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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
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<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>
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Or as close as it gets: freestanding. This is a minimal
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configuration, with only partial support for the standard
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library. Assume only the following header files can be used:
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</p><div class="itemizedlist"><ul class="itemizedlist"><li class="listitem"><p>
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<code class="filename">cstdarg</code>
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</p></li><li class="listitem"><p>
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<code class="filename">cstddef</code>
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</p></li><li class="listitem"><p>
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<code class="filename">cstdlib</code>
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</p></li><li class="listitem"><p>
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<code class="filename">exception</code>
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</p></li><li class="listitem"><p>
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<code class="filename">limits</code>
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</p></li><li class="listitem"><p>
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<code class="filename">new</code>
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</p></li><li class="listitem"><p>
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<code class="filename">exception</code>
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</p></li><li class="listitem"><p>
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<code class="filename">typeinfo</code>
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</p></li></ul></div><p>
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In addition, throw in
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</p><div class="itemizedlist"><ul class="itemizedlist"><li class="listitem"><p>
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<code class="filename">cxxabi.h</code>.
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</p></li></ul></div><p>
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In the
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C++11 <a class="link" href="using.html#manual.intro.using.flags" title="Command Options">dialect</a> add
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</p><div class="itemizedlist"><ul class="itemizedlist"><li class="listitem"><p>
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<code class="filename">initializer_list</code>
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</p></li><li class="listitem"><p>
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<code class="filename">type_traits</code>
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</p></li></ul></div><p> There exists a library that offers runtime support for
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just these headers, and it is called
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<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:
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</p><p>
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<span class="command"><strong>gcc foo.cc -lsupc++</strong></span>
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</p><p>
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No attempt is made to verify that only the minimal subset
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identified above is actually used at compile time. Violations
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are diagnosed as undefined symbols at link time.
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</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>
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If the only library built is the static library
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(<code class="filename">libstdc++.a</code>), or if
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specifying static linking, this section is can be skipped. But
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if building or using a shared library
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(<code class="filename">libstdc++.so</code>), then
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additional location information will need to be provided.
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</p><p>
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But how?
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</p><p>
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A quick read of the relevant part of the GCC
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manual, <a class="link" href="http://gcc.gnu.org/onlinedocs/gcc/Invoking-G_002b_002b.html#Invoking-G_002b_002b">Compiling
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C++ Programs</a>, specifies linking against a C++
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library. More details from the
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GCC <a class="link" href="http://gcc.gnu.org/faq.html#rpath">FAQ</a>,
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which states <span class="emphasis"><em>GCC does not, by default, specify a
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location so that the dynamic linker can find dynamic libraries at
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runtime.</em></span>
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</p><p>
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Users will have to provide this information.
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</p><p>
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Methods vary for different platforms and different styles, and
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are printed to the screen during installation. To summarize:
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</p><div class="itemizedlist"><ul class="itemizedlist"><li class="listitem"><p>
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At runtime set <code class="literal">LD_LIBRARY_PATH</code> in your
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environment correctly, so that the shared library for
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libstdc++ can be found and loaded. Be certain that you
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understand all of the other implications and behavior
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of <code class="literal">LD_LIBRARY_PATH</code> first.
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</p></li><li class="listitem"><p>
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Compile the path to find the library at runtime into the
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program. This can be done by passing certain options to
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<span class="command"><strong>g++</strong></span>, which will in turn pass them on to
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the linker. The exact format of the options is dependent on
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which linker you use:
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</p><div class="itemizedlist"><ul class="itemizedlist"><li class="listitem"><p>
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GNU ld (default on GNU/Linux):
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<code class="literal">-Wl,-rpath,</code><code class="filename">destdir/lib</code>
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</p></li><li class="listitem"><p>
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IRIX ld:
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<code class="literal">-Wl,-rpath,</code><code class="filename">destdir/lib</code>
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</p></li><li class="listitem"><p>
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Solaris ld:
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<code class="literal">-Wl,-R</code><code class="filename">destdir/lib</code>
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</p></li></ul></div></li><li class="listitem"><p>
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Some linkers allow you to specify the path to the library by
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setting <code class="literal">LD_RUN_PATH</code> in your environment
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when linking.
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</p></li><li class="listitem"><p>
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On some platforms the system administrator can configure the
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dynamic linker to always look for libraries in
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<code class="filename">destdir/lib</code>, for example
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by using the <span class="command"><strong>ldconfig</strong></span> utility on GNU/Linux
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or the <span class="command"><strong>crle</strong></span> utility on Solaris. This is a
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system-wide change which can make the system unusable so if you
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are unsure then use one of the other methods described above.
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</p></li></ul></div><p>
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Use the <span class="command"><strong>ldd</strong></span> utility on the linked executable
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to show
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which <code class="filename">libstdc++.so</code>
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library the system will get at runtime.
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</p><p>
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A <code class="filename">libstdc++.la</code> file is
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also installed, for use with Libtool. If you use Libtool to
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create your executables, these details are taken care of for
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you.
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</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>
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