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| <a name="Adding-symbols-from-an-archive"></a> |
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| Previous: <a href="Adding-symbols-from-an-object-file.html#Adding-symbols-from-an-object-file" accesskey="p" rel="prev">Adding symbols from an object file</a>, Up: <a href="Adding-Symbols-to-the-Hash-Table.html#Adding-Symbols-to-the-Hash-Table" accesskey="u" rel="up">Adding Symbols to the Hash Table</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> |
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| <a name="Adding-symbols-from-an-archive-1"></a> |
| <h4 class="subsubsection">2.17.2.3 Adding symbols from an archive</h4> |
| <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-_005fbfd_005fgeneric_005flink_005fadd_005farchive_005fsymbols"></a> |
| <p>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. 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. |
| <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. |
| </p> |
| <p>The function passed to |
| <code>_bfd_generic_link_add_archive_symbols</code> 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 <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. The <code>add_archive_element</code> |
| callback has the option to indicate that it would like to |
| replace the element archive with a substitute BFD, in which |
| case it is the symbols of that substitute BFD that must be |
| added to the linker hash table instead. |
| </p> |
| <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> |
| <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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| Previous: <a href="Adding-symbols-from-an-object-file.html#Adding-symbols-from-an-object-file" accesskey="p" rel="prev">Adding symbols from an object file</a>, Up: <a href="Adding-Symbols-to-the-Hash-Table.html#Adding-Symbols-to-the-Hash-Table" accesskey="u" rel="up">Adding Symbols to the Hash Table</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> |
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