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bpo-44348: BaseException deallocator uses trashcan (GH-28190)

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The deallocator function of the BaseException type now uses the
trashcan mecanism to prevent stack overflow. For example, when a
RecursionError instance is raised, it can be linked to another
RecursionError through the __context__ attribute or the __traceback__
attribute, and then a chain of exceptions is created. When the chain
is destroyed, nested deallocator function calls can crash with a
stack overflow if the chain is too long compared to the available
stack memory.
This commit is contained in:
Victor Stinner 2021-09-07 15:42:11 +02:00 • committed by GitHub
parent 979336de34
commit fb305092a5
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2 changed files with 14 additions and 1 deletions
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8
Misc/NEWS.d/next/Core and Builtins/2021-09-07-00-21-04.bpo-44348.f8w_Td.rst Normal file
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@ -0,0 +1,8 @@
The deallocator function of the :exc:`BaseException` type now uses the
trashcan mecanism to prevent stack overflow. For example, when a
:exc:`RecursionError` instance is raised, it can be linked to another
RecursionError through the ``__context__`` attribute or the
``__traceback__`` attribute, and then a chain of exceptions is created. When
the chain is destroyed, nested deallocator function calls can crash with a
stack overflow if the chain is too long compared to the available stack
memory. Patch by Victor Stinner.

7
Objects/exceptions.c
View file

@ -89,9 +89,14 @@ BaseException_clear(PyBaseExceptionObject *self)
static void
BaseException_dealloc(PyBaseExceptionObject *self)
{
_PyObject_GC_UNTRACK(self);
PyObject_GC_UnTrack(self);
// bpo-44348: The trashcan mecanism prevents stack overflow when deleting
// long chains of exceptions. For example, exceptions can be chained
// through the __context__ attributes or the __traceback__ attribute.
Py_TRASHCAN_BEGIN(self, BaseException_dealloc)
BaseException_clear(self);
Py_TYPE(self)->tp_free((PyObject *)self);
Py_TRASHCAN_END
}
static int