102 lines
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102 lines
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<a name="Adding-symbols-from-an-archive"></a>Previous: <a rel="previous" accesskey="p" href="Adding-symbols-from-an-object-file.html#Adding-symbols-from-an-object-file">Adding symbols from an object file</a>,
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Up: <a rel="up" accesskey="u" href="Adding-Symbols-to-the-Hash-Table.html#Adding-Symbols-to-the-Hash-Table">Adding Symbols to the Hash Table</a>
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<h5 class="subsubsection">2.17.2.3 Adding symbols from an archive</h5>
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<p>When the <code>_bfd_link_add_symbols</code> routine is passed an
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archive, it must look through the symbols defined by the
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archive and decide which elements of the archive should be
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included in the link. For each such element it must call the
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<code>add_archive_element</code> linker callback, and it must add the
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symbols from the object file to the linker hash table.
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<p><a name="index-_005fbfd_005fgeneric_005flink_005fadd_005farchive_005fsymbols-1374"></a>In most cases the work of looking through the symbols in the
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archive should be done by the
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<code>_bfd_generic_link_add_archive_symbols</code> function. This
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function builds a hash table from the archive symbol table and
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looks through the list of undefined symbols to see which
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elements should be included.
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<code>_bfd_generic_link_add_archive_symbols</code> is passed a function
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to call to make the final decision about adding an archive
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element to the link and to do the actual work of adding the
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symbols to the linker hash table.
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<p>The function passed to
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<code>_bfd_generic_link_add_archive_symbols</code> must read the
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symbols of the archive element and decide whether the archive
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element should be included in the link. If the element is to
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be included, the <code>add_archive_element</code> linker callback
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routine must be called with the element as an argument, and
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the elements symbols must be added to the linker hash table
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just as though the element had itself been passed to the
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<code>_bfd_link_add_symbols</code> function.
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<p>When the a.out <code>_bfd_link_add_symbols</code> function receives an
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archive, it calls <code>_bfd_generic_link_add_archive_symbols</code>
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passing <code>aout_link_check_archive_element</code> as the function
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argument. <code>aout_link_check_archive_element</code> calls
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<code>aout_link_check_ar_symbols</code>. If the latter decides to add
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the element (an element is only added if it provides a real,
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non-common, definition for a previously undefined or common
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symbol) it calls the <code>add_archive_element</code> callback and then
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<code>aout_link_check_archive_element</code> calls
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<code>aout_link_add_symbols</code> to actually add the symbols to the
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linker hash table.
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<p>The ECOFF back end is unusual in that it does not normally
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call <code>_bfd_generic_link_add_archive_symbols</code>, because ECOFF
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archives already contain a hash table of symbols. The ECOFF
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back end searches the archive itself to avoid the overhead of
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creating a new hash table.
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