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| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h2 class="title" style="clear: both"> |
| <a name="thread.emulations"></a><a class="link" href="emulations.html" title="Emulations">Emulations</a> |
| </h2></div></div></div> |
| <div class="toc"><dl class="toc"> |
| <dt><span class="section"><a href="emulations.html#thread.emulations.delete"><code class="computeroutput"><span class="special">=</span><span class="keyword">delete</span></code> emulation</a></span></dt> |
| <dt><span class="section"><a href="emulations.html#thread.emulations.move">Move semantics</a></span></dt> |
| <dt><span class="section"><a href="emulations.html#thread.emulations.bool_explicit_conversion">Bool explicit |
| conversion</a></span></dt> |
| <dt><span class="section"><a href="emulations.html#thread.emulations.scoped_enums">Scoped Enums</a></span></dt> |
| </dl></div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="thread.emulations.delete"></a><a class="link" href="emulations.html#thread.emulations.delete" title="=delete emulation"><code class="computeroutput"><span class="special">=</span><span class="keyword">delete</span></code> emulation</a> |
| </h3></div></div></div> |
| <p> |
| C++11 allows to delete some implicitly generated functions as constructors |
| and assignment using '= delete' as in |
| </p> |
| <pre class="programlisting"><span class="keyword">public</span><span class="special">:</span> |
| <span class="identifier">thread</span><span class="special">(</span><span class="identifier">thread</span> <span class="keyword">const</span><span class="special">&)</span> <span class="special">=</span> <span class="keyword">delete</span><span class="special">;</span> |
| </pre> |
| <p> |
| On compilers not supporting this feature, Boost.Thread relays on a partial |
| simulation, it declares the function as private without definition. |
| </p> |
| <pre class="programlisting"><span class="keyword">private</span><span class="special">:</span> |
| <span class="identifier">thread</span><span class="special">(</span><span class="identifier">thread</span> <span class="special">&);</span> |
| </pre> |
| <p> |
| The emulation is partial as the private function can be used for overload |
| resolution for some compilers and prefer it to other overloads that need |
| a conversion. See below the consequences on the move semantic emulation. |
| </p> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="thread.emulations.move"></a><a class="link" href="emulations.html#thread.emulations.move" title="Move semantics">Move semantics</a> |
| </h3></div></div></div> |
| <div class="toc"><dl class="toc"> |
| <dt><span class="section"><a href="emulations.html#thread.emulations.move.deprecated">Deprecated Version |
| 2 interface</a></span></dt> |
| <dt><span class="section"><a href="emulations.html#thread.emulations.move.portable">Portable interface</a></span></dt> |
| </dl></div> |
| <p> |
| In order to implement Movable classes, move parameters and return types Boost.Thread |
| uses the rvalue reference when the compiler support it. On compilers not |
| supporting it Boost.Thread uses either the emulation provided by Boost.Move |
| or the emulation provided by the previous versions of Boost.Thread depending |
| whether <code class="computeroutput"><span class="identifier">BOOST_THREAD_USES_MOVE</span></code> |
| is defined or not. This macros is unset by default when <code class="computeroutput"><span class="identifier">BOOST_THREAD_VERSION</span></code> |
| is 2. Since <code class="computeroutput"><span class="identifier">BOOST_THREAD_VERSION</span></code> |
| 3, <code class="computeroutput"><span class="identifier">BOOST_THREAD_USES_MOVE</span></code> |
| is defined. |
| </p> |
| <div class="section"> |
| <div class="titlepage"><div><div><h4 class="title"> |
| <a name="thread.emulations.move.deprecated"></a><a class="link" href="emulations.html#thread.emulations.move.deprecated" title="Deprecated Version 2 interface">Deprecated Version |
| 2 interface</a> |
| </h4></div></div></div> |
| <div class="toc"><dl class="toc"> |
| <dt><span class="section"><a href="emulations.html#thread.emulations.move.deprecated.Helper">Helpers |
| class and function</a></span></dt> |
| <dt><span class="section"><a href="emulations.html#thread.emulations.move.deprecated.movable">Movable |
| emulation</a></span></dt> |
| </dl></div> |
| <p> |
| Previous to version 1.50, Boost.Thread make use of its own move semantic |
| emulation which had more limitations than the provided by Boost.Move. In |
| addition, it is of interest of the whole Boost community that Boost.Thread |
| uses Boost.Move so that boost::thread can be stored on Movable aware containers. |
| </p> |
| <p> |
| To preserve backward compatibility at least during some releases, Boost.Thread |
| allows the user to use the deprecated move semantic emulation defining |
| BOOST_THREAD_DONT_USE_MOVE. |
| </p> |
| <p> |
| Many aspects of move semantics can be emulated for compilers not supporting |
| rvalue references and Boost.Thread legacy offers tools for that purpose. |
| </p> |
| <div class="section"> |
| <div class="titlepage"><div><div><h5 class="title"> |
| <a name="thread.emulations.move.deprecated.Helper"></a><a class="link" href="emulations.html#thread.emulations.move.deprecated.Helper" title="Helpers class and function">Helpers |
| class and function</a> |
| </h5></div></div></div> |
| <p> |
| Next follows the interface of the legacy move semantic helper class and |
| function. |
| </p> |
| <pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span> |
