lib: Tweaks to linked list macros

  * lib/linklist.h

    - Change the listnextnode, listhead and listtail macros so that
      they allow the list pointer to be NULL.

    - Modify the ALL_LIST_ELEMENTS* macros such that they clear the
      data pointer at the beginning and end of the loop.

From: Josh Bailey <joshb@google.com>
Signed-off-by: Avneesh Sachdev <avneesh@opensourcerouting.org>
Signed-off-by: David Lamparter <equinox@diac24.net>

diff --git a/lib/linklist.h b/lib/linklist.h
index cc6867cd4881356b474f8e33c70cd38cd25269d5..f0ae36256d12dc620f2b66764cd6478e8e892172 100644 (file)
--- a/lib/linklist.h
+++ b/lib/linklist.h
@@ -54,9 +54,9 @@ struct list
   void (*del) (void *val);
 };
 
-#define listnextnode(X) ((X)->next)
-#define listhead(X) ((X)->head)
-#define listtail(X) ((X)->tail)
+#define listnextnode(X) ((X) ? ((X)->next) : NULL)
+#define listhead(X) ((X) ? ((X)->head) : NULL)
+#define listtail(X) ((X) ? ((X)->tail) : NULL)
 #define listcount(X) ((X)->count)
 #define list_isempty(X) ((X)->head == NULL && (X)->tail == NULL)
 #define listgetdata(X) (assert((X)->data != NULL), (X)->data)
@@ -88,10 +88,10 @@ extern void list_add_list (struct list *, struct list *);
  * It is safe to delete the listnode using this macro.
  */
 #define ALL_LIST_ELEMENTS(list,node,nextnode,data) \
-  (node) = listhead(list); \
+  (node) = listhead(list), ((data) = NULL); \
   (node) != NULL && \
     ((data) = listgetdata(node),(nextnode) = listnextnode(node), 1); \
-  (node) = (nextnode)
+  (node) = (nextnode), ((data) = NULL)
 
 /* read-only list iteration macro.
  * Usage: as per ALL_LIST_ELEMENTS, but not safe to delete the listnode Only
@@ -100,9 +100,9 @@ extern void list_add_list (struct list *, struct list *);
  * of previous macro.
  */
 #define ALL_LIST_ELEMENTS_RO(list,node,data) \
-  (node) = listhead(list); \
+  (node) = listhead(list), ((data) = NULL);\
   (node) != NULL && ((data) = listgetdata(node), 1); \
-  (node) = listnextnode(node)
+  (node) = listnextnode(node), ((data) = NULL)
 
 /* these *do not* cleanup list nodes and referenced data, as the functions
  * do - these macros simply {de,at}tach a listnode from/to a list.