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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!-- but may not be published or retransmitted without explicit permission.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/freeb4exit.html by HTTrack Website Copier/3.x [XR&CO'2008], Sat, 14 Mar 2009 07:58:51 GMT --><head><meta name=GENERATOR content="faqproc"><title>Question 7.24</title><link href="freeforall.html" rev=precedes><link href="freetoOS.html" rel=precedes><link href="index.html" rev=subdocument></head><body bgcolor="#ffffff"><a href="freeforall.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="freetoOS.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 7.24</h1><p><font face=Helvetica size=8 color=blue><b>Q:</b></font>Must I free allocated memory before the program exits?</p><p><hr><p><font face=Helvetica size=8 color=blue><b>A:</b></font>You shouldn't have to.A real operating systemdefinitively reclaimsall memoryand other resourceswhen a program exits;the systemcannot affordto havememory integritydependon the whims of random programs.(Strictly speaking,it is not even <TT>free</TT>'s jobto return memory to the operating system;see question <a href="freetoOS.html">7.25</a>.)Nevertheless, some personal computersare said not to reliably recover memoryunless it was freed before exiting,and all that can be inferred from the ANSI/ISO C Standardis that this is a ``quality of implementation issue.''</p><p>On the other hand,the C library <TT>free</TT> function rarely returns memory backto the operating system(see question <a href="freetoOS.html">7.25</a>),so calling <TT>free</TT> probably isn't the way to guaranteethat an exiting program's memory is recovered by the system, anyway.</p><p>In any case,it can be considered good practice to explicitly free allmemory--forexample,in case the program is ever rewrittento perform its main task more than once(perhaps under a Graphical User Interface).<a href="prleak.html" rel=subdocument>[footnote]</a>On the other hand,there are programs(such as interpreters)that don't know whatmemorythey're done with(i.e. what memory could be freed)until it's time to exit,and since all memory should be released at exit,it would be a needless,potentiallyexpensive, anderror-prone exercisefor the program to explicitly free all of it.</p><p>Additional links:<a href="freeb4exit2.html">further explanation</a></p><p>References:ISO Sec. 7.10.3.2<br></p><!-- aend --><p><hr><a href="freeforall.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="freetoOS.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/freeb4exit.html by HTTrack Website Copier/3.x [XR&CO'2008], Sat, 14 Mar 2009 07:58:52 GMT --></html>⌨️ 快捷键说明
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