foo.cc:1:1: error: stray '\345' in program
 很简单，推理一下就行
 ^
foo.cc:1:2: error: stray '\276' in program
 很简单，推理一下就行
  ^
foo.cc:1:3: error: stray '\210' in program
 很简单，推理一下就行
   ^
foo.cc:1:4: error: stray '\347' in program
 很简单，推理一下就行
    ^
foo.cc:1:5: error: stray '\256' in program
 很简单，推理一下就行
     ^
foo.cc:1:6: error: stray '\200' in program
 很简单，推理一下就行
      ^
foo.cc:1:7: error: stray '\345' in program
 很简单，推理一下就行
       ^
foo.cc:1:8: error: stray '\215' in program
 很简单，推理一下就行
        ^
foo.cc:1:9: error: stray '\225' in program
 很简单，推理一下就行
         ^
foo.cc:1:10: error: stray '\357' in program
 很简单，推理一下就行
          ^
foo.cc:1:11: error: stray '\274' in program
 很简单，推理一下就行
           ^
foo.cc:1:12: error: stray '\214' in program
 很简单，推理一下就行
            ^
foo.cc:1:13: error: stray '\346' in program
 很简单，推理一下就行
             ^
foo.cc:1:14: error: stray '\216' in program
 很简单，推理一下就行
              ^
foo.cc:1:15: error: stray '\250' in program
 很简单，推理一下就行
               ^
foo.cc:1:16: error: stray '\347' in program
 很简单，推理一下就行
                ^
foo.cc:1:17: error: stray '\220' in program
 很简单，推理一下就行
                 ^
foo.cc:1:18: error: stray '\206' in program
 很简单，推理一下就行
                  ^
foo.cc:1:19: error: stray '\344' in program
 很简单，推理一下就行
                   ^
foo.cc:1:20: error: stray '\270' in program
 很简单，推理一下就行
                    ^
foo.cc:1:21: error: stray '\200' in program
 很简单，推理一下就行
                     ^
foo.cc:1:22: error: stray '\344' in program
 很简单，推理一下就行
                      ^
foo.cc:1:23: error: stray '\270' in program
 很简单，推理一下就行
                       ^
foo.cc:1:24: error: stray '\213' in program
 很简单，推理一下就行
                        ^
foo.cc:1:25: error: stray '\345' in program
 很简单，推理一下就行
                         ^
foo.cc:1:26: error: stray '\260' in program
 很简单，推理一下就行
                          ^
foo.cc:1:27: error: stray '\261' in program
 很简单，推理一下就行
                           ^
foo.cc:1:28: error: stray '\350' in program
 很简单，推理一下就行
                            ^
foo.cc:1:29: error: stray '\241' in program
 很简单，推理一下就行
                             ^
foo.cc:1:30: error: stray '\214' in program
 很简单，推理一下就行
                              ^
foo.cc:4:1: error: stray '`' in program
 ```cpp
 ^
foo.cc:4:2: error: stray '`' in program
 ```cpp
  ^
foo.cc:4:3: error: stray '`' in program
 ```cpp
   ^
foo.cc:13:1: error: stray '`' in program
 ```
 ^
foo.cc:13:2: error: stray '`' in program
 ```
  ^
foo.cc:13:3: error: stray '`' in program
 ```
   ^
foo.cc:4:4: error: 'cpp' does not name a type
 ```cpp
    ^~~
In file included from /usr/include/c++/7/iosfwd:40:0,
                 from /usr/include/c++/7/ios:38,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/postypes.h:98:11: error: 'ptrdiff_t' does not name a type
   typedef ptrdiff_t streamsize; // Signed integral type
           ^~~~~~~~~
In file included from /usr/include/c++/7/bits/exception_ptr.h:40:0,
                 from /usr/include/c++/7/exception:142,
                 from /usr/include/c++/7/ios:39,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/new:120:31: error: declaration of 'operator new' as non-function
 void* operator new(std::size_t) _GLIBCXX_THROW (std::bad_alloc)
                               ^
/usr/include/c++/7/new:120:25: error: 'size_t' is not a member of 'std'
 void* operator new(std::size_t) _GLIBCXX_THROW (std::bad_alloc)
                         ^~~~~~
/usr/include/c++/7/new:120:25: note: suggested alternative:
In file included from /usr/include/wchar.h:35:0,
                 from /usr/include/c++/7/cwchar:44,
                 from /usr/include/c++/7/bits/postypes.h:40,
                 from /usr/include/c++/7/iosfwd:40,
                 from /usr/include/c++/7/ios:38,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/lib/gcc/x86_64-linux-gnu/7/include/stddef.h:216:23: note:   'size_t'
 typedef __SIZE_TYPE__ size_t;
                       ^~~~~~
In file included from /usr/include/c++/7/bits/exception_ptr.h:40:0,
                 from /usr/include/c++/7/exception:142,
                 from /usr/include/c++/7/ios:39,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/new:122:33: error: declaration of 'operator new []' as non-function
 void* operator new[](std::size_t) _GLIBCXX_THROW (std::bad_alloc)
                                 ^
/usr/include/c++/7/new:122:27: error: 'size_t' is not a member of 'std'
 void* operator new[](std::size_t) _GLIBCXX_THROW (std::bad_alloc)
                           ^~~~~~
/usr/include/c++/7/new:122:27: note: suggested alternative:
In file included from /usr/include/wchar.h:35:0,
                 from /usr/include/c++/7/cwchar:44,
                 from /usr/include/c++/7/bits/postypes.h:40,
                 from /usr/include/c++/7/iosfwd:40,
                 from /usr/include/c++/7/ios:38,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/lib/gcc/x86_64-linux-gnu/7/include/stddef.h:216:23: note:   'size_t'
 typedef __SIZE_TYPE__ size_t;
                       ^~~~~~
In file included from /usr/include/c++/7/bits/exception_ptr.h:40:0,
                 from /usr/include/c++/7/exception:142,
                 from /usr/include/c++/7/ios:39,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/new:134:25: error: declaration of 'operator new' as non-function
 void* operator new(std::size_t, const std::nothrow_t&) _GLIBCXX_USE_NOEXCEPT
                         ^~~~~~
/usr/include/c++/7/new:134:25: error: 'size_t' is not a member of 'std'
/usr/include/c++/7/new:134:25: note: suggested alternative:
In file included from /usr/include/wchar.h:35:0,
                 from /usr/include/c++/7/cwchar:44,
                 from /usr/include/c++/7/bits/postypes.h:40,
                 from /usr/include/c++/7/iosfwd:40,
                 from /usr/include/c++/7/ios:38,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/lib/gcc/x86_64-linux-gnu/7/include/stddef.h:216:23: note:   'size_t'
 typedef __SIZE_TYPE__ size_t;
                       ^~~~~~
In file included from /usr/include/c++/7/bits/exception_ptr.h:40:0,
                 from /usr/include/c++/7/exception:142,
                 from /usr/include/c++/7/ios:39,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/new:134:33: error: expected primary-expression before 'const'
 void* operator new(std::size_t, const std::nothrow_t&) _GLIBCXX_USE_NOEXCEPT
                                 ^~~~~
/usr/include/c++/7/new:136:27: error: declaration of 'operator new []' as non-function
 void* operator new[](std::size_t, const std::nothrow_t&) _GLIBCXX_USE_NOEXCEPT
                           ^~~~~~
/usr/include/c++/7/new:136:27: error: 'size_t' is not a member of 'std'
/usr/include/c++/7/new:136:27: note: suggested alternative:
In file included from /usr/include/wchar.h:35:0,
                 from /usr/include/c++/7/cwchar:44,
                 from /usr/include/c++/7/bits/postypes.h:40,
                 from /usr/include/c++/7/iosfwd:40,
                 from /usr/include/c++/7/ios:38,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/lib/gcc/x86_64-linux-gnu/7/include/stddef.h:216:23: note:   'size_t'
 typedef __SIZE_TYPE__ size_t;
                       ^~~~~~
In file included from /usr/include/c++/7/bits/exception_ptr.h:40:0,
                 from /usr/include/c++/7/exception:142,
                 from /usr/include/c++/7/ios:39,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/new:136:35: error: expected primary-expression before 'const'
 void* operator new[](std::size_t, const std::nothrow_t&) _GLIBCXX_USE_NOEXCEPT
                                   ^~~~~
/usr/include/c++/7/new:168:32: error: declaration of 'operator new' as non-function
 inline void* operator new(std::size_t, void* __p) _GLIBCXX_USE_NOEXCEPT
                                ^~~~~~
/usr/include/c++/7/new:168:32: error: 'size_t' is not a member of 'std'
/usr/include/c++/7/new:168:32: note: suggested alternative:
In file included from /usr/include/wchar.h:35:0,
                 from /usr/include/c++/7/cwchar:44,
                 from /usr/include/c++/7/bits/postypes.h:40,
                 from /usr/include/c++/7/iosfwd:40,
                 from /usr/include/c++/7/ios:38,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/lib/gcc/x86_64-linux-gnu/7/include/stddef.h:216:23: note:   'size_t'
 typedef __SIZE_TYPE__ size_t;
                       ^~~~~~
In file included from /usr/include/c++/7/bits/exception_ptr.h:40:0,
                 from /usr/include/c++/7/exception:142,
                 from /usr/include/c++/7/ios:39,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/new:168:40: error: expected primary-expression before 'void'
 inline void* operator new(std::size_t, void* __p) _GLIBCXX_USE_NOEXCEPT
                                        ^~~~
/usr/include/c++/7/new:170:34: error: declaration of 'operator new []' as non-function
 inline void* operator new[](std::size_t, void* __p) _GLIBCXX_USE_NOEXCEPT
                                  ^~~~~~
/usr/include/c++/7/new:170:34: error: 'size_t' is not a member of 'std'
/usr/include/c++/7/new:170:34: note: suggested alternative:
In file included from /usr/include/wchar.h:35:0,
                 from /usr/include/c++/7/cwchar:44,
                 from /usr/include/c++/7/bits/postypes.h:40,
                 from /usr/include/c++/7/iosfwd:40,
                 from /usr/include/c++/7/ios:38,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/lib/gcc/x86_64-linux-gnu/7/include/stddef.h:216:23: note:   'size_t'
 typedef __SIZE_TYPE__ size_t;
                       ^~~~~~
In file included from /usr/include/c++/7/bits/exception_ptr.h:40:0,
                 from /usr/include/c++/7/exception:142,
                 from /usr/include/c++/7/ios:39,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/new:170:42: error: expected primary-expression before 'void'
 inline void* operator new[](std::size_t, void* __p) _GLIBCXX_USE_NOEXCEPT
                                          ^~~~
In file included from /usr/include/c++/7/bits/move.h:54:0,
                 from /usr/include/c++/7/bits/nested_exception.h:40,
                 from /usr/include/c++/7/exception:143,
                 from /usr/include/c++/7/ios:39,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/type_traits:362:31: error: 'std::size_t' has not been declared
   template<typename _Tp, std::size_t _Size>
                               ^~~~~~
/usr/include/c++/7/type_traits:363:25: error: '_Size' was not declared in this scope
     struct is_array<_Tp[_Size]>
                         ^~~~~
/usr/include/c++/7/type_traits:363:31: error: template argument 1 is invalid
     struct is_array<_Tp[_Size]>
                               ^
/usr/include/c++/7/type_traits:561:42: error: 'nullptr_t' is not a member of 'std'
     struct __is_null_pointer_helper<std::nullptr_t>
                                          ^~~~~~~~~
/usr/include/c++/7/type_traits:561:42: note: suggested alternative:
In file included from /usr/include/c++/7/bits/cxxabi_init_exception.h:38:0,
                 from /usr/include/c++/7/bits/exception_ptr.h:38,
                 from /usr/include/c++/7/exception:142,
                 from /usr/include/c++/7/ios:39,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/lib/gcc/x86_64-linux-gnu/7/include/stddef.h:444:29: note:   'nullptr_t'
   typedef decltype(nullptr) nullptr_t;
                             ^~~~~~~~~
In file included from /usr/include/c++/7/bits/move.h:54:0,
                 from /usr/include/c++/7/bits/nested_exception.h:40,
                 from /usr/include/c++/7/exception:143,
                 from /usr/include/c++/7/ios:39,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/type_traits:561:42: error: 'nullptr_t' is not a member of 'std'
     struct __is_null_pointer_helper<std::nullptr_t>
                                          ^~~~~~~~~
/usr/include/c++/7/type_traits:561:42: note: suggested alternative:
In file included from /usr/include/c++/7/bits/cxxabi_init_exception.h:38:0,
                 from /usr/include/c++/7/bits/exception_ptr.h:38,
                 from /usr/include/c++/7/exception:142,
                 from /usr/include/c++/7/ios:39,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/lib/gcc/x86_64-linux-gnu/7/include/stddef.h:444:29: note:   'nullptr_t'
   typedef decltype(nullptr) nullptr_t;
                             ^~~~~~~~~
In file included from /usr/include/c++/7/bits/move.h:54:0,
                 from /usr/include/c++/7/bits/nested_exception.h:40,
                 from /usr/include/c++/7/exception:143,
                 from /usr/include/c++/7/ios:39,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/type_traits:561:51: error: template argument 1 is invalid
     struct __is_null_pointer_helper<std::nullptr_t>
                                                   ^
/usr/include/c++/7/type_traits:1464:37: error: 'size_t' is not a member of 'std'
     : public integral_constant<std::size_t, __alignof__(_Tp)> { };
                                     ^~~~~~
/usr/include/c++/7/type_traits:1464:37: note: suggested alternative:
In file included from /usr/include/wchar.h:35:0,
                 from /usr/include/c++/7/cwchar:44,
                 from /usr/include/c++/7/bits/postypes.h:40,
                 from /usr/include/c++/7/iosfwd:40,
                 from /usr/include/c++/7/ios:38,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/lib/gcc/x86_64-linux-gnu/7/include/stddef.h:216:23: note:   'size_t'
 typedef __SIZE_TYPE__ size_t;
                       ^~~~~~
In file included from /usr/include/c++/7/bits/move.h:54:0,
                 from /usr/include/c++/7/bits/nested_exception.h:40,
                 from /usr/include/c++/7/exception:143,
                 from /usr/include/c++/7/ios:39,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/type_traits:1464:37: error: 'size_t' is not a member of 'std'
     : public integral_constant<std::size_t, __alignof__(_Tp)> { };
                                     ^~~~~~
/usr/include/c++/7/type_traits:1464:37: note: suggested alternative:
In file included from /usr/include/wchar.h:35:0,
                 from /usr/include/c++/7/cwchar:44,
                 from /usr/include/c++/7/bits/postypes.h:40,
                 from /usr/include/c++/7/iosfwd:40,
                 from /usr/include/c++/7/ios:38,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/lib/gcc/x86_64-linux-gnu/7/include/stddef.h:216:23: note:   'size_t'
 typedef __SIZE_TYPE__ size_t;
                       ^~~~~~
In file included from /usr/include/c++/7/bits/move.h:54:0,
                 from /usr/include/c++/7/bits/nested_exception.h:40,
                 from /usr/include/c++/7/exception:143,
                 from /usr/include/c++/7/ios:39,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/type_traits:1464:61: error: template argument 1 is invalid
     : public integral_constant<std::size_t, __alignof__(_Tp)> { };
                                                             ^
/usr/include/c++/7/type_traits:1464:61: note: invalid template non-type parameter
/usr/include/c++/7/type_traits:1469:37: error: 'size_t' is not a member of 'std'
     : public integral_constant<std::size_t, 0> { };
                                     ^~~~~~
/usr/include/c++/7/type_traits:1469:37: note: suggested alternative:
In file included from /usr/include/wchar.h:35:0,
                 from /usr/include/c++/7/cwchar:44,
                 from /usr/include/c++/7/bits/postypes.h:40,
                 from /usr/include/c++/7/iosfwd:40,
                 from /usr/include/c++/7/ios:38,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/lib/gcc/x86_64-linux-gnu/7/include/stddef.h:216:23: note:   'size_t'
 typedef __SIZE_TYPE__ size_t;
                       ^~~~~~
In file included from /usr/include/c++/7/bits/move.h:54:0,
                 from /usr/include/c++/7/bits/nested_exception.h:40,
                 from /usr/include/c++/7/exception:143,
                 from /usr/include/c++/7/ios:39,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/type_traits:1469:37: error: 'size_t' is not a member of 'std'
     : public integral_constant<std::size_t, 0> { };
                                     ^~~~~~
/usr/include/c++/7/type_traits:1469:37: note: suggested alternative:
In file included from /usr/include/wchar.h:35:0,
                 from /usr/include/c++/7/cwchar:44,
                 from /usr/include/c++/7/bits/postypes.h:40,
                 from /usr/include/c++/7/iosfwd:40,
                 from /usr/include/c++/7/ios:38,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/lib/gcc/x86_64-linux-gnu/7/include/stddef.h:216:23: note:   'size_t'
 typedef __SIZE_TYPE__ size_t;
                       ^~~~~~
In file included from /usr/include/c++/7/bits/move.h:54:0,
                 from /usr/include/c++/7/bits/nested_exception.h:40,
                 from /usr/include/c++/7/exception:143,
                 from /usr/include/c++/7/ios:39,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/type_traits:1469:46: error: template argument 1 is invalid
     : public integral_constant<std::size_t, 0> { };
                                              ^
/usr/include/c++/7/type_traits:1469:46: note: invalid template non-type parameter
/usr/include/c++/7/type_traits:1471:31: error: 'std::size_t' has not been declared
