[BUG] Building Cython extension on Windows triggers TypeError

[daniel-larraz]

setuptools version

setuptools==70.2.0

Python version

Python 3.12

OS

Windows

Additional environment information

MSYS2 MINGW64

Description

Version 70.2.0 triggers a TypeError: unsupported operand type(s) for +: 'NoneType' and 'str' when building a Cython extension on Windows using MSYS2 MINGW64. Previous versions of setuptools work fine.

Expected behavior

The Cython extension should build successfully without any errors.

How to Reproduce

1. Create a directory with three files helloworld.pyx, setup.py, and setup.cfg:

# helloworld.pyx
print("Hello World")

# setup.py
from setuptools import setup
from Cython.Build import cythonize

setup(
    ext_modules = cythonize("helloworld.pyx")
)

# setup.cfg
[build]
compiler = mingw32

3. Launch a MINGW64 environment and go to the directory above.
4. Run: C:\path\to\python.exe setup.py build_ext --inplace

Output

running build_ext
Traceback (most recent call last):
  File "C:\Users\Daniel\Desktop\reproducer\setup.py", line 4, in <module>
    setup(
  File "C:\Users\Daniel\AppData\Local\Programs\Python\Python312\Lib\site-packages\setuptools\__init__.py", line 103, in setup
    return distutils.core.setup(**attrs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\Daniel\AppData\Local\Programs\Python\Python312\Lib\site-packages\setuptools\_distutils\core.py", line 184, in setup
    return run_commands(dist)
           ^^^^^^^^^^^^^^^^^^
  File "C:\Users\Daniel\AppData\Local\Programs\Python\Python312\Lib\site-packages\setuptools\_distutils\core.py", line 200, in run_commands
    dist.run_commands()
  File "C:\Users\Daniel\AppData\Local\Programs\Python\Python312\Lib\site-packages\setuptools\_distutils\dist.py", line 970, in run_commands
    self.run_command(cmd)
  File "C:\Users\Daniel\AppData\Local\Programs\Python\Python312\Lib\site-packages\setuptools\dist.py", line 974, in run_command
    super().run_command(command)
  File "C:\Users\Daniel\AppData\Local\Programs\Python\Python312\Lib\site-packages\setuptools\_distutils\dist.py", line 989, in run_command
    cmd_obj.run()
  File "C:\Users\Daniel\AppData\Local\Programs\Python\Python312\Lib\site-packages\setuptools\command\build_ext.py", line 93, in run
    _build_ext.run(self)
  File "C:\Users\Daniel\AppData\Local\Programs\Python\Python312\Lib\site-packages\setuptools\_distutils\command\build_ext.py", line 329, in run
    customize_compiler(self.compiler)
  File "C:\Users\Daniel\AppData\Local\Programs\Python\Python312\Lib\site-packages\setuptools\_distutils\sysconfig.py", line 333, in customize_compiler
    cpp = cc + " -E"  # not always
          ~~~^~~~~~~
TypeError: unsupported operand type(s) for +: 'NoneType' and 'str'

[abravalheri]

If I am not mistaken the cc variable comes from sysconfig.get_config_var('CC') (and/or the CC environment variable).

@daniel-larraz what is the return value of sysconfig.get_config_var('CC')? And is there any CC environment variable set (what is the output of os.environ['CC'])?

[daniel-larraz]

The return value of sysconfig.get_config_var('CC') is None. There is no CC environment variable set.

[lazka]

I assume you are using the official CPython build?

Due to 2ad8784 I guess.

Previously customize_compiler() was skipped in that setup.

Two options:

1. Guard customize_compiler() to not run with the official CPython like before (that means it will ignore env vars again, like CFLAGS etc)
2. Make customize_compiler() compatible to work with the official CPython (i.e. add some None checks)

I personally tend towards (2).

(this could be moved to distutils)

[daniel-larraz]

Yes, I'm using the official CPython build.

[abravalheri]

@jaraco would it be possible to transfer this issue to pypa/distutils as indicated in laska's analysis in #268.

@naveen521kk, would it be possible to help with this problem (as a potential unintended consequence of #184)?

[lazka]

I can reproduce the error locally, by patching the distutils test suite to default to GCC even for msvc CPython. The test suite passes otherwise.

FAILED distutils/tests/test_build_ext.py::TestBuildExt::test_build_ext - TypeError: unsupported operand type(s) for +: 'NoneType' and 'str'
FAILED distutils/tests/test_build_ext.py::TestBuildExt::test_optional_extension - TypeError: unsupported operand type(s) for +: 'NoneType' and 'str'
FAILED distutils/tests/test_build_ext.py::TestBuildExt::test_get_outputs - TypeError: unsupported operand type(s) for +: 'NoneType' and 'str'
FAILED distutils/tests/test_build_ext.py::TestParallelBuildExt::test_build_ext - TypeError: unsupported operand type(s) for +: 'NoneType' and 'str'
FAILED distutils/tests/test_build_ext.py::TestParallelBuildExt::test_optional_extension - TypeError: unsupported operand type(s) for +: 'NoneType' and 'str'
FAILED distutils/tests/test_build_ext.py::TestParallelBuildExt::test_get_outputs - TypeError: unsupported operand type(s) for +: 'NoneType' and 'str'
FAILED distutils/tests/test_ccompiler.py::test_has_function_prototype - AssertionError: assert False
FAILED distutils/tests/test_install.py::TestInstall::test_record_extensions - TypeError: unsupported operand type(s) for +: 'NoneType' and 'str'

[lazka]

I've created #267

I went with option (1), since (2) turned out to be not possible without major changes.

[jan-david-fischbach]

+1