René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"test_perf_profiler cores periodically on macOS/aarch64","articleBody":"# Crash report\n\n### What happened?\n\nWhen running `test_perf_profiler`, the subprocess fails with what appears to be a bad memory access. \n\nThis doesn't happen every time, maybe 1 in 5 runs. I can't tell if it's load related (It doesn't seem to be from my extremely unscientific testing), but it does happen when running only this test suite (ie test_perf_profiler), or all the Python tests in parallel.  I've also seen this happen on the MacOS build bots. \n\nThis build was configured as such -\n```\n/Volumes/devel/src/cpython-fixes/configure --with-assertions --with-pydebug --enable-safety --enable-slower-safety CC=`basename $CC`\n```\nNote that the build tree (and thus cwd when running the tests) is completely outside of the source tree (I doubt this makes a difference, but who knows).\n\n```python\n% ./python -m test test_perf_profiler --header\nRaised RLIMIT_NOFILE: 256 -\u003e 1024\n== CPython 3.15.0a8+ (heads/main:4a5d25c26c0, Apr 29 2026, 16:33:39) [Clang 22.1.4 ]\n== macOS-26.4.1-arm64-arm-64bit-Mach-O little-endian\n== Python build: debug\n== cwd: /Volumes/devel/build/cpython-fixes.debug/build/test_python_worker_55492æ\n== CPU count: 12\n== encodings: locale=UTF-8 FS=utf-8\n== resources: all test resources are disabled, use -u option to unskip tests\n\nUsing random seed: 1637940672\n0:00:00 load avg: 3.66 Run 1 test sequentially in a single process\n0:00:00 load avg: 3.66 [1/1] test_perf_profiler\ntest test_perf_profiler failed -- Traceback (most recent call last):\n  File \"/Volumes/devel/src/cpython-fixes/Lib/test/test_perf_profiler.py\", line 145, in test_trampoline_works_with_forks\n    self.assertEqual(process.returncode, 0)\n    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^\nAssertionError: 139 != 0\n\n0:00:02 load avg: 3.61 [1/1/1] test_perf_profiler failed (1 failure)\n\n== Tests result: FAILURE ==\n\n1 test failed:\n    test_perf_profiler\n\nTotal duration: 2.5 sec\nTotal tests: run=14 failures=1 skipped=5\nTotal test files: run=1/1 failed=1\nResult: FAILURE\n```\n\nI codesigned the python binary for coredumping so was able to obtain this stack trace -\n\n```\n% lldb --core /cores/core.55510 ./python\n(lldb) target create \"./python\" --core \"/cores/core.55510\"\nbt\nCore file '/cores/core.55510' (arm64) was loaded.\n(lldb) bt\n* thread #1, stop reason = ESR_EC_IABORT_EL0 (fault address: 0x10510f84c)\n  * frame #0: 0x000000010510f84c\n    frame #1: 0x000000010510f84c\n    frame #2: 0x0000000104a4f4d0 python`py_trampoline_evaluator(ts=0x0000000104d8a360, frame=0x0000000105104140, throw=0) at perf_trampoline.c:450:12\n    frame #3: 0x00000001049062e4 python`_PyEval_EvalFrame(tstate=0x0000000104d8a360, frame=0x0000000105104140, throwflag=0) at pycore_ceval.h:120:12\n    frame #4: 0x0000000104906208 python`_PyEval_Vector(tstate=0x0000000104d8a360, func=0x0000000109af9790, locals=0x0000000000000000, args=0x000000016b7f2a88, argcount=0, kwnames=0x0000000000000000) at ceval.c:2124:12\n    frame #5: 0x00000001046f158c python`_PyFunction_Vectorcall(func=0x0000000109af9790, stack=0x000000016b7f2a88, nargsf=9223372036854775808, kwnames=0x0000000000000000) at call.c:413:16\n    frame #6: 0x00000001046efd80 python`_PyObject_VectorcallTstate(tstate=0x0000000104d8a360, callable=0x0000000109af9790, args=0x000000016b7f2a88, nargsf=9223372036854775808, kwnames=0x0000000000000000) at pycore_call.h:144:11\n    frame #7: 0x00000001046f112c python`PyObject_Vectorcall(callable=0x0000000109af9790, args=0x000000016b7f2a88, nargsf=9223372036854775808, kwnames=0x0000000000000000) at call.c:327:12\n    frame #8: 0x0000000104906820 python`_Py_VectorCallInstrumentation_StackRefSteal(callable=(bits = 4457469840), arguments=0x0000000105104140, total_args=0, kwnames=(bits = 1), call_instrumentation=false, frame=0x00000001051040e0, this_instr=0x0000000109c1576e, tstate=0x0000000104d8a360) at ceval.c:775:11\n    frame #9: 0x000000010490e18c python`_PyEval_EvalFrameDefault(tstate=0x0000000104d8a360, frame=0x00000001051040e0, throwflag=0) at generated_cases.c.h:1846:35\n(lldb) ^D\n\n```\n\n\n### CPython versions tested on:\n\nCPython main branch\n\n### Operating systems tested on:\n\nmacOS\n\n### Output from running 'python -VV' on the command line:\n\nPython 3.15.0a8+ (heads/main:4a5d25c26c0, Apr 29 2026, 16:33:39) [Clang 22.1.4 ]\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-150347\n* gh-150392\n* gh-150393\n* gh-150394\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/neek78","@type":"Person","name":"neek78"},"datePublished":"2026-04-29T14:44:53.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":3},"url":"https://github.com/149156/cpython/issues/149156"}