133 lines
6.7 KiB
HTML
133 lines
6.7 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: Include Files</title>
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<meta name="description" content="STABS: Include Files">
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<meta name="keywords" content="STABS: Include Files">
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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="Program-Structure.html#Program-Structure" rel="up" title="Program Structure">
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<link href="Line-Numbers.html#Line-Numbers" rel="next" title="Line Numbers">
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<link href="Source-Files.html#Source-Files" rel="prev" title="Source Files">
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<style type="text/css">
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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="Include-Files"></a>
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<div class="header">
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<p>
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Next: <a href="Line-Numbers.html#Line-Numbers" accesskey="n" rel="next">Line Numbers</a>, Previous: <a href="Source-Files.html#Source-Files" accesskey="p" rel="prev">Source Files</a>, Up: <a href="Program-Structure.html#Program-Structure" accesskey="u" rel="up">Program Structure</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="Names-of-Include-Files"></a>
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<h3 class="section">2.3 Names of Include Files</h3>
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<p>There are several schemes for dealing with include files: the
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traditional <code>N_SOL</code> approach, Sun’s <code>N_BINCL</code> approach, and the
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XCOFF <code>C_BINCL</code> approach (which despite the similar name has little in
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common with <code>N_BINCL</code>).
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</p>
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<a name="index-N_005fSOL"></a>
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<p>An <code>N_SOL</code> symbol specifies which include file subsequent symbols
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refer to. The string field is the name of the file and the value is the
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text address corresponding to the end of the previous include file and
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the start of this one. To specify the main source file again, use an
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<code>N_SOL</code> symbol with the name of the main source file.
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</p>
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<a name="index-N_005fBINCL"></a>
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<a name="index-N_005fEINCL"></a>
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<a name="index-N_005fEXCL"></a>
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<p>The <code>N_BINCL</code> approach works as follows. An <code>N_BINCL</code> symbol
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specifies the start of an include file. In an object file, only the
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string is significant; the linker puts data into some of the other
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fields. The end of the include file is marked by an <code>N_EINCL</code>
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symbol (which has no string field). In an object file, there is no
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significant data in the <code>N_EINCL</code> symbol. <code>N_BINCL</code> and
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<code>N_EINCL</code> can be nested.
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</p>
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<p>If the linker detects that two source files have identical stabs between
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an <code>N_BINCL</code> and <code>N_EINCL</code> pair (as will generally be the case
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for a header file), then it only puts out the stabs once. Each
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additional occurrence is replaced by an <code>N_EXCL</code> symbol. I believe
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the GNU linker and the Sun (both SunOS4 and Solaris) linker are the only
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ones which supports this feature.
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</p>
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<p>A linker which supports this feature will set the value of a
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<code>N_BINCL</code> symbol to the total of all the characters in the stabs
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strings included in the header file, omitting any file numbers. The
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value of an <code>N_EXCL</code> symbol is the same as the value of the
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<code>N_BINCL</code> symbol it replaces. This information can be used to
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match up <code>N_EXCL</code> and <code>N_BINCL</code> symbols which have the same
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filename. The <code>N_EINCL</code> value, and the values of the other and
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description fields for all three, appear to always be zero.
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</p>
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<a name="index-C_005fBINCL"></a>
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<a name="index-C_005fEINCL"></a>
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<p>For the start of an include file in XCOFF, use the <samp>.bi</samp> assembler
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directive, which generates a <code>C_BINCL</code> symbol. A <samp>.ei</samp>
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directive, which generates a <code>C_EINCL</code> symbol, denotes the end of
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the include file. Both directives are followed by the name of the
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source file in quotes, which becomes the string for the symbol.
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The value of each symbol, produced automatically by the assembler
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and linker, is the offset into the executable of the beginning
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(inclusive, as you’d expect) or end (inclusive, as you would not expect)
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of the portion of the COFF line table that corresponds to this include
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file. <code>C_BINCL</code> and <code>C_EINCL</code> do not nest.
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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="Line-Numbers.html#Line-Numbers" accesskey="n" rel="next">Line Numbers</a>, Previous: <a href="Source-Files.html#Source-Files" accesskey="p" rel="prev">Source Files</a>, Up: <a href="Program-Structure.html#Program-Structure" accesskey="u" rel="up">Program Structure</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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