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-or-later -->
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>
22 <refpurpose>Create and destroy references to a bus slot object
</refpurpose>
27 <funcsynopsisinfo>#include
<systemd/sd-bus.h
></funcsynopsisinfo>
30 <funcdef>sd_bus_slot *
<function>sd_bus_slot_ref
</function></funcdef>
31 <paramdef>sd_bus_slot *
<parameter>slot
</parameter></paramdef>
35 <funcdef>sd_bus_slot *
<function>sd_bus_slot_unref
</function></funcdef>
36 <paramdef>sd_bus_slot *
<parameter>slot
</parameter></paramdef>
40 <funcdef>void
<function>sd_bus_slot_unrefp
</function></funcdef>
41 <paramdef>sd_bus_slot **
<parameter>slotp
</parameter></paramdef>
47 <title>Description
</title>
49 <para><function>sd_bus_slot_ref()
</function> increases the reference counter of
50 <parameter>slot
</parameter> by one.
</para>
52 <para><function>sd_bus_slot_unref()
</function> decreases the reference counter of
53 <parameter>slot
</parameter> by one. Once the reference count has dropped to zero, slot object is
54 destroyed and cannot be used anymore, so further calls to
<function>sd_bus_slot_ref()
</function>
55 or
<function>sd_bus_slot_unref()
</function> are illegal.
</para>
57 <para><function>sd_bus_slot_unrefp()
</function> is similar to
58 <function>sd_bus_slot_unref()
</function> but takes a pointer to a pointer to an
59 <type>sd_bus_slot
</type> object. This call is useful in conjunction with GCC's and LLVM's
<ulink
60 url=
"https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html">Clean-up Variable
61 Attribute
</ulink>. See
62 <citerefentry><refentrytitle>sd_bus_new
</refentrytitle><manvolnum>3</manvolnum></citerefentry>
63 for an example how to use the cleanup attribute.
</para>
65 <para><function>sd_bus_slot