=== modified file 'Doc/c-api/structures.rst'
--- Doc/c-api/structures.rst	2008-01-19 22:08:21 +0000
+++ Doc/c-api/structures.rst	2010-11-17 12:18:12 +0000
@@ -1,95 +1,114 @@
 .. highlightlang:: c
 
 .. _common-structs:
 
 Common Object Structures
 ========================
 
 There are a large number of structures which are used in the definition of
 object types for Python.  This section describes these structures and how they
 are used.
 
-All Python objects ultimately share a small number of fields at the beginning of
-the object's representation in memory.  These are represented by the
-:ctype:`PyObject` and :ctype:`PyVarObject` types, which are defined, in turn, by
-the expansions of some macros also used, whether directly or indirectly, in the
-definition of all other Python objects.
+All Python objects ultimately share a small number of fields at the beginning
+of the object's representation in memory.  These are represented by the
+:ctype:`PyObject` and :ctype:`PyVarObject` types, which are defined, in turn,
+by the expansions of some macros also used, whether directly or indirectly, in
+the definition of all other Python objects.
 
 
 .. ctype:: PyObject
 
-   All object types are extensions of this type.  This is a type which contains the
-   information Python needs to treat a pointer to an object as an object.  In a
-   normal "release" build, it contains only the objects reference count and a
-   pointer to the corresponding type object.  It corresponds to the fields defined
-   by the expansion of the ``PyObject_HEAD`` macro.
+   All object types are extensions of this type.  This is a type which
+   contains the information Python needs to treat a pointer to an object as an
+   object.  In a normal "release" build, it contains only the object's
+   reference count and a pointer to the corresponding type object.  It
+   corresponds to the fields defined by the expansion of the ``PyObject_HEAD``
+   macro.
 
 
 .. ctype:: PyVarObject
 
-   This is an extension of :ctype:`PyObject` that adds the :attr:`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.  It corresponds to the fields defined by
-   the expansion of the ``PyObject_VAR_HEAD`` macro.
+   This is an extension of :ctype:`PyObject` that adds the :attr:`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.  It corresponds to the
+   fields defined by the expansion of the ``PyObject_VAR_HEAD`` macro.
 
 These macros are used in the definition of :ctype:`PyObject` and
 :ctype:`PyVarObject`:
 
 
 .. cmacro:: PyObject_HEAD
 
    This is a macro which expands to the declarations of the fields of the
    :ctype:`PyObject` type; it is used when declaring new types which represent
-   objects without a varying length.  The specific fields it expands to depend on
-   the definition of :cmacro:`Py_TRACE_REFS`.  By default, that macro is not
-   defined, and :cmacro:`PyObject_HEAD` expands to::
+   objects without a varying length.  The specific fields it expands to depend
+   on the definition of :cmacro:`Py_TRACE_REFS`.  By default, that macro is
+   not defined, and :cmacro:`PyObject_HEAD` expands to::
 
       Py_ssize_t ob_refcnt;
       PyTypeObject *ob_type;
 
    When :cmacro:`Py_TRACE_REFS` is defined, it expands to::
 
       PyObject *_ob_next, *_ob_prev;
       Py_ssize_t ob_refcnt;
       PyTypeObject *ob_type;
 
 
 .. cmacro:: PyObject_VAR_HEAD
 
    This is a macro which expands to the declarations of the fields of the
-   :ctype:`PyVarObject` type; it is used when declaring new types which represent
-   objects with a length that varies from instance to instance.  This macro always
-   expands to::
+   :ctype:`PyVarObject` type; it is used when declaring new types which
+   represent objects with a length that varies from instance to instance.
+   This macro always expands to::
 
       PyObject_HEAD
       Py_ssize_t ob_size;
 
    Note that :cmacro:`PyObject_HEAD` is part of the expansion, and that its own
    expansion varies depending on the definition of :cmacro:`Py_TRACE_REFS`.
 
