Unreal Crashes After Several Start/Stops when SocketIOComponent is on GameMode

[LordNed]

Hi all,

We've added the SocketIOComponent to the GameMode as we want to ensure it attempts the connection each time the GameMode is started. Unfortunately after 3 or 4 start/stop plays Unreal Engine crashes with the callstack posted below. This is fairly easy to test by rapidly starting/stopping Simulate.

This uses Unreal 4.16.1. (Windows) I have created a gist with our setup inside the GameMode which should let you replicate it. You will be missing a node for how we get our address/port but they should be easy. Add a SocketIOClient component and disable Auto-connect and then paste the gist's contents into the GameMode and hook up the connect functions to BeginPlay.

https://gist.github.com/LordNed/ace0d2492ae1e18b532536db98b41e1e

Access violation - code c0000005 (first/second chance not available)

UE4Editor_SocketIOClient!TMulticastScriptDelegate<FWeakObjectPtr>::ProcessMulticastDelegate<UObject>() [e:\program files\epic games\ue_4.16\engine\source\runtime\core\public\uobject\scriptdelegates.h:457]
UE4Editor_SocketIOClient!TGraphTask<FFunctionGraphTask>::ExecuteTask() [e:\program files\epic games\ue_4.16\engine\source\runtime\core\public\async\taskgraphinterfaces.h:884]
UE4Editor_Core!FNamedTaskThread::ProcessTasksNamedThread() [d:\build\++ue4+release-4.16+compile\sync\engine\source\runtime\core\private\async\taskgraph.cpp:954]
UE4Editor_Core!FNamedTaskThread::ProcessTasksUntilIdle() [d:\build\++ue4+release-4.16+compile\sync\engine\source\runtime\core\private\async\taskgraph.cpp:716]
UE4Editor_Engine!FFrameEndSync::Sync() [d:\build\++ue4+release-4.16+compile\sync\engine\source\runtime\engine\private\unrealengine.cpp:8502]
UE4Editor!FEngineLoop::Tick() [d:\build\++ue4+release-4.16+compile\sync\engine\source\runtime\launch\private\launchengineloop.cpp:3247]
UE4Editor!GuardedMain() [d:\build\++ue4+release-4.16+compile\sync\engine\source\runtime\launch\private\launch.cpp:166]
UE4Editor!GuardedMainWrapper() [d:\build\++ue4+release-4.16+compile\sync\engine\source\runtime\launch\private\windows\launchwindows.cpp:134]
UE4Editor!WinMain() [d:\build\++ue4+release-4.16+compile\sync\engine\source\runtime\launch\private\windows\launchwindows.cpp:210]
UE4Editor!__scrt_common_main_seh() [f:\dd\vctools\crt\vcstartup\src\startup\exe_common.inl:253]
kernel32
ntdll

[getnamo]

Interesting, I've never attached it to a game mode, this is a good description for repro. Call stack points to a nullptr reference from the taskgraph system, so likely trying to pass back information on the game thread after the world has been destroyed. Will look through this bug on the next pass.

[LordNed]

After having a gander at #47 I'm wondering if they're related. I'll change code on my end to my suggested fix I left there and see if that resolves this issue as well.

[LordNed]

Either fixing #47 or #48 seems to have resolved this issue as I can no longer get it to crash. Closing the Issue.