make check on MacOS X

[BrunoDutertre]

'make check' can be made to work on a Mac but it's hard.

Several issues get in the way:

• pip doesn't work with the default system python because of openssl issues (don't know
  when that stopped working).

• it's common to have several versions of python but they have to be installed outside of
  /usr/bin and /usr/lib where the system python lives.

• the CMAKE find_package(PythonLibs) is not reliable. It may find /usr/lib/libpython2.7.dylib
  (i.e., the system version) instead of the version one actually wants.

The only way I got it to work is by finding the right library and forcing cmake to use it:

cmake -DPYTHON_LIBRARY=/Library/Frameworks/Python.framework/Versions/2.7/lib/libpython2.7.dylib
-DPYTHON_INCLUDE_DIR=/Library/Frameworks/Python.framework/Versions/2.7/include/python2.7

[dddejan]

Yes, python seems to be a mess on Mac.

[ianamason]

But in general on a Mac you do not want to be using the system python, especially since you need to install some extra packages. I currently can't do a make check on my python2 machine.
No problems on my python3 machine. I will update once I solve this.

[ianamason]

After a

brew install python@2

and a

pip2 install sympy

I did

cmake -DPYTHON_LIBRARY=/usr/local/Cellar/python@2/2.7.16_1/Frameworks/Python.framework/Versions/2.7/lib/libpython2.7.dylib -DPYTHON_INCLUDE_DIR=/usr/local/Cellar/python@2/2.7.16_1/Frameworks/Python.framework/Versions/2.7/include/python2.7 ..

and make check succeeded without any failures.

On my other laptop, where I only have a brew version of python3 the make check worked out of the box, once I ported the libpoly/python and libpoly/tests to python3.

I have a couple of loose ends to tie up today, but I should be able to make a pull request with the port shortly.

[BrunoDutertre]

Make sure it works for people who don't use brew.

[ianamason]

And for contrast, without specifying the PYTHON_LIBRARY and PYTHON_INCLUDE_DIR, it
finds a python and dynamic library that don't match and the make check crashes with

Fatal Python error: PyThreadState_Get: no current thread

I will look into the what happens to people who try and use the system python (contrary to Apple's advice), once the port is over.

[dddejan]

I tried some cmake hack. Can you guys check if this works.

[ianamason]

OK will try out now ...

Nope:

-- Found PythonInterp: /usr/local/opt/python@2/bin/python (found version "2.7.16")
-- Found PythonLibs: /usr/lib/libpython2.7.dylib (found version "2.7.16")

[dddejan]

But does it crash? (Fatal Python error: PyThreadState_Get: no current thread)

[ianamason]

Amazing! No it doesn't crash. What sort of magic is this?

[ianamason]

OK after my beach walk I will pull this into my python3 branch and see if it works there too.

[ianamason]

facebook magic :-(

[dddejan]

Ok, so I changed cmake to do the following:

• find python interpreter
• use the interpreter to get the headers location This doesn't work, reverted.
• link polypy to load python libraries at runtime as opposed to the one it was compiled with