g++     concept.cpp   -o concept
/usr/include/boost/concept_check.hpp: In instantiation of 'boost::CopyConstructible<<unnamed>::MyVisitorAnon>':
/usr/include/boost/concept/detail/has_constraints.hpp:40:   instantiated from 'const bool boost::concept::not_satisfied<boost::CopyConstructible<<unnamed>::MyVisitorAnon> >::value'
/usr/include/boost/concept/detail/has_constraints.hpp:43:   instantiated from 'boost::concept::not_satisfied<boost::CopyConstructible<<unnamed>::MyVisitorAnon> >'
/usr/include/boost/mpl/if.hpp:67:   instantiated from 'boost::mpl::if_<boost::concept::not_satisfied<boost::CopyConstructible<<unnamed>::MyVisitorAnon> >, boost::concept::constraint<boost::CopyConstructible<<unnamed>::MyVisitorAnon> >, boost::concept::requirement<boost::CopyConstructible<<unnamed>::MyVisitorAnon> > >'
/usr/include/boost/concept/detail/general.hpp:19:   instantiated from 'boost::concept::requirement_<void (*)(boost::CopyConstructible<<unnamed>::MyVisitorAnon>)>'
/usr/include/boost/concept_check.hpp:43:   instantiated from 'void boost::function_requires(Model*) [with Model = boost::CopyConstructible<<unnamed>::MyVisitorAnon>]'
concept.cpp:11:   instantiated from here
/usr/include/boost/concept_check.hpp:156: error: 'boost::concept::requirement<Model>::failed [with Model = boost::concept::usage_requirements<boost::CopyConstructible<<unnamed>::MyVisitorAnon> >]' is not a valid template argument for type 'void (*)()' because function 'static void boost::concept::requirement<Model>::failed() [with Model = boost::concept::usage_requirements<boost::CopyConstructible<<unnamed>::MyVisitorAnon> >]' has not external linkage
/usr/include/boost/concept_check.hpp: In function 'void boost::function_requires(Model*) [with Model = boost::CopyConstructible<<unnamed>::MyVisitorAnon>]':
concept.cpp:11:   instantiated from here
/usr/include/boost/concept_check.hpp:43: error: 'boost::concept::requirement<Model>::failed [with Model = boost::CopyConstructible<<unnamed>::MyVisitorAnon>]' is not a valid template argument for type 'void (*)()' because function 'static void boost::concept::requirement<Model>::failed() [with Model = boost::CopyConstructible<<unnamed>::MyVisitorAnon>]' has not external linkage
make: *** [concept] Error 1