From: Noah Lavine <noah.b.lavine@gmail.com>
To: Andy Wingo <wingo@pobox.com>
Cc: guile-devel <guile-devel@gnu.org>
Subject: Re: Build Error in master
Date: Tue, 7 Feb 2012 09:07:27 -0500 [thread overview]
Message-ID: <CA+U71=Pbf2+U6Xj0VV-LaVOnxANSWN2D+Y_-3xHGCP-JV=0r7Q@mail.gmail.com> (raw)
In-Reply-To: <CA+U71=Psi=QRcDRtAyo9JY2cFh08UHq2foOqddHhM3LiT_bxug@mail.gmail.com>
Hello,
I inserted a GC_is_visible check in my code and learned that 'symbols'
is visible, but the things it points to were getting garbage collected
anyway. It seemed like a GC bug, so I'm trying to build Guile with the
latest version of GC and hoping that fixes it.
I just wanted to warn everyone that the GC_get_free_space_divisor
function will break with libgc 7.2alpha6, because libgc includes the
same function with the same name. I'm not sure what to do about that -
probably try to automatically discover it in configure and put more
#ifdefs around our definition (gc.c:212).
Noah
On Thu, Feb 2, 2012 at 9:59 PM, Noah Lavine <noah.b.lavine@gmail.com> wrote:
> Got it! And unfortunately, it's a GC error. Here's what happens:
>
> symbols is an SCM object defined in symbols.c. It points to an
> scm_cell_t which has two elements: a type tag, and a pointer to an
> scm_weak_set_t. That scm_cell_t is at 0x10101cff0.
>
> However, that scm_cell_t is garbage collected in the scm_cons at
> symbols.c:250. The reason it gets filled with SCM_EOL is that the cons
> is scm_cons (SCM_BOOL_F, SCM_EOL). So I expect that the scm_cell_t is
> garbage collected and then immediately reclaimed to be the pair, which
> would result in its second cell being filled with SCM_EOL, which would
> explain why we later extract SCM_EOL from it.
>
> As a test, I changed the variable 'symbols' in symbols.c to be
> non-static. That didn't fix it, but then again, I don't really know
> how GC works yet.
>
> I can read the libgc documentation and try to figure this out, but can
> anyone point me to what I should be looking for?
>
> Thanks,
> Noah
>
> On Wed, Feb 1, 2012 at 4:01 AM, Andy Wingo <wingo@pobox.com> wrote:
>> On Wed 01 Feb 2012 03:12, Noah Lavine <noah.b.lavine@gmail.com> writes:
>>
>>> In the failing call,
>>> the SCM 'symbols' is 0x10101cff0, but the failing set is at 0x304,
>>> which has not been allocated.
>>
>> 0x304 is one of the iflags, SCM_EOL I think.
>>
>> So, I know it might not have anything to do with it, but can you verify
>> that your guile includes patch 0aed71aa51e89e714de2392c2a5f44694dca77ea
>> ? I just committed that last night, and although it does not seem to be
>> related, who knows.
>>
>> Andy
>> --
>> http://wingolog.org/
next prev parent reply other threads:[~2012-02-07 14:07 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-26 14:26 Build Error in master Noah Lavine
2012-01-26 22:06 ` Andy Wingo
2012-01-27 1:04 ` Noah Lavine
2012-01-29 20:21 ` Catonano
2012-02-01 2:12 ` Noah Lavine
2012-02-01 9:01 ` Andy Wingo
2012-02-03 2:59 ` Noah Lavine
2012-02-07 14:07 ` Noah Lavine [this message]
2012-02-07 14:46 ` Noah Lavine
-- strict thread matches above, loose matches on Subject: below --
2012-03-08 2:23 Build Error in Master Noah Lavine
2012-03-08 2:46 ` Mark H Weaver
2012-03-09 14:34 ` Ludovic Courtès
2012-03-13 2:30 ` Noah Lavine
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