[ENGINE BUG] TArray64 RangeCheck returns incorrect error messages for values over 32 bit

Development Programming & Scripting
1

If you try to access TArray64 value past it’s 32 bit you will get incorrect error message.

Steps to reproduce:

	TArray64<float> DebugMatrices;
    int64 n = 2093952;
    DebugMatrices.AddZeroed(n*3*841); // n*3*841 = 5 283 040 896, 32 bit limit is 2 147 483 647
    UE_LOG(LogTemp, Warning, TEXT("DEBUG_LOG: Zeroed 5 283 040 896 matrices len %lld"), DebugMatrices.Num());
    UE_LOG(LogTemp, Warning, TEXT("last value %f"), DebugMatrices[n*3*841-1]);
    UE_LOG(LogTemp, Warning, TEXT("last+1 value is %f"), DebugMatrices[n*3*841]);

The error:

|||[2022.04.21 - 17.26.37:948][33]LogTemp : Warning : DEBUG_LOG : Zeroed 5 283 040 896 matrices len 5283040896|
|||[2022.04.21 - 17.26.37:948][33]LogTemp : Warning : last value 0|
|||[2022.04.21 - 17.26.37:948][33]LogOutputDevice : Warning :|
Assertion failed: (Index >= 0) & (Index < ArrayNum) [File:C:\3D_Software\UE_5.0\Engine\Source\Runtime\Core\Public\Containers\Array.h] [Line: 691] Array index out of bounds: 988073600 from an array of size 988073600

Expected error:


Assertion failed: (Index >= 0) & (Index < ArrayNum) [File:C:\3D_Software\UE_5.0\Engine\Source\Runtime\Core\Public\Containers\Array.h] [Line: 691] Array index out of bounds: 5283040896 from an array of size 5283040896

The part of the engine code that responsible for bug. I guess the solution is to replace %i with %lld in checkf.

	FORCEINLINE void RangeCheck(SizeType Index) const
	{
		CheckInvariants();

		// Template property, branch will be optimized out
		if (AllocatorType::RequireRangeCheck)
		{
			checkf((Index >= 0) & (Index < ArrayNum),TEXT("Array index out of bounds: %i from an array of size %i"),Index,ArrayNum); // & for one branch
		}
	}

Github code location -
https://github.com/EpicGames/UnrealEngine/blob/46544fa5e0aa9e6740c19b44b0628b72e7bbd5ce/Engine/Source/Runtime/Core/Public/Containers/Array.h#L691

Same error goes for ArrayView64 - https://github.com/EpicGames/UnrealEngine/blob/46544fa5e0aa9e6740c19b44b0628b72e7bbd5ce/Engine/Source/Runtime/Core/Public/Containers/ArrayView.h#L254

1 Like
3

As TArray64 is a template of TArray, it’s a generic type. It’s most useful when triggering an exception in debug mode anyway…

template<typename T, typename Allocator = FDefaultAllocator> class TArray;
template<typename T> using TArray64 = TArray<T, FDefaultAllocator64>;
template<typename T, typename SizeType = int32> class TArrayView;
template<typename T> using TArrayView64 = TArrayView<T, int64>;
template<typename T, typename SizeType = int32> using TConstArrayView = TArrayView<const T, SizeType>;
template<typename T> using TConstArrayView64 = TConstArrayView<T, int64>;
template<typename T> class TTransArray;