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asASSERT abort on delegate early destruction after Release()

robertomurta · 2020-02-03T16:38:34

Hi, I'm having an issue trying to use delegates on script callback functions as the example in https://www.angelcode.com/angelscript/sdk/docs/manual/doc_callbacks.htmlContext: I have a C++ Class for networking, that I could mostly wrap for access in angelscript. Then I need some SetOnConnect, SetOnDisconnect, SetOnMessage functions to bind in Angelscript to call some AS class methods to handle the callbacks.Following the simplest example, passing a function, it works flawless, but when using the delegate example saving the function, object and type, after doing the cb->Release() line, the application crashes.Debugging showed that the SetOnConnectCallback(asIScriptFunction* cb) runs ok, cb->Release() decrements the reference counter, but to a value of 2, and it is not deleted.However, somepoint in “vctools\crt\vcstartup\src\rtc\stack.cpp” which is not available, the address of cb parameter vanishes. Then the garbage collector tries do collect it and fails on as_scriptfunction.cpp line 1646, as content of cb is invalid.If I comment cb->Release() line, everything seems to work, except that when destroying the object, it won't destroy C++ defined counterpart, nor run it's destructor, and every time I load the scene, memory keeps ramping up.C++ snippet Class WebsocketClient : ... { ... void SetOnConnectCallback(asIScriptFunction* cb) { // Release the previous callback, if any if (m_on_connect_callback) m_on_connect_callback->Release(); if (m_on_connect_callbackObject) ETHScriptWrapper::m_pASEngine->ReleaseScriptObject(m_on_connect_callbackObject, m_on_connect_callbackObjectType); m_on_connect_callback = 0; m_on_connect_callbackObject = 0; m_on_connect_callbackObjectType = 0; if (cb && cb->GetFuncType() == asFUNC_DELEGATE) { m_on_connect_callbackObject = cb->GetDelegateObject(); m_on_connect_callbackObjectType = cb->GetDelegateObjectType(); m_on_connect_callback = cb->GetDelegateFunction(); // Hold on to the object and method ETHScriptWrapper::m_pASEngine->AddRefScriptObject(m_on_connect_callbackObject, m_on_connect_callbackObjectType); m_on_connect_callback->AddRef(); // Release the delegate, since it won't be used anymore cb->Release(); //// That's the problematic line } else { // Store the received handle for later use m_on_connect_callback = cb; // Do not release the received script function // until it won't be used any more } } ... } Angelscript snippet: funcdef void CALLBACK(); class GameScene : Scene { private ... ... private WebsocketClient@ m_room; GameScene() { const string sceneName = "scenes/field.esc"; super(sceneName); } void PrintConnected() { print("AS >>> is connected! "); } void onCreated() { SetGravity(vector2(0.0f)); ... @m_room = WebsocketClient(); //CALLBACK @func = CALLBACK(this.PrintConnected); //m_room.SetOnConnect(@func); //m_room.SetOnConnect(CALLBACK(this.PrintConnected)); m_room.SetOnConnect(CALLBACK(PrintConnected)); if(!m_room.IsConnected()) m_room.Connect("localhost", "1201"); } ... }

AngelCode Affiliates delegates referencesmanagment scriptcallbacks

Started by robertomurta January 29, 2020 09:56 PM

12 comments, last by robertomurta 4 years, 4 months ago

robertomurta

Author

January 31, 2020 08:01 PM

Upgrading angelscript version indeed solved the problem of early destruction, and I was able to use delegate as function without the splitting method/object/type code.

We are still using the pre-2012 auto-wrappers version because of lots of legacy code.

the namespaces bug fixes and improvements led us to find and fix other bugs on our code. Which is great. Thank you. :D

Setting asEP_GENERIC_CALL_MODE to 0 was unecessary. :D

PS. I don't know if it's subject for another thread, but the original problem I was working on, is that: There is an object in C++ (WebsocketClient) wrapped on AS, eventually the class that instantiate it (GameScene) is destructed, and WebsocketClient should disconnect, as coded on it's C++ destructor. It works ok when passing a normal function, but when passing a delegate the destructor is not called (nor the object destructed, as it still connected).

WitchLord

4,838

February 01, 2020 06:59 PM

The delegate holds a hard reference to the object, so as long as the delegate is alive it will keep the object alive.

This is one of the reasons why you may want to break up the delegate. That way you can instead hold a weak reference to the object to allow it to die even if the callback still exists.

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robertomurta

Author

February 03, 2020 04:38 PM

Yes, that was what I thought I understood. Even with that I did some more tests and I was not expecting that behavior. Since I think this topic might be interesting for someone else, I'll open another thread explaining better.

https://www.gamedev.net/forums/topic/705642-odd-behavior-on-using-delegate-method-as-parameter-for-callback/

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asASSERT abort on delegate early destruction after Release()

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