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<HTML><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><!-- Created on September, 12 2004 by texi2html 1.64 --><!-- Written by: Lionel Cons <Lionel.Cons@cern.ch> (original author) Karl Berry <karl@freefriends.org> Olaf Bachmann <obachman@mathematik.uni-kl.de> and many others.Maintained by: Olaf Bachmann <obachman@mathematik.uni-kl.de>Send bugs and suggestions to <texi2html@mathematik.uni-kl.de> --><HEAD><TITLE>Autoconf, Automake, and Libtool: libltdl Module Loader</TITLE><META NAME="description" CONTENT="Autoconf, Automake, and Libtool: libltdl Module Loader"><META NAME="keywords" CONTENT="Autoconf, Automake, and Libtool: libltdl Module Loader"><META NAME="resource-type" CONTENT="document"><META NAME="distribution" CONTENT="global"><META NAME="Generator" CONTENT="texi2html 1.64"><script language="Javascript"><!-- // Check the browser version. function checkVersion() { if (navigator.appVersion.charAt(0)>=3) return true; if (navigator.appVersion.charAt(0)>=4) return true; else return false; 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Itimplements the same API as the simple module loader in <A HREF="autobook_162.html#SEC162">17.4 A Simple GNU/Linux Module Loader</A>, and because of the way libltdlis written is able to load modules written for that loader, too. Theonly part of this code which is arguably more complex than theequivalent from the previous example loader, is that <CODE>lt_dlinit</CODE>and <CODE>lt_dlexit</CODE> must be called in the appropriate places. Incontrast, The module search path initialisation is much simplified thanks to another relative improvement in the libltdl API:</P><P><A NAME="IDX34"></A><DL><DT><U>Function:</U> int <B>lt_dlsetsearchpath</B> <I>(const char *<VAR>path</VAR>)</I><DD>This function takes a colon separated list of directories, whichwill be the first directories libltdl will search when trying tolocate a dynamic module.</DL></P><P>Another new API function is used to actually load the module:</P><P><A NAME="IDX35"></A><DL><DT><U>Function:</U> lt_dlhandle <B>lt_dlopenext</B> <I>(const char *<VAR>filename</VAR>)</I><DD>This function is used in precisely the same way as <CODE>lt_dlopen</CODE>.However, if the search for the named module by exact matchagainst <VAR>filename</VAR> fails, it will try again with a <SAMP>`.la'</SAMP> extension,and then the native shared library extension (<SAMP>`.sl'</SAMP> on HP-UX,for example).</DL></P><P>The advantage of using <CODE>lt_dlopenext</CODE> to load dynamic modules isthat it will work equally well when loading modules not compiled withLibtool. Also, by passing the module name parameter with no extension,this function allows module coders to manage without Libtool.</P><P><TABLE width=100%><tr><td> </td><td class=example bgcolor=#6688aa><br><pre></pre></td></tr></table></P><P>This file must be compiled with <CODE>libtool</CODE>, so that the dependentlibraries (<TT>`libdl.so'</TT> on my GNU/Linux machine) are handledcorrectly, and so that the dlpreopen support is compiled in correctly(see section <A HREF="autobook_173.html#SEC173">18.4 dlpreopen Loading</A>):</P><P><TABLE width=100%><tr><td> </td><td class=example bgcolor=#6688aa><br><pre>$ libtool --mode=link gcc -g -o ltdl-loader -dlopen self \-rpath /tmp/lib ltdl-loader.c -lltdlgcc -g -o ltdl-loader -Wl,--rpath,/tmp/lib ltdl-loader.c -lltdl -ldl</pre></td></tr></table></P><P>By using <EM>both</EM> of <CODE>lt_dlopenext</CODE> and<CODE>lt_dlsetsearchpath</CODE>, this module loader will make a valiantattempt at loading anything you pass to it -- including the module Iwrote for the simple GNU/Linux module loader earlier (see section <A HREF="autobook_163.html#SEC163">17.5 A Simple GNU/Linux Dynamic Module</A>). Here, you can see the new<CODE>ltdl-loader</CODE> loading and using the <TT>`simple-module'</TT> modulefrom <A HREF="autobook_163.html#SEC163">17.5 A Simple GNU/Linux Dynamic Module</A>:</P><P><TABLE width=100%><tr><td> </td><td class=example bgcolor=#6688aa><br><pre>$ ltdl-loader simple-module WorldHello, World! => 0</pre></td></tr></table></P><P><A NAME="libltdl Dependent Libraries"></A></TR></TABLE><BR> <FONT SIZE="-1">This document was generatedby <I>Gary V. Vaughan</I> on <I>September, 12 2004</I>using <A HREF="http://www.mathematik.uni-kl.de/~obachman/Texi2html"><I>texi2html</I></A></BODY></HTML>⌨️ 快捷键说明
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