diff --git a/lib/distribute.c b/lib/distribute.c
index 3d61621..906e3f6 100644
--- a/lib/distribute.c
+++ b/lib/distribute.c
@@ -134,7 +134,7 @@
 /* If two distribute-list have same value then return 1 else return
    0. This function is used by hash package. */
 static int
-distribute_cmp (struct distribute *dist1, struct distribute *dist2)
+distribute_cmp (const struct distribute *dist1, const struct distribute *dist2)
 {
   if (dist1->ifname && dist2->ifname)
     if (strcmp (dist1->ifname, dist2->ifname) == 0)
@@ -769,7 +769,7 @@
 distribute_list_init (int node)
 {
   disthash = hash_create ((unsigned int (*) (void *)) distribute_hash_make,
-                          (int (*) (void *, void *)) distribute_cmp);
+                          (int (*) (const void *, const void *)) distribute_cmp);
 
   if(node==RIP_NODE) {
     install_element (RIP_NODE, &distribute_list_all_cmd);
diff --git a/lib/hash.c b/lib/hash.c
index 76bf802..3884051 100644
--- a/lib/hash.c
+++ b/lib/hash.c
@@ -27,7 +27,7 @@
 /* Allocate a new hash.  */
 struct hash *
 hash_create_size (unsigned int size, unsigned int (*hash_key) (void *),
-                                     int (*hash_cmp) (void *, void *))
+                                     int (*hash_cmp) (const void *, const void *))
 {
   struct hash *hash;
 
@@ -46,7 +46,7 @@
 /* Allocate a new hash with default hash size.  */
 struct hash *
 hash_create (unsigned int (*hash_key) (void *), 
-             int (*hash_cmp) (void *, void *))
+             int (*hash_cmp) (const void *, const void *))
 {
   return hash_create_size (HASHTABSIZE, hash_key, hash_cmp);
 }
diff --git a/lib/hash.h b/lib/hash.h
index a6e3d59..f4b1c23 100644
--- a/lib/hash.h
+++ b/lib/hash.h
@@ -48,16 +48,16 @@
   unsigned int (*hash_key) (void *);
 
   /* Data compare function. */
-  int (*hash_cmp) (void *, void *);
+  int (*hash_cmp) (const void *, const void *);
 
   /* Backet alloc. */
   unsigned long count;
 };
 
 extern struct hash *hash_create (unsigned int (*) (void *), 
-                          int (*) (void *, void *));
+				 int (*) (const void *, const void *));
 extern struct hash *hash_create_size (unsigned int, unsigned int (*) (void *), 
-                                             int (*) (void *, void *));
+                                             int (*) (const void *, const void *));
 
 extern void *hash_get (struct hash *, void *, void * (*) (void *));
 extern void *hash_alloc_intern (void *);
diff --git a/lib/if_rmap.c b/lib/if_rmap.c
index e6f753c..ddc62fd 100644
--- a/lib/if_rmap.c
+++ b/lib/if_rmap.c
@@ -120,13 +120,12 @@
 }
 
 static int
-if_rmap_hash_cmp (void *arg1, void* arg2)
+if_rmap_hash_cmp (const void *arg1, const void* arg2)
 {
-  struct if_rmap *if_rmap1 = arg1;
-  struct if_rmap *if_rmap2 = arg2;
-  if (strcmp (if_rmap1->ifname, if_rmap2->ifname) == 0)
-    return 1;
-  return 0;
+  const struct if_rmap *if_rmap1 = arg1;
+  const struct if_rmap *if_rmap2 = arg2;
+
+  return strcmp (if_rmap1->ifname, if_rmap2->ifname) == 0;
 }
 
 static struct if_rmap *
diff --git a/lib/thread.c b/lib/thread.c
index 095dff4..260e8c8 100644
--- a/lib/thread.c
+++ b/lib/thread.c
@@ -223,8 +223,8 @@
 }
 
 static int 
-cpu_record_hash_cmp (struct cpu_thread_history *a,
-		     struct cpu_thread_history *b)
+cpu_record_hash_cmp (const struct cpu_thread_history *a,
+		     const struct cpu_thread_history *b)
 {
   return a->func == b->func;
 }
@@ -410,7 +410,7 @@
   if (cpu_record == NULL) 
     cpu_record 
       = hash_create_size (1011, (unsigned int (*) (void *))cpu_record_hash_key, 
-                          (int (*) (void *, void *))cpu_record_hash_cmp);
+                          (int (*) (const void *, const void *))cpu_record_hash_cmp);
     
   return (struct thread_master *) XCALLOC (MTYPE_THREAD_MASTER,
 					   sizeof (struct thread_master));