I vaguely recall that this was because 16 byte alignment is the minimum you need for certain foreign types, and it's what malloc() does.  Perhaps check the FFI spec and the guarantees that mallocForeignPtrBytes and friends provide?

Cheers

Simon

On Thu, 11 Oct 2018 at 18:44, Ömer Sinan Ağacan <omeragacan@gmail.com> wrote:

Hi,

I just found out we currently align all pinned array payloads to 16 bytes and
I'm wondering why. I don't see any comments/notes on this, and it's also not
part of the primop documentation. We also have another primop for aligned
allocation: newAlignedPinnedByteArray#. Given that alignment behavior of
newPinnedByteArray# is not documented and we have another one for aligned
allocation, perhaps we can remove alignment in newPinnedByteArray#.

Does anyone remember what was the motivation for always aligning pinned arrays?

Thanks

Ömer
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