<html lang="en"> <head> <title>Alternate Keywords - 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-Extensions.html#C-Extensions" title="C Extensions"> <link rel="prev" href="Using-Assembly-Language-with-C.html#Using-Assembly-Language-with-C" title="Using Assembly Language with C"> <link rel="next" href="Incomplete-Enums.html#Incomplete-Enums" title="Incomplete Enums"> <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="Alternate-Keywords"></a> <p> Next: <a rel="next" accesskey="n" href="Incomplete-Enums.html#Incomplete-Enums">Incomplete Enums</a>, Previous: <a rel="previous" accesskey="p" href="Using-Assembly-Language-with-C.html#Using-Assembly-Language-with-C">Using Assembly Language with C</a>, Up: <a rel="up" accesskey="u" href="C-Extensions.html#C-Extensions">C Extensions</a> <hr> </div> <h3 class="section">6.44 Alternate Keywords</h3> <p><a name="index-alternate-keywords-3507"></a><a name="index-keywords_002c-alternate-3508"></a> <samp><span class="option">-ansi</span></samp> and the various <samp><span class="option">-std</span></samp> options disable certain keywords. This causes trouble when you want to use GNU C extensions, or a general-purpose header file that should be usable by all programs, including ISO C programs. The keywords <code>asm</code>, <code>typeof</code> and <code>inline</code> are not available in programs compiled with <samp><span class="option">-ansi</span></samp> or <samp><span class="option">-std</span></samp> (although <code>inline</code> can be used in a program compiled with <samp><span class="option">-std=c99</span></samp> or <samp><span class="option">-std=c11</span></samp>). The ISO C99 keyword <code>restrict</code> is only available when <samp><span class="option">-std=gnu99</span></samp> (which will eventually be the default) or <samp><span class="option">-std=c99</span></samp> (or the equivalent <samp><span class="option">-std=iso9899:1999</span></samp>), or an option for a later standard version, is used. <p>The way to solve these problems is to put ‘<samp><span class="samp">__</span></samp>’ at the beginning and end of each problematical keyword. For example, use <code>__asm__</code> instead of <code>asm</code>, and <code>__inline__</code> instead of <code>inline</code>. <p>Other C compilers won't accept these alternative keywords; if you want to compile with another compiler, you can define the alternate keywords as macros to replace them with the customary keywords. It looks like this: <pre class="smallexample"> #ifndef __GNUC__ #define __asm__ asm #endif </pre> <p><a name="index-g_t_005f_005fextension_005f_005f-3509"></a><a name="index-pedantic-3510"></a><samp><span class="option">-pedantic</span></samp> and other options cause warnings for many GNU C extensions. You can prevent such warnings within one expression by writing <code>__extension__</code> before the expression. <code>__extension__</code> has no effect aside from this. </body></html>