From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS31976 209.132.180.0/23 X-Spam-Status: No, score=-2.9 required=3.0 tests=AWL,BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,RCVD_IN_DNSWL_HI,RCVD_IN_SORBS_SPAM, RP_MATCHES_RCVD shortcircuit=no autolearn=no autolearn_force=no version=3.4.0 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by dcvr.yhbt.net (Postfix) with ESMTP id A491920281 for ; Wed, 20 Sep 2017 07:40:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751750AbdITHkm (ORCPT ); Wed, 20 Sep 2017 03:40:42 -0400 Received: from mail-io0-f194.google.com ([209.85.223.194]:33053 "EHLO mail-io0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751723AbdITHkl (ORCPT ); Wed, 20 Sep 2017 03:40:41 -0400 Received: by mail-io0-f194.google.com with SMTP id j26so697580iod.0 for ; Wed, 20 Sep 2017 00:40:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-transfer-encoding:content-language; bh=irdkj8ohFNFQAcFaPdxD9PHlk1DhL2St0WQR3HI4yE0=; b=MQjHBzitvwvidrA5XtBBfdWyvyjKDYhjN85k4+aVlBWARucUvGKEoWLMYKCo6LW/l5 H2JE9Rw64YgTAE1uR3E7HOZo2+Di1bzzgeYwMUdBNfLZJYRgBWcjsPm7UAHOmlSgVEaO pLT3hGl/DleW0RtJ+kkEjOxkGJVV6xWYBXSyRdj65D8ZsggLp8U2a6N53Y31FLt+6MMp KlgIFgRhuZiSGMjO9nAwiuLNHp0cd6QV4MwgfVhU9IynZlPEqEf+ru7ysg6w/KLCBZR9 F6Oop9EHm6eTdLjOuWrutmtd81NdUucAeClyYIskKanoEW3x7za8ZLZRN1yDyVT/dwP5 0F7w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-transfer-encoding :content-language; bh=irdkj8ohFNFQAcFaPdxD9PHlk1DhL2St0WQR3HI4yE0=; b=QiK+7jW51hhrQBeDBKh0ALNmh/lH7qzxqaYm971nanFGf5pTrbiuJQHJ2xWUJ+VJu8 zQ/7lAZlrIethoYSnx1KI2QPJ2TRYN/U18eUB4D/pGViMOubQlFU0ll23TXJA31jqpxi i3IRgtg88ZgHZr5wNDXVyg371s5Rs5VQTX+y//HjVp2AsOLiPEpC/zNWWp6bxrMayQYo ApmwaHZNK6ON9DqSp1vo2ci678NWQ0YCRUPO7dqUX4DH4ikBVkjE81yky/5r3WfUrb+/ aKeWGFPi9hBZlf7XCTbycjBbxF8ZTxNolfrPG486DdMHsmuWNajjtdwBLZnYFXXBrQgk ySnw== X-Gm-Message-State: AHPjjUgQ6HXMWQv5COtPIV+9A9j/DW/HSL89/un3F1jpELRFy74PInDv XEZ/0v+mURC0LFyiuYkbuzrMVcGF X-Google-Smtp-Source: AOwi7QB8Z4ovcaCVOA1PmPiowRZxAZDcJMBLLRkIATCkyolRfatHMc70jJ2cmkbxhMkO3ZDz/wewYQ== X-Received: by 10.107.135.90 with SMTP id j87mr5503699iod.159.1505893240779; Wed, 20 Sep 2017 00:40:40 -0700 (PDT) Received: from [10.4.2.238] ([14.102.72.146]) by smtp.gmail.com with ESMTPSA id s81sm624093ioe.55.2017.09.20.00.40.38 (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Wed, 20 Sep 2017 00:40:40 -0700 (PDT) Subject: Re: [PATCH v2] for_each_string_list_item: avoid undefined behavior for empty list To: Jonathan Nieder , Junio C Hamano Cc: Michael Haggerty , Alex Riesen , git@vger.kernel.org References: <20170915184323.GU27425@aiede.mtv.corp.google.com> <20170920023008.GB126984@aiede.mtv.corp.google.com> <20170920052705.GC126984@aiede.mtv.corp.google.com> From: Kaartic Sivaraam Message-ID: Date: Wed, 20 Sep 2017 13:10:35 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0 MIME-Version: 1.0 In-Reply-To: <20170920052705.GC126984@aiede.mtv.corp.google.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-Cyberoam-smtpxy-version: 1.0.6.3 X-Cyberoam-AV-Policy: default X-CTCH-Error: Unable to connect local ctasd Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org On Wednesday 20 September 2017 10:57 AM, Jonathan Nieder wrote: > Guard the loop with a NULL check to make the intent crystal clear to > even the most pedantic compiler. A suitably clever compiler could let > the NULL check only run in the first iteration, Noted this just now. So, the overhead doesn't occur when the compilers are clever enough. And as I said in my previous email to this thread, at least 'gcc' and 'clang' seem to be clever enough. > ... but regardless, this > overhead is likely to be dwarfed by the work to be done on each item. :-) That's of course seems to be true.