Hi, I am trying to compile a package that utilizes boost libraries, and the compilation fails. This is on OS X El Capitan, with clang version: 7.3.0.7030029. Is this a known issue, and is there a work around? In file included from /opt/local/include/boost/signals2/slot_base.hpp:18: /opt/local/include/boost/signals2/detail/foreign_ptr.hpp:42:54: error: reference to 'weak_ptr' is ambiguous template<typename T> struct weak_ptr_traits<std::weak_ptr<T> > ~~~~~^ /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/memory:5035:29: note: candidate found by name lookup is 'std::__1::weak_ptr' class _LIBCPP_TYPE_VIS_ONLY weak_ptr ^ /opt/local/include/boost/signals2/detail/foreign_ptr.hpp:25:30: note: candidate found by name lookup is 'std::weak_ptr' template<typename T> class weak_ptr; ^ /opt/local/include/boost/signals2/detail/foreign_ptr.hpp:42:33: error: redefinition of 'weak_ptr_traits<weak_ptr<type-parameter-0-0> >' template<typename T> struct weak_ptr_traits<std::weak_ptr<T> > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ /opt/local/include/boost/signals2/detail/foreign_ptr.hpp:38:33: note: previous definition is here template<typename T> struct weak_ptr_traits<boost::weak_ptr<T> > ^ /opt/local/include/boost/signals2/detail/foreign_ptr.hpp:54:56: error: reference to 'shared_ptr' is ambiguous template<typename T> struct shared_ptr_traits<std::shared_ptr<T> > ~~~~~^ /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/memory:3847:29: note: candidate found by name lookup is 'std::__1::shared_ptr' class _LIBCPP_TYPE_VIS_ONLY shared_ptr ^ /opt/local/include/boost/signals2/detail/foreign_ptr.hpp:24:30: note: candidate found by name lookup is 'std::shared_ptr' template<typename T> class shared_ptr; ^ /opt/local/include/boost/signals2/detail/foreign_ptr.hpp:54:33: error: redefinition of 'shared_ptr_traits<shared_ptr<type-parameter-0-0> >' template<typename T> struct shared_ptr_traits<std::shared_ptr<T> > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ /opt/local/include/boost/signals2/detail/foreign_ptr.hpp:50:33: note: previous definition is here template<typename T> struct shared_ptr_traits<boost::shared_ptr<T> > ^ 4 errors generated. Thanks Brian