1<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> 2<html> 3<head> 4<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 5<title>Emulations</title> 6<link rel="stylesheet" href="../../../doc/src/boostbook.css" type="text/css"> 7<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 8<link rel="home" href="../index.html" title="The Boost C++ Libraries BoostBook Documentation Subset"> 9<link rel="up" href="../thread.html" title="Chapter 39. Thread 4.8.0"> 10<link rel="prev" href="time.html" title="Time Requirements"> 11<link rel="next" href="acknowledgements.html" title="Acknowledgments"> 12</head> 13<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 14<table cellpadding="2" width="100%"><tr> 15<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../boost.png"></td> 16<td align="center"><a href="../../../index.html">Home</a></td> 17<td align="center"><a href="../../../libs/libraries.htm">Libraries</a></td> 18<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> 19<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> 20<td align="center"><a href="../../../more/index.htm">More</a></td> 21</tr></table> 22<hr> 23<div class="spirit-nav"> 24<a accesskey="p" href="time.html"><img src="../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../thread.html"><img src="../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="acknowledgements.html"><img src="../../../doc/src/images/next.png" alt="Next"></a> 25</div> 26<div class="section"> 27<div class="titlepage"><div><div><h2 class="title" style="clear: both"> 28<a name="thread.emulations"></a><a class="link" href="emulations.html" title="Emulations">Emulations</a> 29</h2></div></div></div> 30<div class="toc"><dl class="toc"> 31<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> 32<dt><span class="section"><a href="emulations.html#thread.emulations.move">Move semantics</a></span></dt> 33<dt><span class="section"><a href="emulations.html#thread.emulations.bool_explicit_conversion">Bool explicit 34 conversion</a></span></dt> 35<dt><span class="section"><a href="emulations.html#thread.emulations.scoped_enums">Scoped Enums</a></span></dt> 36</dl></div> 37<div class="section"> 38<div class="titlepage"><div><div><h3 class="title"> 39<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> 40</h3></div></div></div> 41<p> 42 C++11 allows to delete some implicitly generated functions as constructors 43 and assignment using '= delete' as in 44 </p> 45<pre class="programlisting"><span class="keyword">public</span><span class="special">:</span> 46 <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> 47</pre> 48<p> 49 On compilers not supporting this feature, Boost.Thread relays on a partial 50 simulation, it declares the function as private without definition. 51 </p> 52<pre class="programlisting"><span class="keyword">private</span><span class="special">:</span> 53 <span class="identifier">thread</span><span class="special">(</span><span class="identifier">thread</span> <span class="special">&);</span> 54</pre> 55<p> 56 The emulation is partial as the private function can be used for overload 57 resolution for some compilers and prefer it to other overloads that need 58 a conversion. See below the consequences on the move semantic emulation. 59 </p> 60</div> 61<div class="section"> 62<div class="titlepage"><div><div><h3 class="title"> 63<a name="thread.emulations.move"></a><a class="link" href="emulations.html#thread.emulations.move" title="Move semantics">Move semantics</a> 64</h3></div></div></div> 65<div class="toc"><dl class="toc"> 66<dt><span class="section"><a href="emulations.html#thread.emulations.move.deprecated">Deprecated Version 67 2 interface</a></span></dt> 68<dt><span class="section"><a href="emulations.html#thread.emulations.move.portable">Portable interface</a></span></dt> 69</dl></div> 70<p> 71 In order to implement Movable classes, move parameters and return types Boost.Thread 72 uses the rvalue reference when the compiler support it. On compilers not 73 supporting it Boost.Thread uses either the emulation provided by Boost.Move 74 or the emulation provided by the previous versions of Boost.Thread depending 75 whether <code class="computeroutput"><span class="identifier">BOOST_THREAD_USES_MOVE</span></code> 76 is defined or not. This macros is unset by default when <code class="computeroutput"><span class="identifier">BOOST_THREAD_VERSION</span></code> 77 is 2. Since <code class="computeroutput"><span class="identifier">BOOST_THREAD_VERSION</span></code> 78 3, <code class="computeroutput"><span class="identifier">BOOST_THREAD_USES_MOVE</span></code> 79 is defined. 