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102 lines
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102 lines
4.2 KiB
HTML
<html lang="en">
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<head>
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<title>How It Works - Untitled</title>
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<meta name="description" content="Untitled">
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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="Overview.html#Overview" title="Overview">
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<link rel="prev" href="History.html#History" title="History">
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<link rel="next" href="What-BFD-Version-2-Can-Do.html#What-BFD-Version-2-Can-Do" title="What BFD Version 2 Can Do">
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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) 1991-2015 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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<body>
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<div class="node">
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<a name="How-It-Works"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="What-BFD-Version-2-Can-Do.html#What-BFD-Version-2-Can-Do">What BFD Version 2 Can Do</a>,
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Previous: <a rel="previous" accesskey="p" href="History.html#History">History</a>,
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Up: <a rel="up" accesskey="u" href="Overview.html#Overview">Overview</a>
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<hr>
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</div>
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<h3 class="section">1.2 How To Use BFD</h3>
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<p>To use the library, include <samp><span class="file">bfd.h</span></samp> and link with <samp><span class="file">libbfd.a</span></samp>.
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<p>BFD provides a common interface to the parts of an object file
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for a calling application.
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<p>When an application successfully opens a target file (object, archive, or
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whatever), a pointer to an internal structure is returned. This pointer
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points to a structure called <code>bfd</code>, described in
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<samp><span class="file">bfd.h</span></samp>. Our convention is to call this pointer a BFD, and
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instances of it within code <code>abfd</code>. All operations on
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the target object file are applied as methods to the BFD. The mapping is
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defined within <code>bfd.h</code> in a set of macros, all beginning
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with ‘<samp><span class="samp">bfd_</span></samp>’ to reduce namespace pollution.
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<p>For example, this sequence does what you would probably expect:
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return the number of sections in an object file attached to a BFD
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<code>abfd</code>.
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<pre class="example"> <!-- @cartouche -->
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#include "bfd.h"
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unsigned int number_of_sections (abfd)
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bfd *abfd;
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{
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return bfd_count_sections (abfd);
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}
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<!-- @end cartouche -->
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</pre>
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<p>The abstraction used within BFD is that an object file has:
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<ul>
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<li>a header,
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<li>a number of sections containing raw data (see <a href="Sections.html#Sections">Sections</a>),
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<li>a set of relocations (see <a href="Relocations.html#Relocations">Relocations</a>), and
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<li>some symbol information (see <a href="Symbols.html#Symbols">Symbols</a>).
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</ul>
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Also, BFDs opened for archives have the additional attribute of an index
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and contain subordinate BFDs. This approach is fine for a.out and coff,
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but loses efficiency when applied to formats such as S-records and
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IEEE-695.
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</body></html>
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