diff -r ffa851df0825 -r 2fb8b9db1c86 symbian-qemu-0.9.1-12/python-2.6.1/Doc/c-api/refcounting.rst --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/symbian-qemu-0.9.1-12/python-2.6.1/Doc/c-api/refcounting.rst Fri Jul 31 15:01:17 2009 +0100 @@ -0,0 +1,74 @@ +.. highlightlang:: c + + +.. _countingrefs: + +****************** +Reference Counting +****************** + +The macros in this section are used for managing reference counts of Python +objects. + + +.. cfunction:: void Py_INCREF(PyObject *o) + + Increment the reference count for object *o*. The object must not be *NULL*; if + you aren't sure that it isn't *NULL*, use :cfunc:`Py_XINCREF`. + + +.. cfunction:: void Py_XINCREF(PyObject *o) + + Increment the reference count for object *o*. The object may be *NULL*, in + which case the macro has no effect. + + +.. cfunction:: void Py_DECREF(PyObject *o) + + Decrement the reference count for object *o*. The object must not be *NULL*; if + you aren't sure that it isn't *NULL*, use :cfunc:`Py_XDECREF`. If the reference + count reaches zero, the object's type's deallocation function (which must not be + *NULL*) is invoked. + + .. warning:: + + The deallocation function can cause arbitrary Python code to be invoked (e.g. + when a class instance with a :meth:`__del__` method is deallocated). While + exceptions in such code are not propagated, the executed code has free access to + all Python global variables. This means that any object that is reachable from + a global variable should be in a consistent state before :cfunc:`Py_DECREF` is + invoked. For example, code to delete an object from a list should copy a + reference to the deleted object in a temporary variable, update the list data + structure, and then call :cfunc:`Py_DECREF` for the temporary variable. + + +.. cfunction:: void Py_XDECREF(PyObject *o) + + Decrement the reference count for object *o*. The object may be *NULL*, in + which case the macro has no effect; otherwise the effect is the same as for + :cfunc:`Py_DECREF`, and the same warning applies. + + +.. cfunction:: void Py_CLEAR(PyObject *o) + + Decrement the reference count for object *o*. The object may be *NULL*, in + which case the macro has no effect; otherwise the effect is the same as for + :cfunc:`Py_DECREF`, except that the argument is also set to *NULL*. The warning + for :cfunc:`Py_DECREF` does not apply with respect to the object passed because + the macro carefully uses a temporary variable and sets the argument to *NULL* + before decrementing its reference count. + + It is a good idea to use this macro whenever decrementing the value of a + variable that might be traversed during garbage collection. + + .. versionadded:: 2.4 + +The following functions are for runtime dynamic embedding of Python: +``Py_IncRef(PyObject *o)``, ``Py_DecRef(PyObject *o)``. They are +simply exported function versions of :cfunc:`Py_XINCREF` and +:cfunc:`Py_XDECREF`, respectively. + +The following functions or macros are only for use within the interpreter core: +:cfunc:`_Py_Dealloc`, :cfunc:`_Py_ForgetReference`, :cfunc:`_Py_NewReference`, +as well as the global variable :cdata:`_Py_RefTotal`. +