106 lines
4.5 KiB
HTML
106 lines
4.5 KiB
HTML
<html lang="en">
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<head>
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<title>Targets - Untitled</title>
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<meta name="description" content="Untitled">
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<meta name="generator" content="makeinfo 4.7">
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<link title="Top" rel="start" href="index.html#Top">
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<link rel="up" href="BFD-front-end.html#BFD-front-end" title="BFD front end">
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<link rel="prev" href="Core-Files.html#Core-Files" title="Core Files">
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<link rel="next" href="Architectures.html#Architectures" title="Architectures">
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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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This file documents the BFD library.
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Copyright (C) 1991, 2000, 2001, 2003, 2006, 2007 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 1.1 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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</head>
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<body>
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<div class="node">
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<p>
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<a name="Targets"></a>Next: <a rel="next" accesskey="n" href="Architectures.html#Architectures">Architectures</a>,
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Previous: <a rel="previous" accesskey="p" href="Core-Files.html#Core-Files">Core Files</a>,
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Up: <a rel="up" accesskey="u" href="BFD-front-end.html#BFD-front-end">BFD front end</a>
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<hr><br>
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</div>
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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>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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<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>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>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>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>Otherwise return the error <code>bfd_error_invalid_target</code> to
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<code>bfd_openr</code>.
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<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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</ul>
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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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<ul class="menu">
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<li><a accesskey="1" href="bfd_005ftarget.html#bfd_005ftarget">bfd_target</a>
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</ul>
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</body></html>
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