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 <a name="Targets"></a>
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 <p>
 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> &nbsp; [<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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 <hr>
 <a name="Targets-1"></a>
 <h3 class="section">2.12 Targets</h3>


 <p><strong>Description</strong><br>
 Each port of BFD to a different machine requires the creation
 of a target back end. All the back end provides to the root
 part of BFD is a structure containing pointers to functions
 which perform certain low level operations on files. BFD
 translates the applications&rsquo;s requests through a pointer into
 calls to the back end routines.
 </p>
 <p>When a file is opened with <code>bfd_openr</code>, its format and
 target are unknown. BFD uses various mechanisms to determine
 how to interpret the file. The operations performed are:
 </p>
 <ul>
 <li> Create a BFD by calling the internal routine
 <code>_bfd_new_bfd</code>, then call <code>bfd_find_target</code> with the
 target string supplied to <code>bfd_openr</code> and the new BFD pointer.

 </li><li> If a null target string was provided to <code>bfd_find_target</code>,
 look up the environment variable <code>GNUTARGET</code> and use
 that as the target string.

 </li><li> If the target string is still <code>NULL</code>, or the target string is
 <code>default</code>, then use the first item in the target vector
 as the target type, and set <code>target_defaulted</code> in the BFD to
 cause <code>bfd_check_format</code> to loop through all the targets.
 See <a href="bfd_005ftarget.html#bfd_005ftarget">bfd_target</a>.  See <a href="Formats.html#Formats">Formats</a>.

 </li><li> Otherwise, inspect the elements in the target vector
 one by one, until a match on target name is found. When found,
 use it.

 </li><li> Otherwise return the error <code>bfd_error_invalid_target</code> to
 <code>bfd_openr</code>.

 </li><li> <code>bfd_openr</code> attempts to open the file using
 <code>bfd_open_file</code>, and returns the BFD.
 </li></ul>
 <p>Once the BFD has been opened and the target selected, the file
 format may be determined. This is done by calling
 <code>bfd_check_format</code> on the BFD with a suggested format.
 If <code>target_defaulted</code> has been set, each possible target
 type is tried to see if it recognizes the specified format.
 <code>bfd_check_format</code> returns <code>TRUE</code> when the caller guesses right.
 </p><table class="menu" border="0" cellspacing="0">
 <tr><td align="left" valign="top">&bull; <a href="bfd_005ftarget.html#bfd_005ftarget" accesskey="1">bfd_target</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
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	<p>
	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>
	</div>
	<hr>
	<a name="Targets-1"></a>
	<h3 class="section">2.12 Targets</h3>


	<p><strong>Description</strong><br>
	Each port of BFD to a different machine requires the creation
	of a target back end. All the back end provides to the root
	part of BFD is a structure containing pointers to functions
	which perform certain low level operations on files. BFD
	translates the applications’s requests through a pointer into
	calls to the back end routines.
	</p>
	<p>When a file is opened with <code>bfd_openr</code>, its format and
	target are unknown. BFD uses various mechanisms to determine
	how to interpret the file. The operations performed are:
	</p>
	<ul>
	<li> Create a BFD by calling the internal routine
	<code>_bfd_new_bfd</code>, then call <code>bfd_find_target</code> with the
	target string supplied to <code>bfd_openr</code> and the new BFD pointer.

	</li><li> If a null target string was provided to <code>bfd_find_target</code>,
	look up the environment variable <code>GNUTARGET</code> and use
	that as the target string.

	</li><li> If the target string is still <code>NULL</code>, or the target string is
	<code>default</code>, then use the first item in the target vector
	as the target type, and set <code>target_defaulted</code> in the BFD to
	cause <code>bfd_check_format</code> to loop through all the targets.
	See <a href="bfd_005ftarget.html#bfd_005ftarget">bfd_target</a>. See <a href="Formats.html#Formats">Formats</a>.

	</li><li> Otherwise, inspect the elements in the target vector
	one by one, until a match on target name is found. When found,
	use it.

	</li><li> Otherwise return the error <code>bfd_error_invalid_target</code> to
	<code>bfd_openr</code>.

	</li><li> <code>bfd_openr</code> attempts to open the file using
	<code>bfd_open_file</code>, and returns the BFD.
	</li></ul>
	<p>Once the BFD has been opened and the target selected, the file
	format may be determined. This is done by calling
	<code>bfd_check_format</code> on the BFD with a suggested format.
	If <code>target_defaulted</code> has been set, each possible target
	type is tried to see if it recognizes the specified format.
	<code>bfd_check_format</code> returns <code>TRUE</code> when the caller guesses right.
	</p><table class="menu" border="0" cellspacing="0">
	<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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