75 lines
3.7 KiB
HTML
75 lines
3.7 KiB
HTML
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<html lang="en">
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<head>
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<title>Line Numbers - STABS</title>
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<meta name="description" content="STABS">
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<link title="Top" rel="start" href="index.html#Top">
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<link rel="up" href="Program-Structure.html#Program-Structure" title="Program Structure">
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<link rel="prev" href="Include-Files.html#Include-Files" title="Include Files">
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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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<body>
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<div class="node">
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<a name="Line-Numbers"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="Procedures.html#Procedures">Procedures</a>,
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Previous: <a rel="previous" accesskey="p" href="Include-Files.html#Include-Files">Include Files</a>,
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Up: <a rel="up" accesskey="u" href="Program-Structure.html#Program-Structure">Program Structure</a>
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<hr>
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</div>
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<h3 class="section">2.4 Line Numbers</h3>
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<p><a name="index-N_005fSLINE-10"></a>An <code>N_SLINE</code> symbol represents the start of a source line. The
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desc field contains the line number and the value contains the code
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address for the start of that source line. On most machines the address
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is absolute; for stabs in sections (see <a href="Stab-Sections.html#Stab-Sections">Stab Sections</a>), it is
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relative to the function in which the <code>N_SLINE</code> symbol occurs.
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<p><a name="index-N_005fDSLINE-11"></a><a name="index-N_005fBSLINE-12"></a>GNU documents <code>N_DSLINE</code> and <code>N_BSLINE</code> symbols for line
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numbers in the data or bss segments, respectively. They are identical
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to <code>N_SLINE</code> but are relocated differently by the linker. They
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were intended to be used to describe the source location of a variable
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declaration, but I believe that GCC2 actually puts the line number in
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the desc field of the stab for the variable itself. GDB has been
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ignoring these symbols (unless they contain a string field) since
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at least GDB 3.5.
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<p>For single source lines that generate discontiguous code, such as flow
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of control statements, there may be more than one line number entry for
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the same source line. In this case there is a line number entry at the
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start of each code range, each with the same line number.
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<p>XCOFF does not use stabs for line numbers. Instead, it uses COFF line
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numbers (which are outside the scope of this document). Standard COFF
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line numbers cannot deal with include files, but in XCOFF this is fixed
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with the <code>C_BINCL</code> method of marking include files (see <a href="Include-Files.html#Include-Files">Include Files</a>).
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</body></html>
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