[magicalhippo]

> So all malloc implementations have a minimum alignment guarantee. Typically 16 bytes these days on x86

Fun story. Back in the early 2000s, my Delphi OpenGL program randomly crashed when I tried to use vertex buffers. I spent a lot of time checking this and that, before I realized it might be an alignment issue.

Sure enough, Delphi memory allocator at the time only provided 4-byte alignment, while NVIDIA's drivers used aligned SSE instructions which require 16-byte alignment.

So, had to manually align the buffers before passing them to OpenGL.

[badsectoracula]

IMO that sounds either like a bug in Nvidia's drivers (IIRC OpenGL doesn't require that sort of alignment) or -more likely- your code having some other memory related-bug (e.g. accessing data out of bounds) that the extra bytes you got from alignment masked it.

[magicalhippo]

Nah it was definitely NVIDIA's fault. As you say there's nothing in the specs about alignment of those buffers, so they shouldn't be using aligned load instructions.

However Microsoft's malloc at the time was indeed returning 16-byte aligned buffers so they probably didn't notice it in internal testing.