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.

11 files changed, 209 insertions, 222 deletions

diff --git a/Lib/test/clinic.test.c b/Lib/test/clinic.test.c
index 2a071f8485a..e22324efc49 100644
--- a/Lib/test/clinic.test.c
+++ b/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]
diff --git a/Lib/test/test_clinic.py b/Lib/test/test_clinic.py
index 402106194f1..d492ea1d76a 100644
--- a/Lib/test/test_clinic.py
+++ b/Lib/test/test_clinic.py
@@ -3381,8 +3381,8 @@ class ClinicFunctionalTest(unittest.TestCase):
     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)
diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2024-10-27-20-31-43.gh-issue-90370.IP_W3a.rst b/Misc/NEWS.d/next/Core_and_Builtins/2024-10-27-20-31-43.gh-issue-90370.IP_W3a.rst
new file mode 100644
index 00000000000..b6a19c06a22
--- /dev/null
+++ b/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).
diff --git a/Modules/_testclinic.c b/Modules/_testclinic.c
index ca884af1aa2..e3c8ba9b0b5 100644
--- a/Modules/_testclinic.c
+++ b/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;
 }
diff --git a/Modules/clinic/_testclinic.c.h b/Modules/clinic/_testclinic.c.h
index 1988c069710..7e29998c7db 100644
--- a/Modules/clinic/_testclinic.c.h
+++ b/Modules/clinic/_testclinic.c.h
@@ -2530,28 +2530,22 @@ PyDoc_STRVAR(varpos__doc__,
     {"varpos", _PyCFunction_CAST(varpos), METH_FASTCALL, varpos__doc__},
 
 static PyObject *
-varpos_impl(PyObject *module, PyObject *args);
+varpos_impl(PyObject *module, Py_ssize_t nargs, PyObject *const *args);
 
 static PyObject *
 varpos(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
 {
     PyObject *return_value = NULL;
-    PyObject *__clinic_args = NULL;
+    Py_ssize_t nvararg = nargs - 0;
+    PyObject *const *__clinic_args = NULL;
 
     if (!_PyArg_CheckPositional("varpos", nargs, 0, PY_SSIZE_T_MAX)) {
         goto exit;
     }
-    __clinic_args = PyTuple_New(nargs - 0);
-    if (!__clinic_args) {
-        goto exit;
-    }
-    for (Py_ssize_t i = 0; i < nargs - 0; ++i) {
-        PyTuple_SET_ITEM(__clinic_args, i, Py_NewRef(args[0 + i]));
-    }
-    return_value = varpos_impl(module, __clinic_args);
+    __clinic_args = args + 0;
+    return_value = varpos_impl(module, nvararg, __clinic_args);
 
 exit:
-    Py_XDECREF(__clinic_args);
     return return_value;
 }
 
@@ -2565,32 +2559,26 @@ PyDoc_STRVAR(posonly_varpos__doc__,
 
 static PyObject *
 posonly_varpos_impl(PyObject *module, PyObject *a, PyObject *b,
-                    PyObject *args);
+                    Py_ssize_t nargs, PyObject *const *args);
 
 static PyObject *
 posonly_varpos(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
 {
     PyObject *return_value = NULL;
+    Py_ssize_t nvararg = nargs - 2;
     PyObject *a;
     PyObject *b;
-    PyObject *__clinic_args = NULL;
+    PyObject *const *__clinic_args = NULL;
 
     if (!_PyArg_CheckPositional("posonly_varpos", nargs, 2, PY_SSIZE_T_MAX)) {
         goto exit;
     }
     a = args[0];
     b = args[1];
-    __clinic_args = PyTuple_New(nargs - 2);
-    if (!__clinic_args) {
-        goto exit;
-    }
-    for (Py_ssize_t i = 0; i < nargs - 2; ++i) {
-        PyTuple_SET_ITEM(__clinic_args, i, Py_NewRef(args[2 + i]));
-    }
-    return_value = posonly_varpos_impl(module, a, b, __clinic_args);
+    __clinic_args = args + 2;
+    return_value = posonly_varpos_impl(module, a, b, nvararg, __clinic_args);
 
