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<!DOCTYPE HTML PUBLIC "-//W3O//DTD W3 HTML 2.0//EN"><!-- This collection of hypertext pages is Copyright 1995-2005 by Steve Summit. --><!-- Content from the book "C Programming FAQs: Frequently Asked Questions" --><!-- (Addison-Wesley, 1995, ISBN 0-201-84519-9) is made available here by --><!-- permission of the author and the publisher as a service to the community. --><!-- It is intended to complement the use of the published text --><!-- and is protected by international copyright laws. --><!-- The on-line content may be accessed freely for personal use --><!-- but may not be published or retransmitted without explicit permission. --><!-- --><!-- this page built Sat Dec 24 21:47:46 2005 by faqproc version 2.7 --><!-- from source file cpp.sgml dated Wed Dec 21 13:52:14 2005 --><!-- corresponding to FAQ list version 4.0 --><html><!-- Mirrored from c-faq.com/cpp/ifexpr.html by HTTrack Website Copier/3.x [XR&CO'2008], Sat, 14 Mar 2009 07:58:54 GMT --><head><meta name=GENERATOR content="faqproc"><title>Question 10.13</title><link href="ifstrcmp.html" rev=precedes><link href="ifddef.html" rel=precedes><link href="index.html" rev=subdocument></head><body bgcolor="#ffffff"><a href="ifstrcmp.html" rev=precedes><img src="../images/buttonleft.gif" alt="prev"></a><a href="index.html" rev=subdocument><img src="../images/buttonup.gif" alt="up"></a><a href="ifddef.html" rel=precedes><img src="../images/buttonright.gif" alt="next"></a> <a href="../index-2.html"><img src="../images/buttontop.gif" alt="top/contents"></a><a href="../search.html"><img src="../images/buttonsrch.gif" alt="search"></a><hr><p><!-- qbegin --><h1>comp.lang.c FAQ list<font color=blue>·</font><!-- qtag -->Question 10.13</h1><p><font face=Helvetica size=8 color=blue><b>Q:</b></font>Does the <TT>sizeof</TT> operator work in preprocessor <TT>#if</TT> directives?</p><p><hr><p><font face=Helvetica size=8 color=blue><b>A:</b></font>No.Preprocessing happens during an earlierphase of compilation,before type names have been parsed.Insteadof <TT>sizeof</TT>,considerusing the predefined constants in ANSI's <TT><limits.h></TT>,if applicable,orperhapsa ``configure'' script.(Better yet,try to write code which is inherently insensitive to type sizes;see alsoquestions <a href="../decl/inttypes.html">1.1</a> and <a href="../decl/int16.html">1.3</a>.)</p><p>Additional links:<a href="ifsizeof.ct.html">nice explanation by Chris Torek</a></p><p>References:ISO Sec. 5.1.1.2, Sec. 6.8.1<br>H&S Sec. 7.11.1 p. 225<br></p><!-- aend --><p><hr><a href="ifstrcmp.html" rev=precedes><img src="../images/buttonleft.gif" alt="prev"></a><a href="index.html" rev=subdocument><img src="../images/buttonup.gif" alt="up"></a><a href="ifddef.html" rel=precedes><img src="../images/buttonright.gif" alt="next"></a> <a href="../questions.html"><img src="../images/buttontop.gif" alt="contents"></a><a href="../search.html"><img src="../images/buttonsrch.gif" alt="search"></a><br><!-- lastfooter --><a href="../about.html">about this FAQ list</a> <a href="../eskimo.html">about eskimo</a> <a href="../search.html">search</a> <a href="../feedback.html">feedback</a> <a href="copyright.html">copyright</a><p>Hosted by<a href="http://www.eskimo.com/"><img src="../../www.eskimo.com/img/link/eskitiny.gif" alt="Eskimo North"></a></body><!-- Mirrored from c-faq.com/cpp/ifexpr.html by HTTrack Website Copier/3.x [XR&CO'2008], Sat, 14 Mar 2009 07:58:54 GMT --></html>⌨️ 快捷键说明
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