Crash report
What happened?
The following code will cause the interpreter to abort in a no-gil build:
import threading
for x in range(1000):
threading._start_joinable_thread(lambda: None)
try:
threading.settrace_all_threads(())
except Exception:
passAbort backtrace:
python: Python/legacy_tracing.c:435: is_tstate_valid: Assertion `!_PyMem_IsPtrFreed(tstate)' failed.
Thread 1 "python" received signal SIGABRT, Aborted.
__pthread_kill_implementation (no_tid=0, signo=6, threadid=140737350580032) at ./nptl/pthread_kill.c:44
44 ./nptl/pthread_kill.c: No such file or directory.
#0 __pthread_kill_implementation (no_tid=0, signo=6, threadid=140737350580032) at ./nptl/pthread_kill.c:44
#1 __pthread_kill_internal (signo=6, threadid=140737350580032) at ./nptl/pthread_kill.c:78
#2 __GI___pthread_kill (threadid=140737350580032, signo=signo@entry=6) at ./nptl/pthread_kill.c:89
#3 0x00007ffff7ce0476 in __GI_raise (sig=sig@entry=6) at ../sysdeps/posix/raise.c:26
#4 0x00007ffff7cc67f3 in __GI_abort () at ./stdlib/abort.c:79
#5 0x00007ffff7cc671b in __assert_fail_base (fmt=0x7ffff7e7b130 "%s%s%s:%u: %s%sAssertion `%s' failed.\n%n",
assertion=0x555555b53aa9 "!_PyMem_IsPtrFreed(tstate)", file=0x555555b53a91 "Python/legacy_tracing.c", line=435,
function=<optimized out>) at ./assert/assert.c:94
#6 0x00007ffff7cd7e96 in __GI___assert_fail (assertion=assertion@entry=0x555555b53aa9 "!_PyMem_IsPtrFreed(tstate)",
file=file@entry=0x555555b53a91 "Python/legacy_tracing.c", line=line@entry=435,
function=function@entry=0x555555b53ed0 <__PRETTY_FUNCTION__.18> "is_tstate_valid") at ./assert/assert.c:103
#7 0x000055555594a667 in is_tstate_valid (tstate=tstate@entry=0xdddddddddddddddd) at Python/legacy_tracing.c:435
#8 0x000055555594c0c2 in _PyEval_SetTrace (tstate=tstate@entry=0xdddddddddddddddd,
func=func@entry=0x5555559984b0 <trace_trampoline>, arg=arg@entry=()) at Python/legacy_tracing.c:596
#9 0x000055555584cd32 in PyEval_SetTraceAllThreads (func=0x5555559984b0 <trace_trampoline>, arg=()) at Python/ceval.c:2473
#10 0x000055555599698e in sys__settraceallthreads (module=<optimized out>, arg=<optimized out>) at ./Python/sysmodule.c:1187
#11 0x0000555555859272 in _PyEval_EvalFrameDefault (tstate=tstate@entry=0x555555d8a858 <_PyRuntime+361432>, frame=0x7ffff7fb0098,
frame@entry=0x7ffff7fb0020, throwflag=throwflag@entry=0) at Python/generated_cases.c.h:2271
#12 0x0000555555888b6d in _PyEval_EvalFrame (throwflag=0, frame=0x7ffff7fb0020, tstate=0x555555d8a858 <_PyRuntime+361432>)
at ./Include/internal/pycore_ceval.h:119It's also possible to sometimes segfault the interpreter with similar code, like:
import threading
threading._start_joinable_thread(lambda: None)
threading._start_joinable_thread(lambda: None)
threading._start_joinable_thread(lambda: None)
threading._start_joinable_thread(lambda: None)
for x in range(100):
try:
threading.settrace_all_threads(())
except Exception:
passSegfault backtrace:
Thread 1 "python" received signal SIGSEGV, Segmentation fault.
0x000055555594b3fb in setup_tracing (tstate=tstate@entry=0x555555e29760, func=func@entry=0x5555559984b0 <trace_trampoline>, arg=arg@entry=(), old_traceobj=old_traceobj@entry=0x7fffffffd380) at Python/legacy_tracing.c:588
588 tstate->interp->sys_tracing_threads += delta;
(gdb) bt
#0 0x000055555594b3fb in setup_tracing (tstate=tstate@entry=0x555555e29760, func=func@entry=0x5555559984b0 <trace_trampoline>,
arg=arg@entry=(), old_traceobj=old_traceobj@entry=0x7fffffffd380) at Python/legacy_tracing.c:588
#1 0x000055555594c141 in _PyEval_SetTrace (tstate=tstate@entry=0x555555e29760, func=func@entry=0x5555559984b0 <trace_trampoline>,
arg=arg@entry=()) at Python/legacy_tracing.c:610
#2 0x000055555584cd32 in PyEval_SetTraceAllThreads (func=0x5555559984b0 <trace_trampoline>, arg=()) at Python/ceval.c:2473
#3 0x000055555599698e in sys__settraceallthreads (module=<optimized out>, arg=<optimized out>) at ./Python/sysmodule.c:1187
#4 0x00005555557110b6 in cfunction_vectorcall_O (
func=<built-in method _settraceallthreads of module object at remote 0x20000259930>, args=<optimized out>,
nargsf=<optimized out>, kwnames=<optimized out>) at Objects/methodobject.c:537
#5 0x00005555556817dd in _PyObject_VectorcallTstate (tstate=0x555555d8a858 <_PyRuntime+361432>,
callable=<built-in method _settraceallthreads of module object at remote 0x20000259930>, args=0x7fffffffd708,
nargsf=9223372036854775809, kwnames=0x0) at ./Include/internal/pycore_call.h:169
#6 0x00005555556818fc in PyObject_Vectorcall (
callable=callable@entry=<built-in method _settraceallthreads of module object at remote 0x20000259930>,
args=args@entry=0x7fffffffd708, nargsf=<optimized out>, kwnames=kwnames@entry=0x0) at Objects/call.c:327
#7 0x000055555585575c in _PyEval_EvalFrameDefault (tstate=tstate@entry=0x555555d8a858 <_PyRuntime+361432>, frame=0x7ffff7fb0098,
frame@entry=0x7ffff7fb0020, throwflag=throwflag@entry=0) at Python/generated_cases.c.h:1434
#8 0x0000555555888b6d in _PyEval_EvalFrame (throwflag=0, frame=0x7ffff7fb0020, tstate=0x555555d8a858 <_PyRuntime+361432>)
at ./Include/internal/pycore_ceval.h:119Found using fusil by @vstinner.
CPython versions tested on:
CPython main branch
Operating systems tested on:
Linux
Output from running 'python -VV' on the command line:
Python 3.14.0a6+ experimental free-threading build (heads/main:0f04f2456a2, Apr 8 2025, 11:49:24) [GCC 11.4.0]
Linked PRs
Crash report
What happened?
The following code will cause the interpreter to abort in a no-gil build:
Abort backtrace:
It's also possible to sometimes segfault the interpreter with similar code, like:
Segfault backtrace:
Found using fusil by @vstinner.
CPython versions tested on:
CPython main branch
Operating systems tested on:
Linux
Output from running 'python -VV' on the command line:
Python 3.14.0a6+ experimental free-threading build (heads/main:0f04f2456a2, Apr 8 2025, 11:49:24) [GCC 11.4.0]
Linked PRs
PyEval_SetTraceAllThreads#132298