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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"`_interpchannels`: missing `PyErr_NoMemory()` causes `SystemErroron` OOM in `{create,close}()`","articleBody":"# Bug report\n\n### Bug description:\n\n## Bug description\nparent issue:https://github.com/python/cpython/issues/146102\nrefs:https://gist.github.com/devdanzin/d9975354c27e57f2589acfd0a777a2f1\n\nSeveral allocation failure paths in `Modules/_interpchannelsmodule.c`\nreturn `NULL` or `-1` without setting an exception.\n\nThis violates CPython's C API convention that an error return should have\nan exception set. In release builds, this can surface as:\n\n```text\nSystemError: \u003cbuilt-in function ...\u003e returned NULL without setting an exception\n```\n\ninstead of the expected `MemoryError`. In debug builds, the same paths may\ntrip `assert(PyErr_Occurred())` in `handle_channel_error()`.\n\n### Affected functions\n\nThe affected allocation sites are:\n\n| Function | Triggered via |\n|---|---|\n| `_channelends_new()` | `_channels.create()` |\n| `_channel_new()` | `_channels.create()` |\n| `_channelref_new()` | `_channels.create()` |\n| `_channel_set_closing()` | `_channels.close(send=True)` on a non-empty channel |\n\nNearby helper functions in the same file already handle this correctly by\ncalling `PyErr_NoMemory()` on allocation failure, for example:\n\n| Function |\n|---|\n| `_channelitem_new()` |\n| `_channelqueue_new()` |\n| `_channelend_new()` |\n\n### Reproducer\n\n```python\nimport _testcapi\nimport _interpchannels as _channels\nfrom concurrent.interpreters import _crossinterp\n\nREPLACE = _crossinterp._UNBOUND_CONSTANT_TO_FLAG[_crossinterp.UNBOUND]\n\n# Case 1: _channels.create()\nfor n in range(1, 20):\n    _testcapi.set_nomemory(n, n + 1)\n    try:\n        cid = _channels.create(REPLACE)\n    except MemoryError:\n        pass\n    except SystemError as exc:\n        print(f\"[create] n={n}: {type(exc).__name__}: {exc}\")\n    else:\n        _channels.destroy(cid)\n    finally:\n        _testcapi.remove_mem_hooks()\n\n# Case 2: _channels.close(send=True) on a non-empty channel\nfor n in range(1, 30):\n    cid = _channels.create(REPLACE)\n    _channels.send(cid, b\"spam\", blocking=False)\n    _testcapi.set_nomemory(n, n + 1)\n    try:\n        _channels.close(cid, send=True)\n    except MemoryError:\n        pass\n    except SystemError as exc:\n        print(f\"[close] n={n}: {type(exc).__name__}: {exc}\")\n    finally:\n        _testcapi.remove_mem_hooks()\n        try:\n            _channels.close(cid, force=True)\n        except Exception:\n            pass\n        try:\n            _channels.destroy(cid)\n        except Exception:\n            pass\n```\n\nSample output on main, CPython 3.16.0a0, macOS, release build:\n\n```text\n[create] n=1: SystemError: \u003cbuilt-in function create\u003e returned NULL without setting an exception\n[create] n=3: SystemError: \u003cbuilt-in function create\u003e returned NULL without setting an exception\n[create] n=4: SystemError: \u003cbuilt-in function create\u003e returned NULL without setting an exception\n[close] n=1: SystemError: \u003cbuilt-in function close\u003e returned NULL without setting an exception\n```\n\n### Expected behavior\n\nAll affected allocation failure paths should raise `MemoryError`, consistent\nwith nearby helper functions and CPython's general C API error handling\ncontract.\n\n### Fix\n\nCall `PyErr_NoMemory()` before returning an error from the affected\nallocation failure paths.\n\n### CPython versions tested on:\n\nCPython main branch\n\n### Operating systems tested on:\n\nmacOS\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-150214\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/lpyu001","@type":"Person","name":"lpyu001"},"datePublished":"2026-05-22T02:17:16.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":2},"url":"https://github.com/150213/cpython/issues/150213"}