Python Boost Library

[jonassorgenfrei]

Hey i'm trying to use your action to build a test project against boost.
Unfortunatly it looks like the boost python library is not build with it (?).

Using:
find_package(Boost REQUIRED COMPONENTS python REQUIRED)
the return is:
`
Found package configuration file:

D:/a/PythonCLib/PythonCLib/boost/boost/lib/cmake/boost_python-1.78.0/boost_python-config.cmake

but it set boost_python_FOUND to FALSE so package "boost_python" is
considered to be NOT FOUND
`
The action I'm using is:
https://github.com/jonassorgenfrei/PythonCLib/blob/main/.github/workflows/build-test-windows.yml

Is there a flag to configure the boost build to build the python lib too?

[MarkusJx]

All libraries except msvc (shared) and the arm libraries should support python. Try setting the LINK parameter to static.

If that doesn't work, I don't have any experience with the boost python libraries, maybe I'll need to configure the binaries differently?
But if that is the case, I can't promise anything as I'm building the binaries using github actions and the runners are already running low on memory, so adding more libraries to those binaries may not work at all (I had to disable python on arm due to memory issues already).

[jonassorgenfrei]

Hey @MarkusJx thanks for your fast answer.

After adjusting my settings cmake now finds the libraries:

    - name: Install boost
      uses: MarkusJx/install-boost@v2.3.1
      id: install-boost
      with:
          boost_version: 1.78.0
          link: static
          platform_version: 2022
          toolset: msvc
    #- name: Build Boost
    #  id: boost
    #  uses: egor-tensin/build-boost@v1
    #  with:
    #    version: 1.78.0
    #    libraries: system python
    #    platform: x64
    #    configuration: Release
    #    toolset: vs2022
    #    static: 1
    #- name: Show paths
    #  run: |
    #    echo 'Boost has been unpacked to: %s\n' '${{ steps.boost.outputs.root }}'
    #    echo 'Libraries can be found here: %s\n' '${{ steps.boost.outputs.librarydir }}'
    #  shell: bash
    - name: Configure
      run: |
        mkdir build
        cd build
        cmake .. -DBoost_USE_STATIC_LIBS=ON 
        # -D "BOOST_ROOT=${{ steps.boost.outputs.root }}"  -D "BOOST_LIBRARYDIR=${{ steps.boost.outputs.librarydir }}"
      env:
        BOOST_ROOT: ${{ steps.install-boost.outputs.BOOST_ROOT }}
    - name: Build
      run: cmake --build build --parallel --config Release

Unfortunatly when building my project i do get now a lot of linking issues.

