Add commented assert statements to check that the result of

PyObject_stgdict() and PyType_stgdict() calls are non-NULL before
dereferencing the result.  Hopefully this fixes what klocwork is
complaining about.

Fix a few other nits as well.

Modules/_ctypes/_ctypes.c

@@ -152,7 +152,7 @@ StructUnionType_paramfunc(CDataObject *self)
 
 	parg->tag = 'V';
 	stgdict = PyObject_stgdict((PyObject *)self);
-	assert(stgdict);
+	assert(stgdict); /* Cannot be NULL for structure/union instances */
 	parg->pffi_type = &stgdict->ffi_type_pointer;
 	/* For structure parameters (by value), parg->value doesn't contain the structure
 	   data itself, instead parg->value.p *points* to the structure's data
@@ -328,7 +328,6 @@ CDataType_from_param(PyObject *type, PyObject *value)
 
 		/* If we got a PyCArgObject, we must check if the object packed in it
 		   is an instance of the type's dict->proto */
-//		if(dict && ob && dict->proto == (PyObject *)ob->ob_type){
 		if(dict && ob
 		   && PyObject_IsInstance(ob, dict->proto)) {
 			Py_INCREF(value);
@@ -693,6 +692,7 @@ PointerType_from_param(PyObject *type, PyObject *value)
  		   the item types are the same.
  		*/
  		StgDictObject *v = PyObject_stgdict(value);
+		assert(v); /* Cannot be NULL for pointer or array objects */
  		if (PyObject_IsSubclass(v->proto, typedict->proto)) {
   			Py_INCREF(value);
   			return value;
@@ -1154,7 +1154,9 @@ c_wchar_p_from_param(PyObject *type, PyObject *value)
 	if (ArrayObject_Check(value) || PointerObject_Check(value)) {
 		/* c_wchar array instance or pointer(c_wchar(...)) */
 		StgDictObject *dt = PyObject_stgdict(value);
-		StgDictObject *dict = dt && dt->proto ? PyType_stgdict(dt->proto) : NULL;
+		StgDictObject *dict;
+		assert(dt); /* Cannot be NULL for pointer or array objects */
+		dict = dt && dt->proto ? PyType_stgdict(dt->proto) : NULL;
 		if (dict && (dict->setfunc == getentry("u")->setfunc)) {
 			Py_INCREF(value);
 			return value;
@@ -1216,7 +1218,9 @@ c_char_p_from_param(PyObject *type, PyObject *value)
 	if (ArrayObject_Check(value) || PointerObject_Check(value)) {
 		/* c_char array instance or pointer(c_char(...)) */
 		StgDictObject *dt = PyObject_stgdict(value);
-		StgDictObject *dict = dt && dt->proto ? PyType_stgdict(dt->proto) : NULL;
+		StgDictObject *dict;
+		assert(dt); /* Cannot be NULL for pointer or array objects */
+		dict = dt && dt->proto ? PyType_stgdict(dt->proto) : NULL;
 		if (dict && (dict->setfunc == getentry("c")->setfunc)) {
 			Py_INCREF(value);
 			return value;
@@ -1468,7 +1472,7 @@ SimpleType_paramfunc(CDataObject *self)
 	struct fielddesc *fd;
 	
 	dict = PyObject_stgdict((PyObject *)self);
-	assert(dict);
+	assert(dict); /* Cannot be NULL for CDataObject instances */
 	fmt = PyString_AsString(dict->proto);
 	assert(fmt);
 
@@ -2066,6 +2070,7 @@ static int
 CData_clear(CDataObject *self)
 {
 	StgDictObject *dict = PyObject_stgdict((PyObject *)self);
+	assert(dict); /* Cannot be NULL for CDataObject instances */
 	Py_CLEAR(self->b_objects);
 	if ((self->b_needsfree)
 	    && ((size_t)dict->size > sizeof(self->b_value)))
@@ -2363,7 +2368,9 @@ _CData_set(CDataObject *dst, PyObject *type, SETFUNC setfunc, PyObject *value,
 		StgDictObject *p1, *p2;
 		PyObject *keep;
 		p1 = PyObject_stgdict(value);
+		assert(p1); /* Cannot be NULL for array instances */
 		p2 = PyType_stgdict(type);
+		assert(p2); /* Cannot be NULL for pointer types */
 
 		if (p1->proto != p2->proto) {
 			PyErr_Format(PyExc_TypeError,
@@ -2512,7 +2519,7 @@ CFuncPtr_get_restype(CFuncPtrObject *self)
 		return self->restype;
 	}
 	dict = PyObject_stgdict((PyObject *)self);
-	assert(dict);
+	assert(dict); /* Cannot be NULL for CFuncPtrObject instances */
 	if (dict->restype) {
 		Py_INCREF(dict->restype);
 		return dict->restype;
@@ -2554,7 +2561,7 @@ CFuncPtr_get_argtypes(CFuncPtrObject *self)
 		return self->argtypes;
 	}
 	dict = PyObject_stgdict((PyObject *)self);
-	assert(dict);
+	assert(dict); /* Cannot be NULL for CFuncPtrObject instances */
 	if (dict->argtypes) {
 		Py_INCREF(dict->argtypes);
 		return dict->argtypes;
@@ -2647,8 +2654,12 @@ static int
 _validate_paramflags(PyTypeObject *type, PyObject *paramflags)
 {
 	int i, len;
-	StgDictObject *dict = PyType_stgdict((PyObject *)type);
-	PyObject *argtypes = dict->argtypes;
+	StgDictObject *dict;
+	PyObject *argtypes;
+
+	dict = PyType_stgdict((PyObject *)type);
+	assert(dict); /* Cannot be NULL. 'type' is a CFuncPtr type. */
+	argtypes = dict->argtypes;
 
 	if (paramflags == NULL || dict->argtypes == NULL)
 		return 1;
@@ -3260,7 +3271,7 @@ CFuncPtr_call(CFuncPtrObject *self, PyObject *inargs, PyObject *kwds)
 	int outmask;
 	unsigned int numretvals;
 
