gh-90370: Argument Clinic: avoid temporary tuple creation for varargs (…

…#126064)

Avoid temporary tuple creation when all arguments either positional-only
or vararg.

Objects/setobject.c and Modules/gcmodule.c adapted. This fixes slight
performance regression for set methods, introduced by gh-115112.

Lib/test/clinic.test.c

@@ -4148,36 +4148,32 @@ PyDoc_STRVAR(test_vararg_and_posonly__doc__,
     {"test_vararg_and_posonly", _PyCFunction_CAST(test_vararg_and_posonly), METH_FASTCALL, test_vararg_and_posonly__doc__},
 
 static PyObject *
-test_vararg_and_posonly_impl(PyObject *module, PyObject *a, PyObject *args);
+test_vararg_and_posonly_impl(PyObject *module, PyObject *a, Py_ssize_t nargs,
+                             PyObject *const *args);
 
 static PyObject *
 test_vararg_and_posonly(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
 {
     PyObject *return_value = NULL;
+    Py_ssize_t nvararg = nargs - 1;
     PyObject *a;
-    PyObject *__clinic_args = NULL;
+    PyObject *const *__clinic_args = NULL;
 
     if (!_PyArg_CheckPositional("test_vararg_and_posonly", nargs, 1, PY_SSIZE_T_MAX)) {
         goto exit;
     }
     a = args[0];
-    __clinic_args = PyTuple_New(nargs - 1);
-    if (!__clinic_args) {
-        goto exit;
-    }
-    for (Py_ssize_t i = 0; i < nargs - 1; ++i) {
-        PyTuple_SET_ITEM(__clinic_args, i, Py_NewRef(args[1 + i]));
-    }
-    return_value = test_vararg_and_posonly_impl(module, a, __clinic_args);
+    __clinic_args = args + 1;
+    return_value = test_vararg_and_posonly_impl(module, a, nvararg, __clinic_args);
 
 exit:
-    Py_XDECREF(__clinic_args);
     return return_value;
 }
 
 static PyObject *
-test_vararg_and_posonly_impl(PyObject *module, PyObject *a, PyObject *args)
-/*[clinic end generated code: output=79b75dc07decc8d6 input=9cfa748bbff09877]*/
+test_vararg_and_posonly_impl(PyObject *module, PyObject *a, Py_ssize_t nargs,
+                             PyObject *const *args)
+/*[clinic end generated code: output=dc2dd9483cc0459e input=9cfa748bbff09877]*/
 
 /*[clinic input]
 test_vararg
@@ -4931,14 +4927,14 @@ PyDoc_STRVAR(Test___init____doc__,
 "Varargs init method. For example, nargs is translated to PyTuple_GET_SIZE.");
 
 static int
-Test___init___impl(TestObj *self, PyObject *args);
+Test___init___impl(TestObj *self, Py_ssize_t nargs, PyObject *const *args);
 
 static int
 Test___init__(PyObject *self, PyObject *args, PyObject *kwargs)
 {
     int return_value = -1;
     PyTypeObject *base_tp = TestType;
-    PyObject *__clinic_args = NULL;
+    PyObject *const *__clinic_args = NULL;
 
     if ((Py_IS_TYPE(self, base_tp) ||
          Py_TYPE(self)->tp_new == base_tp->tp_new) &&
@@ -4948,17 +4944,16 @@ Test___init__(PyObject *self, PyObject *args, PyObject *kwargs)
     if (!_PyArg_CheckPositional("Test", PyTuple_GET_SIZE(args), 0, PY_SSIZE_T_MAX)) {
         goto exit;
     }
-    __clinic_args = PyTuple_GetSlice(0, -1);
-    return_value = Test___init___impl((TestObj *)self, __clinic_args);
+    __clinic_args = _PyTuple_CAST(args)->ob_item;
+    return_value = Test___init___impl((TestObj *)self, nvararg, __clinic_args);
 
 exit:
-    Py_XDECREF(__clinic_args);
     return return_value;
 }
 
 static int
-Test___init___impl(TestObj *self, PyObject *args)
-/*[clinic end generated code: output=0ed1009fe0dcf98d input=2a8bd0033c9ac772]*/
+Test___init___impl(TestObj *self, Py_ssize_t nargs, PyObject *const *args)
+/*[clinic end generated code: output=6a64b417c9080a73 input=2a8bd0033c9ac772]*/
 
