1<html lang="en"> 2<head> 3<title>Incomplete Enums - Using the GNU Compiler Collection (GCC)</title> 4<meta http-equiv="Content-Type" content="text/html"> 5<meta name="description" content="Using the GNU Compiler Collection (GCC)"> 6<meta name="generator" content="makeinfo 4.13"> 7<link title="Top" rel="start" href="index.html#Top"> 8<link rel="up" href="C-Extensions.html#C-Extensions" title="C Extensions"> 9<link rel="prev" href="Alternate-Keywords.html#Alternate-Keywords" title="Alternate Keywords"> 10<link rel="next" href="Function-Names.html#Function-Names" title="Function Names"> 11<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> 12<!-- 13Copyright (C) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 141998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 152010 Free Software Foundation, Inc. 16 17Permission is granted to copy, distribute and/or modify this document 18under the terms of the GNU Free Documentation License, Version 1.3 or 19any later version published by the Free Software Foundation; with the 20Invariant Sections being ``Funding Free Software'', the Front-Cover 21Texts being (a) (see below), and with the Back-Cover Texts being (b) 22(see below). A copy of the license is included in the section entitled 23``GNU Free Documentation License''. 24 25(a) The FSF's Front-Cover Text is: 26 27 A GNU Manual 28 29(b) The FSF's Back-Cover Text is: 30 31 You have freedom to copy and modify this GNU Manual, like GNU 32 software. Copies published by the Free Software Foundation raise 33 funds for GNU development.--> 34<meta http-equiv="Content-Style-Type" content="text/css"> 35<style type="text/css"><!-- 36 pre.display { font-family:inherit } 37 pre.format { font-family:inherit } 38 pre.smalldisplay { font-family:inherit; font-size:smaller } 39 pre.smallformat { font-family:inherit; font-size:smaller } 40 pre.smallexample { font-size:smaller } 41 pre.smalllisp { font-size:smaller } 42 span.sc { font-variant:small-caps } 43 span.roman { font-family:serif; font-weight:normal; } 44 span.sansserif { font-family:sans-serif; font-weight:normal; } 45--></style> 46<link rel="stylesheet" type="text/css" href="../cs.css"> 47</head> 48<body> 49<div class="node"> 50<a name="Incomplete-Enums"></a> 51<p> 52Next: <a rel="next" accesskey="n" href="Function-Names.html#Function-Names">Function Names</a>, 53Previous: <a rel="previous" accesskey="p" href="Alternate-Keywords.html#Alternate-Keywords">Alternate Keywords</a>, 54Up: <a rel="up" accesskey="u" href="C-Extensions.html#C-Extensions">C Extensions</a> 55<hr> 56</div> 57 58<h3 class="section">6.46 Incomplete <code>enum</code> Types</h3> 59 60<p>You can define an <code>enum</code> tag without specifying its possible values. 61This results in an incomplete type, much like what you get if you write 62<code>struct foo</code> without describing the elements. A later declaration 63which does specify the possible values completes the type. 64 65 <p>You can't allocate variables or storage using the type while it is 66incomplete. However, you can work with pointers to that type. 67 68 <p>This extension may not be very useful, but it makes the handling of 69<code>enum</code> more consistent with the way <code>struct</code> and <code>union</code> 70are handled. 71 72 <p>This extension is not supported by GNU C++. 73 74 </body></html> 75 76