Question

I’m making pong in DirectX11 and I’m getting some weird error.

I have a pointer declared inside my Pong class:

XMVECTOR *ballDirection;

And for some reason, whenever I try to access it:

Unhandled exception at 0x002127d8 in DirectX11Pong.exe:
  0xC0000005: Access violation reading location 0x00000000.

I’m pretty sure this is what happens when you try to access a nullptr pointer, but,
before any “accessing” to the pointer happens, I have it initialized:

ballDirection = new XMVECTOR();

For example, the line of code right now I’m getting this error at is the following:

*ballDirection = XMVectorSetX(*ballDirection, 1);

The only other information that I think is relevant is that I tried earlier to turn a single pointer that holds the paddle info into an array of pointers (for multiple players):

(Before)

Sprite *paddle;

(After)

Sprite *paddle[2];

The moment I did this, I got this error accessing ballDirection,
even though it worked perfectly before I made this array, and I changed no code to do with ballDirection while creating the array and modifying the appropriate code.

After I noticed getting this error I changed the code back, and this still happened.

How can I fix this?

Answer 1

Microsoft does say about dynamic allocation of XMVECTOR that:

Allocations from the heap, however, are more complicated. As such, you
need to be careful whenever you use either XMVECTOR or XMMATRIX as a
member of a class or structure to be allocated from the heap.
On Windows x64, all heap allocations are 16-byte aligned, but for
Windows x86, they are only 8-byte aligned.

So you should not just new XMVECTOR there and expect that all works.