Hi, While testing VC 2015 with Boost, we found that Boost.Polygon contains unqualified calls to non-member size() which are incompatible with C++17's std::size(). Specifically, lines 617 and 703 of boost\polygon\polygon_traits.hpp say: points.reserve(size(polygon)); The argument appears to be "typedef std::list<CPoint> CPolygon;" which is why ADL is considering std::size(). (Note that VC's current lack of Expression SFINAE is not relevant here, as std::size() is viable for std::list.) Here's the full error output (including a new shadow warning): C:\Temp>cl /EHsc /nologo /W4 /wd4100 /MTd /I C:\Temp\boost-1.58.0\include boost_1_58_0\libs\polygon\example\gtl_custom_polygon.cpp gtl_custom_polygon.cpp Unknown compiler version - please run the configure tests and report the results c:\temp\boost-1.58.0\include\boost\polygon\detail/property_merge.hpp(286): warning C4458: declaration of 'output' hides class member c:\temp\boost-1.58.0\include\boost\polygon\detail/property_merge.hpp(223): note: see declaration of 'boost::polygon::merge_scanline::output' c:\temp\boost-1.58.0\include\boost\polygon\detail/property_merge.hpp(584): note: see reference to class template instantiation 'boost::polygon::merge_scanline' being compiled c:\temp\boost-1.58.0\include\boost\polygon\polygon_traits.hpp(617): error C2668: 'boost::polygon::size': ambiguous call to overloaded function c:\temp\boost-1.58.0\include\boost\polygon\polygon_traits.hpp(478): note: could be 'unsigned int boost::polygon::size(const T &)' with [ polygon_type=CPolygon, T=CPolygon ] \\vcfs\builds\VS\feature_WCFB01\1457423\binaries.x86ret\inc\xutility(1347): note: or 'unsigned int std::size(const _Container &)' [found using argument-dependent lookup] with [ polygon_type=CPolygon, _Container=CPolygon ] c:\temp\boost-1.58.0\include\boost\polygon\polygon_traits.hpp(617): note: while trying to match the argument list '(CPolygon)' boost_1_58_0\libs\polygon\example\gtl_custom_polygon.cpp(38): note: see reference to function template instantiation 'std::list> &boost::polygon::convolve(polygon_type &,const point_type &)' being compiled with [ _Ty=CPoint, Polygon=CPolygon, polygon_type=CPolygon, point_type=CPoint ] boost_1_58_0\libs\polygon\example\gtl_custom_polygon.cpp(144): note: see reference to function template instantiation 'void test_polygon<CPolygon>(void)' being compiled c:\temp\boost-1.58.0\include\boost\polygon\polygon_traits.hpp(703): error C2668: 'boost::polygon::size': ambiguous call to overloaded function c:\temp\boost-1.58.0\include\boost\polygon\polygon_traits.hpp(478): note: could be 'unsigned int boost::polygon::size(const T &)' with [ polygon_type=CPolygon, T=CPolygon ] \\vcfs\builds\VS\feature_WCFB01\1457423\binaries.x86ret\inc\xutility(1347): note: or 'unsigned int std::size(const _Container &)' [found using argument-dependent lookup] with [ polygon_type=CPolygon, _Container=CPolygon ] c:\temp\boost-1.58.0\include\boost\polygon\polygon_traits.hpp(703): note: while trying to match the argument list '(CPolygon)' boost_1_58_0\libs\polygon\example\gtl_custom_polygon.cpp(40): note: see reference to function template instantiation 'std::list> &boost::polygon::scale_up<Polygon>(polygon_type &,boost::polygon::coordinate_traits<int>::unsigned_area_type)' being compiled with [ _Ty=CPoint, Polygon=CPolygon, polygon_type=CPolygon ] Thanks, STL