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105 lines
4.9 KiB
HTML
105 lines
4.9 KiB
HTML
4 years ago
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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) 1992-2019 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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<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>Block Structure (STABS)</title>
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<meta name="description" content="Block Structure (STABS)">
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<meta name="keywords" content="Block Structure (STABS)">
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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="Alternate-Entry-Points.html#Alternate-Entry-Points" rel="next" title="Alternate Entry Points">
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<link href="Nested-Procedures.html#Nested-Procedures" rel="prev" title="Nested Procedures">
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<style type="text/css">
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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">
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<a name="Block-Structure"></a>
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<div class="header">
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<p>
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Next: <a href="Alternate-Entry-Points.html#Alternate-Entry-Points" accesskey="n" rel="next">Alternate Entry Points</a>, Previous: <a href="Nested-Procedures.html#Nested-Procedures" accesskey="p" rel="prev">Nested Procedures</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="Block-Structure-1"></a>
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<h3 class="section">2.7 Block Structure</h3>
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<a name="index-N_005fLBRAC"></a>
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<a name="index-N_005fRBRAC"></a>
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<p>The program’s block structure is represented by the <code>N_LBRAC</code> (left
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brace) and the <code>N_RBRAC</code> (right brace) stab types. The variables
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defined inside a block precede the <code>N_LBRAC</code> symbol for most
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compilers, including GCC. Other compilers, such as the Convex, Acorn
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RISC machine, and Sun <code>acc</code> compilers, put the variables after the
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<code>N_LBRAC</code> symbol. The values of the <code>N_LBRAC</code> and
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<code>N_RBRAC</code> symbols are the start and end addresses of the code of
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the block, respectively. For most machines, they are relative to the
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starting address of this source file. For the Gould NP1, they are
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absolute. For stabs in sections (see <a href="Stab-Sections.html#Stab-Sections">Stab Sections</a>), they are
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relative to the function in which they occur.
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</p>
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<p>The <code>N_LBRAC</code> and <code>N_RBRAC</code> stabs that describe the block
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scope of a procedure are located after the <code>N_FUN</code> stab that
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represents the procedure itself.
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</p>
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<p>Sun documents the desc field of <code>N_LBRAC</code> and
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<code>N_RBRAC</code> symbols as containing the nesting level of the block.
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However, dbx seems to not care, and GCC always sets desc to
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zero.
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</p>
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<a name="index-_002ebb"></a>
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<a name="index-_002ebe"></a>
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<a name="index-C_005fBLOCK"></a>
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<p>For XCOFF, block scope is indicated with <code>C_BLOCK</code> symbols. If the
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name of the symbol is ‘<samp>.bb</samp>’, then it is the beginning of the block;
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if the name of the symbol is ‘<samp>.be</samp>’; it is the end of the block.
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</p>
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</body>
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</html>
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