| <span class="special">{</span> |
| <span class="keyword">namespace</span> <span class="identifier">detail</span> |
| <span class="special">{</span> |
| <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> <span class="identifier">T</span><span class="special">></span> |
| <span class="keyword">struct</span> <span class="identifier">thread_move_t</span> |
| <span class="special">{</span> |
| <span class="keyword">explicit</span> <span class="identifier">thread_move_t</span><span class="special">(</span><span class="identifier">T</span><span class="special">&</span> <span class="identifier">t_</span><span class="special">);</span> |
| <span class="identifier">T</span><span class="special">&</span> <span class="keyword">operator</span><span class="special">*()</span> <span class="keyword">const</span><span class="special">;</span> |
| <span class="identifier">T</span><span class="special">*</span> <span class="keyword">operator</span><span class="special">->()</span> <span class="keyword">const</span><span class="special">;</span> |
| <span class="keyword">private</span><span class="special">:</span> |
| <span class="keyword">void</span> <span class="keyword">operator</span><span class="special">=(</span><span class="identifier">thread_move_t</span><span class="special">&);</span> |
| <span class="special">};</span> |
| <span class="special">}</span> |
| <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> <span class="identifier">T</span><span class="special">></span> |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">detail</span><span class="special">::</span><span class="identifier">thread_move_t</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">move</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">detail</span><span class="special">::</span><span class="identifier">thread_move_t</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">t</span><span class="special">);</span> |
| <span class="special">}</span> |
| </pre> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h5 class="title"> |
| <a name="thread.emulations.move.deprecated.movable"></a><a class="link" href="emulations.html#thread.emulations.move.deprecated.movable" title="Movable emulation">Movable |
| emulation</a> |
| </h5></div></div></div> |
| <p> |
| We can write a MovableOny class as follows. You just need to follow these |
| simple steps: |
| </p> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| Add a conversion to the <code class="computeroutput"><span class="identifier">detail</span><span class="special">::</span><span class="identifier">thread_move_t</span><span class="special"><</span><span class="identifier">classname</span><span class="special">></span></code> |
| </li> |
| <li class="listitem"> |
| Make the copy constructor private. |
| </li> |
| <li class="listitem"> |
| Write a constructor taking the parameter as <code class="computeroutput"><span class="identifier">detail</span><span class="special">::</span><span class="identifier">thread_move_t</span><span class="special"><</span><span class="identifier">classname</span><span class="special">></span></code> |
| </li> |
| <li class="listitem"> |
| Write an assignment taking the parameter as <code class="computeroutput"><span class="identifier">detail</span><span class="special">::</span><span class="identifier">thread_move_t</span><span class="special"><</span><span class="identifier">classname</span><span class="special">></span></code> |
| </li> |
| </ul></div> |
| <p> |
| For example the thread class defines the following: |
| </p> |
| <pre class="programlisting"><span class="keyword">class</span> <span class="identifier">thread</span> |
| <span class="special">{</span> |
| <span class="comment">// ...</span> |
| <span class="keyword">private</span><span class="special">:</span> |
| <span class="identifier">thread</span><span class="special">(</span><span class="identifier">thread</span><span class="special">&);</span> |
| <span class="identifier">thread</span><span class="special">&</span> <span class="keyword">operator</span><span class="special">=(</span><span class="identifier">thread</span><span class="special">&);</span> |
| <span class="keyword">public</span><span class="special">:</span> |
| <span class="identifier">detail</span><span class="special">::</span><span class="identifier">thread_move_t</span><span class="special"><</span><span class="identifier">thread</span><span class="special">></span> <span class="identifier">move</span><span class="special">()</span> |
| <span class="special">{</span> |
| <span class="identifier">detail</span><span class="special">::</span><span class="identifier">thread_move_t</span><span class="special"><</span><span class="identifier">thread</span><span class="special">></span> <span class="identifier">x</span><span class="special">(*</span><span class="keyword">this</span><span class="special">);</span> |
| <span class="keyword">return</span> <span class="identifier">x</span><span class="special">;</span> |
| <span class="special">}</span> |
| <span class="keyword">operator</span> <span class="identifier">detail</span><span class="special">::</span><span class="identifier">thread_move_t</span><span class="special"><</span><span class="identifier">thread</span><span class="special">>()</span> |
| <span class="special">{</span> |
| <span class="keyword">return</span> <span class="identifier">move</span><span class="special">();</span> |
| <span class="special">}</span> |
