136 lines
6.1 KiB
HTML
136 lines
6.1 KiB
HTML
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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) 1992-2017 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 5.2, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>STABS: Parameters</title>
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<meta name="description" content="STABS: Parameters">
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<meta name="keywords" content="STABS: Parameters">
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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="Variables.html#Variables" rel="up" title="Variables">
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<link href="Register-Parameters.html#Register-Parameters" rel="next" title="Register Parameters">
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<link href="Based-Variables.html#Based-Variables" rel="prev" title="Based Variables">
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<style type="text/css">
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a.summary-letter {text-decoration: none}
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span.roman {font-family:serif; font-weight:normal}
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-->
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</style>
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</head>
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<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
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<a name="Parameters"></a>
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<div class="header">
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<p>
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Previous: <a href="Based-Variables.html#Based-Variables" accesskey="p" rel="prev">Based Variables</a>, Up: <a href="Variables.html#Variables" accesskey="u" rel="up">Variables</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="Parameters-1"></a>
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<h3 class="section">4.7 Parameters</h3>
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<p>Formal parameters to a function are represented by a stab (or sometimes
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two; see below) for each parameter. The stabs are in the order in which
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the debugger should print the parameters (i.e., the order in which the
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parameters are declared in the source file). The exact form of the stab
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depends on how the parameter is being passed.
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</p>
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<a name="index-N_005fPSYM"></a>
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<a name="index-C_005fPSYM"></a>
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<p>Parameters passed on the stack use the symbol descriptor ‘<samp>p</samp>’ and
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the <code>N_PSYM</code> symbol type (or <code>C_PSYM</code> for XCOFF). The value
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of the symbol is an offset used to locate the parameter on the stack;
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its exact meaning is machine-dependent, but on most machines it is an
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offset from the frame pointer.
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</p>
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<p>As a simple example, the code:
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</p>
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<div class="example">
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<pre class="example">main (argc, argv)
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int argc;
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char **argv;
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</pre></div>
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<p>produces the stabs:
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</p>
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<div class="example">
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<pre class="example">.stabs "main:F1",36,0,0,_main # <span class="roman">36 is N_FUN</span>
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.stabs "argc:p1",160,0,0,68 # <span class="roman">160 is N_PSYM</span>
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.stabs "argv:p20=*21=*2",160,0,0,72
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</pre></div>
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<p>The type definition of <code>argv</code> is interesting because it contains
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several type definitions. Type 21 is pointer to type 2 (char) and
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<code>argv</code> (type 20) is pointer to type 21.
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</p>
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<p>The following symbol descriptors are also said to go with <code>N_PSYM</code>.
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The value of the symbol is said to be an offset from the argument
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pointer (I’m not sure whether this is true or not).
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</p>
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<div class="example">
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<pre class="example">pP (<<??>>)
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pF Fortran function parameter
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X (function result variable)
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</pre></div>
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<table class="menu" border="0" cellspacing="0">
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<tr><td align="left" valign="top">• <a href="Register-Parameters.html#Register-Parameters" accesskey="1">Register Parameters</a>:</td><td> </td><td align="left" valign="top">
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</td></tr>
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<tr><td align="left" valign="top">• <a href="Local-Variable-Parameters.html#Local-Variable-Parameters" accesskey="2">Local Variable Parameters</a>:</td><td> </td><td align="left" valign="top">
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</td></tr>
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<tr><td align="left" valign="top">• <a href="Reference-Parameters.html#Reference-Parameters" accesskey="3">Reference Parameters</a>:</td><td> </td><td align="left" valign="top">
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</td></tr>
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<tr><td align="left" valign="top">• <a href="Conformant-Arrays.html#Conformant-Arrays" accesskey="4">Conformant Arrays</a>:</td><td> </td><td align="left" valign="top">
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</td></tr>
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</table>
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<hr>
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<div class="header">
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<p>
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Previous: <a href="Based-Variables.html#Based-Variables" accesskey="p" rel="prev">Based Variables</a>, Up: <a href="Variables.html#Variables" accesskey="u" rel="up">Variables</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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