From: Johannes Schindelin <Johannes.Schindelin@gmx.de> To: Junio C Hamano <firstname.lastname@example.org> Cc: "Ævar Arnfjörð Bjarmason" <email@example.com>, firstname.lastname@example.org, "Jeff King" <email@example.com>, "Denton Liu" <firstname.lastname@example.org>, "Jeff Hostetler" <email@example.com> Subject: Re: [PATCH] trace2: refactor to avoid gcc warning under -O3 Date: Thu, 6 May 2021 22:29:57 +0200 (CEST) [thread overview] Message-ID: <nycvar.QRO.firstname.lastname@example.org> (raw) In-Reply-To: <email@example.com> [-- Attachment #1: Type: text/plain, Size: 1811 bytes --] Hi Junio, On Thu, 6 May 2021, Junio C Hamano wrote: > Johannes Schindelin <Johannes.Schindelin@gmx.de> writes: > > > Hi Ævar, > > > > On Wed, 5 May 2021, Ævar Arnfjörð Bjarmason wrote: > > > >> Refactor tr2_dst_try_uds_connect() to avoid a gcc warning that > >> appears under -O3 (but not -O2). This makes the build pass under > >> DEVELOPER=1 without needing a DEVOPTS=no-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  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 on > >> 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 could > > imagine, for example, that a oneline like this would be much more helpful > > to any reader: > > > > trace2: do not assume errno != 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
next prev parent reply other threads:[~2021-05-06 20:30 UTC|newest] Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-04-01 7:30 [PATCH] Fix -Wmaybe-uninitialized warnings under -O0 Denton Liu [not found] ` <CAPUEspgBkmxszgBee8C9hZnEwqztf-XKEj7LB_jWVFJaJCge0w@mail.gmail.com> 2020-04-01 9:05 ` Denton Liu 2020-04-01 9:52 ` Jeff King 2020-04-01 14:06 ` Denton Liu 2020-04-03 14:04 ` Jeff King 2020-04-03 14:38 ` Jeff King 2020-04-04 12:07 ` Denton Liu 2020-04-04 14:21 ` Jeff King 2021-05-05 8:40 ` [PATCH] trace2: refactor to avoid gcc warning under -O3 Ævar Arnfjörð Bjarmason 2021-05-05 9:47 ` Junio C Hamano 2021-05-05 13:34 ` Jeff King 2021-05-05 14:38 ` Johannes Schindelin 2021-05-06 1:26 ` Junio C Hamano 2021-05-06 20:29 ` Johannes Schindelin [this message] 2021-05-06 21:10 ` Junio C Hamano 2021-05-11 14:34 ` Johannes Schindelin 2021-05-11 18:00 ` Jeff King 2021-05-11 20:58 ` Junio C Hamano 2021-05-11 21:07 ` Jeff King 2021-05-11 21:33 ` Junio C Hamano 2021-05-11 7:03 ` Junio C Hamano 2021-05-11 13:04 ` [PATCH v2] " Ævar Arnfjörð Bjarmason 2021-05-11 16:40 ` Jeff Hostetler 2021-05-11 17:54 ` Jeff King 2021-05-11 18:08 ` Jeff King 2021-05-11 21:09 ` Junio C Hamano 2021-05-20 0:20 ` Junio C Hamano 2021-05-20 11:05 ` [PATCH v3] " Ævar Arnfjörð Bjarmason 2021-05-20 13:13 ` Jeff King 2021-05-20 22:08 ` Junio C Hamano 2021-05-21 9:34 ` Jeff King
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