>From b7d414a376e85c55e0187abaa8d228c2c75e574f Mon Sep 17 00:00:00 2001
From: Peter Bex <address@hidden>
Date: Sun, 4 Mar 2012 18:32:08 +0100
Subject: [PATCH] Don't allow random numbers for hash tables to have all
 zeroes as lower bits; especially for small hashes this
 produces values that are more predictable than neccessary.
 Also hide hash-default-randomization in srfi-69

---
 eval.scm    |    4 +++-
 runtime.c   |    2 +-
 srfi-69.scm |    9 +++++----
 3 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/eval.scm b/eval.scm
index 779c230..e049895 100644
--- a/eval.scm
+++ b/eval.scm
@@ -45,6 +45,8 @@
 #ifndef C_BINARY_VERSION
 # define C_BINARY_VERSION      0
 #endif
+
+#define C_rnd_fix()		(C_fix(rand()))
 <#
 
 (include "common-declarations.scm")
@@ -111,7 +113,7 @@
   (let ([cache-s #f]
 	[cache-h #f]
         ;; NOTE: All low-level hash tables share the same randomization factor
-        [rand (##core#inline "C_random_fixnum" most-positive-fixnum)] )
+        [rand (##core#inline "C_rnd_fix")] )
     (lambda (s n)
       (if (eq? s cache-s)
 	  (##core#inline "C_fixnum_modulo" cache-h n)
diff --git a/runtime.c b/runtime.c
index 41a2f9d..5f10812 100644
--- a/runtime.c
+++ b/runtime.c
@@ -886,7 +886,7 @@ C_regparm C_SYMBOL_TABLE *C_new_symbol_table(char *name, unsigned int size)
   stp->name = name;
   stp->size = size;
   stp->next = symbol_table_list;
-  stp->rand = C_unfix(C_random_fixnum(C_fix(size)));
+  stp->rand = rand();
 
   if((stp->table = (C_word *)C_malloc(size * sizeof(C_word))) == NULL)
     return NULL;
diff --git a/srfi-69.scm b/srfi-69.scm
index 4b22a3c..2ea384f 100644
--- a/srfi-69.scm
+++ b/srfi-69.scm
@@ -30,11 +30,13 @@
   *eq?-hash *eqv?-hash *equal?-hash
   *make-hash-table
   *hash-table-copy *hash-table-merge! *hash-table-update!/default
-  *hash-table-for-each *hash-table-fold
+  *hash-table-for-each *hash-table-fold hash-default-randomization
   hash-table-canonical-length hash-table-rehash! hash-table-check-resize! ) )
 
 (include "common-declarations.scm")
 
+(foreign-declare "#define C_rnd_fix() (C_fix(rand()))")
+
 (register-feature! 'srfi-69)
 
 
@@ -105,8 +107,7 @@
 (define-constant unknown-immediate-hash-value 262)
 
 (define-constant hash-default-bound 536870912)
-(define hash-default-randomization
-  (##core#inline "C_random_fixnum" hash-default-bound))
+(define hash-default-randomization (##core#inline "C_rnd_fix"))
 
 ;; Force Hash to Bounded Fixnum:
 
@@ -414,7 +415,7 @@
 				string-hash string-hash-ci number-hash))
       ;; Don't add unneccessary bounds checks for procedures known to be
       ;; well-behaved (these are not user-*created* functions)
-      (let ((randomization (##core#inline "C_random_fixnum" most-positive-fixnum)))
+      (let ((randomization (##core#inline "C_rnd_fix")))
         (if (memq user-function (list string-hash string-hash-ci))
             ;; String functions have differing signatures; treat them specially
             (lambda (object bound)
-- 
1.7.9.1