diff --git a/Doc/c-api/object.rst b/Doc/c-api/object.rst
index a84235b..6d13855 100644
--- a/Doc/c-api/object.rst
+++ b/Doc/c-api/object.rst
@@ -264,6 +264,17 @@
    .. versionadded:: 3.9
 
 
+.. c:function:: PyObject* _PyObject_CallOneArg(PyObject *callable, PyObject *arg)
+
+   Call a callable Python object *callable* with exactly 1 positional argument
+   *arg* and no keyword arguments.
+
+   Return the result of the call on success, or raise an exception and return
+   *NULL* on failure.
+
+   .. versionadded:: 3.9
+
+
 .. c:function:: PyObject* PyObject_Call(PyObject *callable, PyObject *args, PyObject *kwargs)
 
    Call a callable Python object *callable*, with arguments given by the
diff --git a/Include/cpython/abstract.h b/Include/cpython/abstract.h
index 69ed943..c9a8a07 100644
--- a/Include/cpython/abstract.h
+++ b/Include/cpython/abstract.h
@@ -62,6 +62,7 @@
 static inline vectorcallfunc
 _PyVectorcall_Function(PyObject *callable)
 {
+    assert(callable != NULL);
     PyTypeObject *tp = Py_TYPE(callable);
     if (!PyType_HasFeature(tp, _Py_TPFLAGS_HAVE_VECTORCALL)) {
         return NULL;
@@ -134,6 +135,17 @@
     return _PyObject_Vectorcall(func, NULL, 0, NULL);
 }
 
+static inline PyObject *
+_PyObject_CallOneArg(PyObject *func, PyObject *arg)
+{
+    assert(arg != NULL);
+    PyObject *_args[2];
+    PyObject **args = _args + 1;  // For PY_VECTORCALL_ARGUMENTS_OFFSET
+    args[0] = arg;
+    return _PyObject_Vectorcall(func, args,
+                                1 | PY_VECTORCALL_ARGUMENTS_OFFSET, NULL);
+}
+
 PyAPI_FUNC(PyObject *) _PyObject_Call_Prepend(
     PyObject *callable,
     PyObject *obj,
diff --git a/Misc/NEWS.d/next/C API/2019-07-02-15-42-37.bpo-37483.vftT4f.rst b/Misc/NEWS.d/next/C API/2019-07-02-15-42-37.bpo-37483.vftT4f.rst
new file mode 100644
index 0000000..e2b0201
--- /dev/null
+++ b/Misc/NEWS.d/next/C API/2019-07-02-15-42-37.bpo-37483.vftT4f.rst
@@ -0,0 +1,2 @@
+Add new function ``_PyObject_CallOneArg`` for calling an object with one
+positional argument.
diff --git a/Modules/_asynciomodule.c b/Modules/_asynciomodule.c
index 4caf3a4..443acc5 100644
--- a/Modules/_asynciomodule.c
+++ b/Modules/_asynciomodule.c
@@ -141,8 +141,7 @@
        Do this check after 'future_init()'; in case we need to raise
        an error, __del__ needs a properly initialized object.
     */
-    PyObject *res = PyObject_CallFunctionObjArgs(
-        asyncio_iscoroutine_func, coro, NULL);
+    PyObject *res = _PyObject_CallOneArg(asyncio_iscoroutine_func, coro);
     if (res == NULL) {
         return -1;
     }
@@ -1286,8 +1285,7 @@
 _asyncio_Future__repr_info_impl(FutureObj *self)
 /*[clinic end generated code: output=fa69e901bd176cfb input=f21504d8e2ae1ca2]*/
 {
-    return PyObject_CallFunctionObjArgs(
-        asyncio_future_repr_info_func, self, NULL);
+    return _PyObject_CallOneArg(asyncio_future_repr_info_func, (PyObject *)self);
 }
 
 static PyObject *
@@ -1364,7 +1362,7 @@
 
     func = _PyObject_GetAttrId(fut->fut_loop, &PyId_call_exception_handler);
     if (func != NULL) {
-        PyObject *res = PyObject_CallFunctionObjArgs(func, context, NULL);
+        PyObject *res = _PyObject_CallOneArg(func, context);
         if (res == NULL) {
             PyErr_WriteUnraisable(func);
         }
@@ -2104,13 +2102,13 @@
             Py_DECREF(current_task_func);
             return NULL;
         }
-        ret = PyObject_CallFunctionObjArgs(current_task_func, loop, NULL);
+        ret = _PyObject_CallOneArg(current_task_func, loop);
         Py_DECREF(current_task_func);
         Py_DECREF(loop);
         return ret;
     }
     else {
-        ret = PyObject_CallFunctionObjArgs(current_task_func, loop, NULL);
+        ret = _PyObject_CallOneArg(current_task_func, loop);
         Py_DECREF(current_task_func);
         return ret;
     }
@@ -2146,7 +2144,7 @@
         return NULL;
     }
 
-    res = PyObject_CallFunctionObjArgs(all_tasks_func, loop, NULL);
+    res = _PyObject_CallOneArg(all_tasks_func, loop);
     Py_DECREF(all_tasks_func);
     return res;
 }
@@ -2159,8 +2157,7 @@
 _asyncio_Task__repr_info_impl(TaskObj *self)
 /*[clinic end generated code: output=6a490eb66d5ba34b input=3c6d051ed3ddec8b]*/
 {
-    return PyObject_CallFunctionObjArgs(
-        asyncio_task_repr_info_func, self, NULL);
+    return _PyObject_CallOneArg(asyncio_task_repr_info_func, (PyObject *)self);
 }
 
 /*[clinic input]
@@ -2411,7 +2408,7 @@
 
     func = _PyObject_GetAttrId(task->task_loop, &PyId_call_exception_handler);
     if (func != NULL) {
-        PyObject *res = PyObject_CallFunctionObjArgs(func, context, NULL);
+        PyObject *res = _PyObject_CallOneArg(func, context);
         if (res == NULL) {
             PyErr_WriteUnraisable(func);
         }
@@ -2543,7 +2540,7 @@
         return NULL;
     }
 
