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<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="asio.history"></a><a class="link" href="history.html" title="Revision History">Revision History</a>
</h2></div></div></div>
<h4>
<a name="asio.history.h0"></a>
      <span><a name="asio.history.asio_1_10_2"></a></span><a class="link" href="history.html#asio.history.asio_1_10_2">Asio
      1.10.2</a>
    </h4>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
          Fixed <code class="computeroutput"><span class="identifier">asio</span><span class="special">::</span><span class="identifier">spawn</span><span class="special">()</span></code>
          to work correctly with new Boost.Coroutine interface.
        </li>
<li class="listitem">
          Ensured that incomplete <code class="computeroutput"><span class="identifier">asio</span><span class="special">::</span><span class="identifier">spawn</span><span class="special">()</span></code> coroutines are correctly unwound when
          cleaned up by the <code class="computeroutput"><span class="identifier">io_service</span></code>
          destructor.
        </li>
<li class="listitem">
          Fixed delegation of continuation hook for handlers produced by <code class="computeroutput"><span class="identifier">io_service</span><span class="special">::</span><span class="identifier">wrap</span><span class="special">()</span></code>
          and <code class="computeroutput"><span class="identifier">strand</span><span class="special">::</span><span class="identifier">wrap</span><span class="special">()</span></code>.
        </li>
<li class="listitem">
          Changed the Windows I/O completion port backend to use <code class="computeroutput"><span class="identifier">ConnectEx</span></code>,
          if available, for connection-oriented IP sockets.
        </li>
<li class="listitem">
          Changed the <code class="computeroutput"><span class="identifier">io_service</span></code>
          backend for non-Windows (and non-IOCP Windows) platforms to use a single
          condition variable per <code class="computeroutput"><span class="identifier">io_service</span></code>
          instance. This addresses a potential race condition when <code class="computeroutput"><span class="identifier">run_one</span><span class="special">()</span></code>
          is used from multiple threads.
        </li>
<li class="listitem">
          Prevented integer overflow when computing timeouts based on some <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span></code> and <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">chrono</span></code>
          clocks.
        </li>
<li class="listitem">
          Made further changes to <code class="computeroutput"><span class="identifier">EV_CLEAR</span></code>
          handling in the kqueue backend, to address other cases where the <code class="computeroutput"><span class="identifier">close</span><span class="special">()</span></code>
          system call may hang on Mac OS X.
        </li>
<li class="listitem">
          Fixed infinite recursion in implementation of <code class="computeroutput"><span class="identifier">resolver_query_base</span><span class="special">::</span><span class="identifier">flags</span><span class="special">::</span><span class="keyword">operator</span><span class="special">~</span></code>.
        </li>
<li class="listitem">
          Made the <code class="computeroutput"><span class="identifier">select</span></code> reactor
          more efficient on Windows for large numbers of sockets.
        </li>
<li class="listitem">
          Fixed a Windows-specific type-aliasing issue reported by <code class="literal">gcc</code>.
        </li>
<li class="listitem">
          Prevented execution of compile-time-only buffer test to avoid triggering
          an address sanitiser warning.
        </li>
<li class="listitem">
          Disabled the <code class="computeroutput"><span class="identifier">GetQueuedCompletionStatus</span></code>
          timeout workaround on recent versions of Windows.
        </li>
<li class="listitem">
          Changed implementation for Windows Runtime to use <code class="computeroutput"><span class="identifier">FormatMessageW</span></code>
          rather than <code class="computeroutput"><span class="identifier">FormatMessageA</span></code>,
          as the Windows store does not permit the latter.
        </li>
<li class="listitem">
          Added support for string-based scope IDs when using link-local multicast
          addresses.
        </li>
<li class="listitem">
          Changed IPv6 multicast group join to use the address's scope ID as the
          interface, if an interface is not explicitly specified.
        </li>
<li class="listitem">
          Fixed multicast test failure on Mac OS X and the BSDs by using a link-local
          multicast address.
        </li>
<li class="listitem">
          Various minor documentation improvements.
        </li>
</ul></div>
<h4>
<a name="asio.history.h1"></a>
      <span><a name="asio.history.asio_1_10_1"></a></span><a class="link" href="history.html#asio.history.asio_1_10_1">Asio
      1.10.1</a>
    </h4>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
          Implemented a limited port to Windows Runtime. This support requires that
          the language extensions be enabled. Due to the restricted facilities exposed
          by the Windows Runtime API, the port also comes with the following caveats:
          <div class="itemizedlist"><ul class="itemizedlist" type="circle">
<li class="listitem">
                The core facilities such as the <code class="computeroutput"><span class="identifier">io_service</span></code>,
                <code class="computeroutput"><span class="identifier">strand</span></code>, buffers,
                composed operations, timers, etc., should all work as normal.
              </li>
<li class="listitem">
                For sockets, only client-side TCP is supported.
              </li>
<li class="listitem">
                Explicit binding of a client-side TCP socket is not supported.
              </li>
<li class="listitem">
                The <code class="computeroutput"><span class="identifier">cancel</span><span class="special">()</span></code>
                function is not supported for sockets. Asynchronous operations may
                only be cancelled by closing the socket.
              </li>
<li class="listitem">
                Operations that use <code class="computeroutput"><span class="identifier">null_buffers</span></code>
                are not supported.
              </li>
<li class="listitem">
                Only <code class="computeroutput"><span class="identifier">tcp</span><span class="special">::</span><span class="identifier">no_delay</span></code> and <code class="computeroutput"><span class="identifier">socket_base</span><span class="special">::</span><span class="identifier">keep_alive</span></code>
                options are supported.
              </li>
<li class="listitem">
                Resolvers do not support service names, only numbers. I.e. you must
                use "80" rather than "http".
              </li>
<li class="listitem">
                Most resolver query flags have no effect.
              </li>
</ul></div>
        </li>
<li class="listitem">
          Extended the ability to use Asio without Boost to include Microsoft Visual
          Studio 2012. When using a C++11 compiler, most of Asio may now be used
          without a dependency on Boost header files or libraries. To use Asio in
          this way, define <code class="computeroutput"><span class="identifier">ASIO_STANDALONE</span></code>
          on your compiler command line or as part of the project options. This standalone
          configuration has been tested for the following platforms and compilers:
          <div class="itemizedlist"><ul class="itemizedlist" type="circle">
<li class="listitem">
                Microsoft Visual Studio 2012
              </li>
<li class="listitem">
                Linux with g++ 4.7 or 4.8 (requires <code class="literal">-std=c++11</code>)
              </li>
<li class="listitem">
                Mac OS X with clang++ / Xcode 4.6 (requires <code class="literal">-std=c++11 -stdlib=libc++</code>)
              </li>
</ul></div>
        </li>
<li class="listitem">
          Fixed a regression (introduced in 1.10.0) where, on some platforms, errors
          from <code class="computeroutput"><span class="identifier">async_connect</span></code> were
          not correctly propagated through to the completion handler.
        </li>
<li class="listitem">
          Fixed a Windows-specific regression (introduced in 1.10.0) that occurs
          when multiple threads are running an <code class="computeroutput"><span class="identifier">io_service</span></code>.
          When the bug occurs, the result of an asynchronous operation (error and
          bytes tranferred) is incorrectly discarded and zero values used instead.
          For TCP sockets this results in spurious end-of-file notifications.
        </li>
<li class="listitem">
          Fixed a bug in handler tracking, where it was not correctly printing out
          some handler IDs.
        </li>
<li class="listitem">
          Fixed the comparison used to test for successful synchronous accept operations
          so that it works correctly with unsigned socket descriptors.
        </li>
<li class="listitem">
          Ensured the signal number is correctly passed to the completion handler
          when starting an <code class="computeroutput"><span class="identifier">async_wait</span></code>
          on a signal that is already raised.
        </li>
<li class="listitem">
          Suppressed a g++ 4.8+ warning about unused typedefs.
        </li>
<li class="listitem">
          Enabled the move optimisation for handlers that use the default invocation
          hook.
        </li>
<li class="listitem">
          Clarified that programs must not issue overlapping <code class="computeroutput"><span class="identifier">async_write_at</span></code>
          operations.
        </li>
<li class="listitem">
          Changed the Windows <code class="computeroutput"><span class="identifier">HANDLE</span></code>
          backend to treat <code class="computeroutput"><span class="identifier">ERROR_MORE_DATA</span></code>
          as a non-fatal error when returned by <code class="computeroutput"><span class="identifier">GetOverlappedResult</span></code>
          for a synchronous read.
        </li>
<li class="listitem">
          Visual C++ language extensions use <code class="computeroutput"><span class="identifier">generic</span></code>
          as a keyword. Added a workaround that renames the namespace to <code class="computeroutput"><span class="identifier">cpp_generic</span></code> when those language extensions
          are in effect.
        </li>
<li class="listitem">
          Fixed some asynchronous operations that missed out on getting <code class="computeroutput"><span class="identifier">async_result</span></code> support in 1.10.0. In particular,
          the buffered stream templates have been updated so that they adhere to
          current handler patterns.
        </li>
<li class="listitem">
          Enabled move support for Microsoft Visual Studio 2012.
        </li>
<li class="listitem">
          Added <code class="computeroutput"><span class="identifier">use_future</span></code> support
          for Microsoft Visual Studio 2012.
        </li>
<li class="listitem">
          Removed a use of <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">min</span></code> in the Windows IOCP backend to avoid
          a dependency on the <code class="computeroutput"><span class="special">&lt;</span><span class="identifier">algorithm</span><span class="special">&gt;</span></code> header.
        </li>
<li class="listitem">
          Eliminated some unnecessary handler copies.
        </li>
<li class="listitem">
          Fixed support for older versions of OpenSSL that do not provide the <code class="computeroutput"><span class="identifier">SSL_CTX_clear_options</span></code> function.
        </li>
<li class="listitem">
          Fixed various minor and cosmetic issues in code and documentation.
