Received: (at 59057) by debbugs.gnu.org; 25 Nov 2022 10:36:17 +0000 From debbugs-submit-bounces <at> debbugs.gnu.org Fri Nov 25 05:36:17 2022 Received: from localhost ([127.0.0.1]:33646 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <debbugs-submit-bounces <at> debbugs.gnu.org>) id 1oyW49-0004wU-9a for submit <at> debbugs.gnu.org; Fri, 25 Nov 2022 05:36:17 -0500 Received: from mx3.muc.de ([193.149.48.5]:34280) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <acm@HIDDEN>) id 1oyW47-0004wD-80 for 59057 <at> debbugs.gnu.org; Fri, 25 Nov 2022 05:36:15 -0500 Received: (qmail 48675 invoked by uid 3782); 25 Nov 2022 11:36:07 +0100 Received: from acm.muc.de (p4fe1573d.dip0.t-ipconnect.de [79.225.87.61]) (using STARTTLS) by colin.muc.de (tmda-ofmipd) with ESMTP; Fri, 25 Nov 2022 11:36:07 +0100 Received: (qmail 4710 invoked by uid 1000); 25 Nov 2022 10:36:06 -0000 Date: Fri, 25 Nov 2022 10:36:06 +0000 To: Stefan Kangas <stefankangas@HIDDEN> Subject: Re: bug#59057: Emacs 29. Byte compiler sometimes forgets about a defvar. Message-ID: <Y4Calk5lh6iGsLC5@ACM> References: <Y2avmeQhiTntL1q2@ACM> <jwvsfiux6so.fsf-monnier+emacs@HIDDEN> <Y2lohC66d/uSi5oz@ACM> <jwv5yfqv4fx.fsf-monnier+emacs@HIDDEN> <Y2ut6a7AONZYR7Sy@ACM> <jwvsfisqakd.fsf-monnier+emacs@HIDDEN> <CADwFkm=z8STfz5abAUc-Y72z-cH_XwDxvKwi9qGWDnhTcxxOEw@HIDDEN> <jwvk03kks71.fsf-monnier+emacs@HIDDEN> <CADwFkm=uPXmwU_efbjXb5AcZ7yd+pzzWbRiv6hgre5PTXXBPbQ@HIDDEN> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <CADwFkm=uPXmwU_efbjXb5AcZ7yd+pzzWbRiv6hgre5PTXXBPbQ@HIDDEN> X-Submission-Agent: TMDA/1.3.x (Ph3nix) From: Alan Mackenzie <acm@HIDDEN> X-Primary-Address: acm@HIDDEN X-Spam-Score: 0.0 (/) X-Debbugs-Envelope-To: 59057 Cc: 59057 <at> debbugs.gnu.org, Stefan Monnier <monnier@HIDDEN> X-BeenThere: debbugs-submit <at> debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: <debbugs-submit.debbugs.gnu.org> List-Unsubscribe: <https://debbugs.gnu.org/cgi-bin/mailman/options/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=unsubscribe> List-Archive: <https://debbugs.gnu.org/cgi-bin/mailman/private/debbugs-submit/> List-Post: <mailto:debbugs-submit <at> debbugs.gnu.org> List-Help: <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=help> List-Subscribe: <https://debbugs.gnu.org/cgi-bin/mailman/listinfo/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=subscribe> Errors-To: debbugs-submit-bounces <at> debbugs.gnu.org Sender: "Debbugs-submit" <debbugs-submit-bounces <at> debbugs.gnu.org> X-Spam-Score: -1.0 (-) Hello, Stefan. On Thu, Nov 24, 2022 at 22:12:07 +0100, Stefan Kangas wrote: > > I don't see any concrete benefit. It's only a problem of documentation > > and/or teaching programmers. If we could go back to 1984 maybe it would > > be worth it to make a different decision, but the cost of the change > > doesn't seem worth the very minor (and hypothetical) benefit. > So should this bug report be closed? The action of defvar can't really be changed any more, but the documentation, which is rather confusing, could be improved. I would suggest leaving the bug open until this has been done. Unfortunately, I won't have much time to look at this in the next few days. -- Alan Mackenzie (Nuremberg, Germany).
bug-gnu-emacs@HIDDEN:bug#59057; Package emacs.
