diff --git a/Doc/c-api/structures.rst b/Doc/c-api/structures.rst index 987bc167c68d6c..58dd915e04f619 100644 --- a/Doc/c-api/structures.rst +++ b/Doc/c-api/structures.rst @@ -28,18 +28,52 @@ under :ref:`reference counting `. object. In a normal "release" build, it contains only the object's reference count and a pointer to the corresponding type object. Nothing is actually declared to be a :c:type:`PyObject`, but every pointer - to a Python object can be cast to a :c:expr:`PyObject*`. Access to the - members must be done by using the macros :c:macro:`Py_REFCNT` and - :c:macro:`Py_TYPE`. + to a Python object can be cast to a :c:expr:`PyObject*`. + + The members must not be accessed directly; instead use macros such as + :c:macro:`Py_REFCNT` and :c:macro:`Py_TYPE`. + + .. c:member:: Py_ssize_t ob_refcnt + + The object's reference count, as returned by :c:macro:`Py_REFCNT`. + Do not use this field directly; instead use functions and macros such as + :c:macro:`!Py_REFCNT`, :c:func:`Py_INCREF` and :c:func:`Py_DecRef`. + + The field type may be different from ``Py_ssize_t``, depending on + build configuration and platform. + + .. c:member:: PyTypeObject* ob_type + + The object's type. + Do not use this field directly; use :c:macro:`Py_TYPE` and + :c:func:`Py_SET_TYPE` instead. .. c:type:: PyVarObject - This is an extension of :c:type:`PyObject` that adds the :c:member:`~PyVarObject.ob_size` - field. This is only used for objects that have some notion of *length*. - This type does not often appear in the Python/C API. - Access to the members must be done by using the macros - :c:macro:`Py_REFCNT`, :c:macro:`Py_TYPE`, and :c:macro:`Py_SIZE`. + An extension of :c:type:`PyObject` that adds the + :c:member:`~PyVarObject.ob_size` field. + This is intended for objects that have some notion of *length*. + + As with :c:type:`!PyObject`, the members must not be accessed directly; + instead use macros such as :c:macro:`Py_SIZE`, :c:macro:`Py_REFCNT` and + :c:macro:`Py_TYPE`. + + .. c:member:: Py_ssize_t ob_size + + A size field, whose contents should be considered an object's internal + implementation detail. + + Do not use this field directly; use :c:macro:`Py_SIZE` instead. + + Object creation functions such as :c:func:`PyObject_NewVar` will + generally set this field to the requested size (number of items). + After creation, arbitrary values can be stored in :c:member:`!ob_size` + using :c:macro:`Py_SET_SIZE`. + + To get an object's publicly exposed length, as returned by + the Python function :py:func:`len`, use :c:func:`PyObject_Length` + instead. .. c:macro:: PyObject_HEAD @@ -103,9 +137,8 @@ under :ref:`reference counting `. Get the type of the Python object *o*. - Return a :term:`borrowed reference`. - - Use the :c:func:`Py_SET_TYPE` function to set an object type. + The returned reference is :term:`borrowed ` from *o*. + Do not release it with :c:func:`Py_DECREF` or similar. .. versionchanged:: 3.11 :c:func:`Py_TYPE()` is changed to an inline static function. @@ -122,16 +155,26 @@ under :ref:`reference counting `. .. c:function:: void Py_SET_TYPE(PyObject *o, PyTypeObject *type) - Set the object *o* type to *type*. + Set the type of object *o* to *type*, without any checking or reference + counting. + + This is a very low-level operation. + Consider instead setting the Python attribute :attr:`~object.__class__` + using :c:func:`PyObject_SetAttrString` or similar. + + Note that assigning an incompatible type can lead to undefined behavior. + + If *type* is a :ref:`heap type `, the caller must create a + new reference to it. + Similarly, if the old type of *o* is a heap type, the caller must release + a reference to that type. .. versionadded:: 3.9 .. c:function:: Py_ssize_t Py_SIZE(PyVarObject *o) - Get the size of the Python object *o*. - - Use the :c:func:`Py_SET_SIZE` function to set an object size. + Get the :c:member:`~PyVarObject.ob_size` field of *o*. .. versionchanged:: 3.11 :c:func:`Py_SIZE()` is changed to an inline static function. @@ -140,7 +183,7 @@ under :ref:`reference counting `. .. c:function:: void Py_SET_SIZE(PyVarObject *o, Py_ssize_t size) - Set the object *o* size to *size*. + Set the :c:member:`~PyVarObject.ob_size` field of *o* to *size*. .. versionadded:: 3.9 diff --git a/Doc/c-api/typeobj.rst b/Doc/c-api/typeobj.rst index af2bead3bb5004..060d6f60174b41 100644 --- a/Doc/c-api/typeobj.rst +++ b/Doc/c-api/typeobj.rst @@ -492,9 +492,9 @@ metatype) initializes :c:member:`~PyTypeObject.tp_itemsize`, which means that it type objects) *must* have the :c:member:`~PyVarObject.ob_size` field. -.. c:member:: Py_ssize_t PyObject.ob_refcnt +:c:member:`PyObject.ob_refcnt` - This is the type object's reference count, initialized to ``1`` by the + The type object's reference count is initialized to ``1`` by the ``PyObject_HEAD_INIT`` macro. Note that for :ref:`statically allocated type objects `, the type's instances (objects whose :c:member:`~PyObject.ob_type` points back to the type) do *not* count as references. But for @@ -506,7 +506,7 @@ type objects) *must* have the :c:member:`~PyVarObject.ob_size` field. This field is not inherited by subtypes. -.. c:member:: PyTypeObject* PyObject.ob_type +:c:member:`PyObject.ob_type` This is the type's type, in other words its metatype. It is initialized by the argument to the ``PyObject_HEAD_INIT`` macro, and its value should normally be @@ -532,14 +532,13 @@ type objects) *must* have the :c:member:`~PyVarObject.ob_size` field. PyVarObject Slots ----------------- -.. c:member:: Py_ssize_t PyVarObject.ob_size +:c:member:`PyVarObject.ob_size` For :ref:`statically allocated type objects `, this should be initialized to zero. For :ref:`dynamically allocated type objects `, this field has a special internal meaning. - This field should be accessed using the :c:func:`Py_SIZE()` and - :c:func:`Py_SET_SIZE()` macros. + This field should be accessed using the :c:func:`Py_SIZE()` macro. **Inheritance:** pFad - Phonifier reborn

Pfad - The Proxy pFad of © 2024 Garber Painting. All rights reserved.

Note: This service is not intended for secure transactions such as banking, social media, email, or purchasing. Use at your own risk. We assume no liability whatsoever for broken pages.

Alternative Proxies:

Alternative Proxy

pFad Proxy

pFad v3 Proxy

pFad v4 Proxy