        </li>
</ul></div>
<h4>
<a name="asio.history.h2"></a>
      <span><a name="asio.history.asio_1_10_0"></a></span><a class="link" href="history.html#asio.history.asio_1_10_0">Asio
      1.10.0</a>
    </h4>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
          Added new traits classes, <code class="computeroutput"><span class="identifier">handler_type</span></code>
          and <code class="computeroutput"><span class="identifier">async_result</span></code>, that
          allow the customisation of the return type of an initiating function.
        </li>
<li class="listitem">
          Added the <code class="computeroutput"><span class="identifier">asio</span><span class="special">::</span><span class="identifier">spawn</span><span class="special">()</span></code>
          function, a high-level wrapper for running stackful coroutines, based on
          the Boost.Coroutine library. The <code class="computeroutput"><span class="identifier">spawn</span><span class="special">()</span></code> function enables programs to implement
          asynchronous logic in a synchronous manner. For example: <code class="computeroutput"><span class="identifier">size_t</span> <span class="identifier">n</span>
          <span class="special">=</span> <span class="identifier">my_socket</span><span class="special">.</span><span class="identifier">async_read_some</span><span class="special">(</span><span class="identifier">my_buffer</span><span class="special">,</span> <span class="identifier">yield</span><span class="special">);</span></code>. For further information, see <a class="link" href="overview/core/spawn.html" title="Stackful Coroutines">Stackful
          Coroutines</a>.
        </li>
<li class="listitem">
          Added the <code class="computeroutput"><span class="identifier">asio</span><span class="special">::</span><span class="identifier">use_future</span></code> special value, which provides
          first-class support for returning a C++11 <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">future</span></code>
          from an asynchronous operation's initiating function. For example: <code class="computeroutput"><span class="identifier">future</span><span class="special">&lt;</span><span class="identifier">size_t</span><span class="special">&gt;</span>
          <span class="special">=</span> <span class="identifier">my_socket</span><span class="special">.</span><span class="identifier">async_read_some</span><span class="special">(</span><span class="identifier">my_buffer</span><span class="special">,</span> <span class="identifier">asio</span><span class="special">::</span><span class="identifier">use_future</span><span class="special">);</span></code>. For further information, see <a class="link" href="overview/cpp2011/futures.html" title="Futures">C++
          2011 Support - Futures</a>.
        </li>
<li class="listitem">
          Promoted the stackless coroutine class and macros to be part of Asio's
          documented interface, rather than part of the HTTP server 4 example. For
          further information, see <a class="link" href="overview/core/coroutine.html" title="Stackless Coroutines">Stackless
          Coroutines</a>.
        </li>
<li class="listitem">
          Added a new handler hook called <code class="computeroutput"><span class="identifier">asio_handler_is_continuation</span></code>.
          Asynchronous operations may represent a continuation of the asynchronous
          control flow associated with the current executing handler. The <code class="computeroutput"><span class="identifier">asio_handler_is_continuation</span></code> hook can
          be customised to return <code class="computeroutput"><span class="keyword">true</span></code>
          if this is the case, and Asio's implementation can use this knowledge to
          optimise scheduling of the new handler. To cover common cases, Asio customises
          the hook for strands, <code class="computeroutput"><span class="identifier">spawn</span><span class="special">()</span></code> and composed asynchronous operations.
        </li>
<li class="listitem">
          Added four new generic protocol classes, <code class="computeroutput"><span class="identifier">generic</span><span class="special">::</span><span class="identifier">datagram_protocol</span></code>,
          <code class="computeroutput"><span class="identifier">generic</span><span class="special">::</span><span class="identifier">raw_protocol</span></code>, <code class="computeroutput"><span class="identifier">generic</span><span class="special">::</span><span class="identifier">seq_packet_protocol</span></code>
          and <code class="computeroutput"><span class="identifier">generic</span><span class="special">::</span><span class="identifier">stream_protocol</span></code>, which implement the
          <code class="computeroutput"><span class="identifier">Protocol</span></code> type requirements,
          but allow the user to specify the address family (e.g. <code class="computeroutput"><span class="identifier">AF_INET</span></code>)
          and protocol type (e.g. <code class="computeroutput"><span class="identifier">IPPROTO_TCP</span></code>)
          at runtime. For further information, see <a class="link" href="overview/networking/other_protocols.html" title="Support for Other Protocols">Support
          for Other Protocols</a>.
        </li>
<li class="listitem">
          Added C++11 move constructors that allow the conversion of a socket (or
          acceptor) into a more generic type. For example, an <code class="computeroutput"><span class="identifier">ip</span><span class="special">::</span><span class="identifier">tcp</span><span class="special">::</span><span class="identifier">socket</span></code>
          can be converted into a <code class="computeroutput"><span class="identifier">generic</span><span class="special">::</span><span class="identifier">stream_protocol</span><span class="special">::</span><span class="identifier">socket</span></code>
          via move construction. For further information, see <a class="link" href="overview/networking/other_protocols.html" title="Support for Other Protocols">Support
          for Other Protocols</a>.
        </li>
<li class="listitem">
          Extended the <code class="computeroutput"><span class="identifier">basic_socket_acceptor</span><span class="special">&lt;&gt;</span></code>'s <code class="computeroutput"><span class="identifier">accept</span><span class="special">()</span></code> and <code class="computeroutput"><span class="identifier">async_accept</span><span class="special">()</span></code> functions to allow a new connection to
          be accepted directly into a socket of a more generic type. For example,
          an <code class="computeroutput"><span class="identifier">ip</span><span class="special">::</span><span class="identifier">tcp</span><span class="special">::</span><span class="identifier">acceptor</span></code> can be used to accept into a
          <code class="computeroutput"><span class="identifier">generic</span><span class="special">::</span><span class="identifier">stream_protocol</span><span class="special">::</span><span class="identifier">socket</span></code> object. For further information,
          see <a class="link" href="overview/networking/other_protocols.html" title="Support for Other Protocols">Support for
          Other Protocols</a>.
        </li>
<li class="listitem">
          Moved existing examples into a C++03-specific directory, and added a new
          directory for C++11-specific examples. A limited subset of the C++03 examples
          have been converted to their C++11 equivalents.
        </li>
<li class="listitem">
          Add the ability to use Asio without Boost, for a limited set of platforms.
          When using a C++11 compiler, most of Asio may now be used without a dependency
          on Boost header files or libraries. To use Asio in this way, define <code class="computeroutput"><span class="identifier">ASIO_STANDALONE</span></code> on your compiler command
          line or as part of the project options. This standalone configuration has
          currently been tested for the following platforms and compilers:
          <div class="itemizedlist"><ul class="itemizedlist" type="circle">
<li class="listitem">
                Linux with g++ 4.7 (requires <code class="literal">-std=c++11</code>)
              </li>
<li class="listitem">
                Mac OS X with clang++ / Xcode 4.6 (requires <code class="literal">-std=c++11 -stdlib=libc++</code>)
              </li>
</ul></div>
        </li>
<li class="listitem">
          Various SSL enhancements. Thanks go to Nick Jones, on whose work these
          changes are based.
          <div class="itemizedlist"><ul class="itemizedlist" type="circle">
<li class="listitem">
                Added support for SSL handshakes with re-use of data already read
                from the wire. New overloads of the <code class="computeroutput"><span class="identifier">ssl</span><span class="special">::</span><span class="identifier">stream</span><span class="special">&lt;&gt;</span></code> class's <code class="computeroutput"><span class="identifier">handshake</span><span class="special">()</span></code> and <code class="computeroutput"><span class="identifier">async_handshake</span><span class="special">()</span></code> functions have been added. These
                accept a <code class="computeroutput"><span class="identifier">ConstBufferSequence</span></code>
                to be used as initial input to the ssl engine for the handshake procedure.
              </li>
<li class="listitem">
                Added support for creation of TLSv1.1 and TLSv1.2 <code class="computeroutput"><span class="identifier">ssl</span><span class="special">::</span><span class="identifier">context</span></code>
                objects.
              </li>
<li class="listitem">
                Added a <code class="computeroutput"><span class="identifier">set_verify_depth</span><span class="special">()</span></code> function to the <code class="computeroutput"><span class="identifier">ssl</span><span class="special">::</span><span class="identifier">context</span></code>
                and <code class="computeroutput"><span class="identifier">ssl</span><span class="special">::</span><span class="identifier">stream</span><span class="special">&lt;&gt;</span></code>
                classes.
              </li>
<li class="listitem">
                Added the ability to load SSL certificate and key data from memory
                buffers. New functions, <code class="computeroutput"><span class="identifier">add_certificate_authority</span><span class="special">()</span></code>, <code class="computeroutput"><span class="identifier">use_certificate</span><span class="special">()</span></code>, <code class="computeroutput"><span class="identifier">use_certificate_chain</span><span class="special">()</span></code>, <code class="computeroutput"><span class="identifier">use_private_key</span><span class="special">()</span></code>, <code class="computeroutput"><span class="identifier">use_rsa_private_key</span><span class="special">()</span></code> and <code class="computeroutput"><span class="identifier">use_tmp_dh</span><span class="special">()</span></code>, have been added to the <code class="computeroutput"><span class="identifier">ssl</span><span class="special">::</span><span class="identifier">context</span></code> class.
              </li>
<li class="listitem">
                Changed <code class="computeroutput"><span class="identifier">ssl</span><span class="special">::</span><span class="identifier">context</span></code> to automatically disable
                SSL compression by default. To enable, use the new <code class="computeroutput"><span class="identifier">ssl</span><span class="special">::</span><span class="identifier">context</span><span class="special">::</span><span class="identifier">clear_options</span><span class="special">()</span></code>
                function, as in <code class="computeroutput"><span class="identifier">my_context</span><span class="special">.</span><span class="identifier">clear_options</span><span class="special">(</span><span class="identifier">ssl</span><span class="special">::</span><span class="identifier">context</span><span class="special">::</span><span class="identifier">no_compression</span><span class="special">)</span></code>.