 exit:
-    Py_XDECREF(__clinic_args);
     return return_value;
 }
 
@@ -3136,28 +3124,23 @@ PyDoc_STRVAR(gh_99233_refcount__doc__,
     {"gh_99233_refcount", _PyCFunction_CAST(gh_99233_refcount), METH_FASTCALL, gh_99233_refcount__doc__},
 
 static PyObject *
-gh_99233_refcount_impl(PyObject *module, PyObject *args);
+gh_99233_refcount_impl(PyObject *module, Py_ssize_t nargs,
+                       PyObject *const *args);
 
 static PyObject *
 gh_99233_refcount(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
 {
     PyObject *return_value = NULL;
-    PyObject *__clinic_args = NULL;
+    Py_ssize_t nvararg = nargs - 0;
+    PyObject *const *__clinic_args = NULL;
 
     if (!_PyArg_CheckPositional("gh_99233_refcount", nargs, 0, PY_SSIZE_T_MAX)) {
         goto exit;
     }
-    __clinic_args = PyTuple_New(nargs - 0);
-    if (!__clinic_args) {
-        goto exit;
-    }
-    for (Py_ssize_t i = 0; i < nargs - 0; ++i) {
-        PyTuple_SET_ITEM(__clinic_args, i, Py_NewRef(args[0 + i]));
-    }
-    return_value = gh_99233_refcount_impl(module, __clinic_args);
+    __clinic_args = args + 0;
+    return_value = gh_99233_refcount_impl(module, nvararg, __clinic_args);
 
 exit:
-    Py_XDECREF(__clinic_args);
     return return_value;
 }
 
@@ -3693,4 +3676,4 @@ exit:
     Py_XDECREF(__clinic_args);
     return return_value;
 }
-/*[clinic end generated code: output=76ecbb38c632bde8 input=a9049054013a1b77]*/
+/*[clinic end generated code: output=7662d07e7d29cbeb input=a9049054013a1b77]*/
diff --git a/Modules/clinic/gcmodule.c.h b/Modules/clinic/gcmodule.c.h
index 9fff4da616b..be3bd35b4ff 100644
--- a/Modules/clinic/gcmodule.c.h
+++ b/Modules/clinic/gcmodule.c.h
@@ -312,28 +312,23 @@ PyDoc_STRVAR(gc_get_referrers__doc__,
     {"get_referrers", _PyCFunction_CAST(gc_get_referrers), METH_FASTCALL, gc_get_referrers__doc__},
 
 static PyObject *
-gc_get_referrers_impl(PyObject *module, PyObject *args);
+gc_get_referrers_impl(PyObject *module, Py_ssize_t nargs,
+                      PyObject *const *args);
 
 static PyObject *
 gc_get_referrers(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
 {
     PyObject *return_value = NULL;
-    PyObject *__clinic_args = NULL;
+    Py_ssize_t nvararg = nargs - 0;
+    PyObject *const *__clinic_args = NULL;
 
     if (!_PyArg_CheckPositional("get_referrers", nargs, 0, PY_SSIZE_T_MAX)) {
         goto exit;
     }
-    __clinic_args = PyTuple_New(nargs - 0);
-    if (!__clinic_args) {
-        goto exit;
-    }
-    for (Py_ssize_t i = 0; i < nargs - 0; ++i) {
-        PyTuple_SET_ITEM(__clinic_args, i, Py_NewRef(args[0 + i]));
-    }
-    return_value = gc_get_referrers_impl(module, __clinic_args);
+    __clinic_args = args + 0;
+    return_value = gc_get_referrers_impl(module, nvararg, __clinic_args);
 
 exit:
-    Py_XDECREF(__clinic_args);
     return return_value;
 }
 
@@ -347,28 +342,23 @@ PyDoc_STRVAR(gc_get_referents__doc__,
     {"get_referents", _PyCFunction_CAST(gc_get_referents), METH_FASTCALL, gc_get_referents__doc__},
 
 static PyObject *
-gc_get_referents_impl(PyObject *module, PyObject *args);
+gc_get_referents_impl(PyObject *module, Py_ssize_t nargs,
+                      PyObject *const *args);
 
 static PyObject *
 gc_get_referents(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
 {
     PyObject *return_value = NULL;
-    PyObject *__clinic_args = NULL;
+    Py_ssize_t nvararg = nargs - 0;
+    PyObject *const *__clinic_args = NULL;
 
