From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Po Lu via "Bug reports for GNU Emacs, the Swiss army knife of text editors" Newsgroups: gmane.emacs.bugs Subject: bug#65491: [PATCH] Improve performance allocating vectors Date: Mon, 18 Sep 2023 10:19:09 +0800 Message-ID: <87jzsoxlya.fsf@yahoo.com> References: <6B2EDD07-AAEB-40E8-B369-F634296BD3D9@gmail.com> <83v8cagkqv.fsf@gnu.org> <83ttrugkj2.fsf@gnu.org> <83sf7egitx.fsf@gnu.org> <871qexzelk.fsf@yahoo.com> Reply-To: Po Lu Mime-Version: 1.0 Content-Type: text/plain Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="10550"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Gnus/5.13 (Gnus v5.13) Cc: 65491@debbugs.gnu.org, Mattias =?UTF-8?Q?Engdeg=C3=A5rd?= , Eli Zaretskii To: Stefan Monnier Original-X-From: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane-mx.org@gnu.org Mon Sep 18 04:20:28 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 1qi3sA-0002Pm-N9 for geb-bug-gnu-emacs@m.gmane-mx.org; 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Hermes SMTP Server) with ESMTPA ID 3d33fddaff326e8c68172b91936e1586; Mon, 18 Sep 2023 02:19:14 +0000 (UTC) In-Reply-To: (Stefan Monnier's message of "Sun, 17 Sep 2023 13:02:15 -0400") X-Mailer: WebService/1.1.21797 mail.backend.jedi.jws.acl:role.jedi.acl.token.atz.jws.hermes.yahoo 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:270734 Archived-At: Stefan Monnier writes: > Even converting them back to their original pointer (which is what we do > with tag/untag pairs) is documented to be well-defined if you compile > using GCC. Only if the consequent pointer designates the same object as the initial pointer (of which I see no scrutable definition within GCC's documentation.) But in practice, this doesn't matter, or so I thought. > In contrast the pointer arithmetic on NULL pointers appears to be > something which compilers have started to (ab)use as an assumption for > their optimizations. Hence the need to update our code. Hmm? Where in this thread was that fact established? Thanks.