| <span class="identifier">thread</span><span class="special">(</span><span class="identifier">detail</span><span class="special">::</span><span class="identifier">thread_move_t</span><span class="special"><</span><span class="identifier">thread</span><span class="special">></span> <span class="identifier">x</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="identifier">thread_info</span><span class="special">=</span><span class="identifier">x</span><span class="special">-></span><span class="identifier">thread_info</span><span class="special">;</span> |
| <span class="identifier">x</span><span class="special">-></span><span class="identifier">thread_info</span><span class="special">.</span><span class="identifier">reset</span><span class="special">();</span> |
| <span class="special">}</span> |
| <span class="identifier">thread</span><span class="special">&</span> <span class="keyword">operator</span><span class="special">=(</span><span class="identifier">detail</span><span class="special">::</span><span class="identifier">thread_move_t</span><span class="special"><</span><span class="identifier">thread</span><span class="special">></span> <span class="identifier">x</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="identifier">thread</span> <span class="identifier">new_thread</span><span class="special">(</span><span class="identifier">x</span><span class="special">);</span> |
| <span class="identifier">swap</span><span class="special">(</span><span class="identifier">new_thread</span><span class="special">);</span> |
| <span class="keyword">return</span> <span class="special">*</span><span class="keyword">this</span><span class="special">;</span> |
| <span class="special">}</span> |
| <span class="comment">// ...</span> |
| |
| <span class="special">};</span> |
| </pre> |
| </div> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h4 class="title"> |
| <a name="thread.emulations.move.portable"></a><a class="link" href="emulations.html#thread.emulations.move.portable" title="Portable interface">Portable interface</a> |
| </h4></div></div></div> |
| <div class="toc"><dl class="toc"> |
| <dt><span class="section"><a href="emulations.html#thread.emulations.move.portable.NO_COPYABLE"><code class="computeroutput"><span class="identifier">BOOST_THREAD_NO_COPYABLE</span><span class="special">(</span><span class="identifier">CLASS</span><span class="special">)</span></code></a></span></dt> |
| <dt><span class="section"><a href="emulations.html#thread.emulations.move.portable.MOVABLE"><code class="computeroutput"><span class="identifier">BOOST_THREAD_MOVABLE</span><span class="special">(</span><span class="identifier">CLASS</span><span class="special">)</span></code></a></span></dt> |
| <dt><span class="section"><a href="emulations.html#thread.emulations.move.portable.MOVABLE_ONLY"><code class="computeroutput"><span class="identifier">BOOST_THREAD_MOVABLE_ONLY</span><span class="special">(</span><span class="identifier">CLASS</span><span class="special">)</span></code></a></span></dt> |
| <dt><span class="section"><a href="emulations.html#thread.emulations.move.portable.COPYABLE_AND_MOVABLE"><code class="computeroutput"><span class="identifier">BOOST_THREAD_COPYABLE_AND_MOVABLE</span><span class="special">(</span><span class="identifier">CLASS</span><span class="special">)</span></code></a></span></dt> |
| <dt><span class="section"><a href="emulations.html#thread.emulations.move.portable.RV_REF"><code class="computeroutput"><span class="identifier">BOOST_THREAD_RV_REF</span><span class="special">(</span><span class="identifier">TYPE</span><span class="special">)</span></code>, |
| <code class="computeroutput"><span class="identifier">BOOST_THREAD_RV_REF_BEG</span></code> |
| and <code class="computeroutput"><span class="identifier">BOOST_THREAD_RV_REF_END</span></code></a></span></dt> |
| <dt><span class="section"><a href="emulations.html#thread.emulations.move.portable.RV"><code class="computeroutput"><span class="identifier">BOOST_THREAD_RV</span><span class="special">(</span><span class="identifier">V</span><span class="special">)</span></code></a></span></dt> |
| <dt><span class="section"><a href="emulations.html#thread.emulations.move.portable.MAKE_RV_REF"><code class="computeroutput"><span class="identifier">BOOST_THREAD_MAKE_RV_REF</span><span class="special">(</span><span class="identifier">RVALUE</span><span class="special">)</span></code></a></span></dt> |
| <dt><span class="section"><a href="emulations.html#thread.emulations.move.portable.DCL_MOVABLE"><code class="computeroutput"><span class="identifier">BOOST_THREAD_DCL_MOVABLE</span></code>, <code class="computeroutput"><span class="identifier">BOOST_THREAD_DCL_MOVABLE_BEG</span><span class="special">(</span><span class="identifier">T1</span><span class="special">)</span></code> and |
| <code class="computeroutput"><span class="identifier">BOOST_THREAD_DCL_MOVABLE_END</span></code></a></span></dt> |
| </dl></div> |
| <p> |
| In order to make the library code portable Boost.Thread uses some macros |
| that will use either the ones provided by Boost.Move or the deprecated |
| move semantics provided by previous versions of Boost.Thread. |
| </p> |
| <p> |
| See the Boost.Move documentation for a complete description on how to declare |
| new Movable classes and its limitations. |
| </p> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <code class="computeroutput"><span class="identifier">BOOST_THREAD_RV_REF</span><span class="special">(</span><span class="identifier">TYPE</span><span class="special">)</span></code> is the equivalent of <code class="computeroutput"><span class="identifier">BOOST_RV_REF</span><span class="special">(</span><span class="identifier">TYPE</span><span class="special">)</span></code> |
