GNU bug report logs - #66117
30.0.50; `find-buffer-visiting' is slow when opening large number of buffers

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Package: emacs;

Reported by: Ihor Radchenko <yantar92 <at> posteo.net>

Date: Wed, 20 Sep 2023 08:53:02 UTC

Severity: minor

Found in version 30.0.50

Done: Eli Zaretskii <eliz <at> gnu.org>

Bug is archived. No further changes may be made.

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Message #441 received at 66117 <at> debbugs.gnu.org (full text, mbox):

From: Stefan Monnier <monnier <at> iro.umontreal.ca>
To: Ihor Radchenko <yantar92 <at> posteo.net>
Cc: Gerd Möllmann <gerd.moellmann <at> gmail.com>,
 dmitry <at> gutov.dev, Eli Zaretskii <eliz <at> gnu.org>, mattias.engdegard <at> gmail.com,
 66117 <at> debbugs.gnu.org
Subject: Re: bug#66117: 30.0.50; `find-buffer-visiting' is slow when opening
 large number of buffers
Date: Mon, 01 Jan 2024 20:30:48 -0500

Ihor Radchenko [2024-01-01 18:02:30] wrote:

> Gerd Möllmann <gerd.moellmann <at> gmail.com> writes:
>
>>> (defvar-local let-tests-buffer-local-var 'value)
>>> (with-temp-buffer
>>>   (setq-local let-tests-buffer-local-var 'baz)
>>>   (let ((let-tests-buffer-local-var 'bar))
>>>     ;; This is failing.
>>>     (should (eq 'bar (default-value 'let-tests-buffer-local-var)))
>>
>> C-h f default-value explains this:
>>
>>   Return SYMBOL’s default value.
>>   This is the value that is seen in buffers that do not have their own values
>>   for this variable.
>
> Are you saying that `let' never changes `default-value' output?
> Unfortunately, no.

Indeed, see the doc that Eli quoted 10 posts "ago":

    [...] ELisp manual, which describes the effect of
    make-variable-buffer-local:

        A peculiar wrinkle of this feature is that binding the variable
        (with ‘let’ or other binding constructs) does not create
        a buffer-local binding for it.  Only setting the variable (with
        ‘set’ or ‘setq’), while the variable does not have a ‘let’-style
        binding that was made in the current buffer, does so.

IOW, `let` changes the binding that is "current": if the variable is
buffer-local in the current buffer it changes that buffer-local value
and otherwise it changes the global value.
[ This for "automatically buffer-local variables".  ]


        Stefan
This bug report was last modified 1 year and 135 days ago.

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