   template<typename _Tp, std::size_t _Size>
                               ^~~~~~
/usr/include/c++/7/type_traits:1472:21: error: '_Size' was not declared in this scope
     struct rank<_Tp[_Size]>
                     ^~~~~
/usr/include/c++/7/type_traits:1472:27: error: template argument 1 is invalid
     struct rank<_Tp[_Size]>
                           ^
/usr/include/c++/7/type_traits:1473:37: error: 'size_t' is not a member of 'std'
     : public integral_constant<std::size_t, 1 + rank<_Tp>::value> { };
                                     ^~~~~~
/usr/include/c++/7/type_traits:1473:37: note: suggested alternative:
In file included from /usr/include/wchar.h:35:0,
                 from /usr/include/c++/7/cwchar:44,
                 from /usr/include/c++/7/bits/postypes.h:40,
                 from /usr/include/c++/7/iosfwd:40,
                 from /usr/include/c++/7/ios:38,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/lib/gcc/x86_64-linux-gnu/7/include/stddef.h:216:23: note:   'size_t'
 typedef __SIZE_TYPE__ size_t;
                       ^~~~~~
In file included from /usr/include/c++/7/bits/move.h:54:0,
                 from /usr/include/c++/7/bits/nested_exception.h:40,
                 from /usr/include/c++/7/exception:143,
                 from /usr/include/c++/7/ios:39,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/type_traits:1473:37: error: 'size_t' is not a member of 'std'
     : public integral_constant<std::size_t, 1 + rank<_Tp>::value> { };
                                     ^~~~~~
/usr/include/c++/7/type_traits:1473:37: note: suggested alternative:
In file included from /usr/include/wchar.h:35:0,
                 from /usr/include/c++/7/cwchar:44,
                 from /usr/include/c++/7/bits/postypes.h:40,
                 from /usr/include/c++/7/iosfwd:40,
                 from /usr/include/c++/7/ios:38,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/lib/gcc/x86_64-linux-gnu/7/include/stddef.h:216:23: note:   'size_t'
 typedef __SIZE_TYPE__ size_t;
                       ^~~~~~
In file included from /usr/include/c++/7/bits/move.h:54:0,
                 from /usr/include/c++/7/bits/nested_exception.h:40,
                 from /usr/include/c++/7/exception:143,
                 from /usr/include/c++/7/ios:39,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/type_traits:1473:65: error: template argument 1 is invalid
     : public integral_constant<std::size_t, 1 + rank<_Tp>::value> { };
                                                                 ^
/usr/include/c++/7/type_traits:1473:65: note: invalid template non-type parameter
/usr/include/c++/7/type_traits:1477:37: error: 'size_t' is not a member of 'std'
     : public integral_constant<std::size_t, 1 + rank<_Tp>::value> { };
                                     ^~~~~~
/usr/include/c++/7/type_traits:1477:37: note: suggested alternative:
In file included from /usr/include/wchar.h:35:0,
                 from /usr/include/c++/7/cwchar:44,
                 from /usr/include/c++/7/bits/postypes.h:40,
                 from /usr/include/c++/7/iosfwd:40,
                 from /usr/include/c++/7/ios:38,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/lib/gcc/x86_64-linux-gnu/7/include/stddef.h:216:23: note:   'size_t'
 typedef __SIZE_TYPE__ size_t;
                       ^~~~~~
In file included from /usr/include/c++/7/bits/move.h:54:0,
                 from /usr/include/c++/7/bits/nested_exception.h:40,
                 from /usr/include/c++/7/exception:143,
                 from /usr/include/c++/7/ios:39,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/type_traits:1477:37: error: 'size_t' is not a member of 'std'
     : public integral_constant<std::size_t, 1 + rank<_Tp>::value> { };
                                     ^~~~~~
/usr/include/c++/7/type_traits:1477:37: note: suggested alternative:
In file included from /usr/include/wchar.h:35:0,
                 from /usr/include/c++/7/cwchar:44,
                 from /usr/include/c++/7/bits/postypes.h:40,
                 from /usr/include/c++/7/iosfwd:40,
                 from /usr/include/c++/7/ios:38,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/lib/gcc/x86_64-linux-gnu/7/include/stddef.h:216:23: note:   'size_t'
 typedef __SIZE_TYPE__ size_t;
                       ^~~~~~
In file included from /usr/include/c++/7/bits/move.h:54:0,
                 from /usr/include/c++/7/bits/nested_exception.h:40,
                 from /usr/include/c++/7/exception:143,
                 from /usr/include/c++/7/ios:39,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/type_traits:1477:65: error: template argument 1 is invalid
     : public integral_constant<std::size_t, 1 + rank<_Tp>::value> { };
                                                                 ^
/usr/include/c++/7/type_traits:1477:65: note: invalid template non-type parameter
/usr/include/c++/7/type_traits:1482:37: error: 'size_t' is not a member of 'std'
     : public integral_constant<std::size_t, 0> { };
                                     ^~~~~~
/usr/include/c++/7/type_traits:1482:37: note: suggested alternative:
In file included from /usr/include/wchar.h:35:0,
                 from /usr/include/c++/7/cwchar:44,
                 from /usr/include/c++/7/bits/postypes.h:40,
                 from /usr/include/c++/7/iosfwd:40,
                 from /usr/include/c++/7/ios:38,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/lib/gcc/x86_64-linux-gnu/7/include/stddef.h:216:23: note:   'size_t'
 typedef __SIZE_TYPE__ size_t;
                       ^~~~~~
In file included from /usr/include/c++/7/bits/move.h:54:0,
                 from /usr/include/c++/7/bits/nested_exception.h:40,
                 from /usr/include/c++/7/exception:143,
                 from /usr/include/c++/7/ios:39,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/type_traits:1482:37: error: 'size_t' is not a member of 'std'
     : public integral_constant<std::size_t, 0> { };
                                     ^~~~~~
/usr/include/c++/7/type_traits:1482:37: note: suggested alternative:
In file included from /usr/include/wchar.h:35:0,
                 from /usr/include/c++/7/cwchar:44,
                 from /usr/include/c++/7/bits/postypes.h:40,
                 from /usr/include/c++/7/iosfwd:40,
                 from /usr/include/c++/7/ios:38,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/lib/gcc/x86_64-linux-gnu/7/include/stddef.h:216:23: note:   'size_t'
 typedef __SIZE_TYPE__ size_t;
                       ^~~~~~
In file included from /usr/include/c++/7/bits/move.h:54:0,
                 from /usr/include/c++/7/bits/nested_exception.h:40,
                 from /usr/include/c++/7/exception:143,
                 from /usr/include/c++/7/ios:39,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/type_traits:1482:46: error: template argument 1 is invalid
     : public integral_constant<std::size_t, 0> { };
                                              ^
/usr/include/c++/7/type_traits:1482:46: note: invalid template non-type parameter
/usr/include/c++/7/type_traits:1484:47: error: 'std::size_t' has not been declared
   template<typename _Tp, unsigned _Uint, std::size_t _Size>
                                               ^~~~~~
/usr/include/c++/7/type_traits:1485:23: error: '_Size' was not declared in this scope
     struct extent<_Tp[_Size], _Uint>
                       ^~~~~
/usr/include/c++/7/type_traits:1485:36: error: template argument 1 is invalid
     struct extent<_Tp[_Size], _Uint>
                                    ^
/usr/include/c++/7/type_traits:1486:37: error: 'size_t' is not a member of 'std'
     : public integral_constant<std::size_t,
                                     ^~~~~~
/usr/include/c++/7/type_traits:1486:37: note: suggested alternative:
In file included from /usr/include/wchar.h:35:0,
                 from /usr/include/c++/7/cwchar:44,
                 from /usr/include/c++/7/bits/postypes.h:40,
                 from /usr/include/c++/7/iosfwd:40,
                 from /usr/include/c++/7/ios:38,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/lib/gcc/x86_64-linux-gnu/7/include/stddef.h:216:23: note:   'size_t'
 typedef __SIZE_TYPE__ size_t;
                       ^~~~~~
In file included from /usr/include/c++/7/bits/move.h:54:0,
                 from /usr/include/c++/7/bits/nested_exception.h:40,
                 from /usr/include/c++/7/exception:143,
                 from /usr/include/c++/7/ios:39,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/type_traits:1486:37: error: 'size_t' is not a member of 'std'
     : public integral_constant<std::size_t,
                                     ^~~~~~
/usr/include/c++/7/type_traits:1486:37: note: suggested alternative:
In file included from /usr/include/wchar.h:35:0,
                 from /usr/include/c++/7/cwchar:44,
                 from /usr/include/c++/7/bits/postypes.h:40,
                 from /usr/include/c++/7/iosfwd:40,
                 from /usr/include/c++/7/ios:38,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/lib/gcc/x86_64-linux-gnu/7/include/stddef.h:216:23: note:   'size_t'
 typedef __SIZE_TYPE__ size_t;
                       ^~~~~~
In file included from /usr/include/c++/7/bits/move.h:54:0,
                 from /usr/include/c++/7/bits/nested_exception.h:40,
                 from /usr/include/c++/7/exception:143,
                 from /usr/include/c++/7/ios:39,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/type_traits:1487:24: error: '_Size' was not declared in this scope
           _Uint == 0 ? _Size : extent<_Tp,
                        ^~~~~
/usr/include/c++/7/type_traits:1488:28: error: template argument 1 is invalid
           _Uint - 1>::value>
                            ^
/usr/include/c++/7/type_traits:1488:28: note: invalid template non-type parameter
/usr/include/c++/7/type_traits:1493:37: error: 'size_t' is not a member of 'std'
     : public integral_constant<std::size_t,
                                     ^~~~~~
/usr/include/c++/7/type_traits:1493:37: note: suggested alternative:
In file included from /usr/include/wchar.h:35:0,
                 from /usr/include/c++/7/cwchar:44,
                 from /usr/include/c++/7/bits/postypes.h:40,
                 from /usr/include/c++/7/iosfwd:40,
                 from /usr/include/c++/7/ios:38,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/lib/gcc/x86_64-linux-gnu/7/include/stddef.h:216:23: note:   'size_t'
 typedef __SIZE_TYPE__ size_t;
                       ^~~~~~
In file included from /usr/include/c++/7/bits/move.h:54:0,
                 from /usr/include/c++/7/bits/nested_exception.h:40,
                 from /usr/include/c++/7/exception:143,
                 from /usr/include/c++/7/ios:39,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/type_traits:1493:37: error: 'size_t' is not a member of 'std'
     : public integral_constant<std::size_t,
                                     ^~~~~~
/usr/include/c++/7/type_traits:1493:37: note: suggested alternative:
In file included from /usr/include/wchar.h:35:0,
                 from /usr/include/c++/7/cwchar:44,
                 from /usr/include/c++/7/bits/postypes.h:40,
                 from /usr/include/c++/7/iosfwd:40,
                 from /usr/include/c++/7/ios:38,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/lib/gcc/x86_64-linux-gnu/7/include/stddef.h:216:23: note:   'size_t'
 typedef __SIZE_TYPE__ size_t;
                       ^~~~~~
In file included from /usr/include/c++/7/bits/move.h:54:0,
                 from /usr/include/c++/7/bits/nested_exception.h:40,
                 from /usr/include/c++/7/exception:143,
                 from /usr/include/c++/7/ios:39,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/type_traits:1495:31: error: template argument 1 is invalid
              _Uint - 1>::value>
                               ^
/usr/include/c++/7/type_traits:1495:31: note: invalid template non-type parameter
/usr/include/c++/7/type_traits:1944:31: error: 'std::size_t' has not been declared
   template<typename _Tp, std::size_t _Size>
                               ^~~~~~
/usr/include/c++/7/type_traits:1945:30: error: '_Size' was not declared in this scope
     struct remove_extent<_Tp[_Size]>
                              ^~~~~
/usr/include/c++/7/type_traits:1945:36: error: template argument 1 is invalid
     struct remove_extent<_Tp[_Size]>
                                    ^
/usr/include/c++/7/type_traits:1957:31: error: 'std::size_t' has not been declared
   template<typename _Tp, std::size_t _Size>
                               ^~~~~~
/usr/include/c++/7/type_traits:1958:35: error: '_Size' was not declared in this scope
     struct remove_all_extents<_Tp[_Size]>
                                   ^~~~~
/usr/include/c++/7/type_traits:1958:41: error: template argument 1 is invalid
     struct remove_all_extents<_Tp[_Size]>
                                         ^
/usr/include/c++/7/type_traits:2016:17: error: 'std::size_t' has not been declared
   template<std::size_t _Len>
                 ^~~~~~
/usr/include/c++/7/type_traits:2021:23: error: '_Len' was not declared in this scope
  unsigned char __data[_Len];
                       ^~~~
/usr/include/c++/7/type_traits:2036:17: error: 'std::size_t' has not been declared
   template<std::size_t _Len, std::size_t _Align =
                 ^~~~~~
/usr/include/c++/7/type_traits:2036:35: error: 'std::size_t' has not been declared
   template<std::size_t _Len, std::size_t _Align =
                                   ^~~~~~
/usr/include/c++/7/type_traits:2037:48: error: '_Len' was not declared in this scope
     __alignof__(typename __aligned_storage_msa<_Len>::__type)>
                                                ^~~~
/usr/include/c++/7/type_traits:2037:52: error: template argument 1 is invalid
     __alignof__(typename __aligned_storage_msa<_Len>::__type)>
                                                    ^
/usr/include/c++/7/type_traits:2042:23: error: '_Len' was not declared in this scope
  unsigned char __data[_Len];
                       ^~~~
/usr/include/c++/7/type_traits:2043:37: error: '_Align' was not declared in this scope
  struct __attribute__((__aligned__((_Align)))) { } __align;
                                     ^~~~~~
In file included from /usr/include/c++/7/bits/stl_algobase.h:62:0,
                 from /usr/include/c++/7/bits/char_traits.h:39,
                 from /usr/include/c++/7/ios:40,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/ext/type_traits.h:162:35: error: 'bool __gnu_cxx::__is_null_pointer' redeclared as different kind of symbol
   __is_null_pointer(std::nullptr_t)
                                   ^
/usr/include/c++/7/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++/7/ext/type_traits.h:162:26: error: 'nullptr_t' is not a member of 'std'
   __is_null_pointer(std::nullptr_t)
                          ^~~~~~~~~
/usr/include/c++/7/ext/type_traits.h:162:26: note: suggested alternative: '__is_nullptr_t'
   __is_null_pointer(std::nullptr_t)
                          ^~~~~~~~~
                          __is_nullptr_t
In file included from /usr/include/c++/7/bits/stl_algobase.h:64:0,
                 from /usr/include/c++/7/bits/char_traits.h:39,
                 from /usr/include/c++/7/ios:40,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/stl_pair.h:86:17: error: 'std::size_t' has not been declared
   template<std::size_t...>
                 ^~~~~~
/usr/include/c++/7/bits/stl_pair.h:434:41: error: 'std::size_t' has not been declared
       template<typename... _Args1, std::size_t... _Indexes1,
                                         ^~~~~~
/usr/include/c++/7/bits/stl_pair.h:435:41: error: 'std::size_t' has not been declared
                typename... _Args2, std::size_t... _Indexes2>
                                         ^~~~~~
/usr/include/c++/7/bits/stl_pair.h:437:27: error: '_Indexes1' was not declared in this scope
              _Index_tuple<_Indexes1...>, _Index_tuple<_Indexes2...>);
                           ^~~~~~~~~
/usr/include/c++/7/bits/stl_pair.h:437:27: note: suggested alternative: '_Index_tuple'
              _Index_tuple<_Indexes1...>, _Index_tuple<_Indexes2...>);
                           ^~~~~~~~~
                           _Index_tuple
/usr/include/c++/7/bits/stl_pair.h:437:36: error: expected parameter pack before '...'
              _Index_tuple<_Indexes1...>, _Index_tuple<_Indexes2...>);
                                    ^~~
/usr/include/c++/7/bits/stl_pair.h:437:39: error: template argument 1 is invalid
              _Index_tuple<_Indexes1...>, _Index_tuple<_Indexes2...>);
                                       ^
/usr/include/c++/7/bits/stl_pair.h:437:55: error: '_Indexes2' was not declared in this scope
              _Index_tuple<_Indexes1...>, _Index_tuple<_Indexes2...>);
                                                       ^~~~~~~~~
/usr/include/c++/7/bits/stl_pair.h:437:55: note: suggested alternative: '_Index_tuple'
              _Index_tuple<_Indexes1...>, _Index_tuple<_Indexes2...>);
                                                       ^~~~~~~~~
                                                       _Index_tuple
/usr/include/c++/7/bits/stl_pair.h:437:64: error: expected parameter pack before '...'
