boost exception

[SVN r43485]

example/cloning_1.cpp

@@ -0,0 +1,22 @@
+//Copyright (c) 2006-2008 Emil Dotchevski and Reverge Studios, Inc.
+
+//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)
+
+//This example shows how to enable cloning when throwing a boost::exception.
+
+#include <boost/exception/enable_exception_cloning.hpp>
+#include <boost/exception/info.hpp>
+#include <stdio.h>
+#include <errno.h>
+
+typedef boost::error_info<struct tag_errno,int> errno_info;
+
+class file_read_error: public boost::exception { };
+
+void
+file_read( FILE * f, void * buffer, size_t size )
+	{
+    if( size!=fread(buffer,1,size,f) )
+        throw boost::enable_exception_cloning(file_read_error()) << errno_info(errno);
+	}