Full text available.Received: (at 59057) by debbugs.gnu.org; 24 Nov 2022 21:12:26 +0000 From debbugs-submit-bounces <at> debbugs.gnu.org Thu Nov 24 16:12:26 2022 Received: from localhost ([127.0.0.1]:60421 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <debbugs-submit-bounces <at> debbugs.gnu.org>) id 1oyJWE-0007rI-EA for submit <at> debbugs.gnu.org; Thu, 24 Nov 2022 16:12:26 -0500 Received: from mail-oi1-f174.google.com ([209.85.167.174]:44730) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <stefankangas@HIDDEN>) id 1oyJWC-0007r2-OI for 59057 <at> debbugs.gnu.org; Thu, 24 Nov 2022 16:12:25 -0500 Received: by mail-oi1-f174.google.com with SMTP id e205so2597240oif.11 for <59057 <at> debbugs.gnu.org>; Thu, 24 Nov 2022 13:12:24 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc:subject:date:message-id:reply-to; bh=w0kzUmQsrxNt/SAI1dlAG+CyqiYhfeS+V7Lr/06Wqyk=; b=ODMpm47686DRqVri62mEa3gCciSed1DlxiyVtN0J7ru7J+r1VdQlBgTeb6T8DQrE9e f0CuACfFvFu7I88PODrZEoPTGQVRjFUMel9j8EEYNEBZIiSSZ7knjRj9LBjWmfoS4X/i KdGwFeT4aGwtGyLs5W8pFGs5fO2Yb/joyIf69nBSr+W602fVIJ3lnGMyOQ9bCkRPpigV nlkwpDvVYEws3qx+2fU9m+Qaa+qRwDT0Owrn/XFixx8HtnKRcMo7Y32clcAC0xeSkLF0 b8jjfpN5Ct9SEMV57OwMEShwniJta9BHui/PNBQVc33P2SB9lfcCvHc4u0nU1F83sr6d AeOQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=w0kzUmQsrxNt/SAI1dlAG+CyqiYhfeS+V7Lr/06Wqyk=; b=2XnmWPSw8CojzRzkdkBsEd/IIYWfOL7q4dXkVpdw0BKDoNfbwsOORWHhTPWTzXADUk jkrd60SFDlQDiyGPTTnxKc2QaKHxVhRUJDwXu5zmmCpkpvlUkJCtQ+IEuRqpbpptGqZ6 xCp8ETg5MJZbN0anWVN/GTDWBdeKyBMDOnqNOs8Y7r8ZZD7oL3/qWuQtZm+unvMswVR4 SpsOLCxuuUMfVxvIPRihWEF8IJBYybLYadtJwHzRddrIdUiwjmSiOgGLkKZdGq17Jx4t aOe/b1Ly1QqMMKVZJ/ETbZD0uA3/ar5qZwxGexs09cbZuO3YTsU2lN1sNLNMkBlvjrgq ilxw== X-Gm-Message-State: ANoB5pmleqi3bLsDiOVAoHhTIjMJF27he8IlFuLvUewDS9CgAFhC6kNB t56sv/PpgOUlx/zzDu3SBv/Ag4aaJEZqdkPhGyU= X-Google-Smtp-Source: AA0mqf4UZNKl2FhZkwhkeBxCjX+rHpNG9P7HA0qVnqR2/w6EL0thl9+CQz+VOTCZiVCieZ6CNQ4Dmuj6ho3pizsvW+s= X-Received: by 2002:a05:6808:2229:b0:35b:2b17:af81 with SMTP id bd41-20020a056808222900b0035b2b17af81mr7681213oib.199.1669324338967; Thu, 24 Nov 2022 13:12:18 -0800 (PST) MIME-Version: 1.0 References: <Y2avmeQhiTntL1q2@ACM> <jwvsfiux6so.fsf-monnier+emacs@HIDDEN> <Y2lohC66d/uSi5oz@ACM> <jwv5yfqv4fx.fsf-monnier+emacs@HIDDEN> <Y2ut6a7AONZYR7Sy@ACM> <jwvsfisqakd.fsf-monnier+emacs@HIDDEN> <CADwFkm=z8STfz5abAUc-Y72z-cH_XwDxvKwi9qGWDnhTcxxOEw@HIDDEN> <jwvk03kks71.fsf-monnier+emacs@HIDDEN> In-Reply-To: <jwvk03kks71.fsf-monnier+emacs@HIDDEN> From: Stefan Kangas <stefankangas@HIDDEN> Date: Thu, 24 Nov 2022 22:12:07 +0100 Message-ID: <CADwFkm=uPXmwU_efbjXb5AcZ7yd+pzzWbRiv6hgre5PTXXBPbQ@HIDDEN> Subject: Re: bug#59057: Emacs 29. Byte compiler sometimes forgets about a defvar. To: Stefan Monnier <monnier@HIDDEN> Content-Type: text/plain; charset="UTF-8" X-Spam-Score: 0.0 (/) X-Debbugs-Envelope-To: 59057 Cc: Alan Mackenzie <acm@HIDDEN>, 59057 <at> debbugs.gnu.org X-BeenThere: debbugs-submit <at> debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: <debbugs-submit.debbugs.gnu.org> List-Unsubscribe: <https://debbugs.gnu.org/cgi-bin/mailman/options/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=unsubscribe> List-Archive: <https://debbugs.gnu.org/cgi-bin/mailman/private/debbugs-submit/> List-Post: <mailto:debbugs-submit <at> debbugs.gnu.org> List-Help: <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=help> List-Subscribe: <https://debbugs.gnu.org/cgi-bin/mailman/listinfo/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=subscribe> Errors-To: debbugs-submit-bounces <at> debbugs.gnu.org Sender: "Debbugs-submit" <debbugs-submit-bounces <at> debbugs.gnu.org> X-Spam-Score: -1.0 (-) > I don't see any concrete benefit. It's only a problem of documentation > and/or teaching programmers. If we could go back to 1984 maybe it would > be worth it to make a different decision, but the cost of the change > doesn't seem worth the very minor (and hypothetical) benefit. So should this bug report be closed?
bug-gnu-emacs@HIDDEN:bug#59057; Package emacs.
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From: Stefan Monnier <monnier@HIDDEN>
To: Stefan Kangas <stefankangas@HIDDEN>
Subject: Re: bug#59057: Emacs 29. Byte compiler sometimes forgets about a
defvar.
In-Reply-To: <CADwFkm=z8STfz5abAUc-Y72z-cH_XwDxvKwi9qGWDnhTcxxOEw@HIDDEN>
(Stefan Kangas's message of "Thu, 24 Nov 2022 11:29:32 -0800")
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> I guess defvar will have to stay as it is. But would it make sense to
> add a new `declare-variable' function, and then document the form
>
> (defvar <foo>)
>
> to be considered deprecated?
I don't see any concrete benefit. It's only a problem of documentation
and/or teaching programmers. If we could go back to 1984 maybe it would
be worth it to make a different decision, but the cost of the change
doesn't seem worth the very minor (and hypothetical) benefit.
Stefan
bug-gnu-emacs@HIDDEN:bug#59057; Package emacs.
Full text available.Received: (at 59057) by debbugs.gnu.org; 24 Nov 2022 19:33:13 +0000 From debbugs-submit-bounces <at> debbugs.gnu.org Thu Nov 24 14:33:12 2022 Received: from localhost ([127.0.0.1]:60254 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <debbugs-submit-bounces <at> debbugs.gnu.org>) id 1oyHyC-0000qs-Jx for submit <at> debbugs.gnu.org; Thu, 24 Nov 2022 14:33:12 -0500 Received: from eggs.gnu.org ([209.51.188.92]:35054) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <eliz@HIDDEN>) id 1oyHyA-0000qe-T6 for 59057 <at> debbugs.gnu.org; Thu, 24 Nov 2022 14:33:11 -0500 Received: from fencepost.gnu.org ([2001:470:142:3::e]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from <eliz@HIDDEN>) id 1oyHy4-0004Pe-AO; Thu, 24 Nov 2022 14:33:04 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=gnu.org; s=fencepost-gnu-org; h=References:Subject:In-Reply-To:To:From:Date: mime-version; bh=VMxoLzXZPyX/G5o0+5jjZ6MTZWPKPCc4sRmIs034KSc=; b=QHD3dhjGyv9c LkTVY9YJyTQMjgRToq4VWUzOWvYGAlLbWh3+jQwBp3MWloe+FUpGGQbyiuRzoBYRwyib26FbMbjlg NnX5XQYftG4WzTeXgB8nIQVXP9WgCXFLb4mTwTbKpLZdS6lc4cdVy/bxkeQgwomgjLzbwJab1ThX+ mQIoz4UGDwbgNHHkhtyFaXJ430Y8UCBUFZ5f3ehMizYZtfCdl6Vc1Kbg9seTy6S9iLgxmTmWrdF4s 9q6Kls4vtOXQPSNmfwkW9PwvAdgIgTJcl+4W2yyLYxDDh0D+xQog5dGCwj+q68x5OR+Aqbta/0yeG CYqIn8YRERwlr6FmseNRqw==; Received: from [87.69.77.57] (helo=home-c4e4a596f7) by fencepost.gnu.org with esmtpsa (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from <eliz@HIDDEN>) id 1oyHy3-0003mD-HJ; Thu, 24 Nov 2022 14:33:03 -0500 Date: Thu, 24 Nov 2022 21:33:24 +0200 Message-Id: <83wn7kuozf.fsf@HIDDEN> From: Eli Zaretskii <eliz@HIDDEN> To: Stefan Kangas <stefankangas@HIDDEN> In-Reply-To: <CADwFkm=z8STfz5abAUc-Y72z-cH_XwDxvKwi9qGWDnhTcxxOEw@HIDDEN> (message