man/sd_event_source_unref.xml

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   5 <!--
   6   SPDX-License-Identifier: LGPL-2.1+
   7
   8   Copyright 2015 Lennart Poettering
   9 -->
  10
  11 <refentry id="sd_event_source_unref" xmlns:xi="http://www.w3.org/2001/XInclude">
  12
  13   <refentryinfo>
  14     <title>sd_event_source_unref</title>
  15     <productname>systemd</productname>
  16
  17     <authorgroup>
  18       <author>
  19         <contrib>Developer</contrib>
  20         <firstname>Lennart</firstname>
  21         <surname>Poettering</surname>
  22         <email>lennart@poettering.net</email>
  23       </author>
  24     </authorgroup>
  25   </refentryinfo>
  26
  27   <refmeta>
  28     <refentrytitle>sd_event_source_unref</refentrytitle>
  29     <manvolnum>3</manvolnum>
  30   </refmeta>
  31
  32   <refnamediv>
  33     <refname>sd_event_source_unref</refname>
  34     <refname>sd_event_source_unrefp</refname>
  35     <refname>sd_event_source_ref</refname>
  36
  37     <refpurpose>Increase or decrease event source reference counters</refpurpose>
  38   </refnamediv>
  39
  40   <refsynopsisdiv>
  41     <funcsynopsis>
  42       <funcsynopsisinfo>#include &lt;systemd/sd-event.h&gt;</funcsynopsisinfo>
  43
  44       <funcprototype>
  45         <funcdef>sd_event_source* <function>sd_event_source_unref</function></funcdef>
  46         <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
  47       </funcprototype>
  48
  49       <funcprototype>
  50         <funcdef>void <function>sd_event_source_unrefp</function></funcdef>
  51         <paramdef>sd_event_source **<parameter>source</parameter></paramdef>
  52       </funcprototype>
  53
  54       <funcprototype>
  55         <funcdef>sd_event_source* <function>sd_event_source_ref</function></funcdef>
  56         <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
  57       </funcprototype>
  58
  59     </funcsynopsis>
  60   </refsynopsisdiv>
  61
  62   <refsect1>
  63     <title>Description</title>
  64
  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
  69     such as
  70     <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  71     or
  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>
  75
  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>
  83
  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>
  87
  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>
  93
  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>
 102   </refsect1>
 103
 104   <refsect1>
 105     <title>Return Value</title>
 106
 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>
 111   </refsect1>
 112
 113   <xi:include href="libsystemd-pkgconfig.xml" />
 114
 115   <refsect1>
 116     <title>See Also</title>
 117
 118     <para>
 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>
 126     </para>
 127   </refsect1>
 128
 129 </refentry>