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#include <tuple>
#include <memory>
 
 
template<typename T>
struct holder {};
 
struct abstract {
 
   virtual ~abstract() = 0;
};
 
abstract::~abstract() {}
 
 
int main() {
   using types 	   = std::tuple<abstract>;
   using holder_t  = holder<types>;
 
   // Ok
   holder_t local;
 
   // Ok
   new holder_t;
 
   // ?
   std::unique_ptr<holder_t> unique(new holder_t);
 
   // ?
   std::make_shared<holder_t>();
}
 

prog.cpp: In function ‘int main()’:
prog.cpp:21:13: warning: unused variable ‘local’ [-Wunused-variable]
In file included from prog.cpp:1:0:
/usr/include/c++/4.7/tuple: In instantiation of ‘struct std::_Head_base<0u, abstract, false>’:
/usr/include/c++/4.7/tuple:215:12:   required from ‘struct std::_Tuple_impl<0u, abstract>’
/usr/include/c++/4.7/tuple:374:11:   required from ‘class std::tuple<abstract>’
/usr/include/c++/4.7/tuple:744:35:   required from ‘constexpr typename std::__add_ref<typename std::tuple_element<__i, std::tuple<_Elements ...> >::type>::type std::get(std::tuple<_Elements ...>&) [with unsigned int __i = 0u; _Elements = {holder<std::tuple<abstract> >*, std::default_delete<holder<std::tuple<abstract> > >}; typename std::__add_ref<typename std::tuple_element<__i, std::tuple<_Elements ...> >::type>::type = holder<std::tuple<abstract> >*&]’
/usr/include/c++/4.7/bits/unique_ptr.h:171:32:   required from ‘std::unique_ptr<_Tp, _Dp>::~unique_ptr() [with _Tp = holder<std::tuple<abstract> >; _Dp = std::default_delete<holder<std::tuple<abstract> > >]’
prog.cpp:27:49:   required from here
/usr/include/c++/4.7/tuple:166:13: error: cannot declare field ‘std::_Head_base<0u, abstract, false>::_M_head_impl’ to be of abstract type ‘abstract’
prog.cpp:8:8: note:   because the following virtual functions are pure within ‘abstract’:
prog.cpp:13:1: note: 	virtual abstract::~abstract()

Standard output is empty