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314 lines
14 KiB
HTML
314 lines
14 KiB
HTML
4 years ago
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<!-- This file documents the BFD library.
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Copyright (C) 1991-2019 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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You have freedom to copy and modify this GNU Manual, like GNU
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software. Copies published by the Free Software Foundation raise
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funds for GNU development. -->
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<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>Writing the symbol table (Untitled Document)</title>
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<meta name="description" content="Writing the symbol table (Untitled Document)">
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<meta name="keywords" content="Writing the symbol table (Untitled Document)">
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<meta name="resource-type" content="document">
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<meta name="distribution" content="global">
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<meta name="Generator" content="makeinfo">
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<link href="index.html#Top" rel="start" title="Top">
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<link href="BFD-Index.html#BFD-Index" rel="index" title="BFD Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Performing-the-Final-Link.html#Performing-the-Final-Link" rel="up" title="Performing the Final Link">
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<link href="Hash-Tables.html#Hash-Tables" rel="next" title="Hash Tables">
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<link href="Relocating-the-section-contents.html#Relocating-the-section-contents" rel="prev" title="Relocating the section contents">
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<style type="text/css">
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div.display {margin-left: 3.2em}
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pre.smalldisplay {font-family: inherit; font-size: smaller}
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ul.no-bullet {list-style: none}
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-->
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</style>
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</head>
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<body lang="en">
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<a name="Writing-the-symbol-table"></a>
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<div class="header">
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<p>
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Previous: <a href="Relocating-the-section-contents.html#Relocating-the-section-contents" accesskey="p" rel="prev">Relocating the section contents</a>, Up: <a href="Performing-the-Final-Link.html#Performing-the-Final-Link" accesskey="u" rel="up">Performing the Final Link</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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</div>
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<hr>
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<a name="Writing-the-symbol-table-1"></a>
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<h4 class="subsubsection">2.17.3.3 Writing the symbol table</h4>
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<p>The <code>_bfd_final_link</code> function must gather all the symbols
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in the input files and write them out. It must also write out
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all the symbols in the global hash table. This must be
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controlled by the <code>strip</code> and <code>discard</code> fields of the
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<code>bfd_link_info</code> structure.
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</p>
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<p>The local symbols of the input files will not have been
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entered into the linker hash table. The <code>_bfd_final_link</code>
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routine must consider each input file and include the symbols
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in the output file. It may be convenient to do this when
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looking through the <code>link_order</code> structures, or it may be
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done by stepping through the <code>input_bfds</code> list.
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</p>
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<p>The <code>_bfd_final_link</code> routine must also traverse the global
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hash table to gather all the externally visible symbols. It
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is possible that most of the externally visible symbols may be
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written out when considering the symbols of each input file,
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but it is still necessary to traverse the hash table since the
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linker script may have defined some symbols that are not in
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any of the input files.
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</p>
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<p>The <code>strip</code> field of the <code>bfd_link_info</code> structure
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controls which symbols are written out. The possible values
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are listed in <code>bfdlink.h</code>. If the value is <code>strip_some</code>,
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then the <code>keep_hash</code> field of the <code>bfd_link_info</code>
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structure is a hash table of symbols to keep; each symbol
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should be looked up in this hash table, and only symbols which
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are present should be included in the output file.
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</p>
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<p>If the <code>strip</code> field of the <code>bfd_link_info</code> structure
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permits local symbols to be written out, the <code>discard</code> field
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is used to further controls which local symbols are included
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in the output file. If the value is <code>discard_l</code>, then all
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local symbols which begin with a certain prefix are discarded;
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this is controlled by the <code>bfd_is_local_label_name</code> entry point.
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</p>
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<p>The a.out backend handles symbols by calling
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<code>aout_link_write_symbols</code> on each input BFD and then
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traversing the global hash table with the function
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<code>aout_link_write_other_symbol</code>. It builds a string table
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while writing out the symbols, which is written to the output
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file at the end of <code>NAME(aout,final_link)</code>.
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</p>
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<a name="index-bfd_005flink_005fsplit_005fsection"></a>
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<a name="bfd_005flink_005fsplit_005fsection"></a>
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<h4 class="subsubsection">2.17.3.4 <code>bfd_link_split_section</code></h4>
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<p><strong>Synopsis</strong>
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</p><div class="example">
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<pre class="example">bfd_boolean bfd_link_split_section (bfd *abfd, asection *sec);
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</pre></div>
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<p><strong>Description</strong><br>
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Return nonzero if <var>sec</var> should be split during a
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reloceatable or final link.