from Stefan Kangas on Thu, 24 Nov 2022 11:29:32 -0800) Subject: Re: bug#59057: Emacs 29. Byte compiler sometimes forgets about a defvar. References: <Y2avmeQhiTntL1q2@ACM> <jwvsfiux6so.fsf-monnier+emacs@HIDDEN> <Y2lohC66d/uSi5oz@ACM> <jwv5yfqv4fx.fsf-monnier+emacs@HIDDEN> <Y2ut6a7AONZYR7Sy@ACM> <jwvsfisqakd.fsf-monnier+emacs@HIDDEN> <CADwFkm=z8STfz5abAUc-Y72z-cH_XwDxvKwi9qGWDnhTcxxOEw@HIDDEN> X-Spam-Score: -2.3 (--) X-Debbugs-Envelope-To: 59057 Cc: acm@HIDDEN, monnier@HIDDEN, 59057 <at> debbugs.gnu.org X-BeenThere: debbugs-submit <at> debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: <debbugs-submit.debbugs.gnu.org> List-Unsubscribe: <https://debbugs.gnu.org/cgi-bin/mailman/options/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=unsubscribe> List-Archive: <https://debbugs.gnu.org/cgi-bin/mailman/private/debbugs-submit/> List-Post: <mailto:debbugs-submit <at> debbugs.gnu.org> List-Help: <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=help> List-Subscribe: <https://debbugs.gnu.org/cgi-bin/mailman/listinfo/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=subscribe> Errors-To: debbugs-submit-bounces <at> debbugs.gnu.org Sender: "Debbugs-submit" <debbugs-submit-bounces <at> debbugs.gnu.org> X-Spam-Score: -3.3 (---) > Cc: Alan Mackenzie <acm@HIDDEN>, 59057 <at> debbugs.gnu.org > From: Stefan Kangas <stefankangas@HIDDEN> > Date: Thu, 24 Nov 2022 11:29:32 -0800 > > Stefan Monnier <monnier@HIDDEN> writes: > > >> The basic problem is that defvar is a dog's breakfast of a function. In > >> fact, it's two distinct functions sharing a name. These two functions > >> have little else to do with eachother. > > > > Yup. > > > >> And defvar appears to be the only function in Emacs where supplying nil > >> as an &optional argument has an effect different from omitting it. This > >> is bad for anybody trying to learn Emacs Lisp. > > > > Not the only one, sadly (`declare-function` comes to mind :-)), but yes, > > it's unusual. > > I guess defvar will have to stay as it is. But would it make sense to > add a new `declare-variable' function, and then document the form > > (defvar <foo>) > > to be considered deprecated? It makes no sense to me to deprecate (defvar FOO). There are only disadvantages down that path (massive annoyance or breakage of third-party code, if nothing else). Please don't.
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Subject: Re: bug#59057: Emacs 29. Byte compiler sometimes forgets about a
defvar.
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Stefan Monnier <monnier@HIDDEN> writes:
>> The basic problem is that defvar is a dog's breakfast of a function. In
>> fact, it's two distinct functions sharing a name. These two functions
>> have little else to do with eachother.
>
> Yup.
>
>> And defvar appears to be the only function in Emacs where supplying nil
>> as an &optional argument has an effect different from omitting it. This
>> is bad for anybody trying to learn Emacs Lisp.
>
> Not the only one, sadly (`declare-function` comes to mind :-)), but yes,
> it's unusual.
I guess defvar will have to stay as it is. But would it make sense to
add a new `declare-variable' function, and then document the form
(defvar <foo>)
to be considered deprecated?
bug-gnu-emacs@HIDDEN:bug#59057; Package emacs.
