/in/foo.cc:1:1: error: stray '##' in program
 ##include <iostream>
 ^~
/in/foo.cc:1:3: error: 'include' does not name a type
 ##include <iostream>
   ^~~~~~~
In file included from /usr/include/c++/6/bits/stl_algobase.h:62:0,
                 from /usr/include/c++/6/bits/char_traits.h:39,
                 from /usr/include/c++/6/string:40,
                 from /in/foo.cc:2:
/usr/include/c++/6/ext/type_traits.h:162:35: error: '__gnu_cxx::__is_null_pointer' declared as an 'inline' variable
   __is_null_pointer(std::nullptr_t)
                                   ^
/usr/include/c++/6/ext/type_traits.h:162:35: error: 'bool __gnu_cxx::__is_null_pointer' redeclared as different kind of symbol
/usr/include/c++/6/ext/type_traits.h:157:5: note: previous declaration 'template<class _Type> bool __gnu_cxx::__is_null_pointer(_Type)'
     __is_null_pointer(_Type)
     ^~~~~~~~~~~~~~~~~
/usr/include/c++/6/ext/type_traits.h:162:21: error: 'nullptr_t' is not a member of 'std'
   __is_null_pointer(std::nullptr_t)
                     ^~~
In file included from /usr/include/c++/6/bits/move.h:57:0,
                 from /usr/include/c++/6/bits/stl_pair.h:59,
                 from /usr/include/c++/6/bits/stl_algobase.h:64,
                 from /usr/include/c++/6/bits/char_traits.h:39,
                 from /usr/include/c++/6/string:40,
                 from /in/foo.cc:2:
/usr/include/c++/6/type_traits:359:31: error: 'std::size_t' has not been declared
   template<typename _Tp, std::size_t _Size>
                               ^~~~~~
/usr/include/c++/6/type_traits:360:25: error: '_Size' was not declared in this scope
     struct is_array<_Tp[_Size]>
                         ^~~~~
/usr/include/c++/6/type_traits:360:31: error: template argument 1 is invalid
     struct is_array<_Tp[_Size]>
                               ^
/usr/include/c++/6/type_traits:558:37: error: 'nullptr_t' is not a member of 'std'
     struct __is_null_pointer_helper<std::nullptr_t>
                                     ^~~
/usr/include/c++/6/type_traits:558:37: error: 'nullptr_t' is not a member of 'std'
/usr/include/c++/6/type_traits:558:51: error: template argument 1 is invalid
     struct __is_null_pointer_helper<std::nullptr_t>
                                                   ^
/usr/include/c++/6/type_traits:1478:32: error: 'size_t' is not a member of 'std'
     : public integral_constant<std::size_t, __alignof__(_Tp)> { };
                                ^~~
/usr/include/c++/6/type_traits:1478:32: error: 'size_t' is not a member of 'std'
/usr/include/c++/6/type_traits:1478:61: error: template argument 1 is invalid
     : public integral_constant<std::size_t, __alignof__(_Tp)> { };
                                                             ^
/usr/include/c++/6/type_traits:1478:61: note: invalid template non-type parameter
/usr/include/c++/6/type_traits:1483:32: error: 'size_t' is not a member of 'std'
     : public integral_constant<std::size_t, 0> { };
                                ^~~
/usr/include/c++/6/type_traits:1483:32: error: 'size_t' is not a member of 'std'
/usr/include/c++/6/type_traits:1483:46: error: template argument 1 is invalid
     : public integral_constant<std::size_t, 0> { };
                                              ^
/usr/include/c++/6/type_traits:1483:46: note: invalid template non-type parameter
/usr/include/c++/6/type_traits:1485:31: error: 'std::size_t' has not been declared
   template<typename _Tp, std::size_t _Size>
                               ^~~~~~
/usr/include/c++/6/type_traits:1486:21: error: '_Size' was not declared in this scope
     struct rank<_Tp[_Size]>
                     ^~~~~
/usr/include/c++/6/type_traits:1486:27: error: template argument 1 is invalid
     struct rank<_Tp[_Size]>
                           ^
/usr/include/c++/6/type_traits:1487:32: error: 'size_t' is not a member of 'std'
     : public integral_constant<std::size_t, 1 + rank<_Tp>::value> { };
                                ^~~
/usr/include/c++/6/type_traits:1487:32: error: 'size_t' is not a member of 'std'
/usr/include/c++/6/type_traits:1487:65: error: template argument 1 is invalid
