From 9865ee2c46b7cc9244c3d78b786ee14a7a302e53 Mon Sep 17 00:00:00 2001
From: tarui <tarui@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>
Date: Tue, 7 Dec 2010 13:38:36 +0000
Subject: [PATCH] 	* io.c (io_read): duplicate string if shared.
 [ruby-dev:42719]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@30122 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
---
 ChangeLog | 4 ++++
 io.c      | 5 ++++-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/ChangeLog b/ChangeLog
index dc7718fe3a..89962d2dea 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Tue Dec  7 22:37:15 2010  Masaya Tarui  <tarui@ruby-lnag.org>
+
+	* io.c (io_read): duplicate string if shared. [ruby-dev:42719]
+
 Tue Dec  7 22:31:08 2010  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* lib/optparse.rb (OptionParser::Officious): separate completion
diff --git a/io.c b/io.c
index 26af3ce6ef..d5d1220294 100644
--- a/io.c
+++ b/io.c
@@ -2212,7 +2212,10 @@ io_read(int argc, VALUE *argv, VALUE io)
     rb_scan_args(argc, argv, "02", &length, &str);
 
     if (NIL_P(length)) {
-	if (!NIL_P(str)) StringValue(str);
+	if (!NIL_P(str)){
+	    StringValue(str);
+	    rb_str_modify(str);
+	}
 	GetOpenFile(io, fptr);
 	rb_io_check_char_readable(fptr);
 	return read_all(fptr, remain_size(fptr), str);