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| <div class="titlepage"><div><div><h2 class="title" style="clear: both"> |
| <a name="boost_typetraits.intrinsics"></a><a class="link" href="intrinsics.html" title="Support for Compiler Intrinsics"> Support for Compiler Intrinsics</a> |
| </h2></div></div></div> |
| <p> |
| There are some traits that can not be implemented within the current C++ language: |
| to make these traits "just work" with user defined types, some kind |
| of additional help from the compiler is required. Currently (April 2008) Visual |
| C++ 8 and 9, GNU GCC 4.3 and MWCW 9 provide the necessary intrinsics, and other |
| compilers will no doubt follow in due course. |
| </p> |
| <p> |
| The Following traits classes always need compiler support to do the right thing |
| for all types (but all have safe fallback positions if this support is unavailable): |
| </p> |
| <div class="itemizedlist"><ul type="disc"> |
| <li> |
| <a class="link" href="reference/is_union.html" title="is_union">is_union</a> |
| </li> |
| <li> |
| <a class="link" href="reference/is_pod.html" title="is_pod">is_pod</a> |
| </li> |
| <li> |
| <a class="link" href="reference/has_trivial_constructor.html" title="has_trivial_constructor">has_trivial_constructor</a> |
| </li> |
| <li> |
| <a class="link" href="reference/has_trivial_copy.html" title="has_trivial_copy">has_trivial_copy</a> |
| </li> |
| <li> |
| <a class="link" href="reference/has_trivial_assign.html" title="has_trivial_assign">has_trivial_assign</a> |
| </li> |
| <li> |
| <a class="link" href="reference/has_trivial_destructor.html" title="has_trivial_destructor">has_trivial_destructor</a> |
| </li> |
| <li> |
| <a class="link" href="reference/has_nothrow_constructor.html" title="has_nothrow_constructor">has_nothrow_constructor</a> |
| </li> |
| <li> |
| <a class="link" href="reference/has_nothrow_copy.html" title="has_nothrow_copy">has_nothrow_copy</a> |
| </li> |
| <li> |
| <a class="link" href="reference/has_nothrow_assign.html" title="has_nothrow_assign">has_nothrow_assign</a> |
| </li> |
| <li> |
| <a class="link" href="reference/has_virtual_destructor.html" title="has_virtual_destructor">has_virtual_destructor</a> |
| </li> |
| </ul></div> |
| <p> |
| The following traits classes can't be portably implemented in the C++ language, |
| although in practice, the implementations do in fact do the right thing on |
| all the compilers we know about: |
| </p> |
| <div class="itemizedlist"><ul type="disc"> |
| <li> |
| <a class="link" href="reference/is_empty.html" title="is_empty">is_empty</a> |
| </li> |
| <li> |
| <a class="link" href="reference/is_polymorphic.html" title="is_polymorphic">is_polymorphic</a> |
| </li> |
| </ul></div> |
| <p> |
| The following traits classes are dependent on one or more of the above: |
| </p> |
| <div class="itemizedlist"><ul type="disc"> |
| <li> |
| <a class="link" href="reference/is_class.html" title="is_class">is_class</a> |
| </li> |
| <li> |
| <a class="link" href="reference/is_stateless.html" title="is_stateless">is_stateless</a> |
| </li> |
| </ul></div> |
| <p> |
| The hooks for compiler-intrinsic support are defined in <a href="../../../../../boost/type_traits/intrinsics.hpp" target="_top">boost/type_traits/intrinsics.hpp</a>, |
| adding support for new compilers is simply a matter of defining one of more |
| of the following macros: |
| </p> |
| <div class="table"> |
| <a name="id1043954"></a><p class="title"><b>Table 1.4. Macros for Compiler Intrinsics</b></p> |
| <div class="table-contents"><table class="table" summary="Macros for Compiler Intrinsics"> |
| <colgroup> |
| <col> |
| <col> |
| </colgroup> |
| <thead><tr> |
| <th> |
| <p> |
| BOOST_IS_UNION(T) |
| </p> |
| </th> |
| <th> |
| <p> |
| Should evaluate to true if T is a union type |
| </p> |
| </th> |
| </tr></thead> |
| <tbody> |
| <tr> |
| <td> |
| <p> |
| BOOST_IS_POD(T) |
| </p> |
| </td> |
| <td> |
| <p> |
