Boost Python class export fails to compile with li

Question

I compiled Boost myself and used it to export the following function to a DLL :

#include <boost/python.hpp>
using namespace boost::python;

std::string greet()
{
    return "hello, dude !!";
}

BOOST_PYTHON_MODULE(hello)
{
    def("greet", greet);
}

This loaded fine in Python after I renamed the hello.dll file to hello.pyd.

Now I am trying this :

#include <boost/python.hpp>
using namespace boost::python;

struct World
{
    void set(std::string msg) { this->msg = msg; }
    std::string greet() { return msg; }
    std::string msg;
};


BOOST_PYTHON_MODULE(hello)
{
    class_<World>("World")
        .def("greet", &World::greet)
        .def("set", &World::set);
}

It errors out with :

Error   29  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@@YAPAXPAXUtype_info@23@1@Z) referenced in function "private: virtual void * __thiscall boost::python::objects::value_holder<struct World>::holds(struct boost::python::type_info,bool)" (?holds@?$value_holder@UWorld@@@objects@python@boost@@EAEPAXUtype_info@34@_N@Z) D:\Code\Python\hello\hello\hello.obj    hello

Error   30  error LNK2019: unresolved external symbol "__declspec(dllimport) public: __thiscall boost::python::converter::shared_ptr_deleter::shared_ptr_deleter(struct boost::python::converter::shared_ptr_deleter const &)" (__imp_??0shared_ptr_deleter@converter@python@boost@@QAE@ABU0123@@Z) referenced in function "public: __thiscall boost::shared_ptr<void>::shared_ptr<void><void,struct boost::python::converter::shared_ptr_deleter>(void *,struct boost::python::converter::shared_ptr_deleter)" (??$?0XUshared_ptr_deleter@converter@python@boost@@@?$shared_ptr@X@boost@@QAE@PAXUshared_ptr_deleter@converter@python@1@@Z) D:\Code\Python\hello\hello\hello.obj    hello

Error   31  error LNK2019: unresolved external symbol "__declspec(dllimport) public: __thiscall boost::python::objects::class_base::~class_base(void)" (__imp_??1class_base@objects@python@boost@@QAE@XZ) referenced in function __unwindfunclet$??0?$class_@UWorld@@Unot_specified@detail@python@boost@@U2345@U2345@@python@boost@@QAE@PBD0@Z$0    D:\Code\Python\hello\hello\hello.obj    hello

Error   32  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?$pair@PAXUtype_info@python@boost@@@std@@PAX@Z@Z) referenced in function "void __cdecl boost::python::objects::register_dynamic_id<struct World>(struct World *)" (??$register_dynamic_id@UWorld@@@objects@python@boost@@YAXPAUWorld@@@Z)  D:\Code\Python\hello\hello\hello.obj    hello

This is Visual Studio Express 2013. I compiled my own boost libraries following the exact steps as given here: http://www.boost.org/doc/libs/1_56_0/doc/html/bbv2/installation.html

I think my build/installation is fine as the global function before this was fine. But maybe there is some incompatibility with MSVC 2012 and 13 because the boost python debug library is named boost_python-vc120-mt-gd-1_56.lib.

Answer 1

I got the answer at: Using Boost::Python::Object causes linker errors

As bjam compiles boost for static linking using the steps given at : http://www.boost.org/doc/libs/1_56_0/doc/html/bbv2/installation.html

I need to define BOOST_PYTHON_STATIC_LIB or it will assume dynamic linkage for the Boost.python library.

Code that compiles:

#define BOOST_PYTHON_STATIC_LIB    
#include <boost/python.hpp>
using namespace boost::python;


struct World
{
    void set(std::string msg) { this->msg = msg; }
    std::string greet() { return msg; }
    std::string msg;
};


BOOST_PYTHON_MODULE(hello)
{
    class_<World>("World")
        .def("greet", &World::greet)
        .def("set", &World::set);
}

One way to use hello.dll, is to first rename hello.dll to hello.pyd and copy it to the directory where Python.exe starts from, then :

Python code :

import hello
obj = hello.World()
obj.set("Hello World!")
obj.greet()