mirror of
https://github.com/python/cpython.git
synced 2024-12-01 05:45:40 +08:00
e8752d7b80
This exposes `PyUnstable_Object_ClearWeakRefsNoCallbacks` as an unstable C-API function to provide a thread-safe mechanism for clearing weakrefs without executing callbacks. Some C-API extensions need to clear weakrefs without calling callbacks, such as after running finalizers like we do in subtype_dealloc. Previously they could use `_PyWeakref_ClearRef` on each weakref, but that's not thread-safe in the free-threaded build. Co-authored-by: Petr Viktorin <encukou@gmail.com>
115 lines
4.3 KiB
ReStructuredText
115 lines
4.3 KiB
ReStructuredText
.. highlight:: c
|
|
|
|
.. _weakrefobjects:
|
|
|
|
Weak Reference Objects
|
|
----------------------
|
|
|
|
Python supports *weak references* as first-class objects. There are two
|
|
specific object types which directly implement weak references. The first is a
|
|
simple reference object, and the second acts as a proxy for the original object
|
|
as much as it can.
|
|
|
|
|
|
.. c:function:: int PyWeakref_Check(PyObject *ob)
|
|
|
|
Return non-zero if *ob* is either a reference or proxy object. This function
|
|
always succeeds.
|
|
|
|
|
|
.. c:function:: int PyWeakref_CheckRef(PyObject *ob)
|
|
|
|
Return non-zero if *ob* is a reference object. This function always succeeds.
|
|
|
|
|
|
.. c:function:: int PyWeakref_CheckProxy(PyObject *ob)
|
|
|
|
Return non-zero if *ob* is a proxy object. This function always succeeds.
|
|
|
|
|
|
.. c:function:: PyObject* PyWeakref_NewRef(PyObject *ob, PyObject *callback)
|
|
|
|
Return a weak reference object for the object *ob*. This will always return
|
|
a new reference, but is not guaranteed to create a new object; an existing
|
|
reference object may be returned. The second parameter, *callback*, can be a
|
|
callable object that receives notification when *ob* is garbage collected; it
|
|
should accept a single parameter, which will be the weak reference object
|
|
itself. *callback* may also be ``None`` or ``NULL``. If *ob* is not a
|
|
weakly referenceable object, or if *callback* is not callable, ``None``, or
|
|
``NULL``, this will return ``NULL`` and raise :exc:`TypeError`.
|
|
|
|
|
|
.. c:function:: PyObject* PyWeakref_NewProxy(PyObject *ob, PyObject *callback)
|
|
|
|
Return a weak reference proxy object for the object *ob*. This will always
|
|
return a new reference, but is not guaranteed to create a new object; an
|
|
existing proxy object may be returned. The second parameter, *callback*, can
|
|
be a callable object that receives notification when *ob* is garbage
|
|
collected; it should accept a single parameter, which will be the weak
|
|
reference object itself. *callback* may also be ``None`` or ``NULL``. If *ob*
|
|
is not a weakly referenceable object, or if *callback* is not callable,
|
|
``None``, or ``NULL``, this will return ``NULL`` and raise :exc:`TypeError`.
|
|
|
|
|
|
.. c:function:: int PyWeakref_GetRef(PyObject *ref, PyObject **pobj)
|
|
|
|
Get a :term:`strong reference` to the referenced object from a weak
|
|
reference, *ref*, into *\*pobj*.
|
|
|
|
* On success, set *\*pobj* to a new :term:`strong reference` to the
|
|
referenced object and return 1.
|
|
* If the reference is dead, set *\*pobj* to ``NULL`` and return 0.
|
|
* On error, raise an exception and return -1.
|
|
|
|
.. versionadded:: 3.13
|
|
|
|
|
|
.. c:function:: PyObject* PyWeakref_GetObject(PyObject *ref)
|
|
|
|
Return a :term:`borrowed reference` to the referenced object from a weak
|
|
reference, *ref*. If the referent is no longer live, returns ``Py_None``.
|
|
|
|
.. note::
|
|
|
|
This function returns a :term:`borrowed reference` to the referenced object.
|
|
This means that you should always call :c:func:`Py_INCREF` on the object
|
|
except when it cannot be destroyed before the last usage of the borrowed
|
|
reference.
|
|
|
|
.. deprecated-removed:: 3.13 3.15
|
|
Use :c:func:`PyWeakref_GetRef` instead.
|
|
|
|
|
|
.. c:function:: PyObject* PyWeakref_GET_OBJECT(PyObject *ref)
|
|
|
|
Similar to :c:func:`PyWeakref_GetObject`, but does no error checking.
|
|
|
|
.. deprecated-removed:: 3.13 3.15
|
|
Use :c:func:`PyWeakref_GetRef` instead.
|
|
|
|
|
|
.. c:function:: void PyObject_ClearWeakRefs(PyObject *object)
|
|
|
|
This function is called by the :c:member:`~PyTypeObject.tp_dealloc` handler
|
|
to clear weak references.
|
|
|
|
This iterates through the weak references for *object* and calls callbacks
|
|
for those references which have one. It returns when all callbacks have
|
|
been attempted.
|
|
|
|
|
|
.. c:function:: void PyUnstable_Object_ClearWeakRefsNoCallbacks(PyObject *object)
|
|
|
|
Clears the weakrefs for *object* without calling the callbacks.
|
|
|
|
This function is called by the :c:member:`~PyTypeObject.tp_dealloc` handler
|
|
for types with finalizers (i.e., :meth:`~object.__del__`). The handler for
|
|
those objects first calls :c:func:`PyObject_ClearWeakRefs` to clear weakrefs
|
|
and call their callbacks, then the finalizer, and finally this function to
|
|
clear any weakrefs that may have been created by the finalizer.
|
|
|
|
In most circumstances, it's more appropriate to use
|
|
:c:func:`PyObject_ClearWeakRefs` to clear weakrefs instead of this function.
|
|
|
|
.. versionadded:: 3.13
|