     if (!_PyArg_CheckPositional("get_referents", nargs, 0, PY_SSIZE_T_MAX)) {
         goto exit;
     }
-    __clinic_args = PyTuple_New(nargs - 0);
-    if (!__clinic_args) {
-        goto exit;
-    }
-    for (Py_ssize_t i = 0; i < nargs - 0; ++i) {
-        PyTuple_SET_ITEM(__clinic_args, i, Py_NewRef(args[0 + i]));
-    }
-    return_value = gc_get_referents_impl(module, __clinic_args);
+    __clinic_args = args + 0;
+    return_value = gc_get_referents_impl(module, nvararg, __clinic_args);
 
 exit:
-    Py_XDECREF(__clinic_args);
     return return_value;
 }
 
@@ -585,4 +575,4 @@ gc_get_freeze_count(PyObject *module, PyObject *Py_UNUSED(ignored))
 exit:
     return return_value;
 }
-/*[clinic end generated code: output=0a7e91917adcb937 input=a9049054013a1b77]*/
+/*[clinic end generated code: output=f488a0d4d6bd3687 input=a9049054013a1b77]*/
diff --git a/Modules/gcmodule.c b/Modules/gcmodule.c
index 57e4aae9ed5..f5fea5aa4dd 100644
--- a/Modules/gcmodule.c
+++ b/Modules/gcmodule.c
@@ -8,6 +8,7 @@
 #include "pycore_gc.h"
 #include "pycore_object.h"      // _PyObject_IS_GC()
 #include "pycore_pystate.h"     // _PyInterpreterState_GET()
+#include "pycore_tuple.h"       // _PyTuple_FromArray()
 
 typedef struct _gc_runtime_state GCState;
 
@@ -221,15 +222,25 @@ Return the list of objects that directly refer to any of 'objs'.
 [clinic start generated code]*/
 
 static PyObject *
-gc_get_referrers_impl(PyObject *module, PyObject *args)
-/*[clinic end generated code: output=296a09587f6a86b5 input=bae96961b14a0922]*/
+gc_get_referrers_impl(PyObject *module, Py_ssize_t nargs,
+                      PyObject *const *args)
+/*[clinic end generated code: output=1d44a7695ea25c40 input=bae96961b14a0922]*/
 {
-    if (PySys_Audit("gc.get_referrers", "(O)", args) < 0) {
+    PyObject *varargs = _PyTuple_FromArray(args, nargs);
+
+    if (!varargs) {
+        return NULL;
+    }
+    if (PySys_Audit("gc.get_referrers", "(O)", varargs) < 0) {
+        Py_DECREF(varargs);
         return NULL;
     }
 
     PyInterpreterState *interp = _PyInterpreterState_GET();
-    return _PyGC_GetReferrers(interp, args);
+    PyObject *result = _PyGC_GetReferrers(interp, varargs);
+
+    Py_DECREF(varargs);
+    return result;
 }
 
 /* Append obj to list; return true if error (out of memory), false if OK. */
@@ -269,27 +280,37 @@ Return the list of objects that are directly referred to by 'objs'.
 [clinic start generated code]*/
 
 static PyObject *
-gc_get_referents_impl(PyObject *module, PyObject *args)
-/*[clinic end generated code: output=d47dc02cefd06fe8 input=b3ceab0c34038cbf]*/
+gc_get_referents_impl(PyObject *module, Py_ssize_t nargs,
+                      PyObject *const *args)
+/*[clinic end generated code: output=e459f3e8c0d19311 input=b3ceab0c34038cbf]*/
 {
-    if (PySys_Audit("gc.get_referents", "(O)", args) < 0) {
+    PyObject *varargs = _PyTuple_FromArray(args, nargs);
+
+    if (!varargs) {
+        return NULL;
+    }
+    if (PySys_Audit("gc.get_referents", "(O)", varargs) < 0) {
+        Py_DECREF(varargs);
         return NULL;
     }
     PyInterpreterState *interp = _PyInterpreterState_GET();
     PyObject *result = PyList_New(0);
 
-    if (result == NULL)
+    if (result == NULL) {
+        Py_DECREF(varargs);
         return NULL;
+    }
 
