https://bugs.python.org/issue41100
https://github.com/python/cpython/pull/21249
https://github.com/python/cpython/pull/21268
https://github.com/python/cpython/pull/21564

--- configure.orig	2020-04-20 07:13:39.000000000 +1000
+++ configure	2020-09-10 19:51:43.000000000 +1000
@@ -8474,6 +8474,9 @@
     	ppc)
     		MACOSX_DEFAULT_ARCH="ppc64"
     		;;
+    	arm64)
+    		MACOSX_DEFAULT_ARCH="arm64"
+    		;;
     	*)
     		as_fn_error $? "Unexpected output of 'arch' on OSX" "$LINENO" 5
     		;;
--- Mac/Tools/pythonw.c.orig	2020-04-20 07:13:39.000000000 +1000
+++ Mac/Tools/pythonw.c	2020-09-10 20:22:45.000000000 +1000
@@ -114,6 +114,9 @@
 #elif defined(__x86_64__)
     cpu_types[0] = CPU_TYPE_X86_64;
 
+#elif defined(__arm64__)
+    cpu_types[0] = CPU_TYPE_ARM64;
+
 #elif defined(__ppc__)
     cpu_types[0] = CPU_TYPE_POWERPC;
 #elif defined(__i386__)
--- Lib/test/test_platform.py.orig	2020-04-20 07:13:39.000000000 +1000
+++ Lib/test/test_platform.py	2020-09-10 20:26:40.000000000 +1000
@@ -220,7 +220,7 @@
             self.assertEqual(res[1], ('', '', ''))
 
             if sys.byteorder == 'little':
-                self.assertIn(res[2], ('i386', 'x86_64'))
+                self.assertIn(res[2], ('i386', 'x86_64', 'arm64'))
             else:
                 self.assertEqual(res[2], 'PowerPC')
 
--- Lib/_osx_support.py.orig	2020-04-20 07:13:39.000000000 +1000
+++ Lib/_osx_support.py	2020-09-10 20:38:30.000000000 +1000
@@ -470,6 +470,8 @@
 
             if len(archs) == 1:
                 machine = archs[0]
+            elif archs == ('arm64', 'x86_64'):
+                machine = 'universal2'
             elif archs == ('i386', 'ppc'):
                 machine = 'fat'
             elif archs == ('i386', 'x86_64'):
@@ -484,6 +486,10 @@
                 raise ValueError(
                    "Don't know machine value for archs=%r" % (archs,))
 
+        elif machine == 'arm':
+            # No 32-bit arm support on macOS
+            machine = 'arm64'
+
         elif machine == 'i386':
             # On OSX the machine type returned by uname is always the
             # 32-bit variant, even if the executable architecture is
--- Lib/test/test_unicode.py.orig	2020-04-20 07:13:39.000000000 +1000
+++ Lib/test/test_unicode.py	2020-09-18 01:42:41.000000000 +1000
@@ -1676,6 +1676,7 @@
     def test_from_format(self):
         test_support.import_module('ctypes')
         from ctypes import (
+            c_char_p,
             pythonapi, py_object, sizeof,
             c_int, c_long, c_longlong, c_ssize_t,
             c_uint, c_ulong, c_ulonglong, c_size_t, c_void_p)
@@ -1684,6 +1685,7 @@
         else:
             name = "PyUnicodeUCS4_FromFormat"
         _PyUnicode_FromFormat = getattr(pythonapi, name)
+        _PyUnicode_FromFormat.argtypes = (c_char_p,)
         _PyUnicode_FromFormat.restype = py_object
 
         def PyUnicode_FromFormat(format, *args):
--- Modules/_ctypes/callbacks.c.orig	2020-04-20 07:13:39.000000000 +1000
+++ Modules/_ctypes/callbacks.c	2020-09-18 02:26:42.000000000 +1000
@@ -24,7 +24,7 @@ CThunkObject_dealloc(PyObject *_self)
     Py_XDECREF(self->callable);
     Py_XDECREF(self->restype);
     if (self->pcl_write)
-        ffi_closure_free(self->pcl_write);
+        Py_ffi_closure_free(self->pcl_write);
     PyObject_GC_Del(self);
 }
 
