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26<a name="BOOST_CONTRACT_DESTRUCTOR"></a><div class="titlepage"></div>
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28<h2><span class="refentrytitle">Macro BOOST_CONTRACT_DESTRUCTOR</span></h2>
29<p>BOOST_CONTRACT_DESTRUCTOR — Program contracts that can be completely disabled at compile-time for destructors. </p>
30</div>
31<h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2>
32<div xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv"><pre class="synopsis"><span class="comment">// In header: &lt;<a class="link" href="reference.html#header.boost.contract_macro_hpp" title="Header &lt;boost/contract_macro.hpp&gt;">boost/contract_macro.hpp</a>&gt;
33
34</span>BOOST_CONTRACT_DESTRUCTOR(...)</pre></div>
35<div class="refsect1">
36<a name="idm45988675198096"></a><h2>Description</h2>
37<p>This is used together with <code class="computeroutput"><a class="link" href="BOOST_CO_idm46268584548992.html" title="Macro BOOST_CONTRACT_POSTCONDITION">BOOST_CONTRACT_POSTCONDITION</a></code>,  <code class="computeroutput"><a class="link" href="BOOST_CONTRACT_EXCEPT.html" title="Macro BOOST_CONTRACT_EXCEPT">BOOST_CONTRACT_EXCEPT</a></code>, and <code class="computeroutput"><a class="link" href="BOOST_CONTRACT_OLD.html" title="Macro BOOST_CONTRACT_OLD">BOOST_CONTRACT_OLD</a></code> to specify postconditions, exception guarantees, and old value copies at body that can be completely disabled at compile-time for destructors (destructors cannot have preconditions, see  <a class="link" href="boost_contract/contract_programming_overview.html#boost_contract.contract_programming_overview.destructor_calls" title="Destructor Calls"> Destructor Calls</a>):</p>
38<pre class="programlisting"><span class="keyword">class</span> <span class="identifier">u</span> <span class="special">{</span>
39    <span class="keyword">friend</span> <span class="keyword">class</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">contract</span><span class="special">::</span><span class="identifier">access</span><span class="special">;</span>
40
41    <span class="identifier">BOOST_CONTRACT_INVARIANT</span><span class="special">(</span><span class="special">{</span> <span class="comment">// Optional (as for static and volatile).</span>
42        <span class="identifier">BOOST_CONTRACT_ASSERT</span><span class="special">(</span><span class="special">...</span><span class="special">)</span><span class="special">;</span>
43        <span class="special">...</span>
44    <span class="special">}</span><span class="special">)</span>
45
46<span class="keyword">public</span><span class="special">:</span>
47    <span class="special">~</span><span class="identifier">u</span><span class="special">(</span><span class="special">)</span> <span class="special">{</span>
48        <span class="identifier">BOOST_CONTRACT_OLD_PTR</span><span class="special">(</span><span class="identifier">old_type</span><span class="special">)</span><span class="special">(</span><span class="identifier">old_var</span><span class="special">)</span><span class="special">;</span>
49        <span class="identifier">BOOST_CONTRACT_DESTRUCTOR</span><span class="special">(</span><span class="keyword">this</span><span class="special">)</span>
50            <span class="comment">// No `PRECONDITION` (destructors have no preconditions).</span>
51            <span class="identifier">BOOST_CONTRACT_OLD</span><span class="special">(</span><span class="special">[</span><span class="special">&amp;</span><span class="special">]</span> <span class="special">{</span> <span class="comment">// Optional.</span>
52                <span class="identifier">old_var</span> <span class="special">=</span> <span class="identifier">BOOST_CONTRACT_OLDOF</span><span class="special">(</span><span class="identifier">old_expr</span><span class="special">)</span><span class="special">;</span>
53                <span class="special">...</span>
54            <span class="special">}</span><span class="special">)</span>
55            <span class="identifier">BOOST_CONTRACT_POSTCONDITION</span><span class="special">(</span><span class="special">[</span><span class="special">&amp;</span><span class="special">]</span> <span class="special">{</span> <span class="comment">// Optional.</span>
