Fix for issue cpp-netlib#419

Author: Jussi Lyytinen

boost/network/protocol/http/algorithms/linearize.hpp

@@ -2,6 +2,7 @@
 #define BOOST_NETWORK_PROTOCOL_HTTP_ALGORITHMS_LINEARIZE_HPP_20101028
 
 // Copyright 2010 Dean Michael Berris.
+// Copyright 2014 Jussi Lyytinen
 // 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)
@@ -137,7 +138,7 @@ BOOST_CONCEPT_REQUIRES(((ClientRequest<Request>)), (OutputIterator))
     *oi = consts::colon_char();
     *oi = consts::space_char();
     boost::copy(request.host(), oi);
-    boost::optional<boost::uint16_t> port_ = port(request);
+    boost::optional<boost::uint16_t> port_ = port(request).as_optional();
     if (port_) {
       string_type port_str = boost::lexical_cast<string_type>(*port_);
       *oi = consts::colon_char();

boost/network/protocol/http/message/wrappers/port.hpp

@@ -4,6 +4,7 @@
 // Copyright 2010, 2014 Dean Michael Berris <[email protected]>
 // Copyright 2010 (c) Sinefunc, Inc.
 // Copyright 2014 Google, Inc.
+// Copyright 2014 Jussi Lyytinen
 // 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)
@@ -31,23 +32,20 @@ struct port_wrapper {
 
   operator port_type() const { return message_.port(); }
 
-#if (_MSC_VER >= 1600)
-  // We hack this so that we don't run into the issue of MSVC 2010 not doing the
-  // right thing when converting/copying Boost.Optional objects.
-  struct optional_wrapper {
-    boost::optional<boost::uint16_t> o_;
-    explicit optional_wrapper(boost::optional<boost::uint16_t> o) : o_(o) {}
-    operator boost::optional<boost::uint16_t>() const { return o_; }
-  };
-
-  operator optional_wrapper() const {
-    return optional_wrapper(uri::port_us(message_.uri()));
-  }
-#else
+#if !defined(_MSC_VER)
+  // Because of a breaking change in Boost 1.56 to boost::optional, implicit
+  // conversions no longer work correctly with MSVC. The conversion therefore
+  // has to be done explicitly with as_optional(). This method is here just
+  // to maintain backwards compatibility with compilers not affected by the
+  // change.
   operator boost::optional<boost::uint16_t>() const {
     return uri::port_us(message_.uri());
   }
 #endif
+  
+  boost::optional<boost::uint16_t> as_optional() const {
+    return uri::port_us(message_.uri());
+  }
 
 };