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<html xmlns="http://www.w3.org/1999/xhtml"><head><title>Linking</title><meta name="generator" content="DocBook XSL-NS Stylesheets V1.75.2"/><meta name="keywords" content=" ISO C++ , library "/><link rel="home" href="../spine.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++0x <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" target="">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" target="">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 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 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="../spine.html">Home</a></td><td align="right" valign="top"> Concurrency</td></tr></table></div></body></html>