              _Index_tuple<_Indexes1...>, _Index_tuple<_Indexes2...>);
                                                                ^~~
/usr/include/c++/7/bits/stl_pair.h:437:67: error: template argument 1 is invalid
              _Index_tuple<_Indexes1...>, _Index_tuple<_Indexes2...>);
                                                                   ^
In file included from /usr/include/c++/7/ios:40:0,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/char_traits.h:108:66: error: 'std::size_t' has not been declared
       compare(const char_type* __s1, const char_type* __s2, std::size_t __n);
                                                                  ^~~~~~
/usr/include/c++/7/bits/char_traits.h:110:40: error: 'size_t' in namespace 'std' does not name a type
       static _GLIBCXX14_CONSTEXPR std::size_t
                                        ^~~~~~
/usr/include/c++/7/bits/char_traits.h:114:39: error: 'std::size_t' has not been declared
       find(const char_type* __s, std::size_t __n, const char_type& __a);
                                       ^~~~~~
/usr/include/c++/7/bits/char_traits.h:117:57: error: 'std::size_t' has not been declared
       move(char_type* __s1, const char_type* __s2, std::size_t __n);
                                                         ^~~~~~
/usr/include/c++/7/bits/char_traits.h:120:57: error: 'std::size_t' has not been declared
       copy(char_type* __s1, const char_type* __s2, std::size_t __n);
                                                         ^~~~~~
/usr/include/c++/7/bits/char_traits.h:123:35: error: 'std::size_t' has not been declared
       assign(char_type* __s, std::size_t __n, char_type __a);
                                   ^~~~~~
/usr/include/c++/7/bits/char_traits.h:149:64: error: 'std::size_t' has not been declared
     compare(const char_type* __s1, const char_type* __s2, std::size_t __n)
                                                                ^~~~~~
/usr/include/c++/7/bits/char_traits.h: In static member function 'static int __gnu_cxx::char_traits<_CharT>::compare(const char_type*, const char_type*, int)':
/usr/include/c++/7/bits/char_traits.h:151:17: error: 'size_t' is not a member of 'std'
       for (std::size_t __i = 0; __i < __n; ++__i)
                 ^~~~~~
/usr/include/c++/7/bits/char_traits.h:151:17: note: suggested alternative:
In file included from /usr/include/wchar.h:35:0,
                 from /usr/include/c++/7/cwchar:44,
                 from /usr/include/c++/7/bits/postypes.h:40,
                 from /usr/include/c++/7/iosfwd:40,
                 from /usr/include/c++/7/ios:38,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/lib/gcc/x86_64-linux-gnu/7/include/stddef.h:216:23: note:   'size_t'
 typedef __SIZE_TYPE__ size_t;
                       ^~~~~~
In file included from /usr/include/c++/7/ios:40:0,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/char_traits.h:151:33: error: '__i' was not declared in this scope
       for (std::size_t __i = 0; __i < __n; ++__i)
                                 ^~~
/usr/include/c++/7/bits/char_traits.h:151:33: note: suggested alternative: '__n'
       for (std::size_t __i = 0; __i < __n; ++__i)
                                 ^~~
                                 __n
/usr/include/c++/7/bits/char_traits.h: At global scope:
/usr/include/c++/7/bits/char_traits.h:160:31: error: 'size_t' in namespace 'std' does not name a type
     _GLIBCXX14_CONSTEXPR std::size_t
                               ^~~~~~
/usr/include/c++/7/bits/char_traits.h:173:37: error: 'std::size_t' has not been declared
     find(const char_type* __s, std::size_t __n, const char_type& __a)
                                     ^~~~~~
/usr/include/c++/7/bits/char_traits.h: In static member function 'static const char_type* __gnu_cxx::char_traits<_CharT>::find(const char_type*, int, const char_type&)':
/usr/include/c++/7/bits/char_traits.h:175:17: error: 'size_t' is not a member of 'std'
       for (std::size_t __i = 0; __i < __n; ++__i)
                 ^~~~~~
/usr/include/c++/7/bits/char_traits.h:175:17: note: suggested alternative:
In file included from /usr/include/wchar.h:35:0,
                 from /usr/include/c++/7/cwchar:44,
                 from /usr/include/c++/7/bits/postypes.h:40,
                 from /usr/include/c++/7/iosfwd:40,
                 from /usr/include/c++/7/ios:38,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/lib/gcc/x86_64-linux-gnu/7/include/stddef.h:216:23: note:   'size_t'
 typedef __SIZE_TYPE__ size_t;
                       ^~~~~~
In file included from /usr/include/c++/7/ios:40:0,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/char_traits.h:175:33: error: '__i' was not declared in this scope
       for (std::size_t __i = 0; __i < __n; ++__i)
                                 ^~~
/usr/include/c++/7/bits/char_traits.h:175:33: note: suggested alternative: '__s'
       for (std::size_t __i = 0; __i < __n; ++__i)
                                 ^~~
                                 __s
/usr/include/c++/7/bits/char_traits.h: At global scope:
/usr/include/c++/7/bits/char_traits.h:184:55: error: 'std::size_t' has not been declared
     move(char_type* __s1, const char_type* __s2, std::size_t __n)
                                                       ^~~~~~
/usr/include/c++/7/bits/char_traits.h:193:55: error: 'std::size_t' has not been declared
     copy(char_type* __s1, const char_type* __s2, std::size_t __n)
                                                       ^~~~~~
/usr/include/c++/7/bits/char_traits.h:203:33: error: 'std::size_t' has not been declared
     assign(char_type* __s, std::size_t __n, char_type __a)
                                 ^~~~~~
In file included from /usr/include/x86_64-linux-gnu/c++/7/bits/c++allocator.h:33:0,
                 from /usr/include/c++/7/bits/allocator.h:46,
                 from /usr/include/c++/7/string:41,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/ext/new_allocator.h:44:14: error: 'std::size_t' has not been declared
   using std::size_t;
              ^~~~~~
/usr/include/c++/7/ext/new_allocator.h:45:14: error: 'std::ptrdiff_t' has not been declared
   using std::ptrdiff_t;
              ^~~~~~~~~
In file included from /usr/include/c++/7/string:44:0,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/ostream_insert.h:45:26: error: 'streamsize' has not been declared
       const _CharT* __s, streamsize __n)
                          ^~~~~~~~~~
/usr/include/c++/7/bits/ostream_insert.h: In function 'void std::__ostream_write(std::basic_ostream<_CharT, _Traits>&, const _CharT*, int)':
/usr/include/c++/7/bits/ostream_insert.h:50:13: error: 'streamsize' does not name a type; did you mean 'streambuf'?
       const streamsize __put = __out.rdbuf()->sputn(__s, __n);
             ^~~~~~~~~~
             streambuf
/usr/include/c++/7/bits/ostream_insert.h:51:11: error: '__put' was not declared in this scope
       if (__put != __n)
           ^~~~~
/usr/include/c++/7/bits/ostream_insert.h:51:11: note: suggested alternative: '__out'
       if (__put != __n)
           ^~~~~
           __out
/usr/include/c++/7/bits/ostream_insert.h: At global scope:
/usr/include/c++/7/bits/ostream_insert.h:57:59: error: 'streamsize' has not been declared
     __ostream_fill(basic_ostream<_CharT, _Traits>& __out, streamsize __n)
                                                           ^~~~~~~~~~
/usr/include/c++/7/bits/ostream_insert.h:77:27: error: 'streamsize' has not been declared
        const _CharT* __s, streamsize __n)
                           ^~~~~~~~~~
/usr/include/c++/7/bits/ostream_insert.h: In function 'std::basic_ostream<_CharT, _Traits>& std::__ostream_insert(std::basic_ostream<_CharT, _Traits>&, const _CharT*, int)':
/usr/include/c++/7/bits/ostream_insert.h:87:14: error: 'streamsize' does not name a type; did you mean 'streambuf'?
        const streamsize __w = __out.width();
              ^~~~~~~~~~
              streambuf
/usr/include/c++/7/bits/ostream_insert.h:88:12: error: '__w' was not declared in this scope
        if (__w > __n)
            ^~~
/usr/include/c++/7/bits/ostream_insert.h:88:12: note: suggested alternative: '__s'
        if (__w > __n)
            ^~~
            __s
/usr/include/c++/7/bits/ostream_insert.h: At global scope:
/usr/include/c++/7/bits/ostream_insert.h:118:68: error: 'streamsize' has not been declared
   extern template ostream& __ostream_insert(ostream&, const char*, streamsize);
                                                                    ^~~~~~~~~~
/usr/include/c++/7/bits/ostream_insert.h:122:11: error: 'streamsize' has not been declared
           streamsize);
           ^~~~~~~~~~
In file included from /usr/include/c++/7/ext/alloc_traits.h:36:0,
                 from /usr/include/c++/7/bits/basic_string.h:40,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/alloc_traits.h:404:36: error: 'ptrdiff_t' in namespace 'std' does not name a type
       using difference_type = std::ptrdiff_t;
                                    ^~~~~~~~~
/usr/include/c++/7/bits/alloc_traits.h:407:30: error: 'size_t' in namespace 'std' does not name a type
       using size_type = std::size_t;
                              ^~~~~~
/usr/include/c++/7/bits/alloc_traits.h:435:37: error: 'size_type' has not been declared
       allocate(allocator_type& __a, size_type __n)
                                     ^~~~~~~~~
/usr/include/c++/7/bits/alloc_traits.h:449:37: error: 'size_type' has not been declared
       allocate(allocator_type& __a, size_type __n, const_void_pointer __hint)
                                     ^~~~~~~~~
/usr/include/c++/7/bits/alloc_traits.h:461:52: error: 'size_type' has not been declared
       deallocate(allocator_type& __a, pointer __p, size_type __n)
                                                    ^~~~~~~~~
/usr/include/c++/7/bits/alloc_traits.h:494:14: error: 'size_type' does not name a type; did you mean 'true_type'?
       static size_type
              ^~~~~~~~~
              true_type
In file included from /usr/include/c++/7/bits/basic_string.h:6361:0,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/ext/string_conversions.h:55:51: error: 'std::size_t' has not been declared
     const char* __name, const _CharT* __str, std::size_t* __idx,
                                                   ^~~~~~
/usr/include/c++/7/ext/string_conversions.h:99:48: error: 'std::size_t' has not been declared
     __to_xstring(int (*__convf) (_CharT*, std::size_t, const _CharT*,
                                                ^~~~~~
/usr/include/c++/7/ext/string_conversions.h:100:31: error: 'std::size_t' has not been declared
      __builtin_va_list), std::size_t __n,
                               ^~~~~~
In file included from /usr/include/c++/7/bits/basic_string.h:40:0,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/ext/alloc_traits.h: In instantiation of 'struct __gnu_cxx::__alloc_traits<std::allocator<char> >':
/usr/include/c++/7/bits/basic_string.h:80:24:   required from 'class std::__cxx11::basic_string<char>'
/usr/include/c++/7/bits/basic_string.h:6372:68:   required from here
/usr/include/c++/7/ext/alloc_traits.h:61:53: error: no type named 'size_type' in 'struct std::allocator_traits<std::allocator<char> >'
     typedef typename _Base_type::size_type          size_type;
                                                     ^~~~~~~~~
/usr/include/c++/7/ext/alloc_traits.h:62:53: error: no type named 'difference_type' in 'struct std::allocator_traits<std::allocator<char> >'
     typedef typename _Base_type::difference_type    difference_type;
                                                     ^~~~~~~~~~~~~~~
/usr/include/c++/7/ext/alloc_traits.h:70:23: error: no members matching '__gnu_cxx::__alloc_traits<std::allocator<char> >::_Base_type {aka std::allocator_traits<std::allocator<char> >}::max_size' in '__gnu_cxx::__alloc_traits<std::allocator<char> >::_Base_type {aka struct std::allocator_traits<std::allocator<char> >}'
     using _Base_type::max_size;
                       ^~~~~~~~
In file included from /usr/include/c++/7/string:52:0,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/basic_string.h: In function 'int std::__cxx11::stoi(const string&, size_t*, int)':
/usr/include/c++/7/bits/basic_string.h:6373:19: error: no matching function for call to '__stoa<long int, int>(long int (*)(const char*, char**, int) throw (), const char [5], const char*, size_t*&, int&)'
      __idx, __base); }
                   ^
In file included from /usr/include/c++/7/bits/basic_string.h:6361:0,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/ext/string_conversions.h:54:5: note: candidate: template<class _TRet, class _Ret, class _CharT, class ... _Base> _Ret __gnu_cxx::__stoa(_TRet (*)(const _CharT*, _CharT**, _Base ...), const char*, const _CharT*, int*, _Base ...)
     __stoa(_TRet (*__convf) (const _CharT*, _CharT**, _Base...),
     ^~~~~~
/usr/include/c++/7/ext/string_conversions.h:54:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/7/string:52:0,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/basic_string.h:6373:19: note:   cannot convert '__idx' (type 'size_t* {aka long unsigned int*}') to type 'int*'
      __idx, __base); }
                   ^
/usr/include/c++/7/bits/basic_string.h: In function 'long int std::__cxx11::stol(const string&, size_t*, int)':
/usr/include/c++/7/bits/basic_string.h:6378:22: error: no matching function for call to '__stoa(long int (*)(const char*, char**, int) throw (), const char [5], const char*, size_t*&, int&)'
         __idx, __base); }
                      ^
In file included from /usr/include/c++/7/bits/basic_string.h:6361:0,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/ext/string_conversions.h:54:5: note: candidate: template<class _TRet, class _Ret, class _CharT, class ... _Base> _Ret __gnu_cxx::__stoa(_TRet (*)(const _CharT*, _CharT**, _Base ...), const char*, const _CharT*, int*, _Base ...)
     __stoa(_TRet (*__convf) (const _CharT*, _CharT**, _Base...),
     ^~~~~~
/usr/include/c++/7/ext/string_conversions.h:54:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/7/string:52:0,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/basic_string.h:6378:22: note:   cannot convert '__idx' (type 'size_t* {aka long unsigned int*}') to type 'int*'
         __idx, __base); }
                      ^
/usr/include/c++/7/bits/basic_string.h: In function 'long unsigned int std::__cxx11::stoul(const string&, size_t*, int)':
/usr/include/c++/7/bits/basic_string.h:6383:22: error: no matching function for call to '__stoa(long unsigned int (*)(const char*, char**, int) throw (), const char [6], const char*, size_t*&, int&)'
         __idx, __base); }
                      ^
In file included from /usr/include/c++/7/bits/basic_string.h:6361:0,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/ext/string_conversions.h:54:5: note: candidate: template<class _TRet, class _Ret, class _CharT, class ... _Base> _Ret __gnu_cxx::__stoa(_TRet (*)(const _CharT*, _CharT**, _Base ...), const char*, const _CharT*, int*, _Base ...)
     __stoa(_TRet (*__convf) (const _CharT*, _CharT**, _Base...),
     ^~~~~~
/usr/include/c++/7/ext/string_conversions.h:54:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/7/string:52:0,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/basic_string.h:6383:22: note:   cannot convert '__idx' (type 'size_t* {aka long unsigned int*}') to type 'int*'
         __idx, __base); }
                      ^
/usr/include/c++/7/bits/basic_string.h: In function 'long long int std::__cxx11::stoll(const string&, size_t*, int)':
/usr/include/c++/7/bits/basic_string.h:6388:22: error: no matching function for call to '__stoa(long long int (*)(const char*, char**, int) throw (), const char [6], const char*, size_t*&, int&)'
         __idx, __base); }
                      ^
In file included from /usr/include/c++/7/bits/basic_string.h:6361:0,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/ext/string_conversions.h:54:5: note: candidate: template<class _TRet, class _Ret, class _CharT, class ... _Base> _Ret __gnu_cxx::__stoa(_TRet (*)(const _CharT*, _CharT**, _Base ...), const char*, const _CharT*, int*, _Base ...)
     __stoa(_TRet (*__convf) (const _CharT*, _CharT**, _Base...),
     ^~~~~~
/usr/include/c++/7/ext/string_conversions.h:54:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/7/string:52:0,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/basic_string.h:6388:22: note:   cannot convert '__idx' (type 'size_t* {aka long unsigned int*}') to type 'int*'
         __idx, __base); }
                      ^
/usr/include/c++/7/bits/basic_string.h: In function 'long long unsigned int std::__cxx11::stoull(const string&, size_t*, int)':
/usr/include/c++/7/bits/basic_string.h:6393:22: error: no matching function for call to '__stoa(long long unsigned int (*)(const char*, char**, int) throw (), const char [7], const char*, size_t*&, int&)'
         __idx, __base); }
                      ^
In file included from /usr/include/c++/7/bits/basic_string.h:6361:0,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/ext/string_conversions.h:54:5: note: candidate: template<class _TRet, class _Ret, class _CharT, class ... _Base> _Ret __gnu_cxx::__stoa(_TRet (*)(const _CharT*, _CharT**, _Base ...), const char*, const _CharT*, int*, _Base ...)
     __stoa(_TRet (*__convf) (const _CharT*, _CharT**, _Base...),
     ^~~~~~
/usr/include/c++/7/ext/string_conversions.h:54:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/7/string:52:0,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/basic_string.h:6393:22: note:   cannot convert '__idx' (type 'size_t* {aka long unsigned int*}') to type 'int*'
         __idx, __base); }
                      ^
/usr/include/c++/7/bits/basic_string.h: In function 'float std::__cxx11::stof(const string&, size_t*)':
/usr/include/c++/7/bits/basic_string.h:6398:72: error: no matching function for call to '__stoa(float (*)(const char*, char**) throw (), const char [5], const char*, size_t*&)'
   { return __gnu_cxx::__stoa(&std::strtof, "stof", __str.c_str(), __idx); }
                                                                        ^
In file included from /usr/include/c++/7/bits/basic_string.h:6361:0,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/ext/string_conversions.h:54:5: note: candidate: template<class _TRet, class _Ret, class _CharT, class ... _Base> _Ret __gnu_cxx::__stoa(_TRet (*)(const _CharT*, _CharT**, _Base ...), const char*, const _CharT*, int*, _Base ...)
     __stoa(_TRet (*__convf) (const _CharT*, _CharT**, _Base...),
     ^~~~~~
/usr/include/c++/7/ext/string_conversions.h:54:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/7/string:52:0,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/basic_string.h:6398:72: note:   cannot convert '__idx' (type 'size_t* {aka long unsigned int*}') to type 'int*'
   { return __gnu_cxx::__stoa(&std::strtof, "stof", __str.c_str(), __idx); }
                                                                        ^
/usr/include/c++/7/bits/basic_string.h: In function 'double std::__cxx11::stod(const string&, size_t*)':
/usr/include/c++/7/bits/basic_string.h:6402:72: error: no matching function for call to '__stoa(double (*)(const char*, char**) throw (), const char [5], const char*, size_t*&)'
   { return __gnu_cxx::__stoa(&std::strtod, "stod", __str.c_str(), __idx); }
                                                                        ^
In file included from /usr/include/c++/7/bits/basic_string.h:6361:0,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/ext/string_conversions.h:54:5: note: candidate: template<class _TRet, class _Ret, class _CharT, class ... _Base> _Ret __gnu_cxx::__stoa(_TRet (*)(const _CharT*, _CharT**, _Base ...), const char*, const _CharT*, int*, _Base ...)
     __stoa(_TRet (*__convf) (const _CharT*, _CharT**, _Base...),
     ^~~~~~
/usr/include/c++/7/ext/string_conversions.h:54:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/7/string:52:0,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/basic_string.h:6402:72: note:   cannot convert '__idx' (type 'size_t* {aka long unsigned int*}') to type 'int*'
   { return __gnu_cxx::__stoa(&std::strtod, "stod", __str.c_str(), __idx); }
                                                                        ^
/usr/include/c++/7/bits/basic_string.h: In function 'long double std::__cxx11::stold(const string&, size_t*)':
/usr/include/c++/7/bits/basic_string.h:6406:74: error: no matching function for call to '__stoa(long double (*)(const char*, char**) throw (), const char [6], const char*, size_t*&)'
   { return __gnu_cxx::__stoa(&std::strtold, "stold", __str.c_str(), __idx); }
                                                                          ^
In file included from /usr/include/c++/7/bits/basic_string.h:6361:0,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/ext/string_conversions.h:54:5: note: candidate: template<class _TRet, class _Ret, class _CharT, class ... _Base> _Ret __gnu_cxx::__stoa(_TRet (*)(const _CharT*, _CharT**, _Base ...), const char*, const _CharT*, int*, _Base ...)
