diff --git a/common/attrlist.c b/common/attrlist.c
index cb0833bc..53217754 100644
--- a/common/attrlist.c
+++ b/common/attrlist.c
@@ -9,6 +9,7 @@ The list is kept sorted in increasing order by start position. Whether or not th
 Overlapping attributes are not allowed; if an attribute is added that conflicts with an existing one, the existing one is removed.
 In addition, the linked list tries to reduce fragmentation: if an attribute is added that just expands another, then there will only be one entry in alist, not two. (TODO does it really?)
 The linked list is not a ring; alist->fist->prev == NULL and alist->last->next == NULL.
+TODO verify that this disallows attributes of length zero
 */
 
 struct attr {