myClass.obj : error LNK2019: unresolved external symbol "__declspec(dllimport) void * __cdecl boost::python::objects::find_static_type(void *,struct boost::python::type_info,struct boost::python::type_info)" (__imp_?find_static_type@objects@python@boost@@YAPEAXPEAXUtype_info@23@1@Z) referenced in function "private: virtual void * __cdecl boost::python::objects::value_holder<class MyClass>::holds(struct boost::python::type_info,bool)" (?holds@?$value_holder@VMyClass@@@objects@python@boost@@EEAAPEAXUtype_info@34@_N@Z) [D:\a\PythonCLib\PythonCLib\build\pyClass.vcxproj]
myClass.obj : error LNK2019: unresolved external symbol "__declspec(dllimport) public: __cdecl boost::python::converter::shared_ptr_deleter::shared_ptr_deleter(struct boost::python::converter::shared_ptr_deleter const &)" (__imp_??0shared_ptr_deleter@converter@python@boost@@QEAA@AEBU0123@@Z) referenced in function "public: __cdecl boost::detail::shared_count::shared_count<void *,struct boost::python::converter::shared_ptr_deleter>(void *,struct boost::python::converter::shared_ptr_deleter)" (??$?0PEAXUshared_ptr_deleter@converter@python@boost@@@shared_count@detail@boost@@QEAA@PEAXUshared_ptr_deleter@converter@python@2@@Z) [D:\a\PythonCLib\PythonCLib\build\pyClass.vcxproj]
    Hint on symbols that are defined and could potentially match:
      "__declspec(dllimport) public: __cdecl boost::python::converter::shared_ptr_deleter::shared_ptr_deleter(class boost::python::handle<struct _object>)" (__imp_??0shared_ptr_deleter@converter@python@boost@@QEAA@V?$handle@U_object@@@23@@Z)
myClass.obj : error LNK2019: unresolved external symbol "__declspec(dllimport) public: __cdecl boost::python::objects::py_function_impl_base::py_function_impl_base(void)" (__imp_??0py_function_impl_base@objects@python@boost@@QEAA@XZ) referenced in function "private: void __cdecl boost::python::class_<class MyClass,struct boost::python::detail::not_specified,struct boost::python::detail::not_specified,struct boost::python::detail::not_specified>::def_impl<class MyClass,class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > (__cdecl*)(class MyClass const &),struct boost::python::detail::def_helper<char const *,struct boost::python::detail::not_specified,struct boost::python::detail::not_specified,struct boost::python::detail::not_specified> >(class MyClass *,char const *,class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > (__cdecl*)(class MyClass const &),struct boost::python::detail::def_helper<char const *,struct boost::python::detail::not_specified,struct boost::python::detail::not_specified,struct boost::python::detail::not_specified> const &,...)" (??$def_impl@VMyClass@@P6A?AV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@AEBV1@@ZU?$def_helper@PEBDUnot_specified@detail@python@boost@@U1234@U1234@@detail@python@boost@@@?$class_@VMyClass@@Unot_specified@detail@python@boost@@U2345@U2345@@python@boost@@AEAAXPEAVMyClass@@PEBDP6A?AV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@AEBV3@@ZAEBU?$def_helper@PEBDUnot_specified@detail@python@boost@@U1234@U1234@@detail@12@ZZ) [D:\a\PythonCLib\PythonCLib\build\pyClass.vcxproj]
myClass.obj : error LNK2019: unresolved external symbol "__declspec(dllimport) public: __cdecl boost::python::objects::class_base::~class_base(void)" (__imp_??1class_base@objects@python@boost@@QEAA@XZ) referenced in function "public: __cdecl boost::python::class_<class MyClass,struct boost::python::detail::not_specified,struct boost::python::detail::not_specified,struct boost::python::detail::not_specified>::~class_<class MyClass,struct boost::python::detail::not_specified,struct boost::python::detail::not_specified,struct boost::python::detail::not_specified>(void)" (??1?$class_@VMyClass@@Unot_specified@detail@python@boost@@U2345@U2345@@python@boost@@QEAA@XZ) [D:\a\PythonCLib\PythonCLib\build\pyClass.vcxproj]
myClass.obj : error LNK2019: unresolved external symbol "__declspec(dllimport) void __cdecl boost::python::objects::register_dynamic_id_aux(struct boost::python::type_info,struct std::pair<void *,struct boost::python::type_info> (__cdecl*)(void *))" (__imp_?register_dynamic_id_aux@objects@python@boost@@YAXUtype_info@23@P6A?AU?$pair@PEAXUtype_info@python@boost@@@std@@PEAX@Z@Z) referenced in function "void __cdecl boost::python::objects::register_dynamic_id<class MyClass>(class MyClass *)" (??$register_dynamic_id@VMyClass@@@objects@python@boost@@YAXPEAVMyClass@@@Z) [D:\a\PythonCLib\PythonCLib\build\pyClass.vcxproj]
myClass.obj : error LNK2001: unresolved external symbol "public: __cdecl boost::python::objects::class_base::~class_base(void)" (??1class_base@objects@python@boost@@QEAA@XZ) [D:\a\PythonCLib\PythonCLib\build\pyClass.vcxproj]
D:\a\PythonCLib\PythonCLib\build\Release\pyClass.pyd : fatal error LNK1120: 6 unresolved externals [D:\a\PythonCLib\PythonCLib\build\pyClass.vcxproj]

Locally i only tested with shared libraries not with static libraries

This is the Action I'm using which unfortunatly failed:
https://github.com/jonassorgenfrei/PythonCLib/actions/runs/3357491244/jobs/5563332782

[MarkusJx]

Apparently, the boost python libraries work in a weird way, so that's good to know.

I've tried compiling your project locally and found this stackoverflow answer. So for some reason, when using boost static libraries, you have to define BOOST_PYTHON_STATIC_LIB before including boost/python.hpp. So I've added this to your project and it compiles.

Thus, I present you two options solving your issue:

1. Define BOOST_PYTHON_STATIC_LIB in your myClass.cpp before including boost/python.hpp:

#define BOOST_PYTHON_STATIC_LIB
#include <boost/python.hpp>

2. (Probably more elegant) If you don't want to change your local setup, which you probably don't want to do, just add this to your CMakeLists.txt:

# Use static python libs in CI runs
if(DEFINED ENV{CI})
    add_definitions(-DBOOST_PYTHON_STATIC_LIB)
endif()

Again, I can't provide shared boost libraries with python due to memory limitations, so these may be the only possible options.

Just let me know if this helped and have a nice day :)

[MarkusJx]

So I've looked into building boost for multiple python versions and although it is possible, it's a huge pain to set up on github actions as actions/setup-python doesn't provide a wide range of python versions (e.g. for ubuntu 22.04, only python 3.10 is supported, python 2.7 is only available for macOs).

Basically, you'll have to handle this on your own, I'm sorry

[jonassorgenfrei]

Oh i see okay yeah will try to find the default python and always force it to be used.
But thanks for taking a look. :)

[MarkusJx]

Ok, so I've changed my mind.

Starting from boost version 1.80.0, boost.python is built with support for various python versions on selected binaries.

[jonassorgenfrei]

Awesome that's great!!!

Thanks for implementing it and letting me know.

I will give it a try the next days ☺️!

[jonassorgenfrei]

FYI works like a charm, just needed to add the Boost_PYTHON_VERSION="" flag to my cmake command and it's working and running perfectly!
e.g. -DBoost_PYTHON_VERSION="${{ matrix.python-version }}"

Thanks so much for adding this!