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  26 <div class="titlepage"><div><div><h2 class="title" style="clear: both">
  27 <a name="boost_typetraits.intrinsics"></a><a class="link" href="intrinsics.html" title="Support for Compiler Intrinsics">Support for Compiler Intrinsics</a>
  28 </h2></div></div></div>
  29 <p>
  30       There are some traits that can not be implemented within the current C++ language:
  31       to make these traits "just work" with user defined types, some kind
  32       of additional help from the compiler is required. Currently (April 2008) Visual
  33       C++ 8 and 9, GNU GCC 4.3 and MWCW 9 provide at least some of the the necessary
  34       intrinsics, and other compilers will no doubt follow in due course.
  35     </p>
  36 <p>
  37       The Following traits classes always need compiler support to do the right thing
  38       for all types (but all have safe fallback positions if this support is unavailable):
  39     </p>
  40 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
  41 <li class="listitem">
  42           <a class="link" href="reference/is_final.html" title="is_final">is_final</a>
  43         </li>
  44 <li class="listitem">
  45           <a class="link" href="reference/is_union.html" title="is_union">is_union</a>
  46         </li>
  47 <li class="listitem">
  48           <a class="link" href="reference/is_pod.html" title="is_pod">is_pod</a>
  49         </li>
  50 <li class="listitem">
  51           <a class="link" href="reference/is_nothrow_move_assignable.html" title="is_nothrow_move_assignable">is_nothrow_move_assignable</a>
  52         </li>
  53 <li class="listitem">
  54           <a class="link" href="reference/is_nothrow_move_constructible.html" title="is_nothrow_move_constructible">is_nothrow_move_constructible</a>
  55         </li>
  56 <li class="listitem">
  57           <a class="link" href="reference/has_trivial_constructor.html" title="has_trivial_constructor">has_trivial_constructor</a>
  58         </li>
  59 <li class="listitem">
  60           <a class="link" href="reference/has_trivial_copy.html" title="has_trivial_copy">has_trivial_copy</a>
  61         </li>
  62 <li class="listitem">
  63           <a class="link" href="reference/has_trivial_move_constructor.html" title="has_trivial_move_constructor">has_trivial_move_constructor</a>
  64         </li>
  65 <li class="listitem">
  66           <a class="link" href="reference/has_trivial_assign.html" title="has_trivial_assign">has_trivial_assign</a>
  67         </li>
  68 <li class="listitem">
  69           <a class="link" href="reference/has_trivial_move_assign.html" title="has_trivial_move_assign">has_trivial_move_assign</a>
  70         </li>
  71 <li class="listitem">
  72           <a class="link" href="reference/has_trivial_destructor.html" title="has_trivial_destructor">has_trivial_destructor</a>
  73         </li>
  74 <li class="listitem">
  75           <a class="link" href="reference/has_nothrow_constructor.html" title="has_nothrow_constructor">has_nothrow_constructor</a>
  76         </li>
  77 <li class="listitem">
  78           <a class="link" href="reference/has_nothrow_copy.html" title="has_nothrow_copy">has_nothrow_copy</a>
  79         </li>
  80 <li class="listitem">
  81           <a class="link" href="reference/has_nothrow_assign.html" title="has_nothrow_assign">has_nothrow_assign</a>
  82         </li>
  83 <li class="listitem">
  84           <a class="link" href="reference/has_virtual_destructor.html" title="has_virtual_destructor">has_virtual_destructor</a>
  85         </li>
  86 </ul></div>
  87 <p>
  88       The following traits classes can't be portably implemented in the C++ language,
  89       although in practice, the implementations do in fact do the right thing on
  90       all the compilers we know about:
  91     </p>
  92 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
  93 <li class="listitem">
  94           <a class="link" href="reference/is_empty.html" title="is_empty">is_empty</a>
  95         </li>
  96 <li class="listitem">
  97           <a class="link" href="reference/is_polymorphic.html" title="is_polymorphic">is_polymorphic</a>
  98         </li>
  99 <li class="listitem">
 100           <a class="link" href="reference/is_virtual_base_of.html" title="is_virtual_base_of">is_virtual_base_of</a>
 101         </li>
 102 </ul></div>
 103 <p>
 104       The following traits classes are dependent on one or more of the above:
 105     </p>
 106 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
 107 <li class="listitem">
 108           <a class="link" href="reference/is_class.html" title="is_class">is_class</a>
 109         </li>
 110 <li class="listitem">
 111           <a class="link" href="reference/is_stateless.html" title="is_stateless">is_stateless</a>
 112         </li>
 113 </ul></div>
 114 <p>
 115       The hooks for compiler-intrinsic support are defined in <a href="../../../../../boost/type_traits/intrinsics.hpp" target="_top">boost/type_traits/intrinsics.hpp</a>,
 116       adding support for new compilers is simply a matter of defining one of more
 117       of the following macros:
 118     </p>
 119 <div class="table">
 120 <a name="boost_typetraits.intrinsics.macros_for_compiler_intrinsics"></a><p class="title"><b>Table&#160;1.9.&#160;Macros for Compiler Intrinsics</b></p>
 121 <div class="table-contents"><table class="table" summary="Macros for Compiler Intrinsics">
