122 lines
5.4 KiB
HTML
122 lines
5.4 KiB
HTML
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<!-- Copyright (C) 1988-2016 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3 or
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any later version published by the Free Software Foundation; with the
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Invariant Sections being "Funding Free Software", the Front-Cover
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Texts being (a) (see below), and with the Back-Cover Texts being (b)
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(see below). A copy of the license is included in the section entitled
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"GNU Free Documentation License".
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(a) The FSF's Front-Cover Text is:
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A GNU Manual
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(b) The FSF's Back-Cover Text is:
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You have freedom to copy and modify this GNU Manual, like GNU
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software. Copies published by the Free Software Foundation raise
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funds for GNU development. -->
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<!-- Created by GNU Texinfo 5.2, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>Using the GNU Compiler Collection (GCC): Alternate Keywords</title>
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<meta name="description" content="Using the GNU Compiler Collection (GCC): Alternate Keywords">
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<meta name="keywords" content="Using the GNU Compiler Collection (GCC): Alternate Keywords">
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<meta name="resource-type" content="document">
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<meta name="distribution" content="global">
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<meta name="Generator" content="makeinfo">
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<link href="index.html#Top" rel="start" title="Top">
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<link href="Option-Index.html#Option-Index" rel="index" title="Option Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="C-Extensions.html#C-Extensions" rel="up" title="C Extensions">
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<link href="Incomplete-Enums.html#Incomplete-Enums" rel="next" title="Incomplete Enums">
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<link href="Size-of-an-asm.html#Size-of-an-asm" rel="prev" title="Size of an asm">
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<style type="text/css">
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-->
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</style>
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</head>
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<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
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<a name="Alternate-Keywords"></a>
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<div class="header">
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<p>
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Next: <a href="Incomplete-Enums.html#Incomplete-Enums" accesskey="n" rel="next">Incomplete Enums</a>, Previous: <a href="Using-Assembly-Language-with-C.html#Using-Assembly-Language-with-C" accesskey="p" rel="prev">Using Assembly Language with C</a>, Up: <a href="C-Extensions.html#C-Extensions" accesskey="u" rel="up">C Extensions</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="Alternate-Keywords-1"></a>
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<h3 class="section">6.45 Alternate Keywords</h3>
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<a name="index-alternate-keywords"></a>
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<a name="index-keywords_002c-alternate"></a>
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<p><samp>-ansi</samp> and the various <samp>-std</samp> options disable certain
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keywords. This causes trouble when you want to use GNU C extensions, or
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a general-purpose header file that should be usable by all programs,
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including ISO C programs. The keywords <code>asm</code>, <code>typeof</code> and
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<code>inline</code> are not available in programs compiled with
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<samp>-ansi</samp> or <samp>-std</samp> (although <code>inline</code> can be used in a
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program compiled with <samp>-std=c99</samp> or <samp>-std=c11</samp>). The
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ISO C99 keyword
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<code>restrict</code> is only available when <samp>-std=gnu99</samp> (which will
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eventually be the default) or <samp>-std=c99</samp> (or the equivalent
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<samp>-std=iso9899:1999</samp>), or an option for a later standard
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version, is used.
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</p>
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<p>The way to solve these problems is to put ‘<samp>__</samp>’ at the beginning and
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end of each problematical keyword. For example, use <code>__asm__</code>
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instead of <code>asm</code>, and <code>__inline__</code> instead of <code>inline</code>.
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</p>
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<p>Other C compilers won’t accept these alternative keywords; if you want to
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compile with another compiler, you can define the alternate keywords as
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macros to replace them with the customary keywords. It looks like this:
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</p>
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<div class="smallexample">
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<pre class="smallexample">#ifndef __GNUC__
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#define __asm__ asm
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#endif
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</pre></div>
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<a name="index-_005f_005fextension_005f_005f"></a>
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<a name="index-pedantic-4"></a>
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<p><samp>-pedantic</samp> and other options cause warnings for many GNU C extensions.
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You can
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prevent such warnings within one expression by writing
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<code>__extension__</code> before the expression. <code>__extension__</code> has no
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effect aside from this.
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</p>
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</body>
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</html>
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