/usr/src/Python-3.6.0/Modules/_ctypes/libffi/src/x86/ffi64.c: In function 'classify_argument':
/usr/src/Python-3.6.0/Modules/_ctypes/libffi/src/x86/ffi64.c:195:18: warning: suggest braces around empty body in an 'else' statement [-Wempty-body]
    FFI_ASSERT (0);
                  ^
/usr/src/Python-3.6.0/Modules/_ctypes/libffi/src/x86/ffi64.c:224:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (i = 0; i < words; i++)
                ^
/usr/src/Python-3.6.0/Modules/_ctypes/libffi/src/x86/ffi64.c:245:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
      for (i = 0; i < num; i++)
                    ^
/usr/src/Python-3.6.0/Modules/_ctypes/libffi/src/x86/ffi64.c:264:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
      for (i = 1; i < words; i++)
                    ^
/usr/src/Python-3.6.0/Modules/_ctypes/libffi/src/x86/ffi64.c:270:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (i = 0; i < words; i++)
                ^
/usr/src/Python-3.6.0/Modules/_ctypes/libffi/src/x86/ffi64.c: In function 'examine_argument':
/usr/src/Python-3.6.0/Modules/_ctypes/libffi/src/x86/ffi64.c:323:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (i = 0; i < n; ++i)
                 ^
/usr/src/Python-3.6.0/Modules/_ctypes/libffi/src/x86/ffi64.c: In function 'ffi_call':
/usr/src/Python-3.6.0/Modules/_ctypes/libffi/src/x86/ffi64.c:484:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for (j = 0; j < n; j++, a += 8, size -= 8)
                  ^
/usr/src/Python-3.6.0/Modules/_ctypes/libffi/src/x86/ffi64.c: In function 'ffi_closure_unix64_inner':
/usr/src/Python-3.6.0/Modules/_ctypes/libffi/src/x86/ffi64.c:659:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for (j = 0; j < n; j++, a += 8)
                  ^