97 lines
5.0 KiB
HTML
97 lines
5.0 KiB
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<html lang="en">
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<head>
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<title>Enumerations - STABS</title>
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<meta name="description" content="STABS">
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<meta name="generator" content="makeinfo 4.13">
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<link title="Top" rel="start" href="index.html#Top">
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<link rel="up" href="Types.html#Types" title="Types">
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<link rel="prev" href="Strings.html#Strings" title="Strings">
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<link rel="next" href="Structures.html#Structures" title="Structures">
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<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
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<!--
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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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</head>
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<body>
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<div class="node">
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<a name="Enumerations"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="Structures.html#Structures">Structures</a>,
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Previous: <a rel="previous" accesskey="p" href="Strings.html#Strings">Strings</a>,
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Up: <a rel="up" accesskey="u" href="Types.html#Types">Types</a>
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<hr>
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</div>
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<h3 class="section">5.7 Enumerations</h3>
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<p>Enumerations are defined with the ‘<samp><span class="samp">e</span></samp>’ type descriptor.
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<!-- FIXME: Where does this information properly go? Perhaps it is -->
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<!-- redundant with something we already explain. -->
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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>The source line:
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<pre class="example"> enum e_places {first,second=3,last};
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</pre>
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<p class="noindent">generates the following stab:
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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>
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<p>The symbol descriptor (‘<samp><span class="samp">T</span></samp>’) says that the stab describes a
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structure, enumeration, or union tag. The type descriptor ‘<samp><span class="samp">e</span></samp>’,
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following the ‘<samp><span class="samp">22=</span></samp>’ of the type definition narrows it down to an
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enumeration type. Following the ‘<samp><span class="samp">e</span></samp>’ is a list of the elements of
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the enumeration. The format is ‘<samp><var>name</var><span class="samp">:</span><var>value</var><span class="samp">,</span></samp>’. The
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list of elements ends with ‘<samp><span class="samp">;</span></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>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>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><span class="samp">T</span></samp>’ or
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‘<samp><span class="samp">t</span></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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</body></html>
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