Can't run or compile anything !!!! -> symbol lookup error: /opt/ros/hydro/lib/libroscpp.so: undefined symbol: _ZN3ros6HeaderC1Ev
it appears that there is an unknown symbol in the libroscpp.so
file, and now catkin can find anything in /opt/ros/hydro/lib/
even though everything is there. No changes were made to the system that I can find, how did this happen and how do I fix it?