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  1. <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

  2. <html>

  3. <!-- This file documents the BFD library.

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  11. Free Software", the Front-Cover texts being (a) (see below), and with

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  27. <title>Adding symbols from an object file (Untitled Document)</title>

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  29. <meta name="description" content="Adding symbols from an object file (Untitled Document)">

  30. <meta name="keywords" content="Adding symbols from an object file (Untitled Document)">

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  34. <link href="index.html#Top" rel="start" title="Top">

  35. <link href="BFD-Index.html#BFD-Index" rel="index" title="BFD Index">

  36. <link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">

  37. <link href="Adding-Symbols-to-the-Hash-Table.html#Adding-Symbols-to-the-Hash-Table" rel="up" title="Adding Symbols to the Hash Table">

  38. <link href="Adding-symbols-from-an-archive.html#Adding-symbols-from-an-archive" rel="next" title="Adding symbols from an archive">

  39. <link href="Differing-file-formats.html#Differing-file-formats" rel="prev" title="Differing file formats">

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  66. </style>

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  69. </head>

  70. 

  71. <body lang="en">

  72. <a name="Adding-symbols-from-an-object-file"></a>

  73. <div class="header">

  74. <p>

  75. Next: <a href="Adding-symbols-from-an-archive.html#Adding-symbols-from-an-archive" accesskey="n" rel="next">Adding symbols from an archive</a>, Previous: <a href="Differing-file-formats.html#Differing-file-formats" accesskey="p" rel="prev">Differing file formats</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> &nbsp; [<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>

  76. </div>

  77. <hr>

  78. <a name="Adding-symbols-from-an-object-file-1"></a>

  79. <h4 class="subsubsection">2.17.2.2 Adding symbols from an object file</h4>

  80. <p>When the <code>_bfd_link_add_symbols</code> routine is passed an object

  81. file, it must add all externally visible symbols in that

  82. object file to the hash table.  The actual work of adding the

  83. symbol to the hash table is normally handled by the function

  84. <code>_bfd_generic_link_add_one_symbol</code>.  The

  85. <code>_bfd_link_add_symbols</code> routine is responsible for reading

  86. all the symbols from the object file and passing the correct

  87. information to <code>_bfd_generic_link_add_one_symbol</code>.

  88. </p>

  89. <p>The <code>_bfd_link_add_symbols</code> routine should not use

  90. <code>bfd_canonicalize_symtab</code> to read the symbols.  The point of

  91. providing this routine is to avoid the overhead of converting

  92. the symbols into generic <code>asymbol</code> structures.

  93. </p>

  94. <a name="index-_005fbfd_005fgeneric_005flink_005fadd_005fone_005fsymbol"></a>

  95. <p><code>_bfd_generic_link_add_one_symbol</code> handles the details of

  96. combining common symbols, warning about multiple definitions,

  97. and so forth.  It takes arguments which describe the symbol to

  98. add, notably symbol flags, a section, and an offset.  The

  99. symbol flags include such things as <code>BSF_WEAK</code> or

  100. <code>BSF_INDIRECT</code>.  The section is a section in the object

  101. file, or something like <code>bfd_und_section_ptr</code> for an undefined

  102. symbol or <code>bfd_com_section_ptr</code> for a common symbol.

  103. </p>

  104. <p>If the <code>_bfd_final_link</code> routine is also going to need to

  105. read the symbol information, the <code>_bfd_link_add_symbols</code>

  106. routine should save it somewhere attached to the object file

  107. BFD.  However, the information should only be saved if the

  108. <code>keep_memory</code> field of the <code>info</code> argument is TRUE, so

  109. that the <code>-no-keep-memory</code> linker switch is effective.

  110. </p>

  111. <p>The a.out function which adds symbols from an object file is

  112. <code>aout_link_add_object_symbols</code>, and most of the interesting

  113. work is in <code>aout_link_add_symbols</code>.  The latter saves

  114. pointers to the hash tables entries created by

  115. <code>_bfd_generic_link_add_one_symbol</code> indexed by symbol number,

  116. so that the <code>_bfd_final_link</code> routine does not have to call

  117. the hash table lookup routine to locate the entry.

  118. </p>

  119. <hr>

  120. <div class="header">

  121. <p>

  122. Next: <a href="Adding-symbols-from-an-archive.html#Adding-symbols-from-an-archive" accesskey="n" rel="next">Adding symbols from an archive</a>, Previous: <a href="Differing-file-formats.html#Differing-file-formats" accesskey="p" rel="prev">Differing file formats</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> &nbsp; [<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>

  123. </div>

  124. 

  125. 

  126. 

  127. </body>

  128. </html>