René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Missing `PyErr_NoMemory` in `_zoneinfo` `load_data` and `ts_to_local`","articleBody":"# Crash report\n\n### What happened?\n\nIt's possible to cause assertion errors due to calls returning `NULL` on OOM in `_zoneinfo`.\n\n### Automated diagnosis:\n\nMultiple `PyMem_Malloc`/`PyMem_Calloc` calls in `load_data` (including `ts_to_local` at line 2130) return `NULL` on OOM and goto `error` without setting an exception. The caller returns `NULL` without exception → assertion failure.\n\nFile: `Modules/_zoneinfo.c`, lines 1029-1137 (`load_data`), 2130 (`ts_to_local`)\n\nMRE for `load_data`:\n```python\nimport _testcapi, sys\n\nfor mod in [\"zoneinfo\", \"_zoneinfo\"]:\n    if mod in sys.modules:\n        del sys.modules[mod]\n\nfor n in range(1, 50):\n    for mod in [\"zoneinfo\", \"_zoneinfo\"]:\n        if mod in sys.modules:\n            del sys.modules[mod]\n    print(n)\n    _testcapi.set_nomemory(n, 0)\n    try:\n        from zoneinfo import ZoneInfo\n        z = ZoneInfo(\"UTC\")\n        _testcapi.remove_mem_hooks()\n        break\n    except MemoryError:\n        _testcapi.remove_mem_hooks()\n```\n\nMRE for `ts_to_local`:\n```python\nimport _testcapi\nfrom zoneinfo import ZoneInfo\n\n# Warm up imports — we only want OOM during zone construction\n_ = ZoneInfo(\"UTC\")\ndel _\n\n# Clear cache so America/New_York gets re-loaded from TZif data\nZoneInfo.clear_cache()\n\n# Persistent failure from allocation #9 onward.\n# Early allocs (import machinery, arg parsing) succeed;\n# the PyMem_Malloc in load_data/ts_to_local fails.\n_testcapi.set_nomemory(9, 0)\n\nz = ZoneInfo(\"America/New_York\")  # crashes: assertion `obj != NULL'\n```\n\nBacktrace:\n```\npython: ./Include/internal/pycore_stackref.h:554: _PyStackRef PyStackRef_FromPyObjectSteal(PyObject *): Assertion `obj != NULL' failed.\n\nProgram received signal SIGABRT, Aborted.\n\n#0  __pthread_kill_implementation (threadid=\u003coptimized out\u003e, signo=6, no_tid=0) at ./nptl/pthread_kill.c:44\n#1  __pthread_kill_internal (threadid=\u003coptimized out\u003e, signo=6) at ./nptl/pthread_kill.c:89\n#2  __GI___pthread_kill (threadid=\u003coptimized out\u003e, signo=signo@entry=6) at ./nptl/pthread_kill.c:100\n#3  0x00007ffff7c45e2e in __GI_raise (sig=sig@entry=6) at ../sysdeps/posix/raise.c:26\n#4  0x00007ffff7c28888 in __GI_abort () at ./stdlib/abort.c:77\n#5  0x00007ffff7c287f0 in __assert_fail_base (fmt=\u003coptimized out\u003e, assertion=\u003coptimized out\u003e, file=\u003coptimized out\u003e, line=\u003coptimized out\u003e, function=\u003coptimized out\u003e) at ./assert/assert.c:118\n#6  0x00007ffff7c3c19f in __assert_fail (assertion=\u003coptimized out\u003e, file=\u003coptimized out\u003e, line=\u003coptimized out\u003e, function=\u003coptimized out\u003e) at ./assert/assert.c:127\n#7  0x000055555587fd55 in PyStackRef_FromPyObjectSteal (obj=\u003coptimized out\u003e) at ./Include/internal/pycore_stackref.h:554\n#8  0x0000555555842cd0 in _PyEval_EvalFrameDefault (tstate=tstate@entry=0x555555d99c08 \u003c_PyRuntime+360664\u003e, frame=\u003coptimized out\u003e, frame@entry=0x7ffff7fa70a0, throwflag=throwflag@entry=0)\n    at Python/generated_cases.c.h:292\n#9  0x000055555583f08b in _PyEval_EvalFrame (tstate=0x555555d99c08 \u003c_PyRuntime+360664\u003e, frame=0x7ffff7fa70a0, throwflag=0) at ./Include/internal/pycore_ceval.h:118\n#10 _PyEval_Vector (tstate=0x555555d99c08 \u003c_PyRuntime+360664\u003e, func=0x7ffff75e9190, locals=0x0, args=0x7fffffffb310, argcount=2, kwnames=0x0) at Python/ceval.c:2130\n#11 0x00005555556a2ebe in _PyObject_VectorcallTstate (tstate=0x555555d99c08 \u003c_PyRuntime+360664\u003e, callable=callable@entry=0x7ffff75e9190, args=args@entry=0x7fffffffb310,\n    nargsf=nargsf@entry=2, kwnames=kwnames@entry=0x0) at ./Include/internal/pycore_call.h:144\n#12 0x00005555556a625a in object_vacall (tstate=tstate@entry=0x555555d99c08 \u003c_PyRuntime+360664\u003e, base=base@entry=0x0, callable=callable@entry=0x7ffff75e9190,\n    vargs=vargs@entry=0x7fffffffb460) at Objects/call.c:823\n#13 0x00005555556a5f0b in PyObject_CallMethodObjArgs (obj=0x7ffff75b08c0, name=0x555555d57470 \u003c_PyRuntime+88384\u003e) at Objects/call.c:960\n#14 0x000055555595136b in import_find_and_load (tstate=tstate@entry=0x555555d99c08 \u003c_PyRuntime+360664\u003e, abs_name=abs_name@entry=0x7ffff74f86d0) at Python/import.c:4125\n#15 0x0000555555950f66 in PyImport_ImportModuleLevelObject (name=name@entry=0x7ffff74f86d0, globals=globals@entry=0x7ffff746a4b0, locals=locals@entry=0x7ffff746a4b0,\n    fromlist=0x7ffff7477cf0, level=level@entry=0) at Python/import.c:4241\n#16 0x00005555558f7265 in _PyEval_ImportNameWithImport (tstate=tstate@entry=0x555555d99c08 \u003c_PyRuntime+360664\u003e, import_func=0x7ffff75be9f0, globals=globals@entry=0x7ffff746a4b0,\n    locals=locals@entry=0x7ffff746a4b0, name=name@entry=0x7ffff74f86d0, fromlist=fromlist@entry=0x7ffff7477cf0, level=0x555555d49188 \u003c_PyRuntime+30296\u003e) at Python/ceval.c:2975\n#17 0x00005555558848bf in _PyEval_ImportName (tstate=tstate@entry=0x555555d99c08 \u003c_PyRuntime+360664\u003e, builtins=0x7ffff75be930, globals=0x7ffff746a4b0, locals=0x7ffff746a4b0,\n    name=0x7ffff74f86d0, fromlist=0x7ffff7477cf0, level=0x555555d49188 \u003c_PyRuntime+30296\u003e) at Python/ceval.c:2954\n#18 0x000055555586141a in _PyEval_EvalFrameDefault (tstate=tstate@entry=0x555555d99c08 \u003c_PyRuntime+360664\u003e, frame=\u003coptimized out\u003e, frame@entry=0x7ffff7fa7020, throwflag=throwflag@entry=0)\n    at Python/generated_cases.c.h:6460\n#19 0x000055555583f08b in _PyEval_EvalFrame (tstate=0x555555d99c08 \u003c_PyRuntime+360664\u003e, frame=0x7ffff7fa7020, throwflag=0) at ./Include/internal/pycore_ceval.h:118\n#20 _PyEval_Vector (tstate=tstate@entry=0x555555d99c08 \u003c_PyRuntime+360664\u003e, func=func@entry=0x7ffff7466690, locals=locals@entry=0x7ffff746a4b0, args=args@entry=0x0,\n    argcount=argcount@entry=0, kwnames=kwnames@entry=0x0) at Python/ceval.c:2130\n#21 0x000055555583ee1e in PyEval_EvalCode (co=co@entry=0x555555f3baf0, globals=globals@entry=0x7ffff746a4b0, locals=locals@entry=0x7ffff746a4b0) at Python/ceval.c:686\n#22 0x00005555559c8f8e in run_eval_code_obj (tstate=0x555555d99c08 \u003c_PyRuntime+360664\u003e, co=co@entry=0x555555f3baf0, globals=globals@entry=0x7ffff746a4b0, locals=locals@entry=0x7ffff746a4b0)\n    at Python/pythonrun.c:1368\n#23 0x00005555559c8adb in run_mod (mod=mod@entry=0x555555f43b30, filename=filename@entry=0x7ffff74e8580, globals=globals@entry=0x7ffff746a4b0, locals=locals@entry=0x7ffff746a4b0,\n    flags=0x7fffffffc950, arena=arena@entry=0x7ffff74dad40, interactive_src=0x0, generate_new_source=0) at Python/pythonrun.c:1471\n```\n\nFound using [cpython-review-toolkit](https://github.com/devdanzin/cpython-review-toolkit) with Claude Opus 4.6, using the `/cpython-review-toolkit:explore Modules/_zoneinfo.c all deep` command.\n\n\n### CPython versions tested on:\n\nCPython main branch\n\n### Operating systems tested on:\n\nLinux\n\n### Output from running 'python -VV' on the command line:\n\nPython 3.15.0a7+ (heads/main:e0f7c1097e1, Mar 17 2026, 18:10:52) [Clang 21.1.2 (2ubuntu6)]\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-146117\n* gh-146119\n* gh-146124\n* gh-146132\n* gh-146138\n* gh-146165\n* gh-146223\n* gh-146224\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/devdanzin","@type":"Person","name":"devdanzin"},"datePublished":"2026-03-17T23:23:48.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":4},"url":"https://github.com/146092/cpython/issues/146092"}