05-inheritance linking error in VS2015

[simbaforrest]

Thanks for the project first.

I can compile and run all other example except for 05-inheritance on VS 2015 with Boost.Python 2.7 x64, which gave me the following linking error:

1>inheritance.obj : error LNK2019: unresolved external symbol "class Base const volatile * __cdecl boost::get_pointer<class Base const volatile >(class Base const volatile *)" (??$get_pointer@$$CDVBase@@@boost@@YAPEDVBase@@PEDV1@@Z) referenced in function "public: static struct _object * __cdecl boost::python::objects::make_instance_impl<class Base,struct boost::python::objects::pointer_holder<class std::auto_ptr<class Base>,class Base>,struct boost::python::objects::make_ptr_instance<class Base,struct boost::python::objects::pointer_holder<class std::auto_ptr<class Base>,class Base> > >::execute<class std::auto_ptr<class Base> >(class std::auto_ptr<class Base> &)" (??$execute@V?$auto_ptr@VBase@@@std@@@?$make_instance_impl@VBase@@U?$pointer_holder@V?$auto_ptr@VBase@@@std@@VBase@@@objects@python@boost@@U?$make_ptr_instance@VBase@@U?$pointer_holder@V?$auto_ptr@VBase@@@std@@VBase@@@objects@python@boost@@@345@@objects@python@boost@@SAPEAU_object@@AEAV?$auto_ptr@VBase@@@std@@@Z)

Based on this discussion, I was able to fix the problem by adding the following code to inheritance.cpp. Not sure whether this should be counted as a bug of this project, but I guess it might help others if they also found this issue.

namespace boost
{
	template <>
	Base const volatile * get_pointer<class Base const volatile >(
		class Base const volatile *c)
	{
		return c;
	}
}

[Achimh3011]

Do you want to open a PR? I never tried to compile the code on Windows, but it'd be nice to have that platform supported as well.

[mkulagowski]

I know it's been a couple of months now, but I need to use Boost::python and tried to crack it with a help of Your code. After few days and boost-headaches I can say, that I successfully ran Your code on:
-Win 10 x64
-Python 3.6 x64
-Boost 1.65
-VS Enterprise 2017 v.15.2 (compiler msvc-14.1)
-CMake 3.9.1

I built all of them, but checked only 1,2,3 & 5.

[Achimh3011]

Hi, was the aforementioned patch included or did it work without?

[mkulagowski]

It worked without but I had to:

• build Boost myself, to make it work with my python version (not sure how it works with boost::python for python 2.7).
• make change in CMakeLists to look for python (not python3).
• make changes in CMake (FindBoost.cmake) to actually recognize Boost 1.65
• change linker settings in VS to look for boost_python3*.dll instead of boost_python*.dll one.
• move created *.pyd file next to the *.py file for it to work, but that is normal as far as I recall.

Yet all of these problems are related to Boost and CMake, not Your code ;)

[Achimh3011]

I close the issue now. I'd still accept an PR if anyone had one...

[ruoxu233]

It worked without but I had to:

• build Boost myself, to make it work with my python version (not sure how it works with boost::python for python 2.7).
• make change in CMakeLists to look for python (not python3).
• make changes in CMake (FindBoost.cmake) to actually recognize Boost 1.65
• change linker settings in VS to look for boost_python3*.dll instead of boost_python*.dll one.
• move created *.pyd file next to the *.py file for it to work, but that is normal as far as I recall.

Yet all of these problems are related to Boost and CMake, not Your code ;)

build Boost _python need careful, othervise will happen Link error like this:
1>boost_python39-vc142-mt-gd-x64-1_75.lib(pickle_support.obj): error LNK2001: unresolved external symbol __imp__Py_Dealloc
1>boost_python39-vc142-mt-gd-x64-1_75.lib(function.obj) : error LNK2019: unresolved external symbol __imp__Py_NewReference referenced in function _PyObject_INIT