Game crashes when saving

[Antoniusz2115]

Every time I call SaveGame() game crashes. Any idea why?

MouseGameInstance.h

#pragma once

#include "CoreMinimal.h"
#include "Engine/GameInstance.h"
#include "MouseGameInstance.generated.h"


UCLASS()
class AMAZINGMOUSERUNNER_API UMouseGameInstance : public UGameInstance
{
	GENERATED_BODY()

public:	
	UMouseGameInstance();

	class UMouseSaveGame* MouseSaveGame;
	FString SaveSlot = "Save1";

	UFUNCTION(BlueprintCallable)
	void LoadGame();
	UFUNCTION(BlueprintCallable)
	void SaveGame();

	int Coins= 0;
	int Shields = 0;

	int FenceType = 0;
	bool FenceLockState[3] = {true, false, false};

	UFUNCTION(BlueprintPure)
	int GetCoins() { return Coins; }

	UFUNCTION(BlueprintPure)
	int GetFenceType() { return FenceType; }

	UFUNCTION(BlueprintCallable)
	void SetFenceType(int NewType) { FenceType = NewType; }

	void AddCoin() { Coins++; }
};

MouseGameInstance.cpp

#include "MouseGameInstance.h"
#include "MouseSaveGame.h"
#include "Kismet/GameplayStatics.h"


UMouseGameInstance::UMouseGameInstance()
{
    MouseSaveGame = Cast<UMouseSaveGame>(UGameplayStatics::LoadGameFromSlot(SaveSlot, 0));

    UE_LOG(LogTemp, Error, TEXT("Working..."));

    if(MouseSaveGame == nullptr)
    {
        MouseSaveGame = Cast<UMouseSaveGame>(UGameplayStatics::CreateSaveGameObject(UMouseSaveGame::StaticClass()));

        MouseSaveGame->Coins = 0;
        MouseSaveGame->FenceType = 0;

        UGameplayStatics::SaveGameToSlot(MouseSaveGame, SaveSlot, 0);

        
    }
    LoadGame();
}

void UMouseGameInstance::LoadGame()
{
    Coins = MouseSaveGame->Coins;
    FenceType = MouseSaveGame->FenceType;
}

void UMouseGameInstance::SaveGame()
{
    if(MouseSaveGame)
    {
        MouseSaveGame->Coins = Coins;
        MouseSaveGame->FenceType = FenceType;

        UGameplayStatics::SaveGameToSlot(MouseSaveGame, SaveSlot, 0);
    }
}

Crash log

Unhandled Exception: EXCEPTION_ACCESS_VIOLATION reading address 0xffffffffffffffff

UnrealEditor_Engine
UnrealEditor_Engine
UnrealEditor_AmazingMouseRunner_0033!UMouseGameInstance::SaveGame() [D:\UE5\nauka\AmazingMouseRunner\Source\AmazingMouseRunner\MouseGameInstance.cpp:43]
UnrealEditor_AmazingMouseRunner_0033!AMouseController::Death() [D:\UE5\nauka\AmazingMouseRunner\Source\AmazingMouseRunner\MouseController.cpp:37]
UnrealEditor_AmazingMouseRunner_0033!AMouseCharacter::Death() [D:\UE5\nauka\AmazingMouseRunner\Source\AmazingMouseRunner\MouseCharacter.cpp:205]
UnrealEditor_AmazingMouseRunner_0033!ABasePlatform::DeathOverlap() [D:\UE5\nauka\AmazingMouseRunner\Source\AmazingMouseRunner\BasePlatform.cpp:114]
UnrealEditor_AmazingMouseRunner_0033!ABasePlatform::execDeathOverlap() [D:\UE5\nauka\AmazingMouseRunner\Intermediate\Build\Win64\UnrealEditor\Inc\AmazingMouseRunner\UHT\BasePlatform.gen.cpp:37]
UnrealEditor_CoreUObject
UnrealEditor_CoreUObject
UnrealEditor_Engine
UnrealEditor_Engine
UnrealEditor_Engine
UnrealEditor_Engine
UnrealEditor_Engine
UnrealEditor_Engine
UnrealEditor_Engine
UnrealEditor_Engine
UnrealEditor_Engine
UnrealEditor_AmazingMouseRunner_0033!AMouseCharacter::Diving() [D:\UE5\nauka\AmazingMouseRunner\Source\AmazingMouseRunner\MouseCharacter.cpp:113]
UnrealEditor_AmazingMouseRunner_0033!AMouseCharacter::Tick() [D:\UE5\nauka\AmazingMouseRunner\Source\AmazingMouseRunner\MouseCharacter.cpp:49]
UnrealEditor_Engine
UnrealEditor_Engine
UnrealEditor_Engine
UnrealEditor_Engine
UnrealEditor_Core
UnrealEditor_Core
UnrealEditor_Core
UnrealEditor_Engine
UnrealEditor_Engine
UnrealEditor_Engine
UnrealEditor_Engine
UnrealEditor_UnrealEd
UnrealEditor_UnrealEd
UnrealEditor
UnrealEditor
UnrealEditor
UnrealEditor
UnrealEditor
UnrealEditor
kernel32
ntdll

[MagForceSeven]

Pointers to UObjects need to have the UPROPERTY macro so that the reflection system & therefore the garbage collector can see them. WIthout that, the garbage collector doesn’t realize that the object is still in use, so it destroys the save object.

[Antoniusz2115]

Thanks. It’s not crashing anymore, but there is another problem. When SaveGame() function is called MouseSaveGame is nullptr even though I create it in UMouseGameInstance(). Do you know why is this happening?

[Antoniusz2115]

So I tried to LoadGameFromSlot() again in SaveGame() and it’s working but I’m still curious why wasn’t it enough to Load it in constructor.

[MagForceSeven]

There’s probably a timing thing because you shouldn’t be doing those thing in the constructor. You want to be doing all that save game stuff by overriding the Init function instead.

[Antoniusz2115]

Thank you again