132 lines
5.4 KiB
HTML
132 lines
5.4 KiB
HTML
<!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 linker LD
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(Linaro_Binutils-2017.02)
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version 2.27.0.
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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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<!-- Created by GNU Texinfo 5.2, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>LD: Simple Assignments</title>
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<meta name="description" content="LD: Simple Assignments">
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<meta name="keywords" content="LD: Simple Assignments">
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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="LD-Index.html#LD-Index" rel="index" title="LD Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Assignments.html#Assignments" rel="up" title="Assignments">
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<link href="HIDDEN.html#HIDDEN" rel="next" title="HIDDEN">
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<link href="Assignments.html#Assignments" rel="prev" title="Assignments">
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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="Simple-Assignments"></a>
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<div class="header">
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<p>
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Next: <a href="HIDDEN.html#HIDDEN" accesskey="n" rel="next">HIDDEN</a>, Up: <a href="Assignments.html#Assignments" accesskey="u" rel="up">Assignments</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="LD-Index.html#LD-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="Simple-Assignments-1"></a>
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<h4 class="subsection">3.5.1 Simple Assignments</h4>
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<p>You may assign to a symbol using any of the C assignment operators:
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</p>
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<dl compact="compact">
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<dt><code><var>symbol</var> = <var>expression</var> ;</code></dt>
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<dt><code><var>symbol</var> += <var>expression</var> ;</code></dt>
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<dt><code><var>symbol</var> -= <var>expression</var> ;</code></dt>
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<dt><code><var>symbol</var> *= <var>expression</var> ;</code></dt>
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<dt><code><var>symbol</var> /= <var>expression</var> ;</code></dt>
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<dt><code><var>symbol</var> <<= <var>expression</var> ;</code></dt>
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<dt><code><var>symbol</var> >>= <var>expression</var> ;</code></dt>
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<dt><code><var>symbol</var> &= <var>expression</var> ;</code></dt>
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<dt><code><var>symbol</var> |= <var>expression</var> ;</code></dt>
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</dl>
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<p>The first case will define <var>symbol</var> to the value of
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<var>expression</var>. In the other cases, <var>symbol</var> must already be
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defined, and the value will be adjusted accordingly.
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</p>
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<p>The special symbol name ‘<samp>.</samp>’ indicates the location counter. You
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may only use this within a <code>SECTIONS</code> command. See <a href="Location-Counter.html#Location-Counter">Location Counter</a>.
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</p>
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<p>The semicolon after <var>expression</var> is required.
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</p>
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<p>Expressions are defined below; see <a href="Expressions.html#Expressions">Expressions</a>.
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</p>
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<p>You may write symbol assignments as commands in their own right, or as
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statements within a <code>SECTIONS</code> command, or as part of an output
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section description in a <code>SECTIONS</code> command.
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</p>
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<p>The section of the symbol will be set from the section of the
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expression; for more information, see <a href="Expression-Section.html#Expression-Section">Expression Section</a>.
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</p>
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<p>Here is an example showing the three different places that symbol
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assignments may be used:
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</p>
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<div class="smallexample">
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<pre class="smallexample">floating_point = 0;
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SECTIONS
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{
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.text :
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{
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*(.text)
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_etext = .;
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}
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_bdata = (. + 3) & ~ 3;
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.data : { *(.data) }
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}
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</pre></div>
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<p>In this example, the symbol ‘<samp>floating_point</samp>’ will be defined as
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zero. The symbol ‘<samp>_etext</samp>’ will be defined as the address following
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the last ‘<samp>.text</samp>’ input section. The symbol ‘<samp>_bdata</samp>’ will be
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defined as the address following the ‘<samp>.text</samp>’ output section aligned
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upward to a 4 byte boundary.
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</p>
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</body>
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</html>
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