Re: MPS signals and Emacs

[Eli Zaretskii]

> From: Gerd Möllmann <gerd.moellmann@gmail.com>
> Cc: Eli Zaretskii <eliz@gnu.org>,  eller.helmut@gmail.com,  
> emacs-devel@gnu.org
> Date: Mon, 22 Apr 2024 09:49:29 +0200
> 
> Paul Eggert <eggert@cs.ucla.edu> writes:
> 
> > On 2024-04-22 00:19, Gerd Möllmann wrote:
> >>> I assume that MPS is not being used to allocate any of Emacs's own
> >>> objects, as copying collectors are incompatible with Emacs's habit of
> >>> squirreling away pointers inside integers.
> >> It's excactly that, a (mostly) copying collector for Emacs :-).
> >
> > Since Emacs uses a conservative collector, how can MPS move Emacs
> > objects? MPS can't know which words are pointers and which are not, so
> > it can't update pointers when Emacs objects move.
> 
> There are ambigupus and there are exact referenes. An object references
> from at least one ambiguos reference cannot be moved, others can.
> 
> Where exact and where ambigous references are (or areas of these), one
> has to tell MPS, of course. It's not like Boehm's collector where
> everything is ambiguous.

What do "exact reference" and "ambiguous reference" mean, in Emacs
terms?