-    PyObject *e = PyObject_CallFunctionObjArgs(et, msg, NULL);
+    PyObject *e = _PyObject_CallOneArg(et, msg);
     Py_DECREF(msg);
     if (e == NULL) {
         return NULL;
diff --git a/Modules/_collectionsmodule.c b/Modules/_collectionsmodule.c
index 45169ec..cc7d3cf 100644
--- a/Modules/_collectionsmodule.c
+++ b/Modules/_collectionsmodule.c
@@ -512,8 +512,7 @@
         return NULL;
     }
     if (old_deque->maxlen < 0)
-        result = PyObject_CallFunctionObjArgs((PyObject *)(Py_TYPE(deque)),
-                                              deque, NULL);
+        result = _PyObject_CallOneArg((PyObject *)(Py_TYPE(deque)), deque);
     else
         result = PyObject_CallFunction((PyObject *)(Py_TYPE(deque)), "Oi",
                                        deque, old_deque->maxlen, NULL);
diff --git a/Modules/_csv.c b/Modules/_csv.c
index 014cbb4..9653ff9 100644
--- a/Modules/_csv.c
+++ b/Modules/_csv.c
@@ -1240,7 +1240,7 @@
     if (line == NULL) {
         return NULL;
     }
-    result = PyObject_CallFunctionObjArgs(self->write, line, NULL);
+    result = _PyObject_CallOneArg(self->write, line);
     Py_DECREF(line);
     return result;
 }
diff --git a/Modules/_ctypes/callproc.c b/Modules/_ctypes/callproc.c
index 6766524..973a654 100644
--- a/Modules/_ctypes/callproc.c
+++ b/Modules/_ctypes/callproc.c
@@ -925,7 +925,7 @@
     if (!checker || !retval)
         return retval;
 
-    v = PyObject_CallFunctionObjArgs(checker, retval, NULL);
+    v = _PyObject_CallOneArg(checker, retval);
     if (v == NULL)
         _PyTraceback_Add("GetResult", "_ctypes/callproc.c", __LINE__-2);
     Py_DECREF(retval);
@@ -1118,7 +1118,7 @@
         if (argtypes && argtype_count > i) {
             PyObject *v;
             converter = PyTuple_GET_ITEM(argtypes, i);
-            v = PyObject_CallFunctionObjArgs(converter, arg, NULL);
+            v = _PyObject_CallOneArg(converter, arg);
             if (v == NULL) {
                 _ctypes_extend_error(PyExc_ArgError, "argument %zd: ", i+1);
                 goto cleanup;
@@ -1795,7 +1795,7 @@
 
     typ = PyDict_GetItemWithError(_ctypes_ptrtype_cache, (PyObject *)Py_TYPE(arg));
     if (typ) {
-        return PyObject_CallFunctionObjArgs(typ, arg, NULL);
+        return _PyObject_CallOneArg(typ, arg);
     }
     else if (PyErr_Occurred()) {
         return NULL;
@@ -1803,7 +1803,7 @@
     typ = POINTER(NULL, (PyObject *)Py_TYPE(arg));
     if (typ == NULL)
         return NULL;
-    result = PyObject_CallFunctionObjArgs(typ, arg, NULL);
+    result = _PyObject_CallOneArg(typ, arg);
     Py_DECREF(typ);
     return result;
 }
diff --git a/Modules/_elementtree.c b/Modules/_elementtree.c
index ee1b5e5..b93ec3d 100644
--- a/Modules/_elementtree.c
+++ b/Modules/_elementtree.c
@@ -2696,7 +2696,7 @@
         PyObject *event = PyTuple_Pack(2, action, node);
         if (event == NULL)
             return -1;
-        res = _PyObject_FastCall(self->events_append, &event, 1);
+        res = _PyObject_CallOneArg(self->events_append, event);
         Py_DECREF(event);
         if (res == NULL)
             return -1;
@@ -2859,7 +2859,7 @@
     }
 
     if (self->comment_factory) {
-        comment = _PyObject_FastCall(self->comment_factory, &text, 1);
+        comment = _PyObject_CallOneArg(self->comment_factory, text);
         if (!comment)
             return NULL;
 
@@ -3197,7 +3197,7 @@
     if (errmsg == NULL)
         return;
 
-    error = _PyObject_FastCall(st->parseerror_obj, &errmsg, 1);
+    error = _PyObject_CallOneArg(st->parseerror_obj, errmsg);
     Py_DECREF(errmsg);
     if (!error)
         return;
@@ -3260,7 +3260,7 @@
                 (TreeBuilderObject*) self->target, value
                 );
         else if (self->handle_data)
-            res = _PyObject_FastCall(self->handle_data, &value, 1);
+            res = _PyObject_CallOneArg(self->handle_data, value);
         else
             res = NULL;
         Py_XDECREF(res);
@@ -3371,7 +3371,7 @@
         /* shortcut */
         res = treebuilder_handle_data((TreeBuilderObject*) self->target, data);
     else if (self->handle_data)
-        res = _PyObject_FastCall(self->handle_data, &data, 1);
+        res = _PyObject_CallOneArg(self->handle_data, data);
     else
         res = NULL;
 
@@ -3398,7 +3398,7 @@
     else if (self->handle_end) {
         tag = makeuniversal(self, tag_in);
         if (tag) {
-            res = _PyObject_FastCall(self->handle_end, &tag, 1);
+            res = _PyObject_CallOneArg(self->handle_end, tag);
             Py_DECREF(tag);
         }
     }
@@ -3485,7 +3485,7 @@
         if (!prefix)
             return;
 
-        res = _PyObject_FastCall(self->handle_end_ns, &prefix, 1);
+        res = _PyObject_CallOneArg(self->handle_end_ns, prefix);
         Py_DECREF(prefix);
     }
 
@@ -3515,7 +3515,7 @@
         if (!comment)
             return;
 
-        res = _PyObject_FastCall(self->handle_comment, &comment, 1);
+        res = _PyObject_CallOneArg(self->handle_comment, comment);
     }
 
