ceph/src/boost/libs/type_traits/doc/html/boost_typetraits/reference/has_trivial_move_constructor.html

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  26 <div class="titlepage"><div><div><h3 class="title">
  27 <a name="boost_typetraits.reference.has_trivial_move_constructor"></a><a class="link" href="has_trivial_move_constructor.html" title="has_trivial_move_constructor">has_trivial_move_constructor</a>
  28 </h3></div></div></div>
  29 <pre class="programlisting"><span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span>
  30 <span class="keyword">struct</span> <span class="identifier">has_trivial_move_constructor</span> <span class="special">:</span> <span class="keyword">public</span> <em class="replaceable"><code><a class="link" href="integral_constant.html" title="integral_constant">true_type</a>-or-<a class="link" href="integral_constant.html" title="integral_constant">false_type</a></code></em> <span class="special">{};</span>
  31 </pre>
  32 <p>
  33         <span class="bold"><strong>Inherits:</strong></span> If T is a (possibly cv-qualified)
  34         type with a trivial move-constructor then inherits from <a class="link" href="integral_constant.html" title="integral_constant">true_type</a>,
  35         otherwise inherits from <a class="link" href="integral_constant.html" title="integral_constant">false_type</a>.
  36       </p>
  37 <p>
  38         If a type has a trivial move-constructor then the constructor has the same
  39         effect as copying the bits of one object to the other: calls to the constructor
  40         can be safely replaced with a call to <code class="computeroutput"><span class="identifier">memcpy</span></code>.
  41       </p>
  42 <p>
  43         <span class="bold"><strong>Compiler Compatibility:</strong></span> Without some (as
  44         yet unspecified) help from the compiler, has_trivial_move_constructor will
  45         never report that a user-defined class or struct has a trivial constructor;
  46         this is always safe, if possibly sub-optimal. In addition C++11's <code class="computeroutput"><span class="keyword">decltype</span></code> is required to correctly support
  47         deleted or private move constructors. Currently (June 2015) compilers that
  48         have the necessary <a class="link" href="../intrinsics.html" title="Support for Compiler Intrinsics">intrinsics</a>
  49         to ensure that this trait "just works" include Clang, GCC-5.1,
  50         and MSVC-12.0. You may also test to see if the necessary <a class="link" href="../intrinsics.html" title="Support for Compiler Intrinsics">intrinsics</a>
  51         are available by checking to see if the macro <code class="computeroutput"><span class="identifier">BOOST_HAS_TRIVIAL_MOVE_CONSTRUCTOR</span></code>
  52         is defined.
  53       </p>
  54 <p>
  55         <span class="bold"><strong>Header:</strong></span> <code class="computeroutput"> <span class="preprocessor">#include</span>
  56         <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">type_traits</span><span class="special">/</span><span class="identifier">has_trivial_move_constructor</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span></code>
  57         or <code class="computeroutput"> <span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">type_traits</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span></code>
  58       </p>
  59 <p>
  60         <span class="bold"><strong>Examples:</strong></span>
  61       </p>
  62 <div class="blockquote"><blockquote class="blockquote"><p>
  63           <code class="computeroutput"><span class="identifier">has_trivial_move_constructor</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;</span></code> inherits from <code class="computeroutput"><a class="link" href="integral_constant.html" title="integral_constant">true_type</a></code>.
  64         </p></blockquote></div>
  65 <div class="blockquote"><blockquote class="blockquote"><p>
  66           <code class="computeroutput"><span class="identifier">has_trivial_move_constructor</span><span class="special">&lt;</span><span class="keyword">char</span><span class="special">*&gt;::</span><span class="identifier">type</span></code>
  67           is the type <code class="computeroutput"><a class="link" href="integral_constant.html" title="integral_constant">true_type</a></code>.
  68         </p></blockquote></div>
  69 <div class="blockquote"><blockquote class="blockquote"><p>
  70           <code class="computeroutput"><span class="identifier">has_trivial_move_constructor</span><span class="special">&lt;</span><span class="keyword">int</span> <span class="special">(*)(</span><span class="keyword">long</span><span class="special">)&gt;::</span><span class="identifier">value</span></code>
  71           is an integral constant expression that evaluates to <span class="emphasis"><em>true</em></span>.
  72         </p></blockquote></div>
  73 <div class="blockquote"><blockquote class="blockquote"><p>
  74           <code class="computeroutput"><span class="identifier">has_trivial_move_constructor</span><span class="special">&lt;</span><span class="identifier">MyClass</span><span class="special">&gt;::</span><span class="identifier">value</span></code>
  75           is an integral constant expression that evaluates to <span class="emphasis"><em>false</em></span>.
  76         </p></blockquote></div>
  77 <div class="blockquote"><blockquote class="blockquote"><p>
  78           <code class="computeroutput"><span class="identifier">has_trivial_move_constructor</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;::</span><span class="identifier">value_type</span></code>
  79           is the type <code class="computeroutput"><span class="keyword">bool</span></code>.
  80         </p></blockquote></div>
  81 </div>
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  84 <td align="right"><div class="copyright-footer">Copyright &#169; 2000, 2011 Adobe Systems Inc, David Abrahams,
  85       Frederic Bron, Steve Cleary, Beman Dawes, Aleksey Gurtovoy, Howard Hinnant,
  86       Jesse Jones, Mat Marcus, Itay Maman, John Maddock, Alexander Nasonov, Thorsten
  87       Ottosen, Roman Perepelitsa, Robert Ramey, Jeremy Siek, Robert Stewart and Steven
  88       Watanabe<p>
  89         Distributed under the Boost Software License, Version 1.0. (See accompanying
  90         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>)
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