80 </p> 81<div class="section"> 82<div class="titlepage"><div><div><h4 class="title"> 83<a name="thread.emulations.move.deprecated"></a><a class="link" href="emulations.html#thread.emulations.move.deprecated" title="Deprecated Version 2 interface">Deprecated Version 84 2 interface</a> 85</h4></div></div></div> 86<div class="toc"><dl class="toc"> 87<dt><span class="section"><a href="emulations.html#thread.emulations.move.deprecated.Helper">Helpers 88 class and function</a></span></dt> 89<dt><span class="section"><a href="emulations.html#thread.emulations.move.deprecated.movable">Movable 90 emulation</a></span></dt> 91</dl></div> 92<p> 93 Previous to version 1.50, Boost.Thread make use of its own move semantic 94 emulation which had more limitations than the provided by Boost.Move. In 95 addition, it is of interest of the whole Boost community that Boost.Thread 96 uses Boost.Move so that boost::thread can be stored on Movable aware containers. 97 </p> 98<p> 99 To preserve backward compatibility at least during some releases, Boost.Thread 100 allows the user to use the deprecated move semantic emulation defining 101 BOOST_THREAD_DONT_USE_MOVE. 102 </p> 103<p> 104 Many aspects of move semantics can be emulated for compilers not supporting 105 rvalue references and Boost.Thread legacy offers tools for that purpose. 106 </p> 107<div class="section"> 108<div class="titlepage"><div><div><h5 class="title"> 109<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 110 class and function</a> 111</h5></div></div></div> 112<p> 113 Next follows the interface of the legacy move semantic helper class and 114 function. 115 </p> 116<pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span> 117<span class="special">{</span> 118 <span class="keyword">namespace</span> <span class="identifier">detail</span> 119 <span class="special">{</span> 120 <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> <span class="identifier">T</span><span class="special">></span> 121 <span class="keyword">struct</span> <span class="identifier">thread_move_t</span> 122 <span class="special">{</span> 123 <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> 124 <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> 125 <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> 126 <span class="keyword">private</span><span class="special">:</span> 127 <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> 128 <span class="special">};</span> 129 <span class="special">}</span> 130 <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> <span class="identifier">T</span><span class="special">></span> 131 <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> 132<span class="special">}</span> 133</pre> 134</div> 135<div class="section"> 136<div class="titlepage"><div><div><h5 class="title"> 137<a name="thread.emulations.move.deprecated.movable"></a><a class="link" href="emulations.html#thread.emulations.move.deprecated.movable" title="Movable emulation">Movable 138 emulation</a> 139</h5></div></div></div> 140<p> 141 We can write a MovableOny class as follows. You just need to follow these 142 simple steps: 143 </p> 144<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 145<li class="listitem"> 146 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> 147 </li> 148<li class="listitem"> 149 Make the copy constructor private. 150 </li> 151<li class="listitem"> 152 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> 153 </li> 154<li class="listitem"> 155 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> 156 </li> 157</ul></div> 158<p> 159 For example the thread class defines the following: 160 </p> 161<pre class="programlisting"><span class="keyword">class</span> <span class="identifier">thread</span> 162<span class="special">{</span> 163 <span class="comment">// ...</span> 164<span class="keyword">private</span><span class="special">:</span> 165 <span class="identifier">thread</span><span class="special">(</span><span class="identifier">thread</span><span class="special">&);</span> 166 <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> 167<span class="keyword">public</span><span class="special">:</span> 168 <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> 169 <span class="special">{</span> 170 <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> 171 <span class="keyword">return</span> <span class="identifier">x</span><span class="special">;</span> 172 <span class="special">}</span> 173 <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> 174 <span class="special">{</span> 175 <span class="keyword">return</span> <span class="identifier">move</span><span class="special">();</span> 176 <span class="special">}</span> 177 <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> 178 <span class="special">{</span> 179 <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> 180 <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> 181 <span class="special">}</span> 182 <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> 183 <span class="special">{</span> 184 <span class="identifier">thread</span> <span class="identifier">new_thread</span><span class="special">(</span><span class="identifier">x</span><span class="special">);</span> 185 <span class="identifier">swap</span><span class="special">(</span><span class="identifier">new_thread</span><span class="special">);</span> 186 <span class="keyword">return</span> <span class="special">*</span><span class="keyword">this</span><span class="special">;</span> 187 <span class="special">}</span> 188 <span class="comment">// ...