Python CMakeLists incorrectly determines PYTHON_LIB_DIR

[tallpgr]

The current Python/CMakeLists.txt is responsible for setting the destination directory of the shared python library PyHSPlasma.so. It currently does so by executing a Python code snippet obtaining the value of distutils.sysconfig.get_python_lib().

Unfortunately it does so with a call to that routine with no arguments, which sets PYTHON_LIB_DIR to the installation directory of the currently running Python interpreter.

While that may be appropriate for building/installing as a manner of installing HSPlasma for the machine performing the build, it becomes inappropriate when HSPlasma is being built in a build environment such as Jenkins, where the Jenkins build process attempts to do a make install with CMAKE_INSTALL_PREFIX set to a non-live destination. If the build is performed (as it should be) in Jenkins under a non-privileged user, the make install operation will attempt to install PyHSPlasma.so into the working Python library directories, and fail because of privileges. As it should. If for no other reason than that make install ignored CMAKE_INSTALL_PREFIX.

I am suggesting for the NOT WIN32 situation to alter your snippet to use

get_python_lib(prefix='${CMAKE_INSTALL_PREFIX}')

instead of the base get_python_lib() call. This will properly pick up the destination for the Python library in an isolated build environment.

-rarified