| </li> |
| <li class="listitem"> |
| <code class="computeroutput"><span class="identifier">BOOST_THREAD_RV_REF_BEG</span></code> |
| is the equivalent of <code class="computeroutput"><span class="identifier">BOOST_RV_REF_BEG</span><span class="special">(</span><span class="identifier">TYPE</span><span class="special">)</span></code> |
| </li> |
| <li class="listitem"> |
| <code class="computeroutput"><span class="identifier">BOOST_THREAD_RV_REF_END</span></code> |
| is the equivalent of <code class="computeroutput"><span class="identifier">BOOST_RV_REF_END</span><span class="special">(</span><span class="identifier">TYPE</span><span class="special">)</span></code> |
| </li> |
| <li class="listitem"> |
| <code class="computeroutput"><span class="identifier">BOOST_THREAD_FWD_REF</span><span class="special">(</span><span class="identifier">TYPE</span><span class="special">)</span></code> is the equivalent of `BOOST_FWD_REF(TYPE) |
| </li> |
| </ul></div> |
| <p> |
| In addition the following macros are needed to make the code portable: |
| </p> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <code class="computeroutput"><span class="identifier">BOOST_THREAD_RV</span><span class="special">(</span><span class="identifier">V</span><span class="special">)</span></code> |
| macro to access the rvalue from a BOOST_THREAD_RV_REF(TYPE), |
| </li> |
| <li class="listitem"> |
| <code class="computeroutput"><span class="identifier">BOOST_THREAD_MAKE_RV_REF</span><span class="special">(</span><span class="identifier">RVALUE</span><span class="special">)</span></code> makes a rvalue. |
| </li> |
| <li class="listitem"> |
| <code class="computeroutput"><span class="identifier">BOOST_THREAD_DCL_MOVABLE</span><span class="special">(</span><span class="identifier">CLASS</span><span class="special">)</span></code> to avoid conflicts with Boost.Move |
| </li> |
| <li class="listitem"> |
| <code class="computeroutput"><span class="identifier">BOOST_THREAD_DCL_MOVABLE_BEG</span><span class="special">(</span><span class="identifier">T1</span><span class="special">)</span></code> and <code class="computeroutput"><span class="identifier">BOOST_THREAD_DCL_MOVABLE_END</span></code> |
| are variant of <code class="computeroutput"><span class="identifier">BOOST_THREAD_DCL_MOVABLE</span></code> |
| when the parameter is a template instantiation. |
| </li> |
| </ul></div> |
| <p> |
| Other macros are provided and must be included on the public section: |
| </p> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <code class="computeroutput"><span class="identifier">BOOST_THREAD_NO_COPYABLE</span></code> |
| declares a class no-copyable either deleting the copy constructors |
| and copy assignment or moving them to the private section. |
| </li> |
| <li class="listitem"> |
| <code class="computeroutput"><span class="identifier">BOOST_THREAD_MOVABLE</span><span class="special">(</span><span class="identifier">CLASS</span><span class="special">)</span></code> declares all the implicit conversions |
| to an rvalue-reference. |
| </li> |
| <li class="listitem"> |
| <code class="computeroutput"><span class="identifier">BOOST_THREAD_MOVABLE_ONLY</span><span class="special">(</span><span class="identifier">CLASS</span><span class="special">)</span></code> is the equivalent of <code class="computeroutput"><span class="identifier">BOOST_MOVABLE_BUT_NOT_COPYABLE</span><span class="special">(</span><span class="identifier">CLASS</span><span class="special">)</span></code> |
| </li> |
| <li class="listitem"> |
| <code class="computeroutput"><span class="identifier">BOOST_THREAD_COPYABLE_AND_MOVABLE</span><span class="special">(</span><span class="identifier">CLASS</span><span class="special">)</span></code> is the equivalent of <code class="computeroutput"><span class="identifier">BOOST_COPYABLE_AND_MOVABLE</span><span class="special">(</span><span class="identifier">CLASS</span><span class="special">)</span></code> |
| </li> |
| </ul></div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h5 class="title"> |
| <a name="thread.emulations.move.portable.NO_COPYABLE"></a><a class="link" href="emulations.html#thread.emulations.move.portable.NO_COPYABLE" title="BOOST_THREAD_NO_COPYABLE(CLASS)"><code class="computeroutput"><span class="identifier">BOOST_THREAD_NO_COPYABLE</span><span class="special">(</span><span class="identifier">CLASS</span><span class="special">)</span></code></a> |
| </h5></div></div></div> |
| <p> |
| This macro marks a class as no copyable, disabling copy construction |
| and assignment. |
| </p> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h5 class="title"> |
| <a name="thread.emulations.move.portable.MOVABLE"></a><a class="link" href="emulations.html#thread.emulations.move.portable.MOVABLE" title="BOOST_THREAD_MOVABLE(CLASS)"><code class="computeroutput"><span class="identifier">BOOST_THREAD_MOVABLE</span><span class="special">(</span><span class="identifier">CLASS</span><span class="special">)</span></code></a> |
| </h5></div></div></div> |
| <p> |
| This macro marks a class as movable, declaring all the implicit conversions |
| to an rvalue-reference. |
| </p> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h5 class="title"> |
| <a name="thread.emulations.move.portable.MOVABLE_ONLY"></a><a class="link" href="emulations.html#thread.emulations.move.portable.MOVABLE_ONLY" title="BOOST_THREAD_MOVABLE_ONLY(CLASS)"><code class="computeroutput"><span class="identifier">BOOST_THREAD_MOVABLE_ONLY</span><span class="special">(</span><span class="identifier">CLASS</span><span class="special">)</span></code></a> |
