<html lang="en"> <head> <title>Plugins GC - GNU Compiler Collection (GCC) Internals</title> <meta http-equiv="Content-Type" content="text/html"> <meta name="description" content="GNU Compiler Collection (GCC) Internals"> <meta name="generator" content="makeinfo 4.13"> <link title="Top" rel="start" href="index.html#Top"> <link rel="up" href="Plugins.html#Plugins" title="Plugins"> <link rel="prev" href="Plugins-pass.html#Plugins-pass" title="Plugins pass"> <link rel="next" href="Plugins-description.html#Plugins-description" title="Plugins description"> <link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> <!-- Copyright (C) 1988-2015 Free Software Foundation, Inc. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with the Invariant Sections being ``Funding Free Software'', the Front-Cover Texts being (a) (see below), and with the Back-Cover Texts being (b) (see below). A copy of the license is included in the section entitled ``GNU Free Documentation License''. (a) The FSF's Front-Cover Text is: A GNU Manual (b) The FSF's Back-Cover Text is: You have freedom to copy and modify this GNU Manual, like GNU software. Copies published by the Free Software Foundation raise funds for GNU development.--> <meta http-equiv="Content-Style-Type" content="text/css"> <style type="text/css"><!-- pre.display { font-family:inherit } pre.format { font-family:inherit } pre.smalldisplay { font-family:inherit; font-size:smaller } pre.smallformat { font-family:inherit; font-size:smaller } pre.smallexample { font-size:smaller } pre.smalllisp { font-size:smaller } span.sc { font-variant:small-caps } span.roman { font-family:serif; font-weight:normal; } span.sansserif { font-family:sans-serif; font-weight:normal; } --></style> </head> <body> <div class="node"> <a name="Plugins-GC"></a> <p> Next: <a rel="next" accesskey="n" href="Plugins-description.html#Plugins-description">Plugins description</a>, Previous: <a rel="previous" accesskey="p" href="Plugins-pass.html#Plugins-pass">Plugins pass</a>, Up: <a rel="up" accesskey="u" href="Plugins.html#Plugins">Plugins</a> <hr> </div> <h3 class="section">23.4 Interacting with the GCC Garbage Collector</h3> <p>Some plugins may want to be informed when GGC (the GCC Garbage Collector) is running. They can register callbacks for the <code>PLUGIN_GGC_START</code> and <code>PLUGIN_GGC_END</code> events (for which the callback is called with a null <code>gcc_data</code>) to be notified of the start or end of the GCC garbage collection. <p>Some plugins may need to have GGC mark additional data. This can be done by registering a callback (called with a null <code>gcc_data</code>) for the <code>PLUGIN_GGC_MARKING</code> event. Such callbacks can call the <code>ggc_set_mark</code> routine, preferably through the <code>ggc_mark</code> macro (and conversely, these routines should usually not be used in plugins outside of the <code>PLUGIN_GGC_MARKING</code> event). Plugins that wish to hold weak references to gc data may also use this event to drop weak references when the object is about to be collected. The <code>ggc_marked_p</code> function can be used to tell if an object is marked, or is about to be collected. The <code>gt_clear_cache</code> overloads which some types define may also be of use in managing weak references. <p>Some plugins may need to add extra GGC root tables, e.g. to handle their own <code>GTY</code>-ed data. This can be done with the <code>PLUGIN_REGISTER_GGC_ROOTS</code> pseudo-event with a null callback and the extra root table (of type <code>struct ggc_root_tab*</code>) as <code>user_data</code>. Running the <code>gengtype -p </code><var>source-dir</var> <var>file-list</var> <var>plugin*.c</var><code> ...</code> utility generates these extra root tables. <p>You should understand the details of memory management inside GCC before using <code>PLUGIN_GGC_MARKING</code> or <code>PLUGIN_REGISTER_GGC_ROOTS</code>. </body></html>