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140 lines
6.1 KiB
HTML
140 lines
6.1 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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<!-- This file documents the BFD library.
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Copyright (C) 1991-2019 Free Software Foundation, Inc.
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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 the
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Invariant Sections being "GNU General Public License" and "Funding
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Free Software", the Front-Cover texts being (a) (see below), and with
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the Back-Cover Texts being (b) (see below). A copy of the license is
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included in the section entitled "GNU Free Documentation License".
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(a) The FSF's Front-Cover Text is:
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A GNU Manual
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(b) The FSF's Back-Cover Text is:
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You have freedom to copy and modify this GNU Manual, like GNU
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software. Copies published by the Free Software Foundation raise
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funds for GNU development. -->
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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>Targets (Untitled Document)</title>
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<meta name="description" content="Targets (Untitled Document)">
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<meta name="keywords" content="Targets (Untitled Document)">
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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="BFD-Index.html#BFD-Index" rel="index" title="BFD Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="BFD-front-end.html#BFD-front-end" rel="up" title="BFD front end">
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<link href="bfd_005ftarget.html#bfd_005ftarget" rel="next" title="bfd_target">
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<link href="Core-Files.html#Core-Files" rel="prev" title="Core Files">
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<style type="text/css">
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<!--
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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="Targets"></a>
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<div class="header">
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<p>
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Next: <a href="Architectures.html#Architectures" accesskey="n" rel="next">Architectures</a>, Previous: <a href="Core-Files.html#Core-Files" accesskey="p" rel="prev">Core Files</a>, Up: <a href="BFD-front-end.html#BFD-front-end" accesskey="u" rel="up">BFD front end</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="BFD-Index.html#BFD-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="Targets-1"></a>
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<h3 class="section">2.12 Targets</h3>
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<p><strong>Description</strong><br>
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Each port of BFD to a different machine requires the creation
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of a target back end. All the back end provides to the root
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part of BFD is a structure containing pointers to functions
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which perform certain low level operations on files. BFD
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translates the applications’s requests through a pointer into
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calls to the back end routines.
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</p>
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<p>When a file is opened with <code>bfd_openr</code>, its format and
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target are unknown. BFD uses various mechanisms to determine
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how to interpret the file. The operations performed are:
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</p>
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<ul>
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<li> Create a BFD by calling the internal routine
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<code>_bfd_new_bfd</code>, then call <code>bfd_find_target</code> with the
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target string supplied to <code>bfd_openr</code> and the new BFD pointer.
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</li><li> If a null target string was provided to <code>bfd_find_target</code>,
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look up the environment variable <code>GNUTARGET</code> and use
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that as the target string.
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</li><li> If the target string is still <code>NULL</code>, or the target string is
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<code>default</code>, then use the first item in the target vector
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as the target type, and set <code>target_defaulted</code> in the BFD to
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cause <code>bfd_check_format</code> to loop through all the targets.
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See <a href="bfd_005ftarget.html#bfd_005ftarget">bfd_target</a>. See <a href="Formats.html#Formats">Formats</a>.
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</li><li> Otherwise, inspect the elements in the target vector
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one by one, until a match on target name is found. When found,
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use it.
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</li><li> Otherwise return the error <code>bfd_error_invalid_target</code> to
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<code>bfd_openr</code>.
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</li><li> <code>bfd_openr</code> attempts to open the file using
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<code>bfd_open_file</code>, and returns the BFD.
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</li></ul>
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<p>Once the BFD has been opened and the target selected, the file
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format may be determined. This is done by calling
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<code>bfd_check_format</code> on the BFD with a suggested format.
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If <code>target_defaulted</code> has been set, each possible target
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type is tried to see if it recognizes the specified format.
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<code>bfd_check_format</code> returns <code>TRUE</code> when the caller guesses right.
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</p><table class="menu" border="0" cellspacing="0">
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<tr><td align="left" valign="top">• <a href="bfd_005ftarget.html#bfd_005ftarget" accesskey="1">bfd_target</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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Next: <a href="Architectures.html#Architectures" accesskey="n" rel="next">Architectures</a>, Previous: <a href="Core-Files.html#Core-Files" accesskey="p" rel="prev">Core Files</a>, Up: <a href="BFD-front-end.html#BFD-front-end" accesskey="u" rel="up">BFD front end</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="BFD-Index.html#BFD-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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