Birdlib: Modify lists to avoid problems with pointer aliasing rules

The old linked list implementation used some wild typecasts and required
GCC option -fno-strict-aliasing to work properly. This patch fixes that.
However, we still keep the option due to other potential problems.

(Commited by Ondrej Santiago Zajicek)

1 files changed, 15 insertions, 2 deletions

diff --git a/lib/lists.h b/lib/lists.h
index 4204cbc5..51856b05 100644
--- a/lib/lists.h
+++ b/lib/lists.h
@@ -26,10 +26,23 @@ typedef struct node {
   struct node *next, *prev;
 } node;
 
-typedef struct list {			/* In fact two overlayed nodes */
-  struct node *head, *null, *tail;
+typedef union list {			/* In fact two overlayed nodes */
+  struct {				/* Head node */
+    struct node head_node;
+    void *head_padding;
+  };
+  struct {				/* Tail node */
+    void *tail_padding;
+    struct node tail_node;
+  };
+  struct {				/* Split to separate pointers */
+    struct node *head;
+    struct node *null;
+    struct node *tail;
+  };
 } list;
 
+
 #define NODE (node *)
 #define HEAD(list) ((void *)((list).head))
 #define TAIL(list) ((void *)((list).tail))