ActionRPG crash with multiple child of parent NPC pawn

CTENoLonger · August 19, 2020, 6:22am

I’m using the Action RPG demo as a base for my own project and I began by spawning several enemy NPC’s of the same class and this worked as expected. Each could take damage and had the attributes I set for them in their Passive Gameplay Effect variable. However when I made a second child of that NPC base class the game crashes if any of it’s attributes are accessed or if I attempt to modify them. They will spawn in but if I use any of the Get Attribute functions that target the RPGCharacter Base in their graph or if any effects attempt to change one of their base attributes - like taking damage - the editor crashes. Here is my crash log for reference. Any help is appreciated!

P.S.- the move speed attribute is mentioned first in this log because I use the Get Move Speed function when the pawn is spawned.

Unhandled Exception: EXCEPTION_ACCESS_VIOLATION reading address 0x000000a4

UE4Editor_GameplayAbilities
UE4Editor_ActionRPG!ARPGCharacterBase::HandleMoveSpeedChanged() [F:\depot\Project\Source\ActionRPG\Private\RPGCharacterBase.cpp:408]
UE4Editor_ActionRPG!URPGAttributeSet::PostGameplayEffectExecute() [F:\depot\Project\Source\ActionRPG\Private\Abilities\RPGAttributeSet.cpp:215]
UE4Editor_GameplayAbilities
UE4Editor_GameplayAbilities
UE4Editor_GameplayAbilities
UE4Editor_GameplayAbilities
UE4Editor_GameplayAbilities
UE4Editor_ActionRPG!ARPGCharacterBase::AddStartupGameplayAbilities() [F:\depot\Project\Source\ActionRPG\Private\RPGCharacterBase.cpp:47]
UE4Editor_ActionRPG!ARPGCharacterBase::PossessedBy() [F:\depot\Project\Source\ActionRPG\Private\RPGCharacterBase.cpp:219]
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kernel32
ntdll

CTENoLonger · August 19, 2020, 4:50pm

To remove possible other issues I tested this by making a new pawn using RPGCharacterBase as it’s parent and made a new controller for it using AIController as it’s base. And set it’s PassiveGameplayEffect to initialize all the default attributes to 100. When I start the game the NPC lists it’s health as 1 no matter what I set it’s max health value to be. And if I try to use the Get Max Health function it crashes. For some reason it seems like the Passive Gameplay Effect isn’t applied when the pawn is spawned.

CTENoLonger · August 20, 2020, 9:57pm

Thought I’d write the solution I ended up with even though I still don’t have a definitive answer for what caused the problem.

I ended up removing one layer of children that I had under the C++ parent class RPGCharacterBase. The hierarchy I ended up with is C++ RPGCharacterBase > base class character > base class NPC > NPC i spawn in the world. This resolved the issue and the NPC I spawn has their initial attributes set by my effect used in the Passive Gameplay Effect variable correctly. Hope this helps someone if they run across the same issue I did!