From: Jeff King <peff@peff.net>
To: Johannes Sixt <j6t@kdbg.org>
Cc: Noam Postavsky <npostavs@users.sourceforge.net>, git@vger.kernel.org
Subject: Re: [BUG] A part of an edge from an octopus merge gets colored, even with --color=never
Date: Tue, 17 May 2016 17:57:49 -0400 [thread overview]
Message-ID: <20160517215749.GB16905@sigill.intra.peff.net> (raw)
In-Reply-To: <573B78CE.1080200@kdbg.org>
On Tue, May 17, 2016 at 10:02:22PM +0200, Johannes Sixt wrote:
> > Interesting. It replicates out of the box for me.
>
> "Out of the box" are the magic words. I usually compile with -O0, which
> doesn't trigger the valgrind report.
Heh, I meant that Noam's test worked out of the box. I also build with
-O0. I was able to replicate with different optimization levels.
I think the interesting thing here is actually the libc (and therefore
possibly your valgrind version). I tried compiling with ASAN and get a
color value of "48830". But no ASAN warning!
I think what is happening is that we over-allocate the new_columns array
based on a power of 2, but only initialize up to num_new_columns. So the
off-by-one accesses heap memory that is allocated but which we have
never written to.
> When I compile with a 3.x based gcc on Windows, I see these warnings:
>
> CC color.o
> color.c: In function 'color_parse_mem':
> color.c:203: warning: 'c.value' may be used uninitialized in this function
> color.c:203: warning: 'c.blue' may be used uninitialized in this function
> color.c:203: warning: 'c.green' may be used uninitialized in this function
> color.c:203: warning: 'c.red' may be used uninitialized in this function
>
> (which triggered my curiosity in this bug report). But they seem to be
> unrelated and are most likely false positives.
Yeah, I think that's unrelated. I'd be highly distrustful of
-Wuninitialized in gcc 3.x. We had to mark quite a few false positives
back then, that were later corrected in the 4.x series.
-Peff
prev parent reply other threads:[~2016-05-17 21:57 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-15 13:05 [BUG] A part of an edge from an octopus merge gets colored, even with --color=never Noam Postavsky
2016-05-17 19:07 ` Johannes Sixt
2016-05-17 19:45 ` Jeff King
2016-05-17 19:51 ` Jeff King
2016-05-17 19:55 ` Jeff King
2016-05-20 22:12 ` Noam Postavsky
2018-06-23 21:45 ` Noam Postavsky
2018-06-25 16:23 ` Jeff King
2018-06-30 12:47 ` Noam Postavsky
2018-08-06 18:34 ` Noam Postavsky
2018-08-06 21:28 ` Jeff King
2018-08-06 21:26 ` Jeff King
2018-09-02 0:34 ` Noam Postavsky
2018-09-08 16:13 ` Jeff King
2018-09-25 0:27 ` Noam Postavsky
2018-10-03 0:09 ` Noam Postavsky
2018-10-03 4:24 ` Jeff King
2018-10-03 22:32 ` Noam Postavsky
2018-10-09 4:51 ` Jeff King
2018-10-10 0:42 ` Noam Postavsky
2016-05-17 20:02 ` Johannes Sixt
2016-05-17 21:57 ` Jeff King [this message]
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