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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"GC of unclosed io.BuffererdRWPair after `.readinto` results in unraisable exception","articleBody":"# Bug report\n\n### Bug description:\n\nIn `BufferedRWPairTest.test_readinto` a `BufferedRWPair` is created but not explicitly closed which results in it being Garbage Collected (GC). During GC the destruction order often results in an unraisable exception. This can be reliably reproduced by modifying the test to end with `support.gc_collect()`. The BufferedRWPair should cleanup reliably in this case.\n\nhttps://github.com/python/cpython/blob/6bc65c30ff1fd0b581a2c93416496fc720bc442c/Lib/test/test_io/test_general.py#L2281-L2288\n\n\n```python\nWarning -- Unraisable exception\nException ignored while finalizing file \u003c_io.BufferedRWPair object at 0x7fd9d7577950\u003e:\nTraceback (most recent call last):\n  File \"\u003ccheckout_dir\u003e/cpython/Lib/test/support/__init__.py\", line 837, in gc_collect\n    gc.collect()\n    ~~~~~~~~~~^^\nValueError: flush of closed file\nWarning -- Unraisable exception\nException ignored while finalizing file \u003c_io.BufferedWriter\u003e:\nTraceback (most recent call last):\n  File \"\u003ccheckout_dir\u003e/cpython/Lib/test/support/__init__.py\", line 837, in gc_collect\n    gc.collect()\n    ~~~~~~~~~~^^\nValueError: flush of closed file\n```\n\nFound while working on GH-138475\n\n### CPython versions tested on:\n\nCPython main branch\n\n### Operating systems tested on:\n\nLinux\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-138724\n* gh-138771\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/cmaloney","@type":"Person","name":"cmaloney"},"datePublished":"2025-09-09T21:21:18.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":0},"url":"https://github.com/138720/cpython/issues/138720"}