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Re: t and nil in pure memory?

From: Stefan Monnier
Subject: Re: t and nil in pure memory?
Date: Thu, 12 Nov 2009 10:22:05 -0500
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/23.1.50 (gnu/linux)

>> > The last GC before dumping generates 200K calls to mark_object, of those
>> > 20K have Qt or Qnil as an argument.
>> > Would it make sense to put Qt and Qnil in pure memory?
>> No, because they may contain pointers to objects that aren't in pure
>> memory (via the plist).

> In principle, you could scratch the plist slot from symbols themselves,
> and instead make `symbol-plist' go over an EQ hash-table. (Such
> externalizing of the symbol plist may make more sense in other dialects
> of Lisp where the plist is used less often than in Elisp -- even though
> I'm not aware of any implementation which does.)

Actually, it's even worse than that: (interned) symbols have a `next'
field which points to the next symbol in the obarray (hash) bucket.
So that's yet another reason why (pure)symbols can have pointers to non
pure memory.


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