I'm getting a fatal error, seemingly, while setting a float. How should I debug this?

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1

I am getting a “Fatal error!/Unhandled Exception: EXCEPTION_ACCESS_VIOLATION” in my crash log. The crash occurs within a few minutes after the game has begun. The log then points me to a line in the code where I am setting a float to 0. My main question, is the crash log reliable, or should I be looking somewhere else for the bug? Or do I have some fundamental misunderstanding of c++/ue4? Thanks in advance for any help. I am using 4.14

My code:

// Called every frame
void ALife::Tick(float DeltaTime)
{
	Super::Tick(DeltaTime);

	LocalTickTimer += DeltaTime;
	if (LocalTickTimer >= LocalTickTimerCD)  //This is called every .1 seconds
	{
		ConstantTick(LocalTickTimer);  //The culprit?

		LocalTickTimer = 0.0f;  -------------------------- //This is line 84
	}
}

The crash log:

[2017.07.13-07.58.31:762][591]LogWindows:Error: === Critical error: ===
[2017.07.13-07.58.31:762][591]LogWindows:Error: 
[2017.07.13-07.58.31:762][591]LogWindows:Error: Fatal error!
[2017.07.13-07.58.31:762][591]LogWindows:Error: 
[2017.07.13-07.58.31:762][591]LogWindows:Error: Unhandled Exception: EXCEPTION_ACCESS_VIOLATION 0x00000000
[2017.07.13-07.58.31:762][591]LogWindows:Error: 
[2017.07.13-07.58.31:762][591]LogWindows:Error: 
[2017.07.13-07.58.31:762][591]LogWindows:Error: DFRPG6.exe!ALife::Tick() [c:\\documents\unreal projects\dfrpg6\source\dfrpg6\life.cpp:84]
[2017.07.13-07.58.31:762][591]LogWindows:Error: DFRPG6.exe!AActor::TickActor()
[2017.07.13-07.58.31:762][591]LogWindows:Error: DFRPG6.exe!FActorTickFunction::ExecuteTick()
[2017.07.13-07.58.31:762][591]LogWindows:Error: DFRPG6.exe!FTickFunctionTask::DoTask()
[2017.07.13-07.58.31:762][591]LogWindows:Error: DFRPG6.exe!TGraphTask<FTickFunctionTask>::ExecuteTask()
[2017.07.13-07.58.31:762][591]LogWindows:Error: DFRPG6.exe!FNamedTaskThread::ProcessTasksNamedThread()
[2017.07.13-07.58.31:762][591]LogWindows:Error: DFRPG6.exe!FNamedTaskThread::ProcessTasksUntilQuit()
[2017.07.13-07.58.31:762][591]LogWindows:Error: DFRPG6.exe!FTaskGraphImplementation::WaitUntilTasksComplete()
[2017.07.13-07.58.31:762][591]LogWindows:Error: DFRPG6.exe!FTickTaskSequencer::ReleaseTickGroup()
[2017.07.13-07.58.31:762][591]LogWindows:Error: DFRPG6.exe!FTickTaskManager::RunTickGroup()
[2017.07.13-07.58.31:762][591]LogWindows:Error: DFRPG6.exe!UWorld::RunTickGroup()
[2017.07.13-07.58.31:762][591]LogWindows:Error: DFRPG6.exe!UWorld::Tick()
[2017.07.13-07.58.31:762][591]LogWindows:Error: DFRPG6.exe!UGameEngine::Tick()
[2017.07.13-07.58.31:762][591]LogWindows:Error: DFRPG6.exe!FEngineLoop::Tick()
[2017.07.13-07.58.31:762][591]LogWindows:Error: DFRPG6.exe!GuardedMain()
[2017.07.13-07.58.31:763][591]LogWindows:Error: DFRPG6.exe!GuardedMainWrapper()
[2017.07.13-07.58.31:763][591]LogWindows:Error: DFRPG6.exe!WinMain()
[2017.07.13-07.58.31:763][591]LogWindows:Error: DFRPG6.exe!__scrt_common_main_seh() [f:\dd\vctools\crt\vcstartup\src\startup\exe_common.inl:255]
[2017.07.13-07.58.31:763][591]LogWindows:Error: KERNEL32.DLL
[2017.07.13-07.58.31:763][591]LogWindows:Error: ntdll.dll
[2017.07.13-07.58.31:763][591]LogWindows:Error: ntdll.dll
[2017.07.13-07.58.31:763][591]LogWindows:Error: 
[2017.07.13-07.58.31:896][591]LogExit: Executing StaticShutdownAfterError
[2017.07.13-07.58.32:487][591]LogWindows: FPlatformMisc::RequestExit(1)
[2017.07.13-07.58.32:501][591]Log file closed, 07/13/17 02:58:32
2

What ConstantTick does? Can you post that. I think problem should be there

3

Hey, thanks for answering. If the log can say line 84 but mean ConstantTick (line 82), it can be any number of things. I won’t bother you guys with debugging that, I was just making sure that would be the case before I pull my hair out debugging it. Thanks.

4

Okay im sure it is not caused by setting float to 0.
That can happen only when memory / memory addresses corrupted and float is invalid… but this is a constant variable, so it is impossibru except if your physical memory has trouble and this float always try to save there lol :smiley: (cant be)

GC also dont will collect this type of variable, but for sure mark with empty UPROPERTY()

And sometimes compiler doing weird thing and cache wrong headers etc.
I suggest to do full clean and full rebuild, sometimes will help.

If this will not help, debug did a mistake and stopped in wrong line and crash happens because of some async operation, timer or in constant tick function