Including <arrayobject.h> path for C extension compilation

[jmorgadov]

Hi, I'm developing a package that contains a C extension which use arrayobject.h header (from numpy). In order to use this header locally I set the enviroment variable C_INCLUDE_PATH and I'm trying to do that in the builder action.

As I don't know "where" is that header in the cloud I find it using this command:

$(python -c 'import numpy, os; print(os.path.dirname(numpy.__file__))')/core/include/numpy

I've tried to set that enviroment variable using:

[tool.cibuildwheel]
environment = { C_INCLUDE_PATH="$(python -c 'import numpy, os; print(os.path.dirname(numpy.__file__))')/core/include/numpy" }

But it sais numpy is not installed, even when I've tried:

[tool.cibuildwheel]
before-build = [ "pip install numpy" ]

I'm aware that I should use the build-system.requires but that didn't work either.

It seems that enviroment variables are setted before all.

I know i can use the -I flag and set the CFLAG variable but I'm afraid this will end up in the same mistake (evaluating the variable before instaling numpy).

So, how can I include this path? Is a better way to do this that I'm missing?

Thanks.

[mayeut]

Without seeing the actual config (do you have a link?) it's hard to answer.
Usually, as you noted, numpy shall be specified in build-system.requires and in fact, you probably want oldest-supported-numpy in there rather than numpy.
The rest will depend on your actual build system.
With setuptools, you'd use np.get_include() something like Extension('foo', ['foo.c'], include_dirs=[np.get_include()])

EDIT:
I'm guessing it's for https://github.com/jmorgadov/fdce
If I'm guessing right, I think that adding oldest-supported-numpy to build-system.requires and changing setup.py as follow will do (you don't need environment or before-build settings here):

 from setuptools import Extension, setup, find_packages

+ import numpy as np
+
 setup(
     name="fdce",
     version="0.1.1a3",
     description="Finite difference coefficient estimator",
     author="Jorge Morgado Vega",
     author_email="[email protected]",
     requires=["numpy"],
     packages=find_packages(),
     python_requires=">=3.8",
     ext_modules=[
-         Extension("fdce._extension._fdce", ["fdce/_extension/_fdce.c"]),
+         Extension("fdce._extension._fdce", ["fdce/_extension/_fdce.c"], include_dirs=[np.get_include()]), 
     ]
 )

[jmorgadov]

You are totally right, I'm really new to C extensions and I didn't knew about np.get_include(). I applyed all the suggestions and it is compiling perfectly. Thanks a lot! :)