@@ -426,7 +426,7 @@ CThunkObject *_ctypes_alloc_callback(PyO
 
     assert(CThunk_CheckExact(p));
 
-    p->pcl_write = ffi_closure_alloc(sizeof(ffi_closure),
+    p->pcl_write = Py_ffi_closure_alloc(sizeof(ffi_closure),
 				     &p->pcl_exec);
     if (p->pcl_write == NULL) {
         PyErr_NoMemory();
@@ -473,12 +473,15 @@ CThunkObject *_ctypes_alloc_callback(PyO
                      "ffi_prep_cif failed with %d", result);
         goto error;
     }
-#if defined(X86_DARWIN) || defined(POWERPC_DARWIN)
-    result = ffi_prep_closure(p->pcl_write, &p->cif, closure_fcn, p);
-#else
+#if HAVE_FFI_PREP_CLOSURE_LOC
     result = ffi_prep_closure_loc(p->pcl_write, &p->cif, closure_fcn,
 				  p,
 				  p->pcl_exec);
+#elif defined(__APPLE__) && defined(__arm64__)
+    PyErr_Format(PyExc_NotImplementedError, "ffi_prep_closure_loc() is missing");
+    goto error;
+#else
+    result = ffi_prep_closure(p->pcl_write, &p->cif, closure_fcn, p);
 #endif
     if (result != FFI_OK) {
         PyErr_Format(PyExc_RuntimeError,
--- Modules/_ctypes/callproc.c.orig	2020-04-20 07:13:39.000000000 +1000
+++ Modules/_ctypes/callproc.c	2020-09-21 06:08:56.000000000 +1000
@@ -773,7 +773,8 @@ static int _call_function_pointer(int fl
                                   ffi_type **atypes,
                                   ffi_type *restype,
                                   void *resmem,
-                                  int argcount)
+                                  int argcount,
+                                  int argtypecount)
 {
 #ifdef WITH_THREAD
     PyThreadState *_save = NULL; /* For Py_BLOCK_THREADS and Py_UNBLOCK_THREADS */
@@ -801,6 +802,37 @@ static int _call_function_pointer(int fl
     if ((flags & FUNCFLAG_CDECL) == 0)
         cc = FFI_STDCALL;
 #endif
+
+    /* Even on Apple-arm64 the calling convention for variadic functions conincides
+    * with the standard calling convention in the case that the function called
+    * only with its fixed arguments.   Thus, we do not need a special flag to be
+    * set on variadic functions.   We treat a function as variadic if it is called
+    * with a nonzero number of variadic arguments */
+    int is_variadic = (argtypecount != 0 && argcount > argtypecount);
+    (void) is_variadic;
+
+#if defined(__APPLE__) && defined(__arm64__) && !defined(HAVE_FFI_PREP_CIF_VAR)
+    if (is_variadic) {
+        PyErr_SetString(PyExc_NotImplementedError, "ffi_prep_cif_var() is missing");
+        return -1;
+    }
+#endif
+
+#if HAVE_FFI_PREP_CIF_VAR
+    if (is_variadic) {
+        if (FFI_OK != ffi_prep_cif_var(&cif,
+                                        cc,
+                                        argtypecount,
+                                        argcount,
+                                        restype,
+                                        atypes)) {
+            PyErr_SetString(PyExc_RuntimeError,
+                            "ffi_prep_cif_var failed");
+            return -1;
+        }
+    } else
+ #endif
+    {
     if (FFI_OK != ffi_prep_cif(&cif,
                                cc,
                                argcount,
@@ -810,6 +842,7 @@ static int _call_function_pointer(int fl
                         "ffi_prep_cif failed");
         return -1;
     }
+    }
 
     if (flags & (FUNCFLAG_USE_ERRNO | FUNCFLAG_USE_LASTERROR)) {
         error_object = _ctypes_get_errobj(&space);
@@ -1183,6 +1216,9 @@ PyObject *_ctypes_callproc(PPROC pProc,
                                      rtype, resbuf,
                                      Py_SAFE_DOWNCAST(argcount,
                                                       Py_ssize_t,
+                                                      int),
+                                     Py_SAFE_DOWNCAST(argtype_count,
+                                                      Py_ssize_t,
                                                       int)))
         goto cleanup;
 