 
 /*[clinic input]
@@ -4976,14 +4971,14 @@ PyDoc_STRVAR(Test__doc__,
 "Varargs new method. For example, nargs is translated to PyTuple_GET_SIZE.");
 
 static PyObject *
-Test_impl(PyTypeObject *type, PyObject *args);
+Test_impl(PyTypeObject *type, Py_ssize_t nargs, PyObject *const *args);
 
 static PyObject *
 Test(PyTypeObject *type, PyObject *args, PyObject *kwargs)
 {
     PyObject *return_value = NULL;
     PyTypeObject *base_tp = TestType;
-    PyObject *__clinic_args = NULL;
+    PyObject *const *__clinic_args = NULL;
 
     if ((type == base_tp || type->tp_init == base_tp->tp_init) &&
         !_PyArg_NoKeywords("Test", kwargs)) {
@@ -4992,17 +4987,16 @@ Test(PyTypeObject *type, PyObject *args, PyObject *kwargs)
     if (!_PyArg_CheckPositional("Test", PyTuple_GET_SIZE(args), 0, PY_SSIZE_T_MAX)) {
         goto exit;
     }
-    __clinic_args = PyTuple_GetSlice(0, -1);
-    return_value = Test_impl(type, __clinic_args);
+    __clinic_args = _PyTuple_CAST(args)->ob_item;
+    return_value = Test_impl(type, nvararg, __clinic_args);
 
 exit:
-    Py_XDECREF(__clinic_args);
     return return_value;
 }
 
 static PyObject *
-Test_impl(PyTypeObject *type, PyObject *args)
-/*[clinic end generated code: output=8b219f6633e2a2e9 input=70ad829df3dd9b84]*/
+Test_impl(PyTypeObject *type, Py_ssize_t nargs, PyObject *const *args)
+/*[clinic end generated code: output=bf22f942407383a5 input=70ad829df3dd9b84]*/
 
 
 /*[clinic input]

Lib/test/test_clinic.py

@@ -3381,8 +3381,8 @@ def test_keyword_only_parameter(self):
     def test_varpos(self):
         # fn(*args)
         fn = ac_tester.varpos
-        self.assertEqual(fn(), ())
-        self.assertEqual(fn(1, 2), (1, 2))
+        self.assertEqual(fn(), ((),))
+        self.assertEqual(fn(1, 2), ((1, 2),))
 
     def test_posonly_varpos(self):
         # fn(a, b, /, *args)

Misc/NEWS.d/next/Core_and_Builtins/2024-10-27-20-31-43.gh-issue-90370.IP_W3a.rst

@@ -0,0 +1,2 @@
+Avoid temporary tuple creation for vararg in argument passing with Argument
+Clinic generated code (if arguments either vararg or positional-only).

Modules/_testclinic.c

@@ -58,6 +58,20 @@ pack_arguments_newref(int argc, ...)
     return tuple;
 }
 
+static PyObject *
+pack_varargs_to_tuple(Py_ssize_t varargssize, PyObject *const *args)
+{
+    assert(!PyErr_Occurred());
+    PyObject *tuple = PyTuple_New(varargssize);
+    if (!tuple) {
+        return NULL;
+    }
+    for (Py_ssize_t i = 0; i < varargssize; i++) {
+        PyTuple_SET_ITEM(tuple, i, Py_NewRef(args[i]));
+    }
+    return tuple;
+}
+
 /* Pack arguments to a tuple.
  * `wrapper` is function which converts primitive type to PyObject.
  * `arg_type` is type that arguments should be converted to before wrapped. */
@@ -970,10 +984,16 @@ varpos
 [clinic start generated code]*/
 
 static PyObject *
-varpos_impl(PyObject *module, PyObject *args)
-/*[clinic end generated code: output=7b0b9545872bdca4 input=f87cd674145d394c]*/
+varpos_impl(PyObject *module, Py_ssize_t nargs, PyObject *const *args)
+/*[clinic end generated code: output=b65096f423fb5dcc input=f87cd674145d394c]*/
 {
-    return Py_NewRef(args);
+    PyObject *vararg_tuple = pack_varargs_to_tuple(nargs, args);
+    if (!vararg_tuple) {
+        return NULL;
+    }
+    PyObject *result =  pack_arguments_newref(1, vararg_tuple);
+    Py_DECREF(vararg_tuple);
+    return result;
 }
 
 
@@ -989,10 +1009,16 @@ posonly_varpos
 
 static PyObject *
 posonly_varpos_impl(PyObject *module, PyObject *a, PyObject *b,
-                    PyObject *args)
-/*[clinic end generated code: output=5dae5eb2a0d623cd input=c9fd7895cfbaabba]*/
+                    Py_ssize_t nargs, PyObject *const *args)
+/*[clinic end generated code: output=d10d43d86d117ab3 input=c9fd7895cfbaabba]*/
 {
-    return pack_arguments_newref(3, a, b, args);
+    PyObject *vararg_tuple = pack_varargs_to_tuple(nargs, args);
+    if (!vararg_tuple) {
+        return NULL;
+    }
+    PyObject *result = pack_arguments_newref(3, a, b, vararg_tuple);
+    Py_DECREF(vararg_tuple);
+    return result;
 }
 
 
@@ -1157,8 +1183,9 @@ Proof-of-concept of GH-99233 refcount error bug.
 [clinic start generated code]*/
 
 static PyObject *
-gh_99233_refcount_impl(PyObject *module, PyObject *args)
-/*[clinic end generated code: output=585855abfbca9a7f input=eecfdc2092d90dc3]*/
+gh_99233_refcount_impl(PyObject *module, Py_ssize_t nargs,
+                       PyObject *const *args)
+/*[clinic end generated code: output=b570007e61e5c670 input=eecfdc2092d90dc3]*/
 {
     Py_RETURN_NONE;
 }