boost exception

[SVN r43485]

example/error_info_1.cpp

@@ -0,0 +1,36 @@
+//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 add data to boost::exception objects at the
+//point of the throw, and how to retrieve that data at the point of the catch.
+
+#include <boost/exception.hpp>
+#include <errno.h>
+#include <iostream>
+
+typedef boost::error_info<struct tag_errno,int> errno_info; //(1)
+
+class my_error: public boost::exception, public std::exception { }; //(2)
+
+void
+f()
+	{
+    throw my_error() << errno_info(errno); //(3)
+	}
+				 
+void
+g()
+	{
+    try
+		{
+        f();
+	    }
+    catch(
+	my_error & x )
+		{
+		if( boost::shared_ptr<int const> err=boost::get_error_info<errno_info>(x) )
+            std::cerr << "Error code: " << *err;
+		}
+	}