     // NOTE: stop the world is a no-op in default build
     _PyEval_StopTheWorld(interp);
-    int err = append_referrents(result, args);
+    int err = append_referrents(result, varargs);
     _PyEval_StartTheWorld(interp);
 
     if (err < 0) {
         Py_CLEAR(result);
     }
 
+    Py_DECREF(varargs);
     return result;
 }
 
diff --git a/Objects/clinic/setobject.c.h b/Objects/clinic/setobject.c.h
index 3853ce3bce6..d6e381a9975 100644
--- a/Objects/clinic/setobject.c.h
+++ b/Objects/clinic/setobject.c.h
@@ -41,28 +41,22 @@ PyDoc_STRVAR(set_update__doc__,
     {"update", _PyCFunction_CAST(set_update), METH_FASTCALL, set_update__doc__},
 
 static PyObject *
-set_update_impl(PySetObject *so, PyObject *args);
+set_update_impl(PySetObject *so, Py_ssize_t nargs, PyObject *const *args);
 
 static PyObject *
 set_update(PySetObject *so, PyObject *const *args, Py_ssize_t nargs)
 {
     PyObject *return_value = NULL;
-    PyObject *__clinic_args = NULL;
+    Py_ssize_t nvararg = nargs - 0;
+    PyObject *const *__clinic_args = NULL;
 
     if (!_PyArg_CheckPositional("update", nargs, 0, PY_SSIZE_T_MAX)) {
         goto exit;
     }
-    __clinic_args = PyTuple_New(nargs - 0);
-    if (!__clinic_args) {
-        goto exit;
-    }
-    for (Py_ssize_t i = 0; i < nargs - 0; ++i) {
-        PyTuple_SET_ITEM(__clinic_args, i, Py_NewRef(args[0 + i]));
-    }
-    return_value = set_update_impl(so, __clinic_args);
+    __clinic_args = args + 0;
+    return_value = set_update_impl(so, nvararg, __clinic_args);
 
 exit:
-    Py_XDECREF(__clinic_args);
     return return_value;
 }
 
@@ -148,28 +142,22 @@ PyDoc_STRVAR(set_union__doc__,
     {"union", _PyCFunction_CAST(set_union), METH_FASTCALL, set_union__doc__},
 
 static PyObject *
-set_union_impl(PySetObject *so, PyObject *args);
+set_union_impl(PySetObject *so, Py_ssize_t nargs, PyObject *const *args);
 
 static PyObject *
 set_union(PySetObject *so, PyObject *const *args, Py_ssize_t nargs)
 {
     PyObject *return_value = NULL;
-    PyObject *__clinic_args = NULL;
+    Py_ssize_t nvararg = nargs - 0;
+    PyObject *const *__clinic_args = NULL;
 
     if (!_PyArg_CheckPositional("union", nargs, 0, PY_SSIZE_T_MAX)) {
         goto exit;
     }
-    __clinic_args = PyTuple_New(nargs - 0);
-    if (!__clinic_args) {
-        goto exit;
-    }
-    for (Py_ssize_t i = 0; i < nargs - 0; ++i) {
-        PyTuple_SET_ITEM(__clinic_args, i, Py_NewRef(args[0 + i]));
-    }
-    return_value = set_union_impl(so, __clinic_args);
+    __clinic_args = args + 0;
+    return_value = set_union_impl(so, nvararg, __clinic_args);
 
 exit:
-    Py_XDECREF(__clinic_args);
     return return_value;
 }
 
@@ -183,28 +171,23 @@ PyDoc_STRVAR(set_intersection_multi__doc__,
     {"intersection", _PyCFunction_CAST(set_intersection_multi), METH_FASTCALL, set_intersection_multi__doc__},
 
 static PyObject *
-set_intersection_multi_impl(PySetObject *so, PyObject *args);
+set_intersection_multi_impl(PySetObject *so, Py_ssize_t nargs,
+                            PyObject *const *args);
 
 static PyObject *
 set_intersection_multi(PySetObject *so, PyObject *const *args, Py_ssize_t nargs)
 {
     PyObject *return_value = NULL;
-    PyObject *__clinic_args = NULL;
+    Py_ssize_t nvararg = nargs - 0;
+    PyObject *const *__clinic_args = NULL;
 
