1<html lang="en"> 2<head> 3<title>Other Directives - The C Preprocessor</title> 4<meta http-equiv="Content-Type" content="text/html"> 5<meta name="description" content="The C Preprocessor"> 6<meta name="generator" content="makeinfo 4.13"> 7<link title="Top" rel="start" href="index.html#Top"> 8<link rel="prev" href="Pragmas.html#Pragmas" title="Pragmas"> 9<link rel="next" href="Preprocessor-Output.html#Preprocessor-Output" title="Preprocessor Output"> 10<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> 11<!-- 12Copyright (C) 1987, 1989, 1991, 1992, 1993, 1994, 1995, 1996, 131997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 142008, 2009, 2010, 2011 15Free 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. A copy of 20the license is included in the 21section entitled ``GNU Free Documentation License''. 22 23This manual contains no Invariant Sections. The Front-Cover Texts are 24(a) (see below), and the Back-Cover Texts are (b) (see below). 25 26(a) The FSF's Front-Cover Text is: 27 28 A GNU Manual 29 30(b) The FSF's Back-Cover Text is: 31 32 You have freedom to copy and modify this GNU Manual, like GNU 33 software. Copies published by the Free Software Foundation raise 34 funds for GNU development. 35--> 36<meta http-equiv="Content-Style-Type" content="text/css"> 37<style type="text/css"><!-- 38 pre.display { font-family:inherit } 39 pre.format { font-family:inherit } 40 pre.smalldisplay { font-family:inherit; font-size:smaller } 41 pre.smallformat { font-family:inherit; font-size:smaller } 42 pre.smallexample { font-size:smaller } 43 pre.smalllisp { font-size:smaller } 44 span.sc { font-variant:small-caps } 45 span.roman { font-family:serif; font-weight:normal; } 46 span.sansserif { font-family:sans-serif; font-weight:normal; } 47--></style> 48<link rel="stylesheet" type="text/css" href="../cs.css"> 49</head> 50<body> 51<div class="node"> 52<a name="Other-Directives"></a> 53<p> 54Next: <a rel="next" accesskey="n" href="Preprocessor-Output.html#Preprocessor-Output">Preprocessor Output</a>, 55Previous: <a rel="previous" accesskey="p" href="Pragmas.html#Pragmas">Pragmas</a>, 56Up: <a rel="up" accesskey="u" href="index.html#Top">Top</a> 57<hr> 58</div> 59 60<h2 class="chapter">8 Other Directives</h2> 61 62<p><a name="index-g_t_0023ident-104"></a><a name="index-g_t_0023sccs-105"></a>The ‘<samp><span class="samp">#ident</span></samp>’ directive takes one argument, a string constant. On 63some systems, that string constant is copied into a special segment of 64the object file. On other systems, the directive is ignored. The 65‘<samp><span class="samp">#sccs</span></samp>’ directive is a synonym for ‘<samp><span class="samp">#ident</span></samp>’. 66 67 <p>These directives are not part of the C standard, but they are not 68official GNU extensions either. What historical information we have 69been able to find, suggests they originated with System V. 70 71 <p><a name="index-null-directive-106"></a>The <dfn>null directive</dfn> consists of a ‘<samp><span class="samp">#</span></samp>’ followed by a newline, 72with only whitespace (including comments) in between. A null directive 73is understood as a preprocessing directive but has no effect on the 74preprocessor output. The primary significance of the existence of the 75null directive is that an input line consisting of just a ‘<samp><span class="samp">#</span></samp>’ will 76produce no output, rather than a line of output containing just a 77‘<samp><span class="samp">#</span></samp>’. Supposedly some old C programs contain such lines. 78 79 </body></html> 80 81