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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!-- but may not be published or retransmitted without explicit permission.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 varargs.sgml dated Sun Nov 25 08:09:42 2001 --><!-- corresponding to FAQ list version 4.0 --><html><!-- Mirrored from c-faq.com/varargs/proto2.html by HTTrack Website Copier/3.x [XR&CO'2008], Sat, 14 Mar 2009 07:59:00 GMT --><head><meta name=GENERATOR content="faqproc"><title>Question 15.3</title><link href="promos.html" rev=precedes><link href="varargs1.html" rel=precedes><link href="index.html" rev=subdocument></head><body bgcolor="#ffffff"><a href="promos.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="varargs1.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 15.3</h1><p><font face=Helvetica size=8 color=blue><b>Q:</b></font>I had a frustrating problem which turned out to be caused by the line<pre> printf("%d", n);</pre>where <TT>n</TT> was actually a <TT>long int</TT>.I thought that ANSI function prototypeswere supposed to guard against argument type mismatches like this.</p><p><hr><p><font face=Helvetica size=8 color=blue><b>A:</b></font>Whena functionacceptsa variable number of arguments,itsprototype does not(and cannot)provide any informationabout the number and types ofthosevariable arguments.Therefore,the usual protections do <em>not</em> applyin the variable-length part of variable-length argument lists:the compiler cannotperform implicit conversions or(in general)warn about mismatches.The programmer must make sure that arguments match,or must manually insert explicit casts.</p><p>In the case of <TT>printf</TT>-like functions,some compilers(including <TT>gcc</TT>)and some versions of <TT>lint</TT>are able to check the actual arguments against the format string,as long as the format string isan immediatestring literal.</p><p>See also questions<a href="../null/null2.html">5.2</a>,<a href="../ansi/argpromos.html">11.3</a>,<a href="../stdio/scanfvsprintf.html">12.9</a>,and<a href="promos.html">15.2</a>.</p><!-- aend --><p><hr><a href="promos.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="varargs1.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/varargs/proto2.html by HTTrack Website Copier/3.x [XR&CO'2008], Sat, 14 Mar 2009 07:59:00 GMT --></html>⌨️ 快捷键说明
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