Libmpec-dev not available on debian 12 when building Python

[neochine]

Feature or enhancement

Proposal:

In this guide
https://devguide.python.org/getting-started/setup-building/#build-dependencies
it suggests lib-mpdec but its not available in debian 12? Perhaps its outdated package?

root@v18606:~/cpython# sudo apt-get install build-essential gdb lcov pkg-config \
      libbz2-dev libffi-dev libgdbm-dev libgdbm-compat-dev liblzma-dev \
      libncurses5-dev libreadline6-dev libsqlite3-dev libssl-dev \
      lzma lzma-dev tk-dev uuid-dev zlib1g-dev libmpdec-dev
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
Note, selecting 'libreadline-dev' instead of 'libreadline6-dev'
E: Unable to locate package libmpdec-dev

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

No response

[we-are-all-individuals]

I encountered the same issue. It looks like mpdecimal has been removed solely because dh-sphinxdoc was not happy with the pre-built HTML docs ...

https://groups.google.com/g/linux.debian.bugs.dist/c/IhDtdjrk7mE

The upstream mpdecimal changelog states that the Sphinx documentation is now in a separate package:

https://www.bytereef.org/mpdecimal/changelog.html

Debian should not have any reason not to reinstate the package, it should be trivial. I suggest to ask nicely on the Debian mailing lists and mention that mpdecimal will be assumed to be present in the CPython build process in the future.

[neochine]

Alright. Given I could build python3.12 even without installing that package, it looks not much necessary. I think issue can be closed

[aisk]

The devguide said that mpdecimal is just an optional package for building with optional packages, so it is not required for building Python.

But I think this is still an issue that needs to be fixed.

[devdanzin]

Here's the Debian bug report log for the removal: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1056785

[we-are-all-individuals]

Here's the Debian bug report log for the removal: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1056785

Reading that issue, it looks like the Debian developers are not going to respond there. Perhaps opening an issue against the Debian CPython package will get more attention.

[erlend-aasland]

Note that it is still possible to use the bundled copy using --without-system-libmpdec (IIRC; I'm on mobile). Perhaps we should mention that in the devguide. I'll open an issue on the devguide tracker. Moreover, opening an issue on the Debian tracker to get the libmpdecimal package reinstated sounds like a good idea; I also commented on their tracker, but I received no reply so far.

[erlend-aasland]

FTR, a fallback to the bundled version is added in #119196.