How to compile __init__.py file using cython on Windows

Question

When I compile an arbitrary __init__.py file on Windows with setup.py build_ext --inplace command, it has an unresolvable external symbol error (i.e. "LINK

Answer 1

This is a very tentative answer because I have no easy way of testing it on Windows, so if it's wrong then let me know and I'll delete it.

Can you try running (on the commend line):

C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Tools\MSVC\14.16.27023\bin\HostX86\x64\link.exe /nologo /INCREMENTAL:NO /LTCG /DLL /MANIFEST:EMBED,ID=2 /MANIFESTUAC:NO /LIBPATH:d:\py37\Libs /LIBPATH:D:\ENVS\cpytrantest\libs /LIBPATH:D:\ENVS\cpytrantest\PCbuild\amd64 "/LIBPATH:C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Tools\MSVC\14.16.27023\lib\x64" "/LIBPATH:C:\Program Files (x86)\Windows Kits\NETFXSDK\4.6.1\lib\um\x64" "/LIBPATH:C:\Program Files (x86)\Windows Kits\10\lib\10.0.18362.0\ucrt\x64" "/LIBPATH:C:\Program Files (x86)\Windows Kits\10\lib\10.0.18362.0\um\x64" /EXPORT:PyInit_ctest build\temp.win-amd64-3.7\Release\ctest/__init__.obj /OUT:C:\Users\76923\Desktop\cpythonrecord\ctest\__init__.cp37-win_amd64.pyd /IMPLIB:build\temp.win-md64-3.7\Release\ctest\__init__.cp37-win_amd64.lib

All I've done is taken the compilation command that distutils generated and replaced /EXPORT:PyInit___init__ with /EXPORT:PyInit_ctest. The /EXPORT is a Windows specific compiler option that doesn't get added on Linux. It looks like either distutils or Cython passes the name PyInit___init__ to MSVC, but if I look in the actual generated C file then the name appears to be PyInit_ctest, hence the undefined symbol.

If that workaround (doing the compilation independently of distutils) works then you should report the bug to either the distutils or the Cython bug tracker (probably Cython) with these details and hopefully it can be fixed.