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