</span> 189 190<span class="special">};</span> 191</pre> 192</div> 193</div> 194<div class="section"> 195<div class="titlepage"><div><div><h4 class="title"> 196<a name="thread.emulations.move.portable"></a><a class="link" href="emulations.html#thread.emulations.move.portable" title="Portable interface">Portable interface</a> 197</h4></div></div></div> 198<div class="toc"><dl class="toc"> 199<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> 200<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> 201<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> 202<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> 203<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>, 204 <code class="computeroutput"><span class="identifier">BOOST_THREAD_RV_REF_BEG</span></code> 205 and <code class="computeroutput"><span class="identifier">BOOST_THREAD_RV_REF_END</span></code></a></span></dt> 206<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> 207<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> 208<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 209 <code class="computeroutput"><span class="identifier">BOOST_THREAD_DCL_MOVABLE_END</span></code></a></span></dt> 210</dl></div> 211<p> 212 In order to make the library code portable Boost.Thread uses some macros 213 that will use either the ones provided by Boost.Move or the deprecated 214 move semantics provided by previous versions of Boost.Thread. 215 </p> 216<p> 217 See the Boost.Move documentation for a complete description on how to declare 218 new Movable classes and its limitations. 219 </p> 220<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 221<li class="listitem"> 222 <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> 223 </li> 224<li class="listitem"> 225 <code class="computeroutput"><span class="identifier">BOOST_THREAD_RV_REF_BEG</span></code> 226 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> 227 </li> 228<li class="listitem"> 229 <code class="computeroutput"><span class="identifier">BOOST_THREAD_RV_REF_END</span></code> 230 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> 231 </li> 232<li class="listitem"> 233 <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) 234 </li> 235</ul></div> 236<p> 237 In addition the following macros are needed to make the code portable: 238 </p> 239<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 240<li class="listitem"> 241 <code class="computeroutput"><span class="identifier">BOOST_THREAD_RV</span><span class="special">(</span><span class="identifier">V</span><span class="special">)</span></code> 242 macro to access the rvalue from a BOOST_THREAD_RV_REF(TYPE), 243 </li> 244<li class="listitem"> 245 <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. 246 </li> 247<li class="listitem"> 248 <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 249 </li> 250<li class="listitem"> 251 <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> 252 are variant of <code class="computeroutput"><span class="identifier">BOOST_THREAD_DCL_MOVABLE</span></code> 253 when the parameter is a template instantiation. 254 </li> 255</ul></div> 256<p> 257 Other macros are provided and must be included on the public section: 258 </p> 259<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 260<li class="listitem"> 261 <code class="computeroutput"><span class="identifier">BOOST_THREAD_NO_COPYABLE</span></code> 262 declares a class no-copyable either deleting the copy constructors 263 and copy assignment or moving them to the private section. 264 </li> 265<li class="listitem"> 266 <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 267 to an rvalue-reference. 268 </li> 269<li class="listitem"> 270 <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> 271 </li> 272<li class="listitem"> 273 <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> 274 </li> 275</ul></div> 276<div class="section"> 277<div class="titlepage"><div><div><h5 class="title"> 278<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> 279</h5></div></div></div> 280<p> 281 This macro marks a class as no copyable, disabling copy construction 282 and assignment. 