-	assert(dict); /* if not, it's a bug */
+	assert(dict); /* Cannot be NULL for CFuncPtrObject instances */
 	restype = self->restype ? self->restype : dict->restype;
 	converters = self->converters ? self->converters : dict->converters;
 	checker = self->checker ? self->checker : dict->checker;
@@ -3681,7 +3692,7 @@ Array_item(PyObject *_self, Py_ssize_t index)
 	}
 
 	stgdict = PyObject_stgdict((PyObject *)self);
-	assert(stgdict);
+	assert(stgdict); /* Cannot be NULL for array instances */
 	/* Would it be clearer if we got the item size from
 	   stgdict->proto's stgdict?
 	*/
@@ -3712,6 +3723,7 @@ Array_slice(PyObject *_self, Py_ssize_t ilow, Py_ssize_t ihigh)
 	len = ihigh - ilow;
 
 	stgdict = PyObject_stgdict((PyObject *)self);
+	assert(stgdict); /* Cannot be NULL for array object instances */
 	proto = stgdict->proto;
 	itemdict = PyType_stgdict(proto);
 	if (itemdict->getfunc == getentry("c")->getfunc) {
@@ -3750,6 +3762,7 @@ Array_ass_item(PyObject *_self, Py_ssize_t index, PyObject *value)
 	}
 	
 	stgdict = PyObject_stgdict((PyObject *)self);
+	assert(stgdict); /* Cannot be NULL for array object instances */
 	if (index < 0 || index >= stgdict->length) {
 		PyErr_SetString(PyExc_IndexError,
 				"invalid index");
@@ -3941,6 +3954,7 @@ Simple_set_value(CDataObject *self, PyObject *value)
 	PyObject *result;
 	StgDictObject *dict = PyObject_stgdict((PyObject *)self);
 
+	assert(dict); /* Cannot be NULL for CDataObject instances */
 	assert(dict->setfunc);
 	result = dict->setfunc(self->b_ptr, value, dict->size);
 	if (!result)
@@ -3966,8 +3980,8 @@ Simple_get_value(CDataObject *self)
 {
 	StgDictObject *dict;
 	dict = PyObject_stgdict((PyObject *)self);
+	assert(dict); /* Cannot be NULL for CDataObject instances */
 	assert(dict->getfunc);
-	dict = PyObject_stgdict((PyObject *)self);
 	return dict->getfunc(self->b_ptr, self->b_size);
 }
 
@@ -4140,11 +4154,10 @@ Pointer_item(PyObject *_self, Py_ssize_t index)
 	}
 
 	stgdict = PyObject_stgdict((PyObject *)self);
-	assert(stgdict);
-	assert(stgdict->proto);
+	assert(stgdict); /* Cannot be NULL for pointer object instances */
 	
 	proto = stgdict->proto;
-	/* XXXXXX MAKE SURE PROTO IS NOT NULL! */
+	assert(proto);
 	itemdict = PyType_stgdict(proto);
 	size = itemdict->size;
 	offset = index * itemdict->size;
@@ -4175,11 +4188,11 @@ Pointer_ass_item(PyObject *_self, Py_ssize_t index, PyObject *value)
 	}
 	
 	stgdict = PyObject_stgdict((PyObject *)self);
-	assert(stgdict);
-	assert(stgdict->proto);
+	assert(stgdict); /* Cannot be NULL fr pointer instances */
 
 	proto = stgdict->proto;
-	/* XXXXXX MAKE SURE PROTO IS NOT NULL! */
+	assert(proto);
+
 	itemdict = PyType_stgdict(proto);
 	size = itemdict->size;
 	offset = index * itemdict->size;
@@ -4200,7 +4213,7 @@ Pointer_get_contents(CDataObject *self, void *closure)
 	}
 
 	stgdict = PyObject_stgdict((PyObject *)self);
-	assert(stgdict);
+	assert(stgdict); /* Cannot be NULL fr pointer instances */
 	return CData_FromBaseObj(stgdict->proto,
 				 (PyObject *)self, 0,
 				 *(void **)self->b_ptr);
@@ -4219,7 +4232,7 @@ Pointer_set_contents(CDataObject *self, PyObject *value, void *closure)
 		return -1;
 	}
 	stgdict = PyObject_stgdict((PyObject *)self);
-	/* should have been catched in Pointer_new() */
+	assert(stgdict); /* Cannot be NULL fr pointer instances */
 	assert(stgdict->proto);
 	if (!CDataObject_Check(value) 
 	    || 0 == PyObject_IsInstance(value, stgdict->proto)) {
@@ -4295,8 +4308,11 @@ Pointer_slice(PyObject *_self, Py_ssize_t ilow, Py_ssize_t ihigh)
 	len = ihigh - ilow;
 
 	stgdict = PyObject_stgdict((PyObject *)self);
+	assert(stgdict); /* Cannot be NULL fr pointer instances */
 	proto = stgdict->proto;
+	assert(proto);
 	itemdict = PyType_stgdict(proto);
+	assert(itemdict);
 	if (itemdict->getfunc == getentry("c")->getfunc) {
 		char *ptr = *(char **)self->b_ptr;
 		return PyString_FromStringAndSize(ptr + ilow, len);