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+ -->
6 <refentry id=
"sd_bus_slot_ref" xmlns:
xi=
"http://www.w3.org/2001/XInclude">
8 <title>sd_bus_slot_ref
</title>
9 <productname>systemd
</productname>
13 <refentrytitle>sd_bus_slot_ref
</refentrytitle>
14 <manvolnum>3</manvolnum>
18 <refname>sd_bus_slot_ref
</refname>
19 <refname>sd_bus_slot_unref
</refname>
20 <refname>sd_bus_slot_unrefp
</refname>
21 <refname>sd_bus_slot_get_bus
</refname>
23 <refpurpose>Create and destroy references to a bus slot object
</refpurpose>
28 <funcsynopsisinfo>#include
<systemd/sd-bus.h
></funcsynopsisinfo>
31 <funcdef>sd_bus_slot *
<function>sd_bus_slot_ref
</function></funcdef>
32 <paramdef>sd_bus_slot *
<parameter>slot
</parameter></paramdef>
36 <funcdef>sd_bus_slot *
<function>sd_bus_slot_unref
</function></funcdef>
37 <paramdef>sd_bus_slot *
<parameter>slot
</parameter></paramdef>
41 <funcdef>void
<function>sd_bus_slot_unrefp
</function></funcdef>
42 <paramdef>sd_bus_slot **
<parameter>slotp
</parameter></paramdef>
46 <funcdef>sd_bus *
<function>sd_bus_slot_get_bus
</function></funcdef>
47 <paramdef>sd_bus_slot *
<parameter>m
</parameter></paramdef>
53 <title>Description
</title>
55 <para><function>sd_bus_slot_ref()
</function> increases the reference counter of
56 <parameter>slot
</parameter> by one.
</para>
58 <para><function>sd_bus_slot_unref()
</function> decreases the reference counter of
59 <parameter>slot
</parameter> by one. Once the reference count has dropped to zero, slot object is
60 destroyed and cannot be used anymore, so further calls to
<function>sd_bus_slot_ref()
</function>
61 or
<function>sd_bus_slot_unref()
</function> are illegal.
</para>
63 <para><function>sd_bus_slot_unrefp()
</function> is similar to
64 <function>sd_bus_slot_unref()
</function> but takes a pointer to a pointer to an
65 <type>sd_bus_slot
</type> object. This call is useful in conjunction with GCC's and LLVM's
<ulink
66 url=
"https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html">Clean-up Variable
67 Attribute
</ulink>. See
68 <citerefentry><refentrytitle>sd_bus_new
</refentrytitle><manvolnum>3</manvolnum></citerefentry>
69 for an example how to use the cleanup attribute.
</para>
71 <para><function>sd_bus_slot_ref()
</function> and
<function>sd_bus_slot_unref()
</function>
72 execute no operation if the passed in bus object address is
73 <constant>NULL
</constant>.
<function>sd_bus_slot_unrefp()
</function> will first dereference
74 its argument, which must not be
<constant>NULL
</constant>, and will execute no operation if
75 <emphasis>that
</emphasis> is
<constant>NULL
</constant>.
78 <para><function>sd_bus_slot_get_bus()
</function> returns the bus object that message
79 <parameter>slot
</parameter> is attached to.
</para>
83 <title>Return Value
</title>
85 <para><function>sd_bus_slot_ref()
</function> always returns the argument.
</para>
87 <para><function>sd_bus_slot_unref()
</function> always returns
<constant>NULL
</constant>.
</para>
89 <para><function>sd_bus_slot_get_bus()
</function> always returns the bus object.
</para>
92 <xi:include href=
"libsystemd-pkgconfig.xml" />
95 <title>See Also
</title>
98 <citerefentry><refentrytitle>systemd
</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
99 <citerefentry><refentrytitle>sd-bus
</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
100 <citerefentry><refentrytitle>sd_bus_new
</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
101 <citerefentry><refentrytitle>sd_bus_message_new
</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
102 <citerefentry><refentrytitle>sd_bus_slot_new_signal
</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
103 <citerefentry><refentrytitle>sd_bus_call_method_async
</refentrytitle><manvolnum>3</manvolnum></citerefentry>