     __stoa(_TRet (*__convf) (const _CharT*, _CharT**, _Base...),
     ^~~~~~
/usr/include/c++/7/ext/string_conversions.h:54:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/7/string:52:0,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/basic_string.h:6406:74: note:   cannot convert '__idx' (type 'size_t* {aka long unsigned int*}') to type 'int*'
   { return __gnu_cxx::__stoa(&std::strtold, "stold", __str.c_str(), __idx); }
                                                                          ^
/usr/include/c++/7/bits/basic_string.h: In function 'std::__cxx11::string std::__cxx11::to_string(int)':
/usr/include/c++/7/bits/basic_string.h:6416:20: error: no matching function for call to '__to_xstring<std::__cxx11::string>(int (*)(char*, size_t, const char*, __va_list_tag*) throw (), long unsigned int, const char [3], int&)'
         "%d", __val); }
                    ^
In file included from /usr/include/c++/7/bits/basic_string.h:6361:0,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/ext/string_conversions.h:99:5: note: candidate: template<class _String, class _CharT> _String __gnu_cxx::__to_xstring(int (*)(_CharT*, int, const _CharT*, __va_list_tag*), int, const _CharT*, ...)
     __to_xstring(int (*__convf) (_CharT*, std::size_t, const _CharT*,
     ^~~~~~~~~~~~
/usr/include/c++/7/ext/string_conversions.h:99:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/7/string:52:0,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/basic_string.h:6416:20: note:   mismatched types 'int' and 'size_t {aka long unsigned int}'
         "%d", __val); }
                    ^
/usr/include/c++/7/bits/basic_string.h: In function 'std::__cxx11::string std::__cxx11::to_string(unsigned int)':
/usr/include/c++/7/bits/basic_string.h:6422:20: error: no matching function for call to '__to_xstring<std::__cxx11::string>(int (*)(char*, size_t, const char*, __va_list_tag*) throw (), long unsigned int, const char [3], unsigned int&)'
         "%u", __val); }
                    ^
In file included from /usr/include/c++/7/bits/basic_string.h:6361:0,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/ext/string_conversions.h:99:5: note: candidate: template<class _String, class _CharT> _String __gnu_cxx::__to_xstring(int (*)(_CharT*, int, const _CharT*, __va_list_tag*), int, const _CharT*, ...)
     __to_xstring(int (*__convf) (_CharT*, std::size_t, const _CharT*,
     ^~~~~~~~~~~~
/usr/include/c++/7/ext/string_conversions.h:99:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/7/string:52:0,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/basic_string.h:6422:20: note:   mismatched types 'int' and 'size_t {aka long unsigned int}'
         "%u", __val); }
                    ^
/usr/include/c++/7/bits/basic_string.h: In function 'std::__cxx11::string std::__cxx11::to_string(long int)':
/usr/include/c++/7/bits/basic_string.h:6427:21: error: no matching function for call to '__to_xstring<std::__cxx11::string>(int (*)(char*, size_t, const char*, __va_list_tag*) throw (), long unsigned int, const char [4], long int&)'
         "%ld", __val); }
                     ^
In file included from /usr/include/c++/7/bits/basic_string.h:6361:0,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/ext/string_conversions.h:99:5: note: candidate: template<class _String, class _CharT> _String __gnu_cxx::__to_xstring(int (*)(_CharT*, int, const _CharT*, __va_list_tag*), int, const _CharT*, ...)
     __to_xstring(int (*__convf) (_CharT*, std::size_t, const _CharT*,
     ^~~~~~~~~~~~
/usr/include/c++/7/ext/string_conversions.h:99:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/7/string:52:0,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/basic_string.h:6427:21: note:   mismatched types 'int' and 'size_t {aka long unsigned int}'
         "%ld", __val); }
                     ^
/usr/include/c++/7/bits/basic_string.h: In function 'std::__cxx11::string std::__cxx11::to_string(long unsigned int)':
/usr/include/c++/7/bits/basic_string.h:6433:21: error: no matching function for call to '__to_xstring<std::__cxx11::string>(int (*)(char*, size_t, const char*, __va_list_tag*) throw (), long unsigned int, const char [4], long unsigned int&)'
         "%lu", __val); }
                     ^
In file included from /usr/include/c++/7/bits/basic_string.h:6361:0,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/ext/string_conversions.h:99:5: note: candidate: template<class _String, class _CharT> _String __gnu_cxx::__to_xstring(int (*)(_CharT*, int, const _CharT*, __va_list_tag*), int, const _CharT*, ...)
     __to_xstring(int (*__convf) (_CharT*, std::size_t, const _CharT*,
     ^~~~~~~~~~~~
/usr/include/c++/7/ext/string_conversions.h:99:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/7/string:52:0,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/basic_string.h:6433:21: note:   mismatched types 'int' and 'size_t {aka long unsigned int}'
         "%lu", __val); }
                     ^
/usr/include/c++/7/bits/basic_string.h: In function 'std::__cxx11::string std::__cxx11::to_string(long long int)':
/usr/include/c++/7/bits/basic_string.h:6439:22: error: no matching function for call to '__to_xstring<std::__cxx11::string>(int (*)(char*, size_t, const char*, __va_list_tag*) throw (), long unsigned int, const char [5], long long int&)'
         "%lld", __val); }
                      ^
In file included from /usr/include/c++/7/bits/basic_string.h:6361:0,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/ext/string_conversions.h:99:5: note: candidate: template<class _String, class _CharT> _String __gnu_cxx::__to_xstring(int (*)(_CharT*, int, const _CharT*, __va_list_tag*), int, const _CharT*, ...)
     __to_xstring(int (*__convf) (_CharT*, std::size_t, const _CharT*,
     ^~~~~~~~~~~~
/usr/include/c++/7/ext/string_conversions.h:99:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/7/string:52:0,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/basic_string.h:6439:22: note:   mismatched types 'int' and 'size_t {aka long unsigned int}'
         "%lld", __val); }
                      ^
/usr/include/c++/7/bits/basic_string.h: In function 'std::__cxx11::string std::__cxx11::to_string(long long unsigned int)':
/usr/include/c++/7/bits/basic_string.h:6445:22: error: no matching function for call to '__to_xstring<std::__cxx11::string>(int (*)(char*, size_t, const char*, __va_list_tag*) throw (), long unsigned int, const char [5], long long unsigned int&)'
         "%llu", __val); }
                      ^
In file included from /usr/include/c++/7/bits/basic_string.h:6361:0,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/ext/string_conversions.h:99:5: note: candidate: template<class _String, class _CharT> _String __gnu_cxx::__to_xstring(int (*)(_CharT*, int, const _CharT*, __va_list_tag*), int, const _CharT*, ...)
     __to_xstring(int (*__convf) (_CharT*, std::size_t, const _CharT*,
     ^~~~~~~~~~~~
/usr/include/c++/7/ext/string_conversions.h:99:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/7/string:52:0,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/basic_string.h:6445:22: note:   mismatched types 'int' and 'size_t {aka long unsigned int}'
         "%llu", __val); }
                      ^
/usr/include/c++/7/bits/basic_string.h: In function 'std::__cxx11::string std::__cxx11::to_string(float)':
/usr/include/c++/7/bits/basic_string.h:6453:20: error: no matching function for call to '__to_xstring<std::__cxx11::string>(int (*)(char*, size_t, const char*, __va_list_tag*) throw (), const int&, const char [3], float&)'
         "%f", __val);
                    ^
In file included from /usr/include/c++/7/bits/basic_string.h:6361:0,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/ext/string_conversions.h:99:5: note: candidate: template<class _String, class _CharT> _String __gnu_cxx::__to_xstring(int (*)(_CharT*, int, const _CharT*, __va_list_tag*), int, const _CharT*, ...)
     __to_xstring(int (*__convf) (_CharT*, std::size_t, const _CharT*,
     ^~~~~~~~~~~~
/usr/include/c++/7/ext/string_conversions.h:99:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/7/string:52:0,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/basic_string.h:6453:20: note:   mismatched types 'int' and 'size_t {aka long unsigned int}'
         "%f", __val);
                    ^
/usr/include/c++/7/bits/basic_string.h: In function 'std::__cxx11::string std::__cxx11::to_string(double)':
/usr/include/c++/7/bits/basic_string.h:6462:20: error: no matching function for call to '__to_xstring<std::__cxx11::string>(int (*)(char*, size_t, const char*, __va_list_tag*) throw (), const int&, const char [3], double&)'
         "%f", __val);
                    ^
In file included from /usr/include/c++/7/bits/basic_string.h:6361:0,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/ext/string_conversions.h:99:5: note: candidate: template<class _String, class _CharT> _String __gnu_cxx::__to_xstring(int (*)(_CharT*, int, const _CharT*, __va_list_tag*), int, const _CharT*, ...)
     __to_xstring(int (*__convf) (_CharT*, std::size_t, const _CharT*,
     ^~~~~~~~~~~~
/usr/include/c++/7/ext/string_conversions.h:99:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/7/string:52:0,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/basic_string.h:6462:20: note:   mismatched types 'int' and 'size_t {aka long unsigned int}'
         "%f", __val);
                    ^
/usr/include/c++/7/bits/basic_string.h: In function 'std::__cxx11::string std::__cxx11::to_string(long double)':
/usr/include/c++/7/bits/basic_string.h:6471:21: error: no matching function for call to '__to_xstring<std::__cxx11::string>(int (*)(char*, size_t, const char*, __va_list_tag*) throw (), const int&, const char [4], long double&)'
         "%Lf", __val);
                     ^
In file included from /usr/include/c++/7/bits/basic_string.h:6361:0,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/ext/string_conversions.h:99:5: note: candidate: template<class _String, class _CharT> _String __gnu_cxx::__to_xstring(int (*)(_CharT*, int, const _CharT*, __va_list_tag*), int, const _CharT*, ...)
     __to_xstring(int (*__convf) (_CharT*, std::size_t, const _CharT*,
     ^~~~~~~~~~~~
/usr/include/c++/7/ext/string_conversions.h:99:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/7/string:52:0,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/basic_string.h:6471:21: note:   mismatched types 'int' and 'size_t {aka long unsigned int}'
         "%Lf", __val);
                     ^
In file included from /usr/include/c++/7/bits/basic_string.h:40:0,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/ext/alloc_traits.h: In instantiation of 'struct __gnu_cxx::__alloc_traits<std::allocator<wchar_t> >':
/usr/include/c++/7/bits/basic_string.h:80:24:   required from 'class std::__cxx11::basic_string<wchar_t>'
/usr/include/c++/7/bits/basic_string.h:6478:68:   required from here
/usr/include/c++/7/ext/alloc_traits.h:61:53: error: no type named 'size_type' in 'struct std::allocator_traits<std::allocator<wchar_t> >'
     typedef typename _Base_type::size_type          size_type;
                                                     ^~~~~~~~~
/usr/include/c++/7/ext/alloc_traits.h:62:53: error: no type named 'difference_type' in 'struct std::allocator_traits<std::allocator<wchar_t> >'
     typedef typename _Base_type::difference_type    difference_type;
                                                     ^~~~~~~~~~~~~~~
/usr/include/c++/7/ext/alloc_traits.h:70:23: error: no members matching '__gnu_cxx::__alloc_traits<std::allocator<wchar_t> >::_Base_type {aka std::allocator_traits<std::allocator<wchar_t> >}::max_size' in '__gnu_cxx::__alloc_traits<std::allocator<wchar_t> >::_Base_type {aka struct std::allocator_traits<std::allocator<wchar_t> >}'
     using _Base_type::max_size;
                       ^~~~~~~~
In file included from /usr/include/c++/7/string:52:0,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/basic_string.h: In function 'int std::__cxx11::stoi(const wstring&, size_t*, int)':
/usr/include/c++/7/bits/basic_string.h:6479:19: error: no matching function for call to '__stoa<long int, int>(long int (*)(const wchar_t*, wchar_t**, int) throw (), const char [5], const wchar_t*, size_t*&, int&)'
      __idx, __base); }
                   ^
In file included from /usr/include/c++/7/bits/basic_string.h:6361:0,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/ext/string_conversions.h:54:5: note: candidate: template<class _TRet, class _Ret, class _CharT, class ... _Base> _Ret __gnu_cxx::__stoa(_TRet (*)(const _CharT*, _CharT**, _Base ...), const char*, const _CharT*, int*, _Base ...)
     __stoa(_TRet (*__convf) (const _CharT*, _CharT**, _Base...),
     ^~~~~~
/usr/include/c++/7/ext/string_conversions.h:54:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/7/string:52:0,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/basic_string.h:6479:19: note:   cannot convert '__idx' (type 'size_t* {aka long unsigned int*}') to type 'int*'
      __idx, __base); }
                   ^
/usr/include/c++/7/bits/basic_string.h: In function 'long int std::__cxx11::stol(const wstring&, size_t*, int)':
/usr/include/c++/7/bits/basic_string.h:6484:22: error: no matching function for call to '__stoa(long int (*)(const wchar_t*, wchar_t**, int) throw (), const char [5], const wchar_t*, size_t*&, int&)'
         __idx, __base); }
                      ^
In file included from /usr/include/c++/7/bits/basic_string.h:6361:0,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/ext/string_conversions.h:54:5: note: candidate: template<class _TRet, class _Ret, class _CharT, class ... _Base> _Ret __gnu_cxx::__stoa(_TRet (*)(const _CharT*, _CharT**, _Base ...), const char*, const _CharT*, int*, _Base ...)
     __stoa(_TRet (*__convf) (const _CharT*, _CharT**, _Base...),
     ^~~~~~
/usr/include/c++/7/ext/string_conversions.h:54:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/7/string:52:0,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/basic_string.h:6484:22: note:   cannot convert '__idx' (type 'size_t* {aka long unsigned int*}') to type 'int*'
         __idx, __base); }
                      ^
/usr/include/c++/7/bits/basic_string.h: In function 'long unsigned int std::__cxx11::stoul(const wstring&, size_t*, int)':
/usr/include/c++/7/bits/basic_string.h:6489:22: error: no matching function for call to '__stoa(long unsigned int (*)(const wchar_t*, wchar_t**, int) throw (), const char [6], const wchar_t*, size_t*&, int&)'
         __idx, __base); }
                      ^
In file included from /usr/include/c++/7/bits/basic_string.h:6361:0,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/ext/string_conversions.h:54:5: note: candidate: template<class _TRet, class _Ret, class _CharT, class ... _Base> _Ret __gnu_cxx::__stoa(_TRet (*)(const _CharT*, _CharT**, _Base ...), const char*, const _CharT*, int*, _Base ...)
     __stoa(_TRet (*__convf) (const _CharT*, _CharT**, _Base...),
     ^~~~~~
/usr/include/c++/7/ext/string_conversions.h:54:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/7/string:52:0,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/basic_string.h:6489:22: note:   cannot convert '__idx' (type 'size_t* {aka long unsigned int*}') to type 'int*'
         __idx, __base); }
                      ^
/usr/include/c++/7/bits/basic_string.h: In function 'long long int std::__cxx11::stoll(const wstring&, size_t*, int)':
/usr/include/c++/7/bits/basic_string.h:6494:22: error: no matching function for call to '__stoa(long long int (*)(const wchar_t*, wchar_t**, int) throw (), const char [6], const wchar_t*, size_t*&, int&)'
         __idx, __base); }
                      ^
In file included from /usr/include/c++/7/bits/basic_string.h:6361:0,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/ext/string_conversions.h:54:5: note: candidate: template<class _TRet, class _Ret, class _CharT, class ... _Base> _Ret __gnu_cxx::__stoa(_TRet (*)(const _CharT*, _CharT**, _Base ...), const char*, const _CharT*, int*, _Base ...)
     __stoa(_TRet (*__convf) (const _CharT*, _CharT**, _Base...),
     ^~~~~~
/usr/include/c++/7/ext/string_conversions.h:54:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/7/string:52:0,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/basic_string.h:6494:22: note:   cannot convert '__idx' (type 'size_t* {aka long unsigned int*}') to type 'int*'
         __idx, __base); }
                      ^
/usr/include/c++/7/bits/basic_string.h: In function 'long long unsigned int std::__cxx11::stoull(const wstring&, size_t*, int)':
/usr/include/c++/7/bits/basic_string.h:6499:22: error: no matching function for call to '__stoa(long long unsigned int (*)(const wchar_t*, wchar_t**, int) throw (), const char [7], const wchar_t*, size_t*&, int&)'
         __idx, __base); }
                      ^
In file included from /usr/include/c++/7/bits/basic_string.h:6361:0,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/ext/string_conversions.h:54:5: note: candidate: template<class _TRet, class _Ret, class _CharT, class ... _Base> _Ret __gnu_cxx::__stoa(_TRet (*)(const _CharT*, _CharT**, _Base ...), const char*, const _CharT*, int*, _Base ...)
     __stoa(_TRet (*__convf) (const _CharT*, _CharT**, _Base...),
     ^~~~~~
/usr/include/c++/7/ext/string_conversions.h:54:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/7/string:52:0,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/basic_string.h:6499:22: note:   cannot convert '__idx' (type 'size_t* {aka long unsigned int*}') to type 'int*'
         __idx, __base); }
                      ^
/usr/include/c++/7/bits/basic_string.h: In function 'float std::__cxx11::stof(const wstring&, size_t*)':
/usr/include/c++/7/bits/basic_string.h:6504:72: error: no matching function for call to '__stoa(float (*)(const wchar_t*, wchar_t**) throw (), const char [5], const wchar_t*, size_t*&)'
   { return __gnu_cxx::__stoa(&std::wcstof, "stof", __str.c_str(), __idx); }
                                                                        ^
In file included from /usr/include/c++/7/bits/basic_string.h:6361:0,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/ext/string_conversions.h:54:5: note: candidate: template<class _TRet, class _Ret, class _CharT, class ... _Base> _Ret __gnu_cxx::__stoa(_TRet (*)(const _CharT*, _CharT**, _Base ...), const char*, const _CharT*, int*, _Base ...)
