gh-64490: Fix refcount error when arguments are packed to tuple in argument clinic (#99233)

Author: colorfulappl

Lib/test/clinic.test

@@ -3793,7 +3793,7 @@ test_vararg_and_posonly(PyObject *module, PyObject *const *args, Py_ssize_t narg
     a = args[0];
     __clinic_args = PyTuple_New(nargs - 1);
     for (Py_ssize_t i = 0; i < nargs - 1; ++i) {
-        PyTuple_SET_ITEM(__clinic_args, i, args[1 + i]);
+        PyTuple_SET_ITEM(__clinic_args, i, Py_NewRef(args[1 + i]));
     }
     return_value = test_vararg_and_posonly_impl(module, a, __clinic_args);
 
@@ -3804,7 +3804,7 @@ exit:
 
 static PyObject *
 test_vararg_and_posonly_impl(PyObject *module, PyObject *a, PyObject *args)
-/*[clinic end generated code: output=548bca3a127c22c1 input=08dc2bf7afbf1613]*/
+/*[clinic end generated code: output=081a953b8cbe7617 input=08dc2bf7afbf1613]*/
 
 /*[clinic input]
 test_vararg

Lib/test/test_clinic.py

@@ -1211,6 +1211,20 @@ def test_keyword_only_parameter(self):
             ac_tester.keyword_only_parameter(1)
         self.assertEqual(ac_tester.keyword_only_parameter(a=1), (1,))
 
+    def test_vararg_and_posonly(self):
+        with self.assertRaises(TypeError):
+            ac_tester.vararg_and_posonly()
+        with self.assertRaises(TypeError):
+            ac_tester.vararg_and_posonly(1, b=2)
+        self.assertEqual(ac_tester.vararg_and_posonly(1, 2, 3, 4), (1, (2, 3, 4)))
+
+    def test_gh_99233_refcount(self):
+        arg = '*A unique string is not referenced by anywhere else.*'
+        arg_refcount_origin = sys.getrefcount(arg)
+        ac_tester.gh_99233_refcount(arg)
+        arg_refcount_after = sys.getrefcount(arg)
+        self.assertEqual(arg_refcount_origin, arg_refcount_after)
+
 
 if __name__ == "__main__":
     unittest.main()

Misc/NEWS.d/next/Library/2022-11-08-11-18-51.gh-issue-64490.VcBgrN.rst

@@ -0,0 +1 @@
+Fix refcount error when arguments are packed to tuple in Argument Clinic.

Modules/_testclinic.c

@@ -892,6 +892,41 @@ keyword_only_parameter_impl(PyObject *module, PyObject *a)
 }
 
 
+/*[clinic input]
+vararg_and_posonly
+
+    a: object
+    *args: object
+    /
+
+[clinic start generated code]*/
+
+static PyObject *
+vararg_and_posonly_impl(PyObject *module, PyObject *a, PyObject *args)
+/*[clinic end generated code: output=42792f799465a14d input=defe017b19ba52e8]*/
+{
+    return pack_arguments_newref(2, a, args);
+}
+
+
+/*[clinic input]
+gh_99233_refcount
+
+    *args: object
+    /
+
+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=85f5fb47ac91a626]*/
+{
+    Py_RETURN_NONE;
+}
+
+
 static PyMethodDef tester_methods[] = {
     TEST_EMPTY_FUNCTION_METHODDEF
     OBJECTS_CONVERTER_METHODDEF
@@ -933,6 +968,8 @@ static PyMethodDef tester_methods[] = {
     POSONLY_KEYWORDS_OPT_KWONLY_OPT_METHODDEF
     POSONLY_OPT_KEYWORDS_OPT_KWONLY_OPT_METHODDEF
     KEYWORD_ONLY_PARAMETER_METHODDEF
+    VARARG_AND_POSONLY_METHODDEF
+    GH_99233_REFCOUNT_METHODDEF
     {NULL, NULL}
 };
 

Modules/clinic/_testclinic.c.h

@@ -956,7 +956,7 @@ def parser_body(prototype, *fields, declarations=''):
                         parser_code.append(normalize_snippet("""
                             %s = PyTuple_New(%s);
                             for (Py_ssize_t i = 0; i < %s; ++i) {{
-                                PyTuple_SET_ITEM(%s, i, args[%d + i]);
+                                PyTuple_SET_ITEM(%s, i, Py_NewRef(args[%d + i]));
                             }}
                             """ % (
                                 p.converter.parser_name,