bpo-40429: Refactor super_init() (GH-19776)

Add super_init_without_args() sub-function. Hold a strong reference
to the frame code object while calling super_init_without_args().

Author: vstinner

Objects/typeobject.c

@@ -8014,6 +8014,83 @@ super_descr_get(PyObject *self, PyObject *obj, PyObject *type)
     }
 }
 
+static int
+super_init_without_args(PyFrameObject *f, PyCodeObject *co,
+                        PyTypeObject **type_p, PyObject **obj_p)
+{
+    if (co->co_argcount == 0) {
+        PyErr_SetString(PyExc_RuntimeError,
+                        "super(): no arguments");
+        return -1;
+    }
+
+    PyObject *obj = f->f_localsplus[0];
+    Py_ssize_t i, n;
+    if (obj == NULL && co->co_cell2arg) {
+        /* The first argument might be a cell. */
+        n = PyTuple_GET_SIZE(co->co_cellvars);
+        for (i = 0; i < n; i++) {
+            if (co->co_cell2arg[i] == 0) {
+                PyObject *cell = f->f_localsplus[co->co_nlocals + i];
+                assert(PyCell_Check(cell));
+                obj = PyCell_GET(cell);
+                break;
+            }
+        }
+    }
+    if (obj == NULL) {
+        PyErr_SetString(PyExc_RuntimeError,
+                        "super(): arg[0] deleted");
+        return -1;
+    }
+
+    if (co->co_freevars == NULL) {
+        n = 0;
+    }
+    else {
+        assert(PyTuple_Check(co->co_freevars));
+        n = PyTuple_GET_SIZE(co->co_freevars);
+    }
+
+    PyTypeObject *type = NULL;
+    for (i = 0; i < n; i++) {
+        PyObject *name = PyTuple_GET_ITEM(co->co_freevars, i);
+        assert(PyUnicode_Check(name));
+        if (_PyUnicode_EqualToASCIIId(name, &PyId___class__)) {
+            Py_ssize_t index = co->co_nlocals +
+                PyTuple_GET_SIZE(co->co_cellvars) + i;
+            PyObject *cell = f->f_localsplus[index];
+            if (cell == NULL || !PyCell_Check(cell)) {
+                PyErr_SetString(PyExc_RuntimeError,
+                  "super(): bad __class__ cell");
+                return -1;
+            }
+            type = (PyTypeObject *) PyCell_GET(cell);
+            if (type == NULL) {
+                PyErr_SetString(PyExc_RuntimeError,
+                  "super(): empty __class__ cell");
+                return -1;
+            }
+            if (!PyType_Check(type)) {
+                PyErr_Format(PyExc_RuntimeError,
+                  "super(): __class__ is not a type (%s)",
+                  Py_TYPE(type)->tp_name);
+                return -1;
+            }
+            break;
+        }
+    }
+    if (type == NULL) {
+        PyErr_SetString(PyExc_RuntimeError,
+                        "super(): __class__ cell not found");
+        return -1;
+    }
+
+    *type_p = type;
+    *obj_p = obj;
+    return 0;
+}
+
 static int
 super_init(PyObject *self, PyObject *args, PyObject *kwds)
 {
@@ -8030,75 +8107,19 @@ super_init(PyObject *self, PyObject *args, PyObject *kwds)
     if (type == NULL) {
         /* Call super(), without args -- fill in from __class__
            and first local variable on the stack. */
-        PyFrameObject *f;
-        Py_ssize_t i, n;
-        f = PyThreadState_GetFrame(_PyThreadState_GET());
+        PyThreadState *tstate = _PyThreadState_GET();
+        PyFrameObject *f = PyThreadState_GetFrame(tstate);
         if (f == NULL) {
             PyErr_SetString(PyExc_RuntimeError,
                             "super(): no current frame");
             return -1;
         }
-        PyCodeObject *co = PyFrame_GetCode(f);
-        Py_DECREF(co);   // use a borrowed reference
-        if (co->co_argcount == 0) {
-            PyErr_SetString(PyExc_RuntimeError,
-                            "super(): no arguments");
-            return -1;
-        }
-        obj = f->f_localsplus[0];
-        if (obj == NULL && co->co_cell2arg) {
-            /* The first argument might be a cell. */
-            n = PyTuple_GET_SIZE(co->co_cellvars);
-            for (i = 0; i < n; i++) {
-                if (co->co_cell2arg[i] == 0) {
-                    PyObject *cell = f->f_localsplus[co->co_nlocals + i];
-                    assert(PyCell_Check(cell));
-                    obj = PyCell_GET(cell);
-                    break;
-                }
-            }
-        }
-        if (obj == NULL) {
-            PyErr_SetString(PyExc_RuntimeError,
-                            "super(): arg[0] deleted");
-            return -1;
-        }
-        if (co->co_freevars == NULL)
-            n = 0;
-        else {
-            assert(PyTuple_Check(co->co_freevars));
-            n = PyTuple_GET_SIZE(co->co_freevars);
-        }
-        for (i = 0; i < n; i++) {
-            PyObject *name = PyTuple_GET_ITEM(co->co_freevars, i);
-            assert(PyUnicode_Check(name));
-            if (_PyUnicode_EqualToASCIIId(name, &PyId___class__)) {
-                Py_ssize_t index = co->co_nlocals +
-                    PyTuple_GET_SIZE(co->co_cellvars) + i;
-                PyObject *cell = f->f_localsplus[index];
-                if (cell == NULL || !PyCell_Check(cell)) {
-                    PyErr_SetString(PyExc_RuntimeError,
-                      "super(): bad __class__ cell");
-                    return -1;
-                }
-                type = (PyTypeObject *) PyCell_GET(cell);
-                if (type == NULL) {
-                    PyErr_SetString(PyExc_RuntimeError,
-                      "super(): empty __class__ cell");
-                    return -1;
-                }
-                if (!PyType_Check(type)) {
-                    PyErr_Format(PyExc_RuntimeError,
-                      "super(): __class__ is not a type (%s)",
-                      Py_TYPE(type)->tp_name);
-                    return -1;
-                }
-                break;
-            }
-        }
-        if (type == NULL) {
-            PyErr_SetString(PyExc_RuntimeError,
-                            "super(): __class__ cell not found");
+
+        PyCodeObject *code = PyFrame_GetCode(f);
+        int res = super_init_without_args(f, code, &type, &obj);
+        Py_DECREF(code);
+
+        if (res < 0) {
             return -1;
         }
     }