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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: Syntactic conventions</TITLE><META NAME="description" CONTENT="Autoconf, Automake, and Libtool: Syntactic conventions"><META NAME="keywords" CONTENT="Autoconf, Automake, and Libtool: Syntactic conventions"><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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These conventionsare designed to make your macros more robust, your code easier to readand, most importantly, improve your chances for getting things to workthe first time! A brief list of recommended conventions appears below:</P><P><UL><LI>Do not use the M4 built-in <CODE>changequote</CODE>. Any good macrowill already perform sufficient quoting.<P><LI>Never use the argument macros (e.g. <SAMP>`$1'</SAMP>) within shell comments anddnl remarks. If such a comment were to be placed within a macrodefinition, M4 will expand the argument macros leading to strangeresults. Instead, quote the argument number to prevent unwantedexpansion. For instance, you would use <SAMP>`$[1]'</SAMP> in the comment.<P><LI>Quote the M4 comment character, <SAMP>`#'</SAMP>. This can appear often inshell code fragments and can have undesirable effects if M4 ignores anyexpansions in the text between the <SAMP>`#'</SAMP> and the next newline.<P><LI>In general, macros invoked from <TT>`configure.in'</TT> should be placed oneper line. Many of the GNU Autotools macros conclude their definitions witha <CODE>dnl</CODE> to prevent unwanted whitespace from accumulating in<TT>`configure'</TT>.<P><LI>Many of the <CODE>AC_</CODE> macros, and others which emulate their goodbehavior, permit default values for unspecified arguments. It isconsidered good style to explicitly show your intention to use an emptyargument by using a pair of quotes, such as <CODE>[]</CODE>.<P><LI>Always quote the names of macros used within the definitions ofother macros.<P><LI>When writing new macros, generate a small <TT>`configure.in'</TT> thatuses (and abuses!) the macro--particularly with respect to quoting.Generate a <TT>`configure'</TT> script with <CODE>autoconf</CODE> and inspectthe results.</UL><P><A NAME="Debugging with M4"></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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