2 files changed, 6 insertions, 0 deletions
diff --git a/ChangeLog b/ChangeLog
index 4917d54ffa..0d920986b7 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Thu Aug 16 20:40:50 2007  Yukihiro Matsumoto  <matz@ruby-lang.org>
+
+	* bignum.c (bigtrunc): RBIGNUM(x)->len may be zero.  out of bound
+	  access.  [ruby-dev:31404]
+
 Thu Aug 16 16:46:07 2007  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* configure.in (aix): enable shared by default.
diff --git a/bignum.c b/bignum.c
index e49a18b118..e6ecb3933b 100644
--- a/bignum.c
+++ b/bignum.c
@@ -104,6 +104,7 @@ bigtrunc(x)
     long len = RBIGNUM(x)->len;
     BDIGIT *ds = BDIGITS(x);
 
+    if (len == 0) return x;
     while (--len && !ds[len]);
     RBIGNUM(x)->len = ++len;
     return x;