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<h5 class="subsubsection">2.17.2.2 Adding symbols from an object file</h5>
<p>When the <code>_bfd_link_add_symbols</code> routine is passed an object
file, it must add all externally visible symbols in that
object file to the hash table. The actual work of adding the
symbol to the hash table is normally handled by the function
<code>_bfd_generic_link_add_one_symbol</code>. The
<code>_bfd_link_add_symbols</code> routine is responsible for reading
all the symbols from the object file and passing the correct
information to <code>_bfd_generic_link_add_one_symbol</code>.
<p>The <code>_bfd_link_add_symbols</code> routine should not use
<code>bfd_canonicalize_symtab</code> to read the symbols. The point of
providing this routine is to avoid the overhead of converting
the symbols into generic <code>asymbol</code> structures.
<p><a name="index-g_t_005fbfd_005fgeneric_005flink_005fadd_005fone_005fsymbol-2344"></a><code>_bfd_generic_link_add_one_symbol</code> handles the details of
combining common symbols, warning about multiple definitions,
and so forth. It takes arguments which describe the symbol to
add, notably symbol flags, a section, and an offset. The
symbol flags include such things as <code>BSF_WEAK</code> or
<code>BSF_INDIRECT</code>. The section is a section in the object
file, or something like <code>bfd_und_section_ptr</code> for an undefined
symbol or <code>bfd_com_section_ptr</code> for a common symbol.
<p>If the <code>_bfd_final_link</code> routine is also going to need to
read the symbol information, the <code>_bfd_link_add_symbols</code>
routine should save it somewhere attached to the object file
BFD. However, the information should only be saved if the
<code>keep_memory</code> field of the <code>info</code> argument is TRUE, so
that the <code>-no-keep-memory</code> linker switch is effective.
<p>The a.out function which adds symbols from an object file is
<code>aout_link_add_object_symbols</code>, and most of the interesting
work is in <code>aout_link_add_symbols</code>. The latter saves
pointers to the hash tables entries created by
<code>_bfd_generic_link_add_one_symbol</code> indexed by symbol number,
so that the <code>_bfd_final_link</code> routine does not have to call
the hash table lookup routine to locate the entry.
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