From oystein.skotheim at zividlabs.com  Mon May 22 15:05:41 2017
From: oystein.skotheim at zividlabs.com (=?iso-8859-1?Q?=D8ystein_Skotheim?=)
Date: Mon, 22 May 2017 19:05:41 +0000
Subject: [C++-sig] LNK2019 Unresolved External Symbol in VS2015 when using
 Boost python3 and numpy3 libraries on Windows
Message-ID: <HE1PR0701MB2298377247FF9C513B630D1D96F80@HE1PR0701MB2298.eurprd07.prod.outlook.com>

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 then trying to compile a small test project using boost::python and boost::numpy:

	#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_python)
	{
		np::initialize();
		bp::def("test_make_zeros", test_make_zeros);
	}

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 - Is this a bug on Windows?)

For my test project, I now get the following linking error:

	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@$0CA@@detail at numpy@python at boost@@YA?AVdtype at 123@XZ) referenced in function "public: static class boost::python::numpy::dtype __cdecl boost::python::numpy::detail::builtin_dtype<float,0>::get(void)" (?get@?$builtin_dtype at M$0A@@detail at numpy@python at boost@@SA?AVdtype at 345@XZ)

What may be the reason for this missing symbol and how should I go about to fix it?

-?ystein

From hzhou3 at clemson.edu  Thu May 25 00:54:16 2017
From: hzhou3 at clemson.edu (Heng Zhou)
Date: Thu, 25 May 2017 00:54:16 -0400
Subject: [C++-sig] Cannot import the Hello World module of Boost.Python's
 QuickStart in python
Message-ID: <CADu3_9_yd-Fv=JWKw+Bb0emdyHoXJZ0cpsRSU7cwFJf4W25BBg@mail.gmail.com>

I followed the steps in the QuickStart of Boost.Python here:
https://urldefense.proofpoint.com/v2/url?u=http-3A__www.boost.org_doc_libs_1-5F49-5F0_libs_python_doc_tutorial_doc_html_index.html&d=DwIBaQ&c=Ngd-ta5yRYsqeUsEDgxhcqsYYY1Xs5ogLxWPA_2Wlc4&r=jSyKml46sQcyHEvdXhVDNwoCqN0MBfWgTmJFqTljZKM&m=6Z-RP-Mjs781YKE08gvO6owK6zMqGXD7ZRueaJHfUNo&s=2-beQ7RazSZIfAiaWI9QGvRv_EumlzP0E6iD2Qfmntg&e= .
I can successfully compile, link and get the output dll file, but I always
got and error:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: No module named hello_ext

when trying to import it in python. This is my environment:

- Windows 7 Enterprise SP1 64 bit, I am the Administrator and run cmd as
Administrator.
- Python 2.7.13 64 bit
- Visual Studio 2015 (v14.0) Update 3
- In VS2015, the project name is ConsoleApplication1, so the output is
ConsoleApplication1.dll.
- I built the simple sample code under x64 configuration in VS2015 and I
verified with dumpbin that the output ConsoleApplication1.dll is really 64
bit.

I tried the following but got the same error:
- I added the search path to the ConsoleApplication1.dll into sys.path
- I changed the name of ConsoleApplication1.dll to hello_ext.dll

The QuickStart says "The resulting DLL is now visible to Python." but that
magic does not take place on my machine. Could you please tell me what I
had missed or, if I built the DLL properly, how to import it in python
command line? Thanks a lot.
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From hzhou3 at clemson.edu  Fri May 26 01:32:46 2017
From: hzhou3 at clemson.edu (Heng Zhou)
Date: Fri, 26 May 2017 01:32:46 -0400
Subject: [C++-sig] Cannot import the Hello World module of
 Boost.Python's QuickStart in python
In-Reply-To: <CADu3_9_yd-Fv=JWKw+Bb0emdyHoXJZ0cpsRSU7cwFJf4W25BBg@mail.gmail.com>
References: <CADu3_9_yd-Fv=JWKw+Bb0emdyHoXJZ0cpsRSU7cwFJf4W25BBg@mail.gmail.com>
Message-ID: <CADu3_98QH=j1wKYWUc7bn8CXDZgZb7Qh57232z8oOdqq47YRjQ@mail.gmail.com>

I solved the problem myself. This is a link to my answer:
https://urldefense.proofpoint.com/v2/url?u=https-3A__stackoverflow.com_questions_44161857_the-2Ddll-2Dcreated-2Dby-2Dboost-2Dpython-2Dcannot-2Dbe-2Dimported-2Dfollowing-2Dboost-2Dpythons-2Dqui_44194094-2344194094&d=DwIBaQ&c=Ngd-ta5yRYsqeUsEDgxhcqsYYY1Xs5ogLxWPA_2Wlc4&r=jSyKml46sQcyHEvdXhVDNwoCqN0MBfWgTmJFqTljZKM&m=Z6BHCcdSSCk4Tyk1aODuxJJLvF5j7M6QqGMajnzntSs&s=1iKwggA27bECIO0iVuLFA4Zz40g5EQ38MrwLBqKfBjY&e= 

On Thu, May 25, 2017 at 12:54 AM, Heng Zhou <hzhou3 at clemson.edu> wrote:

> I followed the steps in the QuickStart of Boost.Python here:
> https://urldefense.proofpoint.com/v2/url?u=http-3A__www.boost.org_doc_libs_1-5F49-5F0_libs_python_doc_&d=DwIBaQ&c=Ngd-ta5yRYsqeUsEDgxhcqsYYY1Xs5ogLxWPA_2Wlc4&r=jSyKml46sQcyHEvdXhVDNwoCqN0MBfWgTmJFqTljZKM&m=Z6BHCcdSSCk4Tyk1aODuxJJLvF5j7M6QqGMajnzntSs&s=B7c9mrc4EPId10XO2UsWu_OZHNf3tA6rtPRvqJ2f_dE&e= 
> tutorial/doc/html/index.html. I can successfully compile, link and get
> the output dll file, but I always got and error:
>
> Traceback (most recent call last):
>   File "<stdin>", line 1, in <module>
> ImportError: No module named hello_ext
>
> when trying to import it in python. This is my environment:
>
> - Windows 7 Enterprise SP1 64 bit, I am the Administrator and run cmd as
> Administrator.
> - Python 2.7.13 64 bit
> - Visual Studio 2015 (v14.0) Update 3
> - In VS2015, the project name is ConsoleApplication1, so the output is
> ConsoleApplication1.dll.
> - I built the simple sample code under x64 configuration in VS2015 and I
> verified with dumpbin that the output ConsoleApplication1.dll is really 64
> bit.
>
> I tried the following but got the same error:
> - I added the search path to the ConsoleApplication1.dll into sys.path
> - I changed the name of ConsoleApplication1.dll to hello_ext.dll
>
> The QuickStart says "The resulting DLL is now visible to Python." but that
> magic does not take place on my machine. Could you please tell me what I
> had missed or, if I built the DLL properly, how to import it in python
> command line? Thanks a lot.
>
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