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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"`test_json` case `test_highly_nested_objects_decoding` fails under PGO on Clang 20","articleBody":"Building 3.15.0a1 on aarch64 macOS with Clang 20 in python-build-standalone failed during the PGO test run in `test_highly_nested_objects_decoding`:\n\n```\ncpython-3.15\u003e FAIL: test_highly_nested_objects_decoding (test.test_json.test_recursion.TestCRecursion.test_highly_nested_objects_decoding)\ncpython-3.15\u003e ----------------------------------------------------------------------\ncpython-3.15\u003e Traceback (most recent call last):\ncpython-3.15\u003e   File \"/private/var/folders/6p/k5sd5z7j31b31pq4lhn0l8d80000gn/T/tmp7fxaapg7/Python-3.15.0a1/Lib/test/test_json/test_recursion.py\", line 77, in test_highly_nested_objects_decoding\ncpython-3.15\u003e     with self.assertRaises(RecursionError):\ncpython-3.15\u003e          ~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^\ncpython-3.15\u003e AssertionError: RecursionError not raised\n```\n\nThis failure is specific to macOS, and also occurs on x86-64. I haven't reproduced it outside of `python-build-standalone` yet. Jump to https://github.com/python/cpython/issues/140125#issuecomment-3404295320 for the root cause.\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-142226\n* gh-142416\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/zanieb","@type":"Person","name":"zanieb"},"datePublished":"2025-10-14T16:02:15.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":14},"url":"https://github.com/140125/cpython/issues/140125"}