<?xml version="1.0" encoding="UTF-8" standalone="no"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"><head><title>Linking</title><meta name="generator" content="DocBook XSL-NS Stylesheets V1.76.1"/><meta name="keywords" content=" ISO C++ , library "/><meta name="keywords" content=" ISO C++ , runtime , library "/><link rel="home" href="../index.html" title="The GNU C++ Library"/><link rel="up" href="using.html" title="Chapter 3. Using"/><link rel="prev" href="using_namespaces.html" title="Namespaces"/><link rel="next" href="using_concurrency.html" title="Concurrency"/></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Linking</th></tr><tr><td align="left"><a accesskey="p" href="using_namespaces.html">Prev</a> </td><th width="60%" align="center">Chapter 3. Using</th><td align="right"> <a accesskey="n" href="using_concurrency.html">Next</a></td></tr></table><hr/></div><div class="section" title="Linking"><div class="titlepage"><div><div><h2 class="title"><a id="manual.intro.using.linkage"/>Linking</h2></div></div></div><div class="section" title="Almost Nothing"><div class="titlepage"><div><div><h3 class="title"><a id="manual.intro.using.linkage.freestanding"/>Almost Nothing</h3></div></div></div><p> Or as close as it gets: freestanding. This is a minimal configuration, with only partial support for the standard library. Assume only the following header files can be used: </p><div class="itemizedlist"><ul class="itemizedlist"><li class="listitem"><p> <code class="filename">cstdarg</code> </p></li><li class="listitem"><p> <code class="filename">cstddef</code> </p></li><li class="listitem"><p> <code class="filename">cstdlib</code> </p></li><li class="listitem"><p> <code class="filename">exception</code> </p></li><li class="listitem"><p> <code class="filename">limits</code> </p></li><li class="listitem"><p> <code class="filename">new</code> </p></li><li class="listitem"><p> <code class="filename">exception</code> </p></li><li class="listitem"><p> <code class="filename">typeinfo</code> </p></li></ul></div><p> In addition, throw in </p><div class="itemizedlist"><ul class="itemizedlist"><li class="listitem"><p> <code class="filename">cxxabi.h</code>. </p></li></ul></div><p> In the C++11 <a class="link" href="using.html#manual.intro.using.flags" title="Command Options">dialect</a> add </p><div class="itemizedlist"><ul class="itemizedlist"><li class="listitem"><p> <code class="filename">initializer_list</code> </p></li><li class="listitem"><p> <code class="filename">type_traits</code> </p></li></ul></div><p> There exists a library that offers runtime support for just these headers, and it is called <code class="filename">libsupc++.a</code>. To use it, compile with <span class="command"><strong>gcc</strong></span> instead of <span class="command"><strong>g++</strong></span>, like so: </p><p> <span class="command"><strong>gcc foo.cc -lsupc++</strong></span> </p><p> No attempt is made to verify that only the minimal subset identified above is actually used at compile time. Violations are diagnosed as undefined symbols at link time. </p></div><div class="section" title="Finding Dynamic or Shared Libraries"><div class="titlepage"><div><div><h3 class="title"><a id="manual.intro.using.linkage.dynamic"/>Finding Dynamic or Shared Libraries</h3></div></div></div><p> If the only library built is the static library (<code class="filename">libstdc++.a</code>), or if specifying static linking, this section is can be skipped. But if building or using a shared library (<code class="filename">libstdc++.so</code>), then additional location information will need to be provided. </p><p> But how? </p><p> A quick read of the relevant part of the GCC manual, <a class="link" href="http://gcc.gnu.org/onlinedocs/gcc/Invoking-G_002b_002b.html#Invoking-G_002b_002b">Compiling C++ Programs</a>, specifies linking against a C++ library. More details from the GCC <a class="link" href="http://gcc.gnu.org/faq.html#rpath">FAQ</a>, which states <span class="emphasis"><em>GCC does not, by default, specify a location so that the dynamic linker can find dynamic libraries at runtime.</em></span> </p><p> Users will have to provide this information. </p><p> Methods vary for different platforms and different styles, and are printed to the screen during installation. To summarize: </p><div class="itemizedlist"><ul class="itemizedlist"><li class="listitem"><p> At runtime set <code class="literal">LD_LIBRARY_PATH</code> in your environment correctly, so that the shared library for libstdc++ can be found and loaded. Be certain that you understand all of the other implications and behavior of <code class="literal">LD_LIBRARY_PATH</code> first. </p></li><li class="listitem"><p> Compile the path to find the library at runtime into the program. This can be done by passing certain options to <span class="command"><strong>g++</strong></span>, which will in turn pass them on to the linker. The exact format of the options is dependent on which linker you use: </p><div class="itemizedlist"><ul class="itemizedlist"><li class="listitem"><p> GNU ld (default on GNU/Linux): <code class="literal">-Wl,-rpath,</code><code class="filename">destdir/lib</code> </p></li><li class="listitem"><p> IRIX ld: <code class="literal">-Wl,-rpath,</code><code class="filename">destdir/lib</code> </p></li><li class="listitem"><p> Solaris ld: <code class="literal">-Wl,-R</code><code class="filename">destdir/lib</code> </p></li></ul></div></li><li class="listitem"><p> Some linkers allow you to specify the path to the library by setting <code class="literal">LD_RUN_PATH</code> in your environment when linking. </p></li><li class="listitem"><p> On some platforms the system administrator can configure the dynamic linker to always look for libraries in <code class="filename">destdir/lib</code>, for example by using the <span class="command"><strong>ldconfig</strong></span> utility on GNU/Linux or the <span class="command"><strong>crle</strong></span> utility on Solaris. This is a system-wide change which can make the system unusable so if you are unsure then use one of the other methods described above. </p></li></ul></div><p> Use the <span class="command"><strong>ldd</strong></span> utility on the linked executable to show which <code class="filename">libstdc++.so</code> library the system will get at runtime. </p><p> A <code class="filename">libstdc++.la</code> file is also installed, for use with Libtool. If you use Libtool to create your executables, these details are taken care of for you. </p></div></div><div class="navfooter"><hr/><table width="100%" summary="Navigation footer"><tr><td align="left"><a accesskey="p" href="using_namespaces.html">Prev</a> </td><td align="center"><a accesskey="u" href="using.html">Up</a></td><td align="right"> <a accesskey="n" href="using_concurrency.html">Next</a></td></tr><tr><td align="left" valign="top">Namespaces </td><td align="center"><a accesskey="h" href="../index.html">Home</a></td><td align="right" valign="top"> Concurrency</td></tr></table></div></body></html>