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93 lines
4.3 KiB
HTML
93 lines
4.3 KiB
HTML
15 years ago
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<html lang="en">
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<head>
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<title>Simple Assignments - Untitled</title>
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<meta http-equiv="Content-Type" content="text/html">
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<meta name="description" content="Untitled">
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<meta name="generator" content="makeinfo 4.7">
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<link title="Top" rel="start" href="index.html#Top">
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<link rel="up" href="Assignments.html#Assignments" title="Assignments">
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<link rel="next" href="PROVIDE.html#PROVIDE" title="PROVIDE">
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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 linker LD
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(GNU Binutils)
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version 2.19.
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Copyright (C) 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000,
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2001, 2002, 2003, 2004, 2005, 2006, 2007 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 1.1
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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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<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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--></style>
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</head>
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<body>
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<div class="node">
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<p>
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<a name="Simple-Assignments"></a>Next: <a rel="next" accesskey="n" href="PROVIDE.html#PROVIDE">PROVIDE</a>,
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Up: <a rel="up" accesskey="u" href="Assignments.html#Assignments">Assignments</a>
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<hr><br>
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</div>
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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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<dl>
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<dt><var>symbol</var><code> = </code><var>expression</var><code> ;</code><dt><var>symbol</var><code> += </code><var>expression</var><code> ;</code><dt><var>symbol</var><code> -= </code><var>expression</var><code> ;</code><dt><var>symbol</var><code> *= </code><var>expression</var><code> ;</code><dt><var>symbol</var><code> /= </code><var>expression</var><code> ;</code><dt><var>symbol</var><code> <<= </code><var>expression</var><code> ;</code><dt><var>symbol</var><code> >>= </code><var>expression</var><code> ;</code><dt><var>symbol</var><code> &= </code><var>expression</var><code> ;</code><dt><var>symbol</var><code> |= </code><var>expression</var><code> ;</code><dd></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>The special symbol name <span class="samp">.</span> 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>The semicolon after <var>expression</var> is required.
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<p>Expressions are defined below; see <a href="Expressions.html#Expressions">Expressions</a>.
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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>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>Here is an example showing the three different places that symbol
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assignments may be used:
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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>
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<p class="noindent">In this example, the symbol <span class="samp">floating_point</span> will be defined as
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zero. The symbol <span class="samp">_etext</span> will be defined as the address following
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the last <span class="samp">.text</span> input section. The symbol <span class="samp">_bdata</span> will be
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defined as the address following the <span class="samp">.text</span> output section aligned
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upward to a 4 byte boundary.
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</body></html>
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