| Brian Silverman | af2eaa8 | 2018-08-04 17:28:31 -0700 | [diff] [blame^] | 1 | <html> |
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| 26 | <div class="titlepage"><div><div><h2 class="title" style="clear: both"> |
| 27 | <a name="boost_optional.implementation_notes"></a><a class="link" href="implementation_notes.html" title="Implementation Notes">Implementation Notes</a> |
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| 29 | <p> |
| 30 | <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> is |
| 31 | 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> |
| 32 | (both from Type Traits). It uses a separate boolean flag to indicate the initialization |
| 33 | state. Placement new with <code class="computeroutput"><span class="identifier">T</span></code>'s |
| 34 | copy/move constructor and <code class="computeroutput"><span class="identifier">T</span></code>'s |
| 35 | destructor are explicitly used to initialize, copy, move and destroy optional |
| 36 | values. As a result, <code class="computeroutput"><span class="identifier">T</span></code>'s default |
| 37 | constructor is effectively by-passed, but the exception guarantees are basic. |
| 38 | It is planned to replace the current implementation with another with stronger |
| 39 | exception safety, such as a future <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">variant</span></code>. |
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| 43 | <td align="left"></td> |
| 44 | <td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright © 2014 Andrzej Krzemieński<p> |
| 45 | Distributed under the Boost Software License, Version 1.0. (See accompanying |
| 46 | 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>) |
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