     __stoa(_TRet (*__convf) (const _CharT*, _CharT**, _Base...),
     ^~~~~~
/usr/include/c++/7/ext/string_conversions.h:54:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/7/string:52:0,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/basic_string.h:6504:72: note:   cannot convert '__idx' (type 'size_t* {aka long unsigned int*}') to type 'int*'
   { return __gnu_cxx::__stoa(&std::wcstof, "stof", __str.c_str(), __idx); }
                                                                        ^
/usr/include/c++/7/bits/basic_string.h: In function 'double std::__cxx11::stod(const wstring&, size_t*)':
/usr/include/c++/7/bits/basic_string.h:6508:72: error: no matching function for call to '__stoa(double (*)(const wchar_t*, wchar_t**) throw (), const char [5], const wchar_t*, size_t*&)'
   { return __gnu_cxx::__stoa(&std::wcstod, "stod", __str.c_str(), __idx); }
                                                                        ^
In file included from /usr/include/c++/7/bits/basic_string.h:6361:0,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/ext/string_conversions.h:54:5: note: candidate: template<class _TRet, class _Ret, class _CharT, class ... _Base> _Ret __gnu_cxx::__stoa(_TRet (*)(const _CharT*, _CharT**, _Base ...), const char*, const _CharT*, int*, _Base ...)
     __stoa(_TRet (*__convf) (const _CharT*, _CharT**, _Base...),
     ^~~~~~
/usr/include/c++/7/ext/string_conversions.h:54:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/7/string:52:0,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/basic_string.h:6508:72: note:   cannot convert '__idx' (type 'size_t* {aka long unsigned int*}') to type 'int*'
   { return __gnu_cxx::__stoa(&std::wcstod, "stod", __str.c_str(), __idx); }
                                                                        ^
/usr/include/c++/7/bits/basic_string.h: In function 'long double std::__cxx11::stold(const wstring&, size_t*)':
/usr/include/c++/7/bits/basic_string.h:6512:74: error: no matching function for call to '__stoa(long double (*)(const wchar_t*, wchar_t**) throw (), const char [6], const wchar_t*, size_t*&)'
   { return __gnu_cxx::__stoa(&std::wcstold, "stold", __str.c_str(), __idx); }
                                                                          ^
In file included from /usr/include/c++/7/bits/basic_string.h:6361:0,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/ext/string_conversions.h:54:5: note: candidate: template<class _TRet, class _Ret, class _CharT, class ... _Base> _Ret __gnu_cxx::__stoa(_TRet (*)(const _CharT*, _CharT**, _Base ...), const char*, const _CharT*, int*, _Base ...)
     __stoa(_TRet (*__convf) (const _CharT*, _CharT**, _Base...),
     ^~~~~~
/usr/include/c++/7/ext/string_conversions.h:54:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/7/string:52:0,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/basic_string.h:6512:74: note:   cannot convert '__idx' (type 'size_t* {aka long unsigned int*}') to type 'int*'
   { return __gnu_cxx::__stoa(&std::wcstold, "stold", __str.c_str(), __idx); }
                                                                          ^
/usr/include/c++/7/bits/basic_string.h: In function 'std::__cxx11::wstring std::__cxx11::to_wstring(int)':
/usr/include/c++/7/bits/basic_string.h:6519:22: error: no matching function for call to '__to_xstring<std::__cxx11::wstring>(int (*)(wchar_t*, size_t, const wchar_t*, __va_list_tag*) throw (), long unsigned int, const wchar_t [3], int&)'
          L"%d", __val); }
                      ^
In file included from /usr/include/c++/7/bits/basic_string.h:6361:0,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/ext/string_conversions.h:99:5: note: candidate: template<class _String, class _CharT> _String __gnu_cxx::__to_xstring(int (*)(_CharT*, int, const _CharT*, __va_list_tag*), int, const _CharT*, ...)
     __to_xstring(int (*__convf) (_CharT*, std::size_t, const _CharT*,
     ^~~~~~~~~~~~
/usr/include/c++/7/ext/string_conversions.h:99:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/7/string:52:0,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/basic_string.h:6519:22: note:   mismatched types 'int' and 'size_t {aka long unsigned int}'
          L"%d", __val); }
                      ^
/usr/include/c++/7/bits/basic_string.h: In function 'std::__cxx11::wstring std::__cxx11::to_wstring(unsigned int)':
/usr/include/c++/7/bits/basic_string.h:6525:22: error: no matching function for call to '__to_xstring<std::__cxx11::wstring>(int (*)(wchar_t*, size_t, const wchar_t*, __va_list_tag*) throw (), long unsigned int, const wchar_t [3], unsigned int&)'
          L"%u", __val); }
                      ^
In file included from /usr/include/c++/7/bits/basic_string.h:6361:0,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/ext/string_conversions.h:99:5: note: candidate: template<class _String, class _CharT> _String __gnu_cxx::__to_xstring(int (*)(_CharT*, int, const _CharT*, __va_list_tag*), int, const _CharT*, ...)
     __to_xstring(int (*__convf) (_CharT*, std::size_t, const _CharT*,
     ^~~~~~~~~~~~
/usr/include/c++/7/ext/string_conversions.h:99:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/7/string:52:0,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/basic_string.h:6525:22: note:   mismatched types 'int' and 'size_t {aka long unsigned int}'
          L"%u", __val); }
                      ^
/usr/include/c++/7/bits/basic_string.h: In function 'std::__cxx11::wstring std::__cxx11::to_wstring(long int)':
/usr/include/c++/7/bits/basic_string.h:6530:23: error: no matching function for call to '__to_xstring<std::__cxx11::wstring>(int (*)(wchar_t*, size_t, const wchar_t*, __va_list_tag*) throw (), long unsigned int, const wchar_t [4], long int&)'
          L"%ld", __val); }
                       ^
In file included from /usr/include/c++/7/bits/basic_string.h:6361:0,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/ext/string_conversions.h:99:5: note: candidate: template<class _String, class _CharT> _String __gnu_cxx::__to_xstring(int (*)(_CharT*, int, const _CharT*, __va_list_tag*), int, const _CharT*, ...)
     __to_xstring(int (*__convf) (_CharT*, std::size_t, const _CharT*,
     ^~~~~~~~~~~~
/usr/include/c++/7/ext/string_conversions.h:99:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/7/string:52:0,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/basic_string.h:6530:23: note:   mismatched types 'int' and 'size_t {aka long unsigned int}'
          L"%ld", __val); }
                       ^
/usr/include/c++/7/bits/basic_string.h: In function 'std::__cxx11::wstring std::__cxx11::to_wstring(long unsigned int)':
/usr/include/c++/7/bits/basic_string.h:6536:23: error: no matching function for call to '__to_xstring<std::__cxx11::wstring>(int (*)(wchar_t*, size_t, const wchar_t*, __va_list_tag*) throw (), long unsigned int, const wchar_t [4], long unsigned int&)'
          L"%lu", __val); }
                       ^
In file included from /usr/include/c++/7/bits/basic_string.h:6361:0,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/ext/string_conversions.h:99:5: note: candidate: template<class _String, class _CharT> _String __gnu_cxx::__to_xstring(int (*)(_CharT*, int, const _CharT*, __va_list_tag*), int, const _CharT*, ...)
     __to_xstring(int (*__convf) (_CharT*, std::size_t, const _CharT*,
     ^~~~~~~~~~~~
/usr/include/c++/7/ext/string_conversions.h:99:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/7/string:52:0,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/basic_string.h:6536:23: note:   mismatched types 'int' and 'size_t {aka long unsigned int}'
          L"%lu", __val); }
                       ^
/usr/include/c++/7/bits/basic_string.h: In function 'std::__cxx11::wstring std::__cxx11::to_wstring(long long int)':
/usr/include/c++/7/bits/basic_string.h:6542:24: error: no matching function for call to '__to_xstring<std::__cxx11::wstring>(int (*)(wchar_t*, size_t, const wchar_t*, __va_list_tag*) throw (), long unsigned int, const wchar_t [5], long long int&)'
          L"%lld", __val); }
                        ^
In file included from /usr/include/c++/7/bits/basic_string.h:6361:0,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/ext/string_conversions.h:99:5: note: candidate: template<class _String, class _CharT> _String __gnu_cxx::__to_xstring(int (*)(_CharT*, int, const _CharT*, __va_list_tag*), int, const _CharT*, ...)
     __to_xstring(int (*__convf) (_CharT*, std::size_t, const _CharT*,
     ^~~~~~~~~~~~
/usr/include/c++/7/ext/string_conversions.h:99:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/7/string:52:0,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/basic_string.h:6542:24: note:   mismatched types 'int' and 'size_t {aka long unsigned int}'
          L"%lld", __val); }
                        ^
/usr/include/c++/7/bits/basic_string.h: In function 'std::__cxx11::wstring std::__cxx11::to_wstring(long long unsigned int)':
/usr/include/c++/7/bits/basic_string.h:6548:24: error: no matching function for call to '__to_xstring<std::__cxx11::wstring>(int (*)(wchar_t*, size_t, const wchar_t*, __va_list_tag*) throw (), long unsigned int, const wchar_t [5], long long unsigned int&)'
          L"%llu", __val); }
                        ^
In file included from /usr/include/c++/7/bits/basic_string.h:6361:0,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/ext/string_conversions.h:99:5: note: candidate: template<class _String, class _CharT> _String __gnu_cxx::__to_xstring(int (*)(_CharT*, int, const _CharT*, __va_list_tag*), int, const _CharT*, ...)
     __to_xstring(int (*__convf) (_CharT*, std::size_t, const _CharT*,
     ^~~~~~~~~~~~
/usr/include/c++/7/ext/string_conversions.h:99:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/7/string:52:0,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/basic_string.h:6548:24: note:   mismatched types 'int' and 'size_t {aka long unsigned int}'
          L"%llu", __val); }
                        ^
/usr/include/c++/7/bits/basic_string.h: In function 'std::__cxx11::wstring std::__cxx11::to_wstring(float)':
/usr/include/c++/7/bits/basic_string.h:6556:22: error: no matching function for call to '__to_xstring<std::__cxx11::wstring>(int (*)(wchar_t*, size_t, const wchar_t*, __va_list_tag*) throw (), const int&, const wchar_t [3], float&)'
          L"%f", __val);
                      ^
In file included from /usr/include/c++/7/bits/basic_string.h:6361:0,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/ext/string_conversions.h:99:5: note: candidate: template<class _String, class _CharT> _String __gnu_cxx::__to_xstring(int (*)(_CharT*, int, const _CharT*, __va_list_tag*), int, const _CharT*, ...)
     __to_xstring(int (*__convf) (_CharT*, std::size_t, const _CharT*,
     ^~~~~~~~~~~~
/usr/include/c++/7/ext/string_conversions.h:99:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/7/string:52:0,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/basic_string.h:6556:22: note:   mismatched types 'int' and 'size_t {aka long unsigned int}'
          L"%f", __val);
                      ^
/usr/include/c++/7/bits/basic_string.h: In function 'std::__cxx11::wstring std::__cxx11::to_wstring(double)':
/usr/include/c++/7/bits/basic_string.h:6565:22: error: no matching function for call to '__to_xstring<std::__cxx11::wstring>(int (*)(wchar_t*, size_t, const wchar_t*, __va_list_tag*) throw (), const int&, const wchar_t [3], double&)'
          L"%f", __val);
                      ^
In file included from /usr/include/c++/7/bits/basic_string.h:6361:0,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/ext/string_conversions.h:99:5: note: candidate: template<class _String, class _CharT> _String __gnu_cxx::__to_xstring(int (*)(_CharT*, int, const _CharT*, __va_list_tag*), int, const _CharT*, ...)
     __to_xstring(int (*__convf) (_CharT*, std::size_t, const _CharT*,
     ^~~~~~~~~~~~
/usr/include/c++/7/ext/string_conversions.h:99:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/7/string:52:0,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/basic_string.h:6565:22: note:   mismatched types 'int' and 'size_t {aka long unsigned int}'
          L"%f", __val);
                      ^
/usr/include/c++/7/bits/basic_string.h: In function 'std::__cxx11::wstring std::__cxx11::to_wstring(long double)':
/usr/include/c++/7/bits/basic_string.h:6574:23: error: no matching function for call to '__to_xstring<std::__cxx11::wstring>(int (*)(wchar_t*, size_t, const wchar_t*, __va_list_tag*) throw (), const int&, const wchar_t [4], long double&)'
          L"%Lf", __val);
                       ^
In file included from /usr/include/c++/7/bits/basic_string.h:6361:0,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/ext/string_conversions.h:99:5: note: candidate: template<class _String, class _CharT> _String __gnu_cxx::__to_xstring(int (*)(_CharT*, int, const _CharT*, __va_list_tag*), int, const _CharT*, ...)
     __to_xstring(int (*__convf) (_CharT*, std::size_t, const _CharT*,
     ^~~~~~~~~~~~
/usr/include/c++/7/ext/string_conversions.h:99:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/7/string:52:0,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/basic_string.h:6574:23: note:   mismatched types 'int' and 'size_t {aka long unsigned int}'
          L"%Lf", __val);
                       ^
In file included from /usr/include/c++/7/string:52:0,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/basic_string.h: In member function 'size_t std::hash<std::__cxx11::basic_string<char> >::operator()(const string&) const':
/usr/include/c++/7/bits/basic_string.h:6603:54: error: 'const string {aka const class std::__cxx11::basic_string<char>}' has no member named 'length'
       { return std::_Hash_impl::hash(__s.data(), __s.length()); }
                                                      ^~~~~~
/usr/include/c++/7/bits/basic_string.h: In member function 'size_t std::hash<std::__cxx11::basic_string<wchar_t> >::operator()(const wstring&) const':
/usr/include/c++/7/bits/basic_string.h:6619:42: error: 'const wstring {aka const class std::__cxx11::basic_string<wchar_t>}' has no member named 'length'
                                      __s.length() * sizeof(wchar_t)); }
                                          ^~~~~~
In file included from /usr/include/c++/7/bits/basic_string.h:40:0,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/ext/alloc_traits.h: In instantiation of 'struct __gnu_cxx::__alloc_traits<std::allocator<char16_t> >':
/usr/include/c++/7/bits/basic_string.h:80:24:   required from 'class std::__cxx11::basic_string<char16_t>'
/usr/include/c++/7/bits/basic_string.h:6636:41:   required from here
/usr/include/c++/7/ext/alloc_traits.h:61:53: error: no type named 'size_type' in 'struct std::allocator_traits<std::allocator<char16_t> >'
     typedef typename _Base_type::size_type          size_type;
                                                     ^~~~~~~~~
/usr/include/c++/7/ext/alloc_traits.h:62:53: error: no type named 'difference_type' in 'struct std::allocator_traits<std::allocator<char16_t> >'
     typedef typename _Base_type::difference_type    difference_type;
                                                     ^~~~~~~~~~~~~~~
/usr/include/c++/7/ext/alloc_traits.h:70:23: error: no members matching '__gnu_cxx::__alloc_traits<std::allocator<char16_t> >::_Base_type {aka std::allocator_traits<std::allocator<char16_t> >}::max_size' in '__gnu_cxx::__alloc_traits<std::allocator<char16_t> >::_Base_type {aka struct std::allocator_traits<std::allocator<char16_t> >}'
     using _Base_type::max_size;
                       ^~~~~~~~
In file included from /usr/include/c++/7/string:52:0,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/basic_string.h: In member function 'size_t std::hash<std::__cxx11::basic_string<char16_t> >::operator()(const u16string&) const':
/usr/include/c++/7/bits/basic_string.h:6637:42: error: 'const u16string {aka const class std::__cxx11::basic_string<char16_t>}' has no member named 'length'
                                      __s.length() * sizeof(char16_t)); }
                                          ^~~~~~
In file included from /usr/include/c++/7/bits/basic_string.h:40:0,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/ext/alloc_traits.h: In instantiation of 'struct __gnu_cxx::__alloc_traits<std::allocator<char32_t> >':
/usr/include/c++/7/bits/basic_string.h:80:24:   required from 'class std::__cxx11::basic_string<char32_t>'
/usr/include/c++/7/bits/basic_string.h:6651:41:   required from here
/usr/include/c++/7/ext/alloc_traits.h:61:53: error: no type named 'size_type' in 'struct std::allocator_traits<std::allocator<char32_t> >'
     typedef typename _Base_type::size_type          size_type;
                                                     ^~~~~~~~~
/usr/include/c++/7/ext/alloc_traits.h:62:53: error: no type named 'difference_type' in 'struct std::allocator_traits<std::allocator<char32_t> >'
     typedef typename _Base_type::difference_type    difference_type;
                                                     ^~~~~~~~~~~~~~~
/usr/include/c++/7/ext/alloc_traits.h:70:23: error: no members matching '__gnu_cxx::__alloc_traits<std::allocator<char32_t> >::_Base_type {aka std::allocator_traits<std::allocator<char32_t> >}::max_size' in '__gnu_cxx::__alloc_traits<std::allocator<char32_t> >::_Base_type {aka struct std::allocator_traits<std::allocator<char32_t> >}'
     using _Base_type::max_size;
                       ^~~~~~~~
In file included from /usr/include/c++/7/string:52:0,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/basic_string.h: In member function 'size_t std::hash<std::__cxx11::basic_string<char32_t> >::operator()(const u32string&) const':
/usr/include/c++/7/bits/basic_string.h:6652:42: error: 'const u32string {aka const class std::__cxx11::basic_string<char32_t>}' has no member named 'length'
                                      __s.length() * sizeof(char32_t)); }
                                          ^~~~~~
In file included from /usr/include/c++/7/string:53:0,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/basic_string.tcc: In function 'std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&)':
/usr/include/c++/7/bits/basic_string.tcc:1487:14: error: 'streamsize' does not name a type; did you mean 'streambuf'?
