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diff --git a/boost/asio/detail/gcc_sync_fenced_block.hpp b/boost/asio/detail/gcc_sync_fenced_block.hpp
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+++ b/boost/asio/detail/gcc_sync_fenced_block.hpp
@@ -0,0 +1,65 @@
+//
+// detail/gcc_sync_fenced_block.hpp
+// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+//
+// Copyright (c) 2003-2012 Christopher M. Kohlhoff (chris at kohlhoff dot com)
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+//
+
+#ifndef BOOST_ASIO_DETAIL_GCC_SYNC_FENCED_BLOCK_HPP
+#define BOOST_ASIO_DETAIL_GCC_SYNC_FENCED_BLOCK_HPP
+
+#if defined(_MSC_VER) && (_MSC_VER >= 1200)
+# pragma once
+#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
+
+#include <boost/asio/detail/config.hpp>
+
+#if defined(__GNUC__) \
+  && ((__GNUC__ == 4 && __GNUC_MINOR__ >= 1) || (__GNUC__ > 4)) \
+  && !defined(__INTEL_COMPILER) && !defined(__ICL) \
+  && !defined(__ICC) && !defined(__ECC) && !defined(__PATHSCALE__)
+
+#include <boost/asio/detail/push_options.hpp>
+
+namespace boost {
+namespace asio {
+namespace detail {
+
+class gcc_sync_fenced_block
+  : private noncopyable
+{
+public:
+  enum half_or_full_t { half, full };
+
+  // Constructor.
+  explicit gcc_sync_fenced_block(half_or_full_t)
+    : value_(0)
+  {
+    __sync_lock_test_and_set(&value_, 1);
+  }
+
+  // Destructor.
+  ~gcc_sync_fenced_block()
+  {
+    __sync_lock_release(&value_);
+  }
+
+private:
+  int value_;
+};
+
+} // namespace detail
+} // namespace asio
+} // namespace boost
+
+#include <boost/asio/detail/pop_options.hpp>
+
+#endif // defined(__GNUC__)
+       // && ((__GNUC__ == 4 && __GNUC_MINOR__ >= 1) || (__GNUC__ > 4))
+       // && !defined(__INTEL_COMPILER) && !defined(__ICL)
+       // && !defined(__ICC) && !defined(__ECC) && !defined(__PATHSCALE__)
+
+#endif // BOOST_ASIO_DETAIL_GCC_SYNC_FENCED_BLOCK_HPP