Unreal Engine Issues and Bug Tracker (UE-41204)

Description

This is the third different callstack in an attempt to repro a HotReload crash I am experiencing.

The other two are:

[Link Removed]: Nullptr Ensure and crash after HotReloading
[Link Removed]: Assert in EditorEngine.cpp after HotReload

Steps to Reproduce

Repro:

Sync QAGame to the same CL as the latest binary build.
Open a copy of QAGame with the latest binary build
In the Content Browser, find the C++ class QAHotReloadUPROP and created a C++ derived from it named CowCPP
Right click on CowCPP and create a Blueprint class based on CowCPP and name it CowBP.
Place an instance of CowBP into the level.

Switch to Visual Studio and add the following code to CowCPP.h below the GENERATED_BODY() macro:

public:
UPROPERTY(Category = ThingsAndStuff, BlueprintReadWrite, EditAnywhere) float Stealthiness;
	
UPROPERTY(Category = ThingsAndStuff, BlueprintReadOnly) bool KingCow;

Click the compile button in UE4Editor
Open CowBP in the Blueprint subeditor and focus the Event Graph
Right click in the event graph, search for the category "things", and place the following nodes in he event graph:
1. "Get King Cow" node
2. "Get Stealthiness" node
3. "Set Stealthiness" node

In CowCPP.h, change Stealthiness to Stealth, and set it equal to 3.0f.

UPROPERTY(Category = ThingsAndStuff, BlueprintReadWrite, EditAnywhere) float Stealth = 3.0f;

Click the Compile button in the editor.

Result:
UE4Editor crashes while trying to HotReload.

Expected:
Project is able to HotReload without crashing.

Frequency:
3/3

Callstack

LogClass: Could not find existing class CowCPP in package /Script/QAGame for HotReload, assuming new class
LogClass: ETestResult HotReload.
LogClass: ETestNativeEnum HotReload.
LogClass: EPolyphonyMode HotReload.
LogClass: EWaveform HotReload.
LogClass: TestNativeStruct HotReload.
LogClass: QASkeletalMeshMergeParams HotReload.
LogClass: QASkelMeshMergeUVTransformMapping HotReload.
LogClass: QASkelMeshMergeUVTransform HotReload.
LogClass: QASkelMeshMergeSectionMapping HotReload.
LogClass: TakeHitInfo HotReload.
LogHotReload: Re-instancing CowCPP after hot-reload.
LogCrashTracker: 


LogCrashTracker: 


