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bpo-46070: _PyGC_Fini() untracks objects (GH-30577) 

Py_EndInterpreter() now explicitly untracks all objects currently
tracked by the GC. Previously, if an object was used later by another
interpreter, calling PyObject_GC_UnTrack() on the object crashed if
the previous or the next object of the PyGC_Head structure became a
dangling pointer.
This commit is contained in:
Victor Stinner 2022-01-13 19:28:32 +01:00 committed by GitHub
parent 6be848922b
commit 1a4d1c1c9b
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5
Misc/NEWS.d/next/Core and Builtins/2022-01-13-17-58-56.bpo-46070.q8IGth.rst Normal file
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@ -0,0 +1,5 @@
:c:func:`Py_EndInterpreter` now explicitly untracks all objects currently
tracked by the GC. Previously, if an object was used later by another
interpreter, calling :c:func:`PyObject_GC_UnTrack` on the object crashed if the
previous or the next object of the :c:type:`PyGC_Head` structure became a
dangling pointer. Patch by Victor Stinner.

24
Modules/gcmodule.c
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@ -2161,12 +2161,36 @@ _PyGC_DumpShutdownStats(PyInterpreterState *interp)
}
}
static void
gc_fini_untrack(PyGC_Head *list)
{
PyGC_Head *gc;
for (gc = GC_NEXT(list); gc != list; gc = GC_NEXT(list)) {
PyObject *op = FROM_GC(gc);
_PyObject_GC_UNTRACK(op);
}
}
void
_PyGC_Fini(PyInterpreterState *interp)
{
GCState *gcstate = &interp->gc;
Py_CLEAR(gcstate->garbage);
Py_CLEAR(gcstate->callbacks);
if (!_Py_IsMainInterpreter(interp)) {
// bpo-46070: Explicitly untrack all objects currently tracked by the
// GC. Otherwise, if an object is used later by another interpreter,
// calling PyObject_GC_UnTrack() on the object crashs if the previous
// or the next object of the PyGC_Head structure became a dangling
// pointer.
for (int i = 0; i < NUM_GENERATIONS; i++) {
PyGC_Head *gen = GEN_HEAD(gcstate, i);
gc_fini_untrack(gen);
}
}
}
/* for debugging */