1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>has_trivial_destructor</title> 5<link rel="stylesheet" href="../../../../../../doc/src/boostbook.css" type="text/css"> 6<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 7<link rel="home" href="../../index.html" title="Chapter 1. Boost.TypeTraits"> 8<link rel="up" href="../reference.html" title="Alphabetical Reference"> 9<link rel="prev" href="has_trivial_def_cons.html" title="has_trivial_default_constructor"> 10<link rel="next" href="has_trivial_move_assign.html" title="has_trivial_move_assign"> 11</head> 12<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 13<table cellpadding="2" width="100%"><tr> 14<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../boost.png"></td> 15<td align="center"><a href="../../../../../../index.html">Home</a></td> 16<td align="center"><a href="../../../../../../libs/libraries.htm">Libraries</a></td> 17<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> 18<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> 19<td align="center"><a href="../../../../../../more/index.htm">More</a></td> 20</tr></table> 21<hr> 22<div class="spirit-nav"> 23<a accesskey="p" href="has_trivial_def_cons.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../reference.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="has_trivial_move_assign.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="section"> 26<div class="titlepage"><div><div><h3 class="title"> 27<a name="boost_typetraits.reference.has_trivial_destructor"></a><a class="link" href="has_trivial_destructor.html" title="has_trivial_destructor">has_trivial_destructor</a> 28</h3></div></div></div> 29<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> 30<span class="keyword">struct</span> <span class="identifier">has_trivial_destructor</span> <span class="special">:</span> <span class="keyword">public</span> <em class="replaceable"><code><a class="link" href="integral_constant.html" title="integral_constant">true_type</a>-or-<a class="link" href="integral_constant.html" title="integral_constant">false_type</a></code></em> <span class="special">{};</span> 31</pre> 32<p> 33 <span class="bold"><strong>Inherits:</strong></span> If T is a (possibly cv-qualified) 34 type with a trivial destructor then inherits from <a class="link" href="integral_constant.html" title="integral_constant">true_type</a>, 35 otherwise inherits from <a class="link" href="integral_constant.html" title="integral_constant">false_type</a>. 36 </p> 37<p> 38 If a type has a trivial destructor then the destructor has no effect: calls 39 to the destructor can be safely omitted. Note that using meta-programming 40 to omit a call to a single trivial-constructor call is of no benefit whatsoever. 41 However, if loops and/or exception handling code can also be omitted, then 42 some benefit in terms of code size and speed can be obtained. 43 </p> 44<p> 45 <span class="bold"><strong>Compiler Compatibility:</strong></span> Without some (as 46 yet unspecified) help from the compiler, has_trivial_destructor will never 47 report that a user-defined class or struct has a trivial destructor; this 48 is always safe, if possibly sub-optimal. In addition, in order to correctly 49 handle deleted or private destructors then support for C++11's <code class="computeroutput"><span class="keyword">decltype</span></code> is required. Currently (June 2015) 50 compilers more recent than Visual C++ 8, GCC-4.3, Greenhills 6.0, Intel-11.0, 51 and Codegear have the necessary compiler <a class="link" href="../intrinsics.html" title="Support for Compiler Intrinsics">intrinsics</a> 52 to ensure that this trait "just works". You may also test to see 53 if the necessary <a class="link" href="../intrinsics.html" title="Support for Compiler Intrinsics">intrinsics</a> 54 are available by checking to see if the macro <code class="computeroutput"><span class="identifier">BOOST_HAS_TRIVIAL_DESTRUCTOR</span></code> 55 is defined. 56 </p> 57<p> 58 <span class="bold"><strong>C++ Standard Reference:</strong></span> 12.4p3. 59 </p> 60<p> 61 <span class="bold"><strong>Header:</strong></span> <code class="computeroutput"> <span class="preprocessor">#include</span> 62 <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">type_traits</span><span class="special">/</span><span class="identifier">has_trivial_destructor</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span></code> 63 or <code class="computeroutput"> <span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">type_traits</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span></code> 64 </p> 65<p> 66 <span class="bold"><strong>Examples:</strong></span> 67 </p> 68<div class="blockquote"><blockquote class="blockquote"><p> 69 <code class="computeroutput"><span class="identifier">has_trivial_destructor</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span></code> inherits from <code class="computeroutput"><a class="link" href="integral_constant.html" title="integral_constant">true_type</a></code>. 70 </p></blockquote></div> 71<div class="blockquote"><blockquote class="blockquote"><p> 72 <code class="computeroutput"><span class="identifier">has_trivial_destructor</span><span class="special"><</span><span class="keyword">char</span><span class="special">*>::</span><span class="identifier">type</span></code> 73 is the type <code class="computeroutput"><a class="link" href="integral_constant.html" title="integral_constant">true_type</a></code>. 74 </p></blockquote></div> 75<div class="blockquote"><blockquote class="blockquote"><p> 76 <code class="computeroutput"><span class="identifier">has_trivial_destructor</span><span class="special"><</span><span class="keyword">int</span> <span class="special">(*)(</span><span class="keyword">long</span><span class="special">)>::</span><span class="identifier">value</span></code> 77 is an integral constant expression that evaluates to <span class="emphasis"><em>true</em></span>. 78 </p></blockquote></div> 79<div class="blockquote"><blockquote class="blockquote"><p> 80 <code class="computeroutput"><span class="identifier">has_trivial_destructor</span><span class="special"><</span><span class="identifier">MyClass</span><span class="special">>::</span><span class="identifier">value</span></code> 81 is an integral constant expression that evaluates to <span class="emphasis"><em>false</em></span>. 82 </p></blockquote></div> 83<div class="blockquote"><blockquote class="blockquote"><p> 84 <code class="computeroutput"><span class="identifier">has_trivial_destructor</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value_type</span></code> 85 is the type <code class="computeroutput"><span class="keyword">bool</span></code>. 86 </p></blockquote></div> 87</div> 88<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 89<td align="left"></td> 90<td align="right"><div class="copyright-footer">Copyright © 2000, 2011 Adobe Systems Inc, David Abrahams, 91 Frederic Bron, Steve Cleary, Beman Dawes, Glen Fernandes, Aleksey Gurtovoy, 92 Howard Hinnant, Jesse Jones, Mat Marcus, Itay Maman, John Maddock, Alexander 93 Nasonov, Thorsten Ottosen, Roman Perepelitsa, Robert Ramey, Jeremy Siek, Robert 94 Stewart and Steven Watanabe<p> 95 Distributed under the Boost Software License, Version 1.0. (See accompanying 96 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>) 97 </p> 98</div></td> 99</tr></table> 100<hr> 101<div class="spirit-nav"> 102<a accesskey="p" href="has_trivial_def_cons.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../reference.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="has_trivial_move_assign.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a> 103</div> 104</body> 105</html> 106
