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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!-- but may not be published or retransmitted without explicit permission.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 decl.sgml dated Wed Dec 21 12:56:18 2005 --><!-- corresponding to FAQ list version 4.0 --><html><!-- Mirrored from c-faq.com/decl/charstarws.html by HTTrack Website Copier/3.x [XR&CO'2008], Sat, 14 Mar 2009 07:58:41 GMT --><head><meta name=GENERATOR content="faqproc"><title>Question 1.5</title><link href="octabyte.html" rev=precedes><link href="mimic.html" rel=precedes><link href="index.html" rev=subdocument></head><body bgcolor="#ffffff"><a href="octabyte.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="mimic.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 1.5</h1><p><font face=Helvetica size=8 color=blue><b>Q:</b></font>What's wrong withthisdeclaration?<pre>char* p1, p2;</pre>I get errors when I try touse<TT>p2</TT>.</p><p><hr><p><font face=Helvetica size=8 color=blue><b>A:</b></font>Nothing is wrong with the declaration--exceptthat it doesn't do what you probably want.The <TT>*</TT> in a pointer declaration is not part of the base type;it is part of the <a href="../sx1/index.html#declarator"><dfn>declarator</dfn></a>containing the name being declared(see question <a href="cdecl1.html">1.21</a>).That is,in C, the syntax and interpretation of a declaration is not really<pre> <I>type identifier</I> ;</pre>but rather<pre> <I>base_type thing_that_gives_base_type</I> ;</pre>where ``<I>thing_that_gives_base_type</I>''--the<a href="../sx1/index.html#declarator"><dfn>declarator</dfn></a>--iseither a simple identifier,or a notation like <TT>*p</TT> or <TT>a[10]</TT> or <TT>f()</TT>indicating that the variable being declared is a pointer to,array of, or function returning that <I>base_type</I>.(Of course, more complicated declarators are possible as well.)</p><p>In the declarationas written in the question,no matter what the whitespacesuggests,the base type is <TT>char</TT> andthe first declarator is ``<TT>* p1</TT>'',and since the declarator contains a <TT>*</TT>,it declares <TT>p1</TT> as a pointer-to-<TT>char</TT>.The declarator for <TT>p2</TT>, however,contains nothing but <TT>p2</TT>,so <TT>p2</TT> is declared as a plain <TT>char</TT>,probably not what was intended.To declare two pointers within the same declaration,use<pre> char *p1, *p2;</pre>Since the <TT>*</TT> is part of the declarator,it's best to use whitespace as shown;writing <TT>char*</TT> invites mistakes and confusion.</p><p>See also question <a href="typedefvsdefine.html">1.13</a>.</p><p>Additional links:<a href="http://www.research.att.com/~bs/bs_faq2.html#whitespace">Bjarne Stroustrup's opinion</a></p><!-- aend --><p><hr><a href="octabyte.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="mimic.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/decl/charstarws.html by HTTrack Website Copier/3.x [XR&CO'2008], Sat, 14 Mar 2009 07:58:41 GMT --></html>⌨️ 快捷键说明
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