Segfault deallocating a ContextVar built with str subclass #132002
Description
Crash report
What happened?
Creating a ContextVar with an instance of a subclass of str leads to a segfault during its deallocation:
from _contextvars import ContextVar class weird_str(str): def __eq__(self, other): pass ContextVar(weird_str())Backtrace:
Program received signal SIGSEGV, Segmentation fault. contextvar_tp_clear (op=op@entry=<_contextvars.ContextVar at remote 0x7ffff7ac7150>) at Python/context.c:935 935 Py_CLEAR(self->var_name); (gdb) bt #0 contextvar_tp_clear (op=op@entry=<_contextvars.ContextVar at remote 0x7ffff7ac7150>) at Python/context.c:935 #1 0x000055555587e395 in contextvar_tp_dealloc (self=<_contextvars.ContextVar at remote 0x7ffff7ac7150>) at Python/context.c:958 #2 0x00005555556ffa08 in _Py_Dealloc (op=op@entry=<_contextvars.ContextVar at remote 0x7ffff7ac7150>) at Objects/object.c:3021 #3 0x000055555587e672 in Py_DECREF (op=<_contextvars.ContextVar at remote 0x7ffff7ac7150>, lineno=883, filename=0x555555a49efe "Python/context.c") at ./Include/refcount.h:416 #4 contextvar_new (name=<weird_str() at remote 0x7ffff7bc7260>, def=0x0) at Python/context.c:883 #5 0x000055555587e6fe in contextvar_tp_new (type=<optimized out>, args=<optimized out>, kwds=<optimized out>) at Python/context.c:928 #6 0x000055555574692f in type_call (self=<type at remote 0x555555bff380>, args=(<weird_str() at remote 0x7ffff7bc7260>,), kwds=0x0) at Objects/typeobject.c:2244 #7 0x000055555567b9a7 in _PyObject_MakeTpCall (tstate=tstate@entry=0x555555c69558 <_PyRuntime+330424>, callable=callable@entry=<type at remote 0x555555bff380>, args=args@entry=0x7fffffffd7c8, nargs=<optimized out>, keywords=keywords@entry=0x0) at Objects/call.c:242 #8 0x000055555567bdc8 in _PyObject_VectorcallTstate (tstate=0x555555c69558 <_PyRuntime+330424>, callable=<type at remote 0x555555bff380>, args=0x7fffffffd7c8, nargsf=<optimized out>, kwnames=0x0) at ./Include/internal/pycore_call.h:167 #9 0x000055555567bdf4 in PyObject_Vectorcall (callable=callable@entry=<type at remote 0x555555bff380>, args=args@entry=0x7fffffffd7c8, nargsf=<optimized out>, kwnames=kwnames@entry=0x0) at Objects/call.c:327 #10 0x000055555582f4c0 in _PyEval_EvalFrameDefault (tstate=tstate@entry=0x555555c69558 <_PyRuntime+330424>, frame=frame@entry=0x7ffff7fb0020, throwflag=throwflag@entry=0) at Python/generated_cases.c.h:1366 #11 0x000055555585cd69 in _PyEval_EvalFrame (throwflag=0, frame=0x7ffff7fb0020, tstate=0x555555c69558 <_PyRuntime+330424>) at ./Include/internal/pycore_ceval.h:119Found using fusil by @vstinner.
CPython versions tested on:
CPython main branch
Operating systems tested on:
Linux, Windows
Output from running 'python -VV' on the command line:
Python 3.14.0a6+ (heads/main:be2d2181e62, Mar 31 2025, 07:30:17) [GCC 11.4.0]