        const streamsize __w = __in.width();
              ^~~~~~~~~~
              streambuf
/usr/include/c++/7/bits/basic_string.tcc:1488:32: error: '__w' was not declared in this scope
        const __size_type __n = __w > 0 ? static_cast<__size_type>(__w)
                                ^~~
/usr/include/c++/7/bits/basic_string.tcc:1488:32: note: suggested alternative: '__n'
        const __size_type __n = __w > 0 ? static_cast<__size_type>(__w)
                                ^~~
                                __n
In file included from /usr/include/c++/7/ios:42:0,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/ios_base.h: At global scope:
/usr/include/c++/7/bits/ios_base.h:520:5: error: 'streamsize' does not name a type; did you mean 'streampos'?
     streamsize  _M_precision;
     ^~~~~~~~~~
     streampos
/usr/include/c++/7/bits/ios_base.h:521:5: error: 'streamsize' does not name a type; did you mean 'streampos'?
     streamsize  _M_width;
     ^~~~~~~~~~
     streampos
/usr/include/c++/7/bits/ios_base.h:688:5: error: 'streamsize' does not name a type; did you mean 'streampos'?
     streamsize
     ^~~~~~~~~~
     streampos
/usr/include/c++/7/bits/ios_base.h:697:5: error: 'streamsize' does not name a type; did you mean 'streampos'?
     streamsize
     ^~~~~~~~~~
     streampos
/usr/include/c++/7/bits/ios_base.h:711:5: error: 'streamsize' does not name a type; did you mean 'streampos'?
     streamsize
     ^~~~~~~~~~
     streampos
/usr/include/c++/7/bits/ios_base.h:720:5: error: 'streamsize' does not name a type; did you mean 'streampos'?
     streamsize
     ^~~~~~~~~~
     streampos
In file included from /usr/include/c++/7/ios:43:0,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/streambuf:50:5: error: 'streamsize' does not name a type; did you mean 'streambuf'?
     streamsize
     ^~~~~~~~~~
     streambuf
/usr/include/c++/7/streambuf:147:14: error: 'streamsize' does not name a type; did you mean 'streambuf'?
       friend streamsize
              ^~~~~~~~~~
              streambuf
/usr/include/c++/7/streambuf:239:33: error: 'streamsize' has not been declared
       pubsetbuf(char_type* __s, streamsize __n)
                                 ^~~~~~~~~~
/usr/include/c++/7/streambuf:283:7: error: 'streamsize' does not name a type; did you mean 'streambuf'?
       streamsize
       ^~~~~~~~~~
       streambuf
/usr/include/c++/7/streambuf:356:7: error: 'streamsize' does not name a type; did you mean 'streambuf'?
       streamsize
       ^~~~~~~~~~
       streambuf
/usr/include/c++/7/streambuf:449:7: error: 'streamsize' does not name a type; did you mean 'streambuf'?
       streamsize
       ^~~~~~~~~~
       streambuf
/usr/include/c++/7/streambuf:591:26: error: 'streamsize' has not been declared
       setbuf(char_type*, streamsize)
                          ^~~~~~~~~~
/usr/include/c++/7/streambuf:648:15: error: 'streamsize' does not name a type; did you mean 'streambuf'?
       virtual streamsize
               ^~~~~~~~~~
               streambuf
/usr/include/c++/7/streambuf:664:15: error: 'streamsize' does not name a type; did you mean 'streambuf'?
       virtual streamsize
               ^~~~~~~~~~
               streambuf
/usr/include/c++/7/streambuf:741:15: error: 'streamsize' does not name a type; did you mean 'streambuf'?
       virtual streamsize
               ^~~~~~~~~~
               streambuf
/usr/include/c++/7/streambuf:794:20: error: 'streamsize' has not been declared
       __safe_gbump(streamsize __n) { _M_in_cur += __n; }
                    ^~~~~~~~~~
/usr/include/c++/7/streambuf:797:20: error: 'streamsize' has not been declared
       __safe_pbump(streamsize __n) { _M_out_cur += __n; }
                    ^~~~~~~~~~
/usr/include/c++/7/streambuf:837:5: error: 'streamsize' does not name a type; did you mean 'streambuf'?
     streamsize
     ^~~~~~~~~~
     streambuf
/usr/include/c++/7/streambuf:842:5: error: 'streamsize' does not name a type; did you mean 'streambuf'?
     streamsize
     ^~~~~~~~~~
     streambuf
In file included from /usr/include/c++/7/streambuf:850:0,
                 from /usr/include/c++/7/ios:43,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/streambuf.tcc:44:5: error: 'streamsize' does not name a type; did you mean 'streambuf'?
     streamsize
     ^~~~~~~~~~
     streambuf
/usr/include/c++/7/bits/streambuf.tcc:78:5: error: 'streamsize' does not name a type; did you mean 'streambuf'?
     streamsize
     ^~~~~~~~~~
     streambuf
/usr/include/c++/7/bits/streambuf.tcc:115:5: error: 'streamsize' does not name a type; did you mean 'streambuf'?
     streamsize
     ^~~~~~~~~~
     streambuf
/usr/include/c++/7/bits/streambuf.tcc:138:12: error: 'streamsize' does not name a type; did you mean 'streambuf'?
     inline streamsize
            ^~~~~~~~~~
            streambuf
/usr/include/c++/7/bits/streambuf.tcc:151:5: error: 'streamsize' is not a template function
     streamsize
     ^~~~~~~~~~
/usr/include/c++/7/bits/streambuf.tcc:152:5: error: expected ';' before '__copy_streambufs'
     __copy_streambufs(basic_streambuf<char>*,
     ^~~~~~~~~~~~~~~~~
/usr/include/c++/7/bits/streambuf.tcc:155:5: error: 'streamsize' is not a template function
     streamsize
     ^~~~~~~~~~
/usr/include/c++/7/bits/streambuf.tcc:156:5: error: expected ';' before '__copy_streambufs_eof'
     __copy_streambufs_eof(basic_streambuf<char>*,
     ^~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/7/bits/streambuf.tcc:162:5: error: 'streamsize' is not a template function
     streamsize
     ^~~~~~~~~~
/usr/include/c++/7/bits/streambuf.tcc:163:5: error: expected ';' before '__copy_streambufs'
     __copy_streambufs(basic_streambuf<wchar_t>*,
     ^~~~~~~~~~~~~~~~~
/usr/include/c++/7/bits/streambuf.tcc:166:5: error: 'streamsize' is not a template function
     streamsize
     ^~~~~~~~~~
/usr/include/c++/7/bits/streambuf.tcc:167:5: error: expected ';' before '__copy_streambufs_eof'
     __copy_streambufs_eof(basic_streambuf<wchar_t>*,
     ^~~~~~~~~~~~~~~~~~~~~
In file included from /usr/include/c++/7/bits/locale_facets.h:48:0,
                 from /usr/include/c++/7/bits/basic_ios.h:37,
                 from /usr/include/c++/7/ios:44,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/streambuf_iterator.h:279:34: error: 'streamsize' has not been declared
       _M_put(const _CharT* __ws, streamsize __len)
                                  ^~~~~~~~~~
/usr/include/c++/7/bits/streambuf_iterator.h: In function 'typename __gnu_cxx::__enable_if<std::__is_char<_CharT>::__value, std::ostreambuf_iterator<_CharT, std::char_traits<_CharT> > >::__type std::__copy_move_a2(_CharT*, _CharT*, std::ostreambuf_iterator<_CharT, std::char_traits<_CharT> >)':
/usr/include/c++/7/bits/streambuf_iterator.h:313:13: error: 'streamsize' does not name a type; did you mean 'streambuf'?
       const streamsize __num = __last - __first;
             ^~~~~~~~~~
             streambuf
/usr/include/c++/7/bits/streambuf_iterator.h:314:11: error: '__num' was not declared in this scope
       if (__num > 0)
           ^~~~~
/usr/include/c++/7/bits/streambuf_iterator.h:314:11: note: suggested alternative: '__wur'
       if (__num > 0)
           ^~~~~
           __wur
/usr/include/c++/7/bits/streambuf_iterator.h: In function 'typename __gnu_cxx::__enable_if<std::__is_char<_CharT>::__value, std::ostreambuf_iterator<_CharT, std::char_traits<_CharT> > >::__type std::__copy_move_a2(const _CharT*, const _CharT*, std::ostreambuf_iterator<_CharT, std::char_traits<_CharT> >)':
/usr/include/c++/7/bits/streambuf_iterator.h:325:13: error: 'streamsize' does not name a type; did you mean 'streambuf'?
       const streamsize __num = __last - __first;
             ^~~~~~~~~~
             streambuf
/usr/include/c++/7/bits/streambuf_iterator.h:326:11: error: '__num' was not declared in this scope
       if (__num > 0)
           ^~~~~
/usr/include/c++/7/bits/streambuf_iterator.h:326:11: note: suggested alternative: '__wur'
       if (__num > 0)
           ^~~~~
           __wur
/usr/include/c++/7/bits/streambuf_iterator.h: In function 'typename __gnu_cxx::__enable_if<std::__is_char<_CharT>::__value, _CharT*>::__type std::__copy_move_a2(std::istreambuf_iterator<_CharT, std::char_traits<_CharT> >, std::istreambuf_iterator<_CharT, std::char_traits<_CharT> >, _CharT*)':
/usr/include/c++/7/bits/streambuf_iterator.h:348:14: error: 'streamsize' does not name a type; did you mean 'streambuf'?
        const streamsize __n = __sb->egptr() - __sb->gptr();
              ^~~~~~~~~~
              streambuf
/usr/include/c++/7/bits/streambuf_iterator.h:349:12: error: '__n' was not declared in this scope
        if (__n > 1)
            ^~~
/usr/include/c++/7/bits/streambuf_iterator.h:349:12: note: suggested alternative: '__c'
        if (__n > 1)
            ^~~
            __c
/usr/include/c++/7/bits/streambuf_iterator.h: In function 'typename __gnu_cxx::__enable_if<std::__is_char<_CharT2>::__value, std::istreambuf_iterator<_CharT> >::__type std::find(std::istreambuf_iterator<_CharT>, std::istreambuf_iterator<_CharT>, const _CharT2&)':
/usr/include/c++/7/bits/streambuf_iterator.h:385:8: error: 'streamsize' was not declared in this scope
        streamsize __n = __sb->egptr() - __sb->gptr();
        ^~~~~~~~~~
/usr/include/c++/7/bits/streambuf_iterator.h:385:8: note: suggested alternative: 'streambuf'
        streamsize __n = __sb->egptr() - __sb->gptr();
        ^~~~~~~~~~
        streambuf
/usr/include/c++/7/bits/streambuf_iterator.h:386:12: error: '__n' was not declared in this scope
        if (__n > 1)
            ^~~
/usr/include/c++/7/bits/streambuf_iterator.h:386:12: note: suggested alternative: '__c'
        if (__n > 1)
            ^~~
            __c
In file included from /usr/include/c++/7/bits/basic_ios.h:37:0,
                 from /usr/include/c++/7/ios:44,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/locale_facets.h: At global scope:
/usr/include/c++/7/bits/locale_facets.h:99:29: error: 'streamsize' has not been declared
       const _CharT* __olds, streamsize __newlen, streamsize __oldlen);
                             ^~~~~~~~~~
/usr/include/c++/7/bits/locale_facets.h:99:50: error: 'streamsize' has not been declared
       const _CharT* __olds, streamsize __newlen, streamsize __oldlen);
                                                  ^~~~~~~~~~
In file included from /usr/include/c++/7/bits/basic_ios.h:37:0,
                 from /usr/include/c++/7/ios:44,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/locale_facets.h:2484:32: error: 'streamsize' has not been declared
       _M_pad(char_type __fill, streamsize __w, ios_base& __io,
                                ^~~~~~~~~~
In file included from /usr/include/c++/7/bits/locale_facets.h:2651:0,
                 from /usr/include/c++/7/bits/basic_ios.h:37,
                 from /usr/include/c++/7/ios:44,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/locale_facets.tcc: In member function 'void std::__numpunct_cache<_CharT>::_M_cache(const std::locale&)':
/usr/include/c++/7/bits/locale_facets.tcc:88:27: error: 'const string {aka const class std::__cxx11::basic_string<char>}' has no member named 'size'
    _M_grouping_size = __g.size();
                           ^~~~
/usr/include/c++/7/bits/locale_facets.tcc:90:8: error: 'const string {aka const class std::__cxx11::basic_string<char>}' has no member named 'copy'
    __g.copy(__grouping, _M_grouping_size);
        ^~~~
/usr/include/c++/7/bits/locale_facets.tcc: In member function '_InIter std::num_get<_CharT, _InIter>::_M_extract_float(_InIter, _InIter, std::ios_base&, std::ios_base::iostate&, std::__cxx11::string&) const':
/usr/include/c++/7/bits/locale_facets.tcc:211:19: error: 'std::__cxx11::string {aka class std::__cxx11::basic_string<char>}' has no member named 'reserve'
  __found_grouping.reserve(32);
                   ^~~~~~~
/usr/include/c++/7/bits/locale_facets.tcc:296:28: error: 'std::__cxx11::string {aka class std::__cxx11::basic_string<char>}' has no member named 'size'
       if (__found_grouping.size())
                            ^~~~
/usr/include/c++/7/bits/locale_facets.tcc:319:28: error: 'std::__cxx11::string {aka class std::__cxx11::basic_string<char>}' has no member named 'size'
       if (__found_grouping.size() && !__found_dec)
                            ^~~~
/usr/include/c++/7/bits/locale_facets.tcc:355:28: error: 'std::__cxx11::string {aka class std::__cxx11::basic_string<char>}' has no member named 'size'
       if (__found_grouping.size())
                            ^~~~
/usr/include/c++/7/bits/locale_facets.tcc: In member function '_InIter std::num_get<_CharT, _InIter>::_M_extract_int(_InIter, _InIter, std::ios_base&, std::ios_base::iostate&, _ValueT&) const':
/usr/include/c++/7/bits/locale_facets.tcc:468:21: error: 'std::__cxx11::string {aka class std::__cxx11::basic_string<char>}' has no member named 'reserve'
    __found_grouping.reserve(32);
                     ^~~~~~~
/usr/include/c++/7/bits/locale_facets.tcc:554:23: error: 'std::__cxx11::string {aka class std::__cxx11::basic_string<char>}' has no member named 'size'
  if (__found_grouping.size())
                       ^~~~
/usr/include/c++/7/bits/locale_facets.tcc:567:56: error: 'std::__cxx11::string {aka class std::__cxx11::basic_string<char>}' has no member named 'size'
  if ((!__sep_pos && !__found_zero && !__found_grouping.size())
                                                        ^~~~
/usr/include/c++/7/bits/locale_facets.tcc: In member function 'virtual _InIter std::num_get<_CharT, _InIter>::do_get(std::num_get<_CharT, _InIter>::iter_type, std::num_get<_CharT, _InIter>::iter_type, std::ios_base&, std::ios_base::iostate&, float&) const':
/usr/include/c++/7/bits/locale_facets.tcc:695:14: error: 'std::__cxx11::string {aka class std::__cxx11::basic_string<char>}' has no member named 'reserve'
       __xtrc.reserve(32);
              ^~~~~~~
/usr/include/c++/7/bits/locale_facets.tcc: In member function 'virtual _InIter std::num_get<_CharT, _InIter>::do_get(std::num_get<_CharT, _InIter>::iter_type, std::num_get<_CharT, _InIter>::iter_type, std::ios_base&, std::ios_base::iostate&, double&) const':
/usr/include/c++/7/bits/locale_facets.tcc:710:14: error: 'std::__cxx11::string {aka class std::__cxx11::basic_string<char>}' has no member named 'reserve'
       __xtrc.reserve(32);
              ^~~~~~~
/usr/include/c++/7/bits/locale_facets.tcc: In member function 'virtual _InIter std::num_get<_CharT, _InIter>::do_get(std::num_get<_CharT, _InIter>::iter_type, std::num_get<_CharT, _InIter>::iter_type, std::ios_base&, std::ios_base::iostate&, long double&) const':
/usr/include/c++/7/bits/locale_facets.tcc:742:14: error: 'std::__cxx11::string {aka class std::__cxx11::basic_string<char>}' has no member named 'reserve'
       __xtrc.reserve(32);
              ^~~~~~~
/usr/include/c++/7/bits/locale_facets.tcc: At global scope:
/usr/include/c++/7/bits/locale_facets.tcc:780:27: error: 'streamsize' has not been declared
     _M_pad(_CharT __fill, streamsize __w, ios_base& __io,
                           ^~~~~~~~~~
/usr/include/c++/7/bits/locale_facets.tcc: In member function '_OutIter std::num_put<_CharT, _OutIter>::_M_insert_int(_OutIter, std::ios_base&, _CharT, _ValueT) const':
/usr/include/c++/7/bits/locale_facets.tcc:921:8: error: 'streamsize' does not name a type; did you mean 'streambuf'?
  const streamsize __w = __io.width();
        ^~~~~~~~~~
        streambuf
/usr/include/c++/7/bits/locale_facets.tcc:922:6: error: '__w' was not declared in this scope
  if (__w > static_cast<streamsize>(__len))
      ^~~
/usr/include/c++/7/bits/locale_facets.tcc:922:6: note: suggested alternative: '__u'
  if (__w > static_cast<streamsize>(__len))
      ^~~
      __u
/usr/include/c++/7/bits/locale_facets.tcc:922:24: error: 'streamsize' does not name a type; did you mean 'streambuf'?
  if (__w > static_cast<streamsize>(__len))
                        ^~~~~~~~~~
                        streambuf
/usr/include/c++/7/bits/locale_facets.tcc:929:7: error: 'class std::ios_base' has no member named 'width'
  __io.width(0);
       ^~~~~
/usr/include/c++/7/bits/locale_facets.tcc: In member function '_OutIter std::num_put<_CharT, _OutIter>::_M_insert_float(_OutIter, std::ios_base&, _CharT, char, _ValueT) const':
/usr/include/c++/7/bits/locale_facets.tcc:984:8: error: 'streamsize' does not name a type; did you mean 'streambuf'?
