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(bfd.info)Adding symbols from an archive

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Adding symbols from an archive
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   When the `_bfd_link_add_symbols' 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 `add_archive_element' linker callback, and it
must add the symbols from the object file to the linker hash table.

   In most cases the work of looking through the symbols in the archive
should be done by the `_bfd_generic_link_add_archive_symbols' function.
This function builds a hash table from the archive symbol table and
looks through the list of undefined symbols to see which elements
should be included.  `_bfd_generic_link_add_archive_symbols' 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.

   The function passed to `_bfd_generic_link_add_archive_symbols' must
read the symbols of the archive element and decide whether the archive
element should be included in the link.  If the element is to be
included, the `add_archive_element' linker callback routine must be
called with the element as an argument, and the elements symbols must
be added to the linker hash table just as though the element had itself
been passed to the `_bfd_link_add_symbols' function.

   When the a.out `_bfd_link_add_symbols' function receives an archive,
it calls `_bfd_generic_link_add_archive_symbols' passing
`aout_link_check_archive_element' as the function argument.
`aout_link_check_archive_element' calls `aout_link_check_ar_symbols'.
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 `add_archive_element' callback and then
`aout_link_check_archive_element' calls `aout_link_add_symbols' to
actually add the symbols to the linker hash table.

   The ECOFF back end is unusual in that it does not normally call
`_bfd_generic_link_add_archive_symbols', 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.