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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: Creating Shared Libraries with libtool</TITLE><META NAME="description" CONTENT="Autoconf, Automake, and Libtool: Creating Shared Libraries with libtool"><META NAME="keywords" CONTENT="Autoconf, Automake, and Libtool: Creating Shared Libraries with libtool"><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; 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Since Libtool is intended to abstract away the details oflibrary building, it doesn't matter whether Libtool is building a sharedlibrary or a static archive. Of course, Libtool will always try tobuild a shared library by default on the platforms to which it has beenported (see section <A HREF="autobook_275.html#SEC275">B. PLATFORMS</A>), but will equally fall back to building astatic archive if the host architecture does not support sharedlibraries, or if the project developer deliberately configures Libtoolto always build static archives only. These libraries are more properlycalled `<EM>Libtool libraries</EM>'; the underlying native library willusually be a shared library, except as described above.</P><P>To create a Libtool library on my HP-UX host, or indeed anywhereelse that <CODE>libtool</CODE> works, run the following commands:</P><P><TABLE><tr><td> </td><td class=smallexample><FONT SIZE=-1><pre>$ rm hello.o libhello.a$ libtool gcc -c hello.cmkdir .libsgcc -c -fPIC -DPIC hello.c -o .libs/hello.logcc -c hello.c -o hello.o >/dev/null 2>&1mv -f .libs/hello.lo hello.lo$ lshello.c hello.lo hello.o$ libtool gcc -rpath /usr/local/lib -o libhello.la hello.lorm -fr .libs/libhello.la .libs/libhello.* .libs/libhello.*/opt/gcc-lib/hp821/2.7.0/ld -b +h libhello.sl.0 +b /usr/local/lib \-o .libs/libhello.sl.0.0 hello.lo(cd .libs && rm -f libhello.sl.0 && ln -s libhello.sl.0.0 libhello.sl.0)(cd .libs && rm -f libhello.sl && ln -s libhello.sl.0.0 libhello.sl)ar cru .libs/libhello.a hello.oranlib .libs/libhello.acreating libhello.la(cd .libs && rm -f libhello.la && ln -s ../libhello.la libhello.la)$ lshello.c hello.lo hello.o libhello.la</FONT></pre></td></tr></table></P><P><A NAME="IDX10"></A>This example illustrates several features of <CODE>libtool</CODE>. Comparethe command line syntax with the previous example (see section <A HREF="autobook_70.html#SEC70">10.2 The Libtool Library</A>). They are both very similar. Notice, however, that whencompiling the <TT>`hello.c'</TT> source file, <CODE>libtool</CODE> creates<EM>two</EM> objects. The first, <TT>`hello.lo'</TT>, is the <EM>Libtoolobject</EM> which we use for Libtool libraries, and the second,<TT>`hello.o'</TT> is a standard object. On HP-UX, <CODE>libtool</CODE>knows that Libtool objects should be compiled with <EM>positionindependent code</EM>, hence the extra switches when creating the firstobject.<BLOCKQUOTE>When you run <CODE>libtool</CODE> from the command line, you must alsospecify a compiler for it to call. Similarly when you create a<CODE>libtool</CODE> script with <CODE>ltconfig</CODE>, a compiler is chosenand interrogated to discover what characteristics it has.See section <A HREF="autobook_69.html#SEC69">10.1 Creating <CODE>libtool</CODE></A>.<P>Prior to release 1.4 of Libtool, <CODE>ltconfig</CODE> probed the buildmachine for a suitable compiler, by searching first for <CODE>gcc</CODE>and then <CODE>cc</CODE>. The functionality of <CODE>ltconfig</CODE> is beingmigrated into the <SAMP>`AC_PROG_LIBTOOL'</SAMP> macro, such that there will beno <CODE>ltconfig</CODE> script in Libtool release 1.5. The currentrelease is part way between the two. In all cases, you can specify aparticular compiler by setting the <SAMP>`CC'</SAMP> environment variable.</P><P>It is important to continue to use the same compiler when you run<CODE>libtool</CODE> as the compiler that was used when you created the<CODE>libtool</CODE> script. If you create the script with <SAMP>`CC'</SAMP> setto <CODE>gcc</CODE>, and subsequently try to compile using, say:</P><P><TABLE><tr><td> </td><td class=smallexample><FONT SIZE=-1><pre>$ libtool c89 -rpath /usr/local/lib -c hello.c</FONT></pre></td></tr></table></P><P><CODE>libtool</CODE> will try to call <CODE>c89</CODE> using the options itdiscovered for <CODE>gcc</CODE>. Needless to say, that doesn't work!</BLOCKQUOTE><P>The link command specifies a Libtool library target, <TT>`libhello.la'</TT>,compiled from a single Libtool object, <TT>`hello.lo'</TT>. Even so,<CODE>libtool</CODE> knows how to build both static and shared archives onHP-UX -- underneath the <CODE>libtool</CODE> abstraction both arecreated. <CODE>libtool</CODE> also understands the particulars of librarylinking on HP-UX: the static archive, <TT>`libhello.a'</TT>, is<I>blessed</I>; the system (and compiler) dependent compiler and linkerflags, versioning scheme and <CODE>.sl</CODE> extension are utilised for theshared archive, <TT>`libhello.sl'</TT>. On another host, all of thesedetails may be completely different, yet with exactly the sameinvocation, <CODE>libtool</CODE> will call the native tools with theappropriate options to achieve the same result. Try it on your ownmachines to see any differences.</P><P>It is the <SAMP>`-rpath'</SAMP> switch that tells <CODE>libtool</CODE> that youwant to build a Libtool library (with both the shared and staticcomponents where possible). If you omit the <SAMP>`-rpath'</SAMP> switch,<CODE>libtool</CODE> will build a convenience library instead,see <A HREF="autobook_74.html#SEC74">Creating convenience Libraries</A>. The <SAMP>`-rpath'</SAMP> switch is doublyimportant, because it tells <CODE>libtool</CODE> that you intend to install<TT>`libhello.la'</TT> in <TT>`/usr/local/lib'</TT>. This allows<CODE>libtool</CODE> to finalize the library correctly after installationon the architectures that need it, see <A HREF="autobook_80.html#SEC80">10.6 Installing a Library</A>.</P><P>Finally, notice that only the Libtool library, <TT>`libhello.la'</TT>,is visible after a successful link. The various files which form thelocal implementation details of the Libtool library are in a hiddensubdirectory, but in order for the abstraction to work cleanly youshouldn't need to worry about these too much.</P><P><A NAME="Creating Static Libraries with libtool"></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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