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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"test_audit_subinterpreter crashes with tracerefs enabled","articleBody":"# Crash report\n\n### What happened?\n\nTo run test: `Programs/_testembed test_audit_subinterpreter`.\n\nThe program crashes with an assert failure:\n```\n_testembed: ../Objects/object.c:196: _PyRefchain_Remove: Assertion `value == REFCHAIN_VALUE' failed.\n```\n\nStack trace:\n```\n#5  0x00007fbd32045eb2 in __GI___assert_fail (\n    assertion=assertion@entry=0x55f8c78ecded \"value == REFCHAIN_VALUE\", \n    file=file@entry=0x55f8c78ecd93 \"../Objects/object.c\", line=line@entry=196, \n    function=function@entry=0x55f8c78edba0 \u003c__PRETTY_FUNCTION__.13\u003e \"_PyRefchain_Remove\")\n    at ./assert/assert.c:101\n#6  0x000055f8c76c9999 in _PyRefchain_Remove (interp=\u003coptimized out\u003e, obj=obj@entry=0x7fbd3183d710)\n    at ../Objects/object.c:196\n#7  0x000055f8c76cb6c3 in _Py_ForgetReference (op=op@entry=0x7fbd3183d710) at ../Objects/object.c:2548\n#8  0x000055f8c76ca91d in _Py_Dealloc (op=op@entry=0x7fbd3183d710) at ../Objects/object.c:2923\n#9  0x000055f8c76b2ad4 in Py_DECREF (filename=filename@entry=0x55f8c78b4f72 \"../Include/refcount.h\", \n    lineno=lineno@entry=476, op=0x7fbd3183d710) at ../Include/refcount.h:367\n#10 0x000055f8c76b2af3 in Py_XDECREF (op=\u003coptimized out\u003e) at ../Include/refcount.h:476\n#11 0x000055f8c76b2c0f in dictkeys_decref (interp=interp@entry=0x7fbd31f6e020, \n    dk=dk@entry=0x55f8c9b29030, use_qsbr=use_qsbr@entry=false) at ../Objects/dictobject.c:459\n#12 0x000055f8c76bca24 in dict_dealloc (self=0x7fbd31765070) at ../Objects/dictobject.c:3187\n#13 0x000055f8c76ca923 in _Py_Dealloc (op=op@entry=0x7fbd31765070) at ../Objects/object.c:2925\n#14 0x000055f8c76c67ab in Py_DECREF (\n    filename=filename@entry=0x55f8c78ec613 \"../Objects/moduleobject.c\", lineno=lineno@entry=1118, \n    op=0x7fbd31765070) at ../Include/refcount.h:367\n#15 0x000055f8c76c6bdb in module_clear (self=0x7fbd31764110) at ../Objects/moduleobject.c:1118\n#16 0x000055f8c77e604a in delete_garbage (tstate=tstate@entry=0x7fbd31fa4d18, \n    gcstate=gcstate@entry=0x7fbd31f6fd08, collectable=collectable@entry=0x7ffd93cac500, \n    old=old@entry=0x7fbd31f6fd50) at ../Python/gc.c:1126\n#17 0x000055f8c77e62f7 in gc_collect_region (tstate=tstate@entry=0x7fbd31fa4d18, \n    from=from@entry=0x7fbd31f6fd50, to=to@entry=0x7fbd31f6fd50, untrack=untrack@entry=3, \n    stats=stats@entry=0x7ffd93cac5e0) at ../Python/gc.c:1585\n#18 0x000055f8c77e6790 in gc_collect_full (tstate=tstate@entry=0x7fbd31fa4d18, \n    stats=stats@entry=0x7ffd93cac5e0) at ../Python/gc.c:1498\n#19 0x000055f8c77e7070 in _PyGC_Collect (tstate=0x7fbd31fa4d18, generation=generation@entry=2, \n    reason=reason@entry=_Py_GC_REASON_SHUTDOWN) at ../Python/gc.c:1862\n#20 0x000055f8c77e70ce in _PyGC_CollectNoFail (tstate=tstate@entry=0x7fbd31fa4d18)\n    at ../Python/gc.c:1903\n#21 0x000055f8c7818408 in finalize_modules (tstate=tstate@entry=0x7fbd31fa4d18)\n    at ../Python/pylifecycle.c:1716\n#22 0x000055f8c781e9f4 in Py_EndInterpreter (tstate=tstate@entry=0x7fbd31fa4d18)\n    at ../Python/pylifecycle.c:2409\n#23 0x000055f8c781ec3a in finalize_subinterpreters () at ../Python/pylifecycle.c:2484\n#24 0x000055f8c781edc3 in _Py_Finalize (runtime=runtime@entry=0x55f8c7b1e000 \u003c_PyRuntime\u003e)\n    at ../Python/pylifecycle.c:2088\n#25 0x000055f8c781ef34 in Py_Finalize () at ../Python/pylifecycle.c:2216\n#26 0x000055f8c75e90ec in test_audit_subinterpreter () at ../Programs/_testembed.c:1431\n#27 0x000055f8c75ece41 in main (argc=\u003coptimized out\u003e, argv=0x7ffd93cac888)\n    at ../Programs/_testembed.c:2520\n```\n\nThe object is a string that has been interned but not immortalized.  Likely it is shared between sub-interpreters, using basic single-phase init and is therefore shared between multiple sub-interpreters.\n\n```\n(rr) p *op\n$3 = {{ob_refcnt = 0, ob_refcnt_split = {0, 0}}, ob_type = 0x55f8c7b00c40 \u003cPyUnicode_Type\u003e}\n(rr) p op\n$4 = 'time_ns'\n```\n\nThe value of `_PyRefchain_IsTraced()` is false since it is ref-traced in a different interpreter.  \n\nQuick and dirty fix for the crash:\n```\n--- a/Objects/object.c\n+++ b/Objects/object.c\n@@ -2537,6 +2537,13 @@ _Py_ForgetReference(PyObject *op)\n \n     PyInterpreterState *interp = _PyInterpreterState_GET();\n \n+    if (!_PyRefchain_IsTraced(interp, op) \u0026\u0026\n+        PyUnicode_Check(op) \u0026\u0026\n+        PyUnicode_CHECK_INTERNED(op) \u0026\u0026\n+        interp != _PyInterpreterState_Main()) {\n+        return;\n+    }\n+\n #ifdef SLOW_UNREF_CHECK\n     if (!_PyRefchain_Get(interp, op)) {\n         /* Not found */\n```\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\n_No response_\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-125314\n* gh-125709\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/nascheme","@type":"Person","name":"nascheme"},"datePublished":"2024-10-10T22:07:17.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":2},"url":"https://github.com/125286/cpython/issues/125286"}