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135 lines
6.0 KiB
HTML
135 lines
6.0 KiB
HTML
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Contributed by Cygnus Support. Written by Julia Menapace, Jim Kingdon,
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Permission is granted to copy, distribute and/or modify this document
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<head>
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<title>Parameters (STABS)</title>
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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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<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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