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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!-- but may not be published or retransmitted without explicit permission.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/crash.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 7.19</title><link href="efficiency.html" rev=precedes><link href="noscale.html" rel=precedes><link href="index.html" rev=subdocument></head><body bgcolor="#ffffff"><a href="efficiency.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="noscale.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 7.19</h1><p><font face=Helvetica size=8 color=blue><b>Q:</b></font>My program is crashing, apparently somewhere down inside<TT>malloc</TT>,but I can't see anything wrong with it.Is there a bug in <TT>malloc</TT>?</p><p><hr><p><font face=Helvetica size=8 color=blue><b>A:</b></font>It is unfortunately very easy to corrupt<TT>malloc</TT>'s internal data structures,and the resulting problems can bestubborn.The most common source of problems is writing more to a<TT>malloc</TT>'ed region than it was allocated to hold;a particularly common bug is to <TT>malloc(strlen(s))</TT>instead of <TT>strlen(s) + 1</TT>.<a href="morebugs.html" rel=subdocument>[footnote]</a>Other problems may involveusing pointers tomemory that has been freed,freeing pointers twice,freeing pointers notobtained from <TT>malloc</TT>,<TT>free</TT>ing null pointers,allocating 0-sized objects(see question <a href="../ansi/malloc0.html">11.26</a>),or trying to <TT>realloc</TT> a null pointer(see question<a href="reallocnull.html">7.30</a>).(The last three--<TT>free</TT>ing null pointers,allocating 0-sized objects,and<TT>realloc</TT>ing a null pointer--are sanctioned by the Standard,thougholder implementations often have problems.)Consequences ofany of these errorscan show uplong after the actual mistakeandin unrelated sections of code,making diagnosis of the problem quite difficult.</p><p>Most implementations of <TT>malloc</TT> are particularly vulnerableto these problems because they store crucialpieces ofinternalinformation directly adjacent to the blocks of memorythey return,making themeasy prey for stray user pointers.</p><p>See also questions<a href="sizetlong.html">7.15</a>,<a href="freesize.html">7.26</a>,<a href="../strangeprob/segv.html">16.8</a>,and<a href="../resources/mallocdbg.html">18.2</a>.</p><!-- aend --><p><hr><a href="efficiency.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="noscale.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/crash.html by HTTrack Website Copier/3.x [XR&CO'2008], Sat, 14 Mar 2009 07:58:51 GMT --></html>⌨️ 快捷键说明
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