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110 lines
4.9 KiB
HTML
110 lines
4.9 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 linker LD
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(SiFive Binutils 2.32.0-2020.04.1)
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version 2.32.
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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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<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>Input Section Common (LD)</title>
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<meta name="description" content="Input Section Common (LD)">
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<meta name="keywords" content="Input Section Common (LD)">
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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="LD-Index.html#LD-Index" rel="index" title="LD Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Input-Section.html#Input-Section" rel="up" title="Input Section">
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<link href="Input-Section-Keep.html#Input-Section-Keep" rel="next" title="Input Section Keep">
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<link href="Input-Section-Wildcards.html#Input-Section-Wildcards" rel="prev" title="Input Section Wildcards">
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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="Input-Section-Common"></a>
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<div class="header">
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<p>
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Next: <a href="Input-Section-Keep.html#Input-Section-Keep" accesskey="n" rel="next">Input Section Keep</a>, Previous: <a href="Input-Section-Wildcards.html#Input-Section-Wildcards" accesskey="p" rel="prev">Input Section Wildcards</a>, Up: <a href="Input-Section.html#Input-Section" accesskey="u" rel="up">Input Section</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="LD-Index.html#LD-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="Input-Section-for-Common-Symbols"></a>
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<h4 class="subsubsection">3.6.4.3 Input Section for Common Symbols</h4>
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<a name="index-common-symbol-placement"></a>
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<a name="index-uninitialized-data-placement"></a>
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<p>A special notation is needed for common symbols, because in many object
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file formats common symbols do not have a particular input section. The
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linker treats common symbols as though they are in an input section
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named ‘<samp>COMMON</samp>’.
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</p>
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<p>You may use file names with the ‘<samp>COMMON</samp>’ section just as with any
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other input sections. You can use this to place common symbols from a
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particular input file in one section while common symbols from other
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input files are placed in another section.
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</p>
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<p>In most cases, common symbols in input files will be placed in the
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‘<samp>.bss</samp>’ section in the output file. For example:
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</p><div class="smallexample">
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<pre class="smallexample">.bss { *(.bss) *(COMMON) }
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</pre></div>
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<a name="index-scommon-section"></a>
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<a name="index-small-common-symbols"></a>
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<p>Some object file formats have more than one type of common symbol. For
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example, the MIPS ELF object file format distinguishes standard common
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symbols and small common symbols. In this case, the linker will use a
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different special section name for other types of common symbols. In
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the case of MIPS ELF, the linker uses ‘<samp>COMMON</samp>’ for standard common
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symbols and ‘<samp>.scommon</samp>’ for small common symbols. This permits you
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to map the different types of common symbols into memory at different
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locations.
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</p>
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<a name="index-_005bCOMMON_005d"></a>
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<p>You will sometimes see ‘<samp>[COMMON]</samp>’ in old linker scripts. This
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notation is now considered obsolete. It is equivalent to
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‘<samp>*(COMMON)</samp>’.
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</p>
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</body>
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</html>
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