f.cc: In function 'int main()':
f.cc:8:35: error: no match for 'operator==' (operand types are 'std::basic_istream<char>::__istream_type {aka std::basic_istream<char>}' and 'int')
   if (cin.getline (x, sizeof (x)) == 0)
                                   ^
f.cc:8:35: note: candidate: operator==(int, int) <built-in>
f.cc:8:35: note:   no known conversion for argument 1 from 'std::basic_istream<char>::__istream_type {aka std::basic_istream<char>}' to 'int'
In file included from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/iosfwd:40:0,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/ios:38,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/ostream:38,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/iostream:39,
                 from f.cc:1:
/home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/postypes.h:216:5: note: candidate: template<class _StateT> bool std::operator==(const std::fpos<_StateT>&, const std::fpos<_StateT>&)
     operator==(const fpos<_StateT>& __lhs, const fpos<_StateT>& __rhs)
     ^
/home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/postypes.h:216:5: note:   template argument deduction/substitution failed:
f.cc:8:38: note:   'std::basic_istream<char>::__istream_type {aka std::basic_istream<char>}' is not derived from 'const std::fpos<_StateT>'
   if (cin.getline (x, sizeof (x)) == 0)
                                      ^
In file included from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/stl_algobase.h:64:0,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/char_traits.h:39,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/ios:40,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/ostream:38,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/iostream:39,
                 from f.cc:1:
/home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/stl_pair.h:330:5: note: candidate: template<class _T1, class _T2> constexpr bool std::operator==(const std::pair<_T1, _T2>&, const std::pair<_T1, _T2>&)
     operator==(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
     ^
/home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/stl_pair.h:330:5: note:   template argument deduction/substitution failed:
f.cc:8:38: note:   'std::basic_istream<char>::__istream_type {aka std::basic_istream<char>}' is not derived from 'const std::pair<_T1, _T2>'
   if (cin.getline (x, sizeof (x)) == 0)
                                      ^
In file included from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/stl_algobase.h:67:0,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/char_traits.h:39,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/ios:40,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/ostream:38,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/iostream:39,
                 from f.cc:1:
/home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/stl_iterator.h:292:5: note: candidate: template<class _Iterator> bool std::operator==(const std::reverse_iterator<_Iterator>&, const std::reverse_iterator<_Iterator>&)
     operator==(const reverse_iterator<_Iterator>& __x,
     ^
/home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/stl_iterator.h:292:5: note:   template argument deduction/substitution failed:
f.cc:8:38: note:   'std::basic_istream<char>::__istream_type {aka std::basic_istream<char>}' is not derived from 'const std::reverse_iterator<_Iterator>'
   if (cin.getline (x, sizeof (x)) == 0)
                                      ^
In file included from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/stl_algobase.h:67:0,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/char_traits.h:39,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/ios:40,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/ostream:38,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/iostream:39,
                 from f.cc:1:
/home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/stl_iterator.h:342:5: note: candidate: template<class _IteratorL, class _IteratorR> bool std::operator==(const std::reverse_iterator<_Iterator>&, const std::reverse_iterator<_IteratorR>&)
     operator==(const reverse_iterator<_IteratorL>& __x,
     ^
/home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/stl_iterator.h:342:5: note:   template argument deduction/substitution failed:
f.cc:8:38: note:   'std::basic_istream<char>::__istream_type {aka std::basic_istream<char>}' is not derived from 'const std::reverse_iterator<_Iterator>'
   if (cin.getline (x, sizeof (x)) == 0)
                                      ^
In file included from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/stl_algobase.h:67:0,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/char_traits.h:39,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/ios:40,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/ostream:38,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/iostream:39,
                 from f.cc:1:
/home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/stl_iterator.h:1104:5: note: candidate: template<class _IteratorL, class _IteratorR> bool std::operator==(const std::move_iterator<_IteratorL>&, const std::move_iterator<_IteratorR>&)
     operator==(const move_iterator<_IteratorL>& __x,
     ^
/home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/stl_iterator.h:1104:5: note:   template argument deduction/substitution failed:
f.cc:8:38: note:   'std::basic_istream<char>::__istream_type {aka std::basic_istream<char>}' is not derived from 'const std::move_iterator<_IteratorL>'
   if (cin.getline (x, sizeof (x)) == 0)
                                      ^