-PyObject_HEAD_INIT
+
+.. cmacro:: PyObject_HEAD_INIT(type)
+
+   This is a macro which expands to initialization values for a new
+   :ctype:`PyObject` type.  This macro expands to::
+
+      _PyObject_EXTRA_INIT
+      1, type,
+
+
+.. cmacro:: PyVarObject_HEAD_INIT(type, size)
+
+   This is a macro which expands to initialization values for a new
+   :ctype:`PyVarObject` type, including the :attr:`ob_size` field.
+   This macro expands to::
+
+      _PyObject_EXTRA_INIT
+      1, type, size,
 
 
 .. ctype:: PyCFunction
 
-   Type of the functions used to implement most Python callables in C. Functions of
-   this type take two :ctype:`PyObject\*` parameters and return one such value.  If
-   the return value is *NULL*, an exception shall have been set.  If not *NULL*,
-   the return value is interpreted as the return value of the function as exposed
-   in Python.  The function must return a new reference.
+   Type of the functions used to implement most Python callables in C.
+   Functions of this type take two :ctype:`PyObject\*` parameters and return
+   one such value.  If the return value is *NULL*, an exception shall have
+   been set.  If not *NULL*, the return value is interpreted as the return
+   value of the function as exposed in Python.  The function must return a new
+   reference.
 
 
 .. ctype:: PyMethodDef
 
    Structure used to describe a method of an extension type.  This structure has
    four fields:
 
    +------------------+-------------+-------------------------------+
    | Field            | C Type      | Meaning                       |
    +==================+=============+===============================+
    | :attr:`ml_name`  | char \*     | name of the method            |
    +------------------+-------------+-------------------------------+
    | :attr:`ml_meth`  | PyCFunction | pointer to the C              |
    |                  |             | implementation                |
    +------------------+-------------+-------------------------------+
    | :attr:`ml_flags` | int         | flag bits indicating how the  |
@@ -104,109 +123,178 @@
 the :ctype:`PyCFunction`, the compiler will require a cast in the method table.
 Even though :ctype:`PyCFunction` defines the first parameter as
 :ctype:`PyObject\*`, it is common that the method implementation uses a the
 specific C type of the *self* object.
 
 The :attr:`ml_flags` field is a bitfield which can include the following flags.
 The individual flags indicate either a calling convention or a binding
 convention.  Of the calling convention flags, only :const:`METH_VARARGS` and
 :const:`METH_KEYWORDS` can be combined (but note that :const:`METH_KEYWORDS`
 alone is equivalent to ``METH_VARARGS | METH_KEYWORDS``). Any of the calling
 convention flags can be combined with a binding flag.
 
 
 .. data:: METH_VARARGS
 
    This is the typical calling convention, where the methods have the type
-   :ctype:`PyCFunction`. The function expects two :ctype:`PyObject\*` values.  The
-   first one is the *self* object for methods; for module functions, it has the
-   value given to :cfunc:`Py_InitModule4` (or *NULL* if :cfunc:`Py_InitModule` was
-   used).  The second parameter (often called *args*) is a tuple object
-   representing all arguments. This parameter is typically processed using
-   :cfunc:`PyArg_ParseTuple` or :cfunc:`PyArg_UnpackTuple`.
+   :ctype:`PyCFunction`. The function expects two :ctype:`PyObject\*` values.
+   The first one is the *self* object for methods; for module functions, it
+   has the value given to :cfunc:`Py_InitModule4` (or *NULL* if
+   :cfunc:`Py_InitModule` was used).  The second parameter (often called
+   *args*) is a tuple object representing all arguments. This parameter is
+   typically processed using :cfunc:`PyArg_ParseTuple` or
+   :cfunc:`PyArg_UnpackTuple`.
 
