refactor: hoist the comparison logic

Author: KowalskiThomas

Objects/listobject.c

@@ -3433,16 +3433,12 @@ list_richcompare_impl(PyObject *v, PyObject *w, int op)
     }
 
     /* Search for the first index where items are different.
-     * Keep vitem/witem alive across the break so that the final ordering
-     * comparison uses the same differing objects.
-     * This is required as PyObject_RichCompareBool may release the GIL and
-     * the list may be mutated in the meantime.
+     * We incref vitem/witem before calling PyObject_RichCompareBool, which may
+     * release the GIL and allow the list to be mutated in the meantime.
      */
-    PyObject *vitem = NULL;
-    PyObject *witem = NULL;
     for (i = 0; i < Py_SIZE(vl) && i < Py_SIZE(wl); i++) {
-        vitem = vl->ob_item[i];
-        witem = wl->ob_item[i];
+        PyObject *vitem = vl->ob_item[i];
+        PyObject *witem = wl->ob_item[i];
         if (vitem == witem) {
             continue;
         }
@@ -3456,37 +3452,30 @@ list_richcompare_impl(PyObject *v, PyObject *w, int op)
             return NULL;
         }
         if (!k) {
-            /* keep vitem/witem alive for the final comparison */
-            break;
+            /* We have a differing item -- shortcuts for EQ/NE */
+            if (op == Py_EQ) {
+                Py_DECREF(vitem);
+                Py_DECREF(witem);
+                Py_RETURN_FALSE;
+            }
+            if (op == Py_NE) {
+                Py_DECREF(vitem);
+                Py_DECREF(witem);
+                Py_RETURN_TRUE;
+            }
+            /* Compare the differing items using the proper operator */
+            PyObject *result = PyObject_RichCompare(vitem, witem, op);
+            Py_DECREF(vitem);
+            Py_DECREF(witem);
+            return result;
         }
 
         Py_DECREF(vitem);
         Py_DECREF(witem);
-        vitem = witem = NULL;
-    }
-
-    if (vitem == NULL) {
-        /* All compared elements were equal -- compare sizes */
-        Py_RETURN_RICHCOMPARE(Py_SIZE(vl), Py_SIZE(wl), op);
     }
 
-    /* We have an item that differs -- shortcuts for EQ/NE */
-    if (op == Py_EQ) {
-        Py_DECREF(vitem);
-        Py_DECREF(witem);
-        Py_RETURN_FALSE;
-    }
-    if (op == Py_NE) {
-        Py_DECREF(vitem);
-        Py_DECREF(witem);
-        Py_RETURN_TRUE;
-    }
-
-    /* Compare the differing items using the proper operator */
-    PyObject *result = PyObject_RichCompare(vitem, witem, op);
-    Py_DECREF(vitem);
-    Py_DECREF(witem);
-    return result;
+    /* All compared elements were equal -- compare sizes */
+    Py_RETURN_RICHCOMPARE(Py_SIZE(vl), Py_SIZE(wl), op);
 }
 
 static PyObject *