id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
13062	LNK2019 Unresolved External Symbol in VS2015 when using Boost python3 and numpy3 libraries on Windows	oystein@…	Ralf W. Grosse-Kunstleve	"I am getting linker errors when trying to use the numpy3 library on Windows:

{{{
test_boost_python.obj : error LNK2019: unresolved external symbol ""class boost::python::numpy::dtype __cdecl boost::python::numpy::detail::get_float_dtype<32>(void)"" (??$get_float_dtype@$0CA@@detail@numpy@python@boost@@YA?AVdtype@123@XZ) referenced in function ""public: static class boost::python::numpy::dtype __cdecl boost::python::numpy::detail::builtin_dtype<float,0>::get(void)"" (?get@?$builtin_dtype@M$0A@@detail@numpy@python@boost@@SA?AVdtype@345@XZ)
}}}

Small test program to reproduce:

{{{#!c++
#include <boost/python.hpp>
#include <boost/python/numpy.hpp>

namespace bp = boost::python;
namespace np = boost::python::numpy;

np::ndarray test_make_zeros(int rows, int cols)
{
    return np::zeros(bp::make_tuple(rows, cols), np::dtype::get_builtin<float>());  
}

BOOST_PYTHON_MODULE(test_boost_numpy)
{
    np::initialize();

    bp::def(""test_make_zeros"", test_make_zeros);
}
}}}

I have downloaded and built Boost 1.64 on Windows by using the following command:

{{{
b2 --build-type=complete address-model=64 toolset=msvc stage
}}}

I added a user-config.jam file in my home directory to tell Boost where to find Python 3:

{{{
using python : 3.6 : c:\\anaconda3\\python ;
}}}

I am using the following CMakeLists.txt file:

{{{
cmake_minimum_required(VERSION 3.8)
project(test_boost_python)

set(BOOST_ROOT ""C:/Boost-1.64"")
SET(Boost_ADDITIONAL_VERSIONS 1.64)

find_package(PythonLibs 3.6 REQUIRED)
include_directories(${PYTHON_INCLUDE_DIRS})

find_package(Boost REQUIRED COMPONENTS python3 numpy3)
include_directories(${Boost_INCLUDE_DIRS})
link_directories(${Boost_LIBRARY_DIRS})

add_library(test_boost_python SHARED test_boost_python.cpp)
set_target_properties(test_boost_python PROPERTIES PREFIX """" SUFFIX "".pyd"")
set_target_properties(test_boost_python PROPERTIES DEFINE_SYMBOL ""BOOST_ALL_NO_LIB"")
target_link_libraries(test_boost_python ${PYTHON_LIBRARIES} ${Boost_LIBRARIES})
}}}

My boost::python library is given the name boost_python3-vc140-mt-1_64.lib and boost::numpy ends up as boost_numpy3-vc140-mt-1_64.lib when linking against Python 3.6.

I had to turn on BOOST_ALL_NO_LIB. If not, the compiler looks for boost_python-vc140-mt-1_64.lib boost_numpy-vc140-mt-1_64.lib (which is under the wrong name, with a missing number 3 after the library names; possibly also a bug on Windows?)

See also https://stackoverflow.com/questions/44072440/lnk2019-unresolved-external-symbol-in-vs2015-when-using-boost-python3-and-numpy3 for more information"	Bugs	new	To Be Determined	python USE GITHUB	Boost 1.64.0	Showstopper		python3 numpy3