1<?xml version="1.0" encoding="UTF-8" standalone="no"?> 2<!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> 3 Or as close as it gets: freestanding. This is a minimal 4 configuration, with only partial support for the standard 5 library. Assume only the following header files can be used: 6 </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p> 7 <code class="filename">cstdarg</code> 8 </p></li><li class="listitem"><p> 9 <code class="filename">cstddef</code> 10 </p></li><li class="listitem"><p> 11 <code class="filename">cstdlib</code> 12 </p></li><li class="listitem"><p> 13 <code class="filename">exception</code> 14 </p></li><li class="listitem"><p> 15 <code class="filename">limits</code> 16 </p></li><li class="listitem"><p> 17 <code class="filename">new</code> 18 </p></li><li class="listitem"><p> 19 <code class="filename">exception</code> 20 </p></li><li class="listitem"><p> 21 <code class="filename">typeinfo</code> 22 </p></li></ul></div><p> 23 In addition, throw in 24 </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p> 25 <code class="filename">cxxabi.h</code>. 26 </p></li></ul></div><p> 27 In the 28 C++11 <a class="link" href="using.html#manual.intro.using.flags" title="Command Options">dialect</a> add 29 </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p> 30 <code class="filename">initializer_list</code> 31 </p></li><li class="listitem"><p> 32 <code class="filename">type_traits</code> 33 </p></li></ul></div><p> There exists a library that offers runtime support for 34 just these headers, and it is called 35 <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: 36 </p><p> 37 <span class="command"><strong>gcc foo.cc -lsupc++</strong></span> 38 </p><p> 39 No attempt is made to verify that only the minimal subset 40 identified above is actually used at compile time. Violations 41 are diagnosed as undefined symbols at link time. 42 </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> 43 If the only library built is the static library 44 (<code class="filename">libstdc++.a</code>), or if 45 specifying static linking, this section is can be skipped. But 46 if building or using a shared library 47 (<code class="filename">libstdc++.so</code>), then 48 additional location information will need to be provided. 49 </p><p> 50 But how? 51 </p><p> 52A quick read of the relevant part of the GCC 53 manual, <a class="link" href="http://gcc.gnu.org/onlinedocs/gcc/Invoking-G_002b_002b.html#Invoking-G_002b_002b" target="_top">Compiling 54 C++ Programs</a>, specifies linking against a C++ 55 library. More details from the 56 GCC <a class="link" href="http://gcc.gnu.org/faq.html#rpath" target="_top">FAQ</a>, 57 which states <span class="emphasis"><em>GCC does not, by default, specify a 58 location so that the dynamic linker can find dynamic libraries at 59 runtime.</em></span> 60 </p><p> 61 Users will have to provide this information. 62 </p><p> 63 Methods vary for different platforms and different styles, and 64 are printed to the screen during installation. To summarize: 65 </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p> 66 At runtime set <code class="literal">LD_LIBRARY_PATH</code> in your 67 environment correctly, so that the shared library for 68 libstdc++ can be found and loaded. Be certain that you 69 understand all of the other implications and behavior 70 of <code class="literal">LD_LIBRARY_PATH</code> first. 71 </p></li><li class="listitem"><p> 72 Compile the path to find the library at runtime into the 73 program. This can be done by passing certain options to 74 <span class="command"><strong>g++</strong></span>, which will in turn pass them on to 75 the linker. The exact format of the options is dependent on 76 which linker you use: 77 </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p> 78 GNU ld (default on GNU/Linux): 79 <code class="literal">-Wl,-rpath,</code><code class="filename">destdir/lib</code> 80 </p></li><li class="listitem"><p> 81 Solaris ld: 82 <code class="literal">-Wl,-R</code><code class="filename">destdir/lib</code> 83 </p></li></ul></div></li><li class="listitem"><p> 84 Some linkers allow you to specify the path to the library by 85 setting <code class="literal">LD_RUN_PATH</code> in your environment 86 when linking. 87 </p></li><li class="listitem"><p> 88 On some platforms the system administrator can configure the 89 dynamic linker to always look for libraries in 90 <code class="filename">destdir/lib</code>, for example 91 by using the <span class="command"><strong>ldconfig</strong></span> utility on GNU/Linux 92 or the <span class="command"><strong>crle</strong></span> utility on Solaris. This is a 93 system-wide change which can make the system unusable so if you 94 are unsure then use one of the other methods described above. 95 </p></li></ul></div><p> 96 Use the <span class="command"><strong>ldd</strong></span> utility on the linked executable 97 to show 98 which <code class="filename">libstdc++.so</code> 99 library the system will get at runtime. 100 </p><p> 101 A <code class="filename">libstdc++.la</code> file is 102 also installed, for use with Libtool. If you use Libtool to 103 create your executables, these details are taken care of for 104 you. 105 </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> 106 GCC 5.3 includes an implementation of the Filesystem library defined 107 by the technical specification ISO/IEC TS 18822:2015. Because this is 108 an experimental library extension, not part of the C++ standard, it 109 is implemented in a separate library, 110 <code class="filename">libstdc++fs.a</code>, and there is 111 no shared library for it. To use the library you should include 112 <code class="filename"><experimental/filesystem></code> 113 and link with <code class="option">-lstdc++fs</code>. The library implementation 114 is incomplete on non-POSIX platforms, specifically Windows support is 115 rudimentary. 116 </p><p> 117 Due to the experimental nature of the Filesystem library the usual 118 guarantees about ABI stability and backwards compatibility do not apply 119 to it. There is no guarantee that the components in any 120 <code class="filename"><experimental/xxx></code> 121 header will remain compatible between different GCC releases. 122 </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>