/in/foo.cc:3:1: error: stray '`' in program
 ```cpp
 ^
/in/foo.cc:3:2: error: stray '`' in program
 ```cpp
  ^
/in/foo.cc:3:3: error: stray '`' in program
 ```cpp
   ^
/in/foo.cc:3:4: error: 'cpp' does not name a type
 ```cpp
    ^~~
In file included from /usr/include/c++/6/cmath:43:0,
                 from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:41,
                 from /in/foo.cc:6:
/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/nested_exception.h:40,
                 from /usr/include/c++/6/exception:173,
                 from /usr/include/c++/6/ios:39,
                 from /usr/include/c++/6/istream:38,
                 from /usr/include/c++/6/sstream:38,
                 from /usr/include/c++/6/complex:45,
                 from /usr/include/c++/6/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:52,
                 from /in/foo.cc:6:
/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: note: suggested alternative:
In file included from /usr/include/c++/6/cstddef:50:0,
                 from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:45,
                 from /in/foo.cc:6:
/usr/lib/gcc/x86_64-linux-gnu/6/include/stddef.h:436:29: note:   'nullptr_t'
   typedef decltype(nullptr) nullptr_t;
                             ^~~~~~~~~
In file included from /usr/include/c++/6/bits/move.h:57:0,
                 from /usr/include/c++/6/bits/nested_exception.h:40,
                 from /usr/include/c++/6/exception:173,
                 from /usr/include/c++/6/ios:39,
                 from /usr/include/c++/6/istream:38,
                 from /usr/include/c++/6/sstream:38,
                 from /usr/include/c++/6/complex:45,
                 from /usr/include/c++/6/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:52,
                 from /in/foo.cc:6:
/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: note: suggested alternative:
In file included from /usr/include/c++/6/cstddef:50:0,
                 from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:45,
                 from /in/foo.cc:6:
/usr/lib/gcc/x86_64-linux-gnu/6/include/stddef.h:436:29: note:   'nullptr_t'
   typedef decltype(nullptr) nullptr_t;
                             ^~~~~~~~~
In file included from /usr/include/c++/6/bits/move.h:57:0,
                 from /usr/include/c++/6/bits/nested_exception.h:40,
                 from /usr/include/c++/6/exception:173,
                 from /usr/include/c++/6/ios:39,
                 from /usr/include/c++/6/istream:38,
                 from /usr/include/c++/6/sstream:38,
                 from /usr/include/c++/6/complex:45,
                 from /usr/include/c++/6/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:52,
                 from /in/foo.cc:6:
/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: note: suggested alternative:
In file included from /usr/include/signal.h:316:0,
                 from /usr/include/c++/6/csignal:42,
                 from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:43,
                 from /in/foo.cc:6:
/usr/lib/gcc/x86_64-linux-gnu/6/include/stddef.h:216:23: note:   'size_t'
 typedef __SIZE_TYPE__ size_t;
                       ^~~~~~
In file included from /usr/include/c++/6/bits/move.h:57:0,
                 from /usr/include/c++/6/bits/nested_exception.h:40,
                 from /usr/include/c++/6/exception:173,
                 from /usr/include/c++/6/ios:39,
                 from /usr/include/c++/6/istream:38,
                 from /usr/include/c++/6/sstream:38,
                 from /usr/include/c++/6/complex:45,
                 from /usr/include/c++/6/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:52,
                 from /in/foo.cc:6:
/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: note: suggested alternative:
In file included from /usr/include/signal.h:316:0,
                 from /usr/include/c++/6/csignal:42,
                 from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:43,
                 from /in/foo.cc:6:
/usr/lib/gcc/x86_64-linux-gnu/6/include/stddef.h:216:23: note:   'size_t'
 typedef __SIZE_TYPE__ size_t;
                       ^~~~~~
In file included from /usr/include/c++/6/bits/move.h:57:0,
                 from /usr/include/c++/6/bits/nested_exception.h:40,
                 from /usr/include/c++/6/exception:173,
                 from /usr/include/c++/6/ios:39,
                 from /usr/include/c++/6/istream:38,
                 from /usr/include/c++/6/sstream:38,
                 from /usr/include/c++/6/complex:45,
                 from /usr/include/c++/6/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:52,
                 from /in/foo.cc:6:
/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: note: suggested alternative:
In file included from /usr/include/signal.h:316:0,
                 from /usr/include/c++/6/csignal:42,
                 from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:43,
                 from /in/foo.cc:6:
/usr/lib/gcc/x86_64-linux-gnu/6/include/stddef.h:216:23: note:   'size_t'
 typedef __SIZE_TYPE__ size_t;
                       ^~~~~~
In file included from /usr/include/c++/6/bits/move.h:57:0,
                 from /usr/include/c++/6/bits/nested_exception.h:40,
                 from /usr/include/c++/6/exception:173,
                 from /usr/include/c++/6/ios:39,
                 from /usr/include/c++/6/istream:38,
                 from /usr/include/c++/6/sstream:38,
                 from /usr/include/c++/6/complex:45,
                 from /usr/include/c++/6/ccomplex:39,
                 from /usr/in