building shared library from D code to import into cython

[Laeeth Isharc via Digitalmars-d-learn]

Hi.

I am trying to create a shared library in D linked against phobos 
so that I may use this in a cython extension module for Python.  
Ultimately I would like to be able to use a D class or struct 
(via the C++ interface) and call it from within cython, since 
cython classes cannot be instantiated without the gil (and this 
prevents easy parallelisation).

I feel a bit foolish asking the question as there is a nice 
example here for working with plain C using dmd as the linker, 
and using dmd and gcc to create a DMD shared library statically 
linked to phobos.  However, I have not succeeded in creating a D 
library statically linked to phobos that works with cython and 
python,
http://dlang.org/dll-linux.html#dso7

I tried it first with test C code to make sure I am able to get 
the C library/cython/Python interaction working.

pytest.c:
#include <stdio.h>

long pytest(long a)
{
        return a+1;
}

int main()
{
        long a =pytest(100);
        printf("%ld",a);
        return 0;
}


pytestpy.pyx:
cdef extern long pytest(long a)

cpdef pytestpy():
        return pytest(109)


setup.py:

from distutils.core import setup
from distutils.extension import Extension
from Cython.Build import cythonize

setup(
                ext_modules = cythonize([
                                 Extension("pytestpy", ["pytestpy.pyx"],
                                libraries=["pytest"],
                                )
        ]))


command line:
gcc -shared -o libpytest.so pytest.o
python setup.py build_ext -i
<copied libpytest.so to /usr/local/lib>
python
import pytestpy
pytestpy.pytestpy()
<it works>

----
now try pytest.d
import std.stdio;

extern (C) long pytest(long a)
{
        return a*2;
}

void main()
{
        auto a =pytest(100);
        writefln("%d",a);
}

command line:
rm pytestd.o
rm libpytest.so
rm /usr/local/lib/libpytest.so
dmd -c pytest.d -fPIC
gcc -shared -o libpytest.so pytest.o -defaultlib=libphobos2.so 
-L-rpath=/usr/local/lib
python

import pytestpy
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: /usr/local/lib/libpytest.so: undefined symbol: 
_D3std5stdio12__ModuleInfoZ


I guess it is not linking to the D runtime, but I am not sure 
what I should be doing to fix.

Any thoughts appreciated.

(The next step I was going to try when this works was C++ 
interface vs importing as a Cython class, but I thought best to 
start simple).

I am running this on 64 bit Fedora 20.

Thanks.


Laeeth.