From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED!not-for-mail From: Paul Eggert Newsgroups: gmane.emacs.bugs Subject: bug#31750: simplify and tune Emacs stack-related allocation Date: Sun, 10 Jun 2018 09:12:33 -0700 Organization: UCLA Computer Science Department Message-ID: References: <9aeda5fe-dc7c-30d5-39df-2942410a672b@cs.ucla.edu> <87po0zz5bd.fsf@gmail.com> <14685fe0-39b9-deb6-6960-0e9572c4357c@cs.ucla.edu> <837en6sms4.fsf@gnu.org> NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable X-Trace: blaine.gmane.org 1528647073 27670 195.159.176.226 (10 Jun 2018 16:11:13 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Sun, 10 Jun 2018 16:11:13 +0000 (UTC) User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0 Cc: npostavs@gmail.com, 31750@debbugs.gnu.org To: Eli Zaretskii Original-X-From: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane.org@gnu.org Sun Jun 10 18:11:08 2018 Return-path: Envelope-to: geb-bug-gnu-emacs@m.gmane.org Original-Received: from lists.gnu.org ([208.118.235.17]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1fS2vp-00070N-VP for geb-bug-gnu-emacs@m.gmane.org; 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Sun, 10 Jun 2018 12:13:02 -0400 X-Loop: help-debbugs@gnu.org Resent-From: Paul Eggert Original-Sender: "Debbugs-submit" Resent-CC: bug-gnu-emacs@gnu.org Resent-Date: Sun, 10 Jun 2018 16:13:02 +0000 Resent-Message-ID: Resent-Sender: help-debbugs@gnu.org X-GNU-PR-Message: followup 31750 X-GNU-PR-Package: emacs X-GNU-PR-Keywords: patch Original-Received: via spool by 31750-submit@debbugs.gnu.org id=B31750.152864716424047 (code B ref 31750); Sun, 10 Jun 2018 16:13:02 +0000 Original-Received: (at 31750) by debbugs.gnu.org; 10 Jun 2018 16:12:44 +0000 Original-Received: from localhost ([127.0.0.1]:42497 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1fS2xQ-0006Fn-00 for submit@debbugs.gnu.org; Sun, 10 Jun 2018 12:12:44 -0400 Original-Received: from zimbra.cs.ucla.edu ([131.179.128.68]:55242) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1fS2xN-0006FX-M9 for 31750@debbugs.gnu.org; Sun, 10 Jun 2018 12:12:42 -0400 Original-Received: from localhost (localhost [127.0.0.1]) by zimbra.cs.ucla.edu (Postfix) with ESMTP id B633B1605E0; Sun, 10 Jun 2018 09:12:35 -0700 (PDT) Original-Received: from zimbra.cs.ucla.edu ([127.0.0.1]) by localhost (zimbra.cs.ucla.edu [127.0.0.1]) (amavisd-new, port 10032) with ESMTP id 5L9OYLRWrgju; Sun, 10 Jun 2018 09:12:35 -0700 (PDT) Original-Received: from localhost (localhost [127.0.0.1]) by zimbra.cs.ucla.edu (Postfix) with ESMTP id ECFC31605B7; Sun, 10 Jun 2018 09:12:34 -0700 (PDT) X-Virus-Scanned: amavisd-new at zimbra.cs.ucla.edu Original-Received: from zimbra.cs.ucla.edu ([127.0.0.1]) by localhost (zimbra.cs.ucla.edu [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id 1ISuTiDh5bTn; Sun, 10 Jun 2018 09:12:34 -0700 (PDT) Original-Received: from [192.168.1.9] (unknown [47.154.30.119]) by zimbra.cs.ucla.edu (Postfix) with ESMTPSA id 89159160543; Sun, 10 Jun 2018 09:12:34 -0700 (PDT) Openpgp: preference=signencrypt Autocrypt: addr=eggert@cs.ucla.edu; prefer-encrypt=mutual; keydata= xsFNBEyAcmQBEADAAyH2xoTu7ppG5D3a8FMZEon74dCvc4+q1XA2J2tBy2pwaTqfhpxxdGA9 Jj50UJ3PD4bSUEgN8tLZ0san47l5XTAFLi2456ciSl5m8sKaHlGdt9XmAAtmXqeZVIYX/UFS 96fDzf4xhEmm/y7LbYEPQdUdxu47xA5KhTYp5bltF3WYDz1Ygd7gx07Auwp7iw7eNvnoDTAl KAl8KYDZzbDNCQGEbpY3efZIvPdeI+FWQN4W+kghy+P6au6PrIIhYraeua7XDdb2LS1en3Ss mE3QjqfRqI/A2ue8JMwsvXe/WK38Ezs6x74iTaqI3AFH6ilAhDqpMnd/msSESNFt76DiO1ZK QMr9amVPknjfPmJISqdhgB1DlEdw34sROf6V8mZw0xfqT6PKE46LcFefzs0kbg4GORf8vjG2 Sf1tk5eU8MBiyN/bZ03bKNjNYMpODDQQwuP84kYLkX2wBxxMAhBxwbDVZudzxDZJ1C2VXujC OJVxq2kljBM9ETYuUGqd75AW2LXrLw6+MuIsHFAYAgRr7+KcwDgBAfwhPBYX34nSSiHlmLC+ KaHLeCLF5ZI2vKm3HEeCTtlOg7xZEONgwzL+fdKo+D6SoC8RRxJKs8a3sVfI4t6CnrQzvJbB n6gxdgCu5i29J1QCYrCYvql2UyFPAK+do99/1jOXT4m2836j1wARAQABzSBQYXVsIEVnZ2Vy dCA8ZWdnZXJ0QGNzLnVjbGEuZWR1PsLBfgQTAQIAKAUCTIByZAIbAwUJEswDAAYLCQgHAwIG FQgCCQoLBBYCAwECH In-Reply-To: <837en6sms4.fsf@gnu.org> Content-Language: en-US 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: 208.118.235.43 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:147265 Archived-At: Eli Zaretskii wrote: > OTOH, maybe I do agree, as long as "blindly" is an essential part of > that rule ;-) Yes, the "blindly" is essential. It's OK to use xmint_ptr on any mint_ptr= , so=20 long as you don't blindly trust the result to be a valid C pointer of the= kind=20 that you want; that is, you have to know that your C code created the min= t_ptr=20 in question and that no Lisp code can have replaced the mint_ptr with som= e other=20 object (perhaps also a mint_ptr). This is like XSAVE_POINTER, where you a= lso=20 have to know that Lisp code has not replaced the Lisp_Save_Value object w= ith=20 some other object (perhaps also of type Lisp_Save_Value and with a pointe= r payload). The main difference is that Lisp code can easily coin a mint_ptr (simply = by=20 using a fixnum) whereas it can't easily coin a Lisp_Save_Value, so there'= s less=20 runtime checking to catch bugs in the C code. However, if two or more=20 Lisp_Save_Value objects are exposed to Lisp code then the Lisp code can p= ass one=20 where the other is expected and this can cause the same sort of crash as = passing=20 a fixnum where a mint_ptr is expected, so introducing mint_ptr doesn't ma= ke=20 things that much more dangerous in principle than they were before.