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>Getting started</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.html" title="Chapter 14. Boost.DLL"> 11<link rel="next" href="tutorial.html" title="Tutorial"> 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.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="tutorial.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.getting_started"></a><a class="link" href="getting_started.html" title="Getting started">Getting started</a> 29</h2></div></div></div> 30<p> 31 Boost.DLL is a header only library. To start with the library you only need 32 to include <code class="computeroutput"><span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">dll</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span></code> header. 33 After that you are free to import and export functions and variables. Importing 34 code requires linking with <code class="computeroutput"><span class="identifier">boost_filesystem</span></code> 35 and <code class="computeroutput"><span class="identifier">boost_system</span></code> libraries. 36 </p> 37<p> 38 If you want to load a library, just construct <code class="computeroutput"><a class="link" href="../boost/dll/shared_library.html" title="Class shared_library">boost::dll::shared_library</a></code> 39 class with a path to the library as a parameter: 40</p> 41<pre class="programlisting"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">dll</span><span class="special">::</span><span class="identifier">shared_library</span> <span class="identifier">lib</span><span class="special">(</span><span class="string">"/test/boost/application/libtest_library.so"</span><span class="special">);</span> 42</pre> 43<p> 44 Now you can easily import symbols from that library using the <code class="computeroutput"><span class="identifier">get</span></code> and <code class="computeroutput"><span class="identifier">get_alias</span></code> 45 member functions: 46</p> 47<pre class="programlisting"><span class="keyword">int</span> <span class="identifier">plugin_constant</span> <span class="special">=</span> <span class="identifier">lib</span><span class="special">.</span><span class="identifier">get</span><span class="special"><</span><span class="keyword">const</span> <span class="keyword">int</span><span class="special">>(</span><span class="string">"integer_variable"</span><span class="special">);</span> 48<span class="identifier">boost</span><span class="special">::</span><span class="identifier">function</span><span class="special"><</span><span class="keyword">int</span><span class="special">()></span> <span class="identifier">f</span> <span class="special">=</span> <span class="identifier">lib</span><span class="special">.</span><span class="identifier">get</span><span class="special"><</span><span class="keyword">int</span><span class="special">()>(</span><span class="string">"function_returning_int"</span><span class="special">);</span> 49<span class="keyword">int</span><span class="special">&</span> <span class="identifier">i</span> <span class="special">=</span> <span class="identifier">lib</span><span class="special">.</span><span class="identifier">get_alias</span><span class="special"><</span><span class="keyword">int</span><span class="special">>(</span><span class="string">"alias_to_int_variable"</span><span class="special">);</span> 50</pre> 51<p> 52 In case of <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">dll</span><span class="special">::</span><span class="identifier">shared_library</span></code> 53 it is safe to use imported symbols only until <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">dll</span><span class="special">::</span><span class="identifier">shared_library</span></code> instance is not destroyed. 54 </p> 55<p> 56 Query libraries using <code class="computeroutput"><a class="link" href="../boost/dll/library_info.html" title="Class library_info">boost::dll::library_info</a></code> 57 and get symbol infos using <code class="computeroutput"><a class="link" href="../boost/dll/symbol_location.html" title="Function symbol_location">boost::dll::symbol_location</a></code>, 58 <code class="computeroutput"><a class="link" href="../boost/dll/this_line_location.html" title="Function this_line_location">boost::dll::this_line_location</a></code> 59 and <code class="computeroutput"><a class="link" href="../boost/dll/program_location.html" title="Function program_location">boost::dll::program_location</a></code>. 60 </p> 61<p> 62 For importing a single function or variable you may use a following one liners: 63 </p> 64<p> 65</p> 66<pre class="programlisting"><span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">;</span> 67 68<span class="comment">// `extern "C"` - specifies C linkage: forces the compiler to export function/variable by a pretty (unmangled) C name.</span> 69<span class="preprocessor">#define</span> <span class="identifier">API</span> <span class="keyword">extern</span> <span class="string">"C"</span> <span class="identifier">BOOST_SYMBOL_EXPORT</span> 70</pre> 71<p> 72 </p> 73<div class="informaltable"> 74<a name="boost_dll.getting_started.starting"></a><table class="table"> 75<colgroup> 76<col> 77<col> 78<col> 79</colgroup> 80<thead><tr> 81<th> 82 <p> 83 Import (code that uses DLL/DSL): 84 </p> 85 </th> 86<th> 87 <p> 88 Export (DLL/DSL sources): 89 </p> 90 </th> 91<th> 92 <p> 93 Functions description: 94 </p> 95 </th> 96</tr></thead> 97<tbody> 98<tr> 99<td> 100 <p> 101</p> 102<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="comment">// Importing function.