     Py_XDECREF(res);
diff --git a/Modules/_io/iobase.c b/Modules/_io/iobase.c
index fab4509..82cc776 100644
--- a/Modules/_io/iobase.c
+++ b/Modules/_io/iobase.c
@@ -557,7 +557,7 @@
         PyObject *b;
 
         if (peek != NULL) {
-            PyObject *readahead = PyObject_CallFunctionObjArgs(peek, _PyLong_One, NULL);
+            PyObject *readahead = _PyObject_CallOneArg(peek, _PyLong_One);
             if (readahead == NULL) {
                 /* NOTE: PyErr_SetFromErrno() calls PyErr_CheckSignals()
                    when EINTR occurs so we needn't do it ourselves. */
diff --git a/Modules/_json.c b/Modules/_json.c
index e3aa997..38beb6f 100644
--- a/Modules/_json.c
+++ b/Modules/_json.c
@@ -818,14 +818,14 @@
     *next_idx_ptr = idx + 1;
 
     if (has_pairs_hook) {
-        val = PyObject_CallFunctionObjArgs(s->object_pairs_hook, rval, NULL);
+        val = _PyObject_CallOneArg(s->object_pairs_hook, rval);
         Py_DECREF(rval);
         return val;
     }
 
     /* if object_hook is not None: rval = object_hook(rval) */
     if (s->object_hook != Py_None) {
-        val = PyObject_CallFunctionObjArgs(s->object_hook, rval, NULL);
+        val = _PyObject_CallOneArg(s->object_hook, rval);
         Py_DECREF(rval);
         return val;
     }
@@ -931,7 +931,7 @@
         return NULL;
 
     /* rval = parse_constant(constant) */
-    rval = PyObject_CallFunctionObjArgs(s->parse_constant, cstr, NULL);
+    rval = _PyObject_CallOneArg(s->parse_constant, cstr);
     idx += PyUnicode_GET_LENGTH(cstr);
     Py_DECREF(cstr);
     *next_idx_ptr = idx;
@@ -1030,7 +1030,7 @@
                                            idx - start);
         if (numstr == NULL)
             return NULL;
-        rval = PyObject_CallFunctionObjArgs(custom_func, numstr, NULL);
+        rval = _PyObject_CallOneArg(custom_func, numstr);
     }
     else {
         Py_ssize_t i, n;
@@ -1440,7 +1440,7 @@
     if (s->fast_encode) {
         return s->fast_encode(NULL, obj);
     }
-    encoded = PyObject_CallFunctionObjArgs(s->encoder, obj, NULL);
+    encoded = _PyObject_CallOneArg(s->encoder, obj);
     if (encoded != NULL && !PyUnicode_Check(encoded)) {
         PyErr_Format(PyExc_TypeError,
                      "encoder() must return a string, not %.80s",
@@ -1526,7 +1526,7 @@
                 return -1;
             }
         }
-        newobj = PyObject_CallFunctionObjArgs(s->defaultfn, obj, NULL);
+        newobj = _PyObject_CallOneArg(s->defaultfn, obj);
         if (newobj == NULL) {
             Py_XDECREF(ident);
             return -1;
diff --git a/Modules/_pickle.c b/Modules/_pickle.c
index 3adece0..d6d1250 100644
--- a/Modules/_pickle.c
+++ b/Modules/_pickle.c
@@ -359,7 +359,7 @@
 {
     PyObject *result;
 
-    result = PyObject_CallFunctionObjArgs(func, obj, NULL);
+    result = _PyObject_CallOneArg(func, obj);
     Py_DECREF(obj);
     return result;
 }
@@ -420,7 +420,7 @@
         return PyObject_CallFunctionObjArgs(func, self, obj, NULL);
     }
     else {
-        return PyObject_CallFunctionObjArgs(func, obj, NULL);
+        return _PyObject_CallOneArg(func, obj);
     }
 }
 
@@ -2296,7 +2296,7 @@
                 return -1;
             }
         }
-        result = PyObject_CallFunctionObjArgs(self->write, payload, NULL);
+        result = _PyObject_CallOneArg(self->write, payload);
         Py_XDECREF(mem);
         if (result == NULL) {
             return -1;
@@ -2504,8 +2504,7 @@
     }
     int in_band = 1;
     if (self->buffer_callback != NULL) {
-        PyObject *ret = PyObject_CallFunctionObjArgs(self->buffer_callback,
-                                                     obj, NULL);
+        PyObject *ret = _PyObject_CallOneArg(self->buffer_callback, obj);
         if (ret == NULL) {
             return -1;
         }
@@ -4322,8 +4321,7 @@
      * regular reduction mechanism.
      */
     if (self->reducer_override != NULL) {
-        reduce_value = PyObject_CallFunctionObjArgs(self->reducer_override,
-                                                    obj, NULL);
+        reduce_value = _PyObject_CallOneArg(self->reducer_override, obj);
         if (reduce_value == NULL) {
             goto error;
         }
diff --git a/Modules/_sqlite/cache.c b/Modules/_sqlite/cache.c
index 4d41804..7552d1b 100644
--- a/Modules/_sqlite/cache.c
+++ b/Modules/_sqlite/cache.c
@@ -112,9 +112,8 @@
     Py_TYPE(self)->tp_free((PyObject*)self);
 }
 
-PyObject* pysqlite_cache_get(pysqlite_Cache* self, PyObject* args)
+PyObject* pysqlite_cache_get(pysqlite_Cache* self, PyObject* key)
 {
-    PyObject* key = args;
     pysqlite_Node* node;
     pysqlite_Node* ptr;
     PyObject* data;
@@ -184,6 +183,9 @@
             }
         }
 
+        /* We cannot replace this by _PyObject_CallOneArg() since
+         * PyObject_CallFunction() has a special case when using a
+         * single tuple as argument. */
         data = PyObject_CallFunction(self->factory, "O", key);
 
         if (!data) {
diff --git a/Modules/_sqlite/connection.c b/Modules/_sqlite/connection.c
index 5ceeaf9..08604b9 100644
--- a/Modules/_sqlite/connection.c
+++ b/Modules/_sqlite/connection.c
@@ -310,7 +310,7 @@
         factory = (PyObject*)&pysqlite_CursorType;
     }
 
