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			156 lines
		
	
	
	
		
			6.4 KiB
		
	
	
	
		
			HTML
		
	
	
	
	
	
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<title>Archives - Untitled</title>
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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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<p>
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<a name="Archives"></a>Next: <a rel="next" accesskey="n" href="Formats.html#Formats">Formats</a>,
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Previous: <a rel="previous" accesskey="p" href="Symbols.html#Symbols">Symbols</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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<h3 class="section">2.8 Archives</h3>
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<p><strong>Description</strong><br>
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An archive (or library) is just another BFD.  It has a symbol
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table, although there's not much a user program will do with it.
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   <p>The big difference between an archive BFD and an ordinary BFD
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is that the archive doesn't have sections.  Instead it has a
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chain of BFDs that are considered its contents.  These BFDs can
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be manipulated like any other.  The BFDs contained in an
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archive opened for reading will all be opened for reading.  You
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may put either input or output BFDs into an archive opened for
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output; they will be handled correctly when the archive is closed.
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   <p>Use <code>bfd_openr_next_archived_file</code> to step through
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the contents of an archive opened for input.  You don't
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have to read the entire archive if you don't want
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to!  Read it until you find what you want.
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   <p>Archive contents of output BFDs are chained through the
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<code>next</code> pointer in a BFD.  The first one is findable through
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the <code>archive_head</code> slot of the archive.  Set it with
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<code>bfd_set_archive_head</code> (q.v.).  A given BFD may be in only one
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open output archive at a time.
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   <p>As expected, the BFD archive code is more general than the
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archive code of any given environment.  BFD archives may
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contain files of different formats (e.g., a.out and coff) and
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even different architectures.  You may even place archives
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recursively into archives!
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   <p>This can cause unexpected confusion, since some archive
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formats are more expressive than others.  For instance, Intel
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COFF archives can preserve long filenames; SunOS a.out archives
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cannot.  If you move a file from the first to the second
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format and back again, the filename may be truncated. 
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Likewise, different a.out environments have different
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conventions as to how they truncate filenames, whether they
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preserve directory names in filenames, etc.  When
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interoperating with native tools, be sure your files are
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homogeneous.
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   <p>Beware: most of these formats do not react well to the
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presence of spaces in filenames.  We do the best we can, but
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can't always handle this case due to restrictions in the format of
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archives.  Many Unix utilities are braindead in regards to
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spaces and such in filenames anyway, so this shouldn't be much
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of a restriction.
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   <p>Archives are supported in BFD in <code>archive.c</code>.
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<h4 class="subsection">2.8.1 Archive functions</h4>
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<p><a name="index-bfd_005fget_005fnext_005fmapent-73"></a>
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<h5 class="subsubsection">2.8.1.1 <code>bfd_get_next_mapent</code></h5>
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<p><strong>Synopsis</strong>
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<pre class="example">     symindex bfd_get_next_mapent
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        (bfd *abfd, symindex previous, carsym **sym);
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</pre>
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   <p><strong>Description</strong><br>
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Step through archive <var>abfd</var>'s symbol table (if it
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has one).  Successively update <var>sym</var> with the next symbol's
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information, returning that symbol's (internal) index into the
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symbol table.
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   <p>Supply <code>BFD_NO_MORE_SYMBOLS</code> as the <var>previous</var> entry to get
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the first one; returns <code>BFD_NO_MORE_SYMBOLS</code> when you've already
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got the last one.
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   <p>A <code>carsym</code> is a canonical archive symbol.  The only
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user-visible element is its name, a null-terminated string.
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   <p><a name="index-bfd_005fset_005farchive_005fhead-74"></a>
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<h5 class="subsubsection">2.8.1.2 <code>bfd_set_archive_head</code></h5>
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<p><strong>Synopsis</strong>
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<pre class="example">     bfd_boolean bfd_set_archive_head (bfd *output, bfd *new_head);
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</pre>
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   <p><strong>Description</strong><br>
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Set the head of the chain of
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BFDs contained in the archive <var>output</var> to <var>new_head</var>.
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   <p><a name="index-bfd_005fopenr_005fnext_005farchived_005ffile-75"></a>
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<h5 class="subsubsection">2.8.1.3 <code>bfd_openr_next_archived_file</code></h5>
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<p><strong>Synopsis</strong>
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<pre class="example">     bfd *bfd_openr_next_archived_file (bfd *archive, bfd *previous);
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</pre>
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   <p><strong>Description</strong><br>
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Provided a BFD, <var>archive</var>, containing an archive and NULL, open
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an input BFD on the first contained element and returns that. 
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Subsequent calls should pass
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the archive and the previous return value to return a created
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BFD to the next contained element. NULL is returned when there
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are no more.
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