              </li>
</ul></div>
        </li>
<li class="listitem">
          Fixed a potential deadlock in <code class="computeroutput"><span class="identifier">signal_set</span></code>
          implementation.
        </li>
<li class="listitem">
          Fixed an error in acceptor example in documentation.
        </li>
<li class="listitem">
          Fixed copy-paste errors in waitable timer documentation.
        </li>
<li class="listitem">
          Added assertions to satisfy some code analysis tools.
        </li>
<li class="listitem">
          Fixed a malformed <code class="computeroutput"><span class="preprocessor">#warning</span></code>
          directive.
        </li>
<li class="listitem">
          Fixed a potential data race in the Linux <code class="computeroutput"><span class="identifier">epoll</span></code>
          implementation.
        </li>
<li class="listitem">
          Fixed a Windows-specific bug, where certain operations might generate an
          <code class="computeroutput"><span class="identifier">error_code</span></code> with an invalid
          (i.e. <code class="computeroutput"><span class="identifier">NULL</span></code>) <code class="computeroutput"><span class="identifier">error_category</span></code>.
        </li>
<li class="listitem">
          Fixed <code class="computeroutput"><span class="identifier">basic_waitable_timer</span></code>'s
          underlying implementation so that it can handle any <code class="computeroutput"><span class="identifier">time_point</span></code>
          value without overflowing the intermediate duration objects.
        </li>
<li class="listitem">
          Fixed a problem with lost thread wakeups that can occur when making concurrent
          calls to <code class="computeroutput"><span class="identifier">run</span><span class="special">()</span></code>
          and <code class="computeroutput"><span class="identifier">poll</span><span class="special">()</span></code>
          on the same <code class="computeroutput"><span class="identifier">io_service</span></code>
          object.
        </li>
<li class="listitem">
          Fixed implementation of asynchronous connect operation so that it can cope
          with spurious readiness notifications from the reactor.
        </li>
<li class="listitem">
          Fixed a memory leak in the <code class="computeroutput"><span class="identifier">ssl</span><span class="special">::</span><span class="identifier">rfc2818_verification</span></code>
          class.
        </li>
<li class="listitem">
          Added a mechanism for disabling automatic Winsock initialisation. See the
          header file <code class="literal">asio/detail/winsock_init.hpp</code> for details.
        </li>
</ul></div>
<h4>
<a name="asio.history.h3"></a>
      <span><a name="asio.history.asio_1_8_3"></a></span><a class="link" href="history.html#asio.history.asio_1_8_3">Asio
      1.8.3</a>
    </h4>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
          Fixed some 64-to-32-bit conversion warnings.
        </li>
<li class="listitem">
          Fixed various small errors in documentation and comments.
        </li>
<li class="listitem">
          Fixed an error in the example embedded in <code class="computeroutput"><span class="identifier">basic_socket</span><span class="special">::</span><span class="identifier">get_option</span></code>'s
          documentation.
        </li>
<li class="listitem">
          Changed to use <code class="computeroutput"><span class="keyword">long</span></code> rather
          than <code class="computeroutput"><span class="keyword">int</span></code> for SSL_CTX options,
          to match OpenSSL.
        </li>
<li class="listitem">
          Changed to use <code class="computeroutput"><span class="identifier">_snwprintf</span></code>
          to address a compile error due to the changed <code class="computeroutput"><span class="identifier">swprintf</span></code>
          signature in recent versions of MinGW.
        </li>
<li class="listitem">
          Fixed a deadlock that can occur on Windows when shutting down a pool of
          <code class="computeroutput"><span class="identifier">io_service</span></code> threads due
          to running out of work.
        </li>
<li class="listitem">
          Changed UNIX domain socket example to treat errors from <code class="computeroutput"><span class="identifier">accept</span></code>
          as non-fatal.
        </li>
<li class="listitem">
          Added a small block recycling optimisation to improve default memory allocation
          behaviour.
        </li>
</ul></div>
<h4>
<a name="asio.history.h4"></a>
      <span><a name="asio.history.asio_1_8_2"></a></span><a class="link" href="history.html#asio.history.asio_1_8_2">Asio
      1.8.2</a>
    </h4>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
          Fixed an incompatibility between <code class="computeroutput"><span class="identifier">ip</span><span class="special">::</span><span class="identifier">tcp</span><span class="special">::</span><span class="identifier">iostream</span></code>
          and C++11.
        </li>
<li class="listitem">
          Decorated GCC attribute names with underscores to prevent interaction with
          user-defined macros.
        </li>
<li class="listitem">
          Added missing <code class="computeroutput"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">cctype</span><span class="special">&gt;</span></code>, needed for some versions of MinGW.
        </li>
<li class="listitem">
          Changed to use <code class="literal">gcc</code>'s atomic builtins on ARM CPUs, when
          available.
        </li>
<li class="listitem">
          Changed strand destruction to be a no-op, to allow strand objects to be
          destroyed after their associated <code class="computeroutput"><span class="identifier">io_service</span></code>
          has been destroyed.
        </li>
<li class="listitem">
          Added support for some newer versions of glibc which provide the <code class="computeroutput"><span class="identifier">epoll_create1</span><span class="special">()</span></code>
          function but always fail with ENOSYS.
        </li>
<li class="listitem">
          Changed the SSL implementation to throw an exception if SSL engine initialisation
          fails.
        </li>
<li class="listitem">
          Fixed another regression in <code class="computeroutput"><span class="identifier">buffered_write_stream</span></code>.
        </li>
<li class="listitem">
          Implemented various minor performance improvements, primarily targeted
          at Linux x86 and x86-64 platforms.
        </li>
</ul></div>
<h4>
<a name="asio.history.h5"></a>
      <span><a name="asio.history.asio_1_8_1"></a></span><a class="link" href="history.html#asio.history.asio_1_8_1">Asio
      1.8.1</a>
    </h4>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
          Changed the <code class="computeroutput"><span class="identifier">epoll_reactor</span></code>
          backend to do lazy registration for <code class="computeroutput"><span class="identifier">EPOLLOUT</span></code>
          events.
        </li>
<li class="listitem">
          Fixed the <code class="computeroutput"><span class="identifier">epoll_reactor</span></code>
          handling of out-of-band data, which was broken by an incomplete fix in
          the last release.
        </li>
<li class="listitem">
          Changed Asio's SSL wrapper to respect OpenSSL's <code class="computeroutput"><span class="identifier">OPENSSL_NO_ENGINE</span></code>
          feature test <code class="computeroutput"><span class="preprocessor">#define</span></code>.
        </li>
<li class="listitem">
          Fixed <code class="computeroutput"><span class="identifier">windows</span><span class="special">::</span><span class="identifier">object_handle</span></code> so that it works with Windows
          compilers that support C++11 move semantics (such as <code class="literal">g++</code>).
        </li>
<li class="listitem">
          Improved the performance of strand rescheduling.
        </li>
<li class="listitem">
          Added support for <code class="literal">g++</code> 4.7 when compiling in C++11 mode.
        </li>
<li class="listitem">
          Fixed a problem where <code class="computeroutput"><span class="identifier">signal_set</span></code>
          handlers were not being delivered when the <code class="computeroutput"><span class="identifier">io_service</span></code>
          was constructed with a <code class="computeroutput"><span class="identifier">concurrency_hint</span></code>
          of 1.
        </li>
</ul></div>
<h4>
<a name="asio.history.h6"></a>
      <span><a name="asio.history.asio_1_8_0"></a></span><a class="link" href="history.html#asio.history.asio_1_8_0">Asio
      1.8.0</a>
    </h4>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
          Added a new class template <code class="computeroutput"><span class="identifier">basic_waitable_timer</span></code>
          based around the C++11 clock type requirements. It may be used with the
          clocks from the C++11 <code class="computeroutput"><span class="special">&lt;</span><span class="identifier">chrono</span><span class="special">&gt;</span></code>
          library facility or, if those are not available, Boost.Chrono. The typedefs
          <code class="computeroutput"><span class="identifier">high_resolution_timer</span></code>,
          <code class="computeroutput"><span class="identifier">steady_timer</span></code> and <code class="computeroutput"><span class="identifier">system_timer</span></code> may be used to create timer
          objects for the standard clock types.
        </li>
<li class="listitem">
          Added a new <code class="computeroutput"><span class="identifier">windows</span><span class="special">::</span><span class="identifier">object_handle</span></code> class for performing waits
          on Windows kernel objects. Thanks go to Boris Schaeling for contributing
          substantially to the development of this feature.
        </li>
<li class="listitem">
          On Linux, <code class="computeroutput"><span class="identifier">connect</span><span class="special">()</span></code>
          can return EAGAIN in certain circumstances. Remapped this to another error
          so that it doesn't look like a non-blocking operation.
        </li>
<li class="listitem">
          Fixed a compile error on NetBSD.
        </li>
<li class="listitem">
          Fixed deadlock on Mac OS X.
        </li>
<li class="listitem">
          Fixed a regression in <code class="computeroutput"><span class="identifier">buffered_write_stream</span></code>.
        </li>
<li class="listitem">
          Fixed a non-paged pool "leak" on Windows when an <code class="computeroutput"><span class="identifier">io_service</span></code> is repeatedly run without
          anything to do.
        </li>
<li class="listitem">
          Reverted earlier change to allow some speculative operations to be performed
          without holding the lock, as it introduced a race condition in some multithreaded
          scenarios.
        </li>
<li class="listitem">
          Fixed a bug where the second buffer in an array of two buffers may be ignored
          if the first buffer is empty.
        </li>
</ul></div>
<h4>
<a name="asio.history.h7"></a>
      <span><a name="asio.history.asio_1_6_1"></a></span><a class="link" href="history.html#asio.history.asio_1_6_1">Asio
      1.6.1</a>
    </h4>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
          Implemented various performance improvements, including:
          <div class="itemizedlist"><ul class="itemizedlist" type="circle">
<li class="listitem">
                Using thread-local operation queues in single-threaded use cases
                (i.e. when <code class="computeroutput"><span class="identifier">concurrency_hint</span></code>
                is 1) to eliminate a lock/unlock pair.
