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67 lines
2.9 KiB
HTML
67 lines
2.9 KiB
HTML
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<title>Symbol Value - Using as</title>
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<link title="Top" rel="start" href="index.html#Top">
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<link rel="up" href="Symbol-Attributes.html#Symbol-Attributes" title="Symbol Attributes">
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<link rel="next" href="Symbol-Type.html#Symbol-Type" title="Symbol Type">
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<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
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This file documents the GNU Assembler "as".
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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
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or any later version published by the Free Software Foundation;
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with no Invariant Sections, with no Front-Cover Texts, and with no
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Back-Cover Texts. A copy of the license is included in the
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section entitled ``GNU Free Documentation License''.
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</head>
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<body>
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<div class="node">
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<a name="Symbol-Value"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="Symbol-Type.html#Symbol-Type">Symbol Type</a>,
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Up: <a rel="up" accesskey="u" href="Symbol-Attributes.html#Symbol-Attributes">Symbol Attributes</a>
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<hr>
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</div>
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<h4 class="subsection">5.5.1 Value</h4>
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<p><a name="index-value-of-a-symbol-227"></a><a name="index-symbol-value-228"></a>The value of a symbol is (usually) 32 bits. For a symbol which labels a
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location in the text, data, bss or absolute sections the value is the
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number of addresses from the start of that section to the label.
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Naturally for text, data and bss sections the value of a symbol changes
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as <code>ld</code> changes section base addresses during linking. Absolute
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symbols' values do not change during linking: that is why they are
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called absolute.
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<p>The value of an undefined symbol is treated in a special way. If it is
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0 then the symbol is not defined in this assembler source file, and
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<code>ld</code> tries to determine its value from other files linked into the
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same program. You make this kind of symbol simply by mentioning a symbol
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name without defining it. A non-zero value represents a <code>.comm</code>
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common declaration. The value is how much common storage to reserve, in
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bytes (addresses). The symbol refers to the first address of the
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allocated storage.
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</body></html>
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