1<?xml version='1.0'?> 2<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" 3 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> 4<!-- SPDX-License-Identifier: LGPL-2.1-or-later --> 5 6<refentry id="sd_event_source_set_destroy_callback" 7 xmlns:xi="http://www.w3.org/2001/XInclude"> 8 9 <refentryinfo> 10 <title>sd_event_source_set_destroy_callback</title> 11 <productname>systemd</productname> 12 </refentryinfo> 13 14 <refmeta> 15 <refentrytitle>sd_event_source_set_destroy_callback</refentrytitle> 16 <manvolnum>3</manvolnum> 17 </refmeta> 18 19 <refnamediv> 20 <refname>sd_event_source_set_destroy_callback</refname> 21 <refname>sd_event_source_get_destroy_callback</refname> 22 <refname>sd_event_destroy_t</refname> 23 24 <refpurpose>Define the callback function for resource cleanup</refpurpose> 25 </refnamediv> 26 27 <refsynopsisdiv> 28 <funcsynopsis> 29 <funcsynopsisinfo>#include <systemd/sd-event.h></funcsynopsisinfo> 30 31 <funcprototype> 32 <funcdef>typedef int (*<function>sd_event_destroy_t</function>)</funcdef> 33 <paramdef>void *<parameter>userdata</parameter></paramdef> 34 </funcprototype> 35 36 <funcprototype> 37 <funcdef>int <function>sd_event_source_set_destroy_callback</function></funcdef> 38 <paramdef>sd_event_source *<parameter>source</parameter></paramdef> 39 <paramdef>sd_event_destroy_t <parameter>callback</parameter></paramdef> 40 </funcprototype> 41 42 <funcprototype> 43 <funcdef>int <function>sd_event_source_get_destroy_callback</function></funcdef> 44 <paramdef>sd_event_source *<parameter>source</parameter></paramdef> 45 <paramdef>sd_event_destroy_t *<parameter>callback</parameter></paramdef> 46 </funcprototype> 47 48 </funcsynopsis> 49 </refsynopsisdiv> 50 51 <refsect1> 52 <title>Description</title> 53 54 <para><function>sd_event_source_set_destroy_callback()</function> sets <parameter>callback</parameter> as the 55 callback function to be called right before the event source object <parameter>source</parameter> is 56 deallocated. The <parameter>userdata</parameter> pointer from the event source object will be passed as the 57 <parameter>userdata</parameter> parameter. This pointer can be set by an argument to the constructor functions, see 58 <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>, or directly, 59 see 60 <citerefentry><refentrytitle>sd_event_source_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry>. 61 This callback function is called even if <parameter>userdata</parameter> is <constant>NULL</constant>. Note that 62 this callback is invoked at a time where the event source object itself is already invalidated, and executing 63 operations or taking new references to the event source object is not permissible.</para> 64 65 <para><function>sd_event_source_get_destroy_callback()</function> returns the current callback 66 for <parameter>source</parameter> in the <parameter>callback</parameter> parameter.</para> 67 </refsect1> 68 69 <refsect1> 70 <title>Return Value</title> 71 72 <para>On success, <function>sd_event_source_set_destroy_callback()</function> returns 0 or a positive 73 integer. On failure, it returns a negative errno-style error code.</para> 74 75 <para><function>sd_event_source_get_destroy_callback()</function> returns positive if the destroy 76 callback function is set, 0 if not. On failure, returns a negative errno-style error code.</para> 77 78 <refsect2> 79 <title>Errors</title> 80 81 <para>Returned errors may indicate the following problems:</para> 82 83 <variablelist> 84 <varlistentry> 85 <term><constant>-EINVAL</constant></term> 86 87 <listitem><para>The <parameter>source</parameter> parameter is <constant>NULL</constant>. 88 </para></listitem> 89 </varlistentry> 90 </variablelist> 91 </refsect2> 92 </refsect1> 93 94 <xi:include href="libsystemd-pkgconfig.xml" /> 95 96 <refsect1> 97 <title>See Also</title> 98 99 <para> 100 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, 101 <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>, 102 <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>, 103 <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>, 104 <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>, 105 <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>, 106 <citerefentry><refentrytitle>sd_event_add_inotify</refentrytitle><manvolnum>3</manvolnum></citerefentry>, 107 <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>, 108 <citerefentry><refentrytitle>sd_event_source_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry> 109 </para> 110 </refsect1> 111 112</refentry> 113