              </li>
<li class="listitem">
                Allowing some <code class="computeroutput"><span class="identifier">epoll_reactor</span></code>
                speculative operations to be performed without holding the lock.
              </li>
<li class="listitem">
                Improving locality of reference by performing an <code class="computeroutput"><span class="identifier">epoll_reactor</span></code>'s
                I/O operation immediately before the corresponding handler is called.
                This also improves scalability across CPUs when multiple threads
                are running the <code class="computeroutput"><span class="identifier">io_service</span></code>.
              </li>
<li class="listitem">
                Specialising asynchronous read and write operations for buffer sequences
                that are arrays (<code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">array</span></code>
                or <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">array</span></code>) of exactly two buffers.
              </li>
</ul></div>
        </li>
<li class="listitem">
          Fixed a compile error in the regex overload of <code class="computeroutput"><span class="identifier">async_read_until</span></code>.
        </li>
<li class="listitem">
          Fixed a Windows-specific compile error by explicitly specifying the <code class="computeroutput"><span class="identifier">signal</span><span class="special">()</span></code>
          function from the global namespace.
        </li>
<li class="listitem">
          Changed the <code class="computeroutput"><span class="identifier">deadline_timer</span></code>
          implementation so that it does not read the clock unless the timer heap
          is non-empty.
        </li>
<li class="listitem">
          Changed the SSL stream's buffers' sizes so that they are large enough to
          hold a complete TLS record.
        </li>
<li class="listitem">
          Fixed the behaviour of the synchronous <code class="computeroutput"><span class="identifier">null_buffers</span></code>
          operations so that they obey the user's non-blocking setting.
        </li>
<li class="listitem">
          Changed to set the size of the select <code class="computeroutput"><span class="identifier">fd_set</span></code>
          at runtime when using Windows.
        </li>
<li class="listitem">
          Disabled an MSVC warning due to const qualifier being applied to function
          type.
        </li>
<li class="listitem">
          Fixed a crash that occurs when using the Intel C++ compiler.
        </li>
<li class="listitem">
          Changed the initialisation of the OpenSSL library so that it supports all
          available algorithms.
        </li>
<li class="listitem">
          Fixed the SSL error mapping used when the session is gracefully shut down.
        </li>
<li class="listitem">
          Added some latency test programs.
        </li>
<li class="listitem">
          Clarified that a read operation ends when the buffer is full.
        </li>
<li class="listitem">
          Fixed an exception safety issue in <code class="computeroutput"><span class="identifier">epoll_reactor</span></code>
          initialisation.
        </li>
<li class="listitem">
          Made the number of strand implementations configurable by defining <code class="computeroutput"><span class="special">(</span><span class="identifier">BOOST_</span><span class="special">)</span><span class="identifier">ASIO_STRAND_IMPLEMENTATIONS</span></code>
          to the desired number.
        </li>
<li class="listitem">
          Added support for a new <code class="computeroutput"><span class="special">(</span><span class="identifier">BOOST_</span><span class="special">)</span><span class="identifier">ASIO_ENABLE_SEQUENTIAL_STRAND_ALLOCATION</span></code>
          flag which switches the allocation of strand implementations to use a round-robin
          approach rather than hashing.
        </li>
<li class="listitem">
          Fixed potential strand starvation issue that can occur when <code class="computeroutput"><span class="identifier">strand</span><span class="special">.</span><span class="identifier">post</span><span class="special">()</span></code>
          is used.
        </li>
</ul></div>
<h4>
<a name="asio.history.h8"></a>
      <span><a name="asio.history.asio_1_6_0"></a></span><a class="link" href="history.html#asio.history.asio_1_6_0">Asio
      1.6.0</a>
    </h4>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
          Improved support for C++0x move construction to further reduce copying
          of handler objects. In certain designs it is possible to eliminate virtually
          all copies. Move support is now enabled when compiling in <code class="literal">-std=c++0x</code>
          mode on g++ 4.5 or higher.
        </li>
<li class="listitem">
          Added build support for platforms that don't provide either of <code class="computeroutput"><span class="identifier">signal</span><span class="special">()</span></code>
          or <code class="computeroutput"><span class="identifier">sigaction</span><span class="special">()</span></code>.
        </li>
<li class="listitem">
          Changed to use C++0x variadic templates when they are available, rather
          than generating function overloads using the Boost.Preprocessor library.
        </li>
<li class="listitem">
          Ensured the value of <code class="computeroutput"><span class="identifier">errno</span></code>
          is preserved across the implementation's signal handler.
        </li>
<li class="listitem">
          On Windows, ensured the count of outstanding work is decremented for abandoned
          operations (i.e. operations that are being cleaned up within the <code class="computeroutput"><span class="identifier">io_service</span></code> destructor).
        </li>
<li class="listitem">
          Fixed behaviour of zero-length reads and writes in the new SSL implementation.
        </li>
<li class="listitem">
          Added support for building with OpenSSL 1.0 when <code class="computeroutput"><span class="identifier">OPENSSL_NO_SSL2</span></code>
          is defined.
        </li>
<li class="listitem">
          Changed most examples to treat a failure by an accept operation as non-fatal.
        </li>
<li class="listitem">
          Fixed an error in the <code class="literal">tick_count_timer</code> example by making
          the duration type signed. Previously, a wait on an already-passed deadline
          would not return for a very long time.
        </li>
</ul></div>
<h4>
<a name="asio.history.h9"></a>
      <span><a name="asio.history.asio_1_5_3"></a></span><a class="link" href="history.html#asio.history.asio_1_5_3">Asio
      1.5.3</a>
    </h4>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
          Added a new, completely rewritten SSL implementation. The new implementation
          compiles faster, shows substantially improved performance, and supports
          custom memory allocation and handler invocation. It includes new API features
          such as certificate verification callbacks and has improved error reporting.
          The new implementation is source-compatible with the old for most uses.
          However, if necessary, the old implementation may still be used by defining
          <code class="computeroutput"><span class="special">(</span><span class="identifier">BOOST_</span><span class="special">)</span><span class="identifier">ASIO_ENABLE_OLD_SSL</span></code>.
        </li>
<li class="listitem">
          Added new <code class="computeroutput"><span class="identifier">asio</span><span class="special">::</span><span class="identifier">buffer</span><span class="special">()</span></code>
          overloads for <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">array</span></code>, when available. The support is
          automatically enabled when compiling in <code class="literal">-std=c++0x</code> mode
          on g++ 4.3 or higher, or when using MSVC 10. The support may be explicitly
          enabled by defining <code class="computeroutput"><span class="special">(</span><span class="identifier">BOOST_</span><span class="special">)</span><span class="identifier">ASIO_HAS_STD_ARRAY</span></code>,
          or disabled by defining <code class="computeroutput"><span class="special">(</span><span class="identifier">BOOST_</span><span class="special">)</span><span class="identifier">ASIO_DISABLE_STD_ARRAY</span></code>.
        </li>
<li class="listitem">
          Changed to use the C++0x standard library templates <code class="computeroutput"><span class="identifier">array</span></code>,
          <code class="computeroutput"><span class="identifier">shared_ptr</span></code>, <code class="computeroutput"><span class="identifier">weak_ptr</span></code> and <code class="computeroutput"><span class="identifier">atomic</span></code>
          when they are available, rather than the Boost equivalents.
        </li>
<li class="listitem">
          Support for <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">error_code</span></code> and <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">system_error</span></code>
          is no longer enabled by default for g++ 4.5, as that compiler's standard
          library does not implement <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">system_error</span><span class="special">::</span><span class="identifier">what</span><span class="special">()</span></code> correctly.
        </li>
</ul></div>
<h4>
<a name="asio.history.h10"></a>
      <span><a name="asio.history.asio_1_5_2"></a></span><a class="link" href="history.html#asio.history.asio_1_5_2">Asio
      1.5.2</a>
    </h4>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
          Added support for C++0x move construction and assignment to sockets, serial
          ports, POSIX descriptors and Windows handles.
        </li>
<li class="listitem">
          Added support for the <code class="computeroutput"><span class="identifier">fork</span><span class="special">()</span></code> system call. Programs that use <code class="computeroutput"><span class="identifier">fork</span><span class="special">()</span></code>
          must call <code class="computeroutput"><span class="identifier">io_service</span><span class="special">.</span><span class="identifier">notify_fork</span><span class="special">()</span></code>
          at the appropriate times. Two new examples have been added showing how
          to use this feature.
        </li>
<li class="listitem">
          Cleaned up the handling of errors reported by the <code class="computeroutput"><span class="identifier">close</span><span class="special">()</span></code> system call. In particular, assume that
          most operating systems won't have <code class="computeroutput"><span class="identifier">close</span><span class="special">()</span></code> fail with <code class="computeroutput"><span class="identifier">EWOULDBLOCK</span></code>,
          but if it does then set the blocking mode and restart the call. If any
          other error occurs, assume the descriptor is closed.
        </li>
<li class="listitem">
          The kqueue flag <code class="computeroutput"><span class="identifier">EV_ONESHOT</span></code>
          seems to cause problems on some versions of Mac OS X, with the <code class="computeroutput"><span class="identifier">io_service</span></code> destructor getting stuck inside
          the <code class="computeroutput"><span class="identifier">close</span><span class="special">()</span></code>
          system call. Changed the kqueue backend to use <code class="computeroutput"><span class="identifier">EV_CLEAR</span></code>
          instead.
        </li>
<li class="listitem">
          Changed exception reporting to include the function name in exception
          <code class="computeroutput"><span class="identifier">what</span><span class="special">()</span></code>
          messages.
        </li>
<li class="listitem">
          Fixed an insufficient initialisers warning with MinGW.
