Updated documentation to:

- point out the importance of reassigning data members before
  assigning thier values

- correct my missconception about return values from visitprocs. Sigh.

- mention the labor saving Py_VISIT and Py_CLEAR macros.

Doc/ext/noddy2.c

@@ -46,7 +46,7 @@ Noddy_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
 static int
 Noddy_init(Noddy *self, PyObject *args, PyObject *kwds)
 {
-    PyObject *first=NULL, *last=NULL;
+    PyObject *first=NULL, *last=NULL, *tmp;
 
     static char *kwlist[] = {"first", "last", "number", NULL};
 
@@ -56,15 +56,17 @@ Noddy_init(Noddy *self, PyObject *args, PyObject *kwds)
         return -1; 
 
     if (first) {
-        Py_XDECREF(self->first);
+        tmp = self->first;
         Py_INCREF(first);
         self->first = first;
+        Py_XDECREF(tmp);
     }
 
     if (last) {
-        Py_XDECREF(self->last);
+        tmp = self->last;
         Py_INCREF(last);
         self->last = last;
+        Py_XDECREF(tmp);
     }
 
     return 0;

Doc/ext/noddy3.c

@@ -46,25 +46,27 @@ Noddy_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
 static int
 Noddy_init(Noddy *self, PyObject *args, PyObject *kwds)
 {
-    PyObject *first=NULL, *last=NULL;
+    PyObject *first=NULL, *last=NULL, *tmp;
 
     static char *kwlist[] = {"first", "last", "number", NULL};
 
-    if (! PyArg_ParseTupleAndKeywords(args, kwds, "|OOi", kwlist, 
+    if (! PyArg_ParseTupleAndKeywords(args, kwds, "|SSi", kwlist, 
                                       &first, &last, 
                                       &self->number))
         return -1; 
 
     if (first) {
-        Py_DECREF(self->first);
+        tmp = self->first;
         Py_INCREF(first);
         self->first = first;
+        Py_DECREF(tmp);
     }
 
     if (last) {
-        Py_DECREF(self->last);
+        tmp = self->last;
         Py_INCREF(last);
         self->last = last;
+        Py_DECREF(tmp);
     }
 
     return 0;

Doc/ext/noddy4.c

@@ -11,10 +11,18 @@ typedef struct {
 static int
 Noddy_traverse(Noddy *self, visitproc visit, void *arg)
 {
-    if (self->first && visit(self->first, arg) < 0)
-        return -1;
-    if (self->last && visit(self->last, arg) < 0)
-        return -1;
+    int vret;
+
+    if (self->first) {
+        vret = visit(self->first, arg);
+        if (vret != 0)
+            return vret;
+    }
+    if (self->last) {
+        vret = visit(self->last, arg);
+        if (vret != 0)
+            return vret;
+    }
 
     return 0;
 }
@@ -22,10 +30,15 @@ Noddy_traverse(Noddy *self, visitproc visit, void *arg)
 static int 
 Noddy_clear(Noddy *self)
 {
-    Py_XDECREF(self->first);
+    PyObject *tmp;
+
+    tmp = self->first;
     self->first = NULL;
-    Py_XDECREF(self->last);
+    Py_XDECREF(tmp);
+
+    tmp = self->last;
     self->last = NULL;
+    Py_XDECREF(tmp);
 
     return 0;
 }
@@ -67,7 +80,7 @@ Noddy_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
 static int
 Noddy_init(Noddy *self, PyObject *args, PyObject *kwds)
 {
-    PyObject *first=NULL, *last=NULL;
+    PyObject *first=NULL, *last=NULL, *tmp;
 
     static char *kwlist[] = {"first", "last", "number", NULL};
 
@@ -77,15 +90,17 @@ Noddy_init(Noddy *self, PyObject *args, PyObject *kwds)
         return -1; 
 
     if (first) {
-        Py_XDECREF(self->first);
+        tmp = self->first;
         Py_INCREF(first);
         self->first = first;
+        Py_XDECREF(tmp);
     }
 
     if (last) {
-        Py_XDECREF(self->last);
+        tmp = self->last;
         Py_INCREF(last);
         self->last = last;
+        Py_XDECREF(tmp);
     }
 
     return 0;