1<html lang="en"> 2<head> 3<title>Pointer Arith - 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="Subscripting.html#Subscripting" title="Subscripting"> 10<link rel="next" href="Initializers.html#Initializers" title="Initializers"> 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="Pointer-Arith"></a> 51<p> 52Next: <a rel="next" accesskey="n" href="Initializers.html#Initializers">Initializers</a>, 53Previous: <a rel="previous" accesskey="p" href="Subscripting.html#Subscripting">Subscripting</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">6.23 Arithmetic on <code>void</code>- and Function-Pointers</h3> 59 60<p><a name="index-void-pointers_002c-arithmetic-2367"></a><a name="index-void_002c-size-of-pointer-to-2368"></a><a name="index-function-pointers_002c-arithmetic-2369"></a><a name="index-function_002c-size-of-pointer-to-2370"></a> 61In GNU C, addition and subtraction operations are supported on pointers to 62<code>void</code> and on pointers to functions. This is done by treating the 63size of a <code>void</code> or of a function as 1. 64 65 <p>A consequence of this is that <code>sizeof</code> is also allowed on <code>void</code> 66and on function types, and returns 1. 67 68 <p><a name="index-Wpointer_002darith-2371"></a>The option <samp><span class="option">-Wpointer-arith</span></samp> requests a warning if these extensions 69are used. 70 71 </body></html> 72 73