sibl

Lesson a00: Bind C++ for use with Python

Goals

With the SIBL Mesh Engine C++ source code, compile C++ binding code on macOS, Linux, and Windows to the xybind library for use with Python.

Steps

macOS

• Create the xybind library. Also, assure any old versions of the xybind packages are deleted prior to creating the new xybind.

> conda activate siblenv
> cd ~/sibl/geo/src/bind
> rm xybind.cypthon-39-darwin.so  # delete the old binary if it exists
> rm -rf xybind.egg-info/  # delete the old binary folder if it exists
> pip install -e .
Obtaining file:///Users/chovey/sibl/geo/src/bind
  Preparing metadata (setup.py) ... done
Installing collected packages: xybind
  Attempting uninstall: xybind
    Found existing installation: xybind 0.0.7
    Uninstalling xybind-0.0.7:
      Successfully uninstalled xybind-0.0.7
  Running setup.py develop for xybind
Successfully installed xybind-0.0.7

• Test the xybind library:

> cd ~/sibl/geo/tests
> pytest test_xybind.py -v                                                     (siblenv)
===================================================== test session starts ======================================================
platform darwin -- Python 3.9.7, pytest-6.2.5, py-1.9.0, pluggy-0.12.0 -- /Users/chovey/opt/miniconda3/envs/siblenv/bin/python
cachedir: .pytest_cache
rootdir: /Users/chovey/sibl/geo
plugins: cov-2.10.1
collected 10 items

test_xybind.py::test_version PASSED                                               [ 10%]
test_xybind.py::test_add PASSED                                                   [ 20%]
test_xybind.py::test_subtract PASSED                                              [ 30%]
test_xybind.py::test_attributes PASSED                                            [ 40%]
test_xybind.py::test_power PASSED                                                 [ 50%]
test_xybind.py::test_pet PASSED                                                   [ 60%]
test_xybind.py::test_unit_square_contains PASSED                                  [ 70%]
test_xybind.py::test_unit_squares_inType PASSED                                   [ 80%]
test_xybind.py::test_qt_node_counts PASSED                                        [ 90%]
test_xybind.py::test_unit_circle_quad_mesh PASSED                                 [100%]

============================= 10 passed in 0.63s =======================================

• Run two methods from xybind interactively with Python:

> python
Python 3.9.7 (default, Sep 16 2021, 08:50:36)
[Clang 10.0.0 ] :: Anaconda, Inc. on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import xybind as xyb
>>> xyb.add(3, 4)
7
>>> xyb.subtract(3, 4)
-1

Linux

Same as macOS.

Windows

• Replace the acsokol user name in the example with the user name and path as appropriate for your local environment.

> cd ~/sibl/geo/src/dual
> g++ -O3 -Wall -shared -std=c++11 -fPIC -fvisibility=hidden -IC:/Users/acsokol/Miniconda3/Include -IC:/Users/acsokol/Miniconda3/lib/site-packages/pybind11/include  main.cpp -o xybind.pyd -LC:/Users/acsokol/Miniconda3 -lpython39

Details

Split it up into a few different parts:

• First set of compiler flags are pretty standard, the two items that have required messing with were as follows:
  • The visibility flag which seems to be a newer pybind11 thing.
  • The other is Werror, which I had to remove. It says to treat warnings as errors which we do not want.

> g++ -O3 -Wall -Werror -shared -std=c++11 -fPIC -fvisibility=hidden

Include Locations

These were the locations returned by the python include line, $(python -m pybind11 --includes), that just runs nicely in Linux/macOS. I loaded python and typed in the command to get the correct responses.

• -IC:/Users/acsokol/Miniconda3/Include
• -IC:/Users/acsokol/Miniconda3/lib/site-packages/pybind11/include

The list of cpp files to compile (later will include other cpp files) main.cpp.

This line gets filled in by python-config which didn’t work either on windows, xybind$(python3-config --extension-suffix). The pyd seems to be a windows dll equivalent?? xybind name has to also appear in the PYBIND11_MODULE(xybind, m) line in the cpp file.

• -o xybind.pyd

This was the hangup for a long time, telling it where the python39.dll file was located and getting the correct syntax to link it. The capital L tells the compiler what folder to look in and the lower case l tells it the file with some assumed platform dependent extension.

• -LC:/Users/acsokol/Miniconda3 -lpython39

Index

This site is open source. Improve this page.