LogWindows:Error: === Critical error: ===
LogWindows:Error: 
LogWindows:Error: Fatal error!
LogWindows:Error: 
LogWindows:Error: Unhandled Exception: EXCEPTION_ACCESS_VIOLATION reading address 0x001a2df4
LogWindows:Error: 
LogWindows:Error: UE4Editor-UnrealEd.dll!TBaseMulticastDelegate<void,UBlueprint * __ptr64>::Broadcast() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\core\public\delegates\delegatesignatureimpl.inl:936]
LogWindows:Error: UE4Editor-UnrealEd.dll!FKismetEditorUtilities::CompileBlueprint() [d:\build\++ue4+release-4.15+compile\sync\engine\source\editor\unrealed\private\kismet2\kismet2.cpp:766]
LogWindows:Error: UE4Editor-UnrealEd.dll!FBlueprintCompileReinstancer::CompileChildren() [d:\build\++ue4+release-4.15+compile\sync\engine\source\editor\unrealed\private\kismet2\kismetreinstanceutilities.cpp:629]
LogWindows:Error: UE4Editor-UnrealEd.dll!FBlueprintCompileReinstancer::ReinstanceObjects() [d:\build\++ue4+release-4.15+compile\sync\engine\source\editor\unrealed\private\kismet2\kismetreinstanceutilities.cpp:756]
LogWindows:Error: UE4Editor-HotReload.dll!FHotReloadModule::ReinstanceClass() [d:\build\++ue4+release-4.15+compile\sync\engine\source\developer\hotreload\private\hotreload.cpp:1260]
LogWindows:Error: UE4Editor-HotReload.dll!FHotReloadModule::ReinstanceClasses() [d:\build\++ue4+release-4.15+compile\sync\engine\source\developer\hotreload\private\hotreload.cpp:1247]
LogWindows:Error: UE4Editor-HotReload.dll!TBaseRawMethodDelegateInstance<0,FHotReloadModule,void __cdecl(void)>::ExecuteIfSafe() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\core\public\delegates\delegateinstancesimpl.h:648]
LogWindows:Error: UE4Editor-CoreUObject.dll!TBaseMulticastDelegate<void>::Broadcast() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\core\public\delegates\delegatesignatureimpl.inl:937]
LogWindows:Error: UE4Editor-CoreUObject.dll!UClassReplaceHotReloadClasses() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\coreuobject\private\uobject\uobjectbase.cpp:720]
LogWindows:Error: UE4Editor-CoreUObject.dll!ProcessNewlyLoadedUObjects() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\coreuobject\private\uobject\uobjectbase.cpp:858]
LogWindows:Error: UE4Editor-CoreUObject.dll!TBaseStaticDelegateInstance<void __cdecl(void)>::ExecuteIfSafe() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\core\public\delegates\delegateinstancesimpl.h:1027]
LogWindows:Error: UE4Editor-Core.dll!TBaseMulticastDelegate<void>::Broadcast() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\core\public\delegates\delegatesignatureimpl.inl:937]
LogWindows:Error: UE4Editor-Core.dll!FModuleManager::LoadModuleWithFailureReason() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\core\private\modules\modulemanager.cpp:471]
LogWindows:Error: UE4Editor-Core.dll!FModuleManager::LoadModule() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\core\private\modules\modulemanager.cpp:330]
LogWindows:Error: UE4Editor-HotReload.dll!FHotReloadModule::DoHotReloadInternal() [d:\build\++ue4+release-4.15+compile\sync\engine\source\developer\hotreload\private\hotreload.cpp:856]
LogWindows:Error: UE4Editor-HotReload.dll!UE4Function_Private::TFunctionRefCaller<<lambda_845f9b2944b03bbc30be1e1f4a8d7f4b>,void __cdecl(TMap<FString,FString,FDefaultSetAllocator,TDefaultMapKeyFuncs<FString,FString,0> > const & __ptr64,bool,enum ECompilationResult::Type)>::Call() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\core\public\templates\function.h:245]
LogWindows:Error: UE4Editor-HotReload.dll!FHotReloadModule::CheckForFinishedModuleDLLCompile() [d:\build\++ue4+release-4.15+compile\sync\engine\source\developer\hotreload\private\hotreload.cpp:1905]
LogWindows:Error: UE4Editor-HotReload.dll!FHotReloadModule::Tick() [d:\build\++ue4+release-4.15+compile\sync\engine\source\developer\hotreload\private\hotreload.cpp:594]
LogWindows:Error: UE4Editor-UnrealEd.dll!UEditorEngine::Tick() [d:\build\++ue4+release-4.15+compile\sync\engine\source\editor\unrealed\private\editorengine.cpp:1236]
LogWindows:Error: UE4Editor-UnrealEd.dll!UUnrealEdEngine::Tick() [d:\build\++ue4+release-4.15+compile\sync\engine\source\editor\unrealed\private\unrealedengine.cpp:391]
LogWindows:Error: UE4Editor.exe!FEngineLoop::Tick() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\launch\private\launchengineloop.cpp:3025]
LogWindows:Error: UE4Editor.exe!GuardedMain() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\launch\private\launch.cpp:166]
LogWindows:Error: UE4Editor.exe!GuardedMainWrapper() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\launch\private\windows\launchwindows.cpp:134]
LogWindows:Error: UE4Editor.exe!WinMain() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\launch\private\windows\launchwindows.cpp:210]
LogWindows:Error: UE4Editor.exe!__scrt_common_main_seh() [f:\dd\vctools\crt\vcstartup\src\startup\exe_common.inl:264]
LogWindows:Error: KERNEL32.DLL!0x00000000297A8364
LogWindows:Error: ntdll.dll!0x000000002C1870D1
LogWindows:Error: ntdll.dll!0x000000002C1870D1
LogWindows:Error: 
LogExit: Executing StaticShutdownAfterError
LogWindows: FPlatformMisc::RequestExit(1)

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Cannot Reproduce

Component	UE - Foundation - Core
Affects Versions	4.15

Created	Jan 27, 2017
Resolved	Jan 30, 2017
Updated	Jul 14, 2021

UE-41204

Access Violation in delegatesignatureimpl.inl after HotReload

Access Violation in delegatesignatureimpl.inl after HotReload

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