Newbie Developing a Python Extension

[Carl Banks]

Jeremy wrote:
> Hi,
>
> I have been working on Linux 2.6.9 to adapt a C++ module to work as a Python
> extension with the following setup.py file:
>
> from distutils.core import setup, Extension
>
> sm=Extension(
>  'tdma',
>  define_macros=[('__USE_POSIX199309','1')],
>  include_dirs=['/usr/include','/usr/include/python2.3'],
>  library_dirs=['/usr/lib'],
>  sources=['Bitstrea.cpp','bytequeu.cpp','debug.cpp','dlist.cpp',
>   'GrPort.cpp','IoPort.cpp','LMEmu.cpp','LMEmuPdu.cpp',
>   'MacPyIf.cpp','per_os_clk.cpp','timer.cpp'])
>
> setup(name='MySm',
>  version='0.1.0',
>  description='TDMA MAC',
>  ext_modules=[sm])
>
> The extension uses the POSIX call clock_gettime() and things seem fine when
> generating the tdma.so file. However, when running the Python program, at a
> line 'from tdma import init,txdn,txup,...', I get an error message saying
> 'ImportError: /home/.../tdma.so: undefined symbol: clock_gettime'.

You're missing a library.  From the clock_gettime man page:

NOTE
       Most  systems  require  the program be linked with the librt
library to
       use these functions.

So you need to build the extention with librt.  Try adding a 'libraries
= ['rt']' option to the extension definition.  (Unfortunately, on
Linux, builduing a shared object without specifying libraries needed
passes silently.  It'd be nice if there was an option to require all
undefined non-Python symbols to be accounted for by some library, but
that would be a lot of work to implement.)


Carl Banks