libs/contract/doc/html/BOOST_CO_idm45394998587680.html

   1 <html>
   2 <head>
   3 <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
   4 <title>Macro BOOST_CONTRACT_CONSTRUCTOR_PRECONDITION</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&#160;1.&#160;Boost.Contract 1.0.0">
   8 <link rel="up" href="reference.html#header.boost.contract_macro_hpp" title="Header &lt;boost/contract_macro.hpp&gt;">
   9 <link rel="prev" href="BOOST_CONTRACT_CONSTRUCTOR.html" title="Macro BOOST_CONTRACT_CONSTRUCTOR">
  10 <link rel="next" href="BOOST_CONTRACT_DESTRUCTOR.html" title="Macro BOOST_CONTRACT_DESTRUCTOR">
  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="BOOST_CONTRACT_CONSTRUCTOR.html"><img src="../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="reference.html#header.boost.contract_macro_hpp"><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="BOOST_CONTRACT_DESTRUCTOR.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a>
  24 </div>
  25 <div class="refentry">
  26 <a name="BOOST_CO_idm45394998587680"></a><div class="titlepage"></div>
  27 <div class="refnamediv">
  28 <h2><span class="refentrytitle">Macro BOOST_CONTRACT_CONSTRUCTOR_PRECONDITION</span></h2>
  29 <p>BOOST_CONTRACT_CONSTRUCTOR_PRECONDITION &#8212; Program preconditions that can be disabled at compile-time for constructors. </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_CONSTRUCTOR_PRECONDITION(...)</pre></div>
  35 <div class="refsect1">
  36 <a name="idm45707992490480"></a><h2>Description</h2>
  37 <p>This is used together with <code class="computeroutput"><a class="link" href="BOOST_CONTRACT_CONSTRUCTOR.html" title="Macro BOOST_CONTRACT_CONSTRUCTOR">BOOST_CONTRACT_CONSTRUCTOR</a></code> to specify contracts for constructors. Constructors that do not have preconditions do not use this macro. When at least one of the class constructors uses this macro,  <code class="computeroutput"><a class="link" href="boost/contract/constructor_precondition.html" title="Class template constructor_precondition">boost::contract::constructor_precondition</a></code> must be the first and private base of the class declaring the constructor for which preconditions are programmed:</p>
  38 <pre class="programlisting"><span class="keyword">class</span> <span class="identifier">u</span>
  39     <span class="preprocessor">#define</span> <span class="identifier">BASES</span> <span class="keyword">private</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">contract</span><span class="special">::</span><span class="identifier">constructor_precondition</span><span class="special">&lt;</span><span class="identifier">u</span><span class="special">&gt;</span><span class="special">,</span> \
  40             <span class="keyword">public</span> <span class="identifier">b</span>
  41     <span class="special">:</span> <span class="identifier">BASES</span>
  42 <span class="special">{</span>
  43     <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>
  44
  45     <span class="keyword">typedef</span> <span class="identifier">BOOST_CONTRACT_BASE_TYPES</span><span class="special">(</span><span class="identifier">BASES</span><span class="special">)</span> <span class="identifier">base_types</span><span class="special">;</span>
  46     <span class="preprocessor">#undef</span> <span class="identifier">BASES</span>
  47
  48     <span class="special">...</span>
  49
  50 <span class="keyword">public</span><span class="special">:</span>
  51     <span class="keyword">explicit</span> <span class="identifier">u</span><span class="special">(</span><span class="keyword">unsigned</span> <span class="identifier">x</span><span class="special">)</span> <span class="special">:</span>
  52         <span class="identifier">BOOST_CONTRACT_CONSTRUCTOR_PRECONDITION</span><span class="special">(</span><span class="identifier">u</span><span class="special">)</span><span class="special">(</span><span class="special">[</span><span class="special">&amp;</span><span class="special">]</span> <span class="special">{</span>
  53             <span class="identifier">BOOST_CONTRACT_ASSERT</span><span class="special">(</span><span class="identifier">x</span> <span class="special">!=</span> <span class="number">0</span><span class="special">)</span><span class="special">;</span>
  54         <span class="special">}</span><span class="special">)</span><span class="special">,</span>
  55         <span class="identifier">b</span><span class="special">(</span><span class="number">1</span> <span class="special">/</span> <span class="identifier">x</span><span class="special">)</span>
  56     <span class="special">{</span>
