Symbol Undefined...

I have read multiple examples for generating an so library using cython’s pure python interface, and then later calling a function in it. THE FUNCTION IS NOT GETTING DEFINED IN THE SO!

• The pure python code:

#cython: language_level=3

import cython

@cython.cfunc
@cython.returns(cython.int)
@cython.locals(a=cython.int)
def blah(a):
    return 42

• The cython command: cython3 test.py
• The gcc step: gcc -fpic `python3-config --cflags` -o test.o -c test.c
• generate an so from the compilation output: gcc -shared -o test.so test.o `python3-config --libs`
• List the entrypoints in the so:

nm -D test.so|less
# (I'm not seeing the function "blah" there!)

• Try accessing the so:

python3
from ctypes import CDLL
so=CDLL('./test.so')
dir(so)
['_FuncPtr', '__class__', '__delattr__', '__dict__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattr__', '__getattribute__', '__getitem__', '__gt__', '__hash__', '__init__', '__init_subclass__', '__le__', '__lt__', '__module__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__', '_func_flags_', '_func_restype_', '_handle', '_name'] 
# NO "blah" function!

All the pure python examples take it as a given that it will show up.

cython version: 0.29.30 python version: 3.9.2 gcc version: 10.2.1 ctypes version: 1.1.0 OS: Debian 11

[bitmodeler]

So to generate an so, I guess I want to do the setup.py with the cythonize call.

They are doing it with a pyx for input; can I pass a pure-python py file?

[I found 2 online examples doing it the gcc way I listed above; I figured once you have the c file generated by cython, the function call representing the call to the python function should be exposed thanks to those decorators I used above and found online…]

• setup.py:

from setuptools import setup
from Cython.Build import cythonize
import sys

setup(ext_modules=cythonize(sys.argv[-1]))

• invocation: python setup.py build_ext --inplace test.py

And: thanks so far…

[scoder]

There’s a “public” modifier to expose symbols. Not sure if that’s available in Python code or limited to Cython syntax, though.