113 lines
6.6 KiB
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113 lines
6.6 KiB
HTML
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<title>Miscellaneous Commands - Untitled</title>
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<link rel="up" href="Simple-Commands.html#Simple-Commands" title="Simple Commands">
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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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<div class="node">
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<p>
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<a name="Miscellaneous-Commands"></a>Previous: <a rel="previous" accesskey="p" href="Format-Commands.html#Format-Commands">Format Commands</a>,
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Up: <a rel="up" accesskey="u" href="Simple-Commands.html#Simple-Commands">Simple Commands</a>
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<hr><br>
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</div>
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<h4 class="subsection">3.4.4 Other Linker Script Commands</h4>
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<p>There are a few other linker scripts commands.
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<dl>
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<dt><code>ASSERT(</code><var>exp</var><code>, </code><var>message</var><code>)</code><dd><a name="index-ASSERT-341"></a><a name="index-assertion-in-linker-script-342"></a>Ensure that <var>exp</var> is non-zero. If it is zero, then exit the linker
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with an error code, and print <var>message</var>.
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<br><dt><code>EXTERN(</code><var>symbol</var> <var>symbol</var><code> ...)</code><dd><a name="index-EXTERN-343"></a><a name="index-undefined-symbol-in-linker-script-344"></a>Force <var>symbol</var> to be entered in the output file as an undefined
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symbol. Doing this may, for example, trigger linking of additional
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modules from standard libraries. You may list several <var>symbol</var>s for
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each <code>EXTERN</code>, and you may use <code>EXTERN</code> multiple times. This
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command has the same effect as the <span class="samp">-u</span> command-line option.
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<br><dt><code>FORCE_COMMON_ALLOCATION</code><dd><a name="index-FORCE_005fCOMMON_005fALLOCATION-345"></a><a name="index-common-allocation-in-linker-script-346"></a>This command has the same effect as the <span class="samp">-d</span> command-line option:
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to make <span class="command">ld</span> assign space to common symbols even if a relocatable
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output file is specified (<span class="samp">-r</span>).
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<br><dt><code>INHIBIT_COMMON_ALLOCATION</code><dd><a name="index-INHIBIT_005fCOMMON_005fALLOCATION-347"></a><a name="index-common-allocation-in-linker-script-348"></a>This command has the same effect as the <span class="samp">--no-define-common</span>
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command-line option: to make <code>ld</code> omit the assignment of addresses
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to common symbols even for a non-relocatable output file.
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<br><dt><code>INSERT [ AFTER | BEFORE ] </code><var>output_section</var><dd><a name="index-INSERT-349"></a><a name="index-insert-user-script-into-default-script-350"></a>This command is typically used in a script specified by <span class="samp">-T</span> to
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augment the default <code>SECTIONS</code> with, for example, overlays. It
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inserts all prior linker script statements after (or before)
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<var>output_section</var>, and also causes <span class="samp">-T</span> to not override the
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default linker script. The exact insertion point is as for orphan
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sections. See <a href="Location-Counter.html#Location-Counter">Location Counter</a>. The insertion happens after the
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linker has mapped input sections to output sections. Prior to the
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insertion, since <span class="samp">-T</span> scripts are parsed before the default
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linker script, statements in the <span class="samp">-T</span> script occur before the
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default linker script statements in the internal linker representation
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of the script. In particular, input section assignments will be made
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to <span class="samp">-T</span> output sections before those in the default script. Here
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is an example of how a <span class="samp">-T</span> script using <code>INSERT</code> might look:
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<pre class="smallexample"> SECTIONS
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{
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OVERLAY :
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{
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.ov1 { ov1*(.text) }
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.ov2 { ov2*(.text) }
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}
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}
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INSERT AFTER .text;
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</pre>
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<br><dt><code>NOCROSSREFS(</code><var>section</var> <var>section</var><code> ...)</code><dd><a name="index-NOCROSSREFS_0028_0040var_007bsections_007d_0029-351"></a><a name="index-cross-references-352"></a>This command may be used to tell <span class="command">ld</span> to issue an error about any
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references among certain output sections.
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<p>In certain types of programs, particularly on embedded systems when
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using overlays, when one section is loaded into memory, another section
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will not be. Any direct references between the two sections would be
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errors. For example, it would be an error if code in one section called
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a function defined in the other section.
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<p>The <code>NOCROSSREFS</code> command takes a list of output section names. If
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<span class="command">ld</span> detects any cross references between the sections, it reports
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an error and returns a non-zero exit status. Note that the
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<code>NOCROSSREFS</code> command uses output section names, not input section
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names.
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<br><dt><code>OUTPUT_ARCH(</code><var>bfdarch</var><code>)</code><dd><a name="index-OUTPUT_005fARCH_0028_0040var_007bbfdarch_007d_0029-353"></a><a name="index-machine-architecture-354"></a><a name="index-architecture-355"></a>Specify a particular output machine architecture. The argument is one
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of the names used by the BFD library (see <a href="BFD.html#BFD">BFD</a>). You can see the
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architecture of an object file by using the <code>objdump</code> program with
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the <span class="samp">-f</span> option.
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</dl>
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</body></html>
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