GNU bug report logs - #28362
26.0.50; [PATCH] gensym in core elisp

Previous Next

To add a comment to this bug, you must first unarchive it, by sending
a message to control AT debbugs.gnu.org, with unarchive 28362 in the body.
You can then email your comments to 28362 AT debbugs.gnu.org in the normal way.

Toggle the display of automated, internal messages from the tracker.

Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Mark Oteiza <mvoteiza <at> udel.edu>
To: bug-gnu-emacs <at> gnu.org
Subject: 26.0.50; [PATCH] gensym in core elisp
Date: Tue, 05 Sep 2017 13:11:23 -0400

[Message part 1 (text/plain, inline)]

Wishlist.

It would be nice to have gensym live in subr.el or C for the utility of
having uniquely named uninterned symbols.  It is helpful, for instance,
in the readability of macroexpansions of pcase and other macros that
generate many uninterned symbols of the same name.

As far as C vs Elisp--cl-gensym is about 10x slower than make-symbol,
but as far as macroexpansion goes, I get the impression gensym is not a
big contributing factor. Consider the following:

(defmacro case-lambda (&rest spec)
  "Return an arbitrary arity function."
  (declare (indent 0) (debug (&rest (pcase-QPAT body))))
  (let ((args (make-symbol "args")))
   `(lambda (&rest ,args)
      (pcase-exhaustive ,args ,@spec))))

(benchmark-run-compiled 1000
  (macroexpand-all
   '(case-lambda
      (`() t)
      (`(,x) (cons x 1))
      (`(,x ,y) (list x y 2))
      (`(,x ,y . ,z) (pcase-lambda (`(,cat ,dog))
                       (vector cat dog x y z 8)))))

The difference between the benchmark with make-symbol and make-symbol
fset to gensym is less than 1% (looking at profiler samples, interval
set to 1us).

I wrote a naïve gensym in C that is only about 1.5x to 2x faster than
cl-gensym (and incompatible because of the inaccessible counter). Patch
attached.

I also attached a patch putting gensym into subr.el.

I've tested both patches.

[gensym_alloc_c.patch (text/x-patch, attachment)]

[gensym.patch (text/x-patch, attachment)]

Message #8 received at 28362 <at> debbugs.gnu.org (full text, mbox):

From: Mark Oteiza <mvoteiza <at> udel.edu>
To: 28362 <at> debbugs.gnu.org
Subject: Re: 26.0.50; [PATCH] gensym in core elisp
Date: Tue, 5 Sep 2017 13:27:33 -0400

[Message part 1 (text/plain, inline)]

On 05/09/17 at 01:11pm, Mark Oteiza wrote:
>I wrote a naïve gensym in C that is only about 1.5x to 2x faster than
>cl-gensym (and incompatible because of the inaccessible counter). Patch
>attached.

There was a bunch of other crap in that patch--clean one attached.

[gensym_alloc_c.patch (text/x-diff, attachment)]

Message #11 received at 28362 <at> debbugs.gnu.org (full text, mbox):

From: Mark Oteiza <mvoteiza <at> udel.edu>
To: 28362 <at> debbugs.gnu.org
Subject: Re: 26.0.50; [PATCH] gensym in core elisp
Date: Mon, 11 Sep 2017 16:35:01 -0400

On 05/09/17 at 01:11pm, Mark Oteiza wrote:
> 
> Wishlist.
> 
> I attached a patch putting gensym into subr.el.

Any comments?  Moving gensym doesn't affect much, so I'll happily
commit, say, at the end of the week.

Message #14 received at 28362 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Mark Oteiza <mvoteiza <at> udel.edu>
Cc: 28362 <at> debbugs.gnu.org
Subject: Re: bug#28362: 26.0.50; [PATCH] gensym in core elisp
Date: Tue, 12 Sep 2017 17:39:12 +0300

> Date: Mon, 11 Sep 2017 16:35:01 -0400
> From: Mark Oteiza <mvoteiza <at> udel.edu>
> 
> On 05/09/17 at 01:11pm, Mark Oteiza wrote:
> > 
> > Wishlist.
> > 
> > I attached a patch putting gensym into subr.el.
> 
> Any comments?  Moving gensym doesn't affect much, so I'll happily
> commit, say, at the end of the week.

I see no reasons to have gensym in C, so let's go with the Lisp
version.

Please also add a NEWS entry about this.

Thanks.

Message #19 received at 28362-done <at> debbugs.gnu.org (full text, mbox):

From: Mark Oteiza <mvoteiza <at> udel.edu>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: 28362-done <at> debbugs.gnu.org
Subject: Re: bug#28362: 26.0.50; [PATCH] gensym in core elisp
Date: Tue, 12 Sep 2017 11:14:24 -0400

On 12/09/17 at 05:39pm, Eli Zaretskii wrote:
> > Date: Mon, 11 Sep 2017 16:35:01 -0400
> > From: Mark Oteiza <mvoteiza <at> udel.edu>
> > 
> > On 05/09/17 at 01:11pm, Mark Oteiza wrote:
> > > 
> > > Wishlist.
> > > 
> > > I attached a patch putting gensym into subr.el.
> > 
> > Any comments?  Moving gensym doesn't affect much, so I'll happily
> > commit, say, at the end of the week.
> 
> I see no reasons to have gensym in C, so let's go with the Lisp
> version.
> 
> Please also add a NEWS entry about this.

Done, thank you.

Previous Next

GNU bug tracking system
Copyright (C) 1999 Darren O. Benham, 1997,2003 nCipher Corporation Ltd, 1994-97 Ian Jackson.