Segmentation fault on Debian Squeeze when analyzing m4a file

[mkonecny]

Step 1: Ensure your environment is Debian Squeeze

Step 2: Download any m4a file:

wget http://www.morrisontrio.com/resources/Morrison%20Trio%20Sample%20-%20Air%20by%20J.S.%20Bach.m4a

Step 3: analyze with -b and -f json parameters.

Output: Segmentation fault

[x42]

Could you create a backtrace?

gdb --args  silan -b -f json ....

(gdb) run
   [.. crash...]
(gdb)  thread apply all bt

Chances are that it's an issue w/ libav* that comes with debian in particular the 'aac' decoder of it. I highly recommend to use ffmpeg-1.2 from ffmpeg.org

[mkonecny]

Reading symbols from /usr/bin/silan...(no debugging symbols found)...done.
(gdb) run
Starting program: /usr/bin/silan -b -f json Morrison\ Trio\ Sample\ -\ Air\ by\ J.S.\ Bach.m4a
[Thread debugging using libthread_db enabled]

Program received signal SIGSEGV, Segmentation fault.
0xb7a58a85 in ?? () from /usr/lib/i686/cmov/libavcodec.so.52
(gdb) thread apply all bt

Thread 1 (Thread 0xb6f116d0 (LWP 20055)):
#0  0xb7a58a85 in ?? () from /usr/lib/i686/cmov/libavcodec.so.52
#1  0x0804b8b4 in ?? ()
Backtrace stopped: previous frame inner to this frame (corrupt stack?)
(gdb) 

[x42]

right. ffmpeg/libav problem.

I'm about to prepare a statically linked binary (using ffmpeg-1.2) instead of distribution provided libavcodec.

[mkonecny]

This may be a Debian package issue as well.

Before

$ sudo dpkg -l | grep libav
ii  libavcodec52                       4:0.5.10-1                        ffmpeg codec library
rc  libavdevice52                      4:0.5.10-1                        ffmpeg device handling library
rc  libavfilter0                       4:0.5.10-1                        ffmpeg video filtering library
ii  libavformat52                      4:0.5.10-1                        ffmpeg file format library
ii  libavutil49                        4:0.5.10-1                        ffmpeg utility library
rc  libpostproc51                      4:0.5.10-1                        ffmpeg video postprocessing library
rc  libswscale0                        4:0.5.10-1                        ffmpeg video scaling library

using debian squeeze backports

$ sudo dpkg -l | grep libav
ii  libav-tools                        6:0.8.5-1~bpo60+1                 Multimedia player, server, encoder and transcoder
ii  libavcodec53                       6:0.8.5-1~bpo60+1                 Libav codec library
ii  libavdevice53                      6:0.8.5-1~bpo60+1                 Libav device handling library
ii  libavfilter2                       6:0.8.5-1~bpo60+1                 Libav video filtering library
ii  libavformat53                      6:0.8.5-1~bpo60+1                 Libav file format library
ii  libavutil51                        6:0.8.5-1~bpo60+1                 Libav utility library

I had to remove all the old libav packages manually since they were allowed to co-exist alongside the new backports. However this also uninstalled silan. So i go to install silan again:

sudo apt-get install silan
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following extra packages will be installed:
  libavcodec52 libavformat52 libavutil49
The following NEW packages will be installed:
  libavcodec52 libavformat52 libavutil49 silan
0 upgraded, 4 newly installed, 0 to remove and 8 not upgraded.
Need to get 0 B/4,833 kB of archives.
After this operation, 12.9 MB of additional disk space will be used.
Do you want to continue [Y/n]? 

It insists on using the old packages.

[x42]

In that case you (or the packager) will need to re-build silan against the new libav*. ffmpeg/libav is not ABI compatible. An application will only work with the version of ffmpeg/libav that it was built with.

Anyway, give http://robin.linuxaudio.org/tmp/silan-i386-linux-gnu-v0.3.1-9-g817ff4c.tgz http://robin.linuxaudio.org/tmp/silan-x86_64-linux-gnu-v0.3.1-9-g817ff4c.tgz a try. it only requires libm.so.6, libdl.so.2, libpthread.so.0 and libc.so.6 -- IOW it will run on any reasonable GNU/Linux system since 2006.

[mkonecny]

Pardon my ignorance, since I haven't worked with Debian packages yet. I'm guessing the problem is libavcodec52 was the one available when the debian package was generated and so that's why 52 was hardcoded as a dependency.

Is it possible to make a Debian package more flexible in this regard?

[mkonecny]

OK, I will your new binaries a try, thx :)

[x42]

libavcodec52 was used to link silan (when the package was created). The dependency of the packages comes from the binary itself.
Run ldd /some/binary (here ldd /usr/bin/silan) to get a list of libraries it requires.

The maintainer of the package will need to compile a new package...

[mkonecny]

Hey we wrote our messages at the same time so ignore that :).

I'm using your statically linked binary and it works perfectly. Is this a temporary link, or can I start sharing it?

[x42]

They're temporary but will likely be around for a while..

I suggest to have Daniel (or whoever builds the debian packages of airtime these days) look into https://github.com/x42/silan/blob/master/x-pbuildstatic.sh -- this script creates those binaries.

The proper solution however is to file a bug report for debian/squeeze and have them sort out the issue.

[mkonecny]

When running silan against the libav packages from squeeze backports the issue is fixed. Closing this issue since it's not a silan bug.

Slightly off-topic: If Debian package maintainers knew that a package in the main apt repo segfaulted, would they move the entire package from backports into main? Or would they just backport the changeset which fixed the problem into main.