283 </p> 284</div> 285<div class="section"> 286<div class="titlepage"><div><div><h5 class="title"> 287<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> 288</h5></div></div></div> 289<p> 290 This macro marks a class as movable, declaring all the implicit conversions 291 to an rvalue-reference. 292 </p> 293</div> 294<div class="section"> 295<div class="titlepage"><div><div><h5 class="title"> 296<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> 297</h5></div></div></div> 298<p> 299 This macro marks a type as movable but not copyable, disabling copy construction 300 and assignment. The user will need to write a move constructor/assignment 301 to fully write a movable but not copyable class. 302 </p> 303</div> 304<div class="section"> 305<div class="titlepage"><div><div><h5 class="title"> 306<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> 307</h5></div></div></div> 308<p> 309 This macro marks a type as copyable and movable. The user will need to 310 write a move constructor/assignment and a copy assignment to fully write 311 a copyable and movable class. 312 </p> 313</div> 314<div class="section"> 315<div class="titlepage"><div><div><h5 class="title"> 316<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>, 317 <code class="computeroutput"><span class="identifier">BOOST_THREAD_RV_REF_BEG</span></code> 318 and <code class="computeroutput"><span class="identifier">BOOST_THREAD_RV_REF_END</span></code></a> 319</h5></div></div></div> 320<p> 321 This macro is used to achieve portable syntax in move constructors and 322 assignments for classes marked as <code class="computeroutput"><span class="identifier">BOOST_THREAD_COPYABLE_AND_MOVABLE</span></code> 323 or <code class="computeroutput"><span class="identifier">BOOST_THREAD_MOVABLE_ONLY</span></code>. 324 </p> 325<p> 326 <code class="computeroutput"><span class="identifier">BOOST_THREAD_RV_REF_BEG</span></code> 327 and <code class="computeroutput"><span class="identifier">BOOST_THREAD_RV_REF_END</span></code> 328 are used when the parameter end with a <code class="computeroutput"><span class="special">></span></code> 329 to avoid the compiler error. 330 </p> 331</div> 332<div class="section"> 333<div class="titlepage"><div><div><h5 class="title"> 334<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> 335</h5></div></div></div> 336<p> 337 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> 338 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. 339 E.g. 340 </p> 341<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> 342<span class="special">{</span> 343 <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> 344 <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> 345<span class="special">}</span> 346</pre> 347<p> 348 The use of this macros has reduced considerably the size of the Boost.Thread 349 move related code. 350 </p> 351</div> 352<div class="section"> 353<div class="titlepage"><div><div><h5 class="title"> 354<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> 355</h5></div></div></div> 356<p> 357 While Boost.Move is the best C++03 move emulation there are some limitations 358 that impact the way the library can be used. For example, with the following 359 declarations 360 </p> 361<pre class="programlisting"><span class="keyword">class</span> <span class="identifier">thread</span> <span class="special">{</span> 362 <span class="comment">// ...</span> 363<span class="keyword">private</span><span class="special">:</span> 364 <span class="identifier">thread</span><span class="special">(</span><span class="identifier">thread</span> <span class="special">&);</span> 365<span class="keyword">public</span><span class="special">:</span> 366 <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> 367 <span class="comment">// ...</span> 368<span class="special">};</span> 369</pre> 370<p> 371 This could not work on some compilers even if thread is convertible to 372 <code class="computeroutput"><span class="identifier">rv</span><span class="special"><</span><span class="identifier">thread</span><span class="special">></span></code> 373 because the compiler prefers the private copy constructor. 374 </p> 375<pre class="programlisting"><span class="identifier">thread</span> <span class="identifier">mkth</span><span class="special">()</span> 376<span class="special">{</span> 377 <span class="keyword">return</span> <span class="identifier">thread</span><span class="special">(</span><span class="identifier">f</span><span class="special">);</span> 378<span class="special">}</span> 379</pre> 380<p> 381 On these compilers we need to use instead an explicit conversion. The 382 library provides a move member function that allows to workaround the 383 issue. 