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151 lines
7.3 KiB
HTML
151 lines
7.3 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>Constants (STABS)</title>
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<meta name="description" content="Constants (STABS)">
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<meta name="keywords" content="Constants (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="index.html#Top" rel="up" title="Top">
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<link href="Variables.html#Variables" rel="next" title="Variables">
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<link href="Alternate-Entry-Points.html#Alternate-Entry-Points" rel="prev" title="Alternate Entry Points">
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<style type="text/css">
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a.summary-letter {text-decoration: 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="Constants"></a>
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<div class="header">
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<p>
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Next: <a href="Variables.html#Variables" accesskey="n" rel="next">Variables</a>, Previous: <a href="Program-Structure.html#Program-Structure" accesskey="p" rel="prev">Program Structure</a>, Up: <a href="index.html#Top" accesskey="u" rel="up">Top</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="Constants-1"></a>
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<h2 class="chapter">3 Constants</h2>
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<p>The ‘<samp>c</samp>’ symbol descriptor indicates that this stab represents a
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constant. This symbol descriptor is an exception to the general rule
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that symbol descriptors are followed by type information. Instead, it
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is followed by ‘<samp>=</samp>’ and one of the following:
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</p>
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<dl compact="compact">
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<dt><code>b <var>value</var></code></dt>
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<dd><p>Boolean constant. <var>value</var> is a numeric value; I assume it is 0 for
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false or 1 for true.
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</p>
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</dd>
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<dt><code>c <var>value</var></code></dt>
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<dd><p>Character constant. <var>value</var> is the numeric value of the constant.
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</p>
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</dd>
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<dt><code>e <var>type-information</var> , <var>value</var></code></dt>
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<dd><p>Constant whose value can be represented as integral.
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<var>type-information</var> is the type of the constant, as it would appear
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after a symbol descriptor (see <a href="String-Field.html#String-Field">String Field</a>). <var>value</var> is the
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numeric value of the constant. GDB 4.9 does not actually get the right
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value if <var>value</var> does not fit in a host <code>int</code>, but it does not
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do anything violent, and future debuggers could be extended to accept
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integers of any size (whether unsigned or not). This constant type is
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usually documented as being only for enumeration constants, but GDB has
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never imposed that restriction; I don’t know about other debuggers.
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</p>
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</dd>
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<dt><code>i <var>value</var></code></dt>
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<dd><p>Integer constant. <var>value</var> is the numeric value. The type is some
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sort of generic integer type (for GDB, a host <code>int</code>); to specify
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the type explicitly, use ‘<samp>e</samp>’ instead.
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</p>
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</dd>
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<dt><code>r <var>value</var></code></dt>
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<dd><p>Real constant. <var>value</var> is the real value, which can be ‘<samp>INF</samp>’
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(optionally preceded by a sign) for infinity, ‘<samp>QNAN</samp>’ for a quiet
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NaN (not-a-number), or ‘<samp>SNAN</samp>’ for a signalling NaN. If it is a
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normal number the format is that accepted by the C library function
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<code>atof</code>.
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</p>
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</dd>
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<dt><code>s <var>string</var></code></dt>
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<dd><p>String constant. <var>string</var> is a string enclosed in either ‘<samp>'</samp>’
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(in which case ‘<samp>'</samp>’ characters within the string are represented as
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‘<samp>\'</samp>’ or ‘<samp>"</samp>’ (in which case ‘<samp>"</samp>’ characters within the
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string are represented as ‘<samp>\"</samp>’).
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</p>
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</dd>
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<dt><code>S <var>type-information</var> , <var>elements</var> , <var>bits</var> , <var>pattern</var></code></dt>
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<dd><p>Set constant. <var>type-information</var> is the type of the constant, as it
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would appear after a symbol descriptor (see <a href="String-Field.html#String-Field">String Field</a>).
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<var>elements</var> is the number of elements in the set (does this means
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how many bits of <var>pattern</var> are actually used, which would be
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redundant with the type, or perhaps the number of bits set in
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<var>pattern</var>? I don’t get it), <var>bits</var> is the number of bits in the
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constant (meaning it specifies the length of <var>pattern</var>, I think),
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and <var>pattern</var> is a hexadecimal representation of the set. AIX
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documentation refers to a limit of 32 bytes, but I see no reason why
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this limit should exist. This form could probably be used for arbitrary
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constants, not just sets; the only catch is that <var>pattern</var> should be
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understood to be target, not host, byte order and format.
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</p></dd>
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</dl>
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<p>The boolean, character, string, and set constants are not supported by
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GDB 4.9, but it ignores them. GDB 4.8 and earlier gave an error
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message and refused to read symbols from the file containing the
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constants.
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</p>
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<p>The above information is followed by ‘<samp>;</samp>’.
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</p>
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<hr>
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<div class="header">
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<p>
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Next: <a href="Variables.html#Variables" accesskey="n" rel="next">Variables</a>, Previous: <a href="Program-Structure.html#Program-Structure" accesskey="p" rel="prev">Program Structure</a>, Up: <a href="index.html#Top" accesskey="u" rel="up">Top</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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</body>
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</html>
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