1 <?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
3 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
5 <!-- SPDX-License-Identifier: LGPL-2.1+ -->
7 <refentry id="sd_event_source_set_destroy_callback"
8 xmlns:xi="http://www.w3.org/2001/XInclude">
11 <title>sd_event_source_set_destroy_callback</title>
12 <productname>elogind</productname>
16 <refentrytitle>sd_event_source_set_destroy_callback</refentrytitle>
17 <manvolnum>3</manvolnum>
21 <refname>sd_event_source_set_destroy_callback</refname>
22 <refname>sd_event_source_get_destroy_callback</refname>
23 <refname>sd_event_destroy_t</refname>
25 <refpurpose>Define the callback function for resource cleanup.</refpurpose>
30 <funcsynopsisinfo>#include <elogind/sd-event.h></funcsynopsisinfo>
33 <funcdef>typedef int (*<function>sd_event_destroy_t</function>)</funcdef>
34 <paramdef>void *<parameter>userdata</parameter></paramdef>
38 <funcdef>int <function>sd_event_source_set_destroy_callback</function></funcdef>
39 <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
40 <paramdef>sd_event_destroy_t <parameter>callback</parameter></paramdef>
44 <funcdef>int <function>sd_event_source_get_destroy_callback</function></funcdef>
45 <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
46 <paramdef>sd_event_destroy_t *<parameter>callback</parameter></paramdef>
53 <title>Description</title>
55 <para><function>sd_event_source_set_destroy_callback()</function> sets <parameter>callback</parameter> as the
56 callback function to be called right before the event source object <parameter>source</parameter> is
57 deallocated. The <parameter>userdata</parameter> pointer from the event source object will be passed as the
58 <parameter>userdata</parameter> parameter. This pointer can be set by an argument to the constructor functions, see
59 <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>, or directly,
61 <citerefentry><refentrytitle>sd_event_source_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
62 This callback function is called even if <parameter>userdata</parameter> is <constant>NULL</constant>. Note that
63 this callback is invoked at a time where the event source object itself is already invalidated, and executing
64 operations or taking new references to the event source object is not permissible.</para>
66 <para><function>sd_event_source_get_destroy_callback()</function> returns the current callback
67 for <parameter>source</parameter> in the <parameter>callback</parameter> parameter.</para>
71 <title>Return Value</title>
73 <para>On success, <function>sd_event_source_set_destroy_callback()</function> returns 0 or a positive integer. On
74 failure, it returns a negative errno-style error code.</para>
76 <para><function>sd_event_source_get_destroy_callback()</function> returns positive if the destroy callback function
77 is set, 0 if not. On failure, returns a negative errno-style error code.</para>
83 <para>Returned errors may indicate the following problems:</para>
87 <term><constant>-EINVAL</constant></term>
89 <listitem><para>The <parameter>source</parameter> parameter is <constant>NULL</constant>.</para></listitem>
94 <xi:include href="libelogind-pkgconfig.xml" />
97 <title>See Also</title>
100 <citerefentry><refentrytitle>elogind</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>