384 </p> 385<pre class="programlisting"><span class="identifier">thread</span> <span class="identifier">mkth</span><span class="special">()</span> 386<span class="special">{</span> 387 <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> 388<span class="special">}</span> 389</pre> 390<p> 391 Note that <code class="computeroutput"><span class="special">::</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">move</span></code> 392 can not be used in this case as thread is not implicitly convertible 393 to <code class="computeroutput"><span class="identifier">thread</span><span class="special">&</span></code>. 394 </p> 395<pre class="programlisting"><span class="identifier">thread</span> <span class="identifier">mkth</span><span class="special">()</span> 396<span class="special">{</span> 397 <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> 398<span class="special">}</span> 399</pre> 400<p> 401 To make the code portable Boost.Thread the user needs to use a macro 402 <code class="computeroutput"><span class="identifier">BOOST_THREAD_MAKE_RV_REF</span></code> 403 that can be used as in 404 </p> 405<pre class="programlisting"><span class="identifier">thread</span> <span class="identifier">mkth</span><span class="special">()</span> 406<span class="special">{</span> 407 <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> 408<span class="special">}</span> 409</pre> 410<p> 411 Note that this limitation is shared also by the legacy Boost.Thread move 412 emulation. 413 </p> 414</div> 415<div class="section"> 416<div class="titlepage"><div><div><h5 class="title"> 417<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 418 <code class="computeroutput"><span class="identifier">BOOST_THREAD_DCL_MOVABLE_END</span></code></a> 419</h5></div></div></div> 420<p> 421 As Boost.Move defines also the <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">move</span></code> 422 function we need to specialize the <code class="computeroutput"><span class="identifier">has_move_emulation_enabled_aux</span></code> 423 metafunction. 424 </p> 425<pre class="programlisting"><span class="keyword">template</span> <span class="special"><></span> 426<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> 427 <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> 428<span class="special">{};</span> 429</pre> 430<p> 431 so that the following Boost.Move overload is disabled 432 </p> 433<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> 434<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> 435</pre> 436<p> 437 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> 438 are used for this purpose. E.g. 439 </p> 440<pre class="programlisting"><span class="identifier">BOOST_THREAD_DCL_MOVABLE</span><span class="special">(</span><span class="identifier">thread</span><span class="special">)</span> 441</pre> 442<p> 443 and 444 </p> 445<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> 446</pre> 447</div> 448</div> 449</div> 450<div class="section"> 451<div class="titlepage"><div><div><h3 class="title"> 452<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 453 conversion</a> 454</h3></div></div></div> 455<div class="toc"><dl class="toc"> 456<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> 457<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> 458</dl></div> 459<p> 460 Locks provide an explicit bool conversion operator when the compiler provides 461 them. 462 </p> 463<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> 464</pre> 465<p> 466 The library provides un implicit conversion to an undefined type that can 467 be used as a conditional expression. 468 </p> 469<pre class="programlisting"><span class="preprocessor">#if</span> <span class="identifier">defined</span><span class="special">(</span><span class="identifier">BOOST_NO_CXX11_EXPLICIT_CONVERSION_OPERATORS</span><span class="special">)</span> 470 <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> 471 <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">!()</span> <span class="keyword">const</span><span class="special">;</span> 472<span class="preprocessor">#else</span> 473 <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> 474<span class="preprocessor">#endif</span> 475</pre> 476<p> 477 The user should use the lock.owns_lock() when an explicit conversion is required. 478 </p> 479<div class="section"> 480<div class="titlepage"><div><div><h4 class="title"> 481<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> 482</h4></div></div></div> 483<div class="variablelist"> 484<p class="title"><b></b></p> 485<dl class="variablelist"> 486<dt><span class="term">Returns:</span></dt> 487<dd><p> 488 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> 489 would return <code class="computeroutput"><span class="keyword">true</span></code>, a 490 value that evaluates to <code class="computeroutput"><span class="keyword">true</span></code> 491 in boolean contexts, otherwise a value that evaluates to <code class="computeroutput"><span class="keyword">false</span></code> in boolean contexts. 