76 lines
3.6 KiB
HTML
76 lines
3.6 KiB
HTML
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<html lang="en">
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<head>
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<title>Transformations On Symbol Tables - STABS</title>
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<meta http-equiv="Content-Type" content="text/html">
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<meta name="description" content="STABS">
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<meta name="generator" content="makeinfo 4.13">
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<link title="Top" rel="start" href="index.html#Top">
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<link rel="up" href="Symbol-Tables.html#Symbol-Tables" title="Symbol Tables">
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<link rel="prev" href="Symbol-Table-Format.html#Symbol-Table-Format" title="Symbol Table Format">
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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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Copyright (C) 1992-2019 Free Software Foundation, Inc.
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Contributed by Cygnus Support. Written by Julia Menapace, Jim Kingdon,
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and David MacKenzie.
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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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any later version published by the Free Software Foundation; with no
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Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
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Texts. A copy of the license is included in the section entitled ``GNU
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Free Documentation License''.-->
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</head>
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<body>
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<div class="node">
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<a name="Transformations-On-Symbol-Tables"></a>
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<p>
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Previous: <a rel="previous" accesskey="p" href="Symbol-Table-Format.html#Symbol-Table-Format">Symbol Table Format</a>,
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Up: <a rel="up" accesskey="u" href="Symbol-Tables.html#Symbol-Tables">Symbol Tables</a>
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<hr>
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</div>
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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>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><span class="samp">nm -ap</span></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>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>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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<ul class="menu">
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<li><a accesskey="1" href="Transformations-On-Static-Variables.html#Transformations-On-Static-Variables">Transformations On Static Variables</a>
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<li><a accesskey="2" href="Transformations-On-Global-Variables.html#Transformations-On-Global-Variables">Transformations On Global Variables</a>
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<li><a accesskey="3" href="Stab-Section-Transformations.html#Stab-Section-Transformations">Stab Section Transformations</a>: For some object file formats,
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things are a bit different.
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</ul>
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</body></html>
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