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 Copyright 2015 Lennart Poettering
11 <refentry id="sd_event_source_unref" xmlns:xi="http://www.w3.org/2001/XInclude">
14 <title>sd_event_source_unref</title>
15 <productname>systemd</productname>
19 <contrib>Developer</contrib>
20 <firstname>Lennart</firstname>
21 <surname>Poettering</surname>
22 <email>lennart@poettering.net</email>
28 <refentrytitle>sd_event_source_unref</refentrytitle>
29 <manvolnum>3</manvolnum>
33 <refname>sd_event_source_unref</refname>
34 <refname>sd_event_source_unrefp</refname>
35 <refname>sd_event_source_ref</refname>
37 <refpurpose>Increase or decrease event source reference counters</refpurpose>
42 <funcsynopsisinfo>#include <systemd/sd-event.h></funcsynopsisinfo>
45 <funcdef>sd_event_source* <function>sd_event_source_unref</function></funcdef>
46 <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
50 <funcdef>void <function>sd_event_source_unrefp</function></funcdef>
51 <paramdef>sd_event_source **<parameter>source</parameter></paramdef>
55 <funcdef>sd_event_source* <function>sd_event_source_ref</function></funcdef>
56 <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
63 <title>Description</title>
65 <para><function>sd_event_source_unref()</function> may be used to
66 decrement by one the reference counter of the event source object
67 specified as <parameter>source</parameter>. The reference counter
68 is initially set to one, when the event source is created with calls
70 <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>
72 <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>. When
73 the reference counter reaches zero it is removed from its event loop
74 object and destroyed.</para>
76 <para><function>sd_event_source_unrefp()</function> is similar to
77 <function>sd_event_source_unref()</function> but takes a pointer to a
78 pointer to an <type>sd_event_source</type> object. This call is useful in
79 conjunction with GCC's and LLVM's <ulink
80 url="https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html">Clean-up
81 Variable Attribute</ulink>. Note that this function is defined as
82 inline function.</para>
84 <para><function>sd_event_source_ref()</function> may be used
85 to increase by one the reference counter of the event source object
86 specified as <parameter>source</parameter>.</para>
88 <para><function>sd_event_source_unref()</function>,
89 <function>sd_bus_creds_unrefp()</function> and
90 <function>sd_bus_creds_ref()</function> execute no operation if
91 the passed event source object is
92 <constant>NULL</constant>.</para>
94 <para>Note that event source objects stay alive and may be
95 dispatched as long as they have a reference counter greater than
96 zero. In order to drop a reference of an event source and make
97 sure the associated event source handler function is not called
98 anymore it is recommended to combine a call of
99 <function>sd_event_source_unref()</function> with a prior call to
100 <function>sd_event_source_set_enabled()</function> with
101 <constant>SD_EVENT_OFF</constant>.</para>
105 <title>Return Value</title>
107 <para><function>sd_event_source_unref()</function> always returns
108 <constant>NULL</constant>.
109 <function>sd_event_source_ref()</function> always returns the
110 event source object passed in.</para>
113 <xi:include href="libelogind-pkgconfig.xml" />
116 <title>See Also</title>
119 <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
120 <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
121 <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
122 <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
123 <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
124 <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
125 <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>