  57         <span class="special">...</span>
  58     <span class="special">}</span>
  59
  60     <span class="special">...</span>
  61 <span class="special">}</span><span class="special">;</span>
  62 </pre>
  63 <p><code class="computeroutput">BOOST_CONTRACT_CONSTRUCTOR_PRECONDITION(class_type)(f)</code> expands to code equivalent to the following (note that when  <code class="computeroutput"><a class="link" href="BOOST_CO_idm45394999662416.html" title="Macro BOOST_CONTRACT_NO_PRECONDITIONS">BOOST_CONTRACT_NO_PRECONDITIONS</a></code> is defined, this macro trivially expands to a default constructor call that is internally implemented to do nothing so this should have minimal to no overhead):</p>
  64 <pre class="programlisting"><span class="comment">// Guarded only by NO_PRECONDITIONS (and not also by NO_CONSTRUCTORS)</span>
  65 <span class="comment">// because for constructor's preconditions (not for postconditions, etc.).</span>
  66 <span class="preprocessor">#ifndef</span> <span class="identifier">BOOST_CONTRACT_NO_PRECONDITIONS</span>
  67     <span class="identifier">boost</span><span class="special">::</span><span class="identifier">contract</span><span class="special">::</span><span class="identifier">constructor_precondition</span><span class="special">&lt;</span><span class="identifier">class_type</span><span class="special">&gt;</span><span class="special">(</span><span class="identifier">f</span><span class="special">)</span>
  68 <span class="preprocessor">#else</span> <span class="comment">// No-op call (likely optimized away, minimal to no overhead).</span>
  69     <span class="identifier">boost</span><span class="special">::</span><span class="identifier">contract</span><span class="special">::</span><span class="identifier">constructor_precondition</span><span class="special">&lt;</span><span class="identifier">class_type</span><span class="special">&gt;</span><span class="special">(</span><span class="special">)</span>
  70 <span class="preprocessor">#endif</span>
  71 </pre>
  72 <p>Where:</p>
  73 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
  74 <li class="listitem"><p><code class="computeroutput"><span class="bold"><strong>class_type</strong></span></code> is the type of the class containing the constructor for which preconditions are being programmed. (This is a variadic macro parameter so it can contain commas not protected by round parenthesis.) </p></li>
  75 <li class="listitem"><p><code class="computeroutput"><span class="bold"><strong>f</strong></span></code> is the nullary functor called by this library to check constructor preconditions <code class="computeroutput">f()</code>. Assertions within this functor call are usually programmed using  <code class="computeroutput"><a class="link" href="BOOST_CONTRACT_ASSERT.html" title="Macro BOOST_CONTRACT_ASSERT">BOOST_CONTRACT_ASSERT</a></code>, but any exception thrown by a call to this functor indicates a contract failure (and will result in this library calling  <code class="computeroutput"><a class="link" href="boost/contract/precondition_failure.html" title="Function precondition_failure">boost::contract::precondition_failure</a></code>). This functor should capture variables by (constant) value, or better by (constant) reference to avoid extra copies. (This is a variadic macro parameter so it can contain commas not protected by round parenthesis.)</p></li>
  76 </ul></div>
  77 <p>
  78 </p>
  79 <p><span class="bold"><strong>See Also:</strong></span></p>
  80 <p> <a class="link" href="boost_contract/extras.html#boost_contract.extras.disable_contract_compilation__macro_interface_" title="Disable Contract Compilation (Macro Interface)">
  81         Disable Contract Compilation</a>,  <a class="link" href="boost_contract/tutorial.html#boost_contract.tutorial.constructors" title="Constructors"> Constructors</a> </p>
  82 <p>
  83 </p>
  84 <p>
  85 </p>
  86 </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 &#169; 2008-2019 Lorenzo Caminiti<p>
  91         Distributed under the Boost Software License, Version 1.0 (see accompanying
  92         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>)
  93       </p>
  94 </div></td>
  95 </tr></table>
  96 <hr>
  97 <div class="spirit-nav">
  98 <a accesskey="p" href="BOOST_CONTRACT_CONSTRUCTOR.html"><img src="../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="reference.html#header.boost.contract_macro_hpp"><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="BOOST_CONTRACT_DESTRUCTOR.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a>
  99 </div>
 100 </body>
 101 </html>