From: Lennart Borgman <lennart.borgman@gmail.com>
To: Stefan Monnier <monnier@iro.umontreal.ca>
Cc: emacs-pretest-bug@gnu.org, 3467@emacsbugs.donarmstrong.com
Subject: bug#3467: 23.0.94; let + make-local-variable => let value made global
Date: Sat, 6 Jun 2009 00:48:16 +0200 [thread overview]
Message-ID: <e01d8a50906051548k2d6d9f15o7a5e841579740c79@mail.gmail.com> (raw)
In-Reply-To: <e01d8a50906050804n3a32cd86le9da7360e0482ae2@mail.gmail.com>
On Fri, Jun 5, 2009 at 5:04 PM, Lennart
Borgman<lennart.borgman@gmail.com> wrote:
> On Fri, Jun 5, 2009 at 4:36 PM, Stefan Monnier<monnier@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?
Sigh, and my suggestion was of course unnecessary stupid. What is
needed is of course to record values and frame+buffer localness and
dito values and reset them. Nothing less than this will ever work
correctly, or?
And does not this apply to all uses of specbind + unbind_to?
Can it be sufficient to just change specbind and unbind_to? Is there
anything else that will be affected by changes in the specbind stack?
Since info about buffer+frame is alwas needed should specbinding be
changed to the below form?
struct specbinding
{
Lisp_Object symbol;
Lisp_Object old_value;
Lisp_Object old_buffer_value;
Lisp_Object old_frame_value;
specbinding_func func;
Lisp_Object unused; /* Dividing by 16 is faster than by 12 */
Lisp_Object unused;
Lisp_Object unused;
};
Is this structure used by other functions than specbind and unbind_to?
next prev parent reply other threads:[~2009-06-05 22:48 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-06-04 21:14 bug#3467: 23.0.94; let + make-local-variable => let value made global Lennart Borgman
2009-06-05 14:21 ` Lennart Borgman
2009-06-05 14:36 ` Stefan Monnier
2009-06-05 15:04 ` Lennart Borgman
2009-06-05 22:48 ` Lennart Borgman [this message]
2009-06-05 23:08 ` Lennart Borgman
2009-06-05 23:32 ` Lennart Borgman
2009-06-06 20:11 ` Lennart Borgman
2009-06-07 1:11 ` Lennart Borgman
2009-06-12 22:24 ` Lennart Borgman
2009-06-27 0:24 ` bug#3467: 23.0.94; let + make-local-variable => let value made Stefan Monnier
2009-06-06 20:05 ` bug#3467: 23.0.94; let + make-local-variable => let value made global Richard Stallman
2009-06-06 20:13 ` Lennart Borgman
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