man/sd_event_source_unref.xml

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   5 <!--
   6   SPDX-License-Identifier: LGPL-2.1+
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   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
  15     <authorgroup>
  16       <author>
  17         <contrib>Developer</contrib>
  18         <firstname>Lennart</firstname>
  19         <surname>Poettering</surname>
  20         <email>lennart@poettering.net</email>
  21       </author>
  22     </authorgroup>
  23   </refentryinfo>
  24
  25   <refmeta>
  26     <refentrytitle>sd_event_source_unref</refentrytitle>
  27     <manvolnum>3</manvolnum>
  28   </refmeta>
  29
  30   <refnamediv>
  31     <refname>sd_event_source_unref</refname>
  32     <refname>sd_event_source_unrefp</refname>
  33     <refname>sd_event_source_ref</refname>
  34
  35     <refpurpose>Increase or decrease event source reference counters</refpurpose>
  36   </refnamediv>
  37
  38   <refsynopsisdiv>
  39     <funcsynopsis>
  40       <funcsynopsisinfo>#include &lt;systemd/sd-event.h&gt;</funcsynopsisinfo>
  41
  42       <funcprototype>
  43         <funcdef>sd_event_source* <function>sd_event_source_unref</function></funcdef>
  44         <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
  45       </funcprototype>
  46
  47       <funcprototype>
  48         <funcdef>void <function>sd_event_source_unrefp</function></funcdef>
  49         <paramdef>sd_event_source **<parameter>source</parameter></paramdef>
  50       </funcprototype>
  51
  52       <funcprototype>
  53         <funcdef>sd_event_source* <function>sd_event_source_ref</function></funcdef>
  54         <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
  55       </funcprototype>
  56
  57     </funcsynopsis>
  58   </refsynopsisdiv>
  59
  60   <refsect1>
  61     <title>Description</title>
  62
  63     <para><function>sd_event_source_unref()</function> may be used to
  64     decrement by one the reference counter of the event source object
  65     specified as <parameter>source</parameter>. The reference counter
  66     is initially set to one, when the event source is created with calls
  67     such as
  68     <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  69     or
  70     <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>. When
  71     the reference counter reaches zero it is removed from its event loop
  72     object and destroyed.</para>
  73
  74     <para><function>sd_event_source_unrefp()</function> is similar to
  75     <function>sd_event_source_unref()</function> but takes a pointer to a
  76     pointer to an <type>sd_event_source</type> object. This call is useful in
  77     conjunction with GCC's and LLVM's <ulink
  78     url="https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html">Clean-up
  79     Variable Attribute</ulink>. Note that this function is defined as
  80     inline function.</para>
  81
  82     <para><function>sd_event_source_ref()</function> may be used
  83     to increase by one the reference counter of the event source object
  84     specified as <parameter>source</parameter>.</para>
  85
  86     <para><function>sd_event_source_unref()</function>,
  87     <function>sd_bus_creds_unrefp()</function> and
  88     <function>sd_bus_creds_ref()</function> execute no operation if
  89     the passed event source object is
  90     <constant>NULL</constant>.</para>
  91
  92     <para>Note that event source objects stay alive and may be
  93     dispatched as long as they have a reference counter greater than
  94     zero. In order to drop a reference of an event source and make
  95     sure the associated event source handler function is not called
  96     anymore it is recommended to combine a call of
  97     <function>sd_event_source_unref()</function> with a prior call to
  98     <function>sd_event_source_set_enabled()</function> with
  99     <constant>SD_EVENT_OFF</constant>.</para>
 100   </refsect1>
 101
 102   <refsect1>
 103     <title>Return Value</title>
 104
 105     <para><function>sd_event_source_unref()</function> always returns
 106     <constant>NULL</constant>.
 107     <function>sd_event_source_ref()</function> always returns the
 108     event source object passed in.</para>
 109   </refsect1>
 110
 111   <xi:include href="libsystemd-pkgconfig.xml" />
 112
 113   <refsect1>
 114     <title>See Also</title>
 115
 116     <para>
 117       <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 118       <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 119       <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 120       <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 121       <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 122       <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 123       <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 124     </para>
 125   </refsect1>
 126
 127 </refentry>