I seem to have messed up something with a manual
gcc update sometime in the past, which didn't become a problem until today, when I upgraded from 14.04 to 16.04. Namely, the system seems to think that the
libstdc++6 version is OK, while
apt (and many other programs) complain it isn't (because the shared library is actually in the wrong version):
sudo apt-get install --fix-broken --fix-missing apt-get: relocation error: /usr/lib/x86_64-linux-gnu/libapt-pkg.so.5.0: symbol _ZNKSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEE7compareERKS4_, version GLIBCXX_3.4.21 not defined in file libstdc++.so.6 with link time reference
The system doesn't even start a graphical mode, the above output was obtained using a non-graphical console (using
apt itself is completely unusable, so I can't just do something like a reinstall.
How can I fix and reinstall these packages, when the program I'm using for managing them itself is affected and unusable?