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106 lines
5.2 KiB
HTML
106 lines
5.2 KiB
HTML
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<html>
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Contributed by Cygnus Support. Written by Julia Menapace, Jim Kingdon,
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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 or
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<head>
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<title>Transformations On Symbol Tables (STABS)</title>
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<meta name="description" content="Transformations On Symbol Tables (STABS)">
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<link href="index.html#Top" rel="start" title="Top">
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<link href="Symbol-Types-Index.html#Symbol-Types-Index" rel="index" title="Symbol Types Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Symbol-Tables.html#Symbol-Tables" rel="up" title="Symbol Tables">
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<link href="Transformations-On-Static-Variables.html#Transformations-On-Static-Variables" rel="next" title="Transformations On Static Variables">
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<link href="Symbol-Table-Format.html#Symbol-Table-Format" rel="prev" title="Symbol Table Format">
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<a name="Transformations-On-Symbol-Tables"></a>
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<div class="header">
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<p>
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Previous: <a href="Symbol-Table-Format.html#Symbol-Table-Format" accesskey="p" rel="prev">Symbol Table Format</a>, Up: <a href="Symbol-Tables.html#Symbol-Tables" accesskey="u" rel="up">Symbol Tables</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Symbol-Types-Index.html#Symbol-Types-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="Transformations-on-Symbol-Tables"></a>
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<h3 class="section">7.2 Transformations on Symbol Tables</h3>
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<p>The linker concatenates object files and does fixups of externally
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defined symbols.
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</p>
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<p>You can see the transformations made on stab data by the assembler and
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linker by examining the symbol table after each pass of the build. To
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do this, use ‘<samp>nm -ap</samp>’, which dumps the symbol table, including
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debugging information, unsorted. For stab entries the columns are:
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<var>value</var>, <var>other</var>, <var>desc</var>, <var>type</var>, <var>string</var>. For
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assembler and linker symbols, the columns are: <var>value</var>, <var>type</var>,
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<var>string</var>.
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</p>
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<p>The low 5 bits of the stab type tell the linker how to relocate the
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value of the stab. Thus for stab types like <code>N_RSYM</code> and
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<code>N_LSYM</code>, where the value is an offset or a register number, the
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low 5 bits are <code>N_ABS</code>, which tells the linker not to relocate the
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value.
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</p>
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<p>Where the value of a stab contains an assembly language label,
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it is transformed by each build step. The assembler turns it into a
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relocatable address and the linker turns it into an absolute address.
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</p>
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<table class="menu" border="0" cellspacing="0">
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<tr><td align="left" valign="top">• <a href="Transformations-On-Static-Variables.html#Transformations-On-Static-Variables" accesskey="1">Transformations On Static Variables</a>:</td><td> </td><td align="left" valign="top">
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</td></tr>
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<tr><td align="left" valign="top">• <a href="Transformations-On-Global-Variables.html#Transformations-On-Global-Variables" accesskey="2">Transformations On Global Variables</a>:</td><td> </td><td align="left" valign="top">
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</td></tr>
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<tr><td align="left" valign="top">• <a href="Stab-Section-Transformations.html#Stab-Section-Transformations" accesskey="3">Stab Section Transformations</a>:</td><td> </td><td align="left" valign="top">For some object file formats,
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things are a bit different.
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</td></tr>
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</table>
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</body>
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</html>
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