From: Stefan Monnier via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
To: Alan Mackenzie <acm@muc.de>
Cc: 59057@debbugs.gnu.org
Subject: bug#59057: Emacs 29. Byte compiler sometimes forgets about a defvar.
Date: Mon, 07 Nov 2022 16:29:15 -0500 [thread overview]
Message-ID: <jwvbkpiv4qh.fsf-monnier+emacs@gnu.org> (raw)
In-Reply-To: <Y2lohC66d/uSi5oz@ACM> (Alan Mackenzie's message of "Mon, 7 Nov 2022 20:20:20 +0000")
>> (defvar VAR) does not "create a variable".
>
> According to both its doc string and the Elisp manual it does.
Where? I'm talking specifically about (defvar VAR) not about
`defvar` in general.
>> It just "locally" declares that this identifier should use dynamic
>> scoping when binding a variable.
> Why "locally"? There's just one obarray involved, which is global.
No, we want to allow `defvar` to have a lexically-local effect.
>> But the better way to write the above code is:
>
>> (defmacro acm-defvar (var)
>> `(progn
>> (defvar ,var)
>> (eval-when-compile
>> (when (version-check)
>> (setq ,var emacs-major-version)))))
>
> There are workarounds, yes. But surely it would be better to fix the
> bug.
It's not a workaround. It's how the programmers say whether they want
the (defvar ,var) declaration to affect all the rest of the code or only
the code within the `when`.
Why put the (defvar ,var) within the `when` if not to limit
its scope?
Stefan
next prev parent reply other threads:[~2022-11-07 21:29 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-05 18:46 bug#59057: Emacs 29. Byte compiler sometimes forgets about a defvar Alan Mackenzie
2022-11-07 13:07 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2022-11-07 20:20 ` Alan Mackenzie
2022-11-07 21:29 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors [this message]
2022-11-08 11:01 ` Alan Mackenzie
2022-11-08 14:12 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2022-11-07 21:31 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2022-11-09 13:40 ` Alan Mackenzie
2022-11-09 17:54 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2022-11-24 19:29 ` Stefan Kangas
2022-11-24 19:33 ` Eli Zaretskii
2022-11-24 20:36 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2022-11-24 21:12 ` Stefan Kangas
2022-11-25 10:36 ` Alan Mackenzie
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