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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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44 <td align=
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"copyright-footer">Copyright
© 2003-
2007 Fernando Luis Cacciola Carballal
<br>Copyright
© 2014 Andrzej Krzemie
ński
<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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