  const streamsize __prec = __io.precision() < 0 ? 6 : __io.precision();
        ^~~~~~~~~~
        streambuf
/usr/include/c++/7/bits/locale_facets.tcc:1006:14: error: '__prec' was not declared in this scope
      __fbuf, __prec, __v);
              ^~~~~~
/usr/include/c++/7/bits/locale_facets.tcc:1006:14: note: suggested alternative: '__pad'
      __fbuf, __prec, __v);
              ^~~~~~
              __pad
/usr/include/c++/7/bits/locale_facets.tcc:1018:18: error: '__prec' was not declared in this scope
          __fbuf, __prec, __v);
                  ^~~~~~
/usr/include/c++/7/bits/locale_facets.tcc:1018:18: note: suggested alternative: '__pad'
          __fbuf, __prec, __v);
                  ^~~~~~
                  __pad
/usr/include/c++/7/bits/locale_facets.tcc:1071:6: error: 'streamsize' was not declared in this scope
      streamsize __off = 0;
      ^~~~~~~~~~
/usr/include/c++/7/bits/locale_facets.tcc:1071:6: note: suggested alternative: 'streambuf'
      streamsize __off = 0;
      ^~~~~~~~~~
      streambuf
/usr/include/c++/7/bits/locale_facets.tcc:1074:3: error: '__off' was not declared in this scope
   __off = 1;
   ^~~~~
/usr/include/c++/7/bits/locale_facets.tcc:1074:3: note: suggested alternative: '__or_'
   __off = 1;
   ^~~~~
   __or_
/usr/include/c++/7/bits/locale_facets.tcc:1080:45: error: '__off' was not declared in this scope
       __lc->_M_thousands_sep, __wp, __ws2 + __off,
                                             ^~~~~
/usr/include/c++/7/bits/locale_facets.tcc:1080:45: note: suggested alternative: '__or_'
       __lc->_M_thousands_sep, __wp, __ws2 + __off,
                                             ^~~~~
                                             __or_
/usr/include/c++/7/bits/locale_facets.tcc:1088:8: error: 'streamsize' does not name a type; did you mean 'streambuf'?
  const streamsize __w = __io.width();
        ^~~~~~~~~~
        streambuf
/usr/include/c++/7/bits/locale_facets.tcc:1089:6: error: '__w' was not declared in this scope
  if (__w > static_cast<streamsize>(__len))
      ^~~
/usr/include/c++/7/bits/locale_facets.tcc:1089:6: note: suggested alternative: '__p'
  if (__w > static_cast<streamsize>(__len))
      ^~~
      __p
/usr/include/c++/7/bits/locale_facets.tcc:1089:24: error: 'streamsize' does not name a type; did you mean 'streambuf'?
  if (__w > static_cast<streamsize>(__len))
                        ^~~~~~~~~~
                        streambuf
/usr/include/c++/7/bits/locale_facets.tcc:1096:7: error: 'class std::ios_base' has no member named 'width'
  __io.width(0);
       ^~~~~
/usr/include/c++/7/bits/locale_facets.tcc: In member function 'virtual _OutIter std::num_put<_CharT, _OutIter>::do_put(std::num_put<_CharT, _OutIter>::iter_type, std::ios_base&, std::num_put<_CharT, _OutIter>::char_type, bool) const':
/usr/include/c++/7/bits/locale_facets.tcc:1126:10: error: 'streamsize' does not name a type; did you mean 'streambuf'?
    const streamsize __w = __io.width();
          ^~~~~~~~~~
          streambuf
/usr/include/c++/7/bits/locale_facets.tcc:1127:8: error: '__w' was not declared in this scope
    if (__w > static_cast<streamsize>(__len))
        ^~~
/usr/include/c++/7/bits/locale_facets.tcc:1127:8: note: suggested alternative: '__s'
    if (__w > static_cast<streamsize>(__len))
        ^~~
        __s
/usr/include/c++/7/bits/locale_facets.tcc:1127:26: error: 'streamsize' does not name a type; did you mean 'streambuf'?
    if (__w > static_cast<streamsize>(__len))
                          ^~~~~~~~~~
                          streambuf
/usr/include/c++/7/bits/locale_facets.tcc:1129:14: error: 'streamsize' does not name a type; did you mean 'streambuf'?
        const streamsize __plen = __w - __len;
              ^~~~~~~~~~
              streambuf
/usr/include/c++/7/bits/locale_facets.tcc:1132:10: error: '__plen' was not declared in this scope
        * __plen));
          ^~~~~~
/usr/include/c++/7/bits/locale_facets.tcc:1132:10: note: suggested alternative: '__len'
        * __plen));
          ^~~~~~
          __len
/usr/include/c++/7/bits/locale_facets.tcc:1135:13: error: 'class std::ios_base' has no member named 'width'
        __io.width(0);
             ^~~~~
/usr/include/c++/7/bits/locale_facets.tcc:1149:9: error: 'class std::ios_base' has no member named 'width'
    __io.width(0);
         ^~~~~
/usr/include/c++/7/bits/locale_facets.tcc: At global scope:
/usr/include/c++/7/bits/locale_facets.tcc:1210:8: error: 'streamsize' has not been declared
        streamsize __newlen, streamsize __oldlen)
        ^~~~~~~~~~
/usr/include/c++/7/bits/locale_facets.tcc:1210:29: error: 'streamsize' has not been declared
        streamsize __newlen, streamsize __oldlen)
                             ^~~~~~~~~~
In file included from /usr/include/c++/7/iostream:39:0,
                 from foo.cc:5:
/usr/include/c++/7/ostream:311:38: error: 'streamsize' has not been declared
       _M_write(const char_type* __s, streamsize __n)
                                      ^~~~~~~~~~
/usr/include/c++/7/ostream:335:35: error: 'streamsize' has not been declared
       write(const char_type* __s, streamsize __n);
                                   ^~~~~~~~~~
/usr/include/c++/7/ostream: In member function 'void std::basic_ostream<_CharT, _Traits>::_M_write(const char_type*, int)':
/usr/include/c++/7/ostream:313:8: error: 'streamsize' does not name a type; did you mean 'streambuf'?
  const streamsize __put = this->rdbuf()->sputn(__s, __n);
        ^~~~~~~~~~
        streambuf
/usr/include/c++/7/ostream:314:6: error: '__put' was not declared in this scope
  if (__put != __n)
      ^~~~~
/usr/include/c++/7/ostream:314:6: note: suggested alternative: 'put'
  if (__put != __n)
      ^~~~~
      put
/usr/include/c++/7/ostream: In function 'std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&, const _CharT*)':
/usr/include/c++/7/ostream:545:17: error: 'streamsize' does not name a type; did you mean 'streambuf'?
     static_cast<streamsize>(_Traits::length(__s)));
                 ^~~~~~~~~~
                 streambuf
/usr/include/c++/7/ostream: In function 'std::basic_ostream<char, _Traits>& std::operator<<(std::basic_ostream<char, _Traits>&, const char*)':
/usr/include/c++/7/ostream:562:17: error: 'streamsize' does not name a type; did you mean 'streambuf'?
     static_cast<streamsize>(_Traits::length(__s)));
                 ^~~~~~~~~~
                 streambuf
In file included from /usr/include/c++/7/ostream:693:0,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/ostream.tcc: At global scope:
/usr/include/c++/7/bits/ostream.tcc:183:30: error: 'streamsize' has not been declared
     write(const _CharT* __s, streamsize __n)
                              ^~~~~~~~~~
In file included from /usr/include/c++/7/iostream:40:0,
                 from foo.cc:5:
/usr/include/c++/7/istream:82:7: error: 'streamsize' does not name a type; did you mean 'streambuf'?
       streamsize   _M_gcount;
       ^~~~~~~~~~
       streambuf
/usr/include/c++/7/istream:268:7: error: 'streamsize' does not name a type; did you mean 'streambuf'?
       streamsize
       ^~~~~~~~~~
       streambuf
/usr/include/c++/7/istream:343:27: error: 'streamsize' has not been declared
       get(char_type* __s, streamsize __n, char_type __delim);
                           ^~~~~~~~~~
/usr/include/c++/7/istream:354:27: error: 'streamsize' has not been declared
       get(char_type* __s, streamsize __n)
                           ^~~~~~~~~~
/usr/include/c++/7/istream:416:31: error: 'streamsize' has not been declared
       getline(char_type* __s, streamsize __n, char_type __delim);
                               ^~~~~~~~~~
/usr/include/c++/7/istream:427:31: error: 'streamsize' has not been declared
       getline(char_type* __s, streamsize __n)
                               ^~~~~~~~~~
/usr/include/c++/7/istream:451:7: error: expected ';' at end of member declaration
       ignore(streamsize __n, int_type __delim);
       ^~~~~~
/usr/include/c++/7/istream:451:25: error: expected ')' before '__n'
       ignore(streamsize __n, int_type __delim);
                         ^~~
/usr/include/c++/7/istream:454:7: error: expected ';' at end of member declaration
       ignore(streamsize __n);
       ^~~~~~
/usr/include/c++/7/istream:454:14: error: redeclaration of 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::ignore'
       ignore(streamsize __n);
              ^~~~~~~~~~
/usr/include/c++/7/istream:451:14: note: previous declaration 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::ignore'
       ignore(streamsize __n, int_type __delim);
              ^~~~~~~~~~
/usr/include/c++/7/istream:454:25: error: expected ')' before '__n'
       ignore(streamsize __n);
                         ^~~
/usr/include/c++/7/istream:457:14: error: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::ignore()' conflicts with a previous declaration
       ignore();
              ^
/usr/include/c++/7/istream:451:14: note: previous declaration 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::ignore'
       ignore(streamsize __n, int_type __delim);
              ^~~~~~~~~~
/usr/include/c++/7/istream:486:28: error: 'streamsize' has not been declared
       read(char_type* __s, streamsize __n);
                            ^~~~~~~~~~
/usr/include/c++/7/istream:504:7: error: 'streamsize' does not name a type; did you mean 'streambuf'?
       streamsize
       ^~~~~~~~~~
       streambuf
/usr/include/c++/7/istream: In constructor 'std::basic_istream<_CharT, _Traits>::basic_istream(std::basic_istream<_CharT, _Traits>::__streambuf_type*)':
/usr/include/c++/7/istream:94:9: error: class 'std::basic_istream<_CharT, _Traits>' does not have any field named '_M_gcount'
       : _M_gcount(streamsize(0))
         ^~~~~~~~~
/usr/include/c++/7/istream:94:19: error: there are no arguments to 'streamsize' that depend on a template parameter, so a declaration of 'streamsize' must be available [-fpermissive]
       : _M_gcount(streamsize(0))
                   ^~~~~~~~~~
/usr/include/c++/7/istream:94:19: note: (if you use '-fpermissive', G++ will accept your code, but allowing the use of an undeclared name is deprecated)
/usr/include/c++/7/istream: In destructor 'virtual std::basic_istream<_CharT, _Traits>::~basic_istream()':
/usr/include/c++/7/istream:104:9: error: '_M_gcount' was not declared in this scope
       { _M_gcount = streamsize(0); }
         ^~~~~~~~~
/usr/include/c++/7/istream:104:9: note: suggested alternative: '_S_out'
       { _M_gcount = streamsize(0); }
         ^~~~~~~~~
         _S_out
/usr/include/c++/7/istream:104:21: error: there are no arguments to 'streamsize' that depend on a template parameter, so a declaration of 'streamsize' must be available [-fpermissive]
       { _M_gcount = streamsize(0); }
                     ^~~~~~~~~~
/usr/include/c++/7/istream: In constructor 'std::basic_istream<_CharT, _Traits>::basic_istream()':
/usr/include/c++/7/istream:607:9: error: class 'std::basic_istream<_CharT, _Traits>' does not have any field named '_M_gcount'
       : _M_gcount(streamsize(0))
         ^~~~~~~~~
/usr/include/c++/7/istream:607:19: error: there are no arguments to 'streamsize' that depend on a template parameter, so a declaration of 'streamsize' must be available [-fpermissive]
       : _M_gcount(streamsize(0))
                   ^~~~~~~~~~
/usr/include/c++/7/istream: In constructor 'std::basic_istream<_CharT, _Traits>::basic_istream(std::basic_istream<_CharT, _Traits>&&)':
/usr/include/c++/7/istream:614:23: error: class 'std::basic_istream<_CharT, _Traits>' does not have any field named '_M_gcount'
       : __ios_type(), _M_gcount(__rhs._M_gcount)
                       ^~~~~~~~~
/usr/include/c++/7/istream: In member function 'void std::basic_istream<_CharT, _Traits>::swap(std::basic_istream<_CharT, _Traits>&)':
/usr/include/c++/7/istream:635:12: error: '_M_gcount' was not declared in this scope
  std::swap(_M_gcount, __rhs._M_gcount);
            ^~~~~~~~~
/usr/include/c++/7/istream:635:12: note: suggested alternative: '_S_out'
  std::swap(_M_gcount, __rhs._M_gcount);
            ^~~~~~~~~
            _S_out
/usr/include/c++/7/istream: In instantiation of 'class std::basic_istream<char>':
/usr/include/c++/7/istream:647:24:   required from here
/usr/include/c++/7/istream:451:14: error: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::ignore() [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]' conflicts with a previous declaration
       ignore(streamsize __n, int_type __delim);
              ^~~~~~~~~~
/usr/include/c++/7/istream:451:14: note: previous declaration 'std::basic_istream<char>::__istream_type& std::basic_istream<char>::ignore'
/usr/include/c++/7/istream: At global scope:
/usr/include/c++/7/istream:648:29: error: 'streamsize' has not been declared
     getline(char_type* __s, streamsize __n, char_type __delim);
                             ^~~~~~~~~~
/usr/include/c++/7/istream:653:12: error: 'std::basic_istream<char>& std::basic_istream<char>::ignore' is not a static data member of 'class std::basic_istream<char>'
     ignore(streamsize __n);
            ^~~~~~~~~~
/usr/include/c++/7/istream:653:12: error: 'streamsize' was not declared in this scope
/usr/include/c++/7/istream:653:12: note: suggested alternative: 'streampos'
     ignore(streamsize __n);
            ^~~~~~~~~~
            streampos
/usr/include/c++/7/istream:658:12: error: 'std::basic_istream<char>& std::basic_istream<char>::ignore' is not a static data member of 'class std::basic_istream<char>'
     ignore(streamsize __n, int_type __delim);
            ^~~~~~~~~~
/usr/include/c++/7/istream:658:12: error: 'streamsize' was not declared in this scope
/usr/include/c++/7/istream:658:12: note: suggested alternative: 'streampos'
     ignore(streamsize __n, int_type __delim);
            ^~~~~~~~~~
            streampos
/usr/include/c++/7/istream:658:37: error: expected primary-expression before '__delim'
     ignore(streamsize __n, int_type __delim);
                                     ^~~~~~~
/usr/include/c++/7/istream:658:44: error: expression list treated as compound expression in initializer [-fpermissive]
     ignore(streamsize __n, int_type __delim);
                                            ^
/usr/include/c++/7/istream: In instantiation of 'class std::basic_istream<wchar_t>':
/usr/include/c++/7/istream:663:27:   required from here
/usr/include/c++/7/istream:451:14: error: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::ignore() [with _CharT = wchar_t; _Traits = std::char_traits<wchar_t>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<wchar_t>]' conflicts with a previous declaration
       ignore(streamsize __n, int_type __delim);
              ^~~~~~~~~~
/usr/include/c++/7/istream:451:14: note: previous declaration 'std::basic_istream<wchar_t>::__istream_type& std::basic_istream<wchar_t>::ignore'
/usr/include/c++/7/istream:664:29: error: 'streamsize' has not been declared
     getline(char_type* __s, streamsize __n, char_type __delim);
                             ^~~~~~~~~~
/usr/include/c++/7/istream:669:12: error: 'std::basic_istream<wchar_t>& std::basic_istream<wchar_t>::ignore' is not a static data member of 'class std::basic_istream<wchar_t>'
     ignore(streamsize __n);
            ^~~~~~~~~~
/usr/include/c++/7/istream:669:12: error: 'streamsize' was not declared in this scope
/usr/include/c++/7/istream:669:12: note: suggested alternative: 'streampos'
     ignore(streamsize __n);
            ^~~~~~~~~~
            streampos
/usr/include/c++/7/istream:674:12: error: 'std::basic_istream<wchar_t>& std::basic_istream<wchar_t>::ignore' is not a static data member of 'class std::basic_istream<wchar_t>'
     ignore(streamsize __n, int_type __delim);
            ^~~~~~~~~~
/usr/include/c++/7/istream:674:12: error: 'streamsize' was not declared in this scope
/usr/include/c++/7/istream:674:12: note: suggested alternative: 'streampos'
     ignore(streamsize __n, int_type __delim);
            ^~~~~~~~~~
            streampos
/usr/include/c++/7/istream:674:37: error: expected primary-expression before '__delim'
     ignore(streamsize __n, int_type __delim);
                                     ^~~~~~~
/usr/include/c++/7/istream:674:44: error: expression list treated as compound expression in initializer [-fpermissive]
     ignore(streamsize __n, int_type __delim);
                                            ^
In file included from /usr/include/c++/7/istream:991:0,
                 from /usr/include/c++/7/iostream:40,
                 from foo.cc:5:
/usr/include/c++/7/bits/istream.tcc: In member function 'std::basic_istream<_CharT, _Traits>::int_type std::basic_istream<_CharT, _Traits>::get()':
/usr/include/c++/7/bits/istream.tcc:248:7: error: '_M_gcount' was not declared in this scope
       _M_gcount = 0;
       ^~~~~~~~~
/usr/include/c++/7/bits/istream.tcc:248:7: note: suggested alternative: '_S_out'
       _M_gcount = 0;
       ^~~~~~~~~
       _S_out
/usr/include/c++/7/bits/istream.tcc: In member function 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::get(std::basic_istream<_CharT, _Traits>::char_type&)':
/usr/include/c++/7/bits/istream.tcc:282:7: error: '_M_gcount' was not declared in this scope
       _M_gcount = 0;
       ^~~~~~~~~
/usr/include/c++/7/bits/istream.tcc:282:7: note: suggested alternative: '_S_out'
       _M_gcount = 0;
       ^~~~~~~~~
       _S_out
/usr/include/c++/7/bits/istream.tcc: At global scope:
/usr/include/c++/7/bits/istream.tcc:317:25: error: 'streamsize' has not been declared
     get(char_type* __s, streamsize __n, char_type __delim)
                         ^~~~~~~~~~
/usr/include/c++/7/bits/istream.tcc: In member function 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::get(std::basic_istream<_CharT, _Traits>::char_type*, int, std::basic_istream<_CharT, _Traits>::char_type)':
/usr/include/c++/7/bits/istream.tcc:319:7: error: '_M_gcount' was not declared in this scope
       _M_gcount = 0;
       ^~~~~~~~~
/usr/include/c++/7/bits/istream.tcc:319:7: note: suggested alternative: '_S_out'
       _M_gcount = 0;
       ^~~~~~~~~
       _S_out
/usr/include/c++/7/bits/istream.tcc: In member function 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::get(std::basic_istream<_CharT, _Traits>::__streambuf_type&, std::basic_istream<_CharT, _Traits>::char_type)':
/usr/include/c++/7/bits/istream.tcc:366:7: error: '_M_gcount' was not declared in this scope
       _M_gcount = 0;
       ^~~~~~~~~
/usr/include/c++/7/bits/istream.tcc:366:7: note: suggested alternative: '_S_out'
       _M_gcount = 0;
       ^~~~~~~~~
       _S_out
/usr/include/c++/7/bits/istream.tcc: At global scope:
/usr/include/c++/7/bits/istream.tcc:408:29: error: 'streamsize' has not been declared
     getline(char_type* __s, streamsize __n, char_type __delim)
                             ^~~~~~~~~~
/usr/include/c++/7/bits/istream.tcc: In member function 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::getline(std::basic_istream<_CharT, _Traits>::char_type*, int, std::basic_istream<_CharT, _Traits>::char_type)':
/usr/include/c++/7/bits/istream.tcc:410:7: error: '_M_gcount' was not declared in this scope
       _M_gcount = 0;
       ^~~~~~~~~
/usr/include/c++/7/bits/istream.tcc:410:7: note: suggested alternative: '_S_out'
       _M_gcount = 0;
       ^~~~~~~~~
       _S_out
/usr/include/c++/7/bits/istream.tcc: In member function 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::ignore()':
/usr/include/c++/7/bits/istream.tcc:470:7: error: '_M_gcount' was not declared in this scope
       _M_gcount = 0;
       ^~~~~~~~~
/usr/include/c++/7/bits/istream.tcc:470:7: note: suggested alternative: '_S_out'
       _M_gcount = 0;
       ^~~~~~~~~
       _S_out
/usr/include/c++/7/bits/istream.tcc: At global scope:
/usr/include/c++/7/bits/istream.tcc:501:12: error: 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::ignore' is not a static data member of 'class std::basic_istream<_CharT, _Traits>'
     ignore(streamsize __n)
            ^~~~~~~~~~
/usr/include/c++/7/bits/istream.tcc:501:12: error: template definition of non-template 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::ignore'
/usr/include/c++/7/bits/istream.tcc:501:12: error: 'streamsize' was not declared in this scope
/usr/include/c++/7/bits/istream.tcc:501:12: note: suggested alternative: 'streambuf'
     ignore(streamsize __n)
            ^~~~~~~~~~
            streambuf
/usr/include/c++/7/bits/istream.tcc:563:12: error: 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::ignore' is not a static data member of 'class std::basic_istream<_CharT, _Traits>'
     ignore(streamsize __n, int_type __delim)
            ^~~~~~~~~~
/usr/include/c++/7/bits/istream.tcc:563:12: error: template definition of non-template 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::ignore'
/usr/include/c++/7/bits/istream.tcc:563:12: error: 'streamsize' was not declared in this scope
/usr/include/c++/7/bits/istream.tcc:563:12: note: suggested alternative: 'streambuf'
     ignore(streamsize __n, int_type __delim)
            ^~~~~~~~~~
            streambuf
/usr/include/c++/7/bits/istream.tcc:563:37: error: expected primary-expression before '__delim'
     ignore(streamsize __n, int_type __delim)
                                     ^~~~~~~
/usr/include/c++/7/bits/istream.tcc: In member function 'std::basic_istream<_CharT, _Traits>::int_type std::basic_istream<_CharT, _Traits>::peek()':
/usr/include/c++/7/bits/istream.tcc:631:7: error: '_M_gcount' was not declared in this scope
       _M_gcount = 0;
       ^~~~~~~~~
/usr/include/c++/7/bits/istream.tcc:631:7: note: suggested alternative: '_S_out'
       _M_gcount = 0;
       ^~~~~~~~~
       _S_out
/usr/include/c++/7/bits/istream.tcc: At global scope:
/usr/include/c++/7/bits/istream.tcc:658:26: error: 'streamsize' has not been declared
     read(char_type* __s, streamsize __n)
                          ^~~~~~~~~~
/usr/include/c++/7/bits/istream.tcc: In member function 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::read(std::basic_istream<_CharT, _Traits>::char_type*, int)':
/usr/include/c++/7/bits/istream.tcc:660:7: error: '_M_gcount' was not declared in this scope
       _M_gcount = 0;
       ^~~~~~~~~
/usr/include/c++/7/bits/istream.tcc:660:7: note: suggested alternative: '_S_out'
       _M_gcount = 0;
       ^~~~~~~~~
       _S_out
/usr/include/c++/7/bits/istream.tcc: At global scope:
/usr/include/c++/7/bits/istream.tcc:685:5: error: 'streamsize' does not name a type; did you mean 'streambuf'?
