man/sd_event_source_unref.xml

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   5 <!--
   6   SPDX-License-Identifier: LGPL-2.1+
   7
   8   This file is part of systemd.
   9
  10   Copyright 2015 Lennart Poettering
  11 -->
  12
  13 <refentry id="sd_event_source_unref" xmlns:xi="http://www.w3.org/2001/XInclude">
  14
  15   <refentryinfo>
  16     <title>sd_event_source_unref</title>
  17     <productname>systemd</productname>
  18
  19     <authorgroup>
  20       <author>
  21         <contrib>Developer</contrib>
  22         <firstname>Lennart</firstname>
  23         <surname>Poettering</surname>
  24         <email>lennart@poettering.net</email>
  25       </author>
  26     </authorgroup>
  27   </refentryinfo>
  28
  29   <refmeta>
  30     <refentrytitle>sd_event_source_unref</refentrytitle>
  31     <manvolnum>3</manvolnum>
  32   </refmeta>
  33
  34   <refnamediv>
  35     <refname>sd_event_source_unref</refname>
  36     <refname>sd_event_source_unrefp</refname>
  37     <refname>sd_event_source_ref</refname>
  38
  39     <refpurpose>Increase or decrease event source reference counters</refpurpose>
  40   </refnamediv>
  41
  42   <refsynopsisdiv>
  43     <funcsynopsis>
  44       <funcsynopsisinfo>#include &lt;systemd/sd-event.h&gt;</funcsynopsisinfo>
  45
  46       <funcprototype>
  47         <funcdef>sd_event_source* <function>sd_event_source_unref</function></funcdef>
  48         <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
  49       </funcprototype>
  50
  51       <funcprototype>
  52         <funcdef>void <function>sd_event_source_unrefp</function></funcdef>
  53         <paramdef>sd_event_source **<parameter>source</parameter></paramdef>
  54       </funcprototype>
  55
  56       <funcprototype>
  57         <funcdef>sd_event_source* <function>sd_event_source_ref</function></funcdef>
  58         <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
  59       </funcprototype>
  60
  61     </funcsynopsis>
  62   </refsynopsisdiv>
  63
  64   <refsect1>
  65     <title>Description</title>
  66
  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
  71     such as
  72     <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  73     or
  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>
  77
  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>
  85
  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>
  89
  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>
  95
  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>
 104   </refsect1>
 105
 106   <refsect1>
 107     <title>Return Value</title>
 108
 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>
 113   </refsect1>
 114
 115   <xi:include href="libsystemd-pkgconfig.xml" />
 116
 117   <refsect1>
 118     <title>See Also</title>
 119
 120     <para>
 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>
 128     </para>
 129   </refsect1>
 130
 131 </refentry>