104 lines
4.9 KiB
HTML
104 lines
4.9 KiB
HTML
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<!-- Copyright (C) 1992-2017 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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<!-- Created by GNU Texinfo 5.2, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>STABS: Line Numbers</title>
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<meta name="description" content="STABS: Line Numbers">
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<meta name="keywords" content="STABS: Line Numbers">
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<meta name="resource-type" content="document">
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<meta name="distribution" content="global">
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<meta name="Generator" content="makeinfo">
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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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="Program-Structure.html#Program-Structure" rel="up" title="Program Structure">
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<link href="Procedures.html#Procedures" rel="next" title="Procedures">
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<link href="Include-Files.html#Include-Files" rel="prev" title="Include Files">
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<style type="text/css">
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<!--
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pre.smalllisp {font-size: smaller}
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span.nocodebreak {white-space:nowrap}
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span.nolinebreak {white-space:nowrap}
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span.roman {font-family:serif; font-weight:normal}
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span.sansserif {font-family:sans-serif; font-weight:normal}
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ul.no-bullet {list-style: none}
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-->
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</style>
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</head>
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<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
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<a name="Line-Numbers"></a>
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<div class="header">
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<p>
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Next: <a href="Procedures.html#Procedures" accesskey="n" rel="next">Procedures</a>, Previous: <a href="Include-Files.html#Include-Files" accesskey="p" rel="prev">Include Files</a>, Up: <a href="Program-Structure.html#Program-Structure" accesskey="u" rel="up">Program Structure</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="Line-Numbers-1"></a>
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<h3 class="section">2.4 Line Numbers</h3>
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<a name="index-N_005fSLINE"></a>
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<p>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>
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<a name="index-N_005fDSLINE"></a>
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<a name="index-N_005fBSLINE"></a>
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<p>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>
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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>
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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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</p>
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</body>
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</html>
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