        </li>
<li class="listitem">
          Changed the <code class="computeroutput"><span class="identifier">shutdown_service</span><span class="special">()</span></code> member functions to be private.
        </li>
<li class="listitem">
          Added archetypes for testing socket option functions.
        </li>
<li class="listitem">
          Added a missing lock in <code class="computeroutput"><span class="identifier">signal_set_service</span><span class="special">::</span><span class="identifier">cancel</span><span class="special">()</span></code>.
        </li>
<li class="listitem">
          Fixed a copy/paste error in <code class="computeroutput"><span class="identifier">SignalHandler</span></code>
          example.
        </li>
<li class="listitem">
          Added the inclusion of the signal header to <code class="computeroutput"><span class="identifier">signal_set_service</span><span class="special">.</span><span class="identifier">hpp</span></code>
          so that constants like <code class="computeroutput"><span class="identifier">NSIG</span></code>
          may be used.
        </li>
<li class="listitem">
          Changed the <code class="computeroutput"><span class="identifier">signal_set_service</span></code>
          implementation so that it doesn't assume that <code class="computeroutput"><span class="identifier">SIGRTMAX</span></code>
          is a compile-time constant.
        </li>
<li class="listitem">
          Changed the Boost.Asio examples so that they don't use Boost.Thread's convenience
          header. Use the header file that is specifically for the boost::thread
          class instead.
        </li>
</ul></div>
<h4>
<a name="asio.history.h11"></a>
      <span><a name="asio.history.asio_1_5_1"></a></span><a class="link" href="history.html#asio.history.asio_1_5_1">Asio
      1.5.1</a>
    </h4>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
          Added support for signal handling, using a new class called <code class="computeroutput"><span class="identifier">signal_set</span></code>. Programs may add one or more
          signals to the set, and then perform an <code class="computeroutput"><span class="identifier">async_wait</span><span class="special">()</span></code> operation. The specified handler will
          be called when one of the signals occurs. The same signal number may registered
          with multiple <code class="computeroutput"><span class="identifier">signal_set</span></code>
          objects, however the signal number must be used only with Asio.
        </li>
<li class="listitem">
          Added handler tracking, a new debugging aid. When enabled by defining
          <code class="computeroutput"><span class="special">(</span><span class="identifier">BOOST_</span><span class="special">)</span><span class="identifier">ASIO_ENABLE_HANDLER_TRACKING</span></code>,
          Asio writes debugging output to the standard error stream. The output records
          asynchronous operations and the relationships between their handlers. It
          may be post-processed using the included <code class="literal">handlerviz.pl</code>
          tool to create a visual representation of the handlers (requires GraphViz).
        </li>
<li class="listitem">
          Fixed a bug in <code class="computeroutput"><span class="identifier">asio</span><span class="special">::</span><span class="identifier">streambuf</span></code> where the <code class="computeroutput"><span class="identifier">consume</span><span class="special">()</span></code> function did not always update the internal
          buffer pointers correctly. The problem may occur when the <code class="computeroutput"><span class="identifier">asio</span><span class="special">::</span><span class="identifier">streambuf</span></code> is filled with data using the
          standard C++ member functions such as <code class="computeroutput"><span class="identifier">sputn</span><span class="special">()</span></code>. (Note: the problem does not manifest
          when the streambuf is populated by the Asio free functions <code class="computeroutput"><span class="identifier">read</span><span class="special">()</span></code>,
          <code class="computeroutput"><span class="identifier">async_read</span><span class="special">()</span></code>,
          <code class="computeroutput"><span class="identifier">read_until</span><span class="special">()</span></code>
          or <code class="computeroutput"><span class="identifier">async_read_until</span><span class="special">()</span></code>.)
        </li>
<li class="listitem">
          Fixed a bug on kqueue-based platforms, where reactor read operations that
          return false from their <code class="computeroutput"><span class="identifier">perform</span><span class="special">()</span></code> function are not correctly re-registered
          with kqueue.
        </li>
<li class="listitem">
          Support for <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">error_code</span></code> and <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">system_error</span></code>
          is no longer enabled by default for MSVC10, as that compiler's standard
          library does not implement <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">system_error</span><span class="special">::</span><span class="identifier">what</span><span class="special">()</span></code> correctly.
        </li>
<li class="listitem">
          Modified the <code class="computeroutput"><span class="identifier">buffers_iterator</span><span class="special">&lt;&gt;</span></code> and <code class="computeroutput"><span class="identifier">ip</span><span class="special">::</span><span class="identifier">basic_resolver_iterator</span></code>
          classes so that the value_type typedefs are non-const byte types.
        </li>
</ul></div>
<h4>
<a name="asio.history.h12"></a>
      <span><a name="asio.history.asio_1_5_0"></a></span><a class="link" href="history.html#asio.history.asio_1_5_0">Asio
      1.5.0</a>
    </h4>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
          Added support for timeouts on socket iostreams, such as <code class="computeroutput"><span class="identifier">ip</span><span class="special">::</span><span class="identifier">tcp</span><span class="special">::</span><span class="identifier">iostream</span></code>.
          A timeout is set by calling <code class="computeroutput"><span class="identifier">expires_at</span><span class="special">()</span></code> or <code class="computeroutput"><span class="identifier">expires_from_now</span><span class="special">()</span></code> to establish a deadline. Any socket operations
          which occur past the deadline will put the iostream into a bad state.
        </li>
<li class="listitem">
          Added a new <code class="computeroutput"><span class="identifier">error</span><span class="special">()</span></code>
          member function to socket iostreams, for retrieving the error code from
          the most recent system call.
        </li>
<li class="listitem">
          Added a new <code class="computeroutput"><span class="identifier">basic_deadline_timer</span><span class="special">::</span><span class="identifier">cancel_one</span><span class="special">()</span></code> function. This function lets you cancel
          a single waiting handler on a timer. Handlers are cancelled in FIFO order.
        </li>
<li class="listitem">
          Added a new <code class="computeroutput"><span class="identifier">transfer_exactly</span><span class="special">()</span></code> completion condition. This can be used
          to send or receive a specified number of bytes even if the total size of
          the buffer (or buffer sequence) is larger.
        </li>
<li class="listitem">
          Added new free functions <code class="computeroutput"><span class="identifier">connect</span><span class="special">()</span></code> and <code class="computeroutput"><span class="identifier">async_connect</span><span class="special">()</span></code>. These operations try each endpoint in
          a list until the socket is successfully connected.
        </li>
<li class="listitem">
          Extended the <code class="computeroutput"><span class="identifier">buffer_size</span><span class="special">()</span></code> function so that it works for buffer
          sequences in addition to individual buffers.
        </li>
<li class="listitem">
          Added a new <code class="computeroutput"><span class="identifier">buffer_copy</span><span class="special">()</span></code> function that can be used to copy the
          raw bytes between individual buffers and buffer sequences.
        </li>
<li class="listitem">
          Added new non-throwing overloads of <code class="computeroutput"><span class="identifier">read</span><span class="special">()</span></code>, <code class="computeroutput"><span class="identifier">read_at</span><span class="special">()</span></code>, <code class="computeroutput"><span class="identifier">write</span><span class="special">()</span></code> and <code class="computeroutput"><span class="identifier">write_at</span><span class="special">()</span></code> that do not require a completion condition.
        </li>
<li class="listitem">
          Added friendlier compiler errors for when a completion handler does not
          meet the necessary type requirements. When C++0x is available (currently
          supported for g++ 4.5 or later, and MSVC 10), <code class="computeroutput"><span class="keyword">static_assert</span></code>
          is also used to generate an informative error message. This checking may
          be disabled by defining <code class="computeroutput"><span class="special">(</span><span class="identifier">BOOST_</span><span class="special">)</span><span class="identifier">ASIO_DISABLE_HANDLER_TYPE_REQUIREMENTS</span></code>.
        </li>
<li class="listitem">
          Added support for using <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">error_code</span></code>
          and <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">system_error</span></code>, when available. The support
          is automatically enabled when compiling in <code class="literal">-std=c++0x</code>
          mode on g++ 4.5 or higher, or when using MSVC 10. The support may be explicitly
          enabled by defining <code class="computeroutput"><span class="identifier">ASIO_HAS_STD_SYSTEM_ERROR</span></code>,
          or disabled by defining <code class="computeroutput"><span class="identifier">ASIO_DISABLE_STD_SYSTEM_ERROR</span></code>.
          (Available in non-Boost version of Asio only.)
        </li>
<li class="listitem">
          Made the <code class="computeroutput"><span class="identifier">is_loopback</span><span class="special">()</span></code>,
          <code class="computeroutput"><span class="identifier">is_unspecified</span><span class="special">()</span></code>
          and <code class="computeroutput"><span class="identifier">is_multicast</span><span class="special">()</span></code>
          functions consistently available across the <code class="computeroutput"><span class="identifier">ip</span><span class="special">::</span><span class="identifier">address</span></code>,
          <code class="computeroutput"><span class="identifier">ip</span><span class="special">::</span><span class="identifier">address_v4</span></code> and <code class="computeroutput"><span class="identifier">ip</span><span class="special">::</span><span class="identifier">address_v6</span></code>
          classes.
        </li>
<li class="listitem">
          Added new <code class="computeroutput"><span class="identifier">non_blocking</span><span class="special">()</span></code> functions for managing the non-blocking
          behaviour of a socket or descriptor. The <code class="computeroutput"><span class="identifier">io_control</span><span class="special">()</span></code> commands named <code class="computeroutput"><span class="identifier">non_blocking_io</span></code>
          are now deprecated in favour of these new functions.
        </li>
<li class="listitem">
          Added new <code class="computeroutput"><span class="identifier">native_non_blocking</span><span class="special">()</span></code> functions for managing the non-blocking
          mode of the underlying socket or descriptor. These functions are intended
          to allow the encapsulation of arbitrary non-blocking system calls as asynchronous
          operations, in a way that is transparent to the user of the socket object.
