Why is my multidimensional array implementation crashing on Init?

Development Programming & Scripting C++
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1

Hello, i’m making my custom 2D Array implementation and i’m using the following code:

template <typename T>
class TArray2D
{
	TArray<TArray<T>> Array;

	uint32 Rows;
	uint32 Columns;

public:

	void Init(uint32 Rows, uint32 Columns, T Value);

	uint32 GetRows() const;
	uint32 GetColumns() const;

	TArray<T>& operator[](uint32 Row);
};

template <typename T>
void TArray2D<T>::Init(uint32 Rows, uint32 Columns, T Value)
{
	Array.Init(Rows);

	for (uint32 Row = 0; Row < Rows; Row++)
		Array[Row].Init(Value, Columns);

	this->Rows = Rows;
	this->Columns = Columns;
}

When i initialize my TArray2D using the Init method the game crashes on the for loop, more specifically on the following line from TArray::Empty when it’s doing the init of the sub array:

AllocatorInstance.ResizeAllocation(0,ArrayMax,sizeof(ElementType));

Can you tell me what am i doing wrong? Thank you

2

If i use this:

for (uint32 Row = 0; Row < Rows; Row++)
{
	TArray<T> Temp;

	Temp.Init(NULL, Columns);

	Array.Add(Temp);
}

instead of:

Array.Init(Rows);
 
for (uint32 Row = 0; Row < Rows; Row++)
    Array[Row].Init(Value, Columns);

It appears to work (although with Add it creates more positions than i need), but i would like to know why the last method doesn’t work.

3

#2D TArrays: Complete Code Sample

I posted a full code sample on 2D TArray’s here

#Add Uninitialized

Take careful note of the use of AddUninitialized at the end of my example above.

Rama

4

Based on this link i got it working with:

Array.SetNum(Rows, false);

for (uint32 Row = 0; Row < Rows; Row++)
	Array[Row].Init(NULL, Columns);

The SetNum still sets the maximum size bigger than the Rows, so i would still like to know if there is a way to do something like Init

5

After checking a 2D Array example on Lightmass.cpp i ended up doing this:

template <typename T>
void TArray2D<T>::Init(uint32 Rows, uint32 Columns, T Value)
{
	Array.Empty(Rows);
	Array.AddZeroed(Rows);

	for (uint32 Row = 0; Row < Rows; Row++)
		Array[Row].Init(Value, Columns);

	this->Rows = Rows;
	this->Columns = Columns;
}

And with this i have the array with the exact size i wanted.

1 Like
6

Thank you for your answer Rama, looking at your code helped me reach to the solution that i commented, so i think it’s fair your answer is marked as accepted :slight_smile:

7

Hello, I have a crash similar to yours in build only. It was worst (more frequent) when i was using TSet instead of TArray.
Do you have any idea what might happens?