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>Safe hooks</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="../intrusive.html" title="Chapter 19. Boost.Intrusive"> 10<link rel="prev" href="presenting_containers.html" title="Presenting Boost.Intrusive containers"> 11<link rel="next" href="auto_unlink_hooks.html" title="Auto-unlink hooks"> 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="presenting_containers.html"><img src="../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../intrusive.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="auto_unlink_hooks.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="intrusive.safe_hook"></a><a class="link" href="safe_hook.html" title="Safe hooks">Safe hooks</a> 29</h2></div></div></div> 30<div class="toc"><dl class="toc"> 31<dt><span class="section"><a href="safe_hook.html#intrusive.safe_hook.features">Features of the safe mode</a></span></dt> 32<dt><span class="section"><a href="safe_hook.html#intrusive.safe_hook.configuring">Configuring safe-mode 33 assertions</a></span></dt> 34</dl></div> 35<div class="section"> 36<div class="titlepage"><div><div><h3 class="title"> 37<a name="intrusive.safe_hook.features"></a><a class="link" href="safe_hook.html#intrusive.safe_hook.features" title="Features of the safe mode">Features of the safe mode</a> 38</h3></div></div></div> 39<p> 40 <span class="bold"><strong>Boost.Intrusive</strong></span> hooks can be configured 41 to operate in safe-link mode. The safe mode is activated by default, but 42 it can be also explicitly activated: 43 </p> 44<pre class="programlisting"><span class="comment">//Configuring the safe mode explicitly</span> 45<span class="keyword">class</span> <span class="identifier">Foo</span> <span class="special">:</span> <span class="keyword">public</span> <span class="identifier">list_base_hook</span><span class="special"><</span> <span class="identifier">link_mode</span><span class="special"><</span><span class="identifier">safe_link</span><span class="special">></span> <span class="special">></span> 46<span class="special">{};</span> 47</pre> 48<p> 49 With the safe mode the user can detect if the object is actually inserted 50 in a container without any external reference. Let's review the basic features 51 of the safe mode: 52 </p> 53<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 54<li class="listitem"> 55 Hook's constructor puts the hook in a well-known default state. 56 </li> 57<li class="listitem"> 58 Hook's destructor checks if the hook is in the well-known default state. 59 If not, an assertion is raised. 60 </li> 61<li class="listitem"> 62 Every time an object is inserted in the intrusive container, the container 63 checks if the hook is in the well-known default state. If not, an assertion 64 is raised. 65 </li> 66<li class="listitem"> 67 Every time an object is being erased from the intrusive container, the 68 container puts the erased object in the well-known default state. 69 </li> 70</ul></div> 71<p> 72 With these features, without any external reference the user can know if 73 the object has been inserted in a container by calling the <code class="computeroutput"><span class="identifier">is_linked</span><span class="special">()</span></code> 74 member function. If the object is not actually inserted in a container, the 75 hook is in the default state, and if it is inserted in a container, the hook 76 is not in the default state. 77 </p> 78</div> 79<div class="section"> 80<div class="titlepage"><div><div><h3 class="title"> 81<a name="intrusive.safe_hook.configuring"></a><a class="link" href="safe_hook.html#intrusive.safe_hook.configuring" title="Configuring safe-mode assertions">Configuring safe-mode 82 assertions</a> 83</h3></div></div></div> 84<p> 85 By default, all safe-mode assertions raised by <span class="bold"><strong>Boost-Intrusive</strong></span> 86 hooks and containers in are implemented using <code class="computeroutput"><span class="identifier">BOOST_ASSERT</span></code>, 87 which can be configured by the user. See <a href="http://www.boost.org/libs/utility/assert.html" target="_top">http://www.boost.org/libs/utility/assert.html</a> 88 for more information about <code class="computeroutput"><span class="identifier">BOOST_ASSERT</span></code>. 89 </p> 90<p> 91 <code class="computeroutput"><span class="identifier">BOOST_ASSERT</span></code> is globally 92 configured, so the user might want to redefine intrusive safe-mode assertions 93 without modifying the global <code class="computeroutput"><span class="identifier">BOOST_ASSERT</span></code>. 94 This can be achieved redefining the following macros: 95 </p> 96<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 97<li class="listitem"> 98 <code class="computeroutput"><span class="identifier">BOOST_INTRUSIVE_SAFE_HOOK_DEFAULT_ASSERT</span></code>: 99 This assertion will be used in insertion functions of the intrusive containers 100 to check that the hook of the value to be inserted is default constructed. 101 </li> 102<li class="listitem"> 103 <code class="computeroutput"><span class="identifier">BOOST_INTRUSIVE_SAFE_HOOK_DESTRUCTOR_ASSERT</span></code>: 104 This assertion will be used in hooks' destructors to check that the hook 105 is in a default state. 106 </li> 107</ul></div> 108<p> 109 If any of these macros is not redefined, the assertion will default to <code class="computeroutput"><span class="identifier">BOOST_ASSERT</span></code>. If <code class="computeroutput"><span class="identifier">BOOST_INTRUSIVE_SAFE_HOOK_DEFAULT_ASSERT</span></code> 110 or <code class="computeroutput"><span class="identifier">BOOST_INTRUSIVE_SAFE_HOOK_DESTRUCTOR_ASSERT</span></code> 111 is defined and the programmer needs to include a file to configure that assertion, 112 it can define <code class="computeroutput"><span class="identifier">BOOST_INTRUSIVE_SAFE_HOOK_DESTRUCTOR_ASSERT_INCLUDE</span></code> 113 or <code class="computeroutput"><span class="identifier">BOOST_INTRUSIVE_SAFE_HOOK_DEFAULT_ASSERT_INCLUDE</span></code> 114 with the name of the file to include: 115 </p> 116<pre class="programlisting"><span class="preprocessor">#define</span> <span class="identifier">BOOST_INTRUSIVE_SAFE_HOOK_DESTRUCTOR_ASSERT</span> <span class="identifier">MYASSERT</span> 117<span class="preprocessor">#define</span> <span class="identifier">BOOST_INTRUSIVE_SAFE_HOOK_DESTRUCTOR_ASSERT_INCLUDE</span> <span class="special"><</span><span class="identifier">myassert</span><span class="special">.</span><span class="identifier">h</span><span class="special">></span> 118</pre> 119</div> 120</div> 121<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 122<td align="left"></td> 123<td align="right"><div class="copyright-footer">Copyright © 2005 Olaf Krzikalla<br>Copyright © 2006-2015 Ion Gaztanaga<p> 124 Distributed under the Boost Software License, Version 1.0. (See accompanying 125 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>) 126 </p> 127</div></td> 128</tr></table> 129<hr> 130<div class="spirit-nav"> 131<a accesskey="p" href="presenting_containers.html"><img src="../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../intrusive.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="auto_unlink_hooks.html"><img src="../../../doc/src/images/next.png" alt="Next"></a> 132</div> 133</body> 134</html> 135
