Cython: zmq_compat.h Cannot open include file: 'zmq.h': No such file or directory

[mattia-donato]

pyzmq version: 25.0.0
libzmq version: 4.3.4
Python version: 3.10 (venv) on Windows 10

In my project due to performance issues I need to use the low-level C calls.
In the pyzmq be possible to use as in the cimport zmq.backend.cython.libzmq as shown in the example "pyzmq/examples/cython/".

The setup.py:

from setuptools import find_packages, setup
from distutils.extension import Extension
from distutils.core import setup
from Cython.Build import cythonize
from Cython.Distutils import build_ext
import numpy as np
import zmq

# COMMAND TO COMPILE: python setup.py build_ext --inplace

include_dirs = [np.get_include()]+zmq.get_includes()+zmq.get_library_dirs()]

print(include_dirs)

print()
setup(
    ext_modules = cythonize([Extension("myproject.libs.cython.fastconverter",
                                       ["myproject/libs/cython/fastconverter.pyx"]),
                             Extension("myproject.libs.cython.ni_fpga_fi.ni_fpga_fi",
                                       ["myproject/libs/cython/ni_fpga_fi/ni_fpga_fi.pyx"]),
                             ],
                             language_level = 3, annotate=True),
    include_dirs=include_dirs,
    packages=find_packages()
)

After the compilation done with the command

python .\setup.py build_ext --inplace

I get the error:

C:\myproject\venv\lib\site-packages\zmq\utils\zmq_compat.h(20): fatal error C1083: Cannot open include file: 'zmq.h': No such file or directory

I thought to change the include_dirs in the setup.py but actually "zmq.h" do not exist in anywhere in the python site-packages.

I installed pyzmq by using simply:

pip install pyzmq

Is there some options that I can use to install PyZmq keeping the file zmq.h somewhere?

Thanks and
Ciao

[minrk]

pyzmq installs don't redistribute zmq.h (maybe they should!), so you'll need to get it from libzmq itself during your build process.

This is related to #1412 and #986 where a pyzmq install on its own really does not provide enough information to compile against libzmq. In particular: the libzmq name, which may be mangled by auditwheel, and zmq.h. Not sure if there's anything else needed.

[mattia-donato]

Thank you minrk for your quick answer!
I tried to copy the zmq.h but of course it is not enough because the linker is complaining: I do not have the static libraries (.lib) neither the definition (.def) but I have only the dynamic libraries (.dll).

BTW The reason why I am trying to cimport libzmq in my cython code is due to performance. Unfortunately the cython methods, of the backend of pyzmq, are not always "nogil".

[minrk]

Ah, if you're on Windows that's a lot more complicated and I've no idea how to do it.

And yes, the Cython classes mostly have gil-holding methods, since they deal with Python objects. You'll want to use the libzmq C API (exposed in pyzmq's libzmq.pxd) to actually do gil-free send/recv.

[NazimHAli]

+1 running into the same error now.