errors from clang

clang -I /usr/local/Cellar/libtommath/1.2.0/include -I /Users/shadow/git/cppcoro/include -I /Library/Developer/CommandLineTools/usr/include/c++/v1 pi.c

In file included from pi.c:1:
In file included from /Library/Developer/CommandLineTools/usr/include/c++/v1/array:108:
In file included from /Library/Developer/CommandLineTools/usr/include/c++/v1/__tuple:15:
In file included from /Library/Developer/CommandLineTools/usr/include/c++/v1/cstddef:45:
/Library/Developer/CommandLineTools/usr/include/c++/v1/__nullptr:55:1: error: unknown type name 'namespace'
namespace std
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/__nullptr:55:14: error: expected ';' after top level declarator
namespace std
             ^
In file included from pi.c:1:
In file included from /Library/Developer/CommandLineTools/usr/include/c++/v1/array:108:
In file included from /Library/Developer/CommandLineTools/usr/include/c++/v1/__tuple:15:
/Library/Developer/CommandLineTools/usr/include/c++/v1/cstddef:50:7: error: expected ';' after top level declarator
using ::size_t;
      ^
/Library/Developer/CommandLineTools/usr/include/c++/v1/cstddef:50:8: error: expected identifier or '('
using ::size_t;
       ^
/Library/Developer/CommandLineTools/usr/include/c++/v1/cstddef:55:7: error: expected ';' after top level declarator
using ::max_align_t;
      ^
/Library/Developer/CommandLineTools/usr/include/c++/v1/cstddef:55:8: error: expected identifier or '('
using ::max_align_t;
       ^
/Library/Developer/CommandLineTools/usr/include/c++/v1/cstddef:60:1: error: unknown type name '_LIBCPP_END_NAMESPACE_STD'
_LIBCPP_END_NAMESPACE_STD
^
In file included from pi.c:1:
In file included from /Library/Developer/CommandLineTools/usr/include/c++/v1/array:108:
In file included from /Library/Developer/CommandLineTools/usr/include/c++/v1/__tuple:16:
/Library/Developer/CommandLineTools/usr/include/c++/v1/type_traits:408:28: error: expected ';' after top level declarator
_LIBCPP_BEGIN_NAMESPACE_STD
                           ^
/Library/Developer/CommandLineTools/usr/include/c++/v1/type_traits:411:1: error: unknown type name 'template'
template <class _Tp> class _LIBCPP_TEMPLATE_VIS reference_wrapper;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/type_traits:411:10: error: expected identifier or '('
template <class _Tp> class _LIBCPP_TEMPLATE_VIS reference_wrapper;
         ^
/Library/Developer/CommandLineTools/usr/include/c++/v1/type_traits:412:1: error: unknown type name 'template'
template <class _Tp> struct _LIBCPP_TEMPLATE_VIS hash;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/type_traits:412:10: error: expected identifier or '('
template <class _Tp> struct _LIBCPP_TEMPLATE_VIS hash;
         ^
/Library/Developer/CommandLineTools/usr/include/c++/v1/type_traits:414:1: error: unknown type name 'template'
template <class>
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/type_traits:414:10: error: expected identifier or '('
template <class>
         ^
/Library/Developer/CommandLineTools/usr/include/c++/v1/type_traits:417:1: error: unknown type name 'template'
template <class _Tp>
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/type_traits:417:10: error: expected identifier or '('
template <class _Tp>
         ^
/Library/Developer/CommandLineTools/usr/include/c++/v1/type_traits:420:1: error: unknown type name 'template'
template <class _Tp, bool>
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/type_traits:420:10: error: expected identifier or '('
template <class _Tp, bool>
         ^
/Library/Developer/CommandLineTools/usr/include/c++/v1/type_traits:423:1: error: unknown type name 'template'
template <bool _Bp, class _If, class _Then>
^
fatal error: too many errors emitted, stopping now [-ferror-limit=]
20 errors generated.