src/c/_cffi_backend.c: In function ‘_my_PyLong_AsUnsignedLongLong’:
      src/c/_cffi_backend.c:868:17: error: implicit declaration of function ‘_PyLong_Sign’ [-Werror=implicit-function-declaration]
        868 |             if (_PyLong_Sign(ob) < 0)
            |                 ^~~~~~~~~~~~
      src/c/_cffi_backend.c: In function ‘cdata_hash’:
      src/c/_cffi_backend.c:2449:12: error: implicit declaration of function ‘_Py_HashPointer’ [-Werror=implicit-function-declaration]
       2449 |     return _Py_HashPointer(((CDataObject *)v)->c_data);
            |            ^~~~~~~~~~~~~~~
      src/c/_cffi_backend.c: In function ‘b_do_dlopen’:
      src/c/_cffi_backend.c:4532:22: warning: ‘Py_FileSystemDefaultEncoding’ is deprecated [-Wdeprecated-declarations]
       4532 |                      Py_FileSystemDefaultEncoding, &filename_or_null, &flags))
            |                      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
      In file included from /usr/include/python3.13/Python.h:77,
                       from src/c/_cffi_backend.c:2:
      /usr/include/python3.13/fileobject.h:22:46: note: declared here
         22 | Py_DEPRECATED(3.12) PyAPI_DATA(const char *) Py_FileSystemDefaultEncoding;
            |                                              ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
      src/c/_cffi_backend.c: In function ‘_my_PyErr_WriteUnraisable’:
      src/c/_cffi_backend.c:6121:9: error: implicit declaration of function ‘_PyErr_WriteUnraisableMsg’; did you mean ‘PyErr_WriteUnraisable’? [-Werror=implicit-function-declaration]
       6121 |         _PyErr_WriteUnraisableMsg(PyText_AS_UTF8(s), NULL);
            |         ^~~~~~~~~~~~~~~~~~~~~~~~~
            |         PyErr_WriteUnraisable
      In file included from src/c/cffi1_module.c:15,
                       from src/c/_cffi_backend.c:7976:
      src/c/ffi_obj.c: In function ‘ffi_getctype’:
      src/c/ffi_obj.c:635:36: error: implicit declaration of function ‘isspace’ [-Werror=implicit-function-declaration]
        635 |     while (replace_with[0] != 0 && isspace(replace_with[0]))
            |                                    ^~~~~~~
      src/c/ffi_obj.c:1:1: note: include ‘<ctype.h>’ or provide a declaration of ‘isspace’
        +++ |+#include <ctype.h>
          1 |