man/sd_event_source_unref.xml

   1 <?xml version='1.0'?>
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
   3   "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4 <!-- SPDX-License-Identifier: LGPL-2.1+ -->
   5
   6 <refentry id="sd_event_source_unref" xmlns:xi="http://www.w3.org/2001/XInclude">
   7
   8   <refentryinfo>
   9     <title>sd_event_source_unref</title>
  10     <productname>systemd</productname>
  11   </refentryinfo>
  12
  13   <refmeta>
  14     <refentrytitle>sd_event_source_unref</refentrytitle>
  15     <manvolnum>3</manvolnum>
  16   </refmeta>
  17
  18   <refnamediv>
  19     <refname>sd_event_source_unref</refname>
  20     <refname>sd_event_source_unrefp</refname>
  21     <refname>sd_event_source_ref</refname>
  22
  23     <refpurpose>Increase or decrease event source reference counters</refpurpose>
  24   </refnamediv>
  25
  26   <refsynopsisdiv>
  27     <funcsynopsis>
  28       <funcsynopsisinfo>#include &lt;systemd/sd-event.h&gt;</funcsynopsisinfo>
  29
  30       <funcprototype>
  31         <funcdef>sd_event_source* <function>sd_event_source_unref</function></funcdef>
  32         <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
  33       </funcprototype>
  34
  35       <funcprototype>
  36         <funcdef>void <function>sd_event_source_unrefp</function></funcdef>
  37         <paramdef>sd_event_source **<parameter>source</parameter></paramdef>
  38       </funcprototype>
  39
  40       <funcprototype>
  41         <funcdef>sd_event_source* <function>sd_event_source_ref</function></funcdef>
  42         <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
  43       </funcprototype>
  44
  45     </funcsynopsis>
  46   </refsynopsisdiv>
  47
  48   <refsect1>
  49     <title>Description</title>
  50
  51     <para><function>sd_event_source_unref()</function> may be used to
  52     decrement by one the reference counter of the event source object
  53     specified as <parameter>source</parameter>. The reference counter
  54     is initially set to one, when the event source is created with calls
  55     such as
  56     <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  57     or
  58     <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>. When
  59     the reference counter reaches zero it is removed from its event loop
  60     object and destroyed.</para>
  61
  62     <para><function>sd_event_source_unrefp()</function> is similar to
  63     <function>sd_event_source_unref()</function> but takes a pointer to a
  64     pointer to an <type>sd_event_source</type> object. This call is useful in
  65     conjunction with GCC's and LLVM's <ulink
  66     url="https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html">Clean-up
  67     Variable Attribute</ulink>. Note that this function is defined as
  68     inline function.</para>
  69
  70     <para><function>sd_event_source_ref()</function> may be used
  71     to increase by one the reference counter of the event source object
  72     specified as <parameter>source</parameter>.</para>
  73
  74     <para><function>sd_event_source_unref()</function>,
  75     <function>sd_bus_creds_unrefp()</function> and
  76     <function>sd_bus_creds_ref()</function> execute no operation if
  77     the passed event source object is
  78     <constant>NULL</constant>.</para>
  79
  80     <para>Note that event source objects stay alive and may be
  81     dispatched as long as they have a reference counter greater than
  82     zero. In order to drop a reference of an event source and make
  83     sure the associated event source handler function is not called
  84     anymore it is recommended to combine a call of
  85     <function>sd_event_source_unref()</function> with a prior call to
  86     <function>sd_event_source_set_enabled()</function> with
  87     <constant>SD_EVENT_OFF</constant>.</para>
  88   </refsect1>
  89
  90   <refsect1>
  91     <title>Return Value</title>
  92
  93     <para><function>sd_event_source_unref()</function> always returns
  94     <constant>NULL</constant>.
  95     <function>sd_event_source_ref()</function> always returns the
  96     event source object passed in.</para>
  97   </refsect1>
  98
  99   <xi:include href="libsystemd-pkgconfig.xml" />
 100
 101   <refsect1>
 102     <title>See Also</title>
 103
 104     <para>
 105       <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 106       <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 107       <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 108       <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 109       <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 110       <citerefentry><refentrytitle>sd_event_add_inotify</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 111       <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 112       <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 113     </para>
 114   </refsect1>
 115
 116 </refentry>