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<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Linking</title><meta name="generator" content="DocBook XSL-NS Stylesheets V1.78.1" /><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 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"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="manual.intro.using.linkage"></a>Linking</h2></div></div></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="manual.intro.using.linkage.freestanding"></a>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" style="list-style-type: disc; "><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" style="list-style-type: disc; "><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" style="list-style-type: disc; "><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"><div class="titlepage"><div><div><h3 class="title"><a id="manual.intro.using.linkage.dynamic"></a>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="_top">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="_top">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" style="list-style-type: disc; "><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" style="list-style-type: circle; "><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>
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 class="section"><div class="titlepage"><div><div><h3 class="title"><a id="manual.intro.using.linkage.experimental"></a>Experimental Library Extensions</h3></div></div></div><p>
GCC 5.3 includes an implementation of the Filesystem library defined
by the technical specification ISO/IEC TS 18822:2015. Because this is
an experimental library extension, not part of the C++ standard, it
is implemented in a separate library,
<code class="filename">libstdc++fs.a</code>, and there is
no shared library for it. To use the library you should include
<code class="filename"><experimental/filesystem></code>
and link with <code class="option">-lstdc++fs</code>. The library implementation
is incomplete on non-POSIX platforms, specifically Windows support is
rudimentary.
</p><p>
Due to the experimental nature of the Filesystem library the usual
guarantees about ABI stability and backwards compatibility do not apply
to it. There is no guarantee that the components in any
<code class="filename"><experimental/xxx></code>
header will remain compatible between different GCC releases.
</p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="using_namespaces.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="using.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="using_concurrency.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Namespaces </td><td width="20%" align="center"><a accesskey="h" href="../index.html">Home</a></td><td width="40%" align="right" valign="top"> Concurrency</td></tr></table></div></body></html>
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