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<a name="Adding-symbols-from-an-object-file"></a>Next: <a rel="next" accesskey="n" href="Adding-symbols-from-an-archive.html#Adding-symbols-from-an-archive">Adding symbols from an archive</a>,
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<h5 class="subsubsection">2.17.2.2 Adding symbols from an object file</h5>
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<p>When the <code>_bfd_link_add_symbols</code> routine is passed an object
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file, it must add all externally visible symbols in that
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object file to the hash table. The actual work of adding the
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symbol to the hash table is normally handled by the function
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<code>_bfd_generic_link_add_one_symbol</code>. The
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<code>_bfd_link_add_symbols</code> routine is responsible for reading
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all the symbols from the object file and passing the correct
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information to <code>_bfd_generic_link_add_one_symbol</code>.
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<p>The <code>_bfd_link_add_symbols</code> routine should not use
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<code>bfd_canonicalize_symtab</code> to read the symbols. The point of
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providing this routine is to avoid the overhead of converting
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the symbols into generic <code>asymbol</code> structures.
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<p><a name="index-_005fbfd_005fgeneric_005flink_005fadd_005fone_005fsymbol-1373"></a><code>_bfd_generic_link_add_one_symbol</code> handles the details of
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combining common symbols, warning about multiple definitions,
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and so forth. It takes arguments which describe the symbol to
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add, notably symbol flags, a section, and an offset. The
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symbol flags include such things as <code>BSF_WEAK</code> or
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<code>BSF_INDIRECT</code>. The section is a section in the object
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file, or something like <code>bfd_und_section_ptr</code> for an undefined
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symbol or <code>bfd_com_section_ptr</code> for a common symbol.
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<p>If the <code>_bfd_final_link</code> routine is also going to need to
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read the symbol information, the <code>_bfd_link_add_symbols</code>
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routine should save it somewhere attached to the object file
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BFD. However, the information should only be saved if the
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<code>keep_memory</code> field of the <code>info</code> argument is TRUE, so
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that the <code>-no-keep-memory</code> linker switch is effective.
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<p>The a.out function which adds symbols from an object file is
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<code>aout_link_add_object_symbols</code>, and most of the interesting
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work is in <code>aout_link_add_symbols</code>. The latter saves
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pointers to the hash tables entries created by
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<code>_bfd_generic_link_add_one_symbol</code> indexed by symbol number,
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so that the <code>_bfd_final_link</code> routine does not have to call
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the hash table lookup routine to locate the entry.
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