     if (!_PyArg_CheckPositional("intersection", nargs, 0, PY_SSIZE_T_MAX)) {
         goto exit;
     }
-    __clinic_args = PyTuple_New(nargs - 0);
-    if (!__clinic_args) {
-        goto exit;
-    }
-    for (Py_ssize_t i = 0; i < nargs - 0; ++i) {
-        PyTuple_SET_ITEM(__clinic_args, i, Py_NewRef(args[0 + i]));
-    }
-    return_value = set_intersection_multi_impl(so, __clinic_args);
+    __clinic_args = args + 0;
+    return_value = set_intersection_multi_impl(so, nvararg, __clinic_args);
 
 exit:
-    Py_XDECREF(__clinic_args);
     return return_value;
 }
 
@@ -218,28 +201,23 @@ PyDoc_STRVAR(set_intersection_update_multi__doc__,
     {"intersection_update", _PyCFunction_CAST(set_intersection_update_multi), METH_FASTCALL, set_intersection_update_multi__doc__},
 
 static PyObject *
-set_intersection_update_multi_impl(PySetObject *so, PyObject *args);
+set_intersection_update_multi_impl(PySetObject *so, Py_ssize_t nargs,
+                                   PyObject *const *args);
 
 static PyObject *
 set_intersection_update_multi(PySetObject *so, PyObject *const *args, Py_ssize_t nargs)
 {
     PyObject *return_value = NULL;
-    PyObject *__clinic_args = NULL;
+    Py_ssize_t nvararg = nargs - 0;
+    PyObject *const *__clinic_args = NULL;
 
     if (!_PyArg_CheckPositional("intersection_update", nargs, 0, PY_SSIZE_T_MAX)) {
         goto exit;
     }
-    __clinic_args = PyTuple_New(nargs - 0);
-    if (!__clinic_args) {
-        goto exit;
-    }
-    for (Py_ssize_t i = 0; i < nargs - 0; ++i) {
-        PyTuple_SET_ITEM(__clinic_args, i, Py_NewRef(args[0 + i]));
-    }
-    return_value = set_intersection_update_multi_impl(so, __clinic_args);
+    __clinic_args = args + 0;
+    return_value = set_intersection_update_multi_impl(so, nvararg, __clinic_args);
 
 exit:
-    Py_XDECREF(__clinic_args);
     return return_value;
 }
 
@@ -277,28 +255,23 @@ PyDoc_STRVAR(set_difference_update__doc__,
     {"difference_update", _PyCFunction_CAST(set_difference_update), METH_FASTCALL, set_difference_update__doc__},
 
 static PyObject *
-set_difference_update_impl(PySetObject *so, PyObject *args);
+set_difference_update_impl(PySetObject *so, Py_ssize_t nargs,
+                           PyObject *const *args);
 
 static PyObject *
 set_difference_update(PySetObject *so, PyObject *const *args, Py_ssize_t nargs)
 {
     PyObject *return_value = NULL;
-    PyObject *__clinic_args = NULL;
+    Py_ssize_t nvararg = nargs - 0;
+    PyObject *const *__clinic_args = NULL;
 
     if (!_PyArg_CheckPositional("difference_update", nargs, 0, PY_SSIZE_T_MAX)) {
         goto exit;
     }
-    __clinic_args = PyTuple_New(nargs - 0);
-    if (!__clinic_args) {
-        goto exit;
-    }
-    for (Py_ssize_t i = 0; i < nargs - 0; ++i) {
-        PyTuple_SET_ITEM(__clinic_args, i, Py_NewRef(args[0 + i]));
-    }
-    return_value = set_difference_update_impl(so, __clinic_args);
+    __clinic_args = args + 0;
+    return_value = set_difference_update_impl(so, nvararg, __clinic_args);
 
 exit:
-    Py_XDECREF(__clinic_args);
     return return_value;
 }
 
@@ -312,28 +285,23 @@ PyDoc_STRVAR(set_difference_multi__doc__,
     {"difference", _PyCFunction_CAST(set_difference_multi), METH_FASTCALL, set_difference_multi__doc__},
 
 static PyObject *
-set_difference_multi_impl(PySetObject *so, PyObject *args);
+set_difference_multi_impl(PySetObject *so, Py_ssize_t nargs,
+                          PyObject *const *args);
 
