Delegate with another delegate as a parameter = Unreal Header Generation Tool crash

Development Programming & Scripting
1

Unreal Header (Generation) Tool crashes with the following code (Unreal Engine 4.9.1 built from GitHub source)

.h

#pragma once

#include "GameFramework/Actor.h"

#include "MyActor.generated.h"


DELARE_DYNAMIC_DELEGATE_OneParam(FRegularDelegate, int32, SomeArgument);
DELARE_DYNAMIC_DELEGATE_OneParam(FDelegateWithDelegateParam, FRegularDelegate const &, RegularDelegate);


UCLASS()
class MYPROJECT_API AMyActor : public AActor
{
GENERATED_BODY()

public:
	AMyActor();

};

This is the callstack after attaching the debugger upon UHT crashing. Within UDelegateProperty::GetCPPType SignatureFunction is NULL but GetName() is called on it.

 	UnrealHeaderTool-CoreUObject.dll!UObjectBase::GetFName() Line 101	C++
 	UnrealHeaderTool-CoreUObject.dll!UObjectBaseUtility::GetName() Line 207	C++
 	UnrealHeaderTool-CoreUObject.dll!UDelegateProperty::GetCPPType(FString * ExtendedTypeText=0x000000000ed277e0, unsigned int CPPExportFlags=2) Line 77	C++
>	UnrealHeaderTool-CoreUObject.dll!UProperty::ExportCppDeclaration(FOutputDevice & Out={...}, EExportedDeclaration::Type DeclarationType=Parameter, const wchar_t * ArrayDimOverride=0x0000000000000000, unsigned int AdditionalExportCPPFlags=0, bool bSkipParameterName=false) Line 463	C++
 	UnrealHeaderTool.exe!FNativeClassHeaderGenerator::ExportNativeFunctionHeader(const FFuncInfo & FunctionData, FStringOutputDevice & HeaderOutput={...}, EExportFunctionType::Type FunctionType=Event, EExportFunctionHeaderStyle::Type FunctionHeaderStyle=Declaration, const wchar_t * ExtraParam) Line 4026	C++
 	UnrealHeaderTool.exe!FNativeClassHeaderGenerator::ExportDelegateDefinitions(FUnrealSourceFile & SourceFile={...}, const TArray<UDelegateFunction *,FDefaultAllocator> & DelegateFunctions={...}, const bool bWrapperImplementationsOnly=false) Line 3129	C++
 	UnrealHeaderTool.exe!FNativeClassHeaderGenerator::ExportClassesFromSourceFileInner(FUnrealSourceFile & SourceFile={...}) Line 1926	C++
 	UnrealHeaderTool.exe!FNativeClassHeaderGenerator::ExportClassesFromSourceFileWrapper(FUnrealSourceFile & SourceFile={...}) Line 2512	C++
 	UnrealHeaderTool.exe!FNativeClassHeaderGenerator::ExportSourceFileHeaderRecursive(FClasses & AllClasses={...}, FUnrealSourceFile * SourceFile=0x0000000006708400, TSet<FUnrealSourceFile const *,DefaultKeyFuncs<FUnrealSourceFile const *,0>,FDefaultSetAllocator> & VisitedSet={...}, bool bCheckDependenciesOnly=false) Line 2656	C++
 	UnrealHeaderTool.exe!FNativeClassHeaderGenerator::ExportSourceFileHeader(FClasses & AllClasses={...}, FUnrealSourceFile * SourceFile=0x0000000006708400) Line 1861	C++
 	UnrealHeaderTool.exe!FNativeClassHeaderGenerator::FNativeClassHeaderGenerator(UPackage * InPackage=0x000000000670dd00, const TArray<FUnrealSourceFile *,FDefaultAllocator> & SourceFiles={...}, FClasses & AllClasses={...}, bool InAllowSaveExportedHeaders, bool bInExportVTableConstructors=88) Line 4799	C++
 	UnrealHeaderTool.exe!FHeaderParser::ExportNativeHeaders(UPackage * CurrentPackage=0x000000000670dd00, FClasses & AllClasses={...}, bool bAllowSaveExportedHeaders, bool bExportVTableConstructors) Line 6586	C++
 	UnrealHeaderTool.exe!FHeaderParser::ParseAllHeadersInside(FClasses & ModuleClasses={...}, FFeedbackContext * Warn=0x000007fed03bd640, UPackage * CurrentPackage=0x000000000670dd00, const FManifestModule & Module={...}, TArray<IScriptGeneratorPluginInterface *,FDefaultAllocator> & ScriptPlugins={...}, bool bExportVTableConstructors=true) Line 6755	C++
 	UnrealHeaderTool.exe!UnrealHeaderTool_Main(const FString & ModuleInfoFilename={...}) Line 5631	C++
 	UnrealHeaderTool.exe!wmain(int ArgC, wchar_t * * ArgV=0x000000000085cd90) Line 80	C++
 	[External Code]

Any information regarding this issue is appreciated.
Link to forum thread for reference

2

I have never seen anyone do this, so i am not sure if it is supported. Why do you need to pass another delegate?

3

Even if it’s not supported, it should give error insted of crashing, so it can be count as bug

4

Hey UnrealEverything-

I have submitted a bug report about UHT crashing when attempting to declare a delegate as part of another delegate’s parameter list (UE-28643).

Cheers

5

This has now been fixed and should be in the 4.11 release. While UHT should now generate the correct code and (importantly) not crash, I can’t say how well it is supported in the rest of the engine, e.g. Blueprints.

Steve

6

Awesome thank you very much. Another reason to look forward to 4.11 :slight_smile:

In the meantime I’m wrapping FRegularDelegate in a USTRUCT and use that struct as the parameter type of FDelegateWithDelegateParam. That should also work fine with Blueprints or is that a wrong assumption?