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diff --git a/share/doc/stabs/Unions.html b/share/doc/stabs/Unions.html new file mode 100644 index 0000000..cf4563d --- /dev/null +++ b/share/doc/stabs/Unions.html @@ -0,0 +1,118 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> +<html> +<!-- Copyright (C) 1992-2023 Free Software Foundation, Inc. +Contributed by Cygnus Support. Written by Julia Menapace, Jim Kingdon, +and David MacKenzie. + +Permission is granted to copy, distribute and/or modify this document +under the terms of the GNU Free Documentation License, Version 1.3 or +any later version published by the Free Software Foundation; with no +Invariant Sections, with no Front-Cover Texts, and with no Back-Cover +Texts. A copy of the license is included in the section entitled "GNU +Free Documentation License". --> +<!-- Created by GNU Texinfo 5.1, http://www.gnu.org/software/texinfo/ --> +<head> +<title>STABS: Unions</title> + +<meta name="description" content="STABS: Unions"> +<meta name="keywords" content="STABS: Unions"> +<meta name="resource-type" content="document"> +<meta name="distribution" content="global"> +<meta name="Generator" content="makeinfo"> +<meta http-equiv="Content-Type" content="text/html; charset=utf-8"> +<link href="index.html#Top" rel="start" title="Top"> +<link href="Symbol-Types-Index.html#Symbol-Types-Index" rel="index" title="Symbol Types Index"> +<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> +<link href="Types.html#Types" rel="up" title="Types"> +<link href="Function-Types.html#Function-Types" rel="next" title="Function Types"> +<link href="Typedefs.html#Typedefs" rel="previous" title="Typedefs"> +<style type="text/css"> +<!-- +a.summary-letter {text-decoration: none} +blockquote.smallquotation {font-size: smaller} +div.display {margin-left: 3.2em} +div.example {margin-left: 3.2em} +div.indentedblock {margin-left: 3.2em} +div.lisp {margin-left: 3.2em} +div.smalldisplay {margin-left: 3.2em} +div.smallexample {margin-left: 3.2em} +div.smallindentedblock {margin-left: 3.2em; font-size: smaller} +div.smalllisp {margin-left: 3.2em} +kbd {font-style:oblique} +pre.display {font-family: inherit} +pre.format {font-family: inherit} +pre.menu-comment {font-family: serif} +pre.menu-preformatted {font-family: serif} +pre.smalldisplay {font-family: inherit; font-size: smaller} +pre.smallexample {font-size: smaller} +pre.smallformat {font-family: inherit; font-size: smaller} +pre.smalllisp {font-size: smaller} +span.nocodebreak {white-space:nowrap} +span.nolinebreak {white-space:nowrap} +span.roman {font-family:serif; font-weight:normal} +span.sansserif {font-family:sans-serif; font-weight:normal} +ul.no-bullet {list-style: none} +--> +</style> + + +</head> + +<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000"> +<a name="Unions"></a> +<div class="header"> +<p> +Next: <a href="Function-Types.html#Function-Types" accesskey="n" rel="next">Function Types</a>, Previous: <a href="Typedefs.html#Typedefs" accesskey="p" rel="previous">Typedefs</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> +</div> +<hr> +<a name="Unions-1"></a> +<h3 class="section">5.10 Unions</h3> + +<div class="example"> +<pre class="example">union u_tag { + int u_int; + float u_float; + char* u_char; +} an_u; +</pre></div> + +<p>This code generates a stab for a union tag and a stab for a union +variable. Both use the <code>N_LSYM</code> stab type. If a union variable is +scoped locally to the procedure in which it is defined, its stab is +located immediately preceding the <code>N_LBRAC</code> for the procedure’s block +start. +</p> +<p>The stab for the union tag, however, is located preceding the code for +the procedure in which it is defined. The stab type is <code>N_LSYM</code>. This +would seem to imply that the union type is file scope, like the struct +type <code>s_tag</code>. This is not true. The contents and position of the stab +for <code>u_type</code> do not convey any information about its procedure local +scope. +</p> +<div class="smallexample"> +<pre class="smallexample"># <span class="roman">128 is N_LSYM</span> +.stabs "u_tag:T23=u4u_int:1,0,32;u_float:12,0,32;u_char:21,0,32;;", + 128,0,0,0 +</pre></div> + +<p>The symbol descriptor ‘<samp>T</samp>’, following the ‘<samp>name:</samp>’ means that +the stab describes an enumeration, structure, or union tag. The type +descriptor ‘<samp>u</samp>’, following the ‘<samp>23=</samp>’ of the type definition, +narrows it down to a union type definition. Following the ‘<samp>u</samp>’ is +the number of bytes in the union. After that is a list of union element +descriptions. Their format is ‘<samp><var>name</var>:<var>type</var>, <var>bit +offset into the union</var>, <var>number of bytes for the element</var>;</samp>’. +</p> +<p>The stab for the union variable is: +</p> +<div class="example"> +<pre class="example">.stabs "an_u:23",128,0,0,-20 # <span class="roman">128 is N_LSYM</span> +</pre></div> + +<p>‘<samp>-20</samp>’ specifies where the variable is stored (see <a href="Stack-Variables.html#Stack-Variables">Stack Variables</a>). +</p> + + + +</body> +</html> |