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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!-- but may not be published or retransmitted without explicit permission.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/funccall.html by HTTrack Website Copier/3.x [XR&CO'2008], Sat, 14 Mar 2009 07:58:48 GMT --><head><meta name=GENERATOR content="faqproc"><title>Question 4.12</title><link href="passbyref.html" rev=precedes><link href="generic.html" rel=precedes><link href="index.html" rev=subdocument></head><body bgcolor="#ffffff"><a href="passbyref.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="generic.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 4.12</h1><p><font face=Helvetica size=8 color=blue><b>Q:</b></font>I've seen different syntax used for calling functions via pointers.What's the story?</p><p><hr><p><font face=Helvetica size=8 color=blue><b>A:</b></font>Originally, a pointer to a function had to be``turned into'' a ``real''function,with the <TT>*</TT> operator,before calling:<pre> int r, (*fp)(), func(); fp = func; r = (*fp)();</pre>The interpretation of thelast line is clear:<TT>fp</TT> is a pointer to function,so <TT>*fp</TT> is the function;append an argument list in parentheses(and extra parentheses around <TT>*fp</TT> to get the precedence right),and you've got a function call.</p><p>It can also be arguedthat functions are always called via pointers,andthat ``real'' functionnamesalwaysdecay implicitly into pointers(in expressions, as they do in initializations;see question <a href="../decl/ptrfuncinit.html">1.34</a>).This reasoningmeans that<pre> r = fp();</pre>is legal and works correctly,whether <TT>fp</TT> isthe name ofa function or a pointer to one.(The usage has always been unambiguous;there is nothing you ever could have done with a function pointerfollowed by an argument listexcept callthe function pointed to.)</p><p>The ANSI C Standard essentially adopts the latter interpretation,meaning that theexplicit <TT>*</TT> isnot required,though it isstill allowed.</p><p>See also question <a href="../decl/ptrfuncinit.html">1.34</a>.</p><p>References:K&R1 Sec. 5.12 p. 116<br>K&R2 Sec. 5.11 p. 120<br>ISO Sec. 6.3.2.2<br>Rationale Sec. 3.3.2.2<br>H&S Sec. 5.8 p. 147, Sec. 7.4.3 p. 190<br></p><!-- aend --><p><hr><a href="passbyref.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="generic.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/funccall.html by HTTrack Website Copier/3.x [XR&CO'2008], Sat, 14 Mar 2009 07:58:48 GMT --></html>⌨️ 快捷键说明
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