Your message dated Mon, 28 Sep 2009 22:57:53 +0000
with message-id <[email protected]>
and subject line Bug#548815: fixed in libvorbisidec 1.0.2+svn16259-2
has caused the Debian Bug report #548815,
regarding ivorbisfile_example.c triggers alignment error on armel
to be marked as done.
This means that you claim that the problem has been dealt with.
If this is not the case it is now your responsibility to reopen the
Bug report if necessary, and/or fix the problem forthwith.
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--
548815: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=548815
Debian Bug Tracking System
Contact [email protected] with problems
--- Begin Message ---
Package: libvorbisidec-dev
On armel, when i build ivorbisfile_example.c against the stock
libvorbisidec package, it triggers a series of CPU alignment faults, and
consequently produces bad data.
Interestingly, this seems to be because gcc is happy to align an array
of chars on an odd address under armel (on i386, gcc appears to always
place char arrays on 4-byte boundaries).
since ov_read asks for a char* buffer, but then casts it to shorts, if
the char* buffer is not short-aligned, the CPU sees an alignment fault.
What the CPU does in the case of an alignment fault is configurable by
echoing the decimal representation of a bitmask into /proc/cpu/alignment:
1 -> warn
2 -> fixup (software workaround to correct the alignment error)
4 -> signal (send a SIGBUS to the child process)
What to do on a user fault defaults to 0 (none of the above), but if you
set it to 4 or 5, the process will receive a SIGBUS.
with the alignment user fault set to 0, the ivorbisfile_example.c simply
produces bad data.
I reported a few things that should probably be fixed to upstream, and
have a new version of the debian package ready which fixes the example
to work properly; i'll upload that version shortly.
further reference:
I originally documented the problem upstream in april:
http://lists.xiph.org/pipermail/tremor/2009-April/001564.html
and followed up again earlier this month (the proposed fixes follow this
thread):
http://lists.xiph.org/pipermail/tremor/2009-September/001587.html
Martin Guy pointed me in the right direction on
http://bugs.debian.org/547525
--dkg
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--- Begin Message ---
Source: libvorbisidec
Source-Version: 1.0.2+svn16259-2
We believe that the bug you reported is fixed in the latest version of
libvorbisidec, which is due to be installed in the Debian FTP archive:
libvorbisidec-dev_1.0.2+svn16259-2_i386.deb
to pool/main/libv/libvorbisidec/libvorbisidec-dev_1.0.2+svn16259-2_i386.deb
libvorbisidec1_1.0.2+svn16259-2_i386.deb
to pool/main/libv/libvorbisidec/libvorbisidec1_1.0.2+svn16259-2_i386.deb
libvorbisidec_1.0.2+svn16259-2.diff.gz
to pool/main/libv/libvorbisidec/libvorbisidec_1.0.2+svn16259-2.diff.gz
libvorbisidec_1.0.2+svn16259-2.dsc
to pool/main/libv/libvorbisidec/libvorbisidec_1.0.2+svn16259-2.dsc
A summary of the changes between this version and the previous one is
attached.
Thank you for reporting the bug, which will now be closed. If you
have further comments please address them to [email protected],
and the maintainer will reopen the bug report if appropriate.
Debian distribution maintenance software
pp.
Daniel Kahn Gillmor <[email protected]> (supplier of updated libvorbisidec
package)
(This message was generated automatically at their request; if you
believe that there is a problem with it please contact the archive
administrators by mailing [email protected])
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA512
Format: 1.8
Date: Mon, 28 Sep 2009 16:01:06 -0400
Source: libvorbisidec
Binary: libvorbisidec-dev libvorbisidec1
Architecture: source i386
Version: 1.0.2+svn16259-2
Distribution: unstable
Urgency: low
Maintainer: Daniel Kahn Gillmor <[email protected]>
Changed-By: Daniel Kahn Gillmor <[email protected]>
Description:
libvorbisidec-dev - Integer-only Ogg Vorbis decoder, AKA "tremor" (Development
Files)
libvorbisidec1 - Integer-only Ogg Vorbis decoder, AKA "tremor"
Closes: 548815
Changes:
libvorbisidec (1.0.2+svn16259-2) unstable; urgency=low
.
* updated ivorbisfile_example.c to ensure proper alignment of pcm data
on short boundaries (affects any arch where char arrays can be placed
on misaligned boundaries, such as armel).
(Closes: #548815)
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