 static PyObject *
 set_difference_multi(PySetObject *so, PyObject *const *args, Py_ssize_t nargs)
 {
     PyObject *return_value = NULL;
-    PyObject *__clinic_args = NULL;
+    Py_ssize_t nvararg = nargs - 0;
+    PyObject *const *__clinic_args = NULL;
 
     if (!_PyArg_CheckPositional("difference", nargs, 0, PY_SSIZE_T_MAX)) {
         goto exit;
     }
-    __clinic_args = PyTuple_New(nargs - 0);
-    if (!__clinic_args) {
-        goto exit;
-    }
-    for (Py_ssize_t i = 0; i < nargs - 0; ++i) {
-        PyTuple_SET_ITEM(__clinic_args, i, Py_NewRef(args[0 + i]));
-    }
-    return_value = set_difference_multi_impl(so, __clinic_args);
+    __clinic_args = args + 0;
+    return_value = set_difference_multi_impl(so, nvararg, __clinic_args);
 
 exit:
-    Py_XDECREF(__clinic_args);
     return return_value;
 }
 
@@ -568,4 +536,4 @@ set___sizeof__(PySetObject *so, PyObject *Py_UNUSED(ignored))
 
     return return_value;
 }
-/*[clinic end generated code: output=de4ee725bd29f758 input=a9049054013a1b77]*/
+/*[clinic end generated code: output=9d4b41191b2c602f input=a9049054013a1b77]*/
diff --git a/Objects/setobject.c b/Objects/setobject.c
index 9f40e085f06..66d7fc730c5 100644
--- a/Objects/setobject.c
+++ b/Objects/setobject.c
@@ -1060,13 +1060,13 @@ Update the set, adding elements from all others.
 [clinic start generated code]*/
 
 static PyObject *
-set_update_impl(PySetObject *so, PyObject *args)
-/*[clinic end generated code: output=34f6371704974c8a input=df4fe486e38cd337]*/
+set_update_impl(PySetObject *so, Py_ssize_t nargs, PyObject *const *args)
+/*[clinic end generated code: output=050e2a21f8d7d16a input=df4fe486e38cd337]*/
 {
     Py_ssize_t i;
 
-    for (i=0 ; i<PyTuple_GET_SIZE(args) ; i++) {
-        PyObject *other = PyTuple_GET_ITEM(args, i);
+    for (i = 0; i < nargs; i++) {
+        PyObject *other = args[i];
         if (set_update_internal(so, other))
             return NULL;
     }
@@ -1289,8 +1289,8 @@ Return a new set with elements from the set and all others.
 [clinic start generated code]*/
 
 static PyObject *
-set_union_impl(PySetObject *so, PyObject *args)
-/*[clinic end generated code: output=2c83d05a446a1477 input=ddf088706e9577b2]*/
+set_union_impl(PySetObject *so, Py_ssize_t nargs, PyObject *const *args)
+/*[clinic end generated code: output=f68ec24d5c19d404 input=ddf088706e9577b2]*/
 {
     PySetObject *result;
     PyObject *other;
@@ -1300,8 +1300,8 @@ set_union_impl(PySetObject *so, PyObject *args)
     if (result == NULL)
         return NULL;
 
-    for (i=0 ; i<PyTuple_GET_SIZE(args) ; i++) {
-        other = PyTuple_GET_ITEM(args, i);
+    for (i = 0; i < nargs; i++) {
+        other = args[i];
         if ((PyObject *)so == other)
             continue;
         if (set_update_local(result, other)) {
@@ -1440,18 +1440,19 @@ Return a new set with elements common to the set and all others.
 [clinic start generated code]*/
 
 static PyObject *
-set_intersection_multi_impl(PySetObject *so, PyObject *args)
-/*[clinic end generated code: output=2406ef3387adbe2f input=0d9f3805ccbba6a4]*/
+set_intersection_multi_impl(PySetObject *so, Py_ssize_t nargs,
+                            PyObject *const *args)
+/*[clinic end generated code: output=ef0756ddb5f2dee9 input=0d9f3805ccbba6a4]*/
 {
     Py_ssize_t i;
 
