1<html lang="en"> 2<head> 3<title>Traditional miscellany - 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="up" href="Traditional-Mode.html#Traditional-Mode" title="Traditional Mode"> 9<link rel="prev" href="Traditional-macros.html#Traditional-macros" title="Traditional macros"> 10<link rel="next" href="Traditional-warnings.html#Traditional-warnings" title="Traditional warnings"> 11<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> 12<!-- 13Copyright (C) 1987, 1989, 1991, 1992, 1993, 1994, 1995, 1996, 141997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 152008, 2009, 2010, 2011 16Free Software Foundation, Inc. 17 18Permission is granted to copy, distribute and/or modify this document 19under the terms of the GNU Free Documentation License, Version 1.3 or 20any later version published by the Free Software Foundation. A copy of 21the license is included in the 22section entitled ``GNU Free Documentation License''. 23 24This manual contains no Invariant Sections. The Front-Cover Texts are 25(a) (see below), and the Back-Cover Texts are (b) (see below). 26 27(a) The FSF's Front-Cover Text is: 28 29 A GNU Manual 30 31(b) The FSF's Back-Cover Text is: 32 33 You have freedom to copy and modify this GNU Manual, like GNU 34 software. Copies published by the Free Software Foundation raise 35 funds for GNU development. 36--> 37<meta http-equiv="Content-Style-Type" content="text/css"> 38<style type="text/css"><!-- 39 pre.display { font-family:inherit } 40 pre.format { font-family:inherit } 41 pre.smalldisplay { font-family:inherit; font-size:smaller } 42 pre.smallformat { font-family:inherit; font-size:smaller } 43 pre.smallexample { font-size:smaller } 44 pre.smalllisp { font-size:smaller } 45 span.sc { font-variant:small-caps } 46 span.roman { font-family:serif; font-weight:normal; } 47 span.sansserif { font-family:sans-serif; font-weight:normal; } 48--></style> 49<link rel="stylesheet" type="text/css" href="../cs.css"> 50</head> 51<body> 52<div class="node"> 53<a name="Traditional-miscellany"></a> 54<p> 55Next: <a rel="next" accesskey="n" href="Traditional-warnings.html#Traditional-warnings">Traditional warnings</a>, 56Previous: <a rel="previous" accesskey="p" href="Traditional-macros.html#Traditional-macros">Traditional macros</a>, 57Up: <a rel="up" accesskey="u" href="Traditional-Mode.html#Traditional-Mode">Traditional Mode</a> 58<hr> 59</div> 60 61<h3 class="section">10.3 Traditional miscellany</h3> 62 63<p>Here are some things to be aware of when using the traditional 64preprocessor. 65 66 <ul> 67<li>Preprocessing directives are recognized only when their leading 68‘<samp><span class="samp">#</span></samp>’ appears in the first column. There can be no whitespace 69between the beginning of the line and the ‘<samp><span class="samp">#</span></samp>’, but whitespace can 70follow the ‘<samp><span class="samp">#</span></samp>’. 71 72 <li>A true traditional C preprocessor does not recognize ‘<samp><span class="samp">#error</span></samp>’ or 73‘<samp><span class="samp">#pragma</span></samp>’, and may not recognize ‘<samp><span class="samp">#elif</span></samp>’. CPP supports all 74the directives in traditional mode that it supports in ISO mode, 75including extensions, with the exception that the effects of 76‘<samp><span class="samp">#pragma GCC poison</span></samp>’ are undefined. 77 78 <li>__STDC__ is not defined. 79 80 <li>If you use digraphs the behavior is undefined. 81 82 <li>If a line that looks like a directive appears within macro arguments, 83the behavior is undefined. 84 85 </ul> 86 87 </body></html> 88 89