115 lines
5.7 KiB
HTML
115 lines
5.7 KiB
HTML
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<!-- This file documents the GNU Assembler "as".
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Copyright (C) 1991-2016 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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<head>
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<title>Using as: Object Attributes</title>
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<meta name="description" content="Using as: Object Attributes">
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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="index.html#Top" rel="up" title="Top">
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<link href="GNU-Object-Attributes.html#GNU-Object-Attributes" rel="next" title="GNU Object Attributes">
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<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
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<a name="Object-Attributes"></a>
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<div class="header">
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<p>
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Next: <a href="Machine-Dependencies.html#Machine-Dependencies" accesskey="n" rel="next">Machine Dependencies</a>, Previous: <a href="Pseudo-Ops.html#Pseudo-Ops" accesskey="p" rel="prev">Pseudo Ops</a>, Up: <a href="index.html#Top" accesskey="u" rel="up">Top</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="Object-Attributes-1"></a>
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<h2 class="chapter">8 Object Attributes</h2>
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<a name="index-object-attributes"></a>
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<p><code>as</code> assembles source files written for a specific architecture
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into object files for that architecture. But not all object files are alike.
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Many architectures support incompatible variations. For instance, floating
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point arguments might be passed in floating point registers if the object file
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requires hardware floating point support—or floating point arguments might be
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passed in integer registers if the object file supports processors with no
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hardware floating point unit. Or, if two objects are built for different
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generations of the same architecture, the combination may require the
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newer generation at run-time.
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</p>
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<p>This information is useful during and after linking. At link time,
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<code>ld</code> can warn about incompatible object files. After link
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time, tools like <code>gdb</code> can use it to process the linked file
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correctly.
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</p>
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<p>Compatibility information is recorded as a series of object attributes. Each
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attribute has a <em>vendor</em>, <em>tag</em>, and <em>value</em>. The vendor is a
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string, and indicates who sets the meaning of the tag. The tag is an integer,
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and indicates what property the attribute describes. The value may be a string
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or an integer, and indicates how the property affects this object. Missing
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attributes are the same as attributes with a zero value or empty string value.
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</p>
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<p>Object attributes were developed as part of the ABI for the ARM Architecture.
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The file format is documented in <cite>ELF for the ARM Architecture</cite>.
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</p>
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<table class="menu" border="0" cellspacing="0">
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<tr><td align="left" valign="top">• <a href="GNU-Object-Attributes.html#GNU-Object-Attributes" accesskey="1">GNU Object Attributes</a>:</td><td> </td><td align="left" valign="top"><small>GNU</small> Object Attributes
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</td></tr>
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<tr><td align="left" valign="top">• <a href="Defining-New-Object-Attributes.html#Defining-New-Object-Attributes" accesskey="2">Defining New Object Attributes</a>:</td><td> </td><td align="left" valign="top">Defining New Object Attributes
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</td></tr>
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</table>
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<hr>
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<div class="header">
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<p>
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Next: <a href="Machine-Dependencies.html#Machine-Dependencies" accesskey="n" rel="next">Machine Dependencies</a>, Previous: <a href="Pseudo-Ops.html#Pseudo-Ops" accesskey="p" rel="prev">Pseudo Ops</a>, Up: <a href="index.html#Top" accesskey="u" rel="up">Top</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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</body>
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