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</p><div class="example">
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<pre class="example">#define bfd_link_split_section(abfd, sec) \
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BFD_SEND (abfd, _bfd_link_split_section, (abfd, sec))
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</pre></div>
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<a name="index-bfd_005fsection_005falready_005flinked"></a>
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<a name="bfd_005fsection_005falready_005flinked"></a>
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<h4 class="subsubsection">2.17.3.5 <code>bfd_section_already_linked</code></h4>
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<p><strong>Synopsis</strong>
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</p><div class="example">
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<pre class="example">bfd_boolean bfd_section_already_linked (bfd *abfd,
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asection *sec,
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struct bfd_link_info *info);
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</pre></div>
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<p><strong>Description</strong><br>
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Check if <var>data</var> has been already linked during a reloceatable
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or final link. Return TRUE if it has.
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</p><div class="example">
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<pre class="example">#define bfd_section_already_linked(abfd, sec, info) \
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BFD_SEND (abfd, _section_already_linked, (abfd, sec, info))
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</pre></div>
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<a name="index-bfd_005fgeneric_005fdefine_005fcommon_005fsymbol"></a>
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<a name="bfd_005fgeneric_005fdefine_005fcommon_005fsymbol"></a>
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<h4 class="subsubsection">2.17.3.6 <code>bfd_generic_define_common_symbol</code></h4>
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<p><strong>Synopsis</strong>
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</p><div class="example">
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<pre class="example">bfd_boolean bfd_generic_define_common_symbol
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(bfd *output_bfd, struct bfd_link_info *info,
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struct bfd_link_hash_entry *h);
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</pre></div>
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<p><strong>Description</strong><br>
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Convert common symbol <var>h</var> into a defined symbol.
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Return TRUE on success and FALSE on failure.
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</p><div class="example">
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<pre class="example">#define bfd_define_common_symbol(output_bfd, info, h) \
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BFD_SEND (output_bfd, _bfd_define_common_symbol, (output_bfd, info, h))
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</pre></div>
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<a name="index-_005fbfd_005fgeneric_005flink_005fhide_005fsymbol"></a>
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<a name="g_t_005fbfd_005fgeneric_005flink_005fhide_005fsymbol"></a>
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<h4 class="subsubsection">2.17.3.7 <code>_bfd_generic_link_hide_symbol</code></h4>
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<p><strong>Synopsis</strong>
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</p><div class="example">
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<pre class="example">void _bfd_generic_link_hide_symbol
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(bfd *output_bfd, struct bfd_link_info *info,
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struct bfd_link_hash_entry *h);
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</pre></div>
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<p><strong>Description</strong><br>
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Hide symbol <var>h</var>.
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This is an internal function. It should not be called from
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outside the BFD library.
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</p><div class="example">
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<pre class="example">#define bfd_link_hide_symbol(output_bfd, info, h) \
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BFD_SEND (output_bfd, _bfd_link_hide_symbol, (output_bfd, info, h))
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</pre></div>
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<a name="index-bfd_005fgeneric_005fdefine_005fstart_005fstop"></a>
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<a name="bfd_005fgeneric_005fdefine_005fstart_005fstop"></a>
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<h4 class="subsubsection">2.17.3.8 <code>bfd_generic_define_start_stop</code></h4>
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<p><strong>Synopsis</strong>
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</p><div class="example">
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<pre class="example">struct bfd_link_hash_entry *bfd_generic_define_start_stop
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(struct bfd_link_info *info,
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const char *symbol, asection *sec);
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</pre></div>
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<p><strong>Description</strong><br>
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Define a __start, __stop, .startof. or .sizeof. symbol.
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Return the symbol or NULL if no such undefined symbol exists.
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</p><div class="example">
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<pre class="example">#define bfd_define_start_stop(output_bfd, info, symbol, sec) \
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BFD_SEND (output_bfd, _bfd_define_start_stop, (info, symbol, sec))
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</pre></div>
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<a name="index-bfd_005ffind_005fversion_005ffor_005fsym"></a>
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<a name="bfd_005ffind_005fversion_005ffor_005fsym"></a>
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<h4 class="subsubsection">2.17.3.9 <code>bfd_find_version_for_sym</code></h4>
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<p><strong>Synopsis</strong>
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</p><div class="example">
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<pre class="example">struct bfd_elf_version_tree * bfd_find_version_for_sym
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(struct bfd_elf_version_tree *verdefs,
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const char *sym_name, bfd_boolean *hide);
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</pre></div>
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<p><strong>Description</strong><br>
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Search an elf version script tree for symbol versioning
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info and export / don’t-export status for a given symbol.
