Python distutils not using correct version of gcc

Question

I am trying to compile a package on Mac OSX 10.6.5. The package's install script relies on distutils. The problem is that the computer's default gcc is version 4.2 (I determined this by just running gcc --version in a terminal window) but when I run 'python setup.py build', I see from the output that the distutils is choosing gcc-4.0 instead of 4.2 This is a big problem because the code I am using require gcc >= 4.2. I do not have admin rights on this machine, so as a workaroud, I created some symlinks that send gcc-4.0 to gcc-4.2. The result is the code compiles, but the generated .so files do not work (when I try to import them in python, I get errors complaining about a missing init function in the shared object).

I have tried compiling this code on a different mac (10.6.6) and it works like a charm: distutils chooses 4.2 without being forced to do so and I can import the generated shared object without a problem. So, what I would like to do is to compile the code on my computer without having to do this symlink trickery...I just want distutils to choose 4.2 automatically as it should. I have tried taking the .so files that compile properly and transferring them to my computer, but that fails for a number of reasons (they are linked against libraries that are not present on my machine/are a different version that those installed).

Does anyone have any advice here?

Thanks, Josh

Answer 1

To force distutils to use a separate compiler, you can redefine a few variables via the environment. First, find out what distutils is using as defaults:

>>> from distutils import sysconfig
>>> sysconfig.get_config_var('LDSHARED')
'gcc-4.0 -Wl,-F. -bundle -undefined dynamic_lookup'
>>> sysconfig.get_config_var('CC')
'gcc-4.0'

Next you need to redefine those, substituting in the version of gcc you'd like to use:

% LDSHARED="gcc-4.2 -Wl,-F. -bundle -undefined dynamic_lookup" CC=gcc-4.2 \
    /usr/bin/python setup.py build_ext

Keep in mind that the sysconfig defaults are pulled from the Makefile which was originally used to compile python, so fudging with them may produce unintended results:

>>> path = sysconfig.get_python_lib(plat_specific=1, standard_lib=1)
>>> os.path.join(path, 'config', 'Makefile')
'/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/config/Makefile'