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From: Stefan Monnier <monnier@HIDDEN>
To: Alan Mackenzie <acm@HIDDEN>
Subject: Re: bug#59057: Emacs 29. Byte compiler sometimes forgets about a
defvar.
In-Reply-To: <Y2ut6a7AONZYR7Sy@ACM> (Alan Mackenzie's message of "Wed, 9 Nov
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> The basic problem is that defvar is a dog's breakfast of a function. In
> fact, it's two distinct functions sharing a name. These two functions
> have little else to do with eachother.
Yup.
> And defvar appears to be the only function in Emacs where supplying nil
> as an &optional argument has an effect different from omitting it. This
> is bad for anybody trying to learn Emacs Lisp.
Not the only one, sadly (`declare-function` comes to mind :-)), but yes,
it's unusual.
Stefan
bug-gnu-emacs@HIDDEN:bug#59057; Package emacs.
Full text available.Received: (at 59057) by debbugs.gnu.org; 9 Nov 2022 13:41:11 +0000 From debbugs-submit-bounces <at> debbugs.gnu.org Wed Nov 09 08:41:10 2022 Received: from localhost ([127.0.0.1]:39315 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <debbugs-submit-bounces <at> debbugs.gnu.org>) id 1oslKI-0003GS-JU for submit <at> debbugs.gnu.org; Wed, 09 Nov 2022 08:41:10 -0500 Received: from mx3.muc.de ([193.149.48.5]:54324) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <acm@HIDDEN>) id 1oslKE-0003Fg-1K for 59057 <at> debbugs.gnu.org; Wed, 09 Nov 2022 08:41:09 -0500 Received: (qmail 77014 invoked by uid 3782); 9 Nov 2022 14:40:59 +0100 Received: from acm.muc.de (p4fe1582d.dip0.t-ipconnect.de [79.225.88.45]) (using STARTTLS) by colin.muc.de (tmda-ofmipd) with ESMTP; Wed, 09 Nov 2022 14:40:59 +0100 Received: (qmail 6919 invoked by uid 1000); 9 Nov 2022 13:40:57 -0000 Date: Wed, 9 Nov 2022 13:40:57 +0000 To: Stefan Monnier <monnier@HIDDEN> Subject: Re: bug#59057: Emacs 29. Byte compiler sometimes forgets about a defvar. Message-ID: <Y2ut6a7AONZYR7Sy@ACM> References: <Y2avmeQhiTntL1q2@ACM> <jwvsfiux6so.fsf-monnier+emacs@HIDDEN> <Y2lohC66d/uSi5oz@ACM> <jwv5yfqv4fx.fsf-monnier+emacs@HIDDEN> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <jwv5yfqv4fx.fsf-monnier+emacs@HIDDEN> X-Submission-Agent: TMDA/1.3.x (Ph3nix) From: Alan Mackenzie <acm@HIDDEN> X-Primary-Address: acm@HIDDEN X-Spam-Score: 0.0 (/) X-Debbugs-Envelope-To: 59057 Cc: 59057 <at> debbugs.gnu.org X-BeenThere: debbugs-submit <at> debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: <debbugs-submit.debbugs.gnu.org> List-Unsubscribe: <https://debbugs.gnu.org/cgi-bin/mailman/options/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=unsubscribe> List-Archive: <https://debbugs.gnu.org/cgi-bin/mailman/private/debbugs-submit/> List-Post: <mailto:debbugs-submit <at> debbugs.gnu.org> List-Help: <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=help> List-Subscribe: <https://debbugs.gnu.org/cgi-bin/mailman/listinfo/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=subscribe> Errors-To: debbugs-submit-bounces <at> debbugs.gnu.org Sender: "Debbugs-submit" <debbugs-submit-bounces <at> debbugs.gnu.org> X-Spam-Score: -1.0 (-) Hello, Stefan. On Mon, Nov 07, 2022 at 16:31:32 -0500, Stefan Monnier wrote: > >> (defvar VAR) does not "create a variable". > > According to both its doc string and the Elisp manual it does. > BTW, what I'm describing is how things have worked in `lexical-binding` > since Emacs-24, basically. A few corner cases didn't quite obey it > (and I'm sure there are still a few remaining ones), but by and large > this is how it has worked for the last 10 years. OK, I see that now, having checked git logs and git blame. There was a bug report in 2018 about the documentation, which Noam Postavsky fixed. The basic problem is that defvar is a dog's breakfast of a function. In fact, it's two distinct functions sharing a name. These two functions have little else to do with eachother. And defvar appears to be the only function in Emacs where supplying nil as an &optional argument has an effect different from omitting it. This is bad for anybody trying to learn Emacs Lisp. Because defvar isn't a single function, it's impossible to document it coherently without explicitly saying it's two functions. I doubt the powers that be would countenance such explicitness. So the documentation will continue to be confusing, and people like me will continue to lose time sorting out what this hybrid function does. I will alter the code in CC Mode which gave rise to this bug report. > Stefan -- Alan Mackenzie (Nuremberg, Germany).
