131 lines
6.9 KiB
HTML
131 lines
6.9 KiB
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<!DOCTYPE html>
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<!-- Created by GNU Texinfo 7.1, https://www.gnu.org/software/texinfo/ -->
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<!-- This manual documents Guile version 3.0.10.
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Copyright (C) 1996-1997, 2000-2005, 2009-2023 Free Software Foundation,
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Inc.
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Copyright (C) 2021 Maxime Devos
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Copyright (C) 2024 Tomas Volf
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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 no
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Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A
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copy of the license is included in the section entitled "GNU Free
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Documentation License." -->
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<title>GC Hooks (Guile Reference Manual)</title>
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<meta name="description" content="GC Hooks (Guile Reference Manual)">
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<link href="index.html" rel="start" title="Top">
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<link href="Concept-Index.html" rel="index" title="Concept Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Hooks.html" rel="up" title="Hooks">
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<link href="REPL-Hooks.html" rel="next" title="REPL Hooks">
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<link href="C-Hooks.html" rel="prev" title="C Hooks">
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<link rel="stylesheet" type="text/css" href="https://www.gnu.org/software/gnulib/manual.css">
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</head>
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<body lang="en">
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<div class="subsubsection-level-extent" id="GC-Hooks">
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<div class="nav-panel">
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<p>
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Next: <a href="REPL-Hooks.html" accesskey="n" rel="next">Hooks into the Guile REPL</a>, Previous: <a href="C-Hooks.html" accesskey="p" rel="prev">Hooks For C Code.</a>, Up: <a href="Hooks.html" accesskey="u" rel="up">Hooks</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<h4 class="subsubsection" id="Hooks-for-Garbage-Collection"><span>6.9.6.4 Hooks for Garbage Collection<a class="copiable-link" href="#Hooks-for-Garbage-Collection"> ¶</a></span></h4>
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<p>Whenever Guile performs a garbage collection, it calls the following
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hooks in the order shown.
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</p>
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<dl class="first-defvr">
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<dt class="defvr" id="index-scm_005fbefore_005fgc_005fc_005fhook"><span class="category-def">C Hook: </span><span><strong class="def-name">scm_before_gc_c_hook</strong><a class="copiable-link" href="#index-scm_005fbefore_005fgc_005fc_005fhook"> ¶</a></span></dt>
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<dd><p>C hook called at the very start of a garbage collection, after setting
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<code class="code">scm_gc_running_p</code> to 1, but before entering the GC critical
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section.
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</p>
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<p>If garbage collection is blocked because <code class="code">scm_block_gc</code> is
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non-zero, GC exits early soon after calling this hook, and no further
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hooks will be called.
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</p></dd></dl>
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<dl class="first-defvr">
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<dt class="defvr" id="index-scm_005fbefore_005fmark_005fc_005fhook"><span class="category-def">C Hook: </span><span><strong class="def-name">scm_before_mark_c_hook</strong><a class="copiable-link" href="#index-scm_005fbefore_005fmark_005fc_005fhook"> ¶</a></span></dt>
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<dd><p>C hook called before beginning the mark phase of garbage collection,
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after the GC thread has entered a critical section.
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</p></dd></dl>
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<dl class="first-defvr">
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<dt class="defvr" id="index-scm_005fbefore_005fsweep_005fc_005fhook"><span class="category-def">C Hook: </span><span><strong class="def-name">scm_before_sweep_c_hook</strong><a class="copiable-link" href="#index-scm_005fbefore_005fsweep_005fc_005fhook"> ¶</a></span></dt>
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<dd><p>C hook called before beginning the sweep phase of garbage collection.
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This is the same as at the end of the mark phase, since nothing else
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happens between marking and sweeping.
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</p></dd></dl>
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<dl class="first-defvr">
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<dt class="defvr" id="index-scm_005fafter_005fsweep_005fc_005fhook"><span class="category-def">C Hook: </span><span><strong class="def-name">scm_after_sweep_c_hook</strong><a class="copiable-link" href="#index-scm_005fafter_005fsweep_005fc_005fhook"> ¶</a></span></dt>
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<dd><p>C hook called after the end of the sweep phase of garbage collection,
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but while the GC thread is still inside its critical section.
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</p></dd></dl>
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<dl class="first-defvr">
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<dt class="defvr" id="index-scm_005fafter_005fgc_005fc_005fhook"><span class="category-def">C Hook: </span><span><strong class="def-name">scm_after_gc_c_hook</strong><a class="copiable-link" href="#index-scm_005fafter_005fgc_005fc_005fhook"> ¶</a></span></dt>
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<dd><p>C hook called at the very end of a garbage collection, after the GC
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thread has left its critical section.
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</p></dd></dl>
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<dl class="first-defvr">
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<dt class="defvr" id="index-after_002dgc_002dhook"><span class="category-def">Scheme Hook: </span><span><strong class="def-name">after-gc-hook</strong><a class="copiable-link" href="#index-after_002dgc_002dhook"> ¶</a></span></dt>
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<dd><a class="index-entry-id" id="index-scm_005fafter_005fgc_005fhook"></a>
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<p>Scheme hook with arity 0. This hook is run asynchronously
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(see <a class="pxref" href="Asyncs.html">Asynchronous Interrupts</a>) soon after the GC has completed and any other events
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that were deferred during garbage collection have been processed. (Also
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accessible from C with the name <code class="code">scm_after_gc_hook</code>.)
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</p></dd></dl>
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<p>All the C hooks listed here have type <code class="code">SCM_C_HOOK_NORMAL</code>, are
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initialized with hook closure data NULL, are invoked by
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<code class="code">scm_c_hook_run</code> with call closure data NULL.
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</p>
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<a class="index-entry-id" id="index-guardians_002c-testing-for-GC_0027d-objects"></a>
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<p>The Scheme hook <code class="code">after-gc-hook</code> is particularly useful in
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conjunction with guardians (see <a class="pxref" href="Guardians.html">Guardians</a>). Typically, if you are
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using a guardian, you want to call the guardian after garbage collection
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to see if any of the objects added to the guardian have been collected.
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By adding a thunk that performs this call to <code class="code">after-gc-hook</code>, you
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can ensure that your guardian is tested after every garbage collection
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cycle.
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</p>
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</div>
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<hr>
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<div class="nav-panel">
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<p>
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Next: <a href="REPL-Hooks.html">Hooks into the Guile REPL</a>, Previous: <a href="C-Hooks.html">Hooks For C Code.</a>, Up: <a href="Hooks.html">Hooks</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html" title="Index" rel="index">Index</a>]</p>
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</div>
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</body>
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</html>
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