[Pythonmac-SIG] Module build fails because distutils adds "-isysroot"

[Patrick Näf]

Hi folks

I'm currently writing a very simple Python module in C that provides an
interface to libaprutil's MD5 routines. I compile my module using
distutils, as per instructions in the "Building C and C++ Extensions with
distutils" chapter of the official Python docs.

Since Mac OS X has libaprutil pre-installed, it seems natural that I try
to use the system version of the library. My Python module's .c file
therefore contains the following #include directive:

  #include <apr-1/apr_md5.h>

Everything works fine (module compiles and I can use it) as long as I use
the system version of Python (2.5.1) to compile the module. The problem is
that I *really* need to build the module with Python 2.6 or newer, and
this is where my trouble starts. I have Python 3.1.1 installed in
/Library/Frameworks/Python, and with this version of Python my module's
build fails miserably, like this:

tharbad:~ patrick$
/Library/Frameworks/Python.framework/Versions/3.1/bin/python3.1 ./setup.py
build_ext --inplace
running build_ext
building 'aprmd5' extension
gcc -arch ppc -arch i386 -isysroot /Developer/SDKs/MacOSX10.4u.sdk
-fno-strict-aliasing -fno-common -dynamic -DNDEBUG -g -O3
-I/Library/Frameworks/Python.framework/Versions/3.1/include/python3.1 -c
aprmd5.c -o build/temp.macosx-10.3-fat-3.1/aprmd5.o
aprmd5.c:43:60: aprmd5.c:43:60: error: apr-1/apr_md5.h: No such file or
directory
[...]

The problem here is that the gcc option "-isysroot" moves the root for
system includes to the SDK directory (/Developer/SDKs/MacOSX10.4u.sdk),
away from the normal root (/). Unfortunately, the SDK does not contain the
header <apr-1/apr_md5.h>, which causes the build to fail. Where does
"-isysroot" come from? Not from my module, it's added automatically by
distutils.

I believe I have correctly diagnosed the problem, and I can certainly work
around it *somehow* in my module, but since I am rather new to Python I
have trouble deciding on a solution that is appropriate. I am therefore
writing to this list, hoping someone reading this can give me some advice.

1) Is my problem a known situation for which there is a generally
accepted, best-practice solution? If so, a pointer in the right direction
would be most welcome. If not, what would seem to be a good solution? Make
my own build of libaprutil using the MacOSX10.4u SDK? Rely on a
third-party build of libaprutil (e.g. fink)? Force the compiler to use the
system's libaprutil?

2) Is this a bug in the MacOSX10.4u SDK, i.e. should the SDK contain the
headers for libaprutil? This seems possible to me, because the SDK
certainly contains headers for other libraries (e.g. openssl), so why not
for libaprutil?

3) Is this a bug in the Python distribution, i.e. should the Python 3.1.1
distutils *not* add "-isysroot"? I think this is not the case, distutils
should add the option because Python probably was built with the SDK.

4) Is my work obsolete because someone already has written a Python module
that interfaces libaprutil and has solved all of my problems? If this is
so, again, pointers would be very welcome.


Thanks for your time
Patrick


System setup:
- Mac OS X 10.5.8 (includes libaprutil 1.2.7)
- gcc --version: powerpc-apple-darwin9-gcc-4.0.1 (GCC) 4.0.1 (Apple Inc.
build 5493)
- Yes, I *do* have the MacOSX10.4u SDK installed :-)
- Python 3.1.1, downloaded from
http://www.python.org/ftp/python/3.1.1/python-3.1.1.dmg (I have also tried
Python 2.6.2 and 3.0.1, with the same result)