From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Alan Mackenzie Newsgroups: gmane.emacs.bugs Subject: bug#65051: internal_equal manipulates symbols with position without checking symbols-with-pos-enabled. Date: Sat, 5 Aug 2023 13:04:07 +0000 Message-ID: References: <83leeqvpx8.fsf@gnu.org> <83h6pevnd0.fsf@gnu.org> <838raqvg91.fsf@gnu.org> <83r0ohsqmp.fsf@gnu.org> <83leepsn4t.fsf@gnu.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="38389"; mail-complaints-to="usenet@ciao.gmane.io" Cc: 65051@debbugs.gnu.org, acm@muc.de, monnier@iro.umontreal.ca To: Eli Zaretskii Original-X-From: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane-mx.org@gnu.org Sat Aug 05 15:05:19 2023 Return-path: Envelope-to: geb-bug-gnu-emacs@m.gmane-mx.org Original-Received: from lists.gnu.org ([209.51.188.17]) by ciao.gmane.io with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1qSGy7-0009hu-71 for geb-bug-gnu-emacs@m.gmane-mx.org; Sat, 05 Aug 2023 15:05:19 +0200 Original-Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qSGxt-00080F-1k; Sat, 05 Aug 2023 09:05:05 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qSGxq-000805-Lf for bug-gnu-emacs@gnu.org; Sat, 05 Aug 2023 09:05:02 -0400 Original-Received: from debbugs.gnu.org ([2001:470:142:5::43]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1qSGxq-0000F7-D1 for bug-gnu-emacs@gnu.org; Sat, 05 Aug 2023 09:05:02 -0400 Original-Received: from Debian-debbugs by debbugs.gnu.org with local (Exim 4.84_2) (envelope-from ) id 1qSGxq-0005eG-7c for bug-gnu-emacs@gnu.org; Sat, 05 Aug 2023 09:05:02 -0400 X-Loop: help-debbugs@gnu.org Resent-From: Alan Mackenzie Original-Sender: "Debbugs-submit" Resent-CC: bug-gnu-emacs@gnu.org Resent-Date: Sat, 05 Aug 2023 13:05:02 +0000 Resent-Message-ID: Resent-Sender: help-debbugs@gnu.org X-GNU-PR-Message: followup 65051 X-GNU-PR-Package: emacs Original-Received: via spool by 65051-submit@debbugs.gnu.org id=B65051.169124066021650 (code B ref 65051); Sat, 05 Aug 2023 13:05:02 +0000 Original-Received: (at 65051) by debbugs.gnu.org; 5 Aug 2023 13:04:20 +0000 Original-Received: from localhost ([127.0.0.1]:56072 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1qSGxA-0005d7-3r for submit@debbugs.gnu.org; Sat, 05 Aug 2023 09:04:20 -0400 Original-Received: from mx3.muc.de ([193.149.48.5]:39087) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1qSGx4-0005cl-M8 for 65051@debbugs.gnu.org; Sat, 05 Aug 2023 09:04:18 -0400 Original-Received: (qmail 99035 invoked by uid 3782); 5 Aug 2023 15:04:08 +0200 Original-Received: from acm.muc.de (p4fe15973.dip0.t-ipconnect.de [79.225.89.115]) (using STARTTLS) by colin.muc.de (tmda-ofmipd) with ESMTP; Sat, 05 Aug 2023 15:04:08 +0200 Original-Received: (qmail 29141 invoked by uid 1000); 5 Aug 2023 13:04:07 -0000 Content-Disposition: inline In-Reply-To: <83leepsn4t.fsf@gnu.org> X-Submission-Agent: TMDA/1.3.x (Ph3nix) X-Primary-Address: acm@muc.de X-BeenThere: debbugs-submit@debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list X-BeenThere: bug-gnu-emacs@gnu.org List-Id: "Bug reports for GNU Emacs, the Swiss army knife of text editors" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane-mx.org@gnu.org Original-Sender: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane-mx.org@gnu.org Xref: news.gmane.io gmane.emacs.bugs:266779 Archived-At: Hello, Eli. On Sat, Aug 05, 2023 at 15:13:22 +0300, Eli Zaretskii wrote: > > Date: Sat, 5 Aug 2023 11:52:52 +0000 > > Cc: 65051@debbugs.gnu.org, Stefan Monnier , > > acm@muc.de > > From: Alan Mackenzie > > Hello, Eli. > > On Sat, Aug 05, 2023 at 13:57:50 +0300, Eli Zaretskii wrote: > > > > Date: Sat, 5 Aug 2023 10:45:37 +0000 > > > > Cc: 