Reformat prior to editing.

Doc/c-api/gcsupport.rst

@@ -9,7 +9,8 @@ Python's support for detecting and collecting garbage which involves circular
 references requires support from object types which are "containers" for other
 objects which may also be containers.  Types which do not store references to
 other objects, or which only store references to atomic types (such as numbers
-or strings), do not need to provide any explicit support for garbage collection.
+or strings), do not need to provide any explicit support for garbage
+collection.
 
 .. An example showing the use of these interfaces can be found in "Supporting the
 .. Cycle Collector (XXX not found: ../ext/example-cycle-support.html)".
@@ -23,13 +24,14 @@ include the :const:`Py_TPFLAGS_HAVE_GC` and provide an implementation of the
 .. data:: Py_TPFLAGS_HAVE_GC
    :noindex:
 
-   Objects with a type with this flag set must conform with the rules documented
+   Objects with a type with this flag set must conform with the rules
-   here.  For convenience these objects will be referred to as container objects.
+   documented here.  For convenience these objects will be referred to as
+   container objects.
 
 Constructors for container types must conform to two rules:
 
-#. The memory for the object must be allocated using :cfunc:`PyObject_GC_New` or
+#. The memory for the object must be allocated using :cfunc:`PyObject_GC_New`
-   :cfunc:`PyObject_GC_VarNew`.
+   or :cfunc:`PyObject_GC_VarNew`.
 
 #. Once all the fields which may contain references to other containers are
    initialized, it must call :cfunc:`PyObject_GC_Track`.
@@ -49,17 +51,17 @@ Constructors for container types must conform to two rules:
 
 .. cfunction:: PyVarObject * PyObject_GC_Resize(PyVarObject *op, Py_ssize_t)
 
-   Resize an object allocated by :cfunc:`PyObject_NewVar`.  Returns the resized
+   Resize an object allocated by :cfunc:`PyObject_NewVar`.  Returns the
-   object or *NULL* on failure.
+   resized object or *NULL* on failure.
 
 
 .. cfunction:: void PyObject_GC_Track(PyObject *op)
 
-   Adds the object *op* to the set of container objects tracked by the collector.
+   Adds the object *op* to the set of container objects tracked by the
-   The collector can run at unexpected times so objects must be valid while being
+   collector.  The collector can run at unexpected times so objects must be
-   tracked.  This should be called once all the fields followed by the
+   valid while being tracked.  This should be called once all the fields
-   :attr:`tp_traverse` handler become valid, usually near the end of the
+   followed by the :attr:`tp_traverse` handler become valid, usually near the
-   constructor.
+   end of the constructor.
 
 
 .. cfunction:: void _PyObject_GC_TRACK(PyObject *op)
@@ -85,10 +87,10 @@ rules:
 .. cfunction:: void PyObject_GC_UnTrack(void *op)
 
    Remove the object *op* from the set of container objects tracked by the
-   collector.  Note that :cfunc:`PyObject_GC_Track` can be called again on this
+   collector.  Note that :cfunc:`PyObject_GC_Track` can be called again on
-   object to add it back to the set of tracked objects.  The deallocator
+   this object to add it back to the set of tracked objects.  The deallocator
-   (:attr:`tp_dealloc` handler) should call this for the object before any of the
+   (:attr:`tp_dealloc` handler) should call this for the object before any of
-   fields used by the :attr:`tp_traverse` handler become invalid.
+   the fields used by the :attr:`tp_traverse` handler become invalid.
 
 
 .. cfunction:: void _PyObject_GC_UNTRACK(PyObject *op)
@@ -101,11 +103,12 @@ The :attr:`tp_traverse` handler accepts a function parameter of this type:
 
 .. ctype:: int (*visitproc)(PyObject *object, void *arg)
 
-   Type of the visitor function passed to the :attr:`tp_traverse` handler.  The
+   Type of the visitor function passed to the :attr:`tp_traverse` handler.
-   function should be called with an object to traverse as *object* and the third
+   The function should be called with an object to traverse as *object* and
-   parameter to the :attr:`tp_traverse` handler as *arg*.  The Python core uses
+   the third parameter to the :attr:`tp_traverse` handler as *arg*.  The
-   several visitor functions to implement cyclic garbage detection; it's not
+   Python core uses several visitor functions to implement cyclic garbage
-   expected that users will need to write their own visitor functions.
+   detection; it's not expected that users will need to write their own
+   visitor functions.
 
 The :attr:`tp_traverse` handler must have the following type:
 
@@ -114,10 +117,10 @@ The :attr:`tp_traverse` handler must have the following type:
 
    Traversal function for a container object.  Implementations must call the
    *visit* function for each object directly contained by *self*, with the
-   parameters to *visit* being the contained object and the *arg* value passed to
+   parameters to *visit* being the contained object and the *arg* value passed
-   the handler.  The *visit* function must not be called with a *NULL* object
+   to the handler.  The *visit* function must not be called with a *NULL*
-   argument.  If *visit* returns a non-zero value that value should be returned
+   object argument.  If *visit* returns a non-zero value that value should be
-   immediately.
+   returned immediately.
 
 To simplify writing :attr:`tp_traverse` handlers, a :cfunc:`Py_VISIT` macro is
 provided.  In order to use this macro, the :attr:`tp_traverse` implementation
@@ -126,9 +129,9 @@ must name its arguments exactly *visit* and *arg*:
 
 .. cfunction:: void Py_VISIT(PyObject *o)
 
-   Call the *visit* callback, with arguments *o* and *arg*. If *visit* returns a
+   Call the *visit* callback, with arguments *o* and *arg*. If *visit* returns
-   non-zero value, then return it.  Using this macro, :attr:`tp_traverse` handlers
+   a non-zero value, then return it.  Using this macro, :attr:`tp_traverse`
-   look like::
+   handlers look like::
 
       static int
       my_traverse(Noddy *self, visitproc visit, void *arg)
@@ -140,14 +143,15 @@ must name its arguments exactly *visit* and *arg*:
 
    .. versionadded:: 2.4
 
-The :attr:`tp_clear` handler must be of the :ctype:`inquiry` type, or *NULL* if
+The :attr:`tp_clear` handler must be of the :ctype:`inquiry` type, or *NULL*
-the object is immutable.
+if the object is immutable.
 
 
 .. ctype:: int (*inquiry)(PyObject *self)
 
-   Drop references that may have created reference cycles.  Immutable objects do
+   Drop references that may have created reference cycles.  Immutable objects
-   not have to define this method since they can never directly create reference
+   do not have to define this method since they can never directly create
-   cycles.  Note that the object must still be valid after calling this method
+   reference cycles.  Note that the object must still be valid after calling
-   (don't just call :cfunc:`Py_DECREF` on a reference).  The collector will call
+   this method (don't just call :cfunc:`Py_DECREF` on a reference).  The
-   this method if it detects that this object is involved in a reference cycle.
+   collector will call this method if it detects that this object is involved
+   in a reference cycle.