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96 lines
4.0 KiB
HTML
96 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>bss (Using as)</title>
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<meta name="description" content="bss (Using as)">
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<meta name="keywords" content="bss (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="Sections.html#Sections" rel="up" title="Sections">
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<link href="Symbols.html#Symbols" rel="next" title="Symbols">
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<link href="Sub_002dSections.html#Sub_002dSections" rel="prev" title="Sub-Sections">
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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="bss"></a>
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<div class="header">
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<p>
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Previous: <a href="Sub_002dSections.html#Sub_002dSections" accesskey="p" rel="prev">Sub-Sections</a>, Up: <a href="Sections.html#Sections" accesskey="u" rel="up">Sections</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="bss-Section"></a>
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<h3 class="section">4.5 bss Section</h3>
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<a name="index-bss-section-1"></a>
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<a name="index-common-variable-storage"></a>
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<p>The bss section is used for local common variable storage.
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You may allocate address space in the bss section, but you may
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not dictate data to load into it before your program executes. When
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your program starts running, all the contents of the bss
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section are zeroed bytes.
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</p>
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<p>The <code>.lcomm</code> pseudo-op defines a symbol in the bss section; see
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<a href="Lcomm.html#Lcomm"><code>.lcomm</code></a>.
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</p>
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<p>The <code>.comm</code> pseudo-op may be used to declare a common symbol, which is
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another form of uninitialized symbol; see <a href="Comm.html#Comm"><code>.comm</code></a>.
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</p>
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<p>When assembling for a target which supports multiple sections, such as ELF or
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COFF, you may switch into the <code>.bss</code> section and define symbols as usual;
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see <a href="Section.html#Section"><code>.section</code></a>. You may only assemble zero values into the
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section. Typically the section will only contain symbol definitions and
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<code>.skip</code> directives (see <a href="Skip.html#Skip"><code>.skip</code></a>).
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</p>
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</body>
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</html>
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