101 lines
4.7 KiB
HTML
101 lines
4.7 KiB
HTML
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<title>Stab - Using as</title>
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<!--
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This file documents the GNU Assembler "as".
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Copyright (C) 1991-2019 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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with no Invariant Sections, with no Front-Cover Texts, and with no
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</head>
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<body>
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<div class="node">
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<a name="Stab"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="String.html#String">String</a>,
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Previous: <a rel="previous" accesskey="p" href="Space.html#Space">Space</a>,
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Up: <a rel="up" accesskey="u" href="Pseudo-Ops.html#Pseudo-Ops">Pseudo Ops</a>
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</div>
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<h3 class="section">7.90 <code>.stabd, .stabn, .stabs</code></h3>
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<p><a name="index-symbolic-debuggers_002c-information-for-477"></a><a name="index-g_t_0040code_007bstab_0040var_007bx_007d_007d-directives-478"></a>There are three directives that begin ‘<samp><span class="samp">.stab</span></samp>’.
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All emit symbols (see <a href="Symbols.html#Symbols">Symbols</a>), for use by symbolic debuggers.
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The symbols are not entered in the <samp><span class="command">as</span></samp> hash table: they
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cannot be referenced elsewhere in the source file.
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Up to five fields are required:
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<dl>
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<dt><var>string</var><dd>This is the symbol's name. It may contain any character except
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‘<samp><span class="samp">\000</span></samp>’, so is more general than ordinary symbol names. Some
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debuggers used to code arbitrarily complex structures into symbol names
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using this field.
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<br><dt><var>type</var><dd>An absolute expression. The symbol's type is set to the low 8 bits of
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this expression. Any bit pattern is permitted, but <code>ld</code>
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and debuggers choke on silly bit patterns.
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<br><dt><var>other</var><dd>An absolute expression. The symbol's “other” attribute is set to the
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low 8 bits of this expression.
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<br><dt><var>desc</var><dd>An absolute expression. The symbol's descriptor is set to the low 16
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bits of this expression.
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<br><dt><var>value</var><dd>An absolute expression which becomes the symbol's value.
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</dl>
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<p>If a warning is detected while reading a <code>.stabd</code>, <code>.stabn</code>,
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or <code>.stabs</code> statement, the symbol has probably already been created;
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you get a half-formed symbol in your object file. This is
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compatible with earlier assemblers!
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<a name="index-g_t_0040code_007bstabd_007d-directive-479"></a>
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<dl><dt><code>.stabd </code><var>type</var><code> , </code><var>other</var><code> , </code><var>desc</var><dd>
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The “name” of the symbol generated is not even an empty string.
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It is a null pointer, for compatibility. Older assemblers used a
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null pointer so they didn't waste space in object files with empty
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strings.
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<p>The symbol's value is set to the location counter,
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relocatably. When your program is linked, the value of this symbol
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is the address of the location counter when the <code>.stabd</code> was
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assembled.
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<p><a name="index-g_t_0040code_007bstabn_007d-directive-480"></a><br><dt><code>.stabn </code><var>type</var><code> , </code><var>other</var><code> , </code><var>desc</var><code> , </code><var>value</var><dd>The name of the symbol is set to the empty string <code>""</code>.
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<p><a name="index-g_t_0040code_007bstabs_007d-directive-481"></a><br><dt><code>.stabs </code><var>string</var><code> , </code><var>type</var><code> , </code><var>other</var><code> , </code><var>desc</var><code> , </code><var>value</var><dd>All five fields are specified.
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</dl>
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<!-- end have-stabs -->
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</body></html>
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