📄 refconst.html
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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!-- but may not be published or retransmitted without explicit permission.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 pointers.sgml dated Wed Dec 21 13:07:10 2005 --><!-- corresponding to FAQ list version 4.0 --><html><!-- Mirrored from c-faq.com/ptrs/refconst.html by HTTrack Website Copier/3.x [XR&CO'2008], Sat, 14 Mar 2009 07:58:47 GMT --><head><meta name=GENERATOR content="faqproc"><title>Question 4.10</title><link href="genericpp.html" rev=precedes><link href="passbyref.html" rel=precedes><link href="index.html" rev=subdocument></head><body bgcolor="#ffffff"><a href="genericpp.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="passbyref.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 4.10</h1><p><font face=Helvetica size=8 color=blue><b>Q:</b></font>I have a function<pre> extern int f(int *);</pre>which accepts a pointer to an <TT>int</TT>.How can I pass a constantby reference?A call like<pre> f(&5);</pre>doesn't seem to work.</p><p><hr><p><font face=Helvetica size=8 color=blue><b>A:</b></font>In C99, you can use a ``compound literal'':<pre> f((int[]){5});</pre></p><p>Prior to C99,you couldn'tdothisdirectly;you had todeclare a temporary variable,and then pass its address to the function:<pre> int five = 5; f(&five);</pre>In C, a function that accepts a pointer to a value(rather thansimplyacceptingthe value itself)probably intends to modify the pointed-to value,so it may be a bad idea to pass pointers to constants.<a href="fn17.html" rel=subdocument>[footnote]</a>Indeed,if <TT>f</TT> is in fact declared as accepting an <TT>int *</TT>,a diagnostic is required if you attempt to pass it a pointer to a <TT>const int</TT>.(<TT>f</TT> could be declared as accepting a<TT>const int *</TT> if it promises not to modify the pointed-to value.)</p><p>See also questions <a href="../struct/anonstruct.html">2.10</a>,<a href="passptrinit.html">4.8</a>,and<a href="../misc/multretval.html">20.1</a>.</p><!-- aend --><p><hr><a href="genericpp.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="passbyref.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/ptrs/refconst.html by HTTrack Website Copier/3.x [XR&CO'2008], Sat, 14 Mar 2009 07:58:47 GMT --></html>⌨️ 快捷键说明
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