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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Memory leak in test_sys with subinterpreters creation (AddressSanitizer detection)","articleBody":"# Bug report\n\n### Bug description:\n\n**Bug Description:**\n\nI've discovered a memory leak when running `test_sys` with AddressSanitizer enabled. The leak occurs during subinterpreter creation and the allocated memory is never freed.\n\n**Environment:**\n- CPython versions affected: **3.14 and 3.15 (main branch)**\n- Operating System: Linux (Ubuntu-based)\n- Build configuration:\n```bash\nCC=clang CXX=clang++ ./configure \\\n    --disable-optimizations \\\n    --with-valgrind \\\n    --with-pydebug \\\n    --enable-pystats \\\n    --with-address-sanitizer\n```\n\n**Steps to Reproduce:**\n\n1. Build CPython with the configuration above (tested on both 3.14 and main branches)\n2. Run: `./python -m test test_sys`\n3. Observe AddressSanitizer output at the end\n\n**Expected Behavior:**\nNo memory leaks should be detected by AddressSanitizer.\n\n**Actual Behavior:**\nAddressSanitizer reports approximately 4.5 MB leaked across 20 allocations. All allocations trace back to `_PyInterpreterState_New` → `alloc_interpreter` → `_PyMem_DebugRawCalloc`.\n\nThe test itself passes successfully, but the leak persists:\n```\n== Tests result: SUCCESS ==\n1 test OK.\n=================================================================\nERROR: LeakSanitizer: detected memory leaks\n```\n\n**Reproduction on Multiple Versions:**\n- **3.14 branch**: 4.5 MB leaked (4517100 bytes in 20 allocations)\n- **3.15 (main)**: 4.5 MB leaked (4516460 bytes in 20 allocations)\n\n**Additional Context:**\n\nThe leak appears to be related to subinterpreter lifecycle management. The stack trace shows memory is allocated through:\n- `interp_create` (Modules/_interpretersmodule.c)\n- `_PyXI_NewInterpreter` (Python/crossinterp.c:3204)\n- `Py_NewInterpreterFromConfig` (Python/pylifecycle.c)\n- `new_interpreter` (Python/pylifecycle.c)\n- `_PyInterpreterState_New` (Python/pystate.c)\n- `alloc_interpreter` (Python/pystate.c)\n\nThis issue appears to be related to #110411, which remains open with the latest report from August 2025 stating \"This is still a problem in 3.13.7 and 3.14.0rc2\". Issue #113055 was closed as resolved in February 2025, but the leak still occurs on current 3.14 and main branches.\n\n\u003cdetails\u003e\n\u003csummary\u003eComplete AddressSanitizer Output (3.15 main branch)\u003c/summary\u003e\n\n```\n➜  main git:(main) sudo ./build/main/python -m test test_sys\nUsing random seed: 1335876681\n0:00:00 load avg: 25.72 Run 1 test sequentially in a single process\n0:00:00 load avg: 25.72 [1/1] test_sys\n0:00:20 load avg: 27.57 [1/1] test_sys passed\n\n== Tests result: SUCCESS ==\n\n1 test OK.\n\nTotal duration: 20.6 sec\nTotal tests: run=92 skipped=6\nTotal test files: run=1/1\nResult: SUCCESS\n\n=================================================================\n==544756==ERROR: LeakSanitizer: detected memory leaks\n\nDirect leak of 4290637 byte(s) in 19 object(s) allocated from:\n    #0 0x5c153a3eef9d in calloc (/home/shamil/oss/cpython/main/build/main/python+0x33bf9d) (BuildId: c97dc91acec24b8d7d7a9344676b1bb0726ae568)\n    #1 0x5c153a777a5e in _PyMem_DebugRawAlloc /home/shamil/oss/cpython/main/build/main/../../Objects/obmalloc.c:2884:24\n    #2 0x5c153a777a5e in _PyMem_DebugRawCalloc /home/shamil/oss/cpython/main/build/main/../../Objects/obmalloc.c:2929:12\n    #3 0x5c153abd8578 in alloc_interpreter /home/shamil/oss/cpython/main/build/main/../../Python/pystate.c:462:17\n    #4 0x5c153abd8578 in _PyInterpreterState_New /home/shamil/oss/cpython/main/build/main/../../Python/pystate.c:660:18\n    #5 0x5c153ab8e818 in new_interpreter /home/shamil/oss/cpython/main/build/main/../../Python/pylifecycle.c:2425:14\n    #6 0x5c153ab8e592 in Py_NewInterpreterFromConfig /home/shamil/oss/cpython/main/build/main/../../Python/pylifecycle.c:2521:12\n    #7 0x5c153aab1b58 in _PyXI_NewInterpreter /home/shamil/oss/cpython/main/build/main/../../Python/crossinterp.c:3204:23\n    #8 0x726f325c23ae in _interpreters_create_impl /home/shamil/oss/cpython/main/build/main/../../Modules/_interpretersmodule.c:880:13\n    #9 0x726f325c23ae in _interpreters_create /home/shamil/oss/cpython/main/build/main/../../Modules/clinic/_interpretersmodule.c.h:91:20\n    #10 0x5c153a5e91c2 in _PyObject_VectorcallTstate /home/shamil/oss/cpython/main/build/main/../../Include/internal/pycore_call.h:169:11\n    #11 0x5c153aa11ff6 in _PyEval_EvalFrameDefault /home/shamil/oss/cpython/main/build/main/../../Python/generated_cases.c.h:3188:35\n    [... rest of stack trace truncated for brevity ...]