| <?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><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> |
