mirror of
https://github.com/boostorg/optional.git
synced 2025-07-14 12:56:35 +02:00
56 lines
4.1 KiB
HTML
56 lines
4.1 KiB
HTML
<html>
|
||
<head>
|
||
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
|
||
<title>Implementation Notes</title>
|
||
<link rel="stylesheet" href="../boostbook.css" type="text/css">
|
||
<meta name="generator" content="DocBook XSL Stylesheets V1.73.2">
|
||
<link rel="start" href="../index.html" title="Chapter 1. Boost.Optional">
|
||
<link rel="up" href="../index.html" title="Chapter 1. Boost.Optional">
|
||
<link rel="prev" href="type_requirements.html" title="Type requirements">
|
||
<link rel="next" href="dependencies_and_portability.html" title="Dependencies and Portability">
|
||
</head>
|
||
<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
|
||
<table cellpadding="2" width="100%"><tr>
|
||
<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../boost.png"></td>
|
||
<td align="center"><a href="../../../../../index.html">Home</a></td>
|
||
<td align="center"><a href="../../../../libraries.htm">Libraries</a></td>
|
||
<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
|
||
<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
|
||
<td align="center"><a href="../../../../../more/index.htm">More</a></td>
|
||
</tr></table>
|
||
<hr>
|
||
<div class="spirit-nav">
|
||
<a accesskey="p" href="type_requirements.html"><img src="../../../../../doc/html/images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.html"><img src="../../../../../doc/html/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../../../doc/html/images/home.png" alt="Home"></a><a accesskey="n" href="dependencies_and_portability.html"><img src="../../../../../doc/html/images/next.png" alt="Next"></a>
|
||
</div>
|
||
<div class="section" lang="en">
|
||
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
|
||
<a name="boost_optional.implementation_notes"></a><a class="link" href="implementation_notes.html" title="Implementation Notes">Implementation Notes</a>
|
||
</h2></div></div></div>
|
||
<p>
|
||
<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> is
|
||
currently implemented using a custom aligned storage facility built from <code class="computeroutput"><span class="identifier">alignment_of</span></code> and <code class="computeroutput"><span class="identifier">type_with_alignment</span></code>
|
||
(both from Type Traits). It uses a separate boolean flag to indicate the initialization
|
||
state. Placement new with <code class="computeroutput"><span class="identifier">T</span></code>'s
|
||
copy constructor and <code class="computeroutput"><span class="identifier">T</span></code>'s destructor
|
||
are explicitly used to initialize,copy and destroy optional values. As a result,
|
||
<code class="computeroutput"><span class="identifier">T</span></code>'s default constructor is
|
||
effectively by-passed, but the exception guarantees are basic. It is planned
|
||
to replace the current implementation with another with stronger exception
|
||
safety, such as a future <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">variant</span></code>.
|
||
</p>
|
||
</div>
|
||
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
|
||
<td align="left"></td>
|
||
<td align="right"><div class="copyright-footer">Copyright © 2003 -2007 Fernando Luis Cacciola Carballal<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>
|
||
</div></td>
|
||
</tr></table>
|
||
<hr>
|
||
<div class="spirit-nav">
|
||
<a accesskey="p" href="type_requirements.html"><img src="../../../../../doc/html/images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.html"><img src="../../../../../doc/html/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../../../doc/html/images/home.png" alt="Home"></a><a accesskey="n" href="dependencies_and_portability.html"><img src="../../../../../doc/html/images/next.png" alt="Next"></a>
|
||
</div>
|
||
</body>
|
||
</html>
|