104 lines
4.3 KiB
HTML
104 lines
4.3 KiB
HTML
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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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<!-- Copyright (C) 1988-2016 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 or
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any later version published by the Free Software Foundation; with the
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Invariant Sections being "Funding Free Software", the Front-Cover
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Texts being (a) (see below), and with the Back-Cover Texts being (b)
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(see below). A copy of the license is included in the section entitled
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"GNU Free Documentation License".
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(a) The FSF's Front-Cover Text is:
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A GNU Manual
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(b) The FSF's Back-Cover Text is:
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You have freedom to copy and modify this GNU Manual, like GNU
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software. Copies published by the Free Software Foundation raise
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funds for GNU development. -->
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<!-- Created by GNU Texinfo 5.2, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>GNU Compiler Collection (GCC) Internals: GGC Roots</title>
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<meta name="description" content="GNU Compiler Collection (GCC) Internals: GGC Roots">
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<meta name="keywords" content="GNU Compiler Collection (GCC) Internals: GGC Roots">
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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="Option-Index.html#Option-Index" rel="index" title="Option Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Type-Information.html#Type-Information" rel="up" title="Type Information">
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<link href="Files.html#Files" rel="next" title="Files">
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<link href="User-GC.html#User-GC" rel="prev" title="User GC">
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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.smallquotation {font-size: smaller}
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div.smallindentedblock {margin-left: 3.2em; font-size: smaller}
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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.nocodebreak {white-space:nowrap}
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span.nolinebreak {white-space:nowrap}
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span.roman {font-family:serif; 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" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
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<a name="GGC-Roots"></a>
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<div class="header">
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<p>
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Next: <a href="Files.html#Files" accesskey="n" rel="next">Files</a>, Previous: <a href="User-GC.html#User-GC" accesskey="p" rel="prev">User GC</a>, Up: <a href="Type-Information.html#Type-Information" accesskey="u" rel="up">Type Information</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="Marking-Roots-for-the-Garbage-Collector"></a>
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<h3 class="section">22.4 Marking Roots for the Garbage Collector</h3>
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<a name="index-roots_002c-marking"></a>
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<a name="index-marking-roots"></a>
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<p>In addition to keeping track of types, the type machinery also locates
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the global variables (<em>roots</em>) that the garbage collector starts
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at. Roots must be declared using one of the following syntaxes:
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</p>
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<ul>
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<li> <code>extern GTY(([<var>options</var>])) <var>type</var> <var>name</var>;</code>
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</li><li> <code>static GTY(([<var>options</var>])) <var>type</var> <var>name</var>;</code>
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</li></ul>
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<p>The syntax
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</p><ul>
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<li> <code>GTY(([<var>options</var>])) <var>type</var> <var>name</var>;</code>
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</li></ul>
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<p>is <em>not</em> accepted. There should be an <code>extern</code> declaration
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of such a variable in a header somewhere—mark that, not the
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definition. Or, if the variable is only used in one file, make it
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<code>static</code>.
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</p>
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</body>
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</html>
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