| </h5></div></div></div> |
| <p> |
| This macro marks a type as movable but not copyable, disabling copy construction |
| and assignment. The user will need to write a move constructor/assignment |
| to fully write a movable but not copyable class. |
| </p> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h5 class="title"> |
| <a name="thread.emulations.move.portable.COPYABLE_AND_MOVABLE"></a><a class="link" href="emulations.html#thread.emulations.move.portable.COPYABLE_AND_MOVABLE" title="BOOST_THREAD_COPYABLE_AND_MOVABLE(CLASS)"><code class="computeroutput"><span class="identifier">BOOST_THREAD_COPYABLE_AND_MOVABLE</span><span class="special">(</span><span class="identifier">CLASS</span><span class="special">)</span></code></a> |
| </h5></div></div></div> |
| <p> |
| This macro marks a type as copyable and movable. The user will need to |
| write a move constructor/assignment and a copy assignment to fully write |
| a copyable and movable class. |
| </p> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h5 class="title"> |
| <a name="thread.emulations.move.portable.RV_REF"></a><a class="link" href="emulations.html#thread.emulations.move.portable.RV_REF" title="BOOST_THREAD_RV_REF(TYPE), BOOST_THREAD_RV_REF_BEG and BOOST_THREAD_RV_REF_END"><code class="computeroutput"><span class="identifier">BOOST_THREAD_RV_REF</span><span class="special">(</span><span class="identifier">TYPE</span><span class="special">)</span></code>, |
| <code class="computeroutput"><span class="identifier">BOOST_THREAD_RV_REF_BEG</span></code> |
| and <code class="computeroutput"><span class="identifier">BOOST_THREAD_RV_REF_END</span></code></a> |
| </h5></div></div></div> |
| <p> |
| This macro is used to achieve portable syntax in move constructors and |
| assignments for classes marked as <code class="computeroutput"><span class="identifier">BOOST_THREAD_COPYABLE_AND_MOVABLE</span></code> |
| or <code class="computeroutput"><span class="identifier">BOOST_THREAD_MOVABLE_ONLY</span></code>. |
| </p> |
| <p> |
| <code class="computeroutput"><span class="identifier">BOOST_THREAD_RV_REF_BEG</span></code> |
| and <code class="computeroutput"><span class="identifier">BOOST_THREAD_RV_REF_END</span></code> |
| are used when the parameter end with a <code class="computeroutput"><span class="special">></span></code> |
| to avoid the compiler error. |
| </p> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h5 class="title"> |
| <a name="thread.emulations.move.portable.RV"></a><a class="link" href="emulations.html#thread.emulations.move.portable.RV" title="BOOST_THREAD_RV(V)"><code class="computeroutput"><span class="identifier">BOOST_THREAD_RV</span><span class="special">(</span><span class="identifier">V</span><span class="special">)</span></code></a> |
| </h5></div></div></div> |
| <p> |
| While Boost.Move emulation allows to access an rvalue reference <code class="computeroutput"><span class="identifier">BOOST_THREAD_RV_REF</span><span class="special">(</span><span class="identifier">TYPE</span><span class="special">)</span></code> |
| using the dot operator, the legacy defines the <code class="computeroutput"><span class="keyword">operator</span><span class="special">-></span></code>. We need then a macro <code class="computeroutput"><span class="identifier">BOOST_THREAD_RV</span></code> that mask this difference. |
| E.g. |
| </p> |
| <pre class="programlisting"><span class="identifier">thread</span><span class="special">(</span><span class="identifier">BOOST_THREAD_RV_REF</span><span class="special">(</span><span class="identifier">thread</span><span class="special">)</span> <span class="identifier">x</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="identifier">thread_info</span><span class="special">=</span><span class="identifier">BOOST_THREAD_RV</span><span class="special">(</span><span class="identifier">x</span><span class="special">).</span><span class="identifier">thread_info</span><span class="special">;</span> |
| <span class="identifier">BOOST_THREAD_RV</span><span class="special">(</span><span class="identifier">x</span><span class="special">).</span><span class="identifier">thread_info</span><span class="special">.</span><span class="identifier">reset</span><span class="special">();</span> |
| <span class="special">}</span> |
| </pre> |
| <p> |
| The use of this macros has reduced considerably the size of the Boost.Thread |
| move related code. |
| </p> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h5 class="title"> |
| <a name="thread.emulations.move.portable.MAKE_RV_REF"></a><a class="link" href="emulations.html#thread.emulations.move.portable.MAKE_RV_REF" title="BOOST_THREAD_MAKE_RV_REF(RVALUE)"><code class="computeroutput"><span class="identifier">BOOST_THREAD_MAKE_RV_REF</span><span class="special">(</span><span class="identifier">RVALUE</span><span class="special">)</span></code></a> |
| </h5></div></div></div> |
| <p> |
| While Boost.Move is the best C++03 move emulation there are some limitations |
| that impact the way the library can be used. For example, with the following |
| declarations |
| </p> |
| <pre class="programlisting"><span class="keyword">class</span> <span class="identifier">thread</span> <span class="special">{</span> |
| <span class="comment">// ...</span> |
| <span class="keyword">private</span><span class="special">:</span> |
| <span class="identifier">thread</span><span class="special">(</span><span class="identifier">thread</span> <span class="special">&);</span> |