-    if (PyTuple_GET_SIZE(args) == 0) {
+    if (nargs == 0) {
         return set_copy(so, NULL);
     }
 
     PyObject *result = Py_NewRef(so);
-    for (i=0 ; i<PyTuple_GET_SIZE(args) ; i++) {
-        PyObject *other = PyTuple_GET_ITEM(args, i);
+    for (i = 0; i < nargs; i++) {
+        PyObject *other = args[i];
         PyObject *newresult;
         Py_BEGIN_CRITICAL_SECTION2(result, other);
         newresult = set_intersection((PySetObject *)result, other);
@@ -1487,12 +1488,13 @@ Update the set, keeping only elements found in it and all others.
 [clinic start generated code]*/
 
 static PyObject *
-set_intersection_update_multi_impl(PySetObject *so, PyObject *args)
-/*[clinic end generated code: output=251c1f729063609d input=223c1e086aa669a9]*/
+set_intersection_update_multi_impl(PySetObject *so, Py_ssize_t nargs,
+                                   PyObject *const *args)
+/*[clinic end generated code: output=808d7ad1935b1dfe input=223c1e086aa669a9]*/
 {
     PyObject *tmp;
 
-    tmp = set_intersection_multi_impl(so, args);
+    tmp = set_intersection_multi_impl(so, nargs, args);
     if (tmp == NULL)
         return NULL;
     Py_BEGIN_CRITICAL_SECTION(so);
@@ -1676,13 +1678,14 @@ Update the set, removing elements found in others.
 [clinic start generated code]*/
 
 static PyObject *
-set_difference_update_impl(PySetObject *so, PyObject *args)
-/*[clinic end generated code: output=28685b2fc63e41c4 input=024e6baa6fbcbb3d]*/
+set_difference_update_impl(PySetObject *so, Py_ssize_t nargs,
+                           PyObject *const *args)
+/*[clinic end generated code: output=55f850c27748d312 input=024e6baa6fbcbb3d]*/
 {
     Py_ssize_t i;
 
-    for (i=0 ; i<PyTuple_GET_SIZE(args) ; i++) {
-        PyObject *other = PyTuple_GET_ITEM(args, i);
+    for (i = 0; i < nargs; i++) {
+        PyObject *other = args[i];
         int rv;
         Py_BEGIN_CRITICAL_SECTION2(so, other);
         rv = set_difference_update_internal(so, other);
@@ -1793,25 +1796,26 @@ Return a new set with elements in the set that are not in the others.
 [clinic start generated code]*/
 
 static PyObject *
-set_difference_multi_impl(PySetObject *so, PyObject *args)
-/*[clinic end generated code: output=3130c3bb3cac873d input=ba78ea5f099e58df]*/
+set_difference_multi_impl(PySetObject *so, Py_ssize_t nargs,
+                          PyObject *const *args)
+/*[clinic end generated code: output=8150d008c00523f3 input=ba78ea5f099e58df]*/
 {
     Py_ssize_t i;
     PyObject *result, *other;
 
-    if (PyTuple_GET_SIZE(args) == 0) {
+    if (nargs == 0) {
         return set_copy(so, NULL);
     }
 
-    other = PyTuple_GET_ITEM(args, 0);
+    other = args[0];
     Py_BEGIN_CRITICAL_SECTION2(so, other);
     result = set_difference(so, other);
     Py_END_CRITICAL_SECTION2();
     if (result == NULL)
         return NULL;
 
-    for (i=1 ; i<PyTuple_GET_SIZE(args) ; i++) {
-        other = PyTuple_GET_ITEM(args, i);
+    for (i = 1; i < nargs; i++) {
+        other = args[i];
         int rv;
         Py_BEGIN_CRITICAL_SECTION(other);
         rv = set_difference_update_internal((PySetObject *)result, other);
diff --git a/Tools/clinic/libclinic/clanguage.py b/Tools/clinic/libclinic/clanguage.py
index 73d47833d97..32aba81ab8a 100644
--- a/Tools/clinic/libclinic/clanguage.py
+++ b/Tools/clinic/libclinic/clanguage.py
@@ -15,7 +15,7 @@ from libclinic.function import (
     Module, Class, Function, Parameter,
     permute_optional_groups,
     GETTER, SETTER, METHOD_INIT)
-from libclinic.converters import self_converter
+from libclinic.converters import defining_class_converter, self_converter
 from libclinic.parse_args import ParseArgsCodeGen
 if TYPE_CHECKING:
     from libclinic.app import Clinic
@@ -396,6 +396,12 @@ class CLanguage(Language):
         first_optional = len(selfless)
         positional = selfless and selfless[-1].is_positional_only()
         has_option_groups = False
+        requires_defining_class = (len(selfless)
+                                   and isinstance(selfless[0].converter,
+                                                  defining_class_converter))
+        pass_vararg_directly = (all(p.is_positional_only() or p.is_vararg()
+                                    for p in selfless)
+                                and not requires_defining_class)
 
