[Boost-bugs] [Boost C++ Libraries] #12921: Linker Error with numpy in boost/python

Subject: [Boost-bugs] [Boost C++ Libraries] #12921: Linker Error with numpy in boost/python
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2017-03-22 12:49:15

#12921: Linker Error with numpy in boost/python
----------------------------+------------------------------
 Reporter:  niko.koester@…  |       Type:  Bugs
   Status:  new             |  Milestone:  To Be Determined
Component:  None            |    Version:  Boost 1.63.0
 Severity:  Problem         |   Keywords:
----------------------------+------------------------------
 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_at_numpy@python_at_boost@@YAX_N_at_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_at_numpy@python_at_boost@@YA?AVndarray_at_123@AEBVobject_at_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.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/12921>
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