          The functions have no effect on the behaviour of the synchronous operations
          of the socket or descriptor.
        </li>
<li class="listitem">
          Added the <code class="computeroutput"><span class="identifier">io_control</span><span class="special">()</span></code>
          member function for socket acceptors.
        </li>
<li class="listitem">
          For consistency with the C++0x standard library, deprecated the <code class="computeroutput"><span class="identifier">native_type</span></code> typedefs in favour of <code class="computeroutput"><span class="identifier">native_handle_type</span></code>, and the <code class="computeroutput"><span class="identifier">native</span><span class="special">()</span></code>
          member functions in favour of <code class="computeroutput"><span class="identifier">native_handle</span><span class="special">()</span></code>.
        </li>
<li class="listitem">
          Added a <code class="computeroutput"><span class="identifier">release</span><span class="special">()</span></code>
          member function to posix descriptors. This function releases ownership
          of the underlying native descriptor to the caller.
        </li>
<li class="listitem">
          Added support for sequenced packet sockets (<code class="computeroutput"><span class="identifier">SOCK_SEQPACKET</span></code>).
        </li>
<li class="listitem">
          Added a new <code class="computeroutput"><span class="identifier">io_service</span><span class="special">::</span><span class="identifier">stopped</span><span class="special">()</span></code> function that can be used to determine
          whether the <code class="computeroutput"><span class="identifier">io_service</span></code>
          has stopped (i.e. a <code class="computeroutput"><span class="identifier">reset</span><span class="special">()</span></code> call is needed prior to any further calls
          to <code class="computeroutput"><span class="identifier">run</span><span class="special">()</span></code>,
          <code class="computeroutput"><span class="identifier">run_one</span><span class="special">()</span></code>,
          <code class="computeroutput"><span class="identifier">poll</span><span class="special">()</span></code>
          or <code class="computeroutput"><span class="identifier">poll_one</span><span class="special">()</span></code>).
        </li>
<li class="listitem">
          Reduced the copying of handler function objects.
        </li>
<li class="listitem">
          Added support for C++0x move construction to further reduce copying of
          handler objects. Move support is enabled when compiling in <code class="literal">-std=c++0x</code>
          mode on g++ 4.5 or higher, or when using MSVC10.
        </li>
<li class="listitem">
          Removed the dependency on OS-provided macros for the well-known IPv4 and
          IPv6 addresses. This should eliminate the annoying "missing braces
          around initializer" warnings.
        </li>
<li class="listitem">
          Reduced the size of <code class="computeroutput"><span class="identifier">ip</span><span class="special">::</span><span class="identifier">basic_endpoint</span><span class="special">&lt;&gt;</span></code> objects (such as <code class="computeroutput"><span class="identifier">ip</span><span class="special">::</span><span class="identifier">tcp</span><span class="special">::</span><span class="identifier">endpoint</span></code> and <code class="computeroutput"><span class="identifier">ip</span><span class="special">::</span><span class="identifier">udp</span><span class="special">::</span><span class="identifier">endpoint</span></code>).
        </li>
<li class="listitem">
          Changed the reactor backends to assume that any descriptors or sockets
          added using <code class="computeroutput"><span class="identifier">assign</span><span class="special">()</span></code>
          may have been <code class="computeroutput"><span class="identifier">dup</span><span class="special">()</span></code>-ed,
          and so require explicit deregistration from the reactor.
        </li>
<li class="listitem">
          Changed the SSL error category to return error strings from the OpenSSL
          library.
        </li>
<li class="listitem">
          Changed the separate compilation support such that, to use Asio's SSL capabilities,
          you should also include 'asio/ssl/impl/src.hpp` in one source file in your
          program.
        </li>
<li class="listitem">
          Removed the deprecated member functions named <code class="computeroutput"><span class="identifier">io_service</span><span class="special">()</span></code>. The <code class="computeroutput"><span class="identifier">get_io_service</span><span class="special">()</span></code> member functions should be used instead.
        </li>
<li class="listitem">
          Removed the deprecated typedefs <code class="computeroutput"><span class="identifier">resolver_query</span></code>
          and <code class="computeroutput"><span class="identifier">resolver_iterator</span></code> from
          the <code class="computeroutput"><span class="identifier">ip</span><span class="special">::</span><span class="identifier">tcp</span></code>, <code class="computeroutput"><span class="identifier">ip</span><span class="special">::</span><span class="identifier">udp</span></code>
          and <code class="computeroutput"><span class="identifier">ip</span><span class="special">::</span><span class="identifier">icmp</span></code> classes.
        </li>
<li class="listitem">
          Fixed a compile error on some versions of g++ due to anonymous enums.
        </li>
<li class="listitem">
          Added an explicit cast to the <code class="computeroutput"><span class="identifier">FIONBIO</span></code>
          constant to int to suppress a compiler warning on some platforms.
        </li>
<li class="listitem">
          Fixed warnings reported by g++'s <code class="literal">-Wshadow</code> compiler option.
        </li>
</ul></div>
<h4>
<a name="asio.history.h13"></a>
      <span><a name="asio.history.asio_1_4_8"></a></span><a class="link" href="history.html#asio.history.asio_1_4_8">Asio
      1.4.8</a>
    </h4>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
          Fixed an integer overflow problem that occurs when <code class="computeroutput"><span class="identifier">ip</span><span class="special">::</span><span class="identifier">address_v4</span><span class="special">::</span><span class="identifier">broadcast</span><span class="special">()</span></code> is used on 64-bit platforms.
        </li>
<li class="listitem">
          Fixed a problem on older Linux kernels (where epoll is used without <code class="computeroutput"><span class="identifier">timerfd</span></code> support) that prevents timely
          delivery of <code class="computeroutput"><span class="identifier">deadline_timer</span></code>
          handlers, after the program has been running for some time.
        </li>
</ul></div>
<h4>
<a name="asio.history.h14"></a>
      <span><a name="asio.history.asio_1_4_7"></a></span><a class="link" href="history.html#asio.history.asio_1_4_7">Asio
      1.4.7</a>
    </h4>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
          Fixed a problem on kqueue-based platforms where a <code class="computeroutput"><span class="identifier">deadline_timer</span></code>
          may never fire if the <code class="computeroutput"><span class="identifier">io_service</span></code>
          is running in a background thread.
        </li>
<li class="listitem">
          Fixed a const-correctness issue that prevented valid uses of <code class="computeroutput"><span class="identifier">has_service</span><span class="special">&lt;&gt;</span></code>
          from compiling.
        </li>
<li class="listitem">
          Fixed MinGW cross-compilation.
        </li>
<li class="listitem">
          Removed dependency on deprecated Boost.System functions (Boost.Asio only).
        </li>
<li class="listitem">
          Ensured <code class="computeroutput"><span class="identifier">close</span><span class="special">()</span></code>/<code class="computeroutput"><span class="identifier">closesocket</span><span class="special">()</span></code>
          failures are correctly propagated.
        </li>
<li class="listitem">
          Added a check for errors returned by <code class="computeroutput"><span class="identifier">InitializeCriticalSectionAndSpinCount</span></code>.
        </li>
<li class="listitem">
          Added support for hardware flow control on QNX.
        </li>
<li class="listitem">
          Always use <code class="computeroutput"><span class="identifier">pselect</span><span class="special">()</span></code>
          on HP-UX, if it is available.
        </li>
<li class="listitem">
          Ensured handler arguments are passed as lvalues.
        </li>
<li class="listitem">
          Fixed Windows build when thread support is disabled.
        </li>
<li class="listitem">
          Fixed a Windows-specific problem where <code class="computeroutput"><span class="identifier">deadline_timer</span></code>
          objects with expiry times set more than 5 minutes in the future may never
          expire.
        </li>
<li class="listitem">
          Fixed the resolver backend on BSD platforms so that an empty service name
          resolves to port number <code class="computeroutput"><span class="number">0</span></code>,
          as per the documentation.
        </li>
<li class="listitem">
          Fixed read operations so that they do not accept buffer sequences of type
          <code class="computeroutput"><span class="identifier">const_buffers_1</span></code>.
        </li>
<li class="listitem">
          Redefined <code class="computeroutput"><span class="identifier">Protocol</span></code> and
          <code class="computeroutput"><span class="identifier">id</span></code> to avoid clashing with
          Objective-C++ keywords.
        </li>
<li class="listitem">
          Fixed a <code class="computeroutput"><span class="identifier">vector</span></code> reallocation
          performance issue that can occur when there are many active <code class="computeroutput"><span class="identifier">deadline_timer</span></code> objects.
        </li>
<li class="listitem">
          Fixed the kqueue backend so that it compiles on NetBSD.
        </li>
<li class="listitem">
          Fixed the socket <code class="computeroutput"><span class="identifier">io_control</span><span class="special">()</span></code> implementation on 64-bit Mac OS X and
          BSD platforms.
        </li>
<li class="listitem">
          Fixed a Windows-specific problem where failures from <code class="computeroutput"><span class="identifier">accept</span><span class="special">()</span></code> are incorrectly treated as successes.
        </li>
<li class="listitem">
          Deprecated the separate compilation header <code class="computeroutput"><span class="identifier">asio</span><span class="special">/</span><span class="identifier">impl</span><span class="special">/</span><span class="identifier">src</span><span class="special">.</span><span class="identifier">cpp</span></code>
          in favour of <code class="computeroutput"><span class="identifier">asio</span><span class="special">/</span><span class="identifier">impl</span><span class="special">/</span><span class="identifier">src</span><span class="special">.</span><span class="identifier">hpp</span></code>.
        </li>
</ul></div>
<h4>
<a name="asio.history.h15"></a>
      <span><a name="asio.history.asio_1_4_6"></a></span><a class="link" href="history.html#asio.history.asio_1_4_6">Asio
      1.4.6</a>
    </h4>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
          Reduced compile times. (Note that some programs may need to add additional
          <code class="computeroutput"><span class="preprocessor">#include</span></code>s, e.g. if the
          program uses boost::array but does not explicitly include <code class="computeroutput"><span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">array</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span></code>.)