     : public integral_constant<std::size_t, 1 + rank<_Tp>::value> { };
                                                                 ^
/usr/include/c++/6/type_traits:1487:65: note: invalid template non-type parameter
/usr/include/c++/6/type_traits:1491:32: error: 'size_t' is not a member of 'std'
     : public integral_constant<std::size_t, 1 + rank<_Tp>::value> { };
                                ^~~
/usr/include/c++/6/type_traits:1491:32: error: 'size_t' is not a member of 'std'
/usr/include/c++/6/type_traits:1491:65: error: template argument 1 is invalid
     : public integral_constant<std::size_t, 1 + rank<_Tp>::value> { };
                                                                 ^
/usr/include/c++/6/type_traits:1491:65: note: invalid template non-type parameter
/usr/include/c++/6/type_traits:1496:32: error: 'size_t' is not a member of 'std'
     : public integral_constant<std::size_t, 0> { };
                                ^~~
/usr/include/c++/6/type_traits:1496:32: error: 'size_t' is not a member of 'std'
/usr/include/c++/6/type_traits:1496:46: error: template argument 1 is invalid
     : public integral_constant<std::size_t, 0> { };
                                              ^
/usr/include/c++/6/type_traits:1496:46: note: invalid template non-type parameter
/usr/include/c++/6/type_traits:1498:47: error: 'std::size_t' has not been declared
   template<typename _Tp, unsigned _Uint, std::size_t _Size>
                                               ^~~~~~
/usr/include/c++/6/type_traits:1499:23: error: '_Size' was not declared in this scope
     struct extent<_Tp[_Size], _Uint>
                       ^~~~~
/usr/include/c++/6/type_traits:1499:36: error: template argument 1 is invalid
     struct extent<_Tp[_Size], _Uint>
                                    ^
/usr/include/c++/6/type_traits:1500:32: error: 'size_t' is not a member of 'std'
     : public integral_constant<std::size_t,
                                ^~~
/usr/include/c++/6/type_traits:1500:32: error: 'size_t' is not a member of 'std'
/usr/include/c++/6/type_traits:1501:24: error: '_Size' was not declared in this scope
           _Uint == 0 ? _Size : extent<_Tp,
                        ^~~~~
/usr/include/c++/6/type_traits:1502:28: error: template argument 1 is invalid
           _Uint - 1>::value>
                            ^
/usr/include/c++/6/type_traits:1502:28: note: invalid template non-type parameter
/usr/include/c++/6/type_traits:1507:32: error: 'size_t' is not a member of 'std'
     : public integral_constant<std::size_t,
                                ^~~
/usr/include/c++/6/type_traits:1507:32: error: 'size_t' is not a member of 'std'
/usr/include/c++/6/type_traits:1509:31: error: template argument 1 is invalid
              _Uint - 1>::value>
                               ^
/usr/include/c++/6/type_traits:1509:31: note: invalid template non-type parameter
/usr/include/c++/6/type_traits:1958:31: error: 'std::size_t' has not been declared
   template<typename _Tp, std::size_t _Size>
                               ^~~~~~
/usr/include/c++/6/type_traits:1959:30: error: '_Size' was not declared in this scope
     struct remove_extent<_Tp[_Size]>
                              ^~~~~
/usr/include/c++/6/type_traits:1959:36: error: template argument 1 is invalid
     struct remove_extent<_Tp[_Size]>
                                    ^
/usr/include/c++/6/type_traits:1971:31: error: 'std::size_t' has not been declared
   template<typename _Tp, std::size_t _Size>
                               ^~~~~~
/usr/include/c++/6/type_traits:1972:35: error: '_Size' was not declared in this scope
     struct remove_all_extents<_Tp[_Size]>
                                   ^~~~~
/usr/include/c++/6/type_traits:1972:41: error: template argument 1 is invalid
     struct remove_all_extents<_Tp[_Size]>
                                         ^
/usr/include/c++/6/type_traits:2030:17: error: 'std::size_t' has not been declared
   template<std::size_t _Len>
                 ^~~~~~
/usr/include/c++/6/type_traits:2035:23: erro