 122 <colgroup>
 123 <col>
 124 <col>
 125 </colgroup>
 126 <thead><tr>
 127 <th>
 128               <p>
 129                 BOOST_ALIGNMENT_OF(T)
 130               </p>
 131             </th>
 132 <th>
 133               <p>
 134                 Should evaluate to the alignment requirements of type T
 135               </p>
 136             </th>
 137 </tr></thead>
 138 <tbody>
 139 <tr>
 140 <td>
 141               <p>
 142                 BOOST_IS_ABSTRACT(T)
 143               </p>
 144             </td>
 145 <td>
 146               <p>
 147                 Should evaluate to true if T is an abstract type
 148               </p>
 149             </td>
 150 </tr>
 151 <tr>
 152 <td>
 153               <p>
 154                 BOOST_IS_BASE_OF(T,U)
 155               </p>
 156             </td>
 157 <td>
 158               <p>
 159                 Should evaluate to true if T is a base class of U
 160               </p>
 161             </td>
 162 </tr>
 163 <tr>
 164 <td>
 165               <p>
 166                 BOOST_IS_CLASS(T)
 167               </p>
 168             </td>
 169 <td>
 170               <p>
 171                 Should evaluate to true if T is a class type
 172               </p>
 173             </td>
 174 </tr>
 175 <tr>
 176 <td>
 177               <p>
 178                 BOOST_IS_CONVERTIBLE(T,U)
 179               </p>
 180             </td>
 181 <td>
 182               <p>
 183                 Should evaluate to true if T is convertible to U
 184               </p>
 185             </td>
 186 </tr>
 187 <tr>
 188 <td>
 189               <p>
 190                 BOOST_IS_EMPTY(T)
 191               </p>
 192             </td>
 193 <td>
 194               <p>
 195                 Should evaluate to true if T is an empty struct or union
 196               </p>
 197             </td>
 198 </tr>
 199 <tr>
 200 <td>
 201               <p>
 202                 BOOST_IS_ENUM(T)
 203               </p>
 204             </td>
 205 <td>
 206               <p>
 207                 Should evaluate to true is T is an enum
 208               </p>
 209             </td>
 210 </tr>
 211 <tr>
 212 <td>
 213               <p>
 214                 BOOST_IS_FINAL(T)
 215               </p>
 216             </td>
 217 <td>
 218               <p>
 219                 Should evaluate to true if T is a class type declared with the final
 220                 specifier
 221               </p>
 222             </td>
 223 </tr>
 224 <tr>
 225 <td>
 226               <p>
 227                 BOOST_IS_NOTHROW_MOVE_ASSIGN(T)
 228               </p>
 229             </td>
 230 <td>
 231               <p>
 232                 Should evaluate to true T has a non-throwing move assign operator.
 233               </p>
 234             </td>
 235 </tr>
 236 <tr>
 237 <td>
 238               <p>
 239                 BOOST_IS_NOTHROW_MOVE_CONSTRUCT(T)
 240               </p>
 241             </td>
 242 <td>
 243               <p>
 244                 Should evaluate to true T has a non-throwing move constructor.
 245               </p>
 246             </td>
 247 </tr>
 248 <tr>
 249 <td>
 250               <p>
 251                 BOOST_IS_POLYMORPHIC(T)
 252               </p>
 253             </td>
 254 <td>
 255               <p>
 256                 Should evaluate to true if T is a polymorphic type
 257               </p>
 258             </td>
 259 </tr>
 260 <tr>
 261 <td>
 262               <p>
 263                 BOOST_IS_POD(T)
 264               </p>
 265             </td>
 266 <td>
 267               <p>
 268                 Should evaluate to true if T is a POD type
 269               </p>
 270             </td>
 271 </tr>
 272 <tr>
 273 <td>
 274               <p>
 275                 BOOST_IS_UNION(T)
 276               </p>
 277             </td>
 278 <td>
 279               <p>
 280                 Should evaluate to true if T is a union type
 281               </p>
 282             </td>
 283 </tr>
 284 <tr>
 285 <td>
 286               <p>
 287                 BOOST_HAS_NOTHROW_ASSIGN(T)
 288               </p>
 289             </td>
 290 <td>
 291               <p>
 292                 Should evaluate to true if <code class="computeroutput"><span class="identifier">T</span>
 293                 <span class="identifier">t</span><span class="special">,</span>
 294                 <span class="identifier">u</span><span class="special">;</span>
 295                 <span class="identifier">t</span> <span class="special">=</span>
