92 lines
4.1 KiB
HTML
92 lines
4.1 KiB
HTML
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<html lang="en">
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<head>
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<title>Parameters - STABS</title>
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<meta http-equiv="Content-Type" content="text/html">
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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="Variables.html#Variables" title="Variables">
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<link rel="prev" href="Based-Variables.html#Based-Variables" title="Based Variables">
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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="Parameters"></a>
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<p>
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Previous: <a rel="previous" accesskey="p" href="Based-Variables.html#Based-Variables">Based Variables</a>,
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Up: <a rel="up" accesskey="u" href="Variables.html#Variables">Variables</a>
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<hr>
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</div>
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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><a name="index-N_005fPSYM-44"></a><a name="index-C_005fPSYM-45"></a>Parameters passed on the stack use the symbol descriptor ‘<samp><span class="samp">p</span></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>As a simple example, the code:
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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>
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<p>produces the stabs:
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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>
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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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<!-- FIXME: figure out what these mean and describe them coherently. -->
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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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<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>
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<ul class="menu">
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<li><a accesskey="1" href="Register-Parameters.html#Register-Parameters">Register Parameters</a>
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<li><a accesskey="2" href="Local-Variable-Parameters.html#Local-Variable-Parameters">Local Variable Parameters</a>
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<li><a accesskey="3" href="Reference-Parameters.html#Reference-Parameters">Reference Parameters</a>
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<li><a accesskey="4" href="Conformant-Arrays.html#Conformant-Arrays">Conformant Arrays</a>
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</ul>
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</body></html>
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