libstdc++-v3/doc/html/manual/using_dynamic_or_shared.html

   1 <html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>Linking</title><meta name="generator" content="DocBook XSL-NS Stylesheets V1.76.1"><meta name="keywords" content="
   2       ISO C++
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   4       library
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   6       ISO C++
   7     ,
   8       runtime
   9     ,
  10       library
  11     "><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 bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Linking</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="using_namespaces.html">Prev</a> </td><th width="60%" align="center">Chapter 3. Using</th><td width="20%" 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" style="clear: both"><a name="manual.intro.using.linkage"></a>Linking</h2></div></div></div><div class="section" title="Almost Nothing"><div class="titlepage"><div><div><h3 class="title"><a name="manual.intro.using.linkage.freestanding"></a>Almost Nothing</h3></div></div></div><p>
  12         Or as close as it gets: freestanding. This is a minimal
  13         configuration, with only partial support for the standard
  14         library. Assume only the following header files can be used:
  15       </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>
  16             <code class="filename">cstdarg</code>
  17           </p></li><li class="listitem"><p>
  18           <code class="filename">cstddef</code>
  19           </p></li><li class="listitem"><p>
  20           <code class="filename">cstdlib</code>
  21           </p></li><li class="listitem"><p>
  22           <code class="filename">exception</code>
  23           </p></li><li class="listitem"><p>
  24           <code class="filename">limits</code>
  25           </p></li><li class="listitem"><p>
  26           <code class="filename">new</code>
  27           </p></li><li class="listitem"><p>
  28           <code class="filename">exception</code>
  29           </p></li><li class="listitem"><p>
  30           <code class="filename">typeinfo</code>
  31           </p></li></ul></div><p>
  32         In addition, throw in
  33       </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>
  34           <code class="filename">cxxabi.h</code>.
  35           </p></li></ul></div><p>
  36         In the
  37         C++11 <a class="link" href="using.html#manual.intro.using.flags" title="Command Options">dialect</a> add
  38       </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>
  39           <code class="filename">initializer_list</code>
  40           </p></li><li class="listitem"><p>
  41           <code class="filename">type_traits</code>
  42           </p></li></ul></div><p> There exists a library that offers runtime support for
  43         just these headers, and it is called
  44         <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:
  45       </p><p>
  46         <span class="command"><strong>gcc foo.cc -lsupc++</strong></span>
  47       </p><p>
  48         No attempt is made to verify that only the minimal subset
  49         identified above is actually used at compile time. Violations
  50         are diagnosed as undefined symbols at link time.
  51       </p></div><div class="section" title="Finding Dynamic or Shared Libraries"><div class="titlepage"><div><div><h3 class="title"><a name="manual.intro.using.linkage.dynamic"></a>Finding Dynamic or Shared Libraries</h3></div></div></div><p>
  52       If the only library built is the static library
  53       (<code class="filename">libstdc++.a</code>), or if
  54       specifying static linking, this section is can be skipped.  But
  55       if building or using a shared library
  56       (<code class="filename">libstdc++.so</code>), then
  57       additional location information will need to be provided.
  58     </p><p>
  59       But how?
  60     </p><p>
  61 A quick read of the relevant part of the GCC
  62       manual, <a class="link" href="http://gcc.gnu.org/onlinedocs/gcc/Invoking-G_002b_002b.html#Invoking-G_002b_002b" target="_top">Compiling
  63       C++ Programs</a>, specifies linking against a C++
  64       library. More details from the
  65       GCC <a class="link" href="http://gcc.gnu.org/faq.html#rpath" target="_top">FAQ</a>,
  66       which states <span class="emphasis"><em>GCC does not, by default, specify a
  67       location so that the dynamic linker can find dynamic libraries at
  68       runtime.</em></span>
  69     </p><p>
  70       Users will have to provide this information.
  71     </p><p>
  72       Methods vary for different platforms and different styles, and
  73       are printed to the screen during installation. To summarize:
  74     </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>
  75           At runtime set <code class="literal">LD_LIBRARY_PATH</code> in your
  76           environment correctly, so that the shared library for
  77           libstdc++ can be found and loaded.  Be certain that you
  78           understand all of the other implications and behavior
  79           of <code class="literal">LD_LIBRARY_PATH</code> first.
  80         </p></li><li class="listitem"><p>
  81           Compile the path to find the library at runtime into the
  82           program.  This can be done by passing certain options to
  83           <span class="command"><strong>g++</strong></span>, which will in turn pass them on to
  84           the linker.  The exact format of the options is dependent on
  85           which linker you use:
  86         </p><div class="itemizedlist"><ul class="itemizedlist" type="circle"><li class="listitem"><p>
  87               GNU ld (default on GNU/Linux):
  88               <code class="literal">-Wl,-rpath,</code><code class="filename">destdir/lib</code>
  89             </p></li><li class="listitem"><p>
  90             Solaris ld:
  91             <code class="literal">-Wl,-R</code><code class="filename">destdir/lib</code>
  92           </p></li></ul></div></li><li class="listitem"><p>
  93           Some linkers allow you to specify the path to the library by
  94           setting <code class="literal">LD_RUN_PATH</code> in your environment
  95           when linking.
  96         </p></li><li class="listitem"><p>
  97           On some platforms the system administrator can configure the
  98           dynamic linker to always look for libraries in
  99           <code class="filename">destdir/lib</code>, for example
 100           by using the <span class="command"><strong>ldconfig</strong></span> utility on GNU/Linux
 101           or the <span class="command"><strong>crle</strong></span> utility on Solaris. This is a
 102           system-wide change which can make the system unusable so if you
 103           are unsure then use one of the other methods described above.
 104         </p></li></ul></div><p>
 105       Use the <span class="command"><strong>ldd</strong></span> utility on the linked executable
 106       to show
 107       which <code class="filename">libstdc++.so</code>
 108       library the system will get at runtime.
 109     </p><p>
 110       A <code class="filename">libstdc++.la</code> file is
 111       also installed, for use with Libtool.  If you use Libtool to
 112       create your executables, these details are taken care of for
 113       you.
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