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83 lines
3.9 KiB
HTML
83 lines
3.9 KiB
HTML
4 years ago
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<html lang="en">
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<head>
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<title>Preprocessing - Using as</title>
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<meta http-equiv="Content-Type" content="text/html">
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<meta name="description" content="Using as">
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<meta name="generator" content="makeinfo 4.13">
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<link title="Top" rel="start" href="index.html#Top">
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<link rel="up" href="Syntax.html#Syntax" title="Syntax">
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<link rel="next" href="Whitespace.html#Whitespace" title="Whitespace">
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<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
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<!--
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This file documents the GNU Assembler "as".
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Copyright (C) 1991-2015 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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<meta http-equiv="Content-Style-Type" content="text/css">
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<style type="text/css"><!--
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pre.display { font-family:inherit }
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pre.format { font-family:inherit }
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pre.smalldisplay { font-family:inherit; font-size:smaller }
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pre.smallformat { font-family:inherit; font-size:smaller }
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pre.smallexample { font-size:smaller }
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pre.smalllisp { font-size:smaller }
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span.sc { font-variant:small-caps }
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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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--></style>
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</head>
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<body>
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<div class="node">
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<a name="Preprocessing"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="Whitespace.html#Whitespace">Whitespace</a>,
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Up: <a rel="up" accesskey="u" href="Syntax.html#Syntax">Syntax</a>
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<hr>
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</div>
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<h3 class="section">3.1 Preprocessing</h3>
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<p><a name="index-preprocessing-114"></a>The <samp><span class="command">as</span></samp> internal preprocessor:
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<a name="index-whitespace_002c-removed-by-preprocessor-115"></a>
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<ul><li>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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<p><a name="index-comments_002c-removed-by-preprocessor-116"></a><li>removes all comments, replacing them with a single space, or an
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appropriate number of newlines.
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<p><a name="index-constants_002c-converted-by-preprocessor-117"></a><li>converts character constants into the appropriate numeric values.
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</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 <span class="sc">gnu</span> C compiler driver
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to get other “CPP” style preprocessing by giving the input file a
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‘<samp><span class="samp">.S</span></samp>’ suffix. See <a href="../gcc/Overall-Options.html#Overall-Options">Options Controlling the Kind of Output</a>.
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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><a name="index-turning-preprocessing-on-and-off-118"></a><a name="index-preprocessing_002c-turning-on-and-off-119"></a><a name="index-g_t_0023NO_005fAPP-120"></a><a name="index-g_t_0023APP-121"></a>If the first line of an input file is <code>#NO_APP</code> or if you use the
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‘<samp><span class="samp">-f</span></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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</body></html>
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