492 </p></dd> 493<dt><span class="term">Throws:</span></dt> 494<dd><p> 495 Nothing. 496 </p></dd> 497</dl> 498</div> 499</div> 500<div class="section"> 501<div class="titlepage"><div><div><h4 class="title"> 502<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> 503</h4></div></div></div> 504<div class="variablelist"> 505<p class="title"><b></b></p> 506<dl class="variablelist"> 507<dt><span class="term">Returns:</span></dt> 508<dd><p> 509 <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>. 510 </p></dd> 511<dt><span class="term">Throws:</span></dt> 512<dd><p> 513 Nothing. 514 </p></dd> 515</dl> 516</div> 517</div> 518</div> 519<div class="section"> 520<div class="titlepage"><div><div><h3 class="title"> 521<a name="thread.emulations.scoped_enums"></a><a class="link" href="emulations.html#thread.emulations.scoped_enums" title="Scoped Enums">Scoped Enums</a> 522</h3></div></div></div> 523<p> 524 Some of the enumerations defined in the standard library are scoped enums. 525 </p> 526<p> 527 On compilers that don't support them, the library uses a class to wrap the 528 underlying type. Instead of 529 </p> 530<pre class="programlisting"><span class="keyword">enum</span> <span class="keyword">class</span> <span class="identifier">future_errc</span> 531<span class="special">{</span> 532 <span class="identifier">broken_promise</span><span class="special">,</span> 533 <span class="identifier">future_already_retrieved</span><span class="special">,</span> 534 <span class="identifier">promise_already_satisfied</span><span class="special">,</span> 535 <span class="identifier">no_state</span> 536<span class="special">};</span> 537</pre> 538<p> 539 the library declare these types as 540 </p> 541<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> 542<span class="special">{</span> 543 <span class="identifier">broken_promise</span><span class="special">,</span> 544 <span class="identifier">future_already_retrieved</span><span class="special">,</span> 545 <span class="identifier">promise_already_satisfied</span><span class="special">,</span> 546 <span class="identifier">no_state</span> 547<span class="special">}</span> 548<span class="identifier">BOOST_SCOPED_ENUM_DECLARE_END</span><span class="special">(</span><span class="identifier">future_errc</span><span class="special">)</span> 549</pre> 550<p> 551 These macros allows to use 'future_errc' in almost all the cases as a scoped 552 enum. 553 </p> 554<p> 555 There are however some limitations: 556 </p> 557<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 558<li class="listitem"> 559 The type is not a C++ enum, so 'is_enum<future_errc>' will be false_type. 560 </li> 561<li class="listitem"> 562 The emulated scoped enum can not be used in switch nor in template arguments. 563 For these cases the user needs to use some macros. 564 </li> 565</ul></div> 566<p> 567 Instead of 568 </p> 569<pre class="programlisting"> <span class="keyword">switch</span> <span class="special">(</span><span class="identifier">ev</span><span class="special">)</span> 570 <span class="special">{</span> 571 <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> 572<span class="comment">// ...</span> 573</pre> 574<p> 575 use 576 </p> 577<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> 578<span class="special">{</span> 579<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> 580</pre> 581<p> 582 And instead of 583 </p> 584<pre class="programlisting"><span class="preprocessor">#ifdef</span> <span class="identifier">BOOST_NO_CXX11_SCOPED_ENUMS</span> 585<span class="keyword">template</span> <span class="special"><></span> 586<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> 587<span class="preprocessor">#endif</span> 588</pre> 589<p> 590 use 591 </p> 592<pre class="programlisting"><span class="preprocessor">#ifdef</span> <span class="identifier">BOOST_NO_CXX11_SCOPED_ENUMS</span> 593<span class="keyword">template</span> <span class="special"><></span> 594<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> 595<span class="preprocessor">#endif</span> 596</pre> 597</div> 598</div> 599<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 600<td align="left"></td> 601<td align="right"><div class="copyright-footer">Copyright © 2007 -11 Anthony Williams<br>Copyright © 2011 -17 Vicente J. Botet Escriba<p> 602 Distributed under the Boost Software License, Version 1.0. (See accompanying 603 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>) 604 </p> 605</div></td> 606</tr></table> 607<hr> 608<div class="spirit-nav"> 609<a accesskey="p" href="time.html"><img src="../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../thread.html"><img src="../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="acknowledgements.html"><img src="../../../doc/src/images/next.png" alt="Next"></a> 610</div> 611</body> 612</html> 613