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Return non-NULL on success and NULL on failure; also sets
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the output ‘<samp>hide</samp>’ boolean parameter.
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</p>
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<a name="index-bfd_005fhide_005fsym_005fby_005fversion"></a>
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<a name="bfd_005fhide_005fsym_005fby_005fversion"></a>
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<h4 class="subsubsection">2.17.3.10 <code>bfd_hide_sym_by_version</code></h4>
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<p><strong>Synopsis</strong>
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</p><div class="example">
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<pre class="example">bfd_boolean bfd_hide_sym_by_version
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(struct bfd_elf_version_tree *verdefs, const char *sym_name);
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</pre></div>
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<p><strong>Description</strong><br>
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Search an elf version script tree for symbol versioning
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info for a given symbol. Return TRUE if the symbol is hidden.
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</p>
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<a name="index-bfd_005flink_005fcheck_005frelocs"></a>
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<a name="bfd_005flink_005fcheck_005frelocs"></a>
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<h4 class="subsubsection">2.17.3.11 <code>bfd_link_check_relocs</code></h4>
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<p><strong>Synopsis</strong>
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</p><div class="example">
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<pre class="example">bfd_boolean bfd_link_check_relocs
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(bfd *abfd, struct bfd_link_info *info);
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</pre></div>
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<p><strong>Description</strong><br>
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Checks the relocs in ABFD for validity.
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Does not execute the relocs.
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Return TRUE if everything is OK, FALSE otherwise.
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This is the external entry point to this code.
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</p>
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<a name="index-_005fbfd_005fgeneric_005flink_005fcheck_005frelocs"></a>
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<a name="g_t_005fbfd_005fgeneric_005flink_005fcheck_005frelocs"></a>
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<h4 class="subsubsection">2.17.3.12 <code>_bfd_generic_link_check_relocs</code></h4>
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<p><strong>Synopsis</strong>
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</p><div class="example">
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<pre class="example">bfd_boolean _bfd_generic_link_check_relocs
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(bfd *abfd, struct bfd_link_info *info);
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</pre></div>
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<p><strong>Description</strong><br>
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Stub function for targets that do not implement reloc checking.
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Return TRUE.
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This is an internal function. It should not be called from
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outside the BFD library.
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</p>
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<a name="index-bfd_005fmerge_005fprivate_005fbfd_005fdata"></a>
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<a name="bfd_005fmerge_005fprivate_005fbfd_005fdata"></a>
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<h4 class="subsubsection">2.17.3.13 <code>bfd_merge_private_bfd_data</code></h4>
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<p><strong>Synopsis</strong>
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</p><div class="example">
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<pre class="example">bfd_boolean bfd_merge_private_bfd_data
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(bfd *ibfd, struct bfd_link_info *info);
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</pre></div>
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<p><strong>Description</strong><br>
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Merge private BFD information from the BFD <var>ibfd</var> to the
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the output file BFD when linking. Return <code>TRUE</code> on success,
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<code>FALSE</code> on error. Possible error returns are:
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</p>
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<ul>
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<li> <code>bfd_error_no_memory</code> -
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Not enough memory exists to create private data for <var>obfd</var>.
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</li></ul>
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<div class="example">
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<pre class="example">#define bfd_merge_private_bfd_data(ibfd, info) \
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BFD_SEND ((info)->output_bfd, _bfd_merge_private_bfd_data, \
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(ibfd, info))
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</pre></div>
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<a name="index-_005fbfd_005fgeneric_005fverify_005fendian_005fmatch"></a>
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<a name="g_t_005fbfd_005fgeneric_005fverify_005fendian_005fmatch"></a>
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<h4 class="subsubsection">2.17.3.14 <code>_bfd_generic_verify_endian_match</code></h4>
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<p><strong>Synopsis</strong>
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</p><div class="example">
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<pre class="example">bfd_boolean _bfd_generic_verify_endian_match
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(bfd *ibfd, struct bfd_link_info *info);
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</pre></div>
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<p><strong>Description</strong><br>
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Can be used from / for bfd_merge_private_bfd_data to check that
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endianness matches between input and output file. Returns
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TRUE for a match, otherwise returns FALSE and emits an error.
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</p>
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<hr>
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<div class="header">
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<p>
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Previous: <a href="Relocating-the-section-contents.html#Relocating-the-section-contents" accesskey="p" rel="prev">Relocating the section contents</a>, Up: <a href="Performing-the-Final-Link.html#Performing-the-Final-Link" accesskey="u" rel="up">Performing the Final Link</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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