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From: Stefan Monnier <monnier@HIDDEN>
To: Alan Mackenzie <acm@HIDDEN>
Subject: Re: bug#59057: Emacs 29. Byte compiler sometimes forgets about a
defvar.
In-Reply-To: <Y2o2/UJeAShsSP+8@ACM> (Alan Mackenzie's message of "Tue, 8 Nov
2022 11:01:17 +0000")
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> The recently introduced special handling of defvar without a value is
> not welcome.
`defvar` without a value has been treated specially (more specifically
as a pure compiler-directive with no run-time effect) since at least
Emacs-19.34, so I'm not sure "recently" can be applied here.
> Why should anybody want a dynamic variable later to be
> a lexically scoped variable?.
E.g. for historical reasons `calendar.el` needs to bind dynamically the
variable `date` around some calls to `eval` and to `run-hooks` because
the code evaluated therein has been defined and documented for may years
before to have access to important info via those dynbound vars.
Yet, we don't want `date` to be globally declared as being
always dynbound just because of that package's mishap, do we?
Similar situations affect other innocent-looking vars in other packages.
Stefan
bug-gnu-emacs@HIDDEN:bug#59057; Package emacs.
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Subject: Re: bug#59057: Emacs 29. Byte compiler sometimes forgets about a
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Hello, Stefan.
On Mon, Nov 07, 2022 at 16:29:15 -0500, Stefan Monnier wrote:
> >> (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.
The entry in the Elisp manual starts off:
This special form defines SYMBOL as a variable. Note that SYMBOL
is not evaluated; the symbol to be defined should appear explicitly
in the `defvar' form. The variable is marked as "special", meaning
that it should always be dynamically bound (see Variable
Scoping).
"This special form defines SYMBOL as a variable.". There are no ifs,
buts, whens, or whenevers in that sentence. This is, at best, somewhat
confusing.
Note also: "... that it should ALWAYS be dynamically bound ...".
I suppose you're now going to say that "defining" a variable is
different from "creating" it. And that you're going to say "always"
doesn't mean always.
From defvar's doc string:
The `defvar' form also declares the variable as "special",
so that it is ALWAYS dynamically bound even if `lexical-binding' is t.
Here, again, you're going to say that "always" only means "sometimes", I
think.
> >> 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.
Why? What's the use case? This, again, is contradictory: a defvar with
a value has global effect, but without a value has only lexical scope.
This doesn't make sense. Why should dynamically bound variables have
lexical scope? Could it be the enthusiasm for lexical binding has burst
beyond its natural limits?
> >> 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`.
I think programmers just want defvar to behave sensibly and
consistently, and in accordance with the documentation. The recently
introduced special handling of defvar without a value is not welcome.
Why should anybody want a dynamic variable later to be a lexically
scoped variable?.
> Why put the (defvar ,var) within the `when` if not to limit
> its scope?
To limit when it will create the variable, according to the value of the
enclosing `if' form. Just like if you do a (setq my-global some-value),
that has effect outside of the lexical scope.
In my test program, l-s-p is created with a dynamic binding, but later
on it got a confusing warning about it being unused as a lexically bound
variable. Nobody wants this, surely?
> Stefan
--
Alan Mackenzie (Nuremberg, Germany).
bug-gnu-emacs@HIDDEN:bug#59057; Package emacs.
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From: Stefan Monnier <monnier@HIDDEN>
To: Alan Mackenzie <acm@HIDDEN>
Subject: Re: bug#59057: Emacs 29. Byte compiler sometimes forgets about a
defvar.
In-Reply-To: <Y2lohC66d/uSi5oz@ACM> (Alan Mackenzie's message of "Mon, 7 Nov
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>> (defvar VAR) does not "create a variable".
> According to both its doc string and the Elisp manual it does.
BTW, what I'm describing is how things have worked in `lexical-binding`
since Emacs-24, basically. A few corner cases didn't quite obey it
(and I'm sure there are still a few remaining ones), but by and large
this is how it has worked for the last 10 years.