65051@debbugs.gnu.org, acm@muc.de > > > > From: Alan Mackenzie > > [ .... ] > > > > > So we can have two different copies of #, such that > > > > > their hex values are different? Isn't that a bug? why don't we > > > > > conflate such identical symbols? > > > > No, it's not a bug, anymore than having two `equal' copies of '(a b c) > > > > would be a bug. > > > But with symbols we store them in obarray, and obarray ought to find > > > the existing slot for # and reuse it, rather than > > > create a new slot? > > No, only the bare symbol is in the obarray. The symbol with position > > itself is a pseudovector, with contents (i) a bare symbol (a Lisp_Object > > "pointing at" the obarray) and (ii) the unsigned integer position. > Please document this factoid in the ELisp manual, I think it's very > important, and having it undocumented is a Bad Thing. DONE. The change is near the top of the following patch, amended from the previous version. diff --git a/doc/lispref/symbols.texi b/doc/lispref/symbols.texi index 34db0caf3a8..a828d303c04 100644 --- a/doc/lispref/symbols.texi +++ b/doc/lispref/symbols.texi @@ -784,9 +784,15 @@ Symbols with Position @cindex bare symbol A @dfn{symbol with position} is a symbol, the @dfn{bare symbol}, together with an unsigned integer called the @dfn{position}. These -objects are intended for use by the byte compiler, which records in -them the position of each symbol occurrence and uses those positions -in warning and error messages. +objects are stored internally much like vectors, and don't themselves +have entries in the obarray (though their bare symbols do; +@pxref{Creating Symbols}). + +Symbols with position are for the use of the byte compiler, which +records in them the position of each symbol occurrence and uses those +positions in warning and error messages. They shouldn't normally be +used otherwise. Doing so can cause unexpected results with basic +Emacs functions such as @code{eq} and @code{equal}. The printed representation of a symbol with position uses the hash notation outlined in @ref{Printed Representation}. It looks like @@ -798,11 +804,20 @@ Symbols with Position For most purposes, when the flag variable @code{symbols-with-pos-enabled} is non-@code{nil}, symbols with -positions behave just as bare symbols do. For example, @samp{(eq -# foo)} has a value @code{t} when that variable -is set (but @code{nil} when it isn't set). Most of the time in Emacs this -variable is @code{nil}, but the byte compiler binds it to @code{t} -when it runs. +positions behave just as their bare symbols would. For example, +@samp{(eq # foo)} has a value @code{t} when the +variable is set; likewise, @code{equal} will treat a symbol with +position argument as its bare symbol. + +When @code{symbols-with-pos-enabled} is @code{nil}, any symbols with +position continue to exist, but do not behave as symbols, or have the +other useful properties outlined in the previous paragraph. @code{eq} +returns @code{t} when given identical arguments, and @code{equal} +returns @code{t} when given arguments with @code{equal} components. + +Most of the time in Emacs @code{symbols-with-pos-enabled} is +@code{nil}, but the byte compiler and the native compiler bind it to +@code{t} when they run. Typically, symbols with position are created by the byte compiler calling the reader function @code{read-positioning-symbols} @@ -820,7 +835,7 @@ Symbols with Position a symbol with position, ignoring the position. @end defvar -@defun symbol-with-pos-p symbol. +@defun symbol-with-pos-p symbol This function returns @code{t} if @var{symbol} is a symbol with position, @code{nil} otherwise. @end defun -- Alan Mackenzie (Nuremberg, Germany).