[Numpy-discussion] Questions about cross-compiling extensions for mac-ppc and mac-intel

[Zachary Pincus]

Hi folks,

I've been doing a lot of web-reading on the subject, but have not  
been completely able to synthesize all of the disparate bits of  
advice about building python extensions as Mac-PPC and Mac-Intel fat  
binaries, so I'm turning to the wisdom of this list for a few questions.

My general goal is to make a double-clickable Mac installer of a set  
of tools built around numpy, numpy's distutils, a very hacked-up  
version of PIL, and some fortran code too. To this end, I need to  
figure out how to get the numpy distutils to cross-compile,  
generating PPC code and Intel code in separate builds -- and/or  
generating a universal binary all in one go. (I'd like to distribute  
a universal version of numpy, but I think that my own code needs to  
be built/distributed separately for each architecture due to endian- 
ness issues.)

Is there explicit support in distutils for this, or is it a matter of  
setting the proper environment variables to entice gcc and gfortran  
to generate code for a specific architecture?

One problem is that PIL is a tricky beast, even in the neutered form  
that I'm using it. It does a compile-time check for the endian-ness  
of the system, and a compile-time search for the zlib to use, both of  
which are problematic.

To address the former, I'd like to be able to (say) include something  
like 'config_endian --big' on the 'python setup.py' command-line, and  
have that information trickle down to the PIL config script (a few  
subpackages deep). Is this easy or possible?

To address the latter, I think I need to have the PIL extensions  
dynamically link against '/Developer/SDKs/MacOSX10.4u.sdk/usr/lib/ 
libz.dylib' which is the fat-binary version of the library, using the  
headers from '/Developer/SDKs/MacOSX10.4u.sdk/usr/include/zlib.h
'. Right now, PIL is using system_info from numpy.distutils to find  
the valid library paths on which libz and its headers might live.  
This is nice and more or less platform-neutral, which I like. How  
best should I convince/configure numpy.distutils.system_info to put '/ 
Developer/SDKs/MacOSX10.4u.sdk/usr/{lib,include}' on the output to  
get_include_dirs() and get_lib_dirs()?

Thanks for any advice or counsel,

Zach Pincus

Program in Biomedical Informatics and Department of Biochemistry
Stanford University School of Medicine