py/objtype: Eliminate __set_name__ hazard.

AJMansfield · AJMansfield · commit 7a169aa653d2 · 2025-07-16T13:35:26.000-04:00
Signed-off-by: Anson Mansfield &lt;amansfield@mantaro.com&gt;
diff --git a/py/objtype.c b/py/objtype.c
@@ -1242,20 +1242,35 @@ mp_obj_t mp_obj_new_type(qstr name, mp_obj_t bases_tuple, mp_obj_t locals_dict)
     }
 
     #if MICROPY_PY_DESCRIPTORS
-    // call __set_name__ on all entries (especially descriptors)
+    // make a list of all names of __set_name__-able attributes that won't be mutated by __set_name__ calls
+    mp_obj_list_t *setname_list = MP_OBJ_TO_PTR(mp_obj_list_make_new(&mp_type_list, 0, 0, NULL));
     for (size_t i = 0; i < locals_map->alloc; i++) {
         if (mp_map_slot_is_filled(locals_map, i)) {
             elem = &(locals_map->table[i]);
 
-            mp_obj_t set_name_method[4];
-            mp_load_method_maybe(elem->value, MP_QSTR___set_name__, set_name_method);
+            mp_obj_t set_name_method[2];
+            mp_load_method_protected(elem->value, MP_QSTR___set_name__, set_name_method, true);
             if (set_name_method[1] != MP_OBJ_NULL) {
-                set_name_method[2] = MP_OBJ_FROM_PTR(o);
-                set_name_method[3] = elem->key;
-                mp_call_method_n_kw(2, 0, set_name_method);
+                mp_obj_list_append(MP_OBJ_FROM_PTR(setname_list), elem->key);
             }
         }
     }
+
+    nlr_buf_t nlr;
+    if (nlr_push(&nlr) == 0) {
+        // then use that list to call __set_name__ on each
+        for (size_t i = 0; i < setname_list->len; i++) {
+            elem = mp_map_lookup(locals_map, setname_list->items[i], MP_MAP_LOOKUP);
+            mp_obj_t set_name_method[4] = { [2] = MP_OBJ_FROM_PTR(o), [3] = elem->key };
+            mp_load_method(elem->value, MP_QSTR___set_name__, set_name_method);
+            mp_call_method_n_kw(2, 0, set_name_method);
+        }
+        nlr_pop();
+    } else {
+        m_del_obj(&mp_type_list, setname_list);
+        nlr_raise(nlr.ret_val);
+    }
+    m_del_obj(&mp_type_list, setname_list);
     #endif
 
     return MP_OBJ_FROM_PTR(o);
