gh-128198: Add missing error checks for usages of PyIter_Next

Modules/_asynciomodule.c

@@ -3623,6 +3623,14 @@ _asyncio_all_tasks_impl(PyObject *module, PyObject *loop)
         Py_DECREF(item);
     }
     Py_DECREF(eager_iter);
+
+    /* Check if loop ended because of exception in PyIter_Next */
+    if (PyErr_Occurred()) {
+        Py_DECREF(tasks);
+        Py_DECREF(loop);
+        return NULL;
+    }
+
     int err = 0;
     ASYNCIO_STATE_LOCK(state);
     TaskObj *first = &state->asyncio_tasks.first;
@@ -3662,6 +3670,12 @@ _asyncio_all_tasks_impl(PyObject *module, PyObject *loop)
     }
     Py_DECREF(scheduled_iter);
     Py_DECREF(loop);
+
+    /* Check if loop ended because of exception in PyIter_Next */
+    if (PyErr_Occurred()) {
+        return NULL;
+    }
+
     return tasks;
 }
 

Modules/_collectionsmodule.c

@@ -1667,10 +1667,13 @@ deque_richcompare(PyObject *v, PyObject *w, int op)
     if (it2 == NULL)
         goto done;
     for (;;) {
-        x = PyIter_Next(it1);
-        if (x == NULL && PyErr_Occurred())
+        if ((x = PyIter_Next(it1)) == NULL && PyErr_Occurred()) {
             goto done;
-        y = PyIter_Next(it2);
+        }
+        if ((y = PyIter_Next(it2)) == NULL && PyErr_Occurred()) {
+            Py_XDECREF(x);
+            goto done;
+        }
         if (x == NULL || y == NULL)
             break;
         b = PyObject_RichCompareBool(x, y, Py_EQ);

Objects/frameobject.c

@@ -264,6 +264,11 @@ framelocalsproxy_merge(PyObject* self, PyObject* other)
 
     Py_DECREF(iter);
 
+    /* Check if loop ended because of exception in PyIter_Next */
+    if (PyErr_Occurred()) {
+        return -1;
+    }
+
     return 0;
 }
 

Objects/namespaceobject.c

@@ -141,6 +141,11 @@ namespace_repr(PyObject *ns)
             goto error;
     }
 
+    /* Check if loop ended because of exception in PyIter_Next */
+    if (PyErr_Occurred()) {
+        goto error;
+    }
+
     separator = PyUnicode_FromString(", ");
     if (separator == NULL)
         goto error;