python pymtp crashes with segfault

[Alex Jones]

Pymtp crashes with a segfault when running in Lucid 10.04.

The following error is logged when running /usr/share/doc/python-pymtp/examples/deviceinfo.py

segfault at 53 ip 00007eff29b39b54 sp 00007fffd5757bf8 error 4 in _ctypes.so[7eff29b32000+1d000]

This happens when either trying to list all tracks or all files.

[Alex Jones (alex-jones)]

This was whilst trying to list files on a Creative Zen Vision:M.

[Fergal Daly (fergal)]

It seems the python code is out of sync with the C code. In particular, there are fields missing from the python struct definitions with the result that the "next" field is often incorrect, leading to following a bad pointer (not a pointer at all actually).

I've attached a patch that adds the missing "modificationdate" field to 2 of the structs. I don't know if this fixes everything but it certainly turns

python -c 'import pymtp;m=pymtp.MTP();m.connect();print m.get_filelisting(); m.disconnect()'

into something that doesn't segfault anymore. It also makes deviceinfo execute to completion too.

[Huw Lewis (huw-lewis2409)]

I have noticed exactly the same thing with libmtp 1.0.2 and pymtp 0.0.4-1.1 and have also created a patch to match thr libmtp.h header file. The changes I made included:
 - LIBMTP_Device: renamed interface_number to object_bitsize to match the libmtp.h name.
 - add modificationdate field c_long to LIBMTP_File
 - add modificationdate field c_long to LIBMTP_Track
 - add ALBUM and PLAYLIST values to the file type enum.

[Huw Lewis (huw-lewis2409)]

What needs to happen to move this along? I am happy to do some testing, reviewing, hacking etc. Are there any unit tests for pymtp?

[Fergal Daly (fergal)]

Simple patch.

[Brian Murray (brian-murray)]

Huw your attachment wasn't really a patch rather your full modified version of pymtp.py, subsequently I uploaded Fergal's patch. However, if there is more work to be done to get pymtp in better shape please let me know and I'll be happy to upload other patches.

[Launchpad Janitor (janitor)]

This bug was fixed in the package pymtp - 0.0.4-2ubuntu1

---------------
pymtp (0.0.4-2ubuntu1) oneiric; urgency=low

  * Fix crash when accessing file listing. Thanks to Fergal Daly for the
    patch. (LP: #575091)
 -- Brian Murray <email address hidden> Fri, 08 Jul 2011 13:27:06 -0700

[Fergal Daly (fergal)]

FYI, this approach to C extensions is extremely brittle. While I was
happy that pymtp existed, it can be broken again at any time by the
addition or reordering of fields in the C library.

If this is to be a supported module then the packager of libmtp will
have to be involved in order to ensure that changes in libmtp also
result in changes to pymtp.