Building python extensions on Snow Leopard
2010-08-06
I ran into some problems while I was trying to install python bindings for the Growl notification framework on my MacBook Pro. My Mac is running the current release of Snow Leopard ( 10.6.4 ) and I'm using a python.org installed binary package of python, under /usr/local/python. Building using distutils and the supplied setup.py failed, seemingly because the compiler was unable to find quite routine include files, such as stdarg.h and float.h .
/Developer/SDKs/MacOSX10.4u.sdk/usr/include/stdarg.h:4:25: error: stdarg.h: No such file or directory
This error message both confused and perturbed me, because stdarg is a fairly fundamental component of a working C library, and I am pretty certain that my compiler isn't that fundamentally broken.
Picking apart the build output from the generated Makefile, I see that it is setting the -isysroot gcc flag, to /Developer/SDKs/MacOSX10.4u.sdk/ . I presume this is because the python installation is built to use the OS X 10.4 compatability SDK. This is why it's pulling in /Developer/SDKs/MacOSX10.4u.sdk/usr/include/stdarg.h . That header is a stub, and included the following stanza
/* GCC uses its own copy of this header */
#if defined(GNUC)
#include_next
#include_next is a gcc extension to cpp, and instructs the preprocessor to start searching for the include file again starting with the next directory on the include path after this one. Standard libraries like stdarg and float can be quite compiler specific, and as the comment indicates, GCC is expected to have it's own copy of this header file, which would be put away somewhere under /usr/lib/gcc .
At this point, a nagging memory of building cocoa apps with XCode resurfaced, suggesting that the 10.4 SDK isn't compatible with gcc-4.2 ( the system default gcc under snow leopard ). GCC 4.0 is supplied though, for use with building against legacy SDKs. On this whim, I tried exporting CC=/usr/bin/gcc-4.0 and rebuilding, and everything worked as it should.
From inspection, it seems like the snow supplied leopard python is built to use 10.6 SDKs and gcc-4.2 and may well be a more sensible python to use. Further googling ducking , turned up this bug report .