[fpc-devel] Aligned dynamic arrays

[Ryan Joseph]

I would like to attempt to implement this feature request (https://bugs.freepascal.org/view.php?id=34031 for my boss) which has the SetLength intrinsic return aligned memory. We need this for the Metal framework which requires all vertex buffer memory to aligned on 4k boundaries so we can’t use dynamic arrays in their current form (see the bug report for example code).

I’ve looked at the dynamic array implementation (dynarr.inc) and it appears that I could over allocate and extend the header (tdynarray) to include an extra field which stores the amount of padding until the actual array elements start (which is aligned). It would complicit the code to some extent however because the current design relies on lots of pointer math.

Is this ok that I add this? Marco said in the comments there was a need so I assume this is a go but I wanted to ask first.

Regards,
	Ryan Joseph