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142 lines
6.9 KiB
HTML
142 lines
6.9 KiB
HTML
4 years ago
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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) 1992-2019 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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<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>Statics (STABS)</title>
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<meta name="description" content="Statics (STABS)">
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<meta name="keywords" content="Statics (STABS)">
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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="Based-Variables.html#Based-Variables" rel="next" title="Based Variables">
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<link href="Common-Blocks.html#Common-Blocks" rel="prev" title="Common Blocks">
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<style type="text/css">
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<!--
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a.summary-letter {text-decoration: none}
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blockquote.indentedblock {margin-right: 0em}
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blockquote.smallindentedblock {margin-right: 0em; font-size: smaller}
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blockquote.smallquotation {font-size: smaller}
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div.display {margin-left: 3.2em}
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div.example {margin-left: 3.2em}
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div.lisp {margin-left: 3.2em}
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div.smalldisplay {margin-left: 3.2em}
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div.smallexample {margin-left: 3.2em}
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kbd {font-style: oblique}
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pre.display {font-family: inherit}
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pre.format {font-family: inherit}
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pre.menu-comment {font-family: serif}
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pre.menu-preformatted {font-family: serif}
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pre.smalldisplay {font-family: inherit; font-size: smaller}
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pre.smallformat {font-family: inherit; font-size: smaller}
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pre.smalllisp {font-size: smaller}
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span.nolinebreak {white-space: nowrap}
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span.roman {font-family: initial; font-weight: normal}
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span.sansserif {font-family: sans-serif; font-weight: normal}
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ul.no-bullet {list-style: none}
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-->
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</style>
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</head>
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<body lang="en">
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<a name="Statics"></a>
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<div class="header">
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<p>
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Next: <a href="Based-Variables.html#Based-Variables" accesskey="n" rel="next">Based Variables</a>, Previous: <a href="Common-Blocks.html#Common-Blocks" accesskey="p" rel="prev">Common Blocks</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="Static-Variables"></a>
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<h3 class="section">4.5 Static Variables</h3>
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<p>Initialized static variables are represented by the ‘<samp>S</samp>’ and
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‘<samp>V</samp>’ symbol descriptors. ‘<samp>S</samp>’ means file scope static, and
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‘<samp>V</samp>’ means procedure scope static. One exception: in XCOFF, IBM’s
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xlc compiler always uses ‘<samp>V</samp>’, and whether it is file scope or not
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is distinguished by whether the stab is located within a function.
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</p>
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<a name="index-N_005fSTSYM"></a>
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<a name="index-N_005fLCSYM"></a>
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<a name="index-N_005fFUN_002c-for-variables"></a>
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<a name="index-N_005fROSYM"></a>
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<p>In a.out files, <code>N_STSYM</code> means the data section, <code>N_FUN</code>
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means the text section, and <code>N_LCSYM</code> means the bss section. For
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those systems with a read-only data section separate from the text
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section (Solaris), <code>N_ROSYM</code> means the read-only data section.
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</p>
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<p>For example, the source lines:
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</p>
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<div class="example">
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<pre class="example">static const int var_const = 5;
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static int var_init = 2;
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static int var_noinit;
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</pre></div>
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<p>yield the following stabs:
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</p>
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<div class="example">
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<pre class="example">.stabs "var_const:S1",36,0,0,_var_const # <span class="roman">36 is N_FUN</span>
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…
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.stabs "var_init:S1",38,0,0,_var_init # <span class="roman">38 is N_STSYM</span>
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…
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.stabs "var_noinit:S1",40,0,0,_var_noinit # <span class="roman">40 is N_LCSYM</span>
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</pre></div>
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<a name="index-C_005fSTSYM"></a>
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<a name="index-C_005fBSTAT"></a>
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<a name="index-C_005fESTAT"></a>
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<p>In XCOFF files, the stab type need not indicate the section;
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<code>C_STSYM</code> can be used for all statics. Also, each static variable
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is enclosed in a static block. A <code>C_BSTAT</code> (emitted with a
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‘<samp>.bs</samp>’ assembler directive) symbol begins the static block; its
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value is the symbol number of the csect symbol whose value is the
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address of the static block, its section is the section of the variables
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in that static block, and its name is ‘<samp>.bs</samp>’. A <code>C_ESTAT</code>
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(emitted with a ‘<samp>.es</samp>’ assembler directive) symbol ends the static
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block; its name is ‘<samp>.es</samp>’ and its value and section are ignored.
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</p>
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<p>In ECOFF files, the storage class is used to specify the section, so the
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stab type need not indicate the section.
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</p>
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<p>In ELF files, for the SunPRO compiler version 2.0.1, symbol descriptor
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‘<samp>S</samp>’ means that the address is absolute (the linker relocates it)
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and symbol descriptor ‘<samp>V</samp>’ means that the address is relative to the
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start of the relevant section for that compilation unit. SunPRO has
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plans to have the linker stop relocating stabs; I suspect that their the
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debugger gets the address from the corresponding ELF (not stab) symbol.
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I’m not sure how to find which symbol of that name is the right one.
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The clean way to do all this would be to have the value of a symbol
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descriptor ‘<samp>S</samp>’ symbol be an offset relative to the start of the
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file, just like everything else, but that introduces obvious
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compatibility problems. For more information on linker stab relocation,
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See <a href="ELF-Linker-Relocation.html#ELF-Linker-Relocation">ELF Linker Relocation</a>.
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</p>
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<hr>
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<div class="header">
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<p>
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Next: <a href="Based-Variables.html#Based-Variables" accesskey="n" rel="next">Based Variables</a>, Previous: <a href="Common-Blocks.html#Common-Blocks" accesskey="p" rel="prev">Common Blocks</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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