From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED.blaine.gmane.org!not-for-mail From: Phil Sainty Newsgroups: gmane.emacs.bugs Subject: bug#38173: describe-variable: Also tell user *where* variable was changed Date: Thu, 14 Nov 2019 11:56:39 +1300 Message-ID: References: <87pnhxyjxp.8.fsf@jidanni.org> <878solyfr2.8.fsf@jidanni.org> <9a2ece93c5474cdd68e6f7253408dba8@webmail.orcon.net.nz> <87pnhwsmii.5.fsf@jidanni.org> <69ffb0e3-4616-4147-4888-cc2889694bb5@orcon.net.nz> <87v9rnx1bi.5.fsf@jidanni.org> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Injection-Info: blaine.gmane.org; posting-host="blaine.gmane.org:195.159.176.226"; logging-data="69510"; mail-complaints-to="usenet@blaine.gmane.org" User-Agent: Orcon Webmail Cc: Katsumi Yamaoka , 38173@debbugs.gnu.org To: =?UTF-8?Q?=E7=A9=8D=E4=B8=B9=E5=B0=BC?= Dan Jacobson Original-X-From: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane.org@gnu.org Thu Nov 14 00:11:03 2019 Return-path: Envelope-to: geb-bug-gnu-emacs@m.gmane.org Original-Received: from lists.gnu.org ([209.51.188.17]) by blaine.gmane.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1iV1mx-000HwR-6w for geb-bug-gnu-emacs@m.gmane.org; Thu, 14 Nov 2019 00:11:03 +0100 Original-Received: from localhost ([::1]:52214 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iV1mv-00025b-WC for geb-bug-gnu-emacs@m.gmane.org; Wed, 13 Nov 2019 18:11:02 -0500 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:37978) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iV1ZP-0005Vl-Ih for bug-gnu-emacs@gnu.org; Wed, 13 Nov 2019 17:57:05 -0500 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iV1ZO-0004NA-IM for bug-gnu-emacs@gnu.org; Wed, 13 Nov 2019 17:57:03 -0500 Original-Received: from debbugs.gnu.org ([209.51.188.43]:51616) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1iV1ZO-0004Mx-FB for bug-gnu-emacs@gnu.org; Wed, 13 Nov 2019 17:57:02 -0500 Original-Received: from Debian-debbugs by debbugs.gnu.org with local (Exim 4.84_2) (envelope-from ) id 1iV1ZO-00053d-B1 for bug-gnu-emacs@gnu.org; Wed, 13 Nov 2019 17:57:02 -0500 X-Loop: help-debbugs@gnu.org Resent-From: Phil Sainty Original-Sender: "Debbugs-submit" Resent-CC: bug-gnu-emacs@gnu.org Resent-Date: Wed, 13 Nov 2019 22:57:02 +0000 Resent-Message-ID: Resent-Sender: help-debbugs@gnu.org X-GNU-PR-Message: followup 38173 X-GNU-PR-Package: emacs Original-Received: via spool by 38173-submit@debbugs.gnu.org id=B38173.157368580719421 (code B ref 38173); Wed, 13 Nov 2019 22:57:02 +0000 Original-Received: (at 38173) by debbugs.gnu.org; 13 Nov 2019 22:56:47 +0000 Original-Received: from localhost ([127.0.0.1]:60437 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1iV1Z9-00053B-8F for submit@debbugs.gnu.org; Wed, 13 Nov 2019 17:56:47 -0500 Original-Received: from smtp-4.orcon.net.nz ([60.234.4.59]:53845) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1iV1Z6-000531-RE for 38173@debbugs.gnu.org; Wed, 13 Nov 2019 17:56:46 -0500 Original-Received: from [10.253.37.70] (port=39003 helo=webmail.orcon.net.nz) by smtp-4.orcon.net.nz with esmtpa (Exim 4.90_1) (envelope-from ) id 1iV1Z1-0002og-M7; Thu, 14 Nov 2019 11:56:39 +1300 Original-Received: from wlgwil-nat-office.catalyst.net.nz ([202.78.240.7]) via [10.253.37.253] by webmail.orcon.net.nz with HTTP (HTTP/1.1 POST); Thu, 14 Nov 2019 11:56:39 +1300 In-Reply-To: <87v9rnx1bi.5.fsf@jidanni.org> X-Sender: psainty@orcon.net.nz X-GeoIP: -- X-Spam_score: -2.9 X-Spam_score_int: -28 X-Spam_bar: -- X-BeenThere: debbugs-submit@debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.51.188.43 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.org@gnu.org Original-Sender: "bug-gnu-emacs" Xref: news.gmane.org gmane.emacs.bugs:171515 Archived-At: On 2019-11-14 04:06, 積丹尼 Dan Jacobson wrote: > PS> It still might not have the effect you wanted, though -- it's > PS> possible to change the apparent / user-facing value of some > variables > PS> without changing the *actual* value of the variable at all. This > is > PS> because of the internal structure of lists in lisp... > > Sounds like a security / coverup risk. Maybe with the expensive > global-variable-tracking turned on, describe-variable could double > check > for such tampering upon looking up a variable. It's not "tampering". It's just the fundamental nature of lists in lisp (all dialects of lisp, AFAIK). You're only seeing it as a concern in the context of a feature which doesn't exist. It would, I think, be *dramatically* (perhaps prohibitively) more expensive to perform that kind of checking. This could no longer be done by the variable-watcher mechanism. In principle, every time ANY lisp object was modified at all, Emacs would need to check to see whether the object (pre- modification) was a value -- or a nested sub-component, to any arbitrary depth, of a value -- of ANY variable in the system, so that it could register that the change affected the user-facing value of that variable. -Phil