Basic C++ function to Python via Cython

Question

I have a very basic setup to experiment on how to expose a C++ function to Python via Cython. However, I keep getting the following error. What am I missing?

foo.obj : error LNK2001: unresolved external symbol cppFoo
C:\git\cythonTest\foo.cp38-win_amd64.pyd : fatal error LNK1120: 1 unresolved externals

cppFoo.h

#ifndef FOO_H
#define FOO_H

double cppFoo(double x, int y);

#endif

cppFoo.cpp

#include "cppFoo.h"

double cppFoo(double x, int y)
{
    return 2 * x + y;
}

cfoo.pxd

cdef extern from "cppFoo.h":
    double cppFoo(double x, int y)

foo.pyx

from cfoo cimport cppFoo

def pyFoo(double x, int y):
    return cppFoo(x, y)

setup.py

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

setup(ext_modules=cythonize("foo.pyx"), requires=['Cython'])

Running with python setup.py clean build_ext --inplace.

Does this answer your question? C++ Fatal Error LNK1120: 1 unresolved externals — l'L'l
– l'L'l, Commented Jan 11, 2020 at 4:25
Not really. Although perhaps it does and I'm too dumb to realize it. — foreignvol
– foreignvol, Commented Jan 11, 2020 at 4:34
I've tried (i) not doing anything and simply calling the python command at the end of the post and (ii) compile it first with gcc -c cppFoo.cpp and then compile the cython stuff. However, both give me the same error. — foreignvol
– foreignvol, Commented Jan 11, 2020 at 4:47

foreignvol · Accepted Answer · 2020-01-11 04:55:18Z

1

I found a solution. cppFoo.cpp was not being recognized as a source file. Adding the following line at the top of foo.pyx was enough.

# distutils: sources = cppFoo.cpp

answered Jan 11, 2020 at 4:55

foreignvol

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