General cleanup in preparation for a bugfix: removed unused code, useless

declarations, added some comments where I had to think too hard to
understand what was happening, and changed the primary internal get/set
functions to assert they're passed objects of the correct type instead of
doing runtime tests for that (it's an internal error that "should never
happen", so it's good enough to check it only in the debug build).

Modules/arraymodule.c

-
 /* Array object implementation */
 
 /* An array is a uniform list -- all items have the same type.
@@ -19,6 +18,10 @@
 
 struct arrayobject; /* Forward */
 
+/* All possible arraydescr values are defined in the vector "descriptors"
+ * below.  That's defined later because the appropriate get and set
+ * functions aren't visible yet.
+ */
 struct arraydescr {
 	int typecode;
 	int itemsize;
@@ -36,17 +39,17 @@ staticforward PyTypeObject Arraytype;
 
 #define is_arrayobject(op) ((op)->ob_type == &Arraytype)
 
-/* Forward */
-static PyObject *newarrayobject(int, struct arraydescr *);
-#if 0
-static int getarraysize(PyObject *);
-#endif
-static PyObject *getarrayitem(PyObject *, int);
-static int setarrayitem(PyObject *, int, PyObject *);
-#if 0
-static int insarrayitem(PyObject *, int, PyObject *);
-static int addarrayitem(PyObject *, PyObject *);
-#endif
+/****************************************************************************
+Get and Set functions for each type.
+A Get function takes an arrayobject* and an integer index, returning the
+array value at that index wrapped in an appropriate PyObject*.
+A Set function takes an arrayobject, integer index, and PyObject*; sets
+the array value at that index to the raw C data extracted from the PyObject*,
+and returns 0 if successful, else nonzero on failure (PyObject* not of an
+appropriate type or value).
+Note that the basic Get and Set functions do NOT check that the index is
+in bounds; that's the responsibility of the caller.
+****************************************************************************/
 
 static PyObject *
 c_getitem(arrayobject *ap, int i)
@@ -208,7 +211,7 @@ II_setitem(arrayobject *ap, int i, PyObject *v)
 			return -1;
 		}
 		x = (unsigned long)y;
-						
+
 	}
 	if (x > UINT_MAX) {
 		PyErr_SetString(PyExc_OverflowError,
@@ -263,14 +266,14 @@ LL_setitem(arrayobject *ap, int i, PyObject *v)
 			return -1;
 		}
 		x = (unsigned long)y;
-						
+
 	}
 	if (x > ULONG_MAX) {
 		PyErr_SetString(PyExc_OverflowError,
 			"unsigned long is greater than maximum");
 		return -1;
 	}
-		
+
 	if (i >= 0)
 		((unsigned long *)ap->ob_item)[i] = x;
 	return 0;
@@ -326,7 +329,10 @@ static struct arraydescr descriptors[] = {
 	{'\0', 0, 0, 0} /* Sentinel */
 };
 /* If we ever allow items larger than double, we must change reverse()! */
-	
+
+/****************************************************************************
+Implementations of array object methods.
+****************************************************************************/
 
 static PyObject *
 newarrayobject(int size, struct arraydescr *descr)
@@ -360,26 +366,11 @@ newarrayobject(int size, struct arraydescr *descr)
 	return (PyObject *) op;
 }
 
-#if 0
-static int
-getarraysize(PyObject *op)
-{
-	if (!is_arrayobject(op)) {
-		PyErr_BadInternalCall();
-		return -1;
-	}
-	return ((arrayobject *)op) -> ob_size;
-}
-#endif
-
 static PyObject *
 getarrayitem(PyObject *op, int i)
 {
 	register arrayobject *ap;
-	if (!is_arrayobject(op)) {
-		PyErr_BadInternalCall();
-		return NULL;
-	}
+	assert(is_arrayobject(op));
 	ap = (arrayobject *)op;
 	if (i < 0 || i >= ap->ob_size) {
 		PyErr_SetString(PyExc_IndexError, "array index out of range");
@@ -417,29 +408,6 @@ ins1(arrayobject *self, int where, PyObject *v)
 	return (*self->ob_descr->setitem)(self, where, v);
 }
 
-#if 0
-static int
-insarrayitem(PyObject *op, int where, PyObject *newitem)
-{
-	if (!is_arrayobject(op)) {
-		PyErr_BadInternalCall();
-		return -1;
-	}
-	return ins1((arrayobject *)op, where, newitem);
-}
-
-static int
-addarrayitem(PyObject *op, PyObject *newitem)
-{
-	if (!is_arrayobject(op)) {
-		PyErr_BadInternalCall();
-		return -1;
-	}
-	return ins1((arrayobject *)op,
-		(int) ((arrayobject *)op)->ob_size, newitem);
-}
-#endif
-
 /* Methods */
 
 static void
@@ -648,10 +616,7 @@ array_ass_item(arrayobject *a, int i, PyObject *v)
 static int
 setarrayitem(PyObject *a, int i, PyObject *v)
 {
-	if (!is_arrayobject(a)) {
-		PyErr_BadInternalCall();
-		return -1;
-	}
+	assert(is_arrayobject(a));
 	return array_ass_item((arrayobject *)a, i, v);
 }
 
@@ -783,10 +748,10 @@ array_extend(arrayobject *self, PyObject *args)
 {
 	int size;
         PyObject    *bb;
-        
+
 	if (!PyArg_ParseTuple(args, "O:extend", &bb))
             return NULL;
-        
+
 	if (!is_arrayobject(bb)) {
 		PyErr_Format(PyExc_TypeError,
 			     "can only extend array with array (not \"%.200s\")",
@@ -951,7 +916,7 @@ array_reverse(arrayobject *self, PyObject *args)
 			memmove(q, tmp, itemsize);
 		}
 	}
-	
+
 	Py_INCREF(Py_None);
 	return Py_None;
 }
@@ -1337,9 +1302,6 @@ static PyBufferProcs array_as_buffer = {
 	(getsegcountproc)array_buffer_getsegcount,
 };
 
-
-
-
 static PyObject *
 a_array(PyObject *self, PyObject *args)
 {