Import error GLIBCXX_3.4.21 not found when importing numbuf.

[robertnishihara]

I followed the installation instructions on a fresh Ubuntu VM using Anaconda with Python 3 (though I am pretty sure I have seen this error with Python 2 as well).

Ray builds and installs fine. However, if I try to run runtest.py (or simply import numbuf), I get the following error.

Traceback (most recent call last):
  File "test/runtest.py", line 6, in <module>
    import ray
  File "/home/ubuntu/ray/lib/python/ray/__init__.py", line 16, in <module>
    import ray.serialization
  File "/home/ubuntu/ray/lib/python/ray/serialization.py", line 6, in <module>
    import numbuf
  File "/home/ubuntu/anaconda3/lib/python3.5/site-packages/numbuf-0.0.1-py3.5.egg/numbuf/__init__.py", line 5, in <module>
    from numbuf.libnumbuf import *
ImportError: /home/ubuntu/anaconda3/bin/../lib/libstdc++.so.6: version `GLIBCXX_3.4.21' not found (required by /home/ubuntu/anaconda3/lib/python3.5/site-packages/numbuf-0.0.1-py3.5.egg/numbuf/libnumbuf.so)

I followed one of the solutions here http://askubuntu.com/questions/575505/glibcxx-3-4-20-not-found-how-to-fix-this-error, which suggested running the following.

conda install libgcc

That fixed the problem.

Should we specifically look for this error and print something more helpful? Or should we change the installation instructions to mention this potential problem?

[mehrdadn]

IMO it's always better to assume no one will read the instructions. :)

[robertnishihara]

Good point.

Feels a bit hacky, but we could edit numbuf/numbuf/__init__.py to be something like

try:
  from numbuf.libnumbuf import *
except ImportError as e:
  if "GLIBCXX" in str(e):
    raise ImportError("SOME ERROR MESSAGE... Try running `conda install libgcc`.")

[mehrdadn]

That'd probably work. But always print the original error message too; don't suppress it.

[robertnishihara]

Agreed.