man/sd_event_source_unref.xml

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   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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   4
   5 <!--
   6   SPDX-License-Identifier: LGPL-2.1+
   7 -->
   8
   9 <refentry id="sd_event_source_unref" xmlns:xi="http://www.w3.org/2001/XInclude">
  10
  11   <refentryinfo>
  12     <title>sd_event_source_unref</title>
  13     <productname>systemd</productname>
  14   </refentryinfo>
  15
  16   <refmeta>
  17     <refentrytitle>sd_event_source_unref</refentrytitle>
  18     <manvolnum>3</manvolnum>
  19   </refmeta>
  20
  21   <refnamediv>
  22     <refname>sd_event_source_unref</refname>
  23     <refname>sd_event_source_unrefp</refname>
  24     <refname>sd_event_source_ref</refname>
  25
  26     <refpurpose>Increase or decrease event source reference counters</refpurpose>
  27   </refnamediv>
  28
  29   <refsynopsisdiv>
  30     <funcsynopsis>
  31       <funcsynopsisinfo>#include &lt;systemd/sd-event.h&gt;</funcsynopsisinfo>
  32
  33       <funcprototype>
  34         <funcdef>sd_event_source* <function>sd_event_source_unref</function></funcdef>
  35         <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
  36       </funcprototype>
  37
  38       <funcprototype>
  39         <funcdef>void <function>sd_event_source_unrefp</function></funcdef>
  40         <paramdef>sd_event_source **<parameter>source</parameter></paramdef>
  41       </funcprototype>
  42
  43       <funcprototype>
  44         <funcdef>sd_event_source* <function>sd_event_source_ref</function></funcdef>
  45         <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
  46       </funcprototype>
  47
  48     </funcsynopsis>
  49   </refsynopsisdiv>
  50
  51   <refsect1>
  52     <title>Description</title>
  53
  54     <para><function>sd_event_source_unref()</function> may be used to
  55     decrement by one the reference counter of the event source object
  56     specified as <parameter>source</parameter>. The reference counter
  57     is initially set to one, when the event source is created with calls
  58     such as
  59     <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  60     or
  61     <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>. When
  62     the reference counter reaches zero it is removed from its event loop
  63     object and destroyed.</para>
  64
  65     <para><function>sd_event_source_unrefp()</function> is similar to
  66     <function>sd_event_source_unref()</function> but takes a pointer to a
  67     pointer to an <type>sd_event_source</type> object. This call is useful in
  68     conjunction with GCC's and LLVM's <ulink
  69     url="https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html">Clean-up
  70     Variable Attribute</ulink>. Note that this function is defined as
  71     inline function.</para>
  72
  73     <para><function>sd_event_source_ref()</function> may be used
  74     to increase by one the reference counter of the event source object
  75     specified as <parameter>source</parameter>.</para>
  76
  77     <para><function>sd_event_source_unref()</function>,
  78     <function>sd_bus_creds_unrefp()</function> and
  79     <function>sd_bus_creds_ref()</function> execute no operation if
  80     the passed event source object is
  81     <constant>NULL</constant>.</para>
  82
  83     <para>Note that event source objects stay alive and may be
  84     dispatched as long as they have a reference counter greater than
  85     zero. In order to drop a reference of an event source and make
  86     sure the associated event source handler function is not called
  87     anymore it is recommended to combine a call of
  88     <function>sd_event_source_unref()</function> with a prior call to
  89     <function>sd_event_source_set_enabled()</function> with
  90     <constant>SD_EVENT_OFF</constant>.</para>
  91   </refsect1>
  92
  93   <refsect1>
  94     <title>Return Value</title>
  95
  96     <para><function>sd_event_source_unref()</function> always returns
  97     <constant>NULL</constant>.
  98     <function>sd_event_source_ref()</function> always returns the
  99     event source object passed in.</para>
 100   </refsect1>
 101
 102   <xi:include href="libelogind-pkgconfig.xml" />
 103
 104   <refsect1>
 105     <title>See Also</title>
 106
 107     <para>
 108       <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 109       <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 110       <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 111       <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 112       <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 113       <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 114       <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 115     </para>
 116   </refsect1>
 117
 118 </refentry>