Stefan
bug-gnu-emacs@HIDDEN:bug#59057; Package emacs.
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From: Stefan Monnier <monnier@HIDDEN>
To: Alan Mackenzie <acm@HIDDEN>
Subject: Re: bug#59057: Emacs 29. Byte compiler sometimes forgets about a
defvar.
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>> (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
bug-gnu-emacs@HIDDEN:bug#59057; Package emacs.
Full text available.Received: (at 59057) by debbugs.gnu.org; 7 Nov 2022 20:20:31 +0000 From debbugs-submit-bounces <at> debbugs.gnu.org Mon Nov 07 15:20:30 2022 Received: from localhost ([127.0.0.1]:35494 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <debbugs-submit-bounces <at> debbugs.gnu.org>) id 1os8be-0006x5-HR for submit <at> debbugs.gnu.org; Mon, 07 Nov 2022 15:20:30 -0500 Received: from mx3.muc.de ([193.149.48.5]:37949) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <acm@HIDDEN>) id 1os8bc-0006wn-S5 for 59057 <at> debbugs.gnu.org; Mon, 07 Nov 2022 15:20:29 -0500 Received: (qmail 21687 invoked by uid 3782); 7 Nov 2022 21:20:20 +0100 Received: from acm.muc.de (p4fe15967.dip0.t-ipconnect.de [79.225.89.103]) (using STARTTLS) by colin.muc.de (tmda-ofmipd) with ESMTP; Mon, 07 Nov 2022 21:20:20 +0100 Received: (qmail 17820 invoked by uid 1000); 7 Nov 2022 20:20:20 -0000 Date: Mon, 7 Nov 2022 20:20:20 +0000 To: Stefan Monnier <monnier@HIDDEN> Subject: Re: bug#59057: Emacs 29. Byte compiler sometimes forgets about a defvar. Message-ID: <Y2lohC66d/uSi5oz@ACM> References: <Y2avmeQhiTntL1q2@ACM> <jwvsfiux6so.fsf-monnier+emacs@HIDDEN> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <jwvsfiux6so.fsf-monnier+emacs@HIDDEN> X-Submission-Agent: TMDA/1.3.x (Ph3nix) From: Alan Mackenzie <acm@HIDDEN> X-Primary-Address: acm@HIDDEN X-Spam-Score: 0.0 (/) X-Debbugs-Envelope-To: 59057 Cc: 59057 <at> debbugs.gnu.org X-BeenThere: debbugs-submit <at> debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: <debbugs-submit.debbugs.gnu.org> List-Unsubscribe: <https://debbugs.gnu.org/cgi-bin/mailman/options/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=unsubscribe> List-Archive: <https://debbugs.gnu.org/cgi-bin/mailman/private/debbugs-submit/> List-Post: <mailto:debbugs-submit <at> debbugs.gnu.org> List-Help: <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=help> List-Subscribe: <https://debbugs.gnu.org/cgi-bin/mailman/listinfo/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=subscribe> Errors-To: debbugs-submit-bounces <at> debbugs.gnu.org Sender: "Debbugs-submit" <debbugs-submit-bounces <at> debbugs.gnu.org> X-Spam-Score: -1.0 (-) Hello, Stefan. On Mon, Nov 07, 2022 at 08:07:28 -0500, Stefan Monnier wrote: > > (defmacro acm-defvar (var) > > `(eval-when-compile > > ; (when (version-check) > > (defvar ,var) > > (setq ,var emacs-major-version) > > ; ) > > )) > (defvar VAR) does not "create a variable". According to both its doc string and the Elisp manual it does. > 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. The manual says that, with defun, "The variable is marked as "special", meaning that it should always be dynamically bound.". In my example program, l-s-p was created with defvar, yet later in the example, the compiler bound it lexically. There is a bug here, either in the code or in the documentation. > Before the commit you mentioned, the above (defvar ,var) would sometimes > incorrectly escape its `when` subexpression and affect subsequent code, > which is why in the past the presence of `when` did not make much > difference whereas it now does. What was incorrect about this "escaping"? It would appear to match the elisp manual, and its effect on subsequent code would be positive, rather than negative, surely? Why does the `when' now prevent l-s-p being marked as global? In particular, why is it not entered into the list byte-compile-bound-variables? > Note also that for the same reason the above should arguably never work > at all since the effect of (defvar ,var) should not escape the > `eval-when-compile` subexpression. Why shouldn't it? The defvar is evaluated at compilation time, should create l-s-p, and should mark it as dynamically bound. It does in fact create the variable (see `message' output), but doesn't mark it as dynamic when the evaluation is inside a conditional. > A lot of code relies on this misbehavior, tho, so we still support it. By what criterion is it "misbehaviour"? It would appear to be what defvar's doc string and manual entry say. > 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. > > This bug doesn't occur on Emacs 28. > > I have a feeling it was introduced into Emacs 29 very recently. > The Emacs-28 behavior was a misbehavior, which got fixed accidentally > recently :-) I feel I'm beginning to get repetitive here. ;-) But what was incorrect about the Emacs 28 behaviour? The current behaviour causes confusing, incorrect warning messages to get output. It cost me many hours of labour till I finally found out the warnings came from a change in the byte compiler. Surely either the code or the documentation should be fixed, so that other people don't have to go through the same. > Stefan -- Alan Mackenzie (Nuremberg, Germany).