In file included from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/stl_algobase.h:67:0,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/char_traits.h:39,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/ios:40,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/ostream:38,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/iostream:39,
                 from f.cc:1:
/home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/stl_iterator.h:1110:5: note: candidate: template<class _Iterator> bool std::operator==(const std::move_iterator<_IteratorL>&, const std::move_iterator<_IteratorL>&)
     operator==(const move_iterator<_Iterator>& __x,
     ^
/home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/stl_iterator.h:1110:5: note:   template argument deduction/substitution failed:
f.cc:8:38: note:   'std::basic_istream<char>::__istream_type {aka std::basic_istream<char>}' is not derived from 'const std::move_iterator<_IteratorL>'
   if (cin.getline (x, sizeof (x)) == 0)
                                      ^
In file included from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/string:41:0,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/locale_classes.h:40,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/ios_base.h:41,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/ios:42,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/ostream:38,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/iostream:39,
                 from f.cc:1:
/home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/allocator.h:131:5: note: candidate: template<class _T1, class _T2> bool std::operator==(const std::allocator<_CharT>&, const std::allocator<_T2>&)
     operator==(const allocator<_T1>&, const allocator<_T2>&)
     ^
/home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/allocator.h:131:5: note:   template argument deduction/substitution failed:
f.cc:8:38: note:   'std::basic_istream<char>::__istream_type {aka std::basic_istream<char>}' is not derived from 'const std::allocator<_CharT>'
   if (cin.getline (x, sizeof (x)) == 0)
                                      ^
In file included from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/string:41:0,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/locale_classes.h:40,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/ios_base.h:41,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/ios:42,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/ostream:38,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/iostream:39,
                 from f.cc:1:
/home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/allocator.h:137:5: note: candidate: template<class _Tp> bool std::operator==(const std::allocator<_CharT>&, const std::allocator<_CharT>&)
     operator==(const allocator<_Tp>&, const allocator<_Tp>&)
     ^
/home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/allocator.h:137:5: note:   template argument deduction/substitution failed:
f.cc:8:38: note:   'std::basic_istream<char>::__istream_type {aka std::basic_istream<char>}' is not derived from 'const std::allocator<_CharT>'
   if (cin.getline (x, sizeof (x)) == 0)
                                      ^
In file included from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/string:52:0,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/locale_classes.h:40,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/ios_base.h:41,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/ios:42,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/ostream:38,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/iostream:39,
                 from f.cc:1:
/home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/basic_string.h:4933:5: note: candidate: template<class _CharT, class _Traits, class _Alloc> bool std::operator==(const std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&, const std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&)
     operator==(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
     ^
/home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/basic_string.h:4933:5: note:   template argument deduction/substitution failed:
f.cc:8:38: note:   'std::basic_istream<char>::__istream_type {aka std::basic_istream<char>}' is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Alloc>'
   if (cin.getline (x, sizeof (x)) == 0)
                                      ^
In file included from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/string:52:0,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/locale_classes.h:40,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/ios_base.h:41,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/ios:42,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/ostream:38,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/iostream:39,
                 from f.cc:1:
/home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/basic_string.h:4940:5: note: candidate: template<class _CharT> typename __gnu_cxx::__enable_if<std::__is_char<_Tp>::__value, bool>::__type std::operator==(const std::__cxx11::basic_string<_CharT>&, const std::__cxx11::basic_string<_CharT>&)
     operator==(const basic_string<_CharT>& __lhs,
     ^
/home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/basic_string.h:4940:5: note:   template argument deduction/substitution failed:
f.cc:8:38: note:   'std::basic_istream<char>::__istream_type {aka std::basic_istream<char>}' is not derived from 'const std::__cxx11::basic_string<_CharT>'
   if (cin.getline (x, sizeof (x)) == 0)
                                      ^
