From e5f30f83ce5f5a11c77990718b323f4718a3a03a Mon Sep 17 00:00:00 2001
From: Tomoyuki Sahara <tsahara@iij.ad.jp>
Date: Mon, 21 Apr 2014 10:01:49 +0900
Subject: IO#flush should raise an exception if it is closed.

---
 mrblib/io.rb | 1 +
 1 file changed, 1 insertion(+)

diff --git a/mrblib/io.rb b/mrblib/io.rb
index 249488ac4..cd8c801d2 100644
--- a/mrblib/io.rb
+++ b/mrblib/io.rb
@@ -91,6 +91,7 @@ class IO
 
   def flush
     # mruby-io always writes immediately (no output buffer).
+    raise IOError, "closed stream" if self.closed?
     self
   end
 
-- 
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