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">
6 SPDX-License-Identifier: LGPL-2.1+
8 This file is part of systemd.
10 Copyright 2015 Lennart Poettering
13 <refentry id="sd_event_source_unref" xmlns:xi="http://www.w3.org/2001/XInclude">
16 <title>sd_event_source_unref</title>
17 <productname>systemd</productname>
21 <contrib>Developer</contrib>
22 <firstname>Lennart</firstname>
23 <surname>Poettering</surname>
24 <email>lennart@poettering.net</email>
30 <refentrytitle>sd_event_source_unref</refentrytitle>
31 <manvolnum>3</manvolnum>
35 <refname>sd_event_source_unref</refname>
36 <refname>sd_event_source_unrefp</refname>
37 <refname>sd_event_source_ref</refname>
39 <refpurpose>Increase or decrease event source reference counters</refpurpose>
44 <funcsynopsisinfo>#include <systemd/sd-event.h></funcsynopsisinfo>
47 <funcdef>sd_event_source* <function>sd_event_source_unref</function></funcdef>
48 <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
52 <funcdef>void <function>sd_event_source_unrefp</function></funcdef>
53 <paramdef>sd_event_source **<parameter>source</parameter></paramdef>
57 <funcdef>sd_event_source* <function>sd_event_source_ref</function></funcdef>
58 <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
65 <title>Description</title>
67 <para><function>sd_event_source_unref()</function> may be used to
68 decrement by one the reference counter of the event source object
69 specified as <parameter>source</parameter>. The reference counter
70 is initially set to one, when the event source is created with calls
72 <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>
74 <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>. When
75 the reference counter reaches zero it is removed from its event loop
76 object and destroyed.</para>
78 <para><function>sd_event_source_unrefp()</function> is similar to
79 <function>sd_event_source_unref()</function> but takes a pointer to a
80 pointer to an <type>sd_event_source</type> object. This call is useful in
81 conjunction with GCC's and LLVM's <ulink
82 url="https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html">Clean-up
83 Variable Attribute</ulink>. Note that this function is defined as
84 inline function.</para>
86 <para><function>sd_event_source_ref()</function> may be used
87 to increase by one the reference counter of the event source object
88 specified as <parameter>source</parameter>.</para>
90 <para><function>sd_event_source_unref()</function>,
91 <function>sd_bus_creds_unrefp()</function> and
92 <function>sd_bus_creds_ref()</function> execute no operation if
93 the passed event source object is
94 <constant>NULL</constant>.</para>
96 <para>Note that event source objects stay alive and may be
97 dispatched as long as they have a reference counter greater than
98 zero. In order to drop a reference of an event source and make
99 sure the associated event source handler function is not called
100 anymore it is recommended to combine a call of
101 <function>sd_event_source_unref()</function> with a prior call to
102 <function>sd_event_source_set_enabled()</function> with
103 <constant>SD_EVENT_OFF</constant>.</para>
107 <title>Return Value</title>
109 <para><function>sd_event_source_unref()</function> always returns
110 <constant>NULL</constant>.
111 <function>sd_event_source_ref()</function> always returns the
112 event source object passed in.</para>
115 <xi:include href="libelogind-pkgconfig.xml" />
118 <title>See Also</title>
121 <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
122 <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
123 <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
124 <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
125 <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
126 <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
127 <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>