* 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

1 files changed, 3 insertions, 1 deletions

diff --git a/string.c b/string.c
index 189cc1b751..d72d0352c7 100644
--- a/string.c
+++ b/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);