56                <span class="identifier">BOOST_CONTRACT_ASSERT</span><span class="special">(</span><span class="special">...</span><span class="special">)</span><span class="special">;</span>
57                <span class="special">...</span>
58            <span class="special">}</span><span class="special">)</span>
59            <span class="identifier">BOOST_CONTRACT_EXCEPT</span><span class="special">(</span><span class="special">[</span><span class="special">&amp;</span><span class="special">]</span> <span class="special">{</span> <span class="comment">// Optional.</span>
60                <span class="identifier">BOOST_CONTRACT_ASSERT</span><span class="special">(</span><span class="special">...</span><span class="special">)</span><span class="special">;</span>
61                <span class="special">...</span>
62            <span class="special">}</span><span class="special">)</span>
63        <span class="special">;</span> <span class="comment">// Trailing `;` is required.</span>
64
65        <span class="special">...</span> <span class="comment">// Destructor body.</span>
66    <span class="special">}</span>
67
68    <span class="special">...</span>
69<span class="special">}</span><span class="special">;</span>
70</pre>
71<p>For optimization, this can be omitted for destructors that do not have postconditions and exception guarantees, within classes that have no invariants.</p>
72<p><code class="computeroutput">BOOST_CONTRACT_DESTRUCTOR(obj)</code> expands to code equivalent to the following (note that no code is generated when  <code class="computeroutput"><a class="link" href="BOOST_CO_idm46268585407008.html" title="Macro BOOST_CONTRACT_NO_DESTRUCTORS">BOOST_CONTRACT_NO_DESTRUCTORS</a></code> is defined):</p>
73<pre class="programlisting"><span class="preprocessor">#ifndef</span> <span class="identifier">BOOST_CONTRACT_NO_DESTRUCTORS</span>
74    <span class="identifier">boost</span><span class="special">::</span><span class="identifier">contract</span><span class="special">::</span><span class="identifier">check</span> <span class="identifier">internal_var</span> <span class="special">=</span>
75            <span class="identifier">boost</span><span class="special">::</span><span class="identifier">contract</span><span class="special">::</span><span class="identifier">destructor</span><span class="special">(</span><span class="identifier">obj</span><span class="special">)</span>
76<span class="preprocessor">#endif</span>
77</pre>
78<p>Where:</p>
79<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
80<li class="listitem"><p><code class="computeroutput"><span class="bold"><strong>obj</strong></span></code> is the object <code class="computeroutput">this</code> from the scope of the enclosing destructor declaring the contract. Destructors check all class invariants, including static and volatile invariants (see <a class="link" href="boost_contract/tutorial.html#boost_contract.tutorial.class_invariants" title="Class Invariants">
81        Class Invariants</a> and  <a class="link" href="boost_contract/extras.html#boost_contract.extras.volatile_public_functions" title="Volatile Public Functions">
82        Volatile Public Functions</a>). (This is a variadic macro parameter so it can contain commas not protected by round parenthesis.) </p></li>
83<li class="listitem"><p><code class="computeroutput"><span class="bold"><strong>internal_var</strong></span></code> is a variable name internally generated by this library (this name is unique but only on different line numbers so this macro cannot be expanded multiple times on the same line).</p></li>
84</ul></div>
85<p>
86</p>
87<p><span class="bold"><strong>See Also:</strong></span></p>
88<p> <a class="link" href="boost_contract/extras.html#boost_contract.extras.disable_contract_compilation__macro_interface_" title="Disable Contract Compilation (Macro Interface)">
89        Disable Contract Compilation</a>,  <a class="link" href="boost_contract/tutorial.html#boost_contract.tutorial.destructors" title="Destructors"> Destructors</a> </p>
90<p>
91</p>
92<p>
93</p>
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98<td align="right"><div class="copyright-footer">Copyright © 2008-2019 Lorenzo Caminiti<p>
99        Distributed under the Boost Software License, Version 1.0 (see accompanying
100        file LICENSE_1_0.txt or a copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
101      </p>
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