| <span class="keyword">public</span><span class="special">:</span> |
| <span class="identifier">thread</span><span class="special">(</span><span class="identifier">rv</span><span class="special"><</span><span class="identifier">thread</span><span class="special">>&);</span> |
| <span class="comment">// ...</span> |
| <span class="special">};</span> |
| </pre> |
| <p> |
| This could not work on some compilers even if thread is convertible to |
| <code class="computeroutput"><span class="identifier">rv</span><span class="special"><</span><span class="identifier">thread</span><span class="special">></span></code> |
| because the compiler prefers the private copy constructor. |
| </p> |
| <pre class="programlisting"><span class="identifier">thread</span> <span class="identifier">mkth</span><span class="special">()</span> |
| <span class="special">{</span> |
| <span class="keyword">return</span> <span class="identifier">thread</span><span class="special">(</span><span class="identifier">f</span><span class="special">);</span> |
| <span class="special">}</span> |
| </pre> |
| <p> |
| On these compilers we need to use instead an explicit conversion. The |
| library provides a move member function that allows to workaround the |
| issue. |
| </p> |
| <pre class="programlisting"><span class="identifier">thread</span> <span class="identifier">mkth</span><span class="special">()</span> |
| <span class="special">{</span> |
| <span class="keyword">return</span> <span class="identifier">thread</span><span class="special">(</span><span class="identifier">f</span><span class="special">).</span><span class="identifier">move</span><span class="special">();</span> |
| <span class="special">}</span> |
| </pre> |
| <p> |
| Note that <code class="computeroutput"><span class="special">::</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">move</span></code> |
| can not be used in this case as thread is not implicitly convertible |
| to <code class="computeroutput"><span class="identifier">thread</span><span class="special">&</span></code>. |
| </p> |
| <pre class="programlisting"><span class="identifier">thread</span> <span class="identifier">mkth</span><span class="special">()</span> |
| <span class="special">{</span> |
| <span class="keyword">return</span> <span class="special">::</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">thread</span><span class="special">(</span><span class="identifier">f</span><span class="special">));</span> |
| <span class="special">}</span> |
| </pre> |
| <p> |
| To make the code portable Boost.Thread the user needs to use a macro |
| <code class="computeroutput"><span class="identifier">BOOST_THREAD_MAKE_RV_REF</span></code> |
| that can be used as in |
| </p> |
| <pre class="programlisting"><span class="identifier">thread</span> <span class="identifier">mkth</span><span class="special">()</span> |
| <span class="special">{</span> |
| <span class="keyword">return</span> <span class="identifier">BOOST_THREAD_MAKE_RV_REF</span><span class="special">(</span><span class="identifier">thread</span><span class="special">(</span><span class="identifier">f</span><span class="special">));</span> |
| <span class="special">}</span> |
| </pre> |
| <p> |
| Note that this limitation is shared also by the legacy Boost.Thread move |
| emulation. |
| </p> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h5 class="title"> |
| <a name="thread.emulations.move.portable.DCL_MOVABLE"></a><a class="link" href="emulations.html#thread.emulations.move.portable.DCL_MOVABLE" title="BOOST_THREAD_DCL_MOVABLE, BOOST_THREAD_DCL_MOVABLE_BEG(T1) and BOOST_THREAD_DCL_MOVABLE_END"><code class="computeroutput"><span class="identifier">BOOST_THREAD_DCL_MOVABLE</span></code>, <code class="computeroutput"><span class="identifier">BOOST_THREAD_DCL_MOVABLE_BEG</span><span class="special">(</span><span class="identifier">T1</span><span class="special">)</span></code> and |
| <code class="computeroutput"><span class="identifier">BOOST_THREAD_DCL_MOVABLE_END</span></code></a> |
| </h5></div></div></div> |
| <p> |
| As Boost.Move defines also the <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">move</span></code> |
| function we need to specialize the <code class="computeroutput"><span class="identifier">has_move_emulation_enabled_aux</span></code> |
| metafunction. |
| </p> |
| <pre class="programlisting"><span class="keyword">template</span> <span class="special"><></span> |
| <span class="keyword">struct</span> <span class="identifier">has_move_emulation_enabled_aux</span><span class="special"><</span><span class="identifier">thread</span><span class="special">></span> |
| <span class="special">:</span> <span class="identifier">BOOST_MOVE_BOOST_NS</span><span class="special">::</span><span class="identifier">integral_constant</span><span class="special"><</span><span class="keyword">bool</span><span class="special">,</span> <span class="keyword">true</span><span class="special">></span> |
| <span class="special">{};</span> |
| </pre> |
| <p> |
| so that the following Boost.Move overload is disabled |
| </p> |
| <pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">></span> |
| <span class="keyword">inline</span> <span class="keyword">typename</span> <span class="identifier">BOOST_MOVE_BOOST_NS</span><span class="special">::</span><span class="identifier">disable_if</span><span class="special"><</span><span class="identifier">has_move_emulation_enabled_aux</span><span class="special"><</span><span class="identifier">T</span><span class="special">>,</span> <span class="identifier">T</span><span class="special">&>::</span><span class="identifier">type</span> <span class="identifier">move</span><span class="special">(</span><span class="identifier">T</span><span class="special">&</span> <span class="identifier">x</span><span class="special">);</span> |
