[core] splaytree: use all 32-bits of hash value

src/algo_splaytree.c

@@ -52,9 +52,10 @@
 #include <stdlib.h>
 #include <assert.h>
 
-#define compare(i,j) ((i)-(j))
+#define compare(i,j) ((int)(((unsigned int)i)-((unsigned int)j)))
 /* This is the comparison.                                       */
 /* Returns <0 if i<j, =0 if i=j, and >0 if i>j                   */
+/* (cast to unsigned int for underflow/overflow defined behavior)*/
 
 /* Splay using the key i (which may or may not be in the tree.)
  * The starting root is t, and the tree used is defined by rat

src/algo_splaytree.h

@@ -20,8 +20,7 @@ __attribute_pure__
 static inline int32_t splaytree_djbhash(const char *str, const uint32_t len);
 static inline int32_t splaytree_djbhash(const char *str, const uint32_t len)
 {
-    /* strip highest bit of hash value for splaytree */
-    return (int32_t)(djbhash(str,len,DJBHASH_INIT) & ~(((uint32_t)1) << 31));
+    return (int32_t)djbhash(str, len, DJBHASH_INIT);
 }
 
 

src/mod_auth.c

@@ -117,14 +117,15 @@ http_auth_cache_init (const array *opts)
     return ac;
 }
 
+__attribute_pure__
 static int
 http_auth_cache_hash (const struct http_auth_require_t * const require, const char *username, const uint32_t ulen)
 {
+    /* (similar to splaytree_djbhash(), but with two strings hashed) */
     uint32_t h = /*(hash pointer value, which includes realm and permissions)*/
       djbhash((char *)(intptr_t)require, sizeof(intptr_t), DJBHASH_INIT);
     h = djbhash(username, ulen, h);
-    /* strip highest bit of hash value for splaytree (see splaytree_djbhash())*/
-    return (int32_t)(h & ~(((uint32_t)1) << 31));
+    return (int32_t)h;
 }
 
 static http_auth_cache_entry *