Link against Python3::Module

[paulgessinger]

instead of Python3::Python, which according to the documentation is meant for embedding the python interpreter.

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[jmcarcell]

Maybe both?

[paulgessinger]

@jmcarcell Python3::Python hard-adds -lintl in the compiler flags and doesn't propagate correctly in spack, at least on macOS. That breaks the macOS build unfortunately. This change works locally for me on macOS, but clearly has issues in the linux builds. Seems like the spack build produces very different python libraries depending on the platform.

[tmadlener]

I think Python3::Python is correct. Otherwise we get missing symbols see here:

  /cvmfs/sft.cern.ch/lcg/releases/binutils/2.40-acaab/x86_64-el9/bin/ld: src/libpodio.so: undefined reference to `_Py_Dealloc'
  /cvmfs/sft.cern.ch/lcg/releases/binutils/2.40-acaab/x86_64-el9/bin/ld: src/libpodio.so: undefined reference to `PyObject_SetAttrString'
  /cvmfs/sft.cern.ch/lcg/releases/binutils/2.40-acaab/x86_64-el9/bin/ld: src/libpodio.so: undefined reference to `PyCMethod_New'
  /cvmfs/sft.cern.ch/lcg/releases/binutils/2.40-acaab/x86_64-el9/bin/ld: src/libpodio.so: undefined reference to `PyErr_SetString'
  /cvmfs/sft.cern.ch/lcg/releases/binutils/2.40-acaab/x86_64-el9/bin/ld: src/libpodio.so: undefined reference to `PyObject_HasAttrString'
  /cvmfs/sft.cern.ch/lcg/releases/binutils/2.40-acaab/x86_64-el9/bin/ld: src/libpodio.so: undefined reference to `PyInstanceMethod_New'
  /cvmfs/sft.cern.ch/lcg/releases/binutils/2.40-acaab/x86_64-el9/bin/ld: src/libpodio.so: undefined reference to `PyErr_Clear'
  /cvmfs/sft.cern.ch/lcg/releases/binutils/2.40-acaab/x86_64-el9/bin/ld: src/libpodio.so: undefined reference to `_PyObject_CallMethod_SizeT'
  /cvmfs/sft.cern.ch/lcg/releases/binutils/2.40-acaab/x86_64-el9/bin/ld: src/libpodio.so: undefined reference to `PyExc_IndexError'
  /cvmfs/sft.cern.ch/lcg/releases/binutils/2.40-acaab/x86_64-el9/bin/ld: src/libpodio.so: undefined reference to `PyObject_GetAttrString'
  /cvmfs/sft.cern.ch/lcg/releases/binutils/2.40-acaab/x86_64-el9/bin/ld: src/libpodio.so: undefined reference to `PyUnicode_AsUTF8'
  /cvmfs/sft.cern.ch/lcg/releases/binutils/2.40-acaab/x86_64-el9/bin/ld: src/libpodio.so: undefined reference to `PyErr_Occurred'

I get a similar error when trying with this on Ubuntu on top of a spack built python.

[paulgessinger]

@jmcarcell @tmadlener From googling, I think the way this is supposed to work is to ignore unresolved symbols at compile time / link time, and let the runtime linker resolve them when python runs.

I'm investigating.

[tmadlener]

Closing this in favor of #928