-    cursor = PyObject_CallFunctionObjArgs(factory, (PyObject *)self, NULL);
+    cursor = _PyObject_CallOneArg(factory, (PyObject *)self);
     if (cursor == NULL)
         return NULL;
     if (!PyObject_TypeCheck(cursor, &pysqlite_CursorType)) {
@@ -970,7 +970,7 @@
     py_statement = PyUnicode_DecodeUTF8(statement_string,
             strlen(statement_string), "replace");
     if (py_statement) {
-        ret = PyObject_CallFunctionObjArgs((PyObject*)user_arg, py_statement, NULL);
+        ret = _PyObject_CallOneArg((PyObject*)user_arg, py_statement);
         Py_DECREF(py_statement);
     }
 
@@ -1465,16 +1465,9 @@
         goto finally;
     }
 
-    args = PyTuple_New(1);
-    if (!args) {
-        goto finally;
-    }
-    Py_INCREF(self);
-    PyTuple_SetItem(args, 0, (PyObject*)self);
-    retval = PyObject_CallObject(pyfn_iterdump, args);
+    retval = _PyObject_CallOneArg(pyfn_iterdump, (PyObject *)self);
 
 finally:
-    Py_XDECREF(args);
     Py_XDECREF(module);
     return retval;
 }
diff --git a/Modules/_sqlite/cursor.c b/Modules/_sqlite/cursor.c
index 38d94b2..e6fcac8 100644
--- a/Modules/_sqlite/cursor.c
+++ b/Modules/_sqlite/cursor.c
@@ -266,7 +266,7 @@
                 item = PyBytes_FromStringAndSize(val_str, nbytes);
                 if (!item)
                     goto error;
-                converted = PyObject_CallFunction(converter, "O", item);
+                converted = _PyObject_CallOneArg(converter, item);
                 Py_DECREF(item);
             }
         } else {
diff --git a/Modules/_sqlite/microprotocols.c b/Modules/_sqlite/microprotocols.c
index c23b09f..59a5e22 100644
--- a/Modules/_sqlite/microprotocols.c
+++ b/Modules/_sqlite/microprotocols.c
@@ -92,7 +92,7 @@
     Py_DECREF(key);
     if (adapter) {
         Py_INCREF(adapter);
-        adapted = PyObject_CallFunctionObjArgs(adapter, obj, NULL);
+        adapted = _PyObject_CallOneArg(adapter, obj);
         Py_DECREF(adapter);
         return adapted;
     }
@@ -105,7 +105,7 @@
         return NULL;
     }
     if (adapter) {
-        adapted = PyObject_CallFunctionObjArgs(adapter, obj, NULL);
+        adapted = _PyObject_CallOneArg(adapter, obj);
         Py_DECREF(adapter);
 
         if (adapted == Py_None) {
@@ -124,7 +124,7 @@
         return NULL;
     }
     if (adapter) {
-        adapted = PyObject_CallFunctionObjArgs(adapter, proto, NULL);
+        adapted = _PyObject_CallOneArg(adapter, proto);
         Py_DECREF(adapter);
 
         if (adapted == Py_None) {
diff --git a/Modules/_sre.c b/Modules/_sre.c
index d4fe588..f4f9d01 100644
--- a/Modules/_sre.c
+++ b/Modules/_sre.c
@@ -1082,7 +1082,7 @@
             match = pattern_new_match(self, &state, 1);
             if (!match)
                 goto error;
-            item = PyObject_CallFunctionObjArgs(filter, match, NULL);
+            item = _PyObject_CallOneArg(filter, match);
             Py_DECREF(match);
             if (!item)
                 goto error;
diff --git a/Modules/_struct.c b/Modules/_struct.c
index 9281c68..d1c635a 100644
--- a/Modules/_struct.c
+++ b/Modules/_struct.c
@@ -2098,7 +2098,7 @@
         return 0;
     }
 
-    s_object = PyObject_CallFunctionObjArgs((PyObject *)(&PyStructType), fmt, NULL);
+    s_object = _PyObject_CallOneArg((PyObject *)(&PyStructType), fmt);
     if (s_object != NULL) {
         if (PyDict_GET_SIZE(cache) >= MAXCACHE)
             PyDict_Clear(cache);
diff --git a/Modules/_xxtestfuzz/fuzzer.c b/Modules/_xxtestfuzz/fuzzer.c
index 16104e4..2446e71 100644
--- a/Modules/_xxtestfuzz/fuzzer.c
+++ b/Modules/_xxtestfuzz/fuzzer.c
@@ -104,7 +104,7 @@
     if (input_bytes == NULL) {
         return 0;
     }
-    PyObject* parsed = PyObject_CallFunctionObjArgs(json_loads_method, input_bytes, NULL);
+    PyObject* parsed = _PyObject_CallOneArg(json_loads_method, input_bytes);
     if (parsed == NULL) {
         /* Ignore ValueError as the fuzzer will more than likely
            generate some invalid json and values */
@@ -263,7 +263,7 @@
     PyObject* pattern = compiled_patterns[idx];
     PyObject* match_callable = PyObject_GetAttrString(pattern, "match");
 
-    PyObject* matches = PyObject_CallFunctionObjArgs(match_callable, to_match, NULL);
+    PyObject* matches = _PyObject_CallOneArg(match_callable, to_match);
 
     Py_XDECREF(matches);
     Py_DECREF(match_callable);
diff --git a/Modules/cjkcodecs/cjkcodecs.h b/Modules/cjkcodecs/cjkcodecs.h
index b67f348..7ed8365 100644
--- a/Modules/cjkcodecs/cjkcodecs.h
+++ b/Modules/cjkcodecs/cjkcodecs.h
@@ -291,7 +291,7 @@
     if (codecobj == NULL)
         return NULL;
 
