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: AS53758 23.128.96.0/24 X-Spam-Status: No, score=-3.1 required=3.0 tests=AWL,BAYES_00,DKIM_SIGNED, DKIM_VALID,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MALFORMED_FREEMAIL, RCVD_IN_DNSWL_MED,SPF_HELO_PASS,SPF_PASS shortcircuit=no autolearn=ham autolearn_force=no version=3.4.2 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by dcvr.yhbt.net (Postfix) with ESMTP id 323131F5AE for ; Thu, 6 May 2021 20:30:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234338AbhEFUbJ (ORCPT ); Thu, 6 May 2021 16:31:09 -0400 Received: from mout.gmx.net ([212.227.17.20]:40905 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232831AbhEFUbJ (ORCPT ); Thu, 6 May 2021 16:31:09 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gmx.net; s=badeba3b8450; t=1620333000; bh=WhXR8qLjAXF188AS/K+FQwKaY6gyt4gTo8jSlQHXPI8=; h=X-UI-Sender-Class:Date:From:To:cc:Subject:In-Reply-To:References; b=SyDDOtuBObGn+I28DQl1woW48j2ZjNlritEVwofOJ8cA3PURqRg+fbQS/E2AxZWDn +f43txas6izJG2Xx7hXyh+xPMzLHEKFI1bJdzrCT7ZZHDjBJa+Khe42Lb/dV0GIBVR qDxpx5HBsFpPJL5GF8Oo59lMOFATJJk4izG61P2M= X-UI-Sender-Class: 01bb95c1-4bf8-414a-932a-4f6e2808ef9c Received: from [172.28.146.104] ([89.1.212.20]) by mail.gmx.net (mrgmx105 [212.227.17.168]) with ESMTPSA (Nemesis) id 1M7sHy-1lat1G0Hqs-004zeB; Thu, 06 May 2021 22:30:00 +0200 Date: Thu, 6 May 2021 22:29:57 +0200 (CEST) From: Johannes Schindelin X-X-Sender: virtualbox@gitforwindows.org To: Junio C Hamano cc: =?UTF-8?Q?=C3=86var_Arnfj=C3=B6r=C3=B0_Bjarmason?= , git@vger.kernel.org, Jeff King , Denton Liu , Jeff Hostetler Subject: Re: [PATCH] trace2: refactor to avoid gcc warning under -O3 In-Reply-To: Message-ID: References: <20200404142131.GA679473@coredump.intra.peff.net> User-Agent: Alpine 2.21.1 (DEB 209 2017-03-23) MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="8323328-1934349159-1620333000=:50" X-Provags-ID: V03:K1:oQEWalE2VyCq0Ex5GZyCVWQM2euUywpLNkoU1fpnSPVjnLnXrrH eCYzLoeI1LFsmP/gXEz1QmxH8NdVg+yCqtPezmNJtlEVL+1fG0xPxq6uqSabuXqGTbhpGt9 C5pP+74GHSiSet0fRyrmmIBzL+AWO5keqKrwDxYg9qUPMreIHyvSN/vuxXnhVlvuSf6wbOl iYdk86nMIHCkyvIyvqWuA== X-UI-Out-Filterresults: notjunk:1;V03:K0:rmPoLJrb5bs=:EAgBq3o2mdmKmpOaUHeIZf wW51OryCT3UZrO5nMnYcTBBa1owhept+0XmD9N7ZP2/HWrBfps4dNPC03hXQL9OC0h1wUnicB HJNT8vWSbC/s6Vr0PE/rtC5anIt6+rHjEpaOZjpk080uSaFisBMZfXkLQFwCaHfwNgWVPbqqj EQEEnxGfx0I6Zf4scp0WYI2u1TZmpchuJfKeoWbdDRsYGgcd16SpbETGC7V4rmIKsZ1Bd5him XD942EojfS1NkkdIb1yfca1iTFSI7tgCSGFbQ+BsX3ULtBIj9wF7u2804jVJZwEmMqev+RcLz t0ex7Md0emFFZRnD8g/Xl+hgc6iLhrYltzRM2vDHnxEFVNJQOHPHUE7IcGG76LtWi/IjlBEzQ asGPMUBCGFTerwb/EX2UPTdmPS27184vyOP6Hd5DTNl5gF3VpIQ0WZCc582Cq+Mr695T09nKZ VTKmbqQmR1wDCarkJJvnGD4ov9Oj4tVxhNzwHr0laD10AcZHm3nzlFdVWeiwLRprMi7gKURqr +OPf3TzEKTgbPU7dAjJJsfFSzyx9msOe+Efl5P8L4kQlGYa0VWFSyYuG7WzqZLHWVdOOAZE+K IJ+2ZUl4QHOzYmuZTzIZKO71ZZE7GakqOzctsfcDlWWhVtLrnzfj39C3DXgXhZaikN8RiMO0m Q/sIXTQRDkYgr4sNoTL+V6CrGwK0AvntQy0QSFMQPhmMMnNErXbctLsCkQjOyWCBnOoTRmgD+ vkrIK6HmipdfTCygn4oS1AQxsacHm3tn7zAeG4aCt6kY8uLikKHKCBPrPlv/eLeeFvqhBV4hq wStzz05fBreAAf6wRtBbGgAlHi8BXdi4Hpees1Eh8BCWH/uDi4VNA1X24Ttd3Kq0SD6Ydo/lB fbSGYlYotntIvlgwlKTDttzYFpiqJjKfdPTTrLF8V2G2bDI0lwLUnZ64EBqMahP7nbSrulPAO P05TqnI52RxtUyNLyYnmZoxPjzogfdBOXl45MUEkufbZb8plGa9SEA5x/EX76yhv4+ZrqOAsv 96nrWMk8cFPp2O/Ew4HlINwu4foUuGXErOc6yEriuJa7fvHY8fP18e9zwl/9AoN90t/EDhWlt oX8xZ+fLZEpAFSuT3OE4r76eQQNH2gV+6frrxqLSMMNN7RBYiSvSmUpNBuKZFRl9ND1peHbaX Obw86W27Bv9QbnH462InWLhdBIQeSgoNEyP6kfgrOuFR6QAvE3Oah+/AK3I55jBlWg4wPTVL2 iD3i6e8p7PkpfLzyY Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. --8323328-1934349159-1620333000=:50 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Hi Junio, On Thu, 6 May 2021, Junio C Hamano wrote: > Johannes Schindelin writes: > > > Hi =C3=86var, > > > > On Wed, 5 May 2021, =C3=86var Arnfj=C3=B6r=C3=B0 Bjarmason wrote: > > > >> Refactor tr2_dst_try_uds_connect() to avoid a gcc warning[1] that > >> appears under -O3 (but not -O2). This makes the build pass under > >> DEVELOPER=3D1 without needing a DEVOPTS=3Dno-error. > >> > >> This can be reproduced with GCC Debian 8.3.0-6, but not e.g. with > >> clang 7.0.1-8+deb10u2. We've had this warning since > >> ee4512ed481 (trace2: create new combined trace facility, 2019-02-22). > >> > >> As noted in [2] this warning happens because the compiler doesn't > >> assume that errno must be non-zero after a failed syscall. Let's work > >> around it as suggested in that analysis. We now return -1 ourselves o= n > >> error, and save away the value of errno in a variable the caller > >> passes in. > > > > It would probably be a lot nicer if you lead with this insight. I coul= d > > imagine, for example, that a oneline like this would be much more help= ful > > to any reader: > > > > trace2: do not assume errno !=3D 0 after a failed syscall > > But that is misleading. > > My understanding is that this patch is about working around > compilers that do not know that a failed syscall means errno would > be set to non-zero. Am I mistaken? > > Otherwise I'd strongly prefer to see a word that hints that this is > an otherwise unneeded workaround for comiplers. Your suggested > title instead hints that it is wrong to assume that errno will be > set to non-zero after a syscall. I do not think that is the message > we want to send to our readers. Right, the oneline I suggested was only for the original patch, with which I disagreed. Ciao, Dscho --8323328-1934349159-1620333000=:50--