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<div class="section">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="boost_dll.limitations"></a><a class="link" href="limitations.html" title="Limitations">Limitations</a>
</h2></div></div></div>
<div class="toc"><dl class="toc">
<dt><span class="section"><a href="limitations.html#boost_dll.limitations.exporting_weak_symbols__fails_on_mingw__android_">Exporting
weak symbols (Fails on MinGW, Android)</a></span></dt>
<dt><span class="section"><a href="limitations.html#boost_dll.limitations.user_defined_section_names__fails_on_sunos___oracle_solaris_studio_compilers_">User
defined section names (Fails on SunOS + Oracle Solaris Studio Compilers)</a></span></dt>
<dt><span class="section"><a href="limitations.html#boost_dll.limitations.multithread">Thread safe library
loading (Fails on FreeBSD, MacOS, iOS and some other)</a></span></dt>
<dt><span class="section"><a href="limitations.html#boost_dll.limitations.nested">Nested Function Definitions</a></span></dt>
</dl></div>
<p>
Some platforms and compilers do not provide all the required functionality
to have a fully functional Boost.DLL. Such compilers are mentioned in this
section along with possible workarounds for those limitations.
</p>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="boost_dll.limitations.exporting_weak_symbols__fails_on_mingw__android_"></a><a class="link" href="limitations.html#boost_dll.limitations.exporting_weak_symbols__fails_on_mingw__android_" title="Exporting weak symbols (Fails on MinGW, Android)">Exporting
weak symbols (Fails on MinGW, Android)</a>
</h3></div></div></div>
<p>
Some versions of Android, <code class="computeroutput"><span class="identifier">MinGW</span></code>
and <code class="computeroutput"><span class="identifier">ld</span></code> on Windows platform
fail to mix <code class="computeroutput"><span class="identifier">__dllexport__</span></code>
and <code class="computeroutput"><span class="identifier">weak</span></code> attributes. This
leads us to situation, where we must explicitly specify translation unit
in which <code class="computeroutput"><a class="link" href="../BOOST_DLL_ALIAS.html" title="Macro BOOST_DLL_ALIAS">BOOST_DLL_ALIAS</a></code> is
instantiated, making all other <code class="computeroutput"><a class="link" href="../BOOST_DLL_ALIAS.html" title="Macro BOOST_DLL_ALIAS">BOOST_DLL_ALIAS</a></code>
declarations with that alias name an <code class="computeroutput"><span class="keyword">extern</span></code>
variable.
</p>
<p>
Unit that must hold an instance of <code class="computeroutput"><a class="link" href="../BOOST_DLL_ALIAS.html" title="Macro BOOST_DLL_ALIAS">BOOST_DLL_ALIAS</a></code>
must define <code class="computeroutput"><a class="link" href="../BOOST_DLL_FORCE_ALIAS_INSTANTIATION.html" title="Macro BOOST_DLL_FORCE_ALIAS_INSTANTIATION">BOOST_DLL_FORCE_ALIAS_INSTANTIATION</a></code>
before including any of the Boost.DLL library headers.
</p>
<p>
You may explicitly disable export of weak symbols using <code class="computeroutput"><a class="link" href="../BOOST_DLL_FORCE_NO_WEAK_EXPORTS.html" title="Macro BOOST_DLL_FORCE_NO_WEAK_EXPORTS">BOOST_DLL_FORCE_NO_WEAK_EXPORTS</a></code>.
This may be usefull for working around linker problems or to test your program
for compatability with linkers that do not support exporting weak symbols.
</p>
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<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="boost_dll.limitations.user_defined_section_names__fails_on_sunos___oracle_solaris_studio_compilers_"></a><a class="link" href="limitations.html#boost_dll.limitations.user_defined_section_names__fails_on_sunos___oracle_solaris_studio_compilers_" title="User defined section names (Fails on SunOS + Oracle Solaris Studio Compilers)">User
defined section names (Fails on SunOS + Oracle Solaris Studio Compilers)</a>
</h3></div></div></div>
<p>
Some platforms ignore section attributes, so that querying for a symbols
in a specified section using <code class="computeroutput"><a class="link" href="../boost/dll/library_info.html" title="Class library_info">boost::dll::library_info</a></code>
may return nothing.
</p>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="boost_dll.limitations.multithread"></a><a class="link" href="limitations.html#boost_dll.limitations.multithread" title="Thread safe library loading (Fails on FreeBSD, MacOS, iOS and some other)">Thread safe library
loading (Fails on FreeBSD, MacOS, iOS and some other)</a>
</h3></div></div></div>
<p>
On some platforms <code class="computeroutput"><span class="identifier">dlopen</span></code>,<code class="computeroutput"><span class="identifier">dlclose</span></code> and some other functions assume
that they won't be called concurrently.
</p>
<p>
Platforms that certaly have that issue are FreeBSD, MacOS, iOS.
</p>
<p>
Platforms that certaly do not have such issue are Windows, Linux+glibc, Android,
QNX.
</p>
<p>
Other platforms are under question. If you're using one of the platforms
that are not listed (for example Linux+busybox), you may run the <code class="computeroutput"><span class="identifier">shared_library_concurrent_load_test</span></code> test
to detect the issue:
</p>
<pre class="programlisting"><span class="identifier">cd</span> <span class="identifier">boost_folder</span><span class="special">/</span><span class="identifier">libs</span><span class="special">/</span><span class="identifier">dll</span><span class="special">/</span><span class="identifier">test</span>
<span class="special">../../../</span><span class="identifier">b2</span> <span class="special">-</span><span class="identifier">a</span> <span class="identifier">shared_library_concurrent_load_test</span>
</pre>
<p>
</p>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="boost_dll.limitations.nested"></a><a class="link" href="limitations.html#boost_dll.limitations.nested" title="Nested Function Definitions">Nested Function Definitions</a>
</h3></div></div></div>
<p>
If a function is defined inside the class-definition it may be interpreted
as always-inline which can lead to the function not being exported at all.
This does however differ between between compilers.
</p>
</div>
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<td align="right"><div class="copyright-footer">Copyright © 2014 Renato Tegon Forti, Antony Polukhin<br>Copyright © 2015 Antony Polukhin<br>Copyright © 2016 Antony Polukhin, Klemens Morgenstern<p>
Distributed under the Boost Software License, Version 1.0. (See accompanying
file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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