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99 lines
4.9 KiB
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99 lines
4.9 KiB
HTML
4 years ago
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<title>Adding symbols from an object file - Untitled</title>
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<meta name="description" content="Untitled">
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<link title="Top" rel="start" href="index.html#Top">
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<link rel="up" href="Adding-Symbols-to-the-Hash-Table.html#Adding-Symbols-to-the-Hash-Table" title="Adding Symbols to the Hash Table">
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<link rel="prev" href="Differing-file-formats.html#Differing-file-formats" title="Differing file formats">
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<link rel="next" href="Adding-symbols-from-an-archive.html#Adding-symbols-from-an-archive" title="Adding symbols from an archive">
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<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
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<!--
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This file documents the BFD library.
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Copyright (C) 1991-2015 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3 or
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any later version published by the Free Software Foundation; with the
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Invariant Sections being ``GNU General Public License'' and ``Funding
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Free Software'', the Front-Cover texts being (a) (see below), and with
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the Back-Cover Texts being (b) (see below). A copy of the license is
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included in the section entitled ``GNU Free Documentation License''.
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(a) The FSF's Front-Cover Text is:
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A GNU Manual
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(b) The FSF's Back-Cover Text is:
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<body>
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<div class="node">
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<a name="Adding-symbols-from-an-object-file"></a>
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<p>
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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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Previous: <a rel="previous" accesskey="p" href="Differing-file-formats.html#Differing-file-formats">Differing file formats</a>,
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Up: <a rel="up" accesskey="u" href="Adding-Symbols-to-the-Hash-Table.html#Adding-Symbols-to-the-Hash-Table">Adding Symbols to the Hash Table</a>
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<hr>
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</div>
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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-g_t_005fbfd_005fgeneric_005flink_005fadd_005fone_005fsymbol-2344"></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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</body></html>
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