         # offset i by -1 because first_optional needs to ignore self
         for i, p in enumerate(parameters, -1):
@@ -404,7 +410,7 @@ class CLanguage(Language):
             if (i != -1) and (p.default is not unspecified):
                 first_optional = min(first_optional, i)
 
-            if p.is_vararg():
+            if p.is_vararg() and not pass_vararg_directly:
                 data.cleanup.append(f"Py_XDECREF({c.parser_name});")
 
             # insert group variable
@@ -418,6 +424,11 @@ class CLanguage(Language):
                     data.impl_parameters.append("int " + group_name)
                     has_option_groups = True
 
+            if p.is_vararg() and pass_vararg_directly:
+                data.impl_arguments.append('nvararg')
+                data.impl_parameters.append('Py_ssize_t nargs')
+                p.converter.type = 'PyObject *const *'
+
             c.render(p, data)
 
         if has_option_groups and (not positional):
diff --git a/Tools/clinic/libclinic/parse_args.py b/Tools/clinic/libclinic/parse_args.py
index 96c9b919bff..559d4fbdd09 100644
--- a/Tools/clinic/libclinic/parse_args.py
+++ b/Tools/clinic/libclinic/parse_args.py
@@ -469,7 +469,11 @@ class ParseArgsCodeGen:
                 nargs = 'PyTuple_GET_SIZE(args)'
                 argname_fmt = 'PyTuple_GET_ITEM(args, %d)'
 
-        left_args = f"{nargs} - {self.max_pos}"
+        if self.vararg != NO_VARARG:
+            self.declarations = f"Py_ssize_t nvararg = {nargs} - {self.max_pos};"
+        else:
+            self.declarations = ""
+
         max_args = NO_VARARG if (self.vararg != NO_VARARG) else self.max_pos
         if self.limited_capi:
             parser_code = []
@@ -518,30 +522,13 @@ class ParseArgsCodeGen:
         use_parser_code = True
         for i, p in enumerate(self.parameters):
             if p.is_vararg():
+                var = p.converter.parser_name
                 if self.fastcall:
-                    parser_code.append(libclinic.normalize_snippet("""
-                        %s = PyTuple_New(%s);
-                        if (!%s) {{
-                            goto exit;
-                        }}
-                        for (Py_ssize_t i = 0; i < %s; ++i) {{
-                            PyTuple_SET_ITEM(%s, i, Py_NewRef(args[%d + i]));
-                        }}
-                        """ % (
-                            p.converter.parser_name,
-                            left_args,
-                            p.converter.parser_name,
-                            left_args,
-                            p.converter.parser_name,
-                            self.max_pos
-                        ), indent=4))
+                    code = f"{var} = args + {self.vararg};"
                 else:
-                    parser_code.append(libclinic.normalize_snippet("""
-                        %s = PyTuple_GetSlice(%d, -1);
-                        """ % (
-                            p.converter.parser_name,
-                            self.max_pos
-                        ), indent=4))
+                    code = f"{var} = _PyTuple_CAST(args)->ob_item;"
+                formatted_code = libclinic.normalize_snippet(code, indent=4)
+                parser_code.append(formatted_code)
                 continue
 
             displayname = p.get_displayname(i+1)
@@ -588,7 +575,7 @@ class ParseArgsCodeGen:
                         goto exit;
                     }}
                     """, indent=4)]
-        self.parser_body(*parser_code)
+        self.parser_body(*parser_code, declarations=self.declarations)
 
     def parse_general(self, clang: CLanguage) -> None:
         parsearg: str | None