In distutils/_msvccompiler.object_filenames, the source's filename is repeated into the temp directory, so if the source file is a/b/c/d/e/f/source.c that whole hierarchy will be repeated into temp-platformname, unless the strip_dir argument is not False. When we run the tests, the starting directory is already quite long on windows, it might be something like C:\Users\VssAdministrator\AppData\Local\Temp\pytest-of-VssAdministrator\pytest-0\test_cython0\random\_examples\cython, so the final output directory is C:\Users\VssAdministrator\AppData\Local\Temp\pytest-of-VssAdministrator\pytest-0\test_cython0\random\_examples\cython\build\temp.win-amd64-3.9\Release\Users\VssAdministrator\AppData\Local\Temp\pytest-of-VssAdministrator\pytest-0\test_cython0\random\_examples\cython.

I think this is too long for windows to handle. I propose to shorten the source file name, so it will not include the full path.