[ros-release] Is there a reason why dependencies get broken so often with ROS packages?

Tully Foote tfoote at osrfoundation.org
Fri May 23 20:56:50 UTC 2014

On Fri, May 23, 2014 at 12:41 PM, Jonathan Bohren <jonathan.bohren at gmail.com
> wrote:

> On Fri, May 23, 2014 at 3:30 PM, Tully Foote <tfoote at osrfoundation.org>wrote:
>> Can you clarify a little bit more about what you mean about conflicting
>> dependencies? The only known issues have been related to upstream debian
>> packages we depend upon which have changed.
> This has been mostly with students who aren't too familiar with the way
> debian package dependencies work. They try to install a new package after
> not upgrading for a while, and they get errors about broken package
> dependencies.

If you fail to update before you try to upgrade or install new packages,
that behavior is inherent to the apt system. The problem is that if your
database is out of date it will refer to old files in the repository. If
nothing has been released everything will work.  Assuming you try to
install foo which depends on bar, neither of which have been installed, if
either foo or bar have been released since you apt-get updated, apt will
fail. And if only bar has been updated it will fail to fetch it from the
old url and say the very generic failure message  along the lines of "bar
requested but is not going to be installed"

For ROS this is more noteable than Ubuntu or Debian as we have a lot of
patch releases made by maintainers. The chance that any Ubuntu package has
been updated in a given month is close to zero. For a ROS package it's very
much non-zero thanks to our very responsive maintainers!

>  Also if you are on shadow-fixed this is possible as we sometimes roll
>> back releases in that repo.
> Nope, this has been with the standard public repos.
>> And as Mike mentioned dist-upgrade is required if there are new
>> dependencies added.
>> I don't know of anything in the ROS release system itself has nothing
>> inherently causing conflicts except that it's very active with a large user
>> base making many releases.
> Yeah, I suspect that's all it is. I've recommended to people here at
> Hopkins to always update their ROS packages when they see there are updates
> available. This is reasonable since it's rare that a
> non-backwards-compatible changes make it into stable releases.

That's a reasonable recommendation. It's more than is necessary to fix the
above problem, that just requires an apt-get update, not a upgrade.


PS The list is now consistent with ros-users with reply to list being the

 If you have some examples we can take a closer look at what caused them.
> It's hard. Usually it happens when you don't run `apt-get upgrade` for a
> month or two. Next time it happens I'll get more information from the
> student who runs into the problem.
> -j
> --
> Jonathan Bohren
> Laboratory for Computational Sensing and Robotics
> http://dscl.lcsr.jhu.edu/People/JonathanBohren
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