📄 cast.html
字号:
<!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!-- but may not be published or retransmitted without explicit permission.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/cast.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 7.7</title><link href="decl.html" rev=precedes><link href="mallocnocast.html" rel=precedes><link href="index.html" rev=subdocument></head><body bgcolor="#ffffff"><a href="decl.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="mallocnocast.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 7.7</h1><p><font face=Helvetica size=8 color=blue><b>Q:</b></font>Why does some code carefully cast the values returned by <TT>malloc</TT>to the pointer type being allocated?</p><p><hr><p><font face=Helvetica size=8 color=blue><b>A:</b></font>Before ANSI/ISOStandardCintroducedthe <TT>void *</TT> generic pointer type,these casts weretypicallyrequiredto silencewarnings(and perhaps induce conversions)when assigningbetween incompatible pointer types.</p><p>Under ANSI/ISO Standard C,these casts areno longer necessary.It can also be arguedthattheyarenowto be discouraged;see question <a href="mallocnocast.html">7.7b</a>.Furthermore,well-defined,low-riskimplicit conversions(such as those which C has always performed betweeninteger and floating-point types)can be considered afeature.</p><p>On the other hand,some programmers prefer to make <em>every</em> conversion explicit,to record that they have considered each caseand decided exactly what should happen(see also question <a href="../style/voidcasts.html">17.5</a>).Also,the casts are typically seen in C codewhichfor one reason or anotheris intended to be compatible with C++,where explicit castsfrom<TT>void *</TT>are required.</p><p>(By the way, the language in sections 6.5 and 7.8.5 ofK&R2which suggests that the casts are requiredis ``overenthusiastic.'')</p><p>To some extent,whether you use these casts or not is a matter of style;seesection<a href="../style/index.html">17</a>.</p><p></p><p>Additional links:<a href="sd3.html" rel=subdocument>further explanation by Mark Brader</a></p><p>References:H&S Sec. 16.1 pp. 386-7<br></p><!-- aend --><p><hr><a href="decl.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="mallocnocast.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/cast.html by HTTrack Website Copier/3.x [XR&CO'2008], Sat, 14 Mar 2009 07:58:50 GMT --></html>⌨️ 快捷键说明
复制代码
Ctrl + C
搜索代码
Ctrl + F
全屏模式
F11
切换主题
Ctrl + Shift + D
显示快捷键
?
增大字号
Ctrl + =
减小字号
Ctrl + -