[Python] Cython can't link external library

Part of a Python library I'm working on is written in Cython. I need to use the LinBox C++ library (which depends on the Givaro library). Just to test, I've written a small C++ function that eats Cython-accessible data, does something with Givaro, and returns Cython-accessible data. Everything compiles correctly, but when I run the test, I get the following error:

ImportError: dlopen(<path/to/cython>/matrices.cpython-311-darwin.so, 0x0002): symbol not found in flat namespace '__ZN6GivarolsERSoRKNS_7IntegerE'

Running nm on matrices.cpython-311-darwin.so, it looks like the symbol is undefined, because I get U __ZN6GivarolsERSoRKNS_7IntegerE. Here's my MWE:

// fastcomputation.cpp

#include <vector>
#include <givaro/gfq.h>

using namespace std;

int kernel(vector<int> A, int rank, int nullity, double field) {
Givaro::GFqDom<int> F(field);
return 1;
}


// fastcomputation.hpp

#include <vector>

int kernel(std::vector<int> A, int rank, int nullity, double field);


# matrices.pyx

# distutils: language = c++

from libcpp.vector cimport vector

cdef extern from "fastcomputation.hpp":
int kernel(vector[int] A, int rank, int nullity, double field)

cpdef pkernel(vector[int] A, int rank, int nullity, double field):
print(kernel(A, rank, nullity, field))


# setup.py


from setuptools import setup, Extension
from Cython.Build import cythonize
import os
import numpy

os.environ["CC"] = "gcc-14"
os.environ["CXX"] = "g++-14"

extensions = [
Extension(
"*",
["<path/to/cython>/*.pyx", "<path/to/cython>/fastcomputation.cpp"],
include_dirs=[
numpy.get_include(),
"<path/to/cython>",
"/opt/homebrew/Cellar/linbox/include",
"/opt/homebrew/Cellar/fflas-ffpack/2.5.0/include",
"/opt/homebrew/Cellar/givaro/4.2.0_1/include",
"/opt/homebrew/Cellar/gmp/6.3.0/include",
"/opt/homebrew/Cellar/libomp/20.1.0/include"
],
library_dirs=[
"/opt/homebrew/Cellar/linbox/lib",
"/opt/homebrew/Cellar/fflas-ffpack/2.5.0/lib",
"/opt/homebrew/Cellar/givaro/4.2.0_1/lib",
"/opt/homebrew/Cellar/gmp/6.3.0/lib",
"/opt/homebrew/Cellar/libomp/20.1.0/lib"
],
runtime_library_dirs=[
"/opt/homebrew/Cellar/linbox/lib",
"/opt/homebrew/Cellar/fflas-ffpack/2.5.0/lib",
"/opt/homebrew/Cellar/givaro/4.2.0_1/lib",
"/opt/homebrew/Cellar/gmp/6.3.0/lib",
"/opt/homebrew/Cellar/libomp/20.1.0/lib"
],
libraries=["linbox", "givaro"],
language="c++"
)
]

setup(
ext_modules=cythonize(extensions, annotate=True, language_level="3")
)


I am not an expert (or even that capable) of getting C++ to compile, so it's possible that I've misdiagnosed this and I'm leaving something out completely. The issue is that, without trying to use Givaro, everything compiles and runs, but I need to use Givaro.

Continue reading...