How to request debug Python build?

Languages Python
1

I tried searching but I couldn’t find any way to ask for, or use, a debug Python build. This is useful as it runs with asserts enabled, and is very helpful for finding bugs in C extension modules.

I tried just calling python-dbg, but is not found in any of the Python 3 versions, and instead falls back to the default command-not-found behaviour (“run apt-get install python-dbg”). However, this is wrong, as Python is installed manually by travis scripts (e.g. “Downloading archive: https://storage.googleapis.com/travis-ci-language-archives/python/binaries/ubuntu/16.04/x86_64/python-3.8.tar.bz2”), and does not match the apt-provided package.

Any ideas?

2

Do you need to debug at Python or at C level?

Or do you rather need to run the entire build in an interactive debug mode (then refer to the link)?

3

python-dbg deb package is for system python 2 (possibly /usr/bin/python).
python3-dbg deb package is for system python 3 (possibly /usr/bin/python3).

If you want to run language: python's python with python-dbg or python-dbg3, make sure if the python is the system python installed by the deb package. I am not sure this case works.

https://packages.ubuntu.com/xenial/python-dbg
https://packages.ubuntu.com/xenial/python3-dbg

Maybe possible case to run Python3 with using deb packages as much as possible.

With language: minimal in .travis.yml,

$ sudo apt-get install python3 python3-dbg python3-something
$ which python3
$ dpkg -S /usr/bin/python3

Or

With language: python and python: 3.6 for example in .travis.yml,

$ python -m pip install dbg something
4

At python interpreter level, so neither actually :slight_smile:

5

Sadly, apt install doesn’t work because with ‘language: python’ and ‘python: 3.8’, python itself doesn’t come from apt, so installing the -dbg package from apt doesn’t work.

But pip install works to install the dbg variant of the interpreter? I’d be surprised, but I’ll look, thanks for the hint.

6

Have no idea what that means. But if you need Python from distro, use language: generic and install one of python*-dbg packages as @junaruga suggested. The executable will be available as python-dbg or python3-dbg (checked that with apt-file list).

Note that you can only get that for python versions provided by the distro. Travis doesn’t provide debug builds.

7

Sadly, apt install doesn’t work because with ‘language: python’ and ‘python: 3.8’, python itself doesn’t come from apt, so installing the -dbg package from apt doesn’t work.

That’s what I supposed. Thanks for sharing your experiment.

But pip install works to install the dbg variant of the interpreter? I’d be surprised, but I’ll look, thanks for the hint.

I see dbg in PyPI. That’s the dbg you are talking about right?

8

Okay, I found that pyenv can install debug versions (pyenv install X.Y.Z -g).

  • It builds versions from source
    • so you are responsible for installing binary dependencies from Apt. You can find their list online though.
    • Add the resulting installation to Travis cache and use e.g. pyenv install -s to avoid rebuilding.
  • Pyenv identifier for debug versions is X.Y.Z-debug so it won’t clash with preinstalled alternative versions
  • Travis has Pyenv installed globally into /opt so need to run pyenv install with sudo.
  • Last time I checked, pip was unable to install packages for a debug Python – at least, in Windows.