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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: Dynamic Modules</TITLE><META NAME="description" CONTENT="Autoconf, Automake, and Libtool: Dynamic Modules"><META NAME="keywords" CONTENT="Autoconf, Automake, and Libtool: Dynamic Modules"><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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For the rest of this chapter I will concentrate onthe conventions used when compiling dynamic modules with GCC onGNU/Linux, which although peculiar to this particular combinationof compiler and host architecture, are typical of the sorts ofconventions you would need to observe on other architectures or witha different compiler. </P><P>With GCC on GNU/Linux, you must compile each of the sourcefiles with <SAMP>`-fPIC'</SAMP><A NAME="DOCF38" HREF="autobook_fot.html#FOOT38">(38)</A>, the resultingobjects must be linked into a loadable module with <CODE>gcc</CODE>'s<SAMP>`-shared'</SAMP> option:</P><P><TABLE width=100%><tr><td> </td><td class=example bgcolor=#6688aa><br><pre>$ gcc -fPIC -c foo.c$ gcc -fPIC -c bar.c$ gcc -shared -o baz.so foo.o bar.o</pre></td></tr></table></P><P>This is pretty similar to how you might go about linking a sharedlibrary, except that the <TT>`baz.so'</TT> module will never be linked witha <SAMP>`-lbaz'</SAMP> option, so the <SAMP>`lib'</SAMP> prefix isn't necessary. Infact, it would probably be confusing if you used the prefix.Similarly, there is no constraint to use any particular filenamesuffix, but it is sensible to use the target's native shared librarysuffix (GNU/Linux uses <SAMP>`.so'</SAMP>) to make it obvious that thecompiled file is some sort of shared object, and not a normalexecutable.</P><P>Apart from that, the only difference between a shared library built forlinking at compile-time and a dynamic module built for loading atrun-time is that the module must provide known <EM>entry points</EM> forthe main executable to call. That is, when writing code destined for adynamic module, you must provide functions or variables with known namesand semantics that the main executable can use to access thefunctionality of the module. This <EM>is</EM> different to the functionand variable names in a regular library, which are already known whenyou write the client code, since the libraries are always written<EM>before</EM> the code that uses them; a runtime module loading systemmust, by definition, be able to cope with modules that are written<EM>after</EM> the code that uses those modules.</P><P><A NAME="Module Access Functions"></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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