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- <title>The Boost Statechart Library - Configuration</title>
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- <h3><a href="../../../index.htm"><img alt="C++ Boost" src=
- "../../../boost.png" border="0" width="277" height="86"></a></h3>
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- <h1 align="center">The Boost Statechart Library</h1>
- <h2 align="center">Configuration</h2>
- </td>
- </tr>
- </table>
- <hr>
- <dl class="page-index">
- <dt><a href="#GeneralConfiguration">General configuration</a></dt>
- <dd><a href="#Introduction">Introduction</a></dd>
- <dd><a href="#DebugModeCompilationOptions">Debug mode compilation
- options</a></dd>
- <dd><a href="#ReleaseModeCompilationOptions">Release mode compilation
- options</a></dd>
- <dd><a href="#ApplicationDefinedMacros">Application Defined
- Macros</a></dd>
- </dl>
- <h1><a id="GeneralConfiguration" name="GeneralConfiguration">General
- configuration</a></h1>
- <h2><a id="Introduction" name="Introduction">Introduction</a></h2>
- <p>The library uses several configuration macros in <a href=
- "../../../libs/config/config.htm"><boost/config.hpp></a>, as well as
- two configuration macros meant to be supplied by the application. Moreover,
- two commonly available compiler options also have an impact on the
- available features.</p>
- <h2><a id="DebugModeCompilationOptions" name=
- "DebugModeCompilationOptions">Debug mode compilation options</a></h2>
- <ul>
- <li>C++ RTTI must be turned on (used by various asserts)</li>
- <li>C++ exception handling can be turned on or off. When turned off,
- obviously the library's <a href="tutorial.html#ExceptionHandling">error
- handling support</a> is no longer available</li>
- </ul>
- <h2><a id="ReleaseModeCompilationOptions" name=
- "ReleaseModeCompilationOptions">Release mode compilation options</a></h2>
- <ul>
- <li>C++ RTTI can be turned on or off. When turned off, the use of
- <code><a href="reference.html#state_cast">state_cast<>()</a></code>
- leads to a compile time error (<code><a href=
- "reference.html#state_downcast">state_downcast<>()</a></code> is
- still available). Moreover, <code>BOOST_STATECHART_USE_NATIVE_RTTI</code>
- must not be defined simultaneously</li>
- <li>C++ exception handling can be turned on or off. When turned off,
- obviously the library's <a href="tutorial.html#ExceptionHandling">error
- handling support</a> is no longer available</li>
- </ul>
- <h2><a id="ApplicationDefinedMacros" name=
- "ApplicationDefinedMacros">Application Defined Macros</a></h2>
- <p>The following macros may be defined by an application using the
- library:</p>
- <table summary="application defined macros" width="100%" cellpadding="2"
- border="3">
- <tr>
- <td width="226"><b>Macro</b></td>
- <td width="893"><b>Meaning</b></td>
- </tr>
- <tr>
- <td width="226"><code>BOOST_STATECHART_USE_NATIVE_RTTI</code></td>
- <td width="893">
- When defined, the library no longer uses its own speed-optimized RTTI
- implementation. Instead, native C++ RTTI is employed (see <a href=
- "performance.html#RttiCustomization">RTTI customization</a> in the
- performance document for more information). This has the following
- effects:
- <ul>
- <li><code>state_machine::state_base_type</code> becomes a
- polymorphic type. That is, when <code>typeid</code> is applied to a
- <code>state_machine::state_base_type</code> reference, the result
- refers to a <code>type_info</code> object representing the the type
- of the most derived state type</li>
- <li><a href="tutorial.html#CustomStateTypeInformation">Custom state
- type information</a> is no longer available</li>
- <li>All states need to store one pointer less, leading to a
- best-case state machine memory footprint reduction of about
- 15%</li>
- <li>Under most circumstances, dispatch speed degrades. This is
- because native C++ RTTI values are retrieved through an additional
- indirection on almost all platforms. See <a href=
- "performance.html#SpeedVersusScalabilityTradeoffs">Speed versus
- scalability tradeoffs</a> in the performance document for
- timings</li>
- </ul>
- </td>
- </tr>
- <tr>
- <td width="226">
- <code>BOOST_STATECHART_RELAX_TRANSITION_CONTEXT</code></td>
- <td width="893">When defined, the sequence of actions that are called
- during a transition is relaxed. That is, its is no longer necessary
- that all states up to the innermost common context are exited before
- the transition action is called (as mandated by the UML standard).
- Instead, the transition action can be a member of either the transition
- source or any direct or indirect outer context and is called as soon as
- all possibly active inner states have been exited. Then all remaining
- active states up to the innermost common context are exited before
- entering all states down to the transition destination</td>
- </tr>
- </table>
- <p>Both macros need to be consistently defined or undefined for all
- translation units that are later linked into the same executable. Not doing
- so will inevitably lead to ODR violations. Depending on compiler and linker
- technology such violations may or may not manifest themselves in link-time
- errors.</p>
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- "../../../doc/images/valid-html401.png" alt="Valid HTML 4.01 Transitional"
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- <p>Revised 05 January, 2008</p>
- <p><i>Copyright © 2003-2008 <a href="contact.html">Andreas Huber
- Dönni</a></i></p>
- <p><i>Distributed under the Boost Software License, Version 1.0. (See
- accompanying file <a href="../../../LICENSE_1_0.txt">LICENSE_1_0.txt</a> or
- copy at <a href=
- "http://www.boost.org/LICENSE_1_0.txt">http://www.boost.org/LICENSE_1_0.txt</a>)</i></p>
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