespace;
using UnityEngine;
using UnityEngine.SceneManagement;

public class Scene2Script : MonoBehaviour
{
    private Action callback;

    public void goBack()
    {
        SceneManager.LoadScene("Scene1");
    }
    void Start()
    {
        callback = JsEngine.Vm.Eval<Action>(@"(function() {
            let List = puer.$generic(
            CS.System.Collections.Generic.List$1,
            CS.System.Int32 // CS.UnityEngine.Vector3
            );
            for (let i = 0; i < 10000; ++i) {
                let lst = new List();
            }
        })");
    }

    // Update is called once per frame
    void Update()
    {
        callback();
    }
}

场景1加载脚本1，场景2加载脚本2

游戏启动后加载场景1.。
一会儿后点击切场景，闪退，日志报：Check failed: Handle not reset in first callback. See comments on |v8::WeakCallbackInfo|..

CrashRepro.zip

[chexiongsheng]

原因分析：

1、脚本1将产生指针类型的，指向TestArray里头字段js对象。
2、切换场景，Scene1Script 对象被gc，TestArray也被gc，但js中1的指针类型对象还没gc。
3、脚本2会在js里new对象，该对象重用了TestArray的内存。而在CppObjectMapper.cpp的BindCppObject中认为如果PassByPointer为false（在js中new会如此），这是新分配的内存，认为肯定不会和之前的重复，因而直接覆盖了CDataCache之前指针类型对象，导致之前指针类型对象释放的时候没调用到Globa.Reset（因为之前的Globa.Reset已经被冲掉），进而触发v8的assert。

[chexiongsheng]

附上简化版的用例（仅一个脚本即可）

using UnityEngine;
using Puerts;
using System;

public class TestEvent
{
    public Vector3[] testArray = { new Vector3(0, 0, 0), new Vector3(0, 0, 0) };
}

public class Test2 : MonoBehaviour
{
    private JsEnv jsEnv;
    // Start is called before the first frame update
    void Start()
    {
        jsEnv = new JsEnv();
        jsEnv.Eval(@"
let o = new CS.TestEvent();

const len = o.testArray.Length;
let cached = [];
for (let j = 0; j < 40000; ++j) {
for(let i = 0; i < len; ++i) {
    cached.push(o.testArray.get_Item(i));
}
}
o = undefined;
let List = puer.$generic(CS.System.Collections.Generic.List$1,
    CS.System.Int32
);
");
        jsEnv.Eval("gc()");
        
        GC.Collect();
        GC.WaitForPendingFinalizers();
        //jsEnv.Dispose();
        UnityEngine.Debug.Log("-------------Start---------------");
    }

    // Update is called once per frame
    void Update()
    {
        UnityEngine.Debug.Log("--------------Update--------------");
        jsEnv.Eval(@"
cached = undefined;
for (let k = 0; k < 10000; ++k) {
    let lst = new List();
}

");
    }
}

感觉要触发也比较苛刻
1、我把Start的40000次循环去掉，就重现不了了
2、好几次Update后才可以触发