 296                 <span class="identifier">u</span></code> can not throw
 297               </p>
 298             </td>
 299 </tr>
 300 <tr>
 301 <td>
 302               <p>
 303                 BOOST_HAS_NOTHROW_CONSTRUCTOR(T)
 304               </p>
 305             </td>
 306 <td>
 307               <p>
 308                 Should evaluate to true if <code class="computeroutput"><span class="identifier">T</span>
 309                 <span class="identifier">x</span><span class="special">;</span></code>
 310                 can not throw
 311               </p>
 312             </td>
 313 </tr>
 314 <tr>
 315 <td>
 316               <p>
 317                 BOOST_HAS_NOTHROW_COPY(T)
 318               </p>
 319             </td>
 320 <td>
 321               <p>
 322                 Should evaluate to true if <code class="computeroutput"><span class="identifier">T</span><span class="special">(</span><span class="identifier">t</span><span class="special">)</span></code> can not throw
 323               </p>
 324             </td>
 325 </tr>
 326 <tr>
 327 <td>
 328               <p>
 329                 BOOST_HAS_TRIVIAL_ASSIGN(T)
 330               </p>
 331             </td>
 332 <td>
 333               <p>
 334                 Should evaluate to true if T has a trivial assignment operator (and
 335                 can therefore be replaced by a call to memcpy)
 336               </p>
 337             </td>
 338 </tr>
 339 <tr>
 340 <td>
 341               <p>
 342                 BOOST_HAS_TRIVIAL_CONSTRUCTOR(T)
 343               </p>
 344             </td>
 345 <td>
 346               <p>
 347                 Should evaluate to true if the default constructor for T is trivial
 348                 (i.e. has no effect)
 349               </p>
 350             </td>
 351 </tr>
 352 <tr>
 353 <td>
 354               <p>
 355                 BOOST_HAS_TRIVIAL_COPY(T)
 356               </p>
 357             </td>
 358 <td>
 359               <p>
 360                 Should evaluate to true if T has a trivial copy constructor (and
 361                 can therefore be replaced by a call to memcpy)
 362               </p>
 363             </td>
 364 </tr>
 365 <tr>
 366 <td>
 367               <p>
 368                 BOOST_HAS_TRIVIAL_DESTRUCTOR(T)
 369               </p>
 370             </td>
 371 <td>
 372               <p>
 373                 Should evaluate to true if T has a trivial destructor (i.e. ~T()
 374                 has no effect)
 375               </p>
 376             </td>
 377 </tr>
 378 <tr>
 379 <td>
 380               <p>
 381                 BOOST_HAS_TRIVIAL_MOVE_CONSTRUCTOR(T)
 382               </p>
 383             </td>
 384 <td>
 385               <p>
 386                 Should evaluate to true if T has a trivial move constructor (and
 387                 can therefore be replaced by a call to memcpy)
 388               </p>
 389             </td>
 390 </tr>
 391 <tr>
 392 <td>
 393               <p>
 394                 BOOST_HAS_TRIVIAL_MOVE_ASSIGN(T)
 395               </p>
 396             </td>
 397 <td>
 398               <p>
 399                 Should evaluate to true if T has a trivial move assignment operator
 400                 (and can therefore be replaced by a call to memcpy)
 401               </p>
 402             </td>
 403 </tr>
 404 <tr>
 405 <td>
 406               <p>
 407                 BOOST_HAS_VIRTUAL_DESTRUCTOR(T)
 408               </p>
 409             </td>
 410 <td>
 411               <p>
 412                 Should evaluate to true T has a virtual destructor
 413               </p>
 414             </td>
 415 </tr>
 416 </tbody>
 417 </table></div>
 418 </div>
 419 <br class="table-break">
 420 </div>
 421 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 422 <td align="left"></td>
 423 <td align="right"><div class="copyright-footer">Copyright &#169; 2000, 2011 Adobe Systems Inc, David Abrahams,
 424       Frederic Bron, Steve Cleary, Beman Dawes, Aleksey Gurtovoy, Howard Hinnant,
 425       Jesse Jones, Mat Marcus, Itay Maman, John Maddock, Alexander Nasonov, Thorsten
 426       Ottosen, Roman Perepelitsa, Robert Ramey, Jeremy Siek, Robert Stewart and Steven
 427       Watanabe<p>
 428         Distributed under the Boost Software License, Version 1.0. (See accompanying
 429         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>)
 430       </p>
 431 </div></td>
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