GNU bug report logs - #66940
Dynamic scoping is all weird now?

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From: Dave Goel <deego3 <at> gmail.com>
To: 66940 <at> debbugs.gnu.org, deego3 <at> gmail.com
Subject: bug#66940: Dynamic scoping is all weird now?
Date: Sun, 5 Nov 2023 00:09:36 -0400

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I apologize.I meant to say it should print 0 to 10 the first time around
because ,ii should hardcode the value at the time of macro definition.
But, the second and third time are so absolutely weird?



On Sun, Nov 5, 2023 at 12:06 AM Dave Goel <deego3 <at> gmail.com> wrote:

> I was playing around, checking my sanity re : dynamic scoping.  I'm
> probably rusty, but I could swear that on older emacsen, this sort of code
> would print 33 ten times.
>
>
> On emacs -Q with debian stable (28.2).
> I try this
>
>
> (progn
>   (setq lexical-binding nil)
>
>   (dotimes (ii 10)
>     (defmacro mac ()
>       `(message "%S" ,ii)
>       (sit-for 0.1))
>     (let ((old_ii ii))
>       (setq ii 33)
>       (mac)
>       (setq ii old_ii)
>       )))
>
> Exits without error the first two times, although, strangely, i don't see
> any messages the second time. (I expected to see ten 33's).
>
>
> *(a) As in, the second time, it doesn't print 33 ten times, as we would
> expect.*
> *(b) The third time is stranger. *
> Let's evaluate it a third time! The third time is even weirder.
> The third time, it complains
> Debugger entered--Lisp error: (void-variable ii)
>   (list 'message "%S" ii)
>   (lambda nil (list 'message "%S" ii) (list 'print ii) (sit-for 0.1))()
>   macroexpand((mac) nil)
>   macroexp-macroexpand((mac) nil)
>   macroexp--expand-all((mac))
>   macroexp--all-forms(((setq ii 33) (mac) (setq ii old_ii)))
>   macroexp--expand-all((let ((old_ii ii)) (setq ii 33) (mac) (setq ii
> old_ii)))
>
> and so on.
>
>
> The bug(?) was reproduced on 29.1 as well - by e1f on #emacs
>
> *(c) It gets even funnier. e1f changed ii to var, but the third time, it
> still complained about ii, with the above error message, and not about var.*
> I reproduced that as well.
>
> Dave
>
>
>

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