 
 .. data:: METH_KEYWORDS
 
-   Methods with these flags must be of type :ctype:`PyCFunctionWithKeywords`.  The
-   function expects three parameters: *self*, *args*, and a dictionary of all the
-   keyword arguments.  The flag is typically combined with :const:`METH_VARARGS`,
-   and the parameters are typically processed using
+   Methods with these flags must be of type :ctype:`PyCFunctionWithKeywords`.
+   The function expects three parameters: *self*, *args*, and a dictionary of
+   all the keyword arguments.  The flag is typically combined with
+   :const:`METH_VARARGS`, and the parameters are typically processed using
    :cfunc:`PyArg_ParseTupleAndKeywords`.
 
 
 .. data:: METH_NOARGS
 
    Methods without parameters don't need to check whether arguments are given if
    they are listed with the :const:`METH_NOARGS` flag.  They need to be of type
    :ctype:`PyCFunction`.  When used with object methods, the first parameter is
-   typically named ``self`` and will hold a reference to the object instance.  In
-   all cases the second parameter will be *NULL*.
+   typically named ``self`` and will hold a reference to the object instance.
+   In all cases the second parameter will be *NULL*.
 
 
 .. data:: METH_O
 
    Methods with a single object argument can be listed with the :const:`METH_O`
    flag, instead of invoking :cfunc:`PyArg_ParseTuple` with a ``"O"`` argument.
    They have the type :ctype:`PyCFunction`, with the *self* parameter, and a
    :ctype:`PyObject\*` parameter representing the single argument.
 
 
 .. data:: METH_OLDARGS
 
    This calling convention is deprecated.  The method must be of type
-   :ctype:`PyCFunction`.  The second argument is *NULL* if no arguments are given,
-   a single object if exactly one argument is given, and a tuple of objects if more
-   than one argument is given.  There is no way for a function using this
-   convention to distinguish between a call with multiple arguments and a call with
-   a tuple as the only argument.
+   :ctype:`PyCFunction`.  The second argument is *NULL* if no arguments are
+   given, a single object if exactly one argument is given, and a tuple of
+   objects if more than one argument is given.  There is no way for a function
+   using this convention to distinguish between a call with multiple arguments
+   and a call with a tuple as the only argument.
 
 These two constants are not used to indicate the calling convention but the
 binding when use with methods of classes.  These may not be used for functions
 defined for modules.  At most one of these flags may be set for any given
 method.
 
 
 .. data:: METH_CLASS
 
    .. index:: builtin: classmethod
 
-   The method will be passed the type object as the first parameter rather than an
-   instance of the type.  This is used to create *class methods*, similar to what
-   is created when using the :func:`classmethod` built-in function.
+   The method will be passed the type object as the first parameter rather
+   than an instance of the type.  This is used to create *class methods*,
+   similar to what is created when using the :func:`classmethod` built-in
+   function.
 
    .. versionadded:: 2.3
 
 
 .. data:: METH_STATIC
 
    .. index:: builtin: staticmethod
 
-   The method will be passed *NULL* as the first parameter rather than an instance
-   of the type.  This is used to create *static methods*, similar to what is
-   created when using the :func:`staticmethod` built-in function.
+   The method will be passed *NULL* as the first parameter rather than an
+   instance of the type.  This is used to create *static methods*, similar to
+   what is created when using the :func:`staticmethod` built-in function.
 
    .. versionadded:: 2.3
 
 One other constant controls whether a method is loaded in place of another
 definition with the same method name.
 
 
 .. data:: METH_COEXIST
 
    The method will be loaded in place of existing definitions.  Without
    *METH_COEXIST*, the default is to skip repeated definitions.  Since slot
-   wrappers are loaded before the method table, the existence of a *sq_contains*
-   slot, for example, would generate a wrapped method named :meth:`__contains__`
-   and preclude the loading of a corresponding PyCFunction with the same name.
-   With the flag defined, the PyCFunction will be loaded in place of the wrapper
-   object and will co-exist with the slot.  This is helpful because calls to
-   PyCFunctions are optimized more than wrapper object calls.
+   wrappers are loaded before the method table, the existence of a
+   *sq_contains* slot, for example, would generate a wrapped method named
+   :meth:`__contains__` and preclude the loading of a corresponding
+   PyCFunction with the same name.  With the flag defined, the PyCFunction
+   will be loaded in place of the wrapper object and will co-exist with the
+   slot.  This is helpful because calls to PyCFunctions are optimized more
+   than wrapper object calls.
 
