Seemingly Random EXCEPTION_ACCESS_VIOLATION thrown after random amount of time playing in editor

Development Programming & Scripting C++
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1

Hi, I’ve been writing a state system based on the state pattern using cpp for a character in ue5.

I have come across an error with the engine where it seems to crash due to an EXCEPTION_ACCESS_VIOLATION after a random amount of time while doing nothing in particular. I understand that this error means that there was some memory that the engine attempted to access and failed. Every time it crashes there could be a different result. I have noticed a few different recurring crash logs.

1. The first crash log that I will receive points to a line in my code. The hex value would be one of the following: 0x00000000, 0xfffffffffff, or a seemingly random value. This originally caused me to believe that I was attempting to call a function on a nullptr value. This is the code segment that I am pointed to:

void ATimeTraveler::Tick(float DeltaTime)
{
	Super::Tick(DeltaTime);
	if (CurrentState != nullptr) {
		assert(CurrentState != nullptr);
		CurrentState->Update(); // this is the line that the error points to
	}
	else {
		UE_LOG(LogTemp, Warning, TEXT("Current State is nullptr"));
	}
}

ATimeTraveler is a class which extends the basic ACharacter class. The line in my code is surrounded in a conditional where it will only run given that CurrentState != nullptr and I assert that it is not nullptr. I will still receive this version of the crash log despite this.

2. The other type of crash log i will receive will similarly point to either a 0x0000000, 0xffffffffff, or seemingly random value, but will not mention any lines from my written code, but only values such as UnrealEditor_Engine and UnrealEditor_Core.

I am completely lost as to why I could be getting this error. Please let me know if you would like me to provide anymore information. Thank you for any help in advance!

2

Does you CurrentState variable marked as UPROPERTY? If CurrentState type is UObject child, it can be garbage collected at any time and this value will be invalid.

1 Like
3

I do not declare it as a UPROPERTY.
Here is the line in my character class header file
UBaseState* CurrentState;

This is the header file for the UBaseState class:

// Fill out your copyright notice in the Description page of Project Settings.

#pragma once

class ATimeTraveler;

#include "CoreMinimal.h"
#include "UObject/NoExportTypes.h"
#include "BaseState.generated.h"

/**
 * 
 */
UCLASS(Abstract, BlueprintType, Blueprintable)
class TIMEJUMP_API UBaseState : public UObject
{
	GENERATED_BODY()
	
public:

	UBaseState();
	~UBaseState();

	FString StateType;

	virtual void Update();
	virtual UBaseState* HandleInput(ATimeTraveler*, FString);
	virtual void Enter(ATimeTraveler*);

	UFUNCTION(BlueprintCallable)
	FString GetStateType();

	UBaseState* DetermineNewState(UBaseState*, ATimeTraveler*);
};

If I am understanding correctly, what you think might be the problem is that because I did not mark the variable as a UPROPERTY, UE5 isn’t handling the data as expected, and could be sending the data to the garbage collector preemptively?

I will try to make these changes and will post an update when I finish testing.

4

I believe not declaring them with UPROPERTY was the issue. Thank you so much! Something to note was that I had to move my pointer definitions to inside the BeginPlay function rather than the actor constructor once I declared them with the UPROPERTY() macro