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129 lines
6.2 KiB
HTML
129 lines
6.2 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>Enumerations (STABS)</title>
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<meta name="description" content="Enumerations (STABS)">
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<meta name="keywords" content="Enumerations (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="Types.html#Types" rel="up" title="Types">
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<link href="Structures.html#Structures" rel="next" title="Structures">
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<link href="Strings.html#Strings" rel="prev" title="Strings">
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<style type="text/css">
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<!--
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a.summary-letter {text-decoration: none}
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blockquote.indentedblock {margin-right: 0em}
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blockquote.smallindentedblock {margin-right: 0em; font-size: smaller}
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blockquote.smallquotation {font-size: smaller}
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div.display {margin-left: 3.2em}
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div.example {margin-left: 3.2em}
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div.lisp {margin-left: 3.2em}
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div.smalldisplay {margin-left: 3.2em}
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div.smallexample {margin-left: 3.2em}
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div.smalllisp {margin-left: 3.2em}
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kbd {font-style: oblique}
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pre.display {font-family: inherit}
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pre.format {font-family: inherit}
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pre.menu-comment {font-family: serif}
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pre.menu-preformatted {font-family: serif}
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pre.smalldisplay {font-family: inherit; font-size: smaller}
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pre.smallexample {font-size: smaller}
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pre.smallformat {font-family: inherit; font-size: smaller}
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pre.smalllisp {font-size: smaller}
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span.nolinebreak {white-space: nowrap}
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span.roman {font-family: initial; 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">
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<a name="Enumerations"></a>
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<div class="header">
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<p>
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Next: <a href="Structures.html#Structures" accesskey="n" rel="next">Structures</a>, Previous: <a href="Strings.html#Strings" accesskey="p" rel="prev">Strings</a>, Up: <a href="Types.html#Types" accesskey="u" rel="up">Types</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="Enumerations-1"></a>
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<h3 class="section">5.7 Enumerations</h3>
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<p>Enumerations are defined with the ‘<samp>e</samp>’ type descriptor.
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</p>
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<p>The source line below declares an enumeration type at file scope.
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The type definition is located after the <code>N_RBRAC</code> that marks the end of
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the previous procedure’s block scope, and before the <code>N_FUN</code> that marks
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the beginning of the next procedure’s block scope. Therefore it does not
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describe a block local symbol, but a file local one.
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</p>
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<p>The source line:
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</p>
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<div class="example">
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<pre class="example">enum e_places {first,second=3,last};
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</pre></div>
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<p>generates the following stab:
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</p>
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<div class="example">
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<pre class="example">.stabs "e_places:T22=efirst:0,second:3,last:4,;",128,0,0,0
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</pre></div>
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<p>The symbol descriptor (‘<samp>T</samp>’) says that the stab describes a
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structure, enumeration, or union tag. The type descriptor ‘<samp>e</samp>’,
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following the ‘<samp>22=</samp>’ of the type definition narrows it down to an
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enumeration type. Following the ‘<samp>e</samp>’ is a list of the elements of
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the enumeration. The format is ‘<samp><var>name</var>:<var>value</var>,</samp>’. The
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list of elements ends with ‘<samp>;</samp>’. The fact that <var>value</var> is
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specified as an integer can cause problems if the value is large. GCC
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2.5.2 tries to output it in octal in that case with a leading zero,
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which is probably a good thing, although GDB 4.11 supports octal only in
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cases where decimal is perfectly good. Negative decimal values are
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supported by both GDB and dbx.
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</p>
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<p>There is no standard way to specify the size of an enumeration type; it
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is determined by the architecture (normally all enumerations types are
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32 bits). Type attributes can be used to specify an enumeration type of
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another size for debuggers which support them; see <a href="String-Field.html#String-Field">String Field</a>.
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</p>
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<p>Enumeration types are unusual in that they define symbols for the
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enumeration values (<code>first</code>, <code>second</code>, and <code>third</code> in the
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above example), and even though these symbols are visible in the file as
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a whole (rather than being in a more local namespace like structure
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member names), they are defined in the type definition for the
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enumeration type rather than each having their own symbol. In order to
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be fast, GDB will only get symbols from such types (in its initial scan
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of the stabs) if the type is the first thing defined after a ‘<samp>T</samp>’ or
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‘<samp>t</samp>’ symbol descriptor (the above example fulfills this
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requirement). If the type does not have a name, the compiler should
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emit it in a nameless stab (see <a href="String-Field.html#String-Field">String Field</a>); GCC does this.
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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="Structures.html#Structures" accesskey="n" rel="next">Structures</a>, Previous: <a href="Strings.html#Strings" accesskey="p" rel="prev">Strings</a>, Up: <a href="Types.html#Types" accesskey="u" rel="up">Types</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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