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Issue #18112: PEP 442 implementation (safe object finalization).

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Antoine Pitrou 2013-07-30 19:59:21 +02:00
parent c5d95b17ac
commit 796564c27b
25 changed files with 1254 additions and 321 deletions
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49
Doc/c-api/typeobj.rst
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@ -465,6 +465,14 @@ type objects) *must* have the :attr:`ob_size` field.
:const:`Py_TPFLAGS_HAVE_VERSION_TAG`.
.. data:: Py_TPFLAGS_HAVE_FINALIZE
This bit is set when the :attr:`tp_finalize` slot is present in the
type structure.
.. versionadded:: 3.4
.. c:member:: char* PyTypeObject.tp_doc
An optional pointer to a NUL-terminated C string giving the docstring for this
@ -968,6 +976,47 @@ type objects) *must* have the :attr:`ob_size` field.
This field is not inherited; it is calculated fresh by :c:func:`PyType_Ready`.
.. c:member:: destructor PyTypeObject.tp_finalize
An optional pointer to an instance finalization function. Its signature is
:c:type:`destructor`::
void tp_finalize(PyObject *)
If :attr:`tp_finalize` is set, the interpreter calls it once when
finalizing an instance. It is called either from the garbage
collector (if the instance is part of an isolated reference cycle) or
just before the object is deallocated. Either way, it is guaranteed
to be called before attempting to break reference cycles, ensuring
that it finds the object in a sane state.
:attr:`tp_finalize` should not mutate the current exception status;
therefore, a recommended way to write a non-trivial finalizer is::
static void
local_finalize(PyObject *self)
{
PyObject *error_type, *error_value, *error_traceback;
/* Save the current exception, if any. */
PyErr_Fetch(&error_type, &error_value, &error_traceback);
/* ... */
/* Restore the saved exception. */
PyErr_Restore(error_type, error_value, error_traceback);
}
For this field to be taken into account (even through inheritance),
you must also set the :const:`Py_TPFLAGS_HAVE_FINALIZE` flags bit.
This field is inherited by subtypes.
.. versionadded:: 3.4
.. seealso:: "Safe object finalization" (:pep:`442`)
.. c:member:: PyObject* PyTypeObject.tp_cache
Unused. Not inherited. Internal use only.