1<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> 2<html> 3<head> 4<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 5<title>Limitations</title> 6<link rel="stylesheet" href="../../../doc/src/boostbook.css" type="text/css"> 7<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 8<link rel="home" href="../index.html" title="The Boost C++ Libraries BoostBook Documentation Subset"> 9<link rel="up" href="../boost_dll.html" title="Chapter 14. Boost.DLL"> 10<link rel="prev" href="../boost/dll/experimental/import_mangled.html" title="Function import_mangled"> 11<link rel="next" href="f_a_q_.html" title="F.A.Q."> 12</head> 13<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 14<table cellpadding="2" width="100%"><tr> 15<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../boost.png"></td> 16<td align="center"><a href="../../../index.html">Home</a></td> 17<td align="center"><a href="../../../libs/libraries.htm">Libraries</a></td> 18<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> 19<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> 20<td align="center"><a href="../../../more/index.htm">More</a></td> 21</tr></table> 22<hr> 23<div class="spirit-nav"> 24<a accesskey="p" href="../boost/dll/experimental/import_mangled.html"><img src="../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../boost_dll.html"><img src="../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="f_a_q_.html"><img src="../../../doc/src/images/next.png" alt="Next"></a> 25</div> 26<div class="section"> 27<div class="titlepage"><div><div><h2 class="title" style="clear: both"> 28<a name="boost_dll.limitations"></a><a class="link" href="limitations.html" title="Limitations">Limitations</a> 29</h2></div></div></div> 30<div class="toc"><dl class="toc"> 31<dt><span class="section"><a href="limitations.html#boost_dll.limitations.exporting_weak_symbols__fails_on_mingw__android_">Exporting 32 weak symbols (Fails on MinGW, Android)</a></span></dt> 33<dt><span class="section"><a href="limitations.html#boost_dll.limitations.user_defined_section_names__fails_on_sunos___oracle_solaris_studio_compilers_">User 34 defined section names (Fails on SunOS + Oracle Solaris Studio Compilers)</a></span></dt> 35<dt><span class="section"><a href="limitations.html#boost_dll.limitations.multithread">Thread safe library 36 loading (Fails on FreeBSD, MacOS, iOS and some other)</a></span></dt> 37<dt><span class="section"><a href="limitations.html#boost_dll.limitations.nested">Nested Function Definitions</a></span></dt> 38</dl></div> 39<p> 40 Some platforms and compilers do not provide all the required functionality 41 to have a fully functional Boost.DLL. Such compilers are mentioned in this 42 section along with possible workarounds for those limitations. 43 </p> 44<div class="section"> 45<div class="titlepage"><div><div><h3 class="title"> 46<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 47 weak symbols (Fails on MinGW, Android)</a> 48</h3></div></div></div> 49<p> 50 Some versions of Android, <code class="computeroutput"><span class="identifier">MinGW</span></code> 51 and <code class="computeroutput"><span class="identifier">ld</span></code> on Windows platform 52 fail to mix <code class="computeroutput"><span class="identifier">__dllexport__</span></code> 53 and <code class="computeroutput"><span class="identifier">weak</span></code> attributes. This 54 leads us to situation, where we must explicitly specify translation unit 55 in which <code class="computeroutput"><a class="link" href="../BOOST_DLL_ALIAS.html" title="Macro BOOST_DLL_ALIAS">BOOST_DLL_ALIAS</a></code> is 56 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> 57 declarations with that alias name an <code class="computeroutput"><span class="keyword">extern</span></code> 58 variable. 59 </p> 60<p> 61 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> 62 must define <code class="computeroutput"><a class="link" href="../BOOST_DL_idm45168081497664.html" title="Macro BOOST_DLL_FORCE_ALIAS_INSTANTIATION">BOOST_DLL_FORCE_ALIAS_INSTANTIATION</a></code> 63 before including any of the Boost.DLL library headers. 64 </p> 65<p> 66 You may explicitly disable export of weak symbols using <code class="computeroutput"><a class="link" href="../BOOST_DL_idm45168081495856.html" title="Macro BOOST_DLL_FORCE_NO_WEAK_EXPORTS">BOOST_DLL_FORCE_NO_WEAK_EXPORTS</a></code>. 67 This may be useful for working around linker problems or to test your program 68 for compatibility with linkers that do not support exporting weak symbols. 69 </p> 70</div> 71<div class="section"> 72<div class="titlepage"><div><div><h3 class="title"> 73<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 74 defined section names (Fails on SunOS + Oracle Solaris Studio Compilers)</a> 75</h3></div></div></div> 76<p> 77 Some platforms ignore section attributes, so that querying for a symbols 78 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> 79 may return nothing. 80 </p> 81</div> 82<div class="section"> 83<div class="titlepage"><div><div><h3 class="title"> 84<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 85 loading (Fails on FreeBSD, MacOS, iOS and some other)</a> 86</h3></div></div></div> 87<p> 88 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 89 that they won't be called concurrently. 90 </p> 91<p> 92 Platforms that certaly have that issue are FreeBSD, MacOS, iOS. 93 </p> 94<p> 95 Platforms that certaly do not have such issue are Windows, Linux+glibc, Android, 96 QNX. 97 </p> 98<p> 99 Other platforms are under question. If you're using one of the platforms 100 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 101 to detect the issue: 102</p> 103<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> 104<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> 105</pre> 106<p> 107 </p> 108</div> 109<div class="section"> 110<div class="titlepage"><div><div><h3 class="title"> 111<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> 112</h3></div></div></div> 113<p> 114 If a function is defined inside the class-definition it may be interpreted 115 as always-inline which can lead to the function not being exported at all. 116 This does however differ between between compilers. 117 </p> 118</div> 119</div> 120<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 121<td align="left"></td> 122<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<br>Copyright © 2017-2019 Antony Polukhin<p> 123 Distributed under the Boost Software License, Version 1.0. (See accompanying 124 file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) 125 </p> 126</div></td> 127</tr></table> 128<hr> 129<div class="spirit-nav"> 130<a accesskey="p" href="../boost/dll/experimental/import_mangled.html"><img src="../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../boost_dll.html"><img src="../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="f_a_q_.html"><img src="../../../doc/src/images/next.png" alt="Next"></a> 131</div> 132</body> 133</html> 134