| Should evaluate to true if T is a POD type |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| BOOST_IS_EMPTY(T) |
| </p> |
| </td> |
| <td> |
| <p> |
| Should evaluate to true if T is an empty struct or union |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| BOOST_HAS_TRIVIAL_CONSTRUCTOR(T) |
| </p> |
| </td> |
| <td> |
| <p> |
| Should evaluate to true if the default constructor for T is trivial |
| (i.e. has no effect) |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| BOOST_HAS_TRIVIAL_COPY(T) |
| </p> |
| </td> |
| <td> |
| <p> |
| Should evaluate to true if T has a trivial copy constructor (and |
| can therefore be replaced by a call to memcpy) |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| BOOST_HAS_TRIVIAL_ASSIGN(T) |
| </p> |
| </td> |
| <td> |
| <p> |
| Should evaluate to true if T has a trivial assignment operator (and |
| can therefore be replaced by a call to memcpy) |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| BOOST_HAS_TRIVIAL_DESTRUCTOR(T) |
| </p> |
| </td> |
| <td> |
| <p> |
| Should evaluate to true if T has a trivial destructor (i.e. ~T() |
| has no effect) |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| BOOST_HAS_NOTHROW_CONSTRUCTOR(T) |
| </p> |
| </td> |
| <td> |
| <p> |
| Should evaluate to true if <code class="computeroutput"><span class="identifier">T</span> |
| <span class="identifier">x</span><span class="special">;</span></code> |
| can not throw |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| BOOST_HAS_NOTHROW_COPY(T) |
| </p> |
| </td> |
| <td> |
| <p> |
| 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 |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| BOOST_HAS_NOTHROW_ASSIGN(T) |
| </p> |
| </td> |
| <td> |
| <p> |
| Should evaluate to true if <code class="computeroutput"><span class="identifier">T</span> |
| <span class="identifier">t</span><span class="special">,</span> |
| <span class="identifier">u</span><span class="special">;</span> |
| <span class="identifier">t</span> <span class="special">=</span> |
| <span class="identifier">u</span></code> can not throw |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| BOOST_HAS_VIRTUAL_DESTRUCTOR(T) |
| </p> |
| </td> |
| <td> |
| <p> |
| Should evaluate to true T has a virtual destructor |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| BOOST_IS_ABSTRACT(T) |
| </p> |
| </td> |
| <td> |
| <p> |
| Should evaluate to true if T is an abstract type |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| BOOST_IS_BASE_OF(T,U) |
| </p> |
| </td> |
| <td> |
| <p> |
| Should evaluate to true if T is a base class of U |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| BOOST_IS_CLASS(T) |
| </p> |
| </td> |
| <td> |
| <p> |
| Should evaluate to true if T is a class type |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| BOOST_IS_CONVERTIBLE(T,U) |
| </p> |
| </td> |
| <td> |
| <p> |
| Should evaluate to true if T is convertible to U |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| BOOST_IS_ENUM(T) |
| </p> |
| </td> |
| <td> |
| <p> |
| Should evaluate to true is T is an enum |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| BOOST_IS_POLYMORPHIC(T) |
| </p> |
| </td> |
| <td> |
| <p> |
| Should evaluate to true if T is a polymorphic type |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| BOOST_ALIGNMENT_OF(T) |
| </p> |
| </td> |
| <td> |
| <p> |
| Should evaluate to the alignment requirements of type T. |
| </p> |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| </div> |
| <br class="table-break"> |
| </div> |
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| <td align="left"></td> |
| <td align="right"><div class="copyright-footer">Copyright © 2000, 2006 Adobe Systems Inc, David Abrahams, |
| Steve Cleary, Beman Dawes, Aleksey Gurtovoy, Howard Hinnant, Jesse Jones, Mat |
| Marcus, Itay Maman, John Maddock, Alexander Nasonov, Thorsten Ottosen, Robert |
| Ramey and Jeremy Siek<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> |
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