--- Modules/_ctypes/ctypes.h.orig	2020-04-20 07:13:39.000000000 +1000
+++ Modules/_ctypes/ctypes.h	2020-09-21 06:14:07.000000000 +1000
@@ -481,6 +481,13 @@ static void capsule_destructor_ ## name(
 
 #endif /* PY_VERSION_HEX >= 0x020700A4 */
 
+#if USING_MALLOC_CLOSURE_DOT_C
+void Py_ffi_closure_free(void *p);
+void *Py_ffi_closure_alloc(size_t size, void** codeloc);
+#else
+#define Py_ffi_closure_free ffi_closure_free
+#define Py_ffi_closure_alloc ffi_closure_alloc
+#endif
 
 /*
  Local Variables:
--- Modules/_ctypes/malloc_closure.c.orig	2020-04-20 07:13:39.000000000 +1000
+++ Modules/_ctypes/malloc_closure.c	2020-09-21 06:22:52.000000000 +1000
@@ -89,16 +89,24 @@ static void more_core(void)
 /******************************************************************/
 
 /* put the item back into the free list */
-void ffi_closure_free(void *p)
+void Py_ffi_closure_free(void *p)
 {
+#if HAVE_FFI_CLOSURE_ALLOC
+    ffi_closure_free(p);
+    return;
+#else
     ITEM *item = (ITEM *)p;
     item->next = free_list;
     free_list = item;
+#endif
 }
 
 /* return one item from the free list, allocating more if needed */
-void *ffi_closure_alloc(size_t ignored, void** codeloc)
+void *Py_ffi_closure_alloc(size_t size, void** codeloc)
 {
+#if HAVE_FFI_CLOSURE_ALLOC
+    return ffi_closure_alloc(size, codeloc);
+#else
     ITEM *item;
     if (!free_list)
         more_core();
@@ -108,4 +116,5 @@ void *ffi_closure_alloc(size_t ignored, 
     free_list = item->next;
     *codeloc = (void *)item;
     return (void *)item;
+#endif
 }
--- setup.py.orig	2020-04-20 07:13:39.000000000 +1000
+++ setup.py	2020-09-21 07:32:43.000000000 +1000
@@ -16,6 +16,7 @@
 from distutils.command.install import install
 from distutils.command.install_lib import install_lib
 from distutils.spawn import find_executable
+import distutils.command.config
 
 cross_compiling = "_PYTHON_HOST_PLATFORM" in os.environ
 
@@ -2129,6 +2130,7 @@
 
         if host_platform == 'darwin':
             sources.append('_ctypes/malloc_closure.c')
+            extra_compile_args.append('-DUSING_MALLOC_CLOSURE_DOT_C=1')
             sources.append('_ctypes/darwin/dlfcn_simple.c')
             extra_compile_args.append('-DMACOSX')
             include_dirs.append('_ctypes/darwin')
@@ -2191,6 +2193,16 @@
                     break
 
         if ffi_inc and ffi_lib:
+            config = distutils.command.config.config(self.distribution)
+            config._check_compiler()
+            if any(cc in config.compiler.compiler_so for cc in ('gcc', 'clang')):
+                config.compiler.compiler_so += ["-Wno-unguarded-availability-new", "-Wno-unused-value"]
+            if config.check_func("ffi_prep_closure_loc", headers=['ffi.h'], include_dirs=[ffi_inc]):
+                ext.extra_compile_args.append("-DHAVE_FFI_PREP_CLOSURE_LOC=1")
+            if config.check_func("ffi_prep_cif_var", headers=['ffi.h'], include_dirs=[ffi_inc]):
+                ext.extra_compile_args.append("-DHAVE_FFI_PREP_CIF_VAR=1")
+            if host_platform == 'darwin' and config.check_func("ffi_closure_alloc", headers=['ffi.h'], include_dirs=[ffi_inc]):
+                ext.extra_compile_args.append("-DHAVE_FFI_CLOSURE_ALLOC=1")
             ext.include_dirs.extend(ffi_inc)
             ext.libraries.append(ffi_lib)
             self.use_system_libffi = True