* string.c (str_gsub): avoid appending empty pre-match substr.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@14944 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,7 @@
+Tue Jan  8 15:03:10 2008  Tanaka Akira  <akr@fsij.org>
+
+	* string.c (str_gsub): avoid appending empty pre-match substr.
+
 Tue Jan  8 13:05:57 2008  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* compile.c (iseq_build_from_ary), iseq.c (iseq_load): fix for format change.

string.c

@@ -2720,7 +2720,9 @@ str_gsub(int argc, VALUE *argv, VALUE str, int bang)
 	if (OBJ_TAINTED(val)) tainted = 1;
 
 	len = beg - offset;	/* copy pre-match substr */
-        rb_enc_str_buf_cat(dest, cp, len, str_enc);
+        if (len) {
+            rb_enc_str_buf_cat(dest, cp, len, str_enc);
+        }
 
         rb_str_buf_append(dest, val);