id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
12921	Linker Error with numpy in boost/python	niko.koester@…	Ralf W. Grosse-Kunstleve	"I am the author of the attached (and solved) stackoverflow question:
http://stackoverflow.com/questions/42899376/lnk2001-error-when-using-boostnumpy/42936160#42936160

My question is, is the described behavior a bug?

Let me start with the answer:

Import the Boost\python numpy package like:

#define BOOST_LIB_NAME ""boost_numpy""

#include <boost/python.hpp>


The Problem description (copy from Stackoverflow):

I am trying to call a C++ .dll from Python and return a numpy array. I am using

Anaconda 2.7 x64
Visual Studio 2013 update 5
boost 1.63.0 prebuileded for lib64-msvc-12.0
I managed to compile this simple example frome here and run it in Python:

#include ""stdafx.h""
#define BOOST_PYTHON_STATIC_LIB
#include <boost/python.hpp>

char const* greet()
{
    return ""hello, world"";
}

BOOST_PYTHON_MODULE(test)
{
    using namespace boost::python;
    def(""greet"", greet);
}
I am unsure about the #define BOOST_PYTHON_STATIC_LIB but without it python could not open the pyd file. I suspected that python could not resolve the references to MSVCR120.dll in the dynamic build, but I am just guessing.

Next step was to include <boost/python/numpy.hpp> and follow this instuctions and start with just creating a numpy::ndarray. Yes, I am aware that void is in contradiction to the intention of getting values, I just wanted to keep things as simple as possible.

#include <boost/python/numpy.hpp>
namespace p = boost::python;
namespace np = boost::python::numpy;

void getNPArray()
{
    Py_Initialize();
    np::initialize();
    p::object tu = p::make_tuple('a', 'b', 'c');
    np::ndarray const example_tuple = np::array(tu);
    return;
}
The import and namespace declarations compile without error. At next step I encountered the linker error. While Py_Initialize() worked fine, the np::initialize() causes the linker to throw

error LNK2001: unresolved external symbol ""void __cdecl boost::python::numpy::initialize(bool)"" (?initialize@numpy@python@boost@@YAX_N@Z)
And np::ndarray const example_tuple = np::array(tu) causes a

error LNK2001: unresolved external symbol ""class boost::python::numpy::ndarray __cdecl boost::python::numpy::array(class boost::python::api::object const &)"" (?array@numpy@python@boost@@YA?AVndarray@123@AEBVobject@api@23@@Z)
As the linker is perfectly happy with the first example I am toally confused about what is going on here. I also tried to comment out all parts from the first example and just compile the second part witout any change in behaviour.

"	Bugs	new	To Be Determined	python USE GITHUB	Boost 1.63.0	Problem