In file included from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/string:52:0,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/locale_classes.h:40,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/ios_base.h:41,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/ios:42,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/ostream:38,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/iostream:39,
                 from f.cc:1:
/home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/basic_string.h:4954:5: note: candidate: template<class _CharT, class _Traits, class _Alloc> bool std::operator==(const _CharT*, const std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&)
     operator==(const _CharT* __lhs,
     ^
/home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/basic_string.h:4954:5: note:   template argument deduction/substitution failed:
f.cc:8:38: note:   mismatched types 'const _CharT*' and 'std::basic_istream<char>'
   if (cin.getline (x, sizeof (x)) == 0)
                                      ^
In file included from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/string:52:0,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/locale_classes.h:40,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/ios_base.h:41,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/ios:42,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/ostream:38,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/iostream:39,
                 from f.cc:1:
/home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/basic_string.h:4966:5: note: candidate: template<class _CharT, class _Traits, class _Alloc> bool std::operator==(const std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&, const _CharT*)
     operator==(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
     ^
/home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/basic_string.h:4966:5: note:   template argument deduction/substitution failed:
f.cc:8:38: note:   'std::basic_istream<char>::__istream_type {aka std::basic_istream<char>}' is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Alloc>'
   if (cin.getline (x, sizeof (x)) == 0)
                                      ^
In file included from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/ios_base.h:46:0,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/ios:42,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/ostream:38,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/iostream:39,
                 from f.cc:1:
/home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/system_error:284:3: note: candidate: bool std::operator==(const std::error_code&, const std::error_code&)
   operator==(const error_code& __lhs, const error_code& __rhs) noexcept
   ^
/home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/system_error:284:3: note:   no known conversion for argument 1 from 'std::basic_istream<char>::__istream_type {aka std::basic_istream<char>}' to 'const std::error_code&'
/home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/system_error:289:3: note: candidate: bool std::operator==(const std::error_code&, const std::error_condition&)
   operator==(const error_code& __lhs, const error_condition& __rhs) noexcept
   ^
/home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/system_error:289:3: note:   no known conversion for argument 1 from 'std::basic_istream<char>::__istream_type {aka std::basic_istream<char>}' to 'const std::error_code&'
/home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/system_error:296:3: note: candidate: bool std::operator==(const std::error_condition&, const std::error_code&)
   operator==(const error_condition& __lhs, const error_code& __rhs) noexcept
   ^
/home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/system_error:296:3: note:   no known conversion for argument 1 from 'std::basic_istream<char>::__istream_type {aka std::basic_istream<char>}' to 'const std::error_condition&'
/home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/system_error:303:3: note: candidate: bool std::operator==(const std::error_condition&, const std::error_condition&)
   operator==(const error_condition& __lhs,
   ^
/home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/system_error:303:3: note:   no known conversion for argument 1 from 'std::basic_istream<char>::__istream_type {aka std::basic_istream<char>}' to 'const std::error_condition&'
In file included from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/locale_facets.h:48:0,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/basic_ios.h:37,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/ios:44,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/ostream:38,
                 from /home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/iostream:39,
                 from f.cc:1:
/home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/streambuf_iterator.h:204:5: note: candidate: template<class _CharT, class _Traits> bool std::operator==(const std::istreambuf_iterator<_CharT, _Traits>&, const std::istreambuf_iterator<_CharT, _Traits>&)
     operator==(const istreambuf_iterator<_CharT, _Traits>& __a,
     ^
/home/bilbo/gnu-toolchain/armhf-build/builds/destdir/x86_64-unknown-linux-gnu/arm-linux-gnueabihf/include/c++/6.0.0/bits/streambuf_iterator.h:204:5: note:   template argument deduction/substitution failed:
f.cc:8:38: note:   'std::basic_istream<char>::__istream_type {aka std::basic_istream<char>}' is not derived from 'const std::istreambuf_iterator<_CharT, _Traits>'
   if (cin.getline (x, sizeof (x)) == 0)
                                      ^