<html lang="en">
<head>
<title>Library functions implementation - Using the GNU Compiler Collection (GCC)</title>
<meta http-equiv="Content-Type" content="text/html">
<meta name="description" content="Using the GNU Compiler Collection (GCC)">
<meta name="generator" content="makeinfo 4.13">
<link title="Top" rel="start" href="index.html#Top">
<link rel="up" href="C-Implementation.html#C-Implementation" title="C Implementation">
<link rel="prev" href="Preprocessing-directives-implementation.html#Preprocessing-directives-implementation" title="Preprocessing directives implementation">
<link rel="next" href="Architecture-implementation.html#Architecture-implementation" title="Architecture implementation">
<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
<!--
Copyright (C) 1988-2015 Free Software Foundation, Inc.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with the
Invariant Sections being ``Funding Free Software'', the Front-Cover
Texts being (a) (see below), and with the Back-Cover Texts being (b)
(see below). A copy of the license is included in the section entitled
``GNU Free Documentation License''.
(a) The FSF's Front-Cover Text is:
A GNU Manual
(b) The FSF's Back-Cover Text is:
You have freedom to copy and modify this GNU Manual, like GNU
software. Copies published by the Free Software Foundation raise
funds for GNU development.-->
<meta http-equiv="Content-Style-Type" content="text/css">
<style type="text/css"><!--
pre.display { font-family:inherit }
pre.format { font-family:inherit }
pre.smalldisplay { font-family:inherit; font-size:smaller }
pre.smallformat { font-family:inherit; font-size:smaller }
pre.smallexample { font-size:smaller }
pre.smalllisp { font-size:smaller }
span.sc { font-variant:small-caps }
span.roman { font-family:serif; font-weight:normal; }
span.sansserif { font-family:sans-serif; font-weight:normal; }
--></style>
</head>
<body>
<div class="node">
<a name="Library-functions-implementation"></a>
<p>
Next: <a rel="next" accesskey="n" href="Architecture-implementation.html#Architecture-implementation">Architecture implementation</a>,
Previous: <a rel="previous" accesskey="p" href="Preprocessing-directives-implementation.html#Preprocessing-directives-implementation">Preprocessing directives implementation</a>,
Up: <a rel="up" accesskey="u" href="C-Implementation.html#C-Implementation">C Implementation</a>
<hr>
</div>
<h3 class="section">4.14 Library Functions</h3>
<p>The behavior of most of these points are dependent on the implementation
of the C library, and are not defined by GCC itself.
<ul>
<li><cite>The null pointer constant to which the macro </cite><code>NULL</code><cite> expands
(C90 7.1.6, C99 7.17, C11 7.19).</cite>
<p>In <code><stddef.h></code>, <code>NULL</code> expands to <code>((void *)0)</code>. GCC
does not provide the other headers which define <code>NULL</code> and some
library implementations may use other definitions in those headers.
</ul>
</body></html>