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<div class="title">Caveats When Not Using C++ RTTI </div> </div>
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<div class="toc"><h3>Table of Contents</h3>
<ul><li class="level1"><a href="#overview_cpp_rtti_disabled_bind">Bind() Issues</a></li>
<li class="level1"><a href="#overview_cpp_rtti_disabled_wxany">wxAny Issues</a></li>
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<div class="textblock"><dl class="section note"><dt>Note</dt><dd>C++ RTTI is usually enabled by default in most wxWidgets builds. If you do not know if your build has C++ RTTI enabled or not, then it probably is enabled, and you should not worry about anything mentioned in this section.</dd></dl>
<p>While in general wxWidgets standard <a class="el" href="overview_rtti.html">Runtime Type Information (RTTI)</a> is used throughout the library, there are some places where it won't work. One of those places is template classes.</p>
<p>When available, C++ RTTI is used to address this issue. If you have built the library with C++ RTTI disabled, an internal RTTI system is substituted. However, this system is not perfect and one proven scenario where it may break is a shared library or DLL build. More specifically, a template class instance created in one physical binary may not be recognized as its correct type when used in another one.</p>
<dl class="section see"><dt>See Also</dt><dd><a class="el" href="overview_rtti.html">Runtime Type Information (RTTI)</a>, <a class="el" href="classwx_evt_handler.html#a0f30c8fa5583b4a5f661897d63de3b62" title="Binds the given function, functor or method dynamically with the event.">wxEvtHandler::Bind()</a>, <a class="el" href="classwx_any.html" title="The wxAny class represents a container for any type.">wxAny</a></dd></dl>
<h1><a class="anchor" id="overview_cpp_rtti_disabled_bind"></a>
Bind() Issues</h1>
<p>wxWidgets 2.9.0 introduced a new <a class="el" href="overview_events.html#overview_events_bind">Dynamic Event Handling</a> system, using <a class="el" href="classwx_evt_handler.html#a0f30c8fa5583b4a5f661897d63de3b62" title="Binds the given function, functor or method dynamically with the event.">wxEvtHandler::Bind<>()</a> and Unbind<>(). This functionality uses templates behind the scenes and therefore is vulnerable to breakage in shared library builds, as described above.</p>
<p>Currently only Unbind<>() needs the type information, so you should be immune to this problem simply if you only need to use Bind<>() and not Unbind<>().</p>
<p>Also, if you only bind and unbind same event handler inside same binary, you should be fine.</p>
<h1><a class="anchor" id="overview_cpp_rtti_disabled_wxany"></a>
wxAny Issues</h1>
<p><a class="el" href="classwx_any.html" title="The wxAny class represents a container for any type.">wxAny</a> is a dynamic type class which transparently uses templates to generate data type handlers, and therefore is vulnerable to breakage in shared library builds, as described above</p>
<p>You should be fine if you only create and use <a class="el" href="classwx_any.html" title="The wxAny class represents a container for any type.">wxAny</a> instances inside same physical binary. However, if you do need to be able to use <a class="el" href="classwx_any.html" title="The wxAny class represents a container for any type.">wxAny</a> freely across binary boundaries, (and for sake of code-safety, you probably do), then specializations for wxAnyValueTypeImpl<> templates need to be defined in one of your shared library (DLL) files. One specialization is required for every data type you use with <a class="el" href="classwx_any.html" title="The wxAny class represents a container for any type.">wxAny</a>. Easiest way to do this is using macros provided in <a class="el" href="any_8h.html">wx/any.h</a>. Note that you <b>do</b> <b>not</b> need to define specializations for C built-in types, nor for <a class="el" href="classwx_string.html" title="String class for passing textual data to or receiving it from wxWidgets.">wxString</a> or <a class="el" href="classwx_date_time.html" title="wxDateTime class represents an absolute moment in time.">wxDateTime</a>, because these are already provided in wxBase. However, you <b>do</b> need to define specializations for all pointer types except char* and wchar_t*.</p>
<p>Let's define a specialization for imaginary type 'MyClass'. In your shared library source code you will need to have this line:</p>
<div class="fragment"><div class="line">WX_IMPLEMENT_ANY_VALUE_TYPE(wxAnyValueTypeImpl<MyClass>)</div>
</div><!-- fragment --><p>In your header file you will need the following:</p>
<div class="fragment"><div class="line">wxDECLARE_ANY_TYPE(MyClass, WXIMPORT_OR_WXEXPORT)</div>
</div><!-- fragment --><p>Where WXIMPORT_OR_WXEXPORT is WXEXPORT when being included from the shared library that called the WX_IMPLEMENT_ANY_VALUE_TYPE() macro, and WXIMPORT otherwise. </p>
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