[Numpy-discussion] CTypes: How to incorporate a library with shared library module?

[Robert Kern]

On Feb 12, 2008 12:41 AM, Damian Eads <eads at soe.ucsc.edu> wrote:
> Robert Kern wrote:
> > On Feb 12, 2008 12:14 AM, Damian Eads <eads at soe.ucsc.edu> wrote:
> >> David Cournapeau wrote:
> >>> On Mon, 2008-02-11 at 22:50 -0700, Damian Eads wrote:
> >>>> Dear Lou,
> >>>>
> >>>> You may want to try using distutils or setuputils, which makes compiling
> >>>> extensions much easier. It does the hard work of finding out which flags
> >>>> are needed to compile extensions on the host platform. There are many
> >>>> examples on the web on how to use distutils to build C extensions
> >>>> (http://docs.python.org/ext/building.html).
> >>> Unfortunately, this does not work. Distutils only knows how to build
> >>> python extensions, not shared libraries. Depending on the platform, this
> >>> is not the same thing, and mac os X is such a platform where both are
> >>> not the same.
> >>>
> >>> cheers,
> >>>
> >>> David
> >> Really? distutils generates .so files for me, which I assume are shared
> >> libraries. FYI: I'm running Fedora 8 on an x86. Does distutils not
> >> generate a shared library on a mac?
> >
> > Python extension modules are shared libraries, yes. But they must
> > follow a particular format, namely exposing a correct
> > "init<modulename>" function. distutils/setuptools only maked Python
> > extension modules, not arbitrary shared libraries.
>
> Perhaps I was a bit too liberal in my use of the term "extension
> module". Several small libraries for a project at work do not define the
> standard init<modulename> function, and yet they build with distutils. I
> can load them into ctypes without any hitches. Perhaps distutils does
> not check for the presence of the init<modulename> function and required
> data structures? I'll admit I may be abusing distutils by using it for
> something for which it wasn't designed.

Yup. It usually works on Linux because the init<modulename> bit isn't
checked. On Windows, it is, and the build will fail.

-- 
Robert Kern

"I have come to believe that the whole world is an enigma, a harmless
enigma that is made terrible by our own mad attempt to interpret it as
though it had an underlying truth."
  -- Umberto Eco