id,summary,reporter,owner,description,type,status,milestone,component,version,severity,resolution,keywords,cc
4170,Error using null_buffers in async_send_to in Windows,nythil@…,chris_kohlhoff,"While exploring the boost.asio library I came across a bug caused by a typo in one of the header files. When async_send_to is invoked on an UDP socket with null_buffers, the following sequence of calls takes place:
 1. {{{basic_datagram_socket->async_send_to(const ConstBufferSequence& buffers, const endpoint_type& destination, WriteHandler handler)}}}
 2. {{{datagram_socket_service->async_send_to(implementation_type& impl, const ConstBufferSequence& buffers, const endpoint_type& destination, socket_base::message_flags flags, WriteHandler handler)}}}
 3. {{{win_iocp_socket_service->async_send_to(implementation_type& impl, const ConstBufferSequence& buffers, const endpoint_type& destination, socket_base::message_flags flags, Handler handler)}}}

The problem is, the 3rd function is the generic version of async_send_to() which expects a valid buffer. Passing null_buffers causes an error. 

There is also a specialization of async_send_to() for the null_buffers case. Unfortunately, it's never called, because in the declaration some arguments are out of place. The declaration is: {{{async_send_to(implementation_type& impl, const null_buffers&, socket_base::message_flags, const endpoint_type&, Handler handler)}}}. Compared to the generic version, the {{{flags}}} and {{{destination}}} arguments are swapped. After correcting the order of these two arguments, async_send_to() works as expected.",Bugs,closed,Boost 1.44.0,asio,Boost Development Trunk,Problem,fixed,,