    .. versionadded:: 2.4
 
 
+.. ctype:: PyMemberDef
+
+   Structure which describes an attribute of a type which corresponds to a C
+   struct member.  Its fields are:
+
+   +------------------+-------------+-------------------------------+
+   | Field            | C Type      | Meaning                       |
+   +==================+=============+===============================+
+   | :attr:`name`     | char \*     | name of the member            |
+   +------------------+-------------+-------------------------------+
+   | :attr:`type`     | int         | the type of the member in the |
+   |                  |             | C struct                      |
+   +------------------+-------------+-------------------------------+
+   | :attr:`offset`   | Py_ssize_t  | the offset in bytes that the  |
+   |                  |             | member is located on the      |
+   |                  |             | type's object struct          |
+   +------------------+-------------+-------------------------------+
+   | :attr:`flags`    | int         | flag bits indicating if the   |
+   |                  |             | field should be read-only or  |
+   |                  |             | writable                      |
+   +------------------+-------------+-------------------------------+
+   | :attr:`doc`      | char \*     | points to the contents of the |
+   |                  |             | docstring                     |
+   +------------------+-------------+-------------------------------+
+
+   :attr:`type` can be one of many ``T_`` macros corresponding to various C
+   types.  When the member is accessed in Python, it will be converted to the
+   equivalent Python type.
+
+   =============== ==================
+   Macro name      C type
+   =============== ==================
+   T_SHORT         short
+   T_INT           int
+   T_LONG          long
+   T_FLOAT         float
+   T_DOUBLE        double
+   T_STRING        char \*
+   T_OBJECT        PyObject \*
+   T_OBJECT_EX     PyObject \*
+   T_CHAR          char
+   T_BYTE          char
+   T_UBYTE         unsigned char
+   T_UINT          unsigned int
+   T_USHORT        unsigned short
+   T_ULONG         unsigned long
+   T_BOOL          char
+   T_LONGLONG      long long
+   T_ULONGLONG     unsigned long long
+   T_PYSSIZET      Py_ssize_t
+   =============== ==================
+
+   :cmacro:`T_OBJECT` and :cmacro:`T_OBJECT_EX` differ in that
+   :cmacro:`T_OBJECT` returns ``None`` if the member is *NULL* and
+   :cmacro:`T_OBJECT_EX` raises an :exc:`AttributeError`.  Try to use
+   :cmacro:`T_OBJECT_EX` over :cmacro:`T_OBJECT` because :cmacro:`T_OBJECT_EX`
+   handles use of the :keyword:`del` statement on that attribute more correctly
+   than :cmacro:`T_OBJECT`.
+
+   :attr:`flags` can be 0 for write and read access or :cmacro:`READONLY` for
+   read-only access.  Using :cmacro:`T_STRING` for :attr:`type` implies
+   :cmacro:`READONLY`.  Only :cmacro:`T_OBJECT` and :cmacro:`T_OBJECT_EX`
+   members can be deleted.  (They are set to *NULL*).
+
+
 .. cfunction:: PyObject* Py_FindMethod(PyMethodDef table[], PyObject *ob, char *name)
 
-   Return a bound method object for an extension type implemented in C.  This can
-   be useful in the implementation of a :attr:`tp_getattro` or :attr:`tp_getattr`
-   handler that does not use the :cfunc:`PyObject_GenericGetAttr` function.
+   Return a bound method object for an extension type implemented in C.  This
+   can be useful in the implementation of a :attr:`tp_getattro` or
+   :attr:`tp_getattr` handler that does not use the
+   :cfunc:`PyObject_GenericGetAttr` function.

