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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: How GNU Autotools uses M4</TITLE><META NAME="description" CONTENT="Autoconf, Automake, and Libtool: How GNU Autotools uses M4"><META NAME="keywords" CONTENT="Autoconf, Automake, and Libtool: How GNU Autotools uses M4"><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; } if (checkVersion()) { homeon = new Image(); homeon.src = "homeon.png"; homeoff = new Image(); homeoff.src = "home.png"; tocon = new Image(); tocon.src = "tocon.png"; tocoff = new Image(); tocoff.src = "toc.png"; indexon = new Image(); indexon.src = "indexon.png"; indexoff = new Image(); indexoff.src = "index.png"; helpon = new Image(); helpon.src = "helpon.png"; helpoff = new Image(); helpoff.src = "help.png"; backon = new Image(); backon.src = "backon.png"; backoff = new Image(); backoff.src = "back.png"; forwardon = new Image(); forwardon.src = "forwardon.png"; forwardoff = new Image(); forwardoff.src = "forward.png"; prevon = new Image(); prevon.src = "prevon.png"; prevoff = new Image(); prevoff.src = "prev.png"; nexton = new Image(); nexton.src = "nexton.png"; nextoff = new Image(); nextoff.src = "next.png"; upon = new Image(); upon.src = "upon.png"; upoff = new Image(); upoff.src = "up.png"; } function img_act(imgName) { if (checkVersion()) { imgOn = eval(imgName + "on.src"); document [imgName].src = imgOn; } } function img_inact(imgName) { if (checkVersion()) { imgOff = eval(imgName + "off.src"); document [imgName].src = imgOff; } }// --></SCRIPT></HEAD><BODY LANG="EN" BGCOLOR="#FFFFFF" TEXT="#000000" LINK="#6688AA" VLINK="#336688" ALINK="#808080"><A NAME="SEC193"></A><TABLE BORDER=0 CELLPADDING=0 CELLSPACING=10><TR VALIGN="TOP"><TD ALIGN="MIDDLE" WIDTH=50 BGCOLOR="#e6e6e6"><TABLE CELLPADDING=1 CELLSPACING=1 BORDER=0><TR VALIGN="TOP" ALIGN="LEFT"><TD VALIGN="MIDDLE" ALIGN="LEFT"><A HREF="autobook_192.html#SEC192" onMouseover="img_act('prev')" onMouseout="img_inact('prev')"><IMG SRC="prev.png" BORDER="0" ALT="Back: What does M4 do?" ALIGN="MIDDLE" NAME="prev"></A></TD></TR><TR VALIGN="TOP" ALIGN="LEFT"><TD VALIGN="MIDDLE" ALIGN="LEFT"><A HREF="autobook_194.html#SEC194" onMouseover="img_act('next')" onMouseout="img_inact('next')"><IMG SRC="next.png" BORDER="0" ALT="Forward: Fundamentals of M4 processing" ALIGN="MIDDLE" NAME="next"></A></TD></TR><TR VALIGN="TOP" ALIGN="LEFT"><TD VALIGN="MIDDLE" ALIGN="LEFT"> <TR VALIGN="TOP" ALIGN="LEFT"><TD VALIGN="MIDDLE" ALIGN="LEFT"><A HREF="autobook_194.html#SEC194" onMouseover="img_act('back')" onMouseout="img_inact('back')"><IMG SRC="back.png" BORDER="0" ALT="FastBack: Fundamentals of M4 processing" ALIGN="MIDDLE" NAME="back"></A></TD></TR><TR VALIGN="TOP" ALIGN="LEFT"><TD VALIGN="MIDDLE" ALIGN="LEFT"><A HREF="autobook_191.html#SEC191" onMouseover="img_act('up')" onMouseout="img_inact('up')"><IMG SRC="up.png" BORDER="0" ALT="Up: M4" ALIGN="MIDDLE" NAME="up"></A></TD></TR><TR VALIGN="TOP" ALIGN="LEFT"><TD VALIGN="MIDDLE" ALIGN="LEFT"><A HREF="autobook_208.html#SEC208" onMouseover="img_act('forward')" onMouseout="img_inact('forward')"><IMG SRC="forward.png" BORDER="0" ALT="FastForward: Writing Portable Bourne Shell" ALIGN="MIDDLE" NAME="forward"></A></TD></TR><TR VALIGN="TOP" ALIGN="LEFT"><TD VALIGN="MIDDLE" ALIGN="LEFT"><A HREF="autobook.html#SEC_Top" onMouseover="img_act('home')" onMouseout="img_inact('home')"><IMG SRC="home.png" BORDER="0" ALT="Top: Autoconf, Automake, and Libtool" ALIGN="MIDDLE" NAME="home"></A></TD></TR><TR VALIGN="TOP" ALIGN="LEFT"><TD VALIGN="MIDDLE" ALIGN="LEFT"><A HREF="autobook_toc.html#SEC_Contents" onMouseover="img_act('toc')" onMouseout="img_inact('toc')"><IMG SRC="toc.png" BORDER="0" ALT="Contents: Table of Contents" ALIGN="MIDDLE" NAME="toc"></A></TD></TR><TR VALIGN="TOP" ALIGN="LEFT"><TD VALIGN="MIDDLE" ALIGN="LEFT"><A HREF="autobook_285.html#SEC285" onMouseover="img_act('index')" onMouseout="img_inact('index')"><IMG SRC="index.png" BORDER="0" ALT="Index: Index" ALIGN="MIDDLE" NAME="index"></A></TD></TR><TR VALIGN="TOP" ALIGN="LEFT"><TD VALIGN="MIDDLE" ALIGN="LEFT"><A HREF="autobook_abt.html#SEC_About" onMouseover="img_act('help')" onMouseout="img_inact('help')"><IMG SRC="help.png" BORDER="0" ALT="About: About this document" ALIGN="MIDDLE" NAME="help"></A></TD></TR></TABLE></TD><TD ALIGN="LEFT"><H2> 21.2 How GNU Autotools uses M4 </H2><!--docid::SEC193::--><P>The GNU Autotools may all appear to use M4, but in actual fact,it all boils down to <CODE>autoconf</CODE> that invokes <CODE>m4</CODE> togenerate your <TT>`configure'</TT> script. You might be surprised to learnthat the shell code in <TT>`configure'</TT> does not use <CODE>m4</CODE> togenerate a final <TT>`Makefile'</TT> from <TT>`Makefile.in'</TT>. Instead, ituses <CODE>sed</CODE>, since that is more likely to be present on anend-user's system and thereby removes the dependency on <CODE>m4</CODE>.</P><P>Automake and Libtool include a lot of M4 input files. Theseare macros provided with each package that you can use directly (orindirectly) from your <TT>`configure.in'</TT>. These packages don't invoke<CODE>m4</CODE> themselves.</P><P>If you have already installed Autoconf on your system, you may haveencountered problems due to its strict M4 requirements.Autoconf <EM>demands</EM> to use GNU M4, mostly due to itexceeding limitations present in other M4 implementations. Asnoted by the Autoconf manual, this is not an onerous requirement, as itonly affects package maintainers who must regenerate <TT>`configure'</TT>scripts.</P><P>Autoconf's own <TT>`Makefile'</TT> will freeze some of the Autoconf<TT>`.m4'</TT> files containing macros as it builds Autoconf. When M4freezes an input file, it produces another file which represents theinternal state of the M4 processor so that the input file does not needto be parsed again. This helps to reduce the startup time for<CODE>autoconf</CODE>.</P><P><A NAME="Fundamentals of M4 processing"></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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