Bug#831442: mpich: Broken /usr/lib/libmpich.so.12 symlink, depending on installation order

[Nicholas Breen]

Source: mpich
Version: 3.2-6
Severity: important

A symlink /usr/lib/libmpich.so.12 is created only depending on what order the
packages libmpich12 and libmpich-dev are installed in, apparently requiring
libmpich-dev to be unpacked before libmpich12 is configured.  In a clean
chroot:

  # dpkg --purge libmpich12 libmpich-dev
  # apt-get install libmpich12
  # apt-get install libmpich-dev
  # ls -l /usr/lib/libmpich.so.12
  ls: cannot access '/usr/lib/libmpich.so.12': No such file or directory

  # dpkg --purge libmpich12 libmpich-dev
  # apt-get install libmpich12 libmpich-dev
  # ls -l /usr/lib/libmpich.so.12
  lrwxrwxrwx 1 root root 9 Jul 16 05:12 /usr/lib/libmpich.so.12 -> libmpi.so

Because libmpi.so is part of the update-alternatives group with OpenMPI,
problems can result when they're both installed:

  # readlink -f /usr/lib/libmpich.so.12
  /usr/lib/x86_64-linux-gnu/libmpich.so.12.1.0
  # apt-get install libopenmpi-dev
  # readlink -f /usr/lib/libmpich.so.12
  /usr/lib/openmpi/lib/libmpi.so.12.0.3

This hits any package that builds against both MPI variants, causing failures
in dpkg-shlibdeps when it can't find MPICH symbols in /usr/lib/libmpich.so.12:
it's responsible for a FTBFS bug on yorick [1] and a whole bunch of build
failures on gromacs in experimental [2].  I don't know why it's suddenly a
problem now, but the buildds now seem to be installing the packages in the
order that triggers this problem more often than not.


-- 
Nicholas Breen
nbreen at debian.org


[1] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=831406
[2] https://buildd.debian.org/status/fetch.php?pkg=gromacs&arch=amd64&ver=2016%7Erc1-2&stamp=1468635513
    (also on eight other architectures and counting)