-    r = PyObject_CallFunctionObjArgs(cofunc, codecobj, NULL);
+    r = _PyObject_CallOneArg(cofunc, codecobj);
     Py_DECREF(codecobj);
 
     return r;
diff --git a/Modules/cjkcodecs/multibytecodec.c b/Modules/cjkcodecs/multibytecodec.c
index c01a0e5..052ed88 100644
--- a/Modules/cjkcodecs/multibytecodec.c
+++ b/Modules/cjkcodecs/multibytecodec.c
@@ -81,7 +81,7 @@
 static PyObject *
 call_error_callback(PyObject *errors, PyObject *exc)
 {
-    PyObject *args, *cb, *r;
+    PyObject *cb, *r;
     const char *str;
 
     assert(PyUnicode_Check(errors));
@@ -92,17 +92,7 @@
     if (cb == NULL)
         return NULL;
 
-    args = PyTuple_New(1);
-    if (args == NULL) {
-        Py_DECREF(cb);
-        return NULL;
-    }
-
-    PyTuple_SET_ITEM(args, 0, exc);
-    Py_INCREF(exc);
-
-    r = PyObject_CallObject(cb, args);
-    Py_DECREF(args);
+    r = _PyObject_CallOneArg(cb, exc);
     Py_DECREF(cb);
     return r;
 }
diff --git a/Modules/gcmodule.c b/Modules/gcmodule.c
index 0cf00e8..2ee7651 100644
--- a/Modules/gcmodule.c
+++ b/Modules/gcmodule.c
@@ -763,7 +763,7 @@
         _PyObject_ASSERT(op, callback != NULL);
 
         /* copy-paste of weakrefobject.c's handle_callback() */
-        temp = PyObject_CallFunctionObjArgs(callback, wr, NULL);
+        temp = _PyObject_CallOneArg(callback, (PyObject *)wr);
         if (temp == NULL)
             PyErr_WriteUnraisable(callback);
         else
diff --git a/Modules/itertoolsmodule.c b/Modules/itertoolsmodule.c
index 00e3cbb..781d0cc 100644
--- a/Modules/itertoolsmodule.c
+++ b/Modules/itertoolsmodule.c
@@ -134,7 +134,7 @@
         newkey = newvalue;
         Py_INCREF(newvalue);
     } else {
-        newkey = PyObject_CallFunctionObjArgs(gbo->keyfunc, newvalue, NULL);
+        newkey = _PyObject_CallOneArg(gbo->keyfunc, newvalue);
         if (newkey == NULL) {
             Py_DECREF(newvalue);
             return -1;
@@ -1210,7 +1210,7 @@
         if (lz->start == 1)
             return item;
 
-        good = PyObject_CallFunctionObjArgs(lz->func, item, NULL);
+        good = _PyObject_CallOneArg(lz->func, item);
         if (good == NULL) {
             Py_DECREF(item);
             return NULL;
@@ -1373,7 +1373,7 @@
     if (item == NULL)
         return NULL;
 
-    good = PyObject_CallFunctionObjArgs(lz->func, item, NULL);
+    good = _PyObject_CallOneArg(lz->func, item);
     if (good == NULL) {
         Py_DECREF(item);
         return NULL;
@@ -3906,7 +3906,7 @@
             ok = PyObject_IsTrue(item);
         } else {
             PyObject *good;
-            good = PyObject_CallFunctionObjArgs(lz->func, item, NULL);
+            good = _PyObject_CallOneArg(lz->func, item);
             if (good == NULL) {
                 Py_DECREF(item);
                 return NULL;
diff --git a/Modules/pyexpat.c b/Modules/pyexpat.c
index 45a1e68..3d193e7 100644
--- a/Modules/pyexpat.c
+++ b/Modules/pyexpat.c
@@ -119,7 +119,7 @@
                                   XML_ErrorString(code), lineno, column);
     if (buffer == NULL)
         return NULL;
-    err = PyObject_CallFunctionObjArgs(ErrorObject, buffer, NULL);
+    err = _PyObject_CallOneArg(ErrorObject, buffer);
     Py_DECREF(buffer);
     if (  err != NULL
           && set_error_attr(err, "code", code)
diff --git a/Objects/abstract.c b/Objects/abstract.c
index 77d0914..86178a7 100644
--- a/Objects/abstract.c
+++ b/Objects/abstract.c
@@ -172,13 +172,13 @@
     }
 
     if (PyType_Check(o)) {
-        PyObject *meth, *result, *stack[1] = {key};
+        PyObject *meth, *result;
         _Py_IDENTIFIER(__class_getitem__);
         if (_PyObject_LookupAttrId(o, &PyId___class_getitem__, &meth) < 0) {
             return NULL;
         }
         if (meth) {
-            result = _PyObject_FastCall(meth, stack, 1);
+            result = _PyObject_CallOneArg(meth, key);
             Py_DECREF(meth);
             return result;
         }
@@ -737,7 +737,7 @@
     }
 
     /* And call it. */
-    result = PyObject_CallFunctionObjArgs(meth, format_spec, NULL);
+    result = _PyObject_CallOneArg(meth, format_spec);
     Py_DECREF(meth);
 
     if (result && !PyUnicode_Check(result)) {
@@ -2459,7 +2459,7 @@
             Py_DECREF(checker);
             return ok;
         }
-        res = PyObject_CallFunctionObjArgs(checker, inst, NULL);
+        res = _PyObject_CallOneArg(checker, inst);
         Py_LeaveRecursiveCall();
         Py_DECREF(checker);
         if (res != NULL) {
@@ -2533,7 +2533,7 @@
             Py_DECREF(checker);
             return ok;
         }
-        res = PyObject_CallFunctionObjArgs(checker, derived, NULL);
+        res = _PyObject_CallOneArg(checker, derived);
         Py_LeaveRecursiveCall();
         Py_DECREF(checker);
         if (res != NULL) {
diff --git a/Objects/bytearrayobject.c b/Objects/bytearrayobject.c
index 1bb19a9..9dd6712 100644
--- a/Objects/bytearrayobject.c
+++ b/Objects/bytearrayobject.c
@@ -89,8 +89,7 @@
 PyObject *
 PyByteArray_FromObject(PyObject *input)
 {
-    return PyObject_CallFunctionObjArgs((PyObject *)&PyByteArray_Type,
-                                        input, NULL);
+    return _PyObject_CallOneArg((PyObject *)&PyByteArray_Type, input);
 }
 
 static PyObject *
@@ -2018,8 +2017,7 @@
 {
     PyObject *result = _PyBytes_FromHex(string, type == &PyByteArray_Type);
     if (type != &PyByteArray_Type && result != NULL) {
-        Py_SETREF(result, PyObject_CallFunctionObjArgs((PyObject *)type,
-                                                       result, NULL));
+        Py_SETREF(result, _PyObject_CallOneArg((PyObject *)type, result));
     }
     return result;
 }
diff --git a/Objects/bytesobject.c b/Objects/bytesobject.c
index 06c87b0..c4edcca 100644
--- a/Objects/bytesobject.c
+++ b/Objects/bytesobject.c
@@ -2333,8 +2333,7 @@
 {
     PyObject *result = _PyBytes_FromHex(string, 0);
     if (type != &PyBytes_Type && result != NULL) {
-        Py_SETREF(result, PyObject_CallFunctionObjArgs((PyObject *)type,
-                                                       result, NULL));
+        Py_SETREF(result, _PyObject_CallOneArg((PyObject *)type, result));
     }
     return result;
 }
diff --git a/Objects/descrobject.c b/Objects/descrobject.c
index a0eb505..4b98578 100644
--- a/Objects/descrobject.c
+++ b/Objects/descrobject.c
@@ -1340,8 +1340,7 @@
         return NULL;
     }
 
-    PyObject *args[1] = {obj};
-    return _PyObject_FastCall(gs->prop_get, args, 1);
+    return _PyObject_CallOneArg(gs->prop_get, obj);
 }
 
 static int
@@ -1362,7 +1361,7 @@
         return -1;
     }
     if (value == NULL)
-        res = PyObject_CallFunctionObjArgs(func, obj, NULL);
+        res = _PyObject_CallOneArg(func, obj);
     else
         res = PyObject_CallFunctionObjArgs(func, obj, value, NULL);
     if (res == NULL)
diff --git a/Objects/dictobject.c b/Objects/dictobject.c
index 0cc1443..422f4b0 100644
--- a/Objects/dictobject.c
+++ b/Objects/dictobject.c
@@ -2113,8 +2113,7 @@
             _Py_IDENTIFIER(__missing__);
             missing = _PyObject_LookupSpecial((PyObject *)mp, &PyId___missing__);
             if (missing != NULL) {
-                res = PyObject_CallFunctionObjArgs(missing,
-                                                   key, NULL);
+                res = _PyObject_CallOneArg(missing, key);
                 Py_DECREF(missing);
                 return res;
             }
diff --git a/Objects/fileobject.c b/Objects/fileobject.c
index 3791241..a21e490 100644
--- a/Objects/fileobject.c
+++ b/Objects/fileobject.c
@@ -136,7 +136,7 @@
         Py_DECREF(writer);
         return -1;
     }
-    result = PyObject_CallFunctionObjArgs(writer, value, NULL);
+    result = _PyObject_CallOneArg(writer, value);
     Py_DECREF(value);
     Py_DECREF(writer);
     if (result == NULL)
diff --git a/Objects/floatobject.c b/Objects/floatobject.c
index 15cbe5c..689e929 100644
--- a/Objects/floatobject.c
+++ b/Objects/floatobject.c
@@ -1501,7 +1501,7 @@
         goto parse_error;
     result = PyFloat_FromDouble(negate ? -x : x);
     if (type != &PyFloat_Type && result != NULL) {
-        Py_SETREF(result, PyObject_CallFunctionObjArgs((PyObject *)type, result, NULL));
+        Py_SETREF(result, _PyObject_CallOneArg((PyObject *)type, result));
     }
     return result;
 
diff --git a/Objects/genobject.c b/Objects/genobject.c
index 2d9a286..5d1f9c7 100644
--- a/Objects/genobject.c
+++ b/Objects/genobject.c
@@ -57,7 +57,7 @@
             /* Save the current exception, if any. */
             PyErr_Fetch(&error_type, &error_value, &error_traceback);
 
-            res = PyObject_CallFunctionObjArgs(finalizer, self, NULL);
+            res = _PyObject_CallOneArg(finalizer, self);
 
             if (res == NULL) {
                 PyErr_WriteUnraisable(self);
@@ -562,7 +562,7 @@
         return 0;
     }
     /* Construct an exception instance manually with
-     * PyObject_CallFunctionObjArgs and pass it to PyErr_SetObject.
+     * _PyObject_CallOneArg and pass it to PyErr_SetObject.
      *
      * We do this to handle a situation when "value" is a tuple, in which
      * case PyErr_SetObject would set the value of StopIteration to
@@ -570,7 +570,7 @@
      *
      * (See PyErr_SetObject/_PyErr_CreateException code for details.)
      */
-    e = PyObject_CallFunctionObjArgs(PyExc_StopIteration, value, NULL);
+    e = _PyObject_CallOneArg(PyExc_StopIteration, value);
     if (e == NULL) {
         return -1;
     }
@@ -1279,7 +1279,7 @@
         PyObject *res;
 
         Py_INCREF(firstiter);
-        res = PyObject_CallFunctionObjArgs(firstiter, o, NULL);
+        res = _PyObject_CallOneArg(firstiter, (PyObject *)o);
         Py_DECREF(firstiter);
         if (res == NULL) {
             return 1;
diff --git a/Objects/listobject.c b/Objects/listobject.c
index f8bf45e..d012ab9 100644
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -2258,8 +2258,7 @@
         }
 
         for (i = 0; i < saved_ob_size ; i++) {
-            keys[i] = PyObject_CallFunctionObjArgs(keyfunc, saved_ob_item[i],
-                                                   NULL);
+            keys[i] = _PyObject_CallOneArg(keyfunc, saved_ob_item[i]);
             if (keys[i] == NULL) {
                 for (i=i-1 ; i>=0 ; i--)
                     Py_DECREF(keys[i]);
diff --git a/Objects/longobject.c b/Objects/longobject.c
index 50ea2a4..3978f5c 100644
--- a/Objects/longobject.c
+++ b/Objects/longobject.c
@@ -5611,8 +5611,7 @@
     Py_DECREF(bytes);
 
     if (long_obj != NULL && type != &PyLong_Type) {
-        Py_SETREF(long_obj, PyObject_CallFunctionObjArgs((PyObject *)type,
-                                                         long_obj, NULL));
+        Py_SETREF(long_obj, _PyObject_CallOneArg((PyObject *)type, long_obj));
     }
 
     return long_obj;
diff --git a/Objects/memoryobject.c b/Objects/memoryobject.c
index a873ac1..66920eaf 100644
--- a/Objects/memoryobject.c
+++ b/Objects/memoryobject.c
@@ -1962,7 +1962,7 @@
     if (format == NULL)
         goto error;
 
-    structobj = PyObject_CallFunctionObjArgs(Struct, format, NULL);
+    structobj = _PyObject_CallOneArg(Struct, format);
     if (structobj == NULL)
         goto error;
 
@@ -2001,7 +2001,7 @@
     PyObject *v;
 
     memcpy(x->item, ptr, x->itemsize);
-    v = PyObject_CallFunctionObjArgs(x->unpack_from, x->mview, NULL);
+    v = _PyObject_CallOneArg(x->unpack_from, x->mview);
     if (v == NULL)
         return NULL;
 
diff --git a/Objects/moduleobject.c b/Objects/moduleobject.c
index 85134c7..92f97e6 100644
--- a/Objects/moduleobject.c
+++ b/Objects/moduleobject.c
@@ -736,8 +736,7 @@
         _Py_IDENTIFIER(__getattr__);
         getattr = _PyDict_GetItemId(m->md_dict, &PyId___getattr__);
         if (getattr) {
-            PyObject* stack[1] = {name};
-            return _PyObject_FastCall(getattr, stack, 1);
+            return _PyObject_CallOneArg(getattr, name);
         }
         _Py_IDENTIFIER(__name__);
         mod_name = _PyDict_GetItemId(m->md_dict, &PyId___name__);
diff --git a/Objects/typeobject.c b/Objects/typeobject.c
index f814333..3b9a537 100644
--- a/Objects/typeobject.c
+++ b/Objects/typeobject.c
@@ -1459,8 +1459,7 @@
 call_unbound_noarg(int unbound, PyObject *func, PyObject *self)
 {
     if (unbound) {
-        PyObject *args[1] = {self};
-        return _PyObject_FastCall(func, args, 1);
+        return _PyObject_CallOneArg(func, self);
     }
     else {
         return _PyObject_CallNoArg(func);
@@ -6561,7 +6560,7 @@
         else
             attr = descr;
     }
-    res = PyObject_CallFunctionObjArgs(attr, name, NULL);
+    res = _PyObject_CallOneArg(attr, name);
     Py_XDECREF(descr);
     return res;
 }
diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index 51d314b..5545eae 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -4248,7 +4248,7 @@
     if (*exceptionObject == NULL)
         goto onError;
 
-    restuple = PyObject_CallFunctionObjArgs(*errorHandler, *exceptionObject, NULL);
+    restuple = _PyObject_CallOneArg(*errorHandler, *exceptionObject);
     if (restuple == NULL)
         goto onError;
     if (!PyTuple_Check(restuple)) {
@@ -4352,7 +4352,7 @@
     if (*exceptionObject == NULL)
         goto onError;
 
-    restuple = PyObject_CallFunctionObjArgs(*errorHandler, *exceptionObject, NULL);
+    restuple = _PyObject_CallOneArg(*errorHandler, *exceptionObject);
     if (restuple == NULL)
         goto onError;
     if (!PyTuple_Check(restuple)) {
@@ -6799,8 +6799,7 @@
     if (*exceptionObject == NULL)
         return NULL;
 
-    restuple = PyObject_CallFunctionObjArgs(
-        *errorHandler, *exceptionObject, NULL);
+    restuple = _PyObject_CallOneArg(*errorHandler, *exceptionObject);
     if (restuple == NULL)
         return NULL;
     if (!PyTuple_Check(restuple)) {
@@ -8778,8 +8777,7 @@
     if (*exceptionObject == NULL)
         return NULL;
 
-    restuple = PyObject_CallFunctionObjArgs(
-        *errorHandler, *exceptionObject, NULL);
+    restuple = _PyObject_CallOneArg(*errorHandler, *exceptionObject);
     if (restuple == NULL)
         return NULL;
     if (!PyTuple_Check(restuple)) {
diff --git a/Objects/weakrefobject.c b/Objects/weakrefobject.c
index 8b8e710..ae3f6dc 100644
--- a/Objects/weakrefobject.c
+++ b/Objects/weakrefobject.c
@@ -874,7 +874,7 @@
 static void
 handle_callback(PyWeakReference *ref, PyObject *callback)
 {
-    PyObject *cbresult = PyObject_CallFunctionObjArgs(callback, ref, NULL);
+    PyObject *cbresult = _PyObject_CallOneArg(callback, (PyObject *)ref);
 
     if (cbresult == NULL)
         PyErr_WriteUnraisable(callback);
diff --git a/Python/_warnings.c b/Python/_warnings.c
index 0b19258..b1762e6 100644
--- a/Python/_warnings.c
+++ b/Python/_warnings.c
@@ -590,7 +590,7 @@
     if (msg == NULL)
         goto error;
 
-    res = PyObject_CallFunctionObjArgs(show_fn, msg, NULL);
+    res = _PyObject_CallOneArg(show_fn, msg);
     Py_DECREF(show_fn);
     Py_DECREF(msg);
 
@@ -651,7 +651,7 @@
     }
     else {
         text = message;
-        message = PyObject_CallFunctionObjArgs(category, message, NULL);
+        message = _PyObject_CallOneArg(category, message);
         if (message == NULL)
             goto cleanup;
     }
@@ -996,7 +996,7 @@
         return NULL;
     }
     /* Call get_source() to get the source code. */
-    source = PyObject_CallFunctionObjArgs(get_source, module_name, NULL);
+    source = _PyObject_CallOneArg(get_source, module_name);
     Py_DECREF(get_source);
     Py_DECREF(module_name);
     if (!source) {
@@ -1283,7 +1283,7 @@
     int warned = 0;
     PyObject *fn = get_warnings_attr(&PyId__warn_unawaited_coroutine, 1);
     if (fn) {
-        PyObject *res = PyObject_CallFunctionObjArgs(fn, coro, NULL);
+        PyObject *res = _PyObject_CallOneArg(fn, coro);
         Py_DECREF(fn);
         if (res || PyErr_ExceptionMatches(PyExc_RuntimeWarning)) {
             warned = 1;
diff --git a/Python/bltinmodule.c b/Python/bltinmodule.c
index 90fbb44..5de4363 100644
--- a/Python/bltinmodule.c
+++ b/Python/bltinmodule.c
@@ -29,7 +29,6 @@
 {
     Py_ssize_t i, j;
     PyObject *base, *meth, *new_base, *result, *new_bases = NULL;
-    PyObject *stack[1] = {bases};
     assert(PyTuple_Check(bases));
 
     for (i = 0; i < nargs; i++) {
@@ -55,7 +54,7 @@
             }
             continue;
         }
-        new_base = _PyObject_FastCall(meth, stack, 1);
+        new_base = _PyObject_CallOneArg(meth, bases);
         Py_DECREF(meth);
         if (!new_base) {
             goto error;
@@ -574,7 +573,7 @@
             ok = PyObject_IsTrue(item);
         } else {
             PyObject *good;
-            good = PyObject_CallFunctionObjArgs(lz->func, item, NULL);
+            good = _PyObject_CallOneArg(lz->func, item);
             if (good == NULL) {
                 Py_DECREF(item);
                 return NULL;
@@ -1625,7 +1624,7 @@
     while (( item = PyIter_Next(it) )) {
         /* get the value from the key function */
         if (keyfunc != NULL) {
-            val = PyObject_CallFunctionObjArgs(keyfunc, item, NULL);
+            val = _PyObject_CallOneArg(keyfunc, item);
             if (val == NULL)
                 goto Fail_it_item;
         }
@@ -2178,7 +2177,7 @@
     if (ndigits == NULL || ndigits == Py_None)
         result = _PyObject_CallNoArg(round);
     else
-        result = PyObject_CallFunctionObjArgs(round, ndigits, NULL);
+        result = _PyObject_CallOneArg(round, ndigits);
     Py_DECREF(round);
     return result;
 }
diff --git a/Python/ceval.c b/Python/ceval.c
index 888749b..b0fd6ee 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -1874,7 +1874,7 @@
                 Py_DECREF(value);
                 goto error;
             }
-            res = PyObject_CallFunctionObjArgs(hook, value, NULL);
+            res = _PyObject_CallOneArg(hook, value);
             Py_DECREF(value);
             if (res == NULL)
                 goto error;
diff --git a/Python/codecs.c b/Python/codecs.c
index d4b34f8..3865762 100644
--- a/Python/codecs.c
+++ b/Python/codecs.c
@@ -99,7 +99,7 @@
 
 PyObject *_PyCodec_Lookup(const char *encoding)
 {
-    PyObject *result, *args = NULL, *v;
+    PyObject *result, *v;
     Py_ssize_t i, len;
 
     if (encoding == NULL) {
@@ -132,13 +132,6 @@
     }
 
     /* Next, scan the search functions in order of registration */
-    args = PyTuple_New(1);
-    if (args == NULL) {
-        Py_DECREF(v);
-        return NULL;
-    }
-    PyTuple_SET_ITEM(args,0,v);
-
     len = PyList_Size(interp->codec_search_path);
     if (len < 0)
         goto onError;
@@ -155,7 +148,7 @@
         func = PyList_GetItem(interp->codec_search_path, i);
         if (func == NULL)
             goto onError;
-        result = PyEval_CallObject(func, args);
+        result = _PyObject_CallOneArg(func, v);
         if (result == NULL)
             goto onError;
         if (result == Py_None) {
@@ -182,11 +175,9 @@
         Py_DECREF(result);
         goto onError;
     }
-    Py_DECREF(args);
     return result;
 
  onError:
-    Py_XDECREF(args);
     return NULL;
 }
 
@@ -325,7 +316,7 @@
     if (errors != NULL)
         streamcodec = PyObject_CallFunction(codeccls, "Os", stream, errors);
     else
-        streamcodec = PyObject_CallFunctionObjArgs(codeccls, stream, NULL);
+        streamcodec = _PyObject_CallOneArg(codeccls, stream);
     Py_DECREF(codecs);
     return streamcodec;
 }
diff --git a/Python/errors.c b/Python/errors.c
index b3b9ac9..a7d40c1 100644
--- a/Python/errors.c
+++ b/Python/errors.c
@@ -93,7 +93,7 @@
         return PyObject_Call(exception, value, NULL);
     }
     else {
-        return PyObject_CallFunctionObjArgs(exception, value, NULL);
+        return _PyObject_CallOneArg(exception, value);
     }
 }
 
@@ -1381,8 +1381,7 @@
         hook_args = make_unraisable_hook_args(tstate, exc_type, exc_value,
                                               exc_tb, err_msg, obj);
         if (hook_args != NULL) {
-            PyObject *args[1] = {hook_args};
-            PyObject *res = _PyObject_FastCall(hook, args, 1);
+            PyObject *res = _PyObject_CallOneArg(hook, hook_args);
             Py_DECREF(hook_args);
             if (res != NULL) {
                 Py_DECREF(res);
diff --git a/Python/import.c b/Python/import.c
index 3937fbe..76866ae 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -1180,7 +1180,7 @@
         PyObject *hook = PyList_GetItem(path_hooks, j);
         if (hook == NULL)
             return NULL;
-        importer = PyObject_CallFunctionObjArgs(hook, p, NULL);
+        importer = _PyObject_CallOneArg(hook, p);
         if (importer != NULL)
             break;