From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS4713 221.184.0.0/13 X-Spam-Status: No, score=-3.8 required=3.0 tests=AWL,BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED, SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY shortcircuit=no autolearn=ham autolearn_force=no version=3.4.2 Received: from neon.ruby-lang.org (neon.ruby-lang.org [221.186.184.75]) by dcvr.yhbt.net (Postfix) with ESMTP id 68BA61F4B4 for ; Thu, 1 Apr 2021 18:08:16 +0000 (UTC) Received: from neon.ruby-lang.org (localhost [IPv6:::1]) by neon.ruby-lang.org (Postfix) with ESMTP id DD0CB1210BA; Fri, 2 Apr 2021 03:07:11 +0900 (JST) Received: from xtrwkhkc.outbound-mail.sendgrid.net (xtrwkhkc.outbound-mail.sendgrid.net [167.89.16.28]) by neon.ruby-lang.org (Postfix) with ESMTPS id 687391210B9 for ; Fri, 2 Apr 2021 03:07:08 +0900 (JST) Received: by filterdrecv-p3mdw1-85cc49d4fc-bzwl8 with SMTP id filterdrecv-p3mdw1-85cc49d4fc-bzwl8-19-60660C02-131 2021-04-01 18:08:02.980424125 +0000 UTC m=+776102.235524760 Received: from herokuapp.com (unknown) by ismtpd0143p1mdw1.sendgrid.net (SG) with ESMTP id xdAH8v2-QtufYm4Fn5MdGg for ; Thu, 01 Apr 2021 18:08:02.889 +0000 (UTC) Date: Thu, 01 Apr 2021 18:08:03 +0000 (UTC) From: headius@headius.com Message-ID: References: Mime-Version: 1.0 X-Redmine-MailingListIntegration-Message-Ids: 79196 X-Redmine-Project: ruby-master X-Redmine-Issue-Tracker: Bug X-Redmine-Issue-Id: 17771 X-Redmine-Issue-Author: headius X-Redmine-Sender: headius X-Mailer: Redmine X-Redmine-Host: bugs.ruby-lang.org X-Redmine-Site: Ruby Issue Tracking System X-Auto-Response-Suppress: All Auto-Submitted: auto-generated X-SG-EID: =?us-ascii?Q?FFqrkVUH+vvTO0v2jw+akFtsx0ctu2v3V2wlBAc+sNo+7BvBUyQBiUbImLL4oN?= =?us-ascii?Q?fkrl0J45fCss+RbaL0QLljAEKz+UjxReY+cOwQ1?= =?us-ascii?Q?aYdoomqkF0QWyilR14GpJTdMi2ixPHKoqn1spSf?= =?us-ascii?Q?GotVk35Nh4HllydSp3anhtJ+r4XBpIU82pNCBbh?= =?us-ascii?Q?bzWgJiKHeqLUUxedeYAwyq46wUQxz2c2F96pYJy?= =?us-ascii?Q?EYXRvsoH2pzQVrG1k=3D?= To: ruby-core@ruby-lang.org X-Entity-ID: b/2+PoftWZ6GuOu3b0IycA== X-ML-Name: ruby-core X-Mail-Count: 103153 Subject: [ruby-core:103153] [Ruby master Bug#17771] String#start_with? should not construct MatchData or set $~ X-BeenThere: ruby-core@ruby-lang.org X-Mailman-Version: 2.1.15 Precedence: list Reply-To: Ruby developers List-Id: Ruby developers List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: ruby-core-bounces@ruby-lang.org Sender: "ruby-core" Issue #17771 has been reported by headius (Charles Nutter). ---------------------------------------- Bug #17771: String#start_with? should not construct MatchData or set $~ https://bugs.ruby-lang.org/issues/17771 * Author: headius (Charles Nutter) * Status: Open * Priority: Normal * Backport: 2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN, 3.0: UNKNOWN ---------------------------------------- I am working on making $~ more thread-safe in JRuby and came across this unexpected behavior: ```ruby $ rvm ruby-3.0 do ruby -e '"foo".start_with?(/foo/); p $~' # ``` The `start_with?` method was added 11 years ago in https://bugs.ruby-lang.org/issues/3388 but I do not think the set of $~ was an intended feature. The `start_with?` method could be much faster and more thread-safe if it did not use the frame-local backref slot and did not allocate a MatchData. Compare with `match?` which was added specifically (without MatchData or backref setting) to provide a fast way to check if a Regexp matches. I propose that `start_with?` stop constructing MatchData, stop setting backref, and provide only its boolean result in the same way as `match?`. -- https://bugs.ruby-lang.org/