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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!-- but may not be published or retransmitted without explicit permission.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/noscale.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 7.19b</title><link href="crash.html" rev=precedes><link href="useafterfree.html" rel=precedes><link href="index.html" rev=subdocument></head><body bgcolor="#ffffff"><a href="crash.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="useafterfree.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 7.19b</h1><p><font face=Helvetica size=8 color=blue><b>Q:</b></font>I'm dynamically allocating an array, like this:<pre> int *iarray = (int *)malloc(nints);</pre><TT>malloc</TT> isn't returning NULL,but the code isn't working.</p><p><hr><p><font face=Helvetica size=8 color=blue><b>A:</b></font><TT>malloc</TT>is a low-level, typeless allocator.It doesn't knowhow you're going to use the memory;all it does is to allocateas many <em>bytes</em> of memory as you ask it.Therefore(except when you're allocating arrays of <TT>char</TT>)you mustmultiply by the size of the elements in the array you're allocating:<pre> int *iarray = malloc(nints * sizeof(int));</pre>or<pre> int *iarray = malloc(nints * sizeof(*iarray));</pre>(The latter fragment can be more reliableif the type of <TT>iarray</TT> might change,since there's only one place to change it.Also, the casts have been removed;see question <a href="cast.html">7.7</a>.)Compare question <a href="../ptrs/explscale.html">4.4</a>,and see also question <a href="sizeofchar.html">7.8</a>.</p><!-- aend --><p><hr><a href="crash.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="useafterfree.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/noscale.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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