        </li>
<li class="listitem">
          Reduced the size of generated code.
        </li>
<li class="listitem">
          Refactored <code class="computeroutput"><span class="identifier">deadline_timer</span></code>
          implementation to improve performance.
        </li>
<li class="listitem">
          Improved multiprocessor scalability on Windows by using a dedicated hidden
          thread to wait for timers.
        </li>
<li class="listitem">
          Improved performance of <code class="computeroutput"><span class="identifier">asio</span><span class="special">::</span><span class="identifier">streambuf</span></code>
          with <code class="computeroutput"><span class="identifier">async_read</span><span class="special">()</span></code>
          and <code class="computeroutput"><span class="identifier">async_read_until</span><span class="special">()</span></code>.
          These read operations now use the existing capacity of the <code class="computeroutput"><span class="identifier">streambuf</span></code> when reading, rather than limiting
          the read to 512 bytes.
        </li>
<li class="listitem">
          Added optional separate compilation. To enable, include <code class="computeroutput"><span class="identifier">asio</span><span class="special">/</span><span class="identifier">impl</span><span class="special">/</span><span class="identifier">src</span><span class="special">.</span><span class="identifier">cpp</span></code>
          in one source file in a program, then build the program with <code class="computeroutput"><span class="special">(</span><span class="identifier">BOOST_</span><span class="special">)</span><span class="identifier">ASIO_SEPARATE_COMPILATION</span></code>
          defined in the project/compiler settings. Alternatively, <code class="computeroutput"><span class="special">(</span><span class="identifier">BOOST_</span><span class="special">)</span><span class="identifier">ASIO_DYN_LINK</span></code>
          may be defined to build a separately-compiled Asio as part of a shared
          library.
        </li>
<li class="listitem">
          Added new macro <code class="computeroutput"><span class="special">(</span><span class="identifier">BOOST_</span><span class="special">)</span><span class="identifier">ASIO_DISABLE_FENCED_BLOCK</span></code>
          to permit the disabling of memory fences around completion handlers, even
          if thread support is enabled.
        </li>
<li class="listitem">
          Reworked timeout examples to better illustrate typical use cases.
        </li>
<li class="listitem">
          Ensured that handler arguments are passed as const types.
        </li>
<li class="listitem">
          Fixed incorrect parameter order in <code class="computeroutput"><span class="identifier">null_buffers</span></code>
          variant of <code class="computeroutput"><span class="identifier">async_send_to</span></code>.
        </li>
<li class="listitem">
          Ensured unsigned char is used with <code class="computeroutput"><span class="identifier">isdigit</span></code>
          in <code class="computeroutput"><span class="identifier">getaddrinfo</span></code> emulation.
        </li>
<li class="listitem">
          Fixed handling of very small but non-zero timeouts.
        </li>
<li class="listitem">
          Fixed crash that occurred when an empty buffer sequence was passed to a
          composed read or write operation.
        </li>
<li class="listitem">
          Added missing operator+ overload in <code class="computeroutput"><span class="identifier">buffers_iterator</span></code>.
        </li>
<li class="listitem">
          Implemented cancellation of <code class="computeroutput"><span class="identifier">null_buffers</span></code>
          operations on Windows.
        </li>
</ul></div>
<h4>
<a name="asio.history.h16"></a>
      <span><a name="asio.history.asio_1_4_5"></a></span><a class="link" href="history.html#asio.history.asio_1_4_5">Asio
      1.4.5</a>
    </h4>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
          Improved performance.
        </li>
<li class="listitem">
          Reduced compile times.
        </li>
<li class="listitem">
          Reduced the size of generated code.
        </li>
<li class="listitem">
          Extended the guarantee that background threads don't call user code to
          all asynchronous operations.
        </li>
<li class="listitem">
          Changed to use edge-triggered epoll on Linux.
        </li>
<li class="listitem">
          Changed to use <code class="computeroutput"><span class="identifier">timerfd</span></code>
          for dispatching timers on Linux, when available.
        </li>
<li class="listitem">
          Changed to use one-shot notifications with kqueue on Mac OS X and BSD platforms.
        </li>
<li class="listitem">
          Added a bitmask type <code class="computeroutput"><span class="identifier">ip</span><span class="special">::</span><span class="identifier">resolver_query_base</span><span class="special">::</span><span class="identifier">flags</span></code>
          as per the TR2 proposal. This type prevents implicit conversion from <code class="computeroutput"><span class="keyword">int</span></code> to <code class="computeroutput"><span class="identifier">flags</span></code>,
          allowing the compiler to catch cases where users incorrectly pass a numeric
          port number as the service name.
        </li>
<li class="listitem">
          Added <code class="computeroutput"><span class="preprocessor">#define</span> <span class="identifier">NOMINMAX</span></code>
          for all Windows compilers. Users can define <code class="computeroutput"><span class="special">(</span><span class="identifier">BOOST_</span><span class="special">)</span><span class="identifier">ASIO_NO_NOMINMAX</span></code> to suppress this definition.
        </li>
<li class="listitem">
          Fixed a bug where 0-byte asynchronous reads were incorrectly passing an
          <code class="computeroutput"><span class="identifier">error</span><span class="special">::</span><span class="identifier">eof</span></code> result to the completion handler.
        </li>
<li class="listitem">
          Changed the <code class="computeroutput"><span class="identifier">io_control</span><span class="special">()</span></code> member functions to always call <code class="computeroutput"><span class="identifier">ioctl</span></code> on the underlying descriptor when
          modifying blocking mode.
        </li>
<li class="listitem">
          Changed the resolver implementation so that it no longer requires the typedefs
          <code class="computeroutput"><span class="identifier">InternetProtocol</span><span class="special">::</span><span class="identifier">resolver_query</span></code> and <code class="computeroutput"><span class="identifier">InternetProtocol</span><span class="special">::</span><span class="identifier">resolver_iterator</span></code>,
          as neither typedef is part of the documented <code class="computeroutput"><span class="identifier">InternetProtocol</span></code>
          requirements. The corresponding typedefs in the <code class="computeroutput"><span class="identifier">ip</span><span class="special">::</span><span class="identifier">tcp</span></code>,
          <code class="computeroutput"><span class="identifier">ip</span><span class="special">::</span><span class="identifier">udp</span></code> and <code class="computeroutput"><span class="identifier">ip</span><span class="special">::</span><span class="identifier">icmp</span></code>
          classes have been deprecated.
        </li>
<li class="listitem">
          Fixed out-of-band handling for reactors not based on <code class="computeroutput"><span class="identifier">select</span><span class="special">()</span></code>.
        </li>
<li class="listitem">
          Added new <code class="computeroutput"><span class="special">(</span><span class="identifier">BOOST_</span><span class="special">)</span><span class="identifier">ASIO_DISABLE_THREADS</span></code>
          macro that allows Asio's threading support to be independently disabled.
        </li>
<li class="listitem">
          Minor documentation improvements.
        </li>
</ul></div>
<h4>
<a name="asio.history.h17"></a>
      <span><a name="asio.history.asio_1_4_4"></a></span><a class="link" href="history.html#asio.history.asio_1_4_4">Asio
      1.4.4</a>
    </h4>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
          Added a new HTTP Server 4 example illustrating the use of stackless coroutines
          with Asio.
        </li>
<li class="listitem">
          Changed handler allocation and invocation to use <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">addressof</span></code>
          to get the address of handler objects, rather than applying <code class="computeroutput"><span class="keyword">operator</span><span class="special">&amp;</span></code>
          directly.
        </li>
<li class="listitem">
          Restricted MSVC buffer debugging workaround to 2008, as it causes a crash
          with 2010 beta 2.
        </li>
<li class="listitem">
          Fixed a problem with the lifetime of handler memory, where Windows needs
          the <code class="computeroutput"><span class="identifier">OVERLAPPED</span></code> structure
          to be valid until both the initiating function call has returned and the
          completion packet has been delivered.
        </li>
<li class="listitem">
          Don't block signals while performing system calls, but instead restart
          the calls if they are interrupted.
        </li>
<li class="listitem">
          Documented the guarantee made by strand objects with respect to order of
          handler invocation.
        </li>
<li class="listitem">
          Changed strands to use a pool of implementations, to make copying of strands
          cheaper.
        </li>
<li class="listitem">
          Ensured that kqueue support is enabled for BSD platforms.
        </li>
<li class="listitem">
          Added a <code class="computeroutput"><span class="identifier">boost_</span></code> prefix to
          the <code class="computeroutput"><span class="keyword">extern</span> <span class="string">"C"</span></code>
          thread entry point function.
        </li>
<li class="listitem">
          In <code class="computeroutput"><span class="identifier">getaddrinfo</span></code> emulation,
          only check the socket type (<code class="computeroutput"><span class="identifier">SOCK_STREAM</span></code>
          or <code class="computeroutput"><span class="identifier">SOCK_DGRAM</span></code>) if a service
          name has been specified. This should allow the emulation to work with raw
          sockets.
        </li>
<li class="listitem">
          Added a workaround for some broken Windows firewalls that make a socket
          appear bound to 0.0.0.0 when it is in fact bound to 127.0.0.1.
        </li>
<li class="listitem">
          Applied a fix for reported excessive CPU usage under Solaris.
        </li>
<li class="listitem">
          Added some support for platforms that use older compilers such as g++ 2.95.
        </li>
</ul></div>
<h4>
<a name="asio.history.h18"></a>
      <span><a name="asio.history.asio_1_4_3"></a></span><a class="link" href="history.html#asio.history.asio_1_4_3">Asio
      1.4.3</a>
    </h4>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
          Added a new ping example to illustrate the use of ICMP sockets.