\n\nDirect leak of 225823 byte(s) in 1 object(s) allocated from:\n    #0 0x5c153a3eef9d in calloc (/home/shamil/oss/cpython/main/build/main/python+0x33bf9d) (BuildId: c97dc91acec24b8d7d7a9344676b1bb0726ae568)\n    #1 0x5c153a777a5e in _PyMem_DebugRawAlloc /home/shamil/oss/cpython/main/build/main/../../Objects/obmalloc.c:2884:24\n    #2 0x5c153a777a5e in _PyMem_DebugRawCalloc /home/shamil/oss/cpython/main/build/main/../../Objects/obmalloc.c:2929:12\n    #3 0x5c153abd8578 in alloc_interpreter /home/shamil/oss/cpython/main/build/main/../../Python/pystate.c:462:17\n    #4 0x5c153abd8578 in _PyInterpreterState_New /home/shamil/oss/cpython/main/build/main/../../Python/pystate.c:660:18\n    [... rest of stack trace truncated for brevity ...]\n\nSUMMARY: AddressSanitizer: 4516460 byte(s) leaked in 20 allocation(s).\n```\n\u003c/details\u003e\n\n\u003cdetails\u003e\n\u003csummary\u003eComplete AddressSanitizer Output (3.14 branch)\u003c/summary\u003e\n\n```\n➜  3.14 git:(3.14) sudo ./python -m test test_sys\nUsing random seed: 641571276\n0:00:00 load avg: 2.97 Run 1 test sequentially in a single process\n0:00:00 load avg: 2.97 [1/1] test_sys\n0:00:06 load avg: 2.66 [1/1] test_sys passed\n\n== Tests result: SUCCESS ==\n\n1 test OK.\n\nTotal duration: 6.7 sec\nTotal tests: run=97 skipped=7\nTotal test files: run=1/1\nResult: SUCCESS\n\n=================================================================\n==570353==ERROR: LeakSanitizer: detected memory leaks\n\nDirect leak of 4291245 byte(s) in 19 object(s) allocated from:\n    #0 0x5ea8303c6f8d in calloc (/home/shamil/oss/cpython/3.14/python+0x325f8d) (BuildId: bd4e3657446f867dffe5f140bfa56307be2c714a)\n    #1 0x5ea83074b5be in _PyMem_DebugRawAlloc /home/shamil/oss/cpython/3.14/Objects/obmalloc.c:2869:24\n    #2 0x5ea83074b5be in _PyMem_DebugRawCalloc /home/shamil/oss/cpython/3.14/Objects/obmalloc.c:2914:12\n    #3 0x5ea830b8f5ec in alloc_interpreter /home/shamil/oss/cpython/3.14/Python/pystate.c:570:17\n    #4 0x5ea830b8f5ec in _PyInterpreterState_New /home/shamil/oss/cpython/3.14/Python/pystate.c:757:18\n    #5 0x5ea830b5a2c8 in new_interpreter /home/shamil/oss/cpython/3.14/Python/pylifecycle.c:2313:14\n    #6 0x5ea830b5a042 in Py_NewInterpreterFromConfig /home/shamil/oss/cpython/3.14/Python/pylifecycle.c:2409:12\n    #7 0x5ea830a7cd78 in _PyXI_NewInterpreter /home/shamil/oss/cpython/3.14/Python/crossinterp.c:3204:23\n    #8 0x7be02a35a2a8 in interp_create /home/shamil/oss/cpython/3.14/./Modules/_interpretersmodule.c:862:13\n    [... rest of stack trace truncated for brevity ...]\n\nDirect leak of 225855 byte(s) in 1 object(s) allocated from:\n    #0 0x5ea8303c6f8d in calloc (/home/shamil/oss/cpython/3.14/python+0x325f8d) (BuildId: bd4e3657446f867dffe5f140bfa56307be2c714a)\n    #1 0x5ea83074b5be in _PyMem_DebugRawAlloc /home/shamil/oss/cpython/3.14/Objects/obmalloc.c:2869:24\n    #2 0x5ea83074b5be in _PyMem_DebugRawCalloc /home/shamil/oss/cpython/3.14/Objects/obmalloc.c:2914:12\n    #3 0x5ea830b8f5ec in alloc_interpreter /home/shamil/oss/cpython/3.14/Python/pystate.c:570:17\n    #4 0x5ea830b8f5ec in _PyInterpreterState_New /home/shamil/oss/cpython/3.14/Python/pystate.c:757:18\n    [... rest of stack trace truncated for brevity ...]\n\nSUMMARY: AddressSanitizer: 4517100 byte(s) leaked in 20 allocation(s).\n```\n\u003c/details\u003e\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-140111\n* gh-140118\n* gh-140140\n* gh-140148\n* gh-140261\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/ashm-dev","@type":"Person","name":"ashm-dev"},"datePublished":"2025-10-13T22:37:53.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":17},"url":"https://github.com/140067/cpython/issues/140067"}