1<html lang="en"> 2<head> 3<title>Library functions implementation - 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-Implementation.html#C-Implementation" title="C Implementation"> 9<link rel="prev" href="Preprocessing-directives-implementation.html#Preprocessing-directives-implementation" title="Preprocessing directives implementation"> 10<link rel="next" href="Architecture-implementation.html#Architecture-implementation" title="Architecture implementation"> 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="Library-functions-implementation"></a> 51<p> 52Next: <a rel="next" accesskey="n" href="Architecture-implementation.html#Architecture-implementation">Architecture implementation</a>, 53Previous: <a rel="previous" accesskey="p" href="Preprocessing-directives-implementation.html#Preprocessing-directives-implementation">Preprocessing directives implementation</a>, 54Up: <a rel="up" accesskey="u" href="C-Implementation.html#C-Implementation">C Implementation</a> 55<hr> 56</div> 57 58<h3 class="section">4.14 Library functions</h3> 59 60<p>The behavior of most of these points are dependent on the implementation 61of the C library, and are not defined by GCC itself. 62 63 <ul> 64<li><cite>The null pointer constant to which the macro </cite><code>NULL</code><cite> expands 65(C90 7.1.6, C99 7.17).</cite> 66 67 <p>In <code><stddef.h></code>, <code>NULL</code> expands to <code>((void *)0)</code>. GCC 68does not provide the other headers which define <code>NULL</code> and some 69library implementations may use other definitions in those headers. 70 71 </ul> 72 73 </body></html> 74 75