80 lines
4.2 KiB
HTML
80 lines
4.2 KiB
HTML
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<html lang="en">
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<title>Block Structure - 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="Nested-Procedures.html#Nested-Procedures" title="Nested Procedures">
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<link rel="next" href="Alternate-Entry-Points.html#Alternate-Entry-Points" title="Alternate Entry Points">
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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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<a name="Block-Structure"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="Alternate-Entry-Points.html#Alternate-Entry-Points">Alternate Entry Points</a>,
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Previous: <a rel="previous" accesskey="p" href="Nested-Procedures.html#Nested-Procedures">Nested Procedures</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">2.7 Block Structure</h3>
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<p><a name="index-N_005fLBRAC-18"></a><a name="index-N_005fRBRAC-19"></a><!-- For GCC 2.5.8 or so stabs-in-coff, these are absolute instead of -->
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<!-- function relative (as documented below). But GDB has never been able -->
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<!-- to deal with that (it had wanted them to be relative to the file, but -->
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<!-- I just fixed that (between GDB 4.12 and 4.13)), so it is function -->
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<!-- relative just like ELF and SOM and the below documentation. -->
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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>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>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><a name="index-g_t_002ebb-20"></a><a name="index-g_t_002ebe-21"></a><a name="index-C_005fBLOCK-22"></a>For XCOFF, block scope is indicated with <code>C_BLOCK</code> symbols. If the
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name of the symbol is ‘<samp><span class="samp">.bb</span></samp>’, then it is the beginning of the block;
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if the name of the symbol is ‘<samp><span class="samp">.be</span></samp>’; it is the end of the block.
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</body></html>
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