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95 lines
4.0 KiB
HTML
95 lines
4.0 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 GNU Assembler "as".
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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
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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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-->
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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>Symbol Value (Using as)</title>
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<meta name="description" content="Symbol Value (Using as)">
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<meta name="keywords" content="Symbol Value (Using as)">
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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="AS-Index.html#AS-Index" rel="index" title="AS Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Symbol-Attributes.html#Symbol-Attributes" rel="up" title="Symbol Attributes">
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<link href="Symbol-Type.html#Symbol-Type" rel="next" title="Symbol Type">
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<link href="Symbol-Attributes.html#Symbol-Attributes" rel="prev" title="Symbol Attributes">
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<style type="text/css">
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<!--
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a.summary-letter {text-decoration: none}
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blockquote.indentedblock {margin-right: 0em}
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blockquote.smallindentedblock {margin-right: 0em; font-size: smaller}
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blockquote.smallquotation {font-size: smaller}
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div.display {margin-left: 3.2em}
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div.example {margin-left: 3.2em}
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div.lisp {margin-left: 3.2em}
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div.smalldisplay {margin-left: 3.2em}
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div.smallexample {margin-left: 3.2em}
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div.smalllisp {margin-left: 3.2em}
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kbd {font-style: oblique}
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pre.display {font-family: inherit}
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pre.format {font-family: inherit}
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pre.menu-comment {font-family: serif}
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pre.menu-preformatted {font-family: serif}
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pre.smalldisplay {font-family: inherit; font-size: smaller}
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pre.smallexample {font-size: smaller}
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pre.smallformat {font-family: inherit; font-size: smaller}
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pre.smalllisp {font-size: smaller}
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span.nolinebreak {white-space: nowrap}
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span.roman {font-family: initial; font-weight: normal}
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span.sansserif {font-family: sans-serif; font-weight: normal}
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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="Symbol-Value"></a>
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<div class="header">
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<p>
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Next: <a href="Symbol-Type.html#Symbol-Type" accesskey="n" rel="next">Symbol Type</a>, Up: <a href="Symbol-Attributes.html#Symbol-Attributes" accesskey="u" rel="up">Symbol Attributes</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="AS-Index.html#AS-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="Value"></a>
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<h4 class="subsection">5.5.1 Value</h4>
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<a name="index-value-of-a-symbol"></a>
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<a name="index-symbol-value"></a>
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<p>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>
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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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</p>
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</body>
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</html>
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