Description

NekoAsakura

opened on Apr 11, 2026

Issue body actions

Bug report

Bug description:

_CHECK_ATTR_CLASS calls sym_set_const(owner, type) without installing a type watcher. If the type mutates, the executor isn't invalidated.

cpython/Python/optimizer_bytecodes.c

Lines 224 to 228 in a059e85

	}
	else {
	sym_set_const(owner, type);
	}
	}

Should install a watcher like _GUARD_TYPE_VERSION does:

cpython/Python/optimizer_bytecodes.c

Lines 246 to 250 in a059e85

	if (sym_set_type_version(owner, type_version)) {
	PyType_Watch(TYPE_WATCHER_ID, (PyObject *)type);
	_Py_BloomFilter_Add(dependencies, type);
	}
	}

Found by @Fidget-Spinner in #148394 (comment)

CPython versions tested on:

CPython main branch

Operating systems tested on:

Linux

Linked PRs

• gh-148398: add type watcher in _CHECK_ATTR_CLASS #148399

Reacted by Ken Jin

Activity

1. NekoAsakura

   added

   type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

   on Apr 11, 2026
2. NekoAsakura

   added 3 commits that reference this issue on Apr 11, 2026

   pythongh-148398: add type watcher in `_CHECK_ATTR_CLASS`

   ca70b69

   pythongh-148398: add NEWS

   6ee2de7

   Merge branch 'main' into pythongh-148398/add-type-watcher

   8cb0b3c
3. picnixz

   added

   interpreter-core(Objects, Python, Grammar, and Parser dirs)(Objects, Python, Grammar, and Parser dirs)

   topic-JIT

   on Apr 11, 2026
4. NekoAsakura

   added a commit that references this issue on Apr 12, 2026

   pythongh-148398: add type watcher in `_CHECK_ATTR_CLASS`

   c1eeb13
5. Fidget-Spinner

   added a commit that references this issue on Apr 12, 2026

   gh-148398: add type watcher in `_CHECK_ATTR_CLASS` (GH-148399)

   30c698a
6. Fidget-Spinner

   closed this as completedon Apr 12, 2026
7. ljfp

   added a commit that references this issue on Apr 25, 2026

   pythongh-148398: add type watcher in `_CHECK_ATTR_CLASS` (pythonGH-14…

   8c88400

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