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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"`intern_static` is not thread-safe with multiple interpreters","articleBody":"# Bug report\n\nMost static strings are interned during Python initialization in [`_PyUnicode_InitStaticStrings`](https://github.com/python/cpython/blob/5f6001130f8ada871193377954cfcfee01ef93b6/Include/internal/pycore_unicodeobject_generated.h). However, the `_Py_LATIN1_CHR` characters (code points 0-255) are static, but not interned. They may be interned later while the Python is running. This can happen for various reasons, including calls to `sys.intern`.\n\nThis isn't thread-safe: it modifies the hashtable `_PyRuntime.cached_objects.interned_strings`, which is shared across threads and interpreters, without any synchronization.\n\nIt also can break the interning identity invariant. You can have a non-static, interned 1-characters string later shadowed by the global interning of the static 1-character string.\n\n**Suggestions**\n\n* The `_PyRuntime.cached_objects.interned_strings` should be immutable. We should not modify it after `Py_Initialize()` until shutdown (i.e., `_PyUnicode_ClearInterned` called from `finalize_interp_types()`)\n* The 1-character latin1 strings should be interned. This can either be by explicitly interning them during startup, or by handling 1-character strings  specially in `intern_common`.\n\ncc @encukou @ericsnowcurrently \n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-122303\n* gh-122347\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/colesbury","@type":"Person","name":"colesbury"},"datePublished":"2024-07-25T18:29:20.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":4},"url":"https://github.com/122291/cpython/issues/122291"}