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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!-- but may not be published or retransmitted without explicit permission.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 21:47:45 2005 by faqproc version 2.7 --><!-- from source file malloc.sgml dated Wed Dec 21 13:50:44 2005 --><!-- corresponding to FAQ list version 4.0 --><html><!-- Mirrored from c-faq.com/malloc/retaggr.html by HTTrack Website Copier/3.x [XR&CO'2008], Sat, 14 Mar 2009 07:58:50 GMT --><head><meta name=GENERATOR content="faqproc"><title>Question 7.5a</title><link href="linebfdur.html" rev=precedes><link href="retaggr2.html" rel=precedes><link href="index.html" rev=subdocument></head><body bgcolor="#ffffff"><a href="linebfdur.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="retaggr2.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 7.5a</h1><p><font face=Helvetica size=8 color=blue><b>Q:</b></font>I have a function that is supposed to return a string,but when it returns to its caller,the returned string is garbage.</p><p><hr><p><font face=Helvetica size=8 color=blue><b>A:</b></font>Whenever a function returns a pointer,makesure that the pointed-to memoryisproperlyallocated.For example,make sure you have <em>not</em> donesomething like<pre><br> #include <stdio.h><br> char *itoa(int n) { char retbuf[20]; /* WRONG */ sprintf(retbuf, "%d", n); return retbuf; /* WRONG */ }</pre>When a function returns,itsautomatic, localvariablesare discarded,so the returned pointer in this case is invalid(it points to an array that no longer exists).</p><p>One fixwould be to declare the return buffer as<pre> static char retbuf[20];</pre>This fix is imperfect,since a function using static data is not reentrant.Furthermore,successive calls to this version of <TT>itoa</TT> keep overwriting the same return buffer:the caller won't be ableto call it several timesand keepall thereturn values aroundsimultaneously.</p><p>See also questions<a href="retaggr2.html">7.5b</a>,<a href="../stdio/sprintfsize.html">12.21</a>,and<a href="../misc/multretval.html">20.1</a>.</p><p>References:ISO Sec. 6.1.2.4<br></p><!-- aend --><p><hr><a href="linebfdur.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="retaggr2.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/malloc/retaggr.html by HTTrack Website Copier/3.x [XR&CO'2008], Sat, 14 Mar 2009 07:58:50 GMT --></html>⌨️ 快捷键说明
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