string.c: fix capacity

* string.c (str_buf_cat): should round up the capacity by 4KiB,
  but not number of rooms.  [ruby-core:61886] [Bug #9709]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45534 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 1 insertions, 1 deletions

diff --git a/string.c b/string.c
index 511374c7b8..ccf265738e 100644
--- a/string.c
+++ b/string.c
@@ -2029,7 +2029,7 @@ str_buf_cat(VALUE str, const char *ptr, long len)
     if (capa <= total) {
 	while (total > capa) {
 	    if (capa + termlen >= LONG_MAX / 2) {
-		capa = (total + 4095) / 4096;
+		capa = (total + 4095) / 4096 * 4096;
 		break;
 	    }
 	    capa = (capa + termlen) * 2;