gdb embeds python3.3, but support scripts are not compatible

[Russell Power]

The saucy gdb appears to be linked against libpython3.3.

This results in a conflict when trying to debug python2.7 programs, which use the python2.7-dbg.py scripts from python2.7-dbg. This makes debugging Python programs difficult.

  File "/usr/lib/debug/usr/bin/python2.7-gdb.py", line 54
    Py_TPFLAGS_HEAPTYPE = (1L << 9)
                            ^
SyntaxError: invalid syntax
  File "/usr/lib/debug/usr/bin/python2.7-gdb.py", line 54
    Py_TPFLAGS_HEAPTYPE = (1L << 9)

There are also invalid print statements that show up as well.

If these are updated, then the file parses, but `py-bt` fails with:

Error occurred in Python command: global name 'long' is not defined

Updating all of the long() references to int() doesn't work:

Error occurred in Python command: 'gdb.Value' object cannot be interpreted as an integer

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[David Coles (dcoles)]

Looks like the cause of the "'gdb.Value' object cannot be interpreted as an integer" error is the range function not being able to turn a gdb.Value into an int. Put an explicit `int(val)` in there and I can get py-bt and py-list to work again.

I've attached a patch with the changes I've made, but I want to check that this doesn't break Python 2.7 support and clean it up a bit more (pretty sure that `long` and `int` have been unified for a while now) before submitting this upstream.

[Ubuntu Foundations Team Bug Bot (crichton)]

The attachment "Python 3 support" seems to be a patch. If it isn't, please remove the "patch" flag from the attachment, remove the "patch" tag, and if you are a member of the ~ubuntu-reviewers, unsubscribe the team.

[This is an automated message performed by a Launchpad user owned by ~brian-murray, for any issues please contact him.]

[Matthias Klose (doko)]

please attach the patch to the upstream issue as well.

[Steve Langasek (vorlon)]

jtaylor points out on IRC that fixing the syntax with 2to3 is insufficient to make this actually work.

Test case:

  $ sudo apt-get install python3-dbg gdb
  $ 2to3 /usr/lib/debug/usr/bin/python3.3m-gdb.py > /tmp/python-gdb.patch
  $ cd / && sudo patch -p0 < /tmp/python-gdb.patch
  $ gdb --args python3-dbg /usr/bin/lsb_release
  (gdb) break PyTuple_Size
  (gdb) run
  (gdb) bt

With gdb compiled for python3, instead of getting useful python information in the backtrace, you get python exceptions:

(gdb) bt
#0 PyTuple_Size (
    op=(None, <code at remote 0x7ffff7fe8340>, '_make_relax_case.<locals>._relax_case', <code at remote 0x7ffff7fe8400>)) at ../Objects/tupleobject.c:127
#1 0x00000000006567c0 in PyFunction_NewWithQualName (
Python Exception <class 'AttributeError'> 'PyDictObjectPtr' object has no attribute 'items':
    code=<code at remote 0x7ffff7fe84c0>, globals=,
    qualname='_make_relax_case') at ../Objects/funcobject.c:29
Python Exception <class 'TypeError'> 'gdb.Value' object cannot be interpreted as an integer:
<snip>

so this seems to need some further help.

[Steve Langasek (vorlon)]

jtaylor clarified that he had managed to misapply the patch from the upstream bug, and if it's applied correctly gdb works without generating python exceptions.

[Peter Feiner (pete5)]

For anybody that's too impatient to wait for the saucy packages to be updated, here's how you apply the patch yourself:

wget -O - http://hg.python.org/cpython/raw-file/ef4636faf8bd/Tools/gdb/libpython.py | sudo tee /usr/lib/debug/usr/bin/python2.7-gdb.py

wget -O - http://hg.python.org/cpython/raw-file/752db82b7933/Tools/gdb/libpython.py | sudo tee /usr/lib/debug/usr/bin/python3.3m-gdb.py

[Matthias Klose (doko)]

fixed in trusty and utopic

[Rolf Leggewie (r0lf)]

saucy has seen the end of its life and is no longer receiving any updates. Marking the saucy task for this ticket as "Won't Fix".

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/python-tripleoclient 0.0.10 release.