How to link 3rd party dependency that you try to make a binding for?

[cyborgdennett]

Hello,

I have library A, that has it's own CMake build, and I build that with default CMake params. Than my project is project B, where I make python bindings. how can I use the A library?

Project outline:
├── dist
├── MANIFEST.in
├── primesieve (Library I try to make bindings for)
├── primesieve_bindings.cpp (bindings)
├── primesieve_py (python module dir)
. ├─ init.py
├── pyproject.toml
├── setup.py

The steps I take in my setup.py are as follows

1. Compile the primesieve library
2. using pybind11 to make bindings of this library
3. It will compile
4. installing the wheel
5. run python -c "import primesieve_py;" returns:

Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/home/<>/.local/lib/python3.10/site-packages/primesieve_py/__init__.py", line 1, in <module>
    from _primesieve import primes, primes_from  # Import from your extension module
ImportError: libprimesieve.so.12: cannot open shared object file: No such file or directory

primesieve_bindings.cpp:

#include <pybind11/pybind11.h>
#include <primesieve.hpp>

namespace py = pybind11;

PYBIND11_MODULE(_primesieve, m)
{
    m.doc() = "Python bindings for primesieve";

    m.def("primes", [](uint64_t start)
          {
        std::vector<uint64_t> primes;
        primesieve::generate_primes(start, &primes);
        return primes; });

}

primesieve_py/init.py

from _primesieve import primes, primes_from  # Import from your extension module

__all__ = ["primes"]

setup.py

from glob import glob
from setuptools import setup, find_packages
from pybind11.setup_helpers import Pybind11Extension, build_ext
import subprocess
import os
import shutil
import os
        
class build_ext(build_ext):
    def run(self):
        # Compile primesieve first
        print("Compiling primesieve...")
        if not os.path.exists('build'):
            os.makedirs('build')
        subprocess.check_call(['cmake', '../primesieve'], cwd='build')
        subprocess.check_call(['make'], cwd='build')
        # Copy the primesieve shared library to the package directory
        # the .so file is in build/libprimesieve.so
        shutil.copy2('build/libprimesieve.so', 'primesieve_py')
        
        # Now run the normal build process
        super().run()
        
ext_modules = [
    Pybind11Extension(
        "_primesieve",
        ["primesieve_bindings.cpp"],
        # Example: define_macros=[("VERSION_INFO", __version__)],
        include_dirs=["primesieve/include"],
        libraries=["primesieve"],
        library_dirs=["build"],  # Adjust if needed
        language="c++",
    ),
]


setup(
    name="primesieve-py",
    version="0.0.1",
    author="Casper Belier",
    author_email="[email protected]",
    description="Python bindings for primesieve",
    packages=["primesieve_py"],
    package_data={
        # Assuming 'primesieve_py' is the package directory where the .so file should be included
        'primesieve_py': ['libprimesieve.so'],
    },
    cmdclass={"build_ext": build_ext},
    ext_modules=ext_modules,
    zip_safe=False,
)

[cyborgdennett]

Okay, I found a solution to this problem, it consists of making the library you interface static. I don't recommend this practice for large libraries, but the one I use is only 100kb big.

Step 1.
Make sure your library is made into a static library,
In this case I made use of CMake: Also make sure to use -fPIC. Otherwise it will not compile either.
subprocess.check_call(['cmake', "-DBUILD_PRIMESIEVE=OFF", "-DBUILD_SHARED_LIBS=OFF","-DBUILD_STATIC_LIBS=ON", "-DCMAKE_CXX_FLAGS=-fPIC", '../primesieve'], cwd='build')
Step 2.
Enjoy making python bindings