118 lines
5.0 KiB
HTML
118 lines
5.0 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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<!-- This file documents the GNU Assembler "as".
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Copyright (C) 1991-2016 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
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or any later version published by the Free Software Foundation;
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with no Invariant Sections, with no Front-Cover Texts, and with no
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Back-Cover Texts. A copy of the license is included in the
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section entitled "GNU Free Documentation License".
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-->
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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 as: Preprocessing</title>
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<meta name="description" content="Using as: Preprocessing">
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<meta name="keywords" content="Using as: Preprocessing">
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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="AS-Index.html#AS-Index" rel="index" title="AS Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Syntax.html#Syntax" rel="up" title="Syntax">
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<link href="Whitespace.html#Whitespace" rel="next" title="Whitespace">
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<link href="Syntax.html#Syntax" rel="prev" title="Syntax">
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<style type="text/css">
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<!--
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a.summary-letter {text-decoration: none}
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blockquote.smallquotation {font-size: smaller}
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div.display {margin-left: 3.2em}
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div.example {margin-left: 3.2em}
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div.indentedblock {margin-left: 3.2em}
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div.lisp {margin-left: 3.2em}
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div.smalldisplay {margin-left: 3.2em}
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div.smallexample {margin-left: 3.2em}
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div.smallindentedblock {margin-left: 3.2em; font-size: smaller}
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div.smalllisp {margin-left: 3.2em}
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kbd {font-style:oblique}
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pre.display {font-family: inherit}
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pre.format {font-family: inherit}
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pre.menu-comment {font-family: serif}
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pre.menu-preformatted {font-family: serif}
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pre.smalldisplay {font-family: inherit; font-size: smaller}
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pre.smallexample {font-size: smaller}
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pre.smallformat {font-family: inherit; font-size: smaller}
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pre.smalllisp {font-size: smaller}
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span.nocodebreak {white-space:nowrap}
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span.nolinebreak {white-space:nowrap}
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span.roman {font-family:serif; font-weight:normal}
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span.sansserif {font-family:sans-serif; font-weight:normal}
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ul.no-bullet {list-style: none}
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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="Preprocessing"></a>
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<div class="header">
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<p>
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Next: <a href="Whitespace.html#Whitespace" accesskey="n" rel="next">Whitespace</a>, Up: <a href="Syntax.html#Syntax" accesskey="u" rel="up">Syntax</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="AS-Index.html#AS-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="Preprocessing-1"></a>
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<h3 class="section">3.1 Preprocessing</h3>
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<a name="index-preprocessing"></a>
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<p>The <code>as</code> internal preprocessor:
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</p><ul>
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<li> <a name="index-whitespace_002c-removed-by-preprocessor"></a>
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adjusts and removes extra whitespace. It leaves one space or tab before
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the keywords on a line, and turns any other whitespace on the line into
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a single space.
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</li><li> <a name="index-comments_002c-removed-by-preprocessor"></a>
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removes all comments, replacing them with a single space, or an
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appropriate number of newlines.
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</li><li> <a name="index-constants_002c-converted-by-preprocessor"></a>
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converts character constants into the appropriate numeric values.
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</li></ul>
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<p>It does not do macro processing, include file handling, or
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anything else you may get from your C compiler’s preprocessor. You can
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do include file processing with the <code>.include</code> directive
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(see <a href="Include.html#Include"><code>.include</code></a>). You can use the <small>GNU</small> C compiler driver
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to get other “CPP” style preprocessing by giving the input file a
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‘<samp>.S</samp>’ suffix. See <a href="../gcc info/Overall-Options.html#Overall-Options">Options Controlling the Kind of
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Output</a> in <cite>Using GNU CC</cite>.
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</p>
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<p>Excess whitespace, comments, and character constants
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cannot be used in the portions of the input text that are not
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preprocessed.
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</p>
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<a name="index-turning-preprocessing-on-and-off"></a>
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<a name="index-preprocessing_002c-turning-on-and-off"></a>
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<a name="index-_0023NO_005fAPP"></a>
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<a name="index-_0023APP"></a>
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<p>If the first line of an input file is <code>#NO_APP</code> or if you use the
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‘<samp>-f</samp>’ option, whitespace and comments are not removed from the input file.
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Within an input file, you can ask for whitespace and comment removal in
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specific portions of the by putting a line that says <code>#APP</code> before the
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text that may contain whitespace or comments, and putting a line that says
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<code>#NO_APP</code> after this text. This feature is mainly intend to support
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<code>asm</code> statements in compilers whose output is otherwise free of comments
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and whitespace.
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</p>
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</body>
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</html>
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