bug-gnu-emacs@HIDDEN:bug#59057; Package emacs.
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From: Stefan Monnier <monnier@HIDDEN>
To: Alan Mackenzie <acm@HIDDEN>
Subject: Re: bug#59057: Emacs 29. Byte compiler sometimes forgets about a
defvar.
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> (defmacro acm-defvar (var)
> `(eval-when-compile
> ; (when (version-check)
> (defvar ,var)
> (setq ,var emacs-major-version)
> ; )
> ))
(defvar VAR) does not "create a variable". It just "locally" declares
that this identifier should use dynamic scoping when binding a variable.
Before the commit you mentioned, the above (defvar ,var) would sometimes
incorrectly escape its `when` subexpression and affect subsequent code,
which is why in the past the presence of `when` did not make much
difference whereas it now does.
Note also that for the same reason the above should arguably never work
at all since the effect of (defvar ,var) should not escape the
`eval-when-compile` subexpression. A lot of code relies on this
misbehavior, tho, so we still support it. 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)))))
> This bug doesn't occur on Emacs 28.
> I have a feeling it was introduced into Emacs 29 very recently.
The Emacs-28 behavior was a misbehavior, which got fixed accidentally
recently :-)
Stefan
bug-gnu-emacs@HIDDEN:bug#59057; Package emacs.
Full text available.
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Date: Sat, 5 Nov 2022 18:46:49 +0000
To: bug-gnu-emacs@HIDDEN
Subject: Emacs 29. Byte compiler sometimes forgets about a defvar.
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Hello, Emacs.
With an up to date master version, start emacs -Q.
(i) Visit bug-compile-defvar.el, which looks like this:
#########################################################################
;; -*- lexical-binding: t -*-
(eval-and-compile
(defun version-check ()
(>= emacs-major-version 28)))
(defmacro acm-defvar (var)
`(eval-when-compile
; (when (version-check)
(defvar ,var)
(setq ,var emacs-major-version)
; )
))
(acm-defvar l-s-p)
(eval-when-compile
(message
"\nl-s-p is %sin byte-compile-bound-variables"
(if (memq 'l-s-p byte-compile-bound-variables)
"" "not "))
(message
"l-s-p is %sbound"
(if (boundp 'l-s-p) "" "not ")))
(defun acm-bind-l-s-p ()
(let ((l-s-p emacs-major-version))
(message "Nothing much\n")))
#########################################################################
The idea here is that the macro acm-defvar itself calls defvar, creating
a variable.
(ii) Do M-x byte-compile-file RET ~/bug-compile-defvar.el.
(iii) Note that this works properly, giving out the two messages, the
first of which confirms that the new variable l-s-p has been entered
into the list byte-compile-bound-variables.
(iv) Edit the buffer, removing both single semicolon comment markers, and
save the file.
(v) Do M-x byte-compile-file RET ~/bug-compile-defvar.el again.
(vi) Note that now the new variable is NOT in
byte-compile-bound-variables. This is a bug.
(vii) Note also that there is a spurious compiler warning about l-s-p
being an unused lexical variable in function acm-bind-l-s-p. This is
also a bug.
This bug doesn't occur on Emacs 28. I have a feeling it was introduced
into Emacs 29 very recently.
--
Alan Mackenzie (Nuremberg, Germany).
Alan Mackenzie <acm@HIDDEN>:bug-gnu-emacs@HIDDEN.
Full text available.bug-gnu-emacs@HIDDEN:bug#59057; Package emacs.
Full text available.
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