In file included from /usr/include/c++/7/cassert:43:0,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:33,
                 from /in/foo.cc:2:
/usr/include/x86_64-linux-gnu/c++/7/bits/c++config.h:229:1: error: expected unqualified-id before 'namespace'
 namespace std
 ^~~~~~~~~
In file included from /usr/include/c++/7/cmath:43:0,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:41,
                 from /in/foo.cc:2:
/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)
                          ^~~~~~~~~
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/istream:38,
                 from /usr/include/c++/7/sstream:38,
                 from /usr/include/c++/7/complex:45,
                 from /usr/include/c++/7/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:52,
                 from /in/foo.cc:2:
/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/stdlib.h:32:0,
                 from /usr/include/c++/7/bits/std_abs.h:38,
                 from /usr/include/c++/7/cmath:47,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:41,
                 from /in/foo.cc:2:
/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/istream:38,
                 from /usr/include/c++/7/sstream:38,
                 from /usr/include/c++/7/complex:45,
                 from /usr/include/c++/7/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:52,
                 from /in/foo.cc:2:
/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/stdlib.h:32:0,
                 from /usr/include/c++/7/bits/std_abs.h:38,
                 from /usr/include/c++/7/cmath:47,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:41,
                 from /in/foo.cc:2:
/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/istream:38,
                 from /usr/include/c++/7/sstream:38,
                 from /usr/include/c++/7/complex:45,
                 from /usr/include/c++/7/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:52,
                 from /in/foo.cc:2:
/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/stdlib.h:32:0,
                 from /usr/include/c++/7/bits/std_abs.h:38,
                 from /usr/include/c++/7/cmath:47,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:41,
                 from /in/foo.cc:2:
/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/istream:38,
                 from /usr/include/c++/7/sstream:38,
                 from /usr/include/c++/7/complex:45,
                 from /usr/include/c++/7/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:52,
                 from /in/foo.cc:2:
/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/stdlib.h:32:0,
                 from /usr/include/c++/7/bits/std_abs.h:38,
                 from /usr/include/c++/7/cmath:47,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:41,
                 from /in/foo.cc:2:
/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/istream:38,
                 from /usr/include/c++/7/sstream:38,
                 from /usr/include/c++/7/complex:45,
                 from /usr/include/c++/7/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:52,
                 from /in/foo.cc:2:
/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/stdlib.h:32:0,
                 from /usr/include/c++/7/bits/std_abs.h:38,
                 from /usr/include/c++/7/cmath:47,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:41,
                 from /in/foo.cc:2:
/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/istream:38,
                 from /usr/include/c++/7/sstream:38,
                 from /usr/include/c++/7/complex:45,
                 from /usr/include/c++/7/ccomplex:39,
                 from /usr/include/x