Comments on: Lisp pointer size?

By: Senko Rasic

Senko Rasic — Wed, 30 Nov -0001 00:00:00 +0000

Lisp uses tagged pointers, that is, they use a few bits of
the pointer to specify pointer type, which leaves fewer
bits around to actually point to the object. If you're
on 32bit arch, 128mb == 2^27, and, say, 5 bits are used
by Emacs Lisp to tag the pointers, then you'd really be
running out of it.
But I'm not emacs (or even lisp) guru, and all of the above is just my educated guess, so it can easily be wrong.

By: Alexander Larsson

Alexander Larsson — Wed, 30 Nov -0001 00:00:00 +0000

I assumed that the tag-bits in a pointer used the two lowest bits by only allowing pointers to be at even 32bit positions.

By: d

Wed, 30 Nov -0001 00:00:00 +0000

Use emacs-22 (from CVS), the size has now been increased to 256MB. Besides that it has quite a lot of very useful features.
More than 2 tag bits are needed to distiguish between the different
data types: integers, symbols, strings, conses, floats, etc.