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[3.10] bpo-44184: Apply GH-26274 to the non-GC-type branch of subtype_dealloc (GH-27165) #27174

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Merged
merged 1 commit into from
Jul 15, 2021
Merged

[3.10] bpo-44184: Apply GH-26274 to the non-GC-type branch of subtype_dealloc (GH-27165) #27174

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14 changes: 11 additions & 3 deletions Objects/typeobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1344,14 +1344,22 @@ subtype_dealloc(PyObject *self)
/* Extract the type again; tp_del may have changed it */
type = Py_TYPE(self);

// Don't read type memory after calling basedealloc() since basedealloc()
// can deallocate the type and free its memory.
int type_needs_decref = (type->tp_flags & Py_TPFLAGS_HEAPTYPE
&& !(base->tp_flags & Py_TPFLAGS_HEAPTYPE));

/* Call the base tp_dealloc() */
assert(basedealloc);
basedealloc(self);

/* Only decref if the base type is not already a heap allocated type.
Otherwise, basedealloc should have decref'd it already */
if (type->tp_flags & Py_TPFLAGS_HEAPTYPE && !(base->tp_flags & Py_TPFLAGS_HEAPTYPE))
/* Can't reference self beyond this point. It's possible tp_del switched
our type from a HEAPTYPE to a non-HEAPTYPE, so be careful about
reference counting. Only decref if the base type is not already a heap
allocated type. Otherwise, basedealloc should have decref'd it already */
if (type_needs_decref) {
Py_DECREF(type);
}

/* Done */
return;
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