Build a Python 64 bit extension on Windows 8

c++ module

2013-07-07 Build a Python 64 bit extension on Windows 8

I was using MinGW on Windows to build a Python extension including C++ code. The 32bit mode was working fine and I was using the following command line:

python setup.by build --compiler=mingw32

I thought it would be easy to run it with the Python 64 bit version. No change would be required. I was a little bit over confident.

Traceback (most recent call last):
  File "setup.py", line 11, in <module>
    author_email  = '...',
  File "c:\python33_x64\lib\distutils\core.py", line 148, in setup
    dist.run_commands()
  File "c:\python33_x64\lib\distutils\dist.py", line 929, in run_commands
    self.run_command(cmd)
  File "c:\python33_x64\lib\distutils\dist.py", line 948, in run_command
    cmd_obj.run()
  File "c:\python33_x64\lib\distutils\command\build_ext.py", line 323, in run
    force=self.force)
  File "c:\python33_x64\lib\distutils\ccompiler.py", line 1034, in new_compiler
    return klass(None, dry_run, force)
  File "c:\python33_x64\lib\distutils\cygwinccompiler.py", line 125, in __init__
    if self.ld_version >= "2.10.90":
TypeError: unorderable types: NoneType() >= str()

I decided to switch to Visual Studio Express 2012 to build my extension. but I went through some error related to the file vcvarsall.bat because Python was not able to find the file vsvars64.bat (for one very good reason, it does not exist). I read some blogs where people suggest to reinstall Visual Studio Express but I did not remember the setup asking me anything about options. When I checked the folder of Visual Studio, I found the following file vcvarsx86_amd64.bat. Then, after some research (stubborness is mandatory for those parts) and some tweaks, I discovered two mistakes in the package distutils. They need to be fixed in the file msvc9compiler.py:

The file uses the version Visual Studio used to compile Python (2010), which is not the version I used, so I manually updated the function get_build_version to get:

            if majorVersion >= 6:
                # pick on of the following line
                majorVersion = 11 # VS 2012
                majorVersion = 12 # VS 2013
                majorVersion = 14 # VS 2015
                return majorVersion + minorVersion

Not the best but it works.

The second modification is at the beginning of the same file which contains:

            PLAT_TO_VCVARS = {
                'win32' : 'x86',
                'win-amd64' : 'amd64',
                'win-ia64' : 'ia64',
            }

The flag amd64 must be replaced by x86_amd64.

After the two modifications, it was working fine with the following command line:

python setup.by build --compiler=msvc --plat-name=win-amd64

And I understood why it was failing without any mysterious new installation. I checked about 64 bit version of MinGW but it looked a longer path than the one I chose. Who knows? You will find some others details here. I wrote a function which import a module written in one single C++ file. If the module does not exist, it compiles it inplace.

As a conclusion, I would say it was difficult to find the proper instructions. Maybe the number of documents related to that issue has increased, or the search engines I used were not able to give me the answer. All I know is I do not want to go through that again even if I know there will be a next time when I update Python or when I change my laptop. I hope next time I face that problem, search engines will show me my own page.

Xavier Dupré

XD blog

2013-07-07 Build a Python 64 bit extension on Windows 8