96 lines
5.1 KiB
HTML
96 lines
5.1 KiB
HTML
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<html lang="en">
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<head>
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<title>Include Files - 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="Program-Structure.html#Program-Structure" title="Program Structure">
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<link rel="prev" href="Source-Files.html#Source-Files" title="Source Files">
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<link rel="next" href="Line-Numbers.html#Line-Numbers" title="Line Numbers">
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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="Include-Files"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="Line-Numbers.html#Line-Numbers">Line Numbers</a>,
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Previous: <a rel="previous" accesskey="p" href="Source-Files.html#Source-Files">Source Files</a>,
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Up: <a rel="up" accesskey="u" href="Program-Structure.html#Program-Structure">Program Structure</a>
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<hr>
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</div>
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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><a name="index-N_005fSOL-4"></a>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><a name="index-N_005fBINCL-5"></a><a name="index-N_005fEINCL-6"></a><a name="index-N_005fEXCL-7"></a>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>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>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><a name="index-C_005fBINCL-8"></a><a name="index-C_005fEINCL-9"></a>For the start of an include file in XCOFF, use the <samp><span class="file">.bi</span></samp> assembler
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directive, which generates a <code>C_BINCL</code> symbol. A <samp><span class="file">.ei</span></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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</body></html>
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