Re: MPS: weak hash tables

[Helmut Eller]

On Tue, Jul 02 2024, Pip Cet wrote:

> Also, there's the whole caution thing about weak objects containing
> only unaligned words or words pointing directly to a base object,
> which is only relevant on Unix/i386, IIRC. (MPS emulates instructions
> to simulate fine-grained barriers, which is a really cool idea; I'd
> still like an option to turn it off though...). That would mean we
> have to replace Lisp_Objects and use the ptr member of our union (and
> that's the reason I'm using fixnums rather than plain integers for the
> hash).

Why do you think that the restriction only applies to 32-bit systems?
My interpretation of

  Section 7.4. Caution
  ...
  “Aligned pointer” means a word whose numeric value (that is, its value
  when treated as an unsigned integer) is a multiple of the size of a
  pointer. If you’re using a 64-bit architecture, that means that an
  aligned pointer is a multiple of 8 and its bottom three bits are zero.
  ...

is that it applies to 64-bit machines as well.