Plugins-GC.html 5.3 KB

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  65. Next: <a href="Plugins-description.html#Plugins-description" accesskey="n" rel="next">Plugins description</a>, Previous: <a href="Plugins-pass.html#Plugins-pass" accesskey="p" rel="prev">Plugins pass</a>, Up: <a href="Plugins.html#Plugins" accesskey="u" rel="up">Plugins</a> &nbsp; [<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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  68. <a name="Interacting-with-the-GCC-Garbage-Collector"></a>
  69. <h3 class="section">23.4 Interacting with the GCC Garbage Collector</h3>
  70. <p>Some plugins may want to be informed when GGC (the GCC Garbage
  71. Collector) is running. They can register callbacks for the
  72. <code>PLUGIN_GGC_START</code> and <code>PLUGIN_GGC_END</code> events (for which
  73. the callback is called with a null <code>gcc_data</code>) to be notified of
  74. the start or end of the GCC garbage collection.
  75. </p>
  76. <p>Some plugins may need to have GGC mark additional data. This can be
  77. done by registering a callback (called with a null <code>gcc_data</code>)
  78. for the <code>PLUGIN_GGC_MARKING</code> event. Such callbacks can call the
  79. <code>ggc_set_mark</code> routine, preferably through the <code>ggc_mark</code> macro
  80. (and conversely, these routines should usually not be used in plugins
  81. outside of the <code>PLUGIN_GGC_MARKING</code> event). Plugins that wish to hold
  82. weak references to gc data may also use this event to drop weak references when
  83. the object is about to be collected. The <code>ggc_marked_p</code> function can be
  84. used to tell if an object is marked, or is about to be collected. The
  85. <code>gt_clear_cache</code> overloads which some types define may also be of use in
  86. managing weak references.
  87. </p>
  88. <p>Some plugins may need to add extra GGC root tables, e.g. to handle their own
  89. <code>GTY</code>-ed data. This can be done with the <code>PLUGIN_REGISTER_GGC_ROOTS</code>
  90. pseudo-event with a null callback and the extra root table (of type <code>struct
  91. ggc_root_tab*</code>) as <code>user_data</code>. Running the
  92. <code>gengtype -p <var>source-dir</var> <var>file-list</var> <var>plugin*.c</var> ...</code>
  93. utility generates these extra root tables.
  94. </p>
  95. <p>You should understand the details of memory management inside GCC
  96. before using <code>PLUGIN_GGC_MARKING</code> or <code>PLUGIN_REGISTER_GGC_ROOTS</code>.
  97. </p>
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