     streamsize
     ^~~~~~~~~~
     streambuf
/usr/include/c++/7/bits/istream.tcc: In member function 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::putback(std::basic_istream<_CharT, _Traits>::char_type)':
/usr/include/c++/7/bits/istream.tcc:723:7: error: '_M_gcount' was not declared in this scope
       _M_gcount = 0;
       ^~~~~~~~~
/usr/include/c++/7/bits/istream.tcc:723:7: note: suggested alternative: '_S_out'
       _M_gcount = 0;
       ^~~~~~~~~
       _S_out
/usr/include/c++/7/bits/istream.tcc: In member function 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::unget()':
/usr/include/c++/7/bits/istream.tcc:758:7: error: '_M_gcount' was not declared in this scope
       _M_gcount = 0;
       ^~~~~~~~~
/usr/include/c++/7/bits/istream.tcc:758:7: note: suggested alternative: '_S_out'
       _M_gcount = 0;
       ^~~~~~~~~
       _S_out
/usr/include/c++/7/bits/istream.tcc: In function 'std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, _CharT2*)':
/usr/include/c++/7/bits/istream.tcc:971:7: error: 'streamsize' was not declared in this scope
       streamsize __extracted = 0;
       ^~~~~~~~~~
/usr/include/c++/7/bits/istream.tcc:971:7: note: suggested alternative: 'streambuf'
       streamsize __extracted = 0;
       ^~~~~~~~~~
       streambuf
/usr/include/c++/7/bits/istream.tcc:979:19: error: expected ';' before '__num'
        streamsize __num = __in.width();
                   ^~~~~
/usr/include/c++/7/bits/istream.tcc:980:12: error: '__num' was not declared in this scope
        if (__num <= 0)
            ^~~~~
/usr/include/c++/7/bits/istream.tcc:980:12: note: suggested alternative: '__wur'
        if (__num <= 0)
            ^~~~~
            __wur
/usr/include/c++/7/bits/istream.tcc:981:49: error: type/value mismatch at argument 1 in template parameter list for 'template<class _Value> struct __gnu_cxx::__numeric_traits'
   __num = __gnu_cxx::__numeric_traits<streamsize>::__max;
                                                 ^
/usr/include/c++/7/bits/istream.tcc:981:49: note:   expected a type, got 'streamsize'
/usr/include/c++/7/bits/istream.tcc:989:15: error: '__extracted' was not declared in this scope
        while (__extracted < __num - 1
               ^~~~~~~~~~~
/usr/include/c++/7/bits/istream.tcc:989:15: note: suggested alternative: '__traitor'
        while (__extracted < __num - 1
               ^~~~~~~~~~~
               __traitor
/usr/include/c++/7/bits/istream.tcc:989:29: error: '__num' was not declared in this scope
        while (__extracted < __num - 1
                             ^~~~~
/usr/include/c++/7/bits/istream.tcc:989:29: note: suggested alternative: '__wur'
        while (__extracted < __num - 1
                             ^~~~~
                             __wur
/usr/include/c++/7/bits/istream.tcc:1014:12: error: '__extracted' was not declared in this scope
       if (!__extracted)
            ^~~~~~~~~~~
/usr/include/c++/7/bits/istream.tcc:1014:12: note: suggested alternative: '__traitor'
       if (!__extracted)
            ^~~~~~~~~~~
            __traitor
In file included from /usr/include/c++/7/string:52:0,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:5:
/usr/include/c++/7/bits/basic_string.h: In instantiation of 'std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::basic_string(std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&&) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]':
/usr/include/c++/7/system_error:189:40:   required from here
/usr/include/c++/7/bits/basic_string.h:542:24: error: 'class std::__cxx11::basic_string<char>' has no member named '_M_allocated_capacity'; did you mean '_S_local_capacity'?
      _M_capacity(__str._M_allocated_capacity);
                  ~~~~~~^~~~~~~~~~~~~~~~~~~~~
                  _S_local_capacity
/usr/include/c++/7/bits/basic_string.h:542:17: error: '_M_capacity' was not declared in this scope
      _M_capacity(__str._M_allocated_capacity);
      ~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/7/bits/basic_string.h:548:11: error: '_M_length' was not declared in this scope
  _M_length(__str.length());
  ~~~~~~~~~^~~~~~~~~~~~~~~~
/usr/include/c++/7/bits/basic_string.h: In instantiation of 'std::__cxx11::basic_string<_CharT, _Traits, _Alloc> std::operator+(std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&&, std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&&) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]':
/usr/include/c++/7/system_error:351:50:   required from here
/usr/include/c++/7/bits/basic_string.h:5968:33: error: 'class std::__cxx11::basic_string<char>' has no member named 'size'
       const auto __size = __lhs.size() + __rhs.size();
                           ~~~~~~^~~~
/usr/include/c++/7/bits/basic_string.h:5968:48: error: 'class std::__cxx11::basic_string<char>' has no member named 'size'
       const auto __size = __lhs.size() + __rhs.size();
                                          ~~~~~~^~~~
/usr/include/c++/7/bits/basic_string.h:5969:43: error: 'class std::__cxx11::basic_string<char>' has no member named 'capacity'
       const bool __cond = (__size > __lhs.capacity()
                                     ~~~~~~^~~~~~~~
/usr/include/c++/7/bits/basic_string.h:5970:26: error: 'class std::__cxx11::basic_string<char>' has no member named 'capacity'
       && __size <= __rhs.capacity());
                    ~~~~~~^~~~~~~~
/usr/include/c++/7/bits/basic_string.h:5971:32: error: no matching function for call to 'std::__cxx11::basic_string<char>::insert(int, std::__cxx11::basic_string<char>&)'
       return __cond ? std::move(__rhs.insert(0, __lhs))
                       ~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/7/bits/basic_string.h:1567:9: note: candidate: template<class _InputIterator, class> std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::iterator std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::insert(std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::const_iterator, _InputIterator, _InputIterator) [with _InputIterator = _InputIterator; <template-parameter-2-2> = <template-parameter-1-2>; _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]
         insert(const_iterator __p, _InputIterator __beg, _InputIterator __end)
         ^~~~~~
/usr/include/c++/7/bits/basic_string.h:1567:9: note:   template argument deduction/substitution failed:
/usr/include/c++/7/bits/basic_string.h:5971:32: note:   candidate expects 3 arguments, 2 provided
       return __cond ? std::move(__rhs.insert(0, __lhs))
                       ~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/7/bits/basic_string.h:1601:7: note: candidate: void std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::insert(std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::iterator, std::initializer_list<_Tp>) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>; std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::iterator = __gnu_cxx::__normal_iterator<char*, std::__cxx11::basic_string<char> >; typename __gnu_cxx::__alloc_traits<typename __gnu_cxx::__alloc_traits<_Alloc>::rebind<_CharT>::other>::pointer = char*]
       insert(iterator __p, initializer_list<_CharT> __l)
       ^~~~~~
/usr/include/c++/7/bits/basic_string.h:1601:7: note:   no known conversion for argument 1 from 'int' to 'std::__cxx11::basic_string<char>::iterator {aka __gnu_cxx::__normal_iterator<char*, std::__cxx11::basic_string<char> >}'
/usr/include/c++/7/bits/basic_string.h:1728:7: note: candidate: std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::iterator std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::insert(std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::__const_iterator, _CharT) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>; std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::iterator = __gnu_cxx::__normal_iterator<char*, std::__cxx11::basic_string<char> >; typename __gnu_cxx::__alloc_traits<typename __gnu_cxx::__alloc_traits<_Alloc>::rebind<_CharT>::other>::pointer = char*; std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::__const_iterator = __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >; typename __gnu_cxx::__alloc_traits<typename __gnu_cxx::__alloc_traits<_Alloc>::rebind<_CharT>::other>::const_pointer = const char*]
       insert(__const_iterator __p, _CharT __c)
       ^~~~~~
/usr/include/c++/7/bits/basic_string.h:1728:7: note:   no known conversion for argument 1 from 'int' to 'std::__cxx11::basic_string<char>::__const_iterator {aka __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >}'
/usr/include/c++/7/bits/basic_string.h: In instantiation of 'std::__cxx11::basic_string<_CharT, _Traits, _Alloc> std::operator+(const _CharT*, std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&&) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]':
/usr/include/c++/7/system_error:354:51:   required from here
/usr/include/c++/7/bits/basic_string.h:5979:23: error: no matching function for call to 'std::__cxx11::basic_string<char>::insert(int, const char*&)'
     { return std::move(__rhs.insert(0, __lhs)); }
              ~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/7/bits/basic_string.h:1567:9: note: candidate: template<class _InputIterator, class> std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::iterator std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::insert(std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::const_iterator, _InputIterator, _InputIterator) [with _InputIterator = _InputIterator; <template-parameter-2-2> = <template-parameter-1-2>; _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]
         insert(const_iterator __p, _InputIterator __beg, _InputIterator __end)
         ^~~~~~
/usr/include/c++/7/bits/basic_string.h:1567:9: note:   template argument deduction/substitution failed:
/usr/include/c++/7/bits/basic_string.h:5979:23: note:   candidate expects 3 arguments, 2 provided
     { return std::move(__rhs.insert(0, __lhs)); }
              ~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/7/bits/basic_string.h:1601:7: note: candidate: void std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::insert(std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::iterator, std::initializer_list<_Tp>) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>; std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::iterator = __gnu_cxx::__normal_iterator<char*, std::__cxx11::basic_string<char> >; typename __gnu_cxx::__alloc_traits<typename __gnu_cxx::__alloc_traits<_Alloc>::rebind<_CharT>::other>::pointer = char*]
       insert(iterator __p, initializer_list<_CharT> __l)
       ^~~~~~
/usr/include/c++/7/bits/basic_string.h:1601:7: note:   no known conversion for argument 1 from 'int' to 'std::__cxx11::basic_string<char>::iterator {aka __gnu_cxx::__normal_iterator<char*, std::__cxx11::basic_string<char> >}'
/usr/include/c++/7/bits/basic_string.h:1728:7: note: candidate: std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::iterator std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::insert(std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::__const_iterator, _CharT) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>; std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::iterator = __gnu_cxx::__normal_iterator<char*, std::__cxx11::basic_string<char> >; typename __gnu_cxx::__alloc_traits<typename __gnu_cxx::__alloc_traits<_Alloc>::rebind<_CharT>::other>::pointer = char*; std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::__const_iterator = __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >; typename __gnu_cxx::__alloc_traits<typename __gnu_cxx::__alloc_traits<_Alloc>::rebind<_CharT>::other>::const_pointer = const char*]
       insert(__const_iterator __p, _CharT __c)
       ^~~~~~
/usr/include/c++/7/bits/basic_string.h:1728:7: note:   no known conversion for argument 1 from 'int' to 'std::__cxx11::basic_string<char>::__const_iterator {aka __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >}'
/usr/include/c++/7/bits/basic_string.h: In instantiation of 'void std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::_M_dispose() [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]':
/usr/include/c++/7/bits/basic_string.h:647:19:   required from 'std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::~basic_string() [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]'
/usr/include/c++/7/system_error:189:40:   required from here
/usr/include/c++/7/bits/basic_string.h:221:15: error: using invalid field 'std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::<unnamed union>::_M_allocated_capacity'
    _M_destroy(_M_allocated_capacity);
               ^~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/7/bits/basic_string.h:221:14: error: '_M_destroy' was not declared in this scope
    _M_destroy(_M_allocated_capacity);
    ~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/7/bits/basic_string.h:221:14: note: suggested alternative: '_M_data'
    _M_destroy(_M_allocated_capacity);
    ~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~
    _M_data
/usr/include/c++/7/bits/basic_string.h: In instantiation of 'std::__cxx11::basic_string<_CharT, _Traits, _Alloc>& std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::append(const _CharT*) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]':
/usr/include/c++/7/bits/basic_string.h:5929:7:   required from 'std::__cxx11::basic_string<_CharT, _Traits, _Alloc> std::operator+(const std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&, const _CharT*) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]'
/usr/include/c++/7/system_error:351:30:   required from here
/usr/include/c++/7/bits/basic_string.h:1257:17: error: '_M_check_length' was not declared in this scope
  _M_check_length(size_type(0), __n, "basic_string::append");
  ~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/7/bits/basic_string.h:1257:17: note: suggested alternative: '__socklen_t'
  _M_check_length(size_type(0), __n, "basic_string::append");
  ~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  __socklen_t
/usr/include/c++/7/bits/basic_string.h:1258:18: error: '_M_append' was not declared in this scope
  return _M_append(__s, __n);
         ~~~~~~~~~^~~~~~~~~~
/usr/include/c++/7/bits/basic_string.h:1258:18: note: suggested alternative: 'append'
  return _M_append(__s, __n);
         ~~~~~~~~~^~~~~~~~~~
         append
foo.cc: In function 'int main()':
foo.cc:9:13: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  int n;scanf("%d",&n);
        ~~~~~^~~~~~~~~

自豪的采用HydroJudge(https://github.com/hydro-dev/Hydro)进行评测。