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<h2 class="appendix">Appendix A MRI Compatible Script Files</h2>
<p><a name="index-MRI-compatibility-806"></a>To aid users making the transition to <span class="sc">gnu</span> <samp><span class="command">ld</span></samp> from the MRI
linker, <samp><span class="command">ld</span></samp> can use MRI compatible linker scripts as an
alternative to the more general-purpose linker scripting language
described in <a href="Scripts.html#Scripts">Scripts</a>. MRI compatible linker scripts have a much
simpler command set than the scripting language otherwise used with
<samp><span class="command">ld</span></samp>. <span class="sc">gnu</span> <samp><span class="command">ld</span></samp> supports the most commonly used MRI
linker commands; these commands are described here.
<p>In general, MRI scripts aren't of much use with the <code>a.out</code> object
file format, since it only has three sections and MRI scripts lack some
features to make use of them.
<p>You can specify a file containing an MRI-compatible script using the
&lsquo;<samp><span class="samp">-c</span></samp>&rsquo; command-line option.
<p>Each command in an MRI-compatible script occupies its own line; each
command line starts with the keyword that identifies the command (though
blank lines are also allowed for punctuation). If a line of an
MRI-compatible script begins with an unrecognized keyword, <samp><span class="command">ld</span></samp>
issues a warning message, but continues processing the script.
<p>Lines beginning with &lsquo;<samp><span class="samp">*</span></samp>&rsquo; are comments.
<p>You can write these commands using all upper-case letters, or all
lower case; for example, &lsquo;<samp><span class="samp">chip</span></samp>&rsquo; is the same as &lsquo;<samp><span class="samp">CHIP</span></samp>&rsquo;.
The following list shows only the upper-case form of each command.
<a name="index-g_t_0040code_007bABSOLUTE_007d-_0028MRI_0029-807"></a>
<dl><dt><code>ABSOLUTE </code><var>secname</var><dt><code>ABSOLUTE </code><var>secname</var><code>, </code><var>secname</var><code>, ... </code><var>secname</var><dd>Normally, <samp><span class="command">ld</span></samp> includes in the output file all sections from all
the input files. However, in an MRI-compatible script, you can use the
<code>ABSOLUTE</code> command to restrict the sections that will be present in
your output program. If the <code>ABSOLUTE</code> command is used at all in a
script, then only the sections named explicitly in <code>ABSOLUTE</code>
commands will appear in the linker output. You can still use other
input sections (whatever you select on the command line, or using
<code>LOAD</code>) to resolve addresses in the output file.
<p><a name="index-g_t_0040code_007bALIAS_007d-_0028MRI_0029-808"></a><br><dt><code>ALIAS </code><var>out-secname</var><code>, </code><var>in-secname</var><dd>Use this command to place the data from input section <var>in-secname</var>
in a section called <var>out-secname</var> in the linker output file.
<p><var>in-secname</var> may be an integer.
<p><a name="index-g_t_0040code_007bALIGN_007d-_0028MRI_0029-809"></a><br><dt><code>ALIGN </code><var>secname</var><code> = </code><var>expression</var><dd>Align the section called <var>secname</var> to <var>expression</var>. The
<var>expression</var> should be a power of two.
<p><a name="index-g_t_0040code_007bBASE_007d-_0028MRI_0029-810"></a><br><dt><code>BASE </code><var>expression</var><dd>Use the value of <var>expression</var> as the lowest address (other than
absolute addresses) in the output file.
<p><a name="index-g_t_0040code_007bCHIP_007d-_0028MRI_0029-811"></a><br><dt><code>CHIP </code><var>expression</var><dt><code>CHIP </code><var>expression</var><code>, </code><var>expression</var><dd>This command does nothing; it is accepted only for compatibility.
<p><a name="index-g_t_0040code_007bEND_007d-_0028MRI_0029-812"></a><br><dt><code>END</code><dd>This command does nothing whatever; it's only accepted for compatibility.
<p><a name="index-g_t_0040code_007bFORMAT_007d-_0028MRI_0029-813"></a><br><dt><code>FORMAT </code><var>output-format</var><dd>Similar to the <code>OUTPUT_FORMAT</code> command in the more general linker
language, but restricted to S-records, if <var>output-format</var> is &lsquo;<samp><span class="samp">S</span></samp>&rsquo;
<p><a name="index-g_t_0040code_007bLIST_007d-_0028MRI_0029-814"></a><br><dt><code>LIST </code><var>anything</var><code>...</code><dd>Print (to the standard output file) a link map, as produced by the
<samp><span class="command">ld</span></samp> command-line option &lsquo;<samp><span class="samp">-M</span></samp>&rsquo;.
<p>The keyword <code>LIST</code> may be followed by anything on the
same line, with no change in its effect.
<p><a name="index-g_t_0040code_007bLOAD_007d-_0028MRI_0029-815"></a><br><dt><code>LOAD </code><var>filename</var><dt><code>LOAD </code><var>filename</var><code>, </code><var>filename</var><code>, ... </code><var>filename</var><dd>Include one or more object file <var>filename</var> in the link; this has the
same effect as specifying <var>filename</var> directly on the <samp><span class="command">ld</span></samp>
command line.
<p><a name="index-g_t_0040code_007bNAME_007d-_0028MRI_0029-816"></a><br><dt><code>NAME </code><var>output-name</var><dd><var>output-name</var> is the name for the program produced by <samp><span class="command">ld</span></samp>; the
MRI-compatible command <code>NAME</code> is equivalent to the command-line
option &lsquo;<samp><span class="samp">-o</span></samp>&rsquo; or the general script language command <code>OUTPUT</code>.
<p><a name="index-g_t_0040code_007bORDER_007d-_0028MRI_0029-817"></a><br><dt><code>ORDER </code><var>secname</var><code>, </code><var>secname</var><code>, ... </code><var>secname</var><dt><code>ORDER </code><var>secname</var> <var>secname</var> <var>secname</var><dd>Normally, <samp><span class="command">ld</span></samp> orders the sections in its output file in the
order in which they first appear in the input files. In an MRI-compatible
script, you can override this ordering with the <code>ORDER</code> command. The
sections you list with <code>ORDER</code> will appear first in your output
file, in the order specified.
<p><a name="index-g_t_0040code_007bPUBLIC_007d-_0028MRI_0029-818"></a><br><dt><code>PUBLIC </code><var>name</var><code>=</code><var>expression</var><dt><code>PUBLIC </code><var>name</var><code>,</code><var>expression</var><dt><code>PUBLIC </code><var>name</var> <var>expression</var><dd>Supply a value (<var>expression</var>) for external symbol
<var>name</var> used in the linker input files.
<p><a name="index-g_t_0040code_007bSECT_007d-_0028MRI_0029-819"></a><br><dt><code>SECT </code><var>secname</var><code>, </code><var>expression</var><dt><code>SECT </code><var>secname</var><code>=</code><var>expression</var><dt><code>SECT </code><var>secname</var> <var>expression</var><dd>You can use any of these three forms of the <code>SECT</code> command to
specify the start address (<var>expression</var>) for section <var>secname</var>.
If you have more than one <code>SECT</code> statement for the same
<var>secname</var>, only the <em>first</em> sets the start address.
</dl>
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