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78 lines
3.4 KiB
HTML
78 lines
3.4 KiB
HTML
15 years ago
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<html lang="en">
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<head>
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<title>PROVIDE - 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="prev" href="Simple-Assignments.html#Simple-Assignments" title="Simple Assignments">
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<link rel="next" href="PROVIDE_005fHIDDEN.html#PROVIDE_005fHIDDEN" title="PROVIDE_HIDDEN">
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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="PROVIDE"></a>Next: <a rel="next" accesskey="n" href="PROVIDE_005fHIDDEN.html#PROVIDE_005fHIDDEN">PROVIDE_HIDDEN</a>,
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Previous: <a rel="previous" accesskey="p" href="Simple-Assignments.html#Simple-Assignments">Simple Assignments</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">3.5.2 PROVIDE</h4>
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<p><a name="index-PROVIDE-359"></a>In some cases, it is desirable for a linker script to define a symbol
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only if it is referenced and is not defined by any object included in
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the link. For example, traditional linkers defined the symbol
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<span class="samp">etext</span>. However, ANSI C requires that the user be able to use
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<span class="samp">etext</span> as a function name without encountering an error. The
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<code>PROVIDE</code> keyword may be used to define a symbol, such as
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<span class="samp">etext</span>, only if it is referenced but not defined. The syntax is
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<code>PROVIDE(</code><var>symbol</var><code> = </code><var>expression</var><code>)</code>.
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<p>Here is an example of using <code>PROVIDE</code> to define <span class="samp">etext</span>:
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<pre class="smallexample"> 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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PROVIDE(etext = .);
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}
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}
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</pre>
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<p>In this example, if the program defines <span class="samp">_etext</span> (with a leading
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underscore), the linker will give a multiple definition error. If, on
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the other hand, the program defines <span class="samp">etext</span> (with no leading
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underscore), the linker will silently use the definition in the program.
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If the program references <span class="samp">etext</span> but does not define it, the
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linker will use the definition in the linker script.
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</body></html>
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