[jira] [Created] (ARROW-7041) PythonLibs setting found by CMake uses wrong version of Python on macOS

["Christian Hudon (Jira)" <ji...@apache.org>]

Christian Hudon created ARROW-7041:
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             Summary: PythonLibs setting found by CMake uses wrong version of Python on macOS
                 Key: ARROW-7041
                 URL: https://issues.apache.org/jira/browse/ARROW-7041
             Project: Apache Arrow
          Issue Type: Bug
            Reporter: Christian Hudon


I'm trying to build the Python library and run its tests, so to do that I need to first build the C++ library. I'm going through the Python Development Guide part of the docs. When invoking CMake to build the C++ library, it claims to have found PythonLibs here:

-- Found PythonLibs: /usr/local/Cellar/python@2/2.7.16_1/Frameworks/Python.framework/Versions/2.7/lib/libpython3.7m.dylib

Just by looking at the whole path, it doesn't look like a promising location. And indeed, there's no libpython3.7*.dylib file in the Python 2.7 install directory. So the C++ build fails.

I'm on macOS 10.14.6. I have Python 2.7 and 3.7 both installed via Homebrew. (There is a libpython3.7*.dylib file in the Python 3.7 install of Homebrew.) For the Python build dependencies, I have a Python 3.7 venv active and they are installed there via pip. This happens with -DARROW_PYTHON=ON.

This definitely looks like whatever piece of CMake code that is trying to find PythonLibs is grabbing the first directory it finds, and appending a path to the dylib without looking if it exists. However, I don't know much of anything about CMake. Any suggestion for a fix or at least a workaround to point CMake to the PythonLibs directory that would make more sense?



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