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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!-- but may not be published or retransmitted without explicit permission.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 struct.sgml dated Wed Dec 21 16:15:32 2005 --><!-- corresponding to FAQ list version 4.0 --><html><!-- Mirrored from c-faq.com/struct/index.html by HTTrack Website Copier/3.x [XR&CO'2008], Sat, 14 Mar 2009 07:54:01 GMT --><head><meta name=GENERATOR content="faqproc"><title>Structures, Unions, and Enumerations</title></head><body bgcolor="#ffffff"> <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><H1>2. Structures, Unions, and Enumerations</H1><p><a href="typedef.html" rel=subdocument>2.1</a>What's the difference betweenthese two declarations?<pre> struct x1 { ... }; typedef struct { ... } x2;</pre></p><p><a href="impltypedef.html" rel=subdocument>2.2</a>Why doesn't<pre>struct x { ... };x thestruct;</pre>work?</p><p><a href="selfref.html" rel=subdocument>2.3</a>Can a structure contain a pointerto itself?</p><p><a href="opaquetypes.html" rel=subdocument>2.4</a>How can I implementopaque (abstract) data types in C?</p><p><a href="oop.html" rel=subdocument>2.4b</a>Is there a good way of simulating OOP-style inheritance,or other OOP features,in C?</p><p><a href="fcnproto.html" rel=subdocument>2.5</a>Why does the declaration<pre>extern int f(struct x *p);</pre>give mean obscurewarning messageabout``struct x declared inside parameter list''?</p><p><a href="structhack.html" rel=subdocument>2.6</a>I came across some code that declared a structurelike this:<pre>struct name { int namelen; char namestr[1];};</pre>and then did some tricky allocation to makethe<TT>namestr</TT>array act like ithad several elements,with the numberrecorded by <TT>namelen</TT>.How does this work?Isitlegal or portable?</p><p><a href="firstclass.html" rel=subdocument>2.7</a>I heardthat structures could be assignedto variables and passed to and from functions, but K&R1saysnot.</p><p><a href="compare.html" rel=subdocument>2.8</a>Is there a way tocompare structuresautomatically?</p><p><a href="passret.html" rel=subdocument>2.9</a>Howarestructure passing and returningimplemented?</p><p><a href="anonstruct.html" rel=subdocument>2.10</a>How canI pass constant values to functions which accept structure arguments?How can I create nameless, immediate, constant structure values?</p><p><a href="io.html" rel=subdocument>2.11</a>How can I read/write structures from/todata files?</p><p><a href="padding.html" rel=subdocument>2.12</a>Why is mycompilerleaving holes in structures,wasting spaceand preventing``binary'' I/O to external datafiles?CanI turnthisoff,or otherwise control the alignment of structure fields?</p><p><a href="endpad.html" rel=subdocument>2.13</a>Why does <TT>sizeof</TT> report a larger size than I expect for astructure type,as if there were padding at the end?</p><p><a href="offsetof.html" rel=subdocument>2.14</a>How can I determine the byte offset of a field within a structure?</p><p><a href="fieldnames.html" rel=subdocument>2.15</a>How can I access structure fields by name at run time?</p><p><a href="withxref.html" rel=subdocument>2.16</a>Does C have an equivalent to Pascal's<TT>with</TT> statement?</p><p><a href="decay.html" rel=subdocument>2.17</a>If an array name acts like a pointer to the base of an array,why isn't the same thing true of a structure?</p><p><a href="retcrash.html" rel=subdocument>2.18</a>This programworks correctly, butitdumps coreafter itfinishes.Why?<pre> struct list { char *item; struct list *next; } /* Here is the main program. */ main(argc, argv) { ... }</pre></p><p><a href="union.html" rel=subdocument>2.19</a>What's the difference between a structure and a union, anyway?</p><p><a href="initunion.html" rel=subdocument>2.20</a>Can I initialize unions?</p><p><a href="taggedunion.html" rel=subdocument>2.21</a>Is there an automatic wayto keep track of which field of a union is in use?</p><p><a href="enumvsdefine.html" rel=subdocument>2.22</a>What's the difference betweenan enumeration and a set ofpreprocessor <TT>#define</TT>s?</p><p><a href="enumport.html" rel=subdocument>2.23</a>Are enumerations really portable?<br>Aren't they Pascalish?<br></p><p><a href="enumprint.html" rel=subdocument>2.24</a>Is there an easy way to print enumeration values symbolically?</p><p><a href="bitfield0.html" rel=subdocument>2.25</a>I came across some structure declarations with colons and numbers next to certainfields,like this:<pre>struct record { char *name; int refcount : 4; unsigned dirty : 1;};</pre>What gives?</p><p><a href="bitfields.html" rel=subdocument>2.26</a>Why do people use explicit masks andbit-twiddlingcode so much,instead of declaring bit-fields?</p><hr><p><a href="../index-2.html">top</a></p><p><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><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></p></body><!-- Mirrored from c-faq.com/struct/index.html by HTTrack Website Copier/3.x [XR&CO'2008], Sat, 14 Mar 2009 07:54:12 GMT --></html>⌨️ 快捷键说明
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