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77 lines
3.2 KiB
HTML
77 lines
3.2 KiB
HTML
4 years ago
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<title>GGC Roots - GNU Compiler Collection (GCC) Internals</title>
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<meta http-equiv="Content-Type" content="text/html">
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<meta name="description" content="GNU Compiler Collection (GCC) Internals">
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<meta name="generator" content="makeinfo 4.13">
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<link title="Top" rel="start" href="index.html#Top">
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<link rel="up" href="Type-Information.html#Type-Information" title="Type Information">
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<link rel="prev" href="User-GC.html#User-GC" title="User GC">
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<link rel="next" href="Files.html#Files" title="Files">
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<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
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<!--
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Copyright (C) 1988-2015 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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--></style>
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</head>
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<body>
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<div class="node">
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<a name="GGC-Roots"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="Files.html#Files">Files</a>,
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Previous: <a rel="previous" accesskey="p" href="User-GC.html#User-GC">User GC</a>,
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Up: <a rel="up" accesskey="u" href="Type-Information.html#Type-Information">Type Information</a>
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<hr>
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</div>
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<h3 class="section">22.4 Marking Roots for the Garbage Collector</h3>
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<p><a name="index-roots_002c-marking-5095"></a><a name="index-marking-roots-5096"></a>
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In addition to keeping track of types, the type machinery also locates
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the global variables (<dfn>roots</dfn>) that the garbage collector starts
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at. Roots must be declared using one of the following syntaxes:
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<ul>
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<li><code>extern GTY(([</code><var>options</var><code>])) </code><var>type</var> <var>name</var><code>;</code>
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<li><code>static GTY(([</code><var>options</var><code>])) </code><var>type</var> <var>name</var><code>;</code>
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</ul>
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The syntax
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<ul>
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<li><code>GTY(([</code><var>options</var><code>])) </code><var>type</var> <var>name</var><code>;</code>
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</ul>
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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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</body></html>
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