Python

ctypes broken on armhf

Bug #898172 reported by Loïc Minier on 2011-11-30

This bug affects 1 person

	Status	Importance	Assigned to
Python	New	Unknown	python-roundup #13508
python2.6 (Ubuntu)	Won't Fix	Undecided	Unassigned
python2.7 (Ubuntu)	Fix Released	Undecided	Unassigned
python3.2 (Ubuntu)	Fix Released	Undecided	Unassigned

Bug Description

Python's ctypes allows dynamically loading libraries. On linux, it parses ldconfig -p output for a given library name, skipping over incompatible ABIs. ABI is derived from uname output, which is incorrect. Currently, the code can't cope with "hard-float" in the ldconfig -p output on armhf.

I will attach a debdiff which allows ctypes to work on either armel or armhf, but wont work on a biarch or multiarch armel + armhf system.

The code should be redesigned to check the real ABI, not the uname output; one option to do so is to check the ABI of the currently running executable, e.g. ldd on sys.executable as done elsewhere in the script, but still seems fragile; another option is to look at /proc/$pid/maps (probably not portable); another option is to ask libc to do the loading (seems the safest).

Cheers,

Tags:

Related branches

lp://staging/debian/python2.7

lp://staging/ubuntu/precise/python2.7

lp://staging/ubuntu/precise/python3.2

Revision history for this message

Loïc Minier (lool) wrote on 2011-11-30:

python2.7 debdiff for the workaround Edit (2.6 KiB, text/plain)

Ubuntu Foundations Team Bug Bot (crichton) on 2011-11-30

tags:

added: patch

Revision history for this message

Matthias Klose (doko) wrote on 2011-11-30:

won't fix for python2.6, to be removed

Changed in python2.6 (Ubuntu):
status:	New → Won't Fix

Revision history for this message

Dr. David Alan Gilbert (davidgil-uk) wrote on 2011-12-01:

Beware that ctypes may be broken in other ways on armhf as well; in particular it uses libffi to do its binding and a while ago when I looked I came to the conclusion it probably won't call variadic functions correctly if they are passed FP values.

My post to the ctypes list:
http://permalink.gmane.org/gmane.comp.python.ctypes/4657

Revision history for this message

Launchpad Janitor (janitor) wrote on 2011-12-01:

This bug was fixed in the package python2.7 - 2.7.2-8

---------------
python2.7 (2.7.2-8) unstable; urgency=low

  * Update to 20111130, taken from the 2.7 branch.
  * New patch, ctypes-arm, allow for ",hard-float" after libc6 in ldconfig -p
    output (Loic Minier). LP: #898172.
  * debian/rules: Define DPKG_VARS (Alban Browaeys). Closes: #647419).
  * Add python-config man page (Johann Felix Soden). Closes: #650181).

python2.7 (2.7.2-7) unstable; urgency=low

  * Adjust patches for removed Lib/plat-linux3.
  * Add build conflict to libncurses5-dev, let configure search for
    ncurses headers in /usr/include/ncursesw too.

python2.7 (2.7.2-6) unstable; urgency=low

  * Update to 20111004, taken from the 2.7 branch.
  * Use the ncursesw include directory when linking with ncursesw.
  * Rebuild with libreadline not linked with libncurses*. Closes: #643816.
  * Fix typos in the multiprocessing module. Closes: #643856.
-- Matthias Klose <email address hidden> Thu, 01 Dec 2011 12:40:07 +0000