Using XMVECTOR from DirectXMath as a class member causes a crash only in Release Mode?

Question

I\'ve been trying to use XMVECTOR as a class member for a bounding box, since I do a lot of calculations, but I use the XMFLOAT3 only once per frame, so the bounding box has

Answer 1

The class is not being created at an aligned address, so even though the XM* members are aligned on 16-byte boundaries, the parent's alignment miss-aligns them, causing the crash.

To prevent this you need to use _mm_alloc (which really just wraps _aligned_alloc), or replace the default allocator with one that returns blocks minimally aligned to 16 bytes (under x64 this the case with the default allocator).

a simple solution to this in C++ is to create a base class for all classes the contain XM* members that looks like the following:

template<size_t Alignment> class AlignedAllocationPolicy
{
    public:
    static void* operator new(size_t size)
    {
        return _aligned_malloc(size,Alienment);
    }

    static void operator delete(void* memory)
    {
        _aligned_free(memory);
    }
};

class MyAlignedObject : public AlignedAllocationPolicy<16>
{
//...
};

As pointed out by @Dave, this is a minimal example, you'd want to overload all the new and delete operators, specifically new[] and delete[]