        </li>
<li class="listitem">
          Changed the <code class="computeroutput"><span class="identifier">buffered</span><span class="special">*</span><span class="identifier">_stream</span><span class="special">&lt;&gt;</span></code>
          templates to treat 0-byte reads and writes as no-ops, to comply with the
          documented type requirements for <code class="computeroutput"><span class="identifier">SyncReadStream</span></code>,
          <code class="computeroutput"><span class="identifier">AsyncReadStream</span></code>, <code class="computeroutput"><span class="identifier">SyncWriteStream</span></code> and <code class="computeroutput"><span class="identifier">AsyncWriteStream</span></code>.
        </li>
<li class="listitem">
          Changed some instances of the <code class="computeroutput"><span class="keyword">throw</span></code>
          keyword to <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">throw_exception</span><span class="special">()</span></code>
          to allow Asio to be used when exception support is disabled. Note that
          the SSL wrappers still require exception support.
        </li>
<li class="listitem">
          Made Asio compatible with the OpenSSL 1.0 beta.
        </li>
<li class="listitem">
          Eliminated a redundant system call in the Solaris /dev/poll backend.
        </li>
<li class="listitem">
          Fixed a bug in resizing of the bucket array in the internal hash maps.
        </li>
<li class="listitem">
          Ensured correct propagation of the error code when a synchronous accept
          fails.
        </li>
<li class="listitem">
          Ensured correct propagation of the error code when a synchronous read or
          write on a Windows <code class="computeroutput"><span class="identifier">HANDLE</span></code>
          fails.
        </li>
<li class="listitem">
          Fixed failures reported when <code class="computeroutput"><span class="identifier">_GLIBCXX_DEBUG</span></code>
          is defined.
        </li>
<li class="listitem">
          Fixed custom memory allocation support for timers.
        </li>
<li class="listitem">
          Tidied up various warnings reported by g++.
        </li>
<li class="listitem">
          Various documentation improvements, including more obvious hyperlinks to
          function overloads, header file information, examples for the handler type
          requirements, and adding enum values to the index.
        </li>
</ul></div>
<h4>
<a name="asio.history.h19"></a>
      <span><a name="asio.history.asio_1_4_2"></a></span><a class="link" href="history.html#asio.history.asio_1_4_2">Asio
      1.4.2</a>
    </h4>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
          Implement automatic resizing of the bucket array in the internal hash maps.
          This is to improve performance for very large numbers of asynchronous operations
          and also to reduce memory usage for very small numbers. A new macro <code class="computeroutput"><span class="special">(</span><span class="identifier">BOOST_</span><span class="special">)</span><span class="identifier">ASIO_HASH_MAP_BUCKETS</span></code>
          may be used to tweak the sizes used for the bucket arrays. (N.B. this feature
          introduced a bug which was fixed in Asio 1.4.3 / Boost 1.40.)
        </li>
<li class="listitem">
          Add performance optimisation for the Windows IOCP backend for when no timers
          are used.
        </li>
<li class="listitem">
          Prevent locale settings from affecting formatting of TCP and UDP endpoints.
        </li>
<li class="listitem">
          Fix a memory leak that occurred when an asynchronous SSL operation's completion
          handler threw an exception.
        </li>
<li class="listitem">
          Fix the implementation of <code class="computeroutput"><span class="identifier">io_control</span><span class="special">()</span></code> so that it adheres to the documented
          type requirements for IoControlCommand.
        </li>
<li class="listitem">
          Fix incompatibility between Asio and ncurses.h.
        </li>
<li class="listitem">
          On Windows, specifically handle the case when an overlapped <code class="computeroutput"><span class="identifier">ReadFile</span></code> call fails with <code class="computeroutput"><span class="identifier">ERROR_MORE_DATA</span></code>. This enables a hack
          where a <code class="computeroutput"><span class="identifier">windows</span><span class="special">::</span><span class="identifier">stream_handle</span></code> can be used with a message-oriented
          named pipe.
        </li>
<li class="listitem">
          Fix system call wrappers to always clear the error on success, as POSIX
          allows successful system calls to modify errno.
        </li>
<li class="listitem">
          Don't include termios.h if <code class="computeroutput"><span class="special">(</span><span class="identifier">BOOST_</span><span class="special">)</span><span class="identifier">ASIO_DISABLE_SERIAL_PORT</span></code> is defined.
        </li>
<li class="listitem">
          Cleaned up some more MSVC level 4 warnings.
        </li>
<li class="listitem">
          Various documentation fixes.
        </li>
</ul></div>
<h4>
<a name="asio.history.h20"></a>
      <span><a name="asio.history.asio_1_4_1"></a></span><a class="link" href="history.html#asio.history.asio_1_4_1">Asio
      1.4.1</a>
    </h4>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
          Improved compatibility with some Windows firewall software.
        </li>
<li class="listitem">
          Ensured arguments to <code class="computeroutput"><span class="identifier">windows</span><span class="special">::</span><span class="identifier">overlapped_ptr</span><span class="special">::</span><span class="identifier">complete</span><span class="special">()</span></code> are correctly passed to the completion
          handler.
        </li>
<li class="listitem">
          Fixed a link problem and multicast failure on QNX.
        </li>
<li class="listitem">
          Fixed a compile error in SSL support on MinGW / g++ 3.4.5.
        </li>
<li class="listitem">
          Drop back to using a pipe for notification if eventfd is not available
          at runtime on Linux.
        </li>
<li class="listitem">
          Various minor bug and documentation fixes.
        </li>
</ul></div>
<h4>
<a name="asio.history.h21"></a>
      <span><a name="asio.history.asio_1_4_0"></a></span><a class="link" href="history.html#asio.history.asio_1_4_0">Asio
      1.4.0</a>
    </h4>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
          Enhanced CompletionCondition concept with the signature <code class="computeroutput"><span class="identifier">size_t</span>
          <span class="identifier">CompletionCondition</span><span class="special">(</span><span class="identifier">error_code</span> <span class="identifier">ec</span><span class="special">,</span> <span class="identifier">size_t</span> <span class="identifier">total</span><span class="special">)</span></code>,
          where the return value indicates the maximum number of bytes to be transferred
          on the next read or write operation. (The old CompletionCondition signature
          is still supported for backwards compatibility).
        </li>
<li class="listitem">
          New <code class="computeroutput"><span class="identifier">windows</span><span class="special">::</span><span class="identifier">overlapped_ptr</span></code> class to allow arbitrary
          overlapped I/O functions (such as <code class="computeroutput"><span class="identifier">TransmitFile</span></code>)
          to be used with Asio.
        </li>
<li class="listitem">
          On recent versions of Linux, an <code class="computeroutput"><span class="identifier">eventfd</span></code>
          descriptor is now used (rather than a pipe) to interrupt a blocked select/epoll
          reactor.
        </li>
<li class="listitem">
          Added const overloads of <code class="computeroutput"><span class="identifier">lowest_layer</span><span class="special">()</span></code>.
        </li>
<li class="listitem">
          Synchronous read, write, accept and connect operations are now thread safe
          (meaning that it is now permitted to perform concurrent synchronous operations
          on an individual socket, if supported by the OS).
        </li>
<li class="listitem">
          Reactor-based <code class="computeroutput"><span class="identifier">io_service</span></code>
          implementations now use lazy initialisation to reduce the memory usage
          of an <code class="computeroutput"><span class="identifier">io_service</span></code> object
          used only as a message queue.
        </li>
</ul></div>
<h4>
<a name="asio.history.h22"></a>
      <span><a name="asio.history.asio_1_2_0"></a></span><a class="link" href="history.html#asio.history.asio_1_2_0">Asio
      1.2.0</a>
    </h4>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
          Added support for serial ports.
        </li>
<li class="listitem">
          Added support for UNIX domain sockets.
        </li>
<li class="listitem">
          Added support for raw sockets and ICMP.
        </li>
<li class="listitem">
          Added wrappers for POSIX stream-oriented file descriptors (excluding regular
          files).
        </li>
<li class="listitem">
          Added wrappers for Windows stream-oriented <code class="computeroutput"><span class="identifier">HANDLE</span></code>s
          such as named pipes (requires <code class="computeroutput"><span class="identifier">HANDLE</span></code>s
          that work with I/O completion ports).
        </li>
<li class="listitem">
          Added wrappers for Windows random-access <code class="computeroutput"><span class="identifier">HANDLE</span></code>s
          such as files (requires <code class="computeroutput"><span class="identifier">HANDLE</span></code>s
          that work with I/O completion ports).
        </li>
<li class="listitem">
          Added support for reactor-style operations (i.e. they report readiness
          but perform no I/O) using a new <code class="computeroutput"><span class="identifier">null_buffers</span></code>
          type.
        </li>
<li class="listitem">
          Added an iterator type for bytewise traversal of buffer sequences.
        </li>
<li class="listitem">
          Added new <code class="computeroutput"><span class="identifier">read_until</span><span class="special">()</span></code>
          and <code class="computeroutput"><span class="identifier">async_read_until</span><span class="special">()</span></code>
          overloads that take a user-defined function object for locating message
          boundaries.
        </li>
<li class="listitem">
          Added an experimental two-lock queue (enabled by defining <code class="computeroutput"><span class="special">(</span><span class="identifier">BOOST_</span><span class="special">)</span><span class="identifier">ASIO_ENABLE_TWO_LOCK_QUEUE</span></code>)
          that may provide better <code class="computeroutput"><span class="identifier">io_service</span></code>
          scalability across many processors.
        </li>
<li class="listitem">
          Various fixes, performance improvements, and more complete coverage of
          the custom memory allocation support.
        </li>
</ul></div>
<h4>
<a name="asio.history.h23"></a>
      <span><a name="asio.history.asio_1_0_0"></a></span><a class="link" href="history.html#asio.history.asio_1_0_0">Asio
      1.0.0</a>
    </h4>
<p>
      First stable release of Asio.
    </p>
</div>
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
<td align="left"></td>
<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2014 Christopher M. Kohlhoff<p>
        Distributed under the Boost Software License, Version 1.0. (See accompanying
        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
      </p>
</div></td>
</tr></table>
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