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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Immortalize Py_EMPTY_KEYS","articleBody":"The every dict has a keys \"object\", of type `PyDictKeysObject`.  While it isn't actually a Python object, it does have a refcount, which is used to know when to free it.  `PyDictKeysObject` (and the helpers, `dictkeys_incref()` and `dictkeys_decref()`) was not updated to be immortal when the other singletons were.  When it comes to interpreter isolation, that's a problem for empty dicts.\r\n\r\nEvery empty dict shares a global, statically allocated singleton for its keys:  `Py_EMPTY_KEYS` (AKA `static PyDictKeysObject empty_keys_struct`).  This singleton is defined and used internally in dictobject.c, so we don't have the same ABI compatibility concerns that we have with object ref counts generally,\r\n\r\nOne way or another, we need to isolate `Py_EMPTY_KEYS`.  Otherwise we end up with races on the refcount.\r\n\r\ncc @eduardo-elizondo @markshannon\r\n\r\n----\r\n\r\nPossible solutions:\r\n\r\n1. update the code in dictobject.c to make `Py_EMPTY_KEYS` immortal\r\n2. move `Py_EMPTY_KEYS` to `PyInterpreterState`\r\n\r\nThe first one seems simpler.\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-104253\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/ericsnowcurrently","@type":"Person","name":"ericsnowcurrently"},"datePublished":"2023-05-06T23:49:46.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":0},"url":"https://github.com/104252/cpython/issues/104252"}