| </pre> |
| <p> |
| The macros <code class="computeroutput"><span class="identifier">BOOST_THREAD_DCL_MOVABLE</span><span class="special">(</span><span class="identifier">CLASS</span><span class="special">)</span></code>, <code class="computeroutput"><span class="identifier">BOOST_THREAD_DCL_MOVABLE_BEG</span><span class="special">(</span><span class="identifier">T1</span><span class="special">)</span></code> and <code class="computeroutput"><span class="identifier">BOOST_THREAD_DCL_MOVABLE_END</span></code> |
| are used for this purpose. E.g. |
| </p> |
| <pre class="programlisting"><span class="identifier">BOOST_THREAD_DCL_MOVABLE</span><span class="special">(</span><span class="identifier">thread</span><span class="special">)</span> |
| </pre> |
| <p> |
| and |
| </p> |
| <pre class="programlisting"><span class="identifier">BOOST_THREAD_DCL_MOVABLE_BEG</span><span class="special">(</span><span class="identifier">T</span><span class="special">)</span> <span class="identifier">promise</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">BOOST_THREAD_DCL_MOVABLE_END</span> |
| </pre> |
| </div> |
| </div> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="thread.emulations.bool_explicit_conversion"></a><a class="link" href="emulations.html#thread.emulations.bool_explicit_conversion" title="Bool explicit conversion">Bool explicit |
| conversion</a> |
| </h3></div></div></div> |
| <div class="toc"><dl class="toc"> |
| <dt><span class="section"><a href="emulations.html#thread.emulations.bool_explicit_conversion.bool_conversion"><code class="computeroutput"><span class="keyword">operator</span> </code><span class="emphasis"><em>unspecified-bool-type</em></span><code class="computeroutput"><span class="special">()</span> <span class="keyword">const</span></code></a></span></dt> |
| <dt><span class="section"><a href="emulations.html#thread.emulations.bool_explicit_conversion.operator_not"><code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">!()</span> <span class="keyword">const</span></code></a></span></dt> |
| </dl></div> |
| <p> |
| Locks provide an explicit bool conversion operator when the compiler provides |
| them. |
| </p> |
| <pre class="programlisting"><span class="keyword">explicit</span> <span class="keyword">operator</span> <span class="keyword">bool</span><span class="special">()</span> <span class="keyword">const</span><span class="special">;</span> |
| </pre> |
| <p> |
| The library provides un implicit conversion to an undefined type that can |
| be used as a conditional expression. |
| </p> |
| <pre class="programlisting"><span class="preprocessor">#if</span> <span class="identifier">defined</span><span class="special">(</span><span class="identifier">BOOST_NO_EXPLICIT_CONVERSION_OPERATORS</span><span class="special">)</span> |
| <span class="keyword">operator</span> <span class="emphasis"><em>unspecified-bool-type</em></span><span class="special">()</span> <span class="keyword">const</span><span class="special">;</span> |
| <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">!()</span> <span class="keyword">const</span><span class="special">;</span> |
| <span class="preprocessor">#else</span> |
| <span class="keyword">explicit</span> <span class="keyword">operator</span> <span class="keyword">bool</span><span class="special">()</span> <span class="keyword">const</span><span class="special">;</span> |
| <span class="preprocessor">#endif</span> |
| </pre> |
| <p> |
| The user should use the lock.owns_lock() when a explicit conversion is required. |
| </p> |
| <div class="section"> |
| <div class="titlepage"><div><div><h4 class="title"> |
| <a name="thread.emulations.bool_explicit_conversion.bool_conversion"></a><a class="link" href="emulations.html#thread.emulations.bool_explicit_conversion.bool_conversion" title="operator unspecified-bool-type() const"><code class="computeroutput"><span class="keyword">operator</span> </code><span class="emphasis"><em>unspecified-bool-type</em></span><code class="computeroutput"><span class="special">()</span> <span class="keyword">const</span></code></a> |
| </h4></div></div></div> |
| <div class="variablelist"> |
| <p class="title"><b></b></p> |
| <dl class="variablelist"> |
| <dt><span class="term">Returns:</span></dt> |
| <dd><p> |
| If <a class="link" href="synchronization.html#thread.synchronization.locks.unique_lock.owns_lock" title="bool owns_lock() const"><code class="computeroutput"><span class="identifier">owns_lock</span><span class="special">()</span></code></a> |
| would return <code class="computeroutput"><span class="keyword">true</span></code>, a |
| value that evaluates to <code class="computeroutput"><span class="keyword">true</span></code> |
| in boolean contexts, otherwise a value that evaluates to <code class="computeroutput"><span class="keyword">false</span></code> in boolean contexts. |
| </p></dd> |
| <dt><span class="term">Throws:</span></dt> |
| <dd><p> |
| Nothing. |
| </p></dd> |
| </dl> |
| </div> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h4 class="title"> |
| <a name="thread.emulations.bool_explicit_conversion.operator_not"></a><a class="link" href="emulations.html#thread.emulations.bool_explicit_conversion.operator_not" title="bool operator!() const"><code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">!()</span> <span class="keyword">const</span></code></a> |
