bug#36649: 27.0.50; pure space and pdumper

[Stefan Kangas <stefankangas@gmail.com>]

Pip Cet <pipcet@gmail.com> writes:

> On Sat, Aug 22, 2020 at 9:59 AM Andreas Schwab <schwab@linux-m68k.org> wrote:
>> On Aug 22 2020, Pip Cet wrote:
>> > +purecopy (Lisp_Object obj);
>> >
>> >  DEFUN ("purecopy", Fpurecopy, Spurecopy, 1, 1, 0,
>> >         doc: /* Make a copy of object OBJ in pure storage.
>>
>> Perhaps purecopy should be dropped or made a no-op?
>
> I believe that would be a logical next step, yes. The comment in
> loadup.el says hash-consing saves "around 11% of pure space", which
> sounds like it isn't worth the hassle to me.
>
> So my suggestion would be to apply this patch first (removing the C
> parts of pure space), then remove unexec, then turn purecopy into an
> alias for identity and remove as many instances of it as possible.
>
> Just as a reminder, we're still putting a 3 MB block of zero bytes
> into every emacs binary...

To me, the above sounds like a reasonable plan, given the discussion in
this thread and lack of any objections.

> Should this be discussed on emacs-devel?

Bringing this up on emacs-devel could perhaps get a few more eyes on
this before it lands on master.  At the very least, it would inform
everyone about the planned change.  So why not proceed to do that?