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<h5 class="subsubsection">2.17.2.3 Adding symbols from an archive</h5>
<p>When the <code>_bfd_link_add_symbols</code> routine is passed an
archive, it must look through the symbols defined by the
archive and decide which elements of the archive should be
included in the link. For each such element it must call the
<code>add_archive_element</code> linker callback, and it must add the
symbols from the object file to the linker hash table. (The
callback may in fact indicate that a replacement BFD should be
used, in which case the symbols from that BFD should be added
to the linker hash table instead.)
<p><a name="index-g_t_005fbfd_005fgeneric_005flink_005fadd_005farchive_005fsymbols-2345"></a>In most cases the work of looking through the symbols in the
archive should be done by the
<code>_bfd_generic_link_add_archive_symbols</code> function.
<code>_bfd_generic_link_add_archive_symbols</code> is passed a function
to call to make the final decision about adding an archive
element to the link and to do the actual work of adding the
symbols to the linker hash table. If the element is to
be included, the <code>add_archive_element</code> linker callback
routine must be called with the element as an argument, and
the element's symbols must be added to the linker hash table
just as though the element had itself been passed to the
<code>_bfd_link_add_symbols</code> function.
<p>When the a.out <code>_bfd_link_add_symbols</code> function receives an
archive, it calls <code>_bfd_generic_link_add_archive_symbols</code>
passing <code>aout_link_check_archive_element</code> as the function
argument. <code>aout_link_check_archive_element</code> calls
<code>aout_link_check_ar_symbols</code>. If the latter decides to add
the element (an element is only added if it provides a real,
non-common, definition for a previously undefined or common
symbol) it calls the <code>add_archive_element</code> callback and then
<code>aout_link_check_archive_element</code> calls
<code>aout_link_add_symbols</code> to actually add the symbols to the
linker hash table - possibly those of a substitute BFD, if the
<code>add_archive_element</code> callback avails itself of that option.
<p>The ECOFF back end is unusual in that it does not normally
call <code>_bfd_generic_link_add_archive_symbols</code>, because ECOFF
archives already contain a hash table of symbols. The ECOFF
back end searches the archive itself to avoid the overhead of
creating a new hash table.
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