</span> 103<span class="keyword">auto</span> <span class="identifier">cpp11_func</span> <span class="special">=</span> <span class="identifier">dll</span><span class="special">::</span><span class="identifier">import</span><span class="special"><</span><span class="keyword">int</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">&&)>(</span> 104 <span class="identifier">path_to_shared_library</span><span class="special">,</span> <span class="string">"i_am_a_cpp11_function"</span> 105 <span class="special">);</span> 106</pre> 107<p> 108 </p> 109 </td> 110<td> 111 <p> 112</p> 113<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="keyword">namespace</span> <span class="identifier">some_namespace</span> <span class="special">{</span> 114 <span class="identifier">API</span> <span class="keyword">int</span> <span class="identifier">i_am_a_cpp11_function</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">&&</span> <span class="identifier">param</span><span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span> 115<span class="comment">// ^-------------------- function name to use in dll::import<></span> 116<span class="special">}</span> 117</pre> 118<p> 119 </p> 120 </td> 121<td> 122 <p> 123 <code class="computeroutput"><a class="link" href="../boost/dll/import.html" title="Function import">import<T>(...)</a></code> 124 </p> 125 </td> 126</tr> 127<tr> 128<td> 129 <p> 130</p> 131<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="comment">// Importing variable.</span> 132<span class="identifier">shared_ptr</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">></span> <span class="identifier">cpp_var</span> <span class="special">=</span> <span class="identifier">dll</span><span class="special">::</span><span class="identifier">import</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">>(</span> 133 <span class="identifier">path_to_shared_library</span><span class="special">,</span> <span class="string">"cpp_variable_name"</span> 134 <span class="special">);</span> 135</pre> 136<p> 137 </p> 138 </td> 139<td> 140 <p> 141</p> 142<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="keyword">namespace</span> <span class="identifier">your_project_namespace</span> <span class="special">{</span> 143 <span class="identifier">API</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="identifier">cpp_variable_name</span><span class="special">;</span> 144<span class="special">}</span> 145</pre> 146<p> 147 </p> 148 </td> 149<td> 150 <p> 151 <code class="computeroutput"><a class="link" href="../boost/dll/import.html" title="Function import">import<T>(...)</a></code> 152 </p> 153 </td> 154</tr> 155<tr> 156<td> 157 <p> 158</p> 159<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="comment">// Importing function by alias name</span> 160<span class="keyword">auto</span> <span class="identifier">cpp_func</span> <span class="special">=</span> <span class="identifier">dll</span><span class="special">::</span><span class="identifier">import_alias</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">&)>(</span> 161 <span class="identifier">path_to_shared_library</span><span class="special">,</span> <span class="string">"pretty_name"</span> 162 <span class="special">);</span> 163</pre> 164<p> 165 </p> 166 </td> 167<td> 168 <p> 169</p> 170<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="keyword">namespace</span> <span class="identifier">some_namespace</span> <span class="special">{</span> 171 <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="identifier">i_am_function_with_ugly_name</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">&</span> <span class="identifier">param</span><span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span> 172<span class="special">}</span> 173 174<span class="comment">// When you have no control over function sources or wish to specify another name.</span> 175<span class="identifier">BOOST_DLL_ALIAS</span><span class="special">(</span><span class="identifier">some_namespace</span><span class="special">::</span><span class="identifier">i_am_function_with_ugly_name</span><span class="special">,</span> <span class="identifier">pretty_name</span><span class="special">)</span> 176</pre> 177<p> 178 </p> 179 </td> 180<td> 181 <p> 182 <code class="computeroutput"><a class="link" href="../boost/dll/import_alias.html" title="Function import_alias">import_alias<T>(...)</a></code> 183 </p> 184 <p> 185 <code class="computeroutput"><a class="link" href="../BOOST_DLL_ALIAS.html" title="Macro BOOST_DLL_ALIAS">BOOST_DLL_ALIAS</a></code> 186 </p> 187 </td> 188</tr> 189</tbody> 190</table> 191</div> 192<p> 193 It is safe to use imported variable or function because the variables returned 194 from <code class="computeroutput"><a class="link" href="../boost/dll/import.html" title="Function import">import<T>(...)</a></code> 195 and <code class="computeroutput"><a class="link" href="../boost/dll/import_alias.html" title="Function import_alias">import_alias<T>(...)</a></code> 196 functions internally hold a reference to the shared library. 197 </p> 198<p> 199 <code class="computeroutput">BOOST_SYMBOL_EXPORT</code> is just 200 a macro from Boost.Config that expands into the <code class="computeroutput"><span class="identifier">__declspec</span><span class="special">(</span><span class="identifier">dllexport</span><span class="special">)</span></code> or <code class="computeroutput"><span class="identifier">__attribute__</span><span class="special">((</span><span class="identifier">visibility</span><span class="special">(</span><span class="string">"default"</span><span class="special">)))</span></code>. You are free to use your own macro for 201 exports. 202 </p> 203<div class="note"><table border="0" summary="Note"> 204<tr> 205<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../doc/src/images/note.png"></td> 206<th align="left">Note</th> 207</tr> 208<tr><td align="left" valign="top"><p> 209 On Linux/POSIX/MacOS link with library "dl". "-fvisibility=hidden" 210 flag is also recommended. 211 </p></td></tr> 212</table></div> 213</div> 214<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 215<td align="left"></td> 216<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> 217 Distributed under the Boost Software License, Version 1.0. (See accompanying 218 file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) 219 </p> 220</div></td> 221</tr></table> 222<hr> 223<div class="spirit-nav"> 224<a accesskey="p" href="../boost_dll.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="tutorial.html"><img src="../../../doc/src/images/next.png" alt="Next"></a> 225</div> 226</body> 227</html> 228
