From: Denton Liu <liu.denton@gmail.com>
To: Jeff King <peff@peff.net>
Cc: Git Mailing List <git@vger.kernel.org>
Subject: Re: [PATCH] Fix -Wmaybe-uninitialized warnings under -O0
Date: Wed, 1 Apr 2020 10:06:43 -0400 [thread overview]
Message-ID: <20200401140643.GA880372@generichostname> (raw)
In-Reply-To: <20200401095255.GA60227@coredump.intra.peff.net>
Hi Peff,
On Wed, Apr 01, 2020 at 05:52:55AM -0400, Jeff King wrote:
> On Wed, Apr 01, 2020 at 03:30:16AM -0400, Denton Liu wrote:
>
> > When compiling Git under -O0, gcc (Arch Linux 9.3.0-1) 9.3.0 produces
> > many -Wmaybe-uninitialized warnings. These are false positives since
> > when Git is compiled under -O2, gcc is smart enough to see that the
> > code paths that use these variables all initialise them beforehand.
> > Nonetheless, these warnings block the compilation process when
> > DEVELOPER=1 is enabled (which enables -Werror).
> >
> > Fix these warnings by initializing these variables with dummy values (0,
> > -1 or NULL as appropriate).
>
> Hmph. I almost always compile with -O0 and have been using gcc 9.3.0
> since it was packaged for Debian a few weeks ago, but I don't see any of
> these warnings.
>
> The current version in Debian unstable is 9.3.0-8, which picks up some
> extra patches from the upstream gcc-9 branch. But even if I download a
> snapshot of the original 9.3.0 release, it builds fine.
>
> So why does your version behave differently? And if this is a temporary
> state for a buggy version of gcc (that may be fixed in the next point
> release), is it worth changing our source code to appease it?
A correction to the earlier message... It seems like I wasn't reporting
the correct settings. I was actually compiling with -Og, not -O0
(whoops!).
I tested it with gcc-8 and it seems like it also reports the same
problem. Also, -O1 reports warnings as well.
I guess the question is do we only support -O0 and -O2 or should we
support the levels in between as well?
Sorry for the confusion,
Denton
>
> -Peff
next prev parent reply other threads:[~2020-04-01 14:06 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 [this message]
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
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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