GNU bug report logs - #3467
23.0.94; let + make-local-variable => let value made global

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Package: emacs;

Reported by: Lennart Borgman <lennart.borgman <at> gmail.com>

Date: Thu, 4 Jun 2009 21:20:04 UTC

Severity: normal

Tags: wontfix

Merged with 10604

Found in version 23.2

Done: Lars Ingebrigtsen <larsi <at> gnus.org>

Bug is archived. No further changes may be made.

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From: Lennart Borgman <lennart.borgman <at> gmail.com>
To: Stefan Monnier <monnier <at> iro.umontreal.ca>
Cc: 3467 <at> debbugs.gnu.org, emacs-pretest-bug <at> gnu.org
Subject: bug#3467: 23.0.94; let + make-local-variable => let value made  global
Date: Fri, 5 Jun 2009 17:04:01 +0200

On Fri, Jun 5, 2009 at 4:36 PM, Stefan Monnier<monnier <at> iro.umontreal.ca> wrote:
>> If you eval these lines
>>   (defvar w14 "global")
>>   (defvar w15 "global")
>>   (let ((w14 "let")
>>         (w15 "let"))
>>     (set (make-local-variable 'w14) "local")
>>     (message "w14 maybe let: in buffer=%S, global=%S" w14 (default-value 'w14))
>>     (message "w15 maybe let: in buffer=%S, global=%S" w15 (default-value 'w15)))
>>   (message "w14 top level: in buffer=%S, global=%S" w14 (default-value 'w14))
>>   (message "w15 top level: in buffer=%S, global=%S" w15 (default-value 'w15))
>
>> the output will be
>
>>   w14 maybe let: in buffer="local", global="let"
>>   w15 maybe let: in buffer="let", global="let"
>>   w14 top level: in buffer="global", global="let"
>>   w15 top level: in buffer="global", global="global"
>
>> All values here except w14 global value on next last line are arguably
>> correct. The last value of w14 should be "global", not "let".
>
>> It looks like perhaps the call to (make-local-variable w14) does not
>> mark the "global let" value of w14 as let bound (or removes that
>> mark).
>
> Given the way let-binding and buffer-local bindings are currently
> implemented, it's difficult to make it work correctly in all corner
> cases, and even more so without slowing down the common case.
> So don't hold your breath.

I gave a suggestion in the next message for how to implement this:
Check buffer and frame localness before unbind_to in Flet. Would that
really be expensive?
This bug report was last modified 9 years and 198 days ago.

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