Re: How to add pseudo vector types

[Eli Zaretskii]

> From: Stephen Leake <stephen_leake@stephe-leake.org>
> Cc: Yuan Fu <casouri@gmail.com>,  cpitclaudel@gmail.com,
>   monnier@iro.umontreal.ca,  emacs-devel@gnu.org
> Date: Sun, 25 Jul 2021 11:01:22 -0700
> 
> >> How do we handle such thing in Emacs?
> >
> > We use xmalloc, which calls memory_full when allocation fails, which
> > releases some spare memory we have for this purpose, and tells the
> > user to save the session and exit.
> 
> I'm thinking about how this applies to wisi, when migrating to a module.
> 
> Ada has a built-in allocator; it's probably possible to change that, but
> I'd like to understand exactly why we need to do that.

We need that to allow the user to save the session while he/she can.

> The Ada allocator throws an exception on allocation fail; is it
> sufficient to turn that exception into an elisp signal, and arrange for
> elisp to call memory_full (or take some other action, like killing the
> parser)?

What is a "lisp signal" in this context?

> Another possible reason to change the Ada allocator is if we want to
> expose Ada memory pointers directly to elisp, as Yuan Fu wants to do for
> tree-sitter (I don't plan to do this for wisi). Does that require that
> the pointers be allocated by the same allocator?

Same allocator as what?

> I'm not clear what that would mean for the garbage collector; is it
> then expected to recover the tree-sitter-allocated memory for the
> tree? or does it ignore those lisp objects?

It depends on which Lisp object you wrap those pointers.  User-pointer
object allow you to provide your own "finalizer" function.