| </h4></div></div></div> |
| <div class="variablelist"> |
| <p class="title"><b></b></p> |
| <dl class="variablelist"> |
| <dt><span class="term">Returns:</span></dt> |
| <dd><p> |
| <code class="computeroutput"><span class="special">!</span></code> <a class="link" href="synchronization.html#thread.synchronization.locks.unique_lock.owns_lock" title="bool owns_lock() const"><code class="computeroutput"><span class="identifier">owns_lock</span><span class="special">()</span></code></a>. |
| </p></dd> |
| <dt><span class="term">Throws:</span></dt> |
| <dd><p> |
| Nothing. |
| </p></dd> |
| </dl> |
| </div> |
| </div> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="thread.emulations.scoped_enums"></a><a class="link" href="emulations.html#thread.emulations.scoped_enums" title="Scoped Enums">Scoped Enums</a> |
| </h3></div></div></div> |
| <p> |
| Some of the enumerations defined in the standard library are scoped enums. |
| </p> |
| <p> |
| On compilers that don't support them, the library uses a class to wrap the |
| underlying type. Instead of |
| </p> |
| <pre class="programlisting"><span class="keyword">enum</span> <span class="keyword">class</span> <span class="identifier">future_errc</span> |
| <span class="special">{</span> |
| <span class="identifier">broken_promise</span><span class="special">,</span> |
| <span class="identifier">future_already_retrieved</span><span class="special">,</span> |
| <span class="identifier">promise_already_satisfied</span><span class="special">,</span> |
| <span class="identifier">no_state</span> |
| <span class="special">};</span> |
| </pre> |
| <p> |
| the library declare these types as |
| </p> |
| <pre class="programlisting"><span class="identifier">BOOST_SCOPED_ENUM_DECLARE_BEGIN</span><span class="special">(</span><span class="identifier">future_errc</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="identifier">broken_promise</span><span class="special">,</span> |
| <span class="identifier">future_already_retrieved</span><span class="special">,</span> |
| <span class="identifier">promise_already_satisfied</span><span class="special">,</span> |
| <span class="identifier">no_state</span> |
| <span class="special">}</span> |
| <span class="identifier">BOOST_SCOPED_ENUM_DECLARE_END</span><span class="special">(</span><span class="identifier">future_errc</span><span class="special">)</span> |
| </pre> |
| <p> |
| These macros allows to use 'future_errc' in almost all the cases as an scoped |
| enum. |
| </p> |
| <p> |
| There are however some limitations: |
| </p> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| The type is not a C++ enum, so 'is_enum<future_errc>' will be false_type. |
| </li> |
| <li class="listitem"> |
| The emulated scoped enum can not be used in switch nor in template arguments. |
| For these cases the user needs to use some macros. |
| </li> |
| </ul></div> |
| <p> |
| Instead of |
| </p> |
| <pre class="programlisting"> <span class="keyword">switch</span> <span class="special">(</span><span class="identifier">ev</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="keyword">case</span> <span class="identifier">future_errc</span><span class="special">::</span><span class="identifier">broken_promise</span><span class="special">:</span> |
| <span class="comment">// ...</span> |
| </pre> |
| <p> |
| use |
| </p> |
| <pre class="programlisting"><span class="keyword">switch</span> <span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">native_value</span><span class="special">(</span><span class="identifier">ev</span><span class="special">))</span> |
| <span class="special">{</span> |
| <span class="keyword">case</span> <span class="identifier">future_errc</span><span class="special">::</span><span class="identifier">broken_promise</span><span class="special">:</span> |
| </pre> |
| <p> |
| And instead of |
| </p> |
| <pre class="programlisting"><span class="preprocessor">#ifdef</span> <span class="identifier">BOOST_NO_SCOPED_ENUMS</span> |
| <span class="keyword">template</span> <span class="special"><></span> |
| <span class="keyword">struct</span> <span class="identifier">BOOST_SYMBOL_VISIBLE</span> <span class="identifier">is_error_code_enum</span><span class="special"><</span><span class="identifier">future_errc</span><span class="special">></span> <span class="special">:</span> <span class="keyword">public</span> <span class="identifier">true_type</span> <span class="special">{</span> <span class="special">};</span> |
| <span class="preprocessor">#endif</span> |
| </pre> |
| <p> |
| use |
| </p> |
| <pre class="programlisting"><span class="preprocessor">#ifdef</span> <span class="identifier">BOOST_NO_SCOPED_ENUMS</span> |
| <span class="keyword">template</span> <span class="special"><></span> |
| <span class="keyword">struct</span> <span class="identifier">BOOST_SYMBOL_VISIBLE</span> <span class="identifier">is_error_code_enum</span><span class="special"><</span><span class="identifier">future_errc</span><span class="special">::</span><span class="identifier">enum_type</span><span class="special">></span> <span class="special">:</span> <span class="keyword">public</span> <span class="identifier">true_type</span> <span class="special">{</span> <span class="special">};</span> |
| <span class="preprocessor">#endif</span> |
| </pre> |
| </div> |
| </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 © 2007 -11 Anthony Williams<br>Copyright © 2011 -15 Vicente J. Botet Escriba<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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