python · methane · Jul 4, 2019 · Jul 2, 2019
diff --git a/Doc/c-api/object.rst b/Doc/c-api/object.rst
@@ -264,6 +264,17 @@ Object Protocol
    .. 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
@@ -62,6 +62,7 @@ PyVectorcall_NARGS(size_t n)
 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 @@ _PyObject_CallNoArg(PyObject *func) {
     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
@@ -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
@@ -141,8 +141,7 @@ _is_coroutine(PyObject *coro)
        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 @@ static PyObject *
 _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 @@ FutureObj_finalize(FutureObj *fut)
 
     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 @@ _asyncio_Task_current_task_impl(PyTypeObject *type, PyObject *loop)
             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 @@ _asyncio_Task_all_tasks_impl(PyTypeObject *type, PyObject *loop)
         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 @@ static PyObject *
 _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 @@ TaskObj_finalize(TaskObj *task)
 
     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 @@ task_set_error_soon(TaskObj *task, PyObject *et, const char *format, ...)
         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
@@ -512,8 +512,7 @@ deque_copy(PyObject *deque, PyObject *Py_UNUSED(ignored))
         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
@@ -1240,7 +1240,7 @@ csv_writerow(WriterObj *self, PyObject *seq)
     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
@@ -925,7 +925,7 @@ static PyObject *GetResult(PyObject *restype, void *result, PyObject *checker)
     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 @@ PyObject *_ctypes_callproc(PPROC pProc,
         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;
@@ -1795,15 +1795,15 @@ pointer(PyObject *self, PyObject *arg)
 
     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;
     }
     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
@@ -2696,7 +2696,7 @@ treebuilder_append_event(TreeBuilderObject *self, PyObject *action,
         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 @@ treebuilder_handle_comment(TreeBuilderObject* self, PyObject* text)
     }
 
     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 @@ expat_set_error(enum XML_Error error_code, Py_ssize_t line, Py_ssize_t column,
     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 @@ expat_default_handler(XMLParserObject* self, const XML_Char* data_in,
                 (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 @@ expat_data_handler(XMLParserObject* self, const XML_Char* data_in,
         /* 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 @@ expat_end_handler(XMLParserObject* self, const XML_Char* tag_in)
     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 @@ expat_end_ns_handler(XMLParserObject* self, const XML_Char* prefix_in)
         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 @@ expat_comment_handler(XMLParserObject* self, const XML_Char* comment_in)
         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
@@ -557,7 +557,7 @@ _io__IOBase_readline_impl(PyObject *self, Py_ssize_t limit)
         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
@@ -818,14 +818,14 @@ _parse_object_unicode(PyScannerObject *s, PyObject *pystr, Py_ssize_t idx, Py_ss
     *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 @@ _parse_constant(PyScannerObject *s, const char *constant, Py_ssize_t idx, Py_ssi
         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 @@ _match_number_unicode(PyScannerObject *s, PyObject *pystr, Py_ssize_t start, Py_
                                            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 @@ encoder_encode_string(PyEncoderObject *s, PyObject *obj)
     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 @@ encoder_listencode_obj(PyEncoderObject *s, _PyAccu *acc,
                 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
@@ -359,7 +359,7 @@ _Pickle_FastCall(PyObject *func, PyObject *obj)
 {
     PyObject *result;
 
-    result = PyObject_CallFunctionObjArgs(func, obj, NULL);
+    result = _PyObject_CallOneArg(func, obj);
     Py_DECREF(obj);
     return result;
 }
@@ -420,7 +420,7 @@ call_method(PyObject *func, PyObject *self, PyObject *obj)
         return PyObject_CallFunctionObjArgs(func, self, obj, NULL);
     }
     else {
-        return PyObject_CallFunctionObjArgs(func, obj, NULL);
+        return _PyObject_CallOneArg(func, obj);
     }
 }
 
@@ -2296,7 +2296,7 @@ _Pickler_write_bytes(PicklerObject *self,
                 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 @@ save_picklebuffer(PicklerObject *self, PyObject *obj)
     }
     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 @@ save(PicklerObject *self, PyObject *obj, int pers_save)
      * 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
@@ -112,9 +112,8 @@ void pysqlite_cache_dealloc(pysqlite_Cache* self)
     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 @@ PyObject* pysqlite_cache_get(pysqlite_Cache* self, PyObject* args)
             }
         }
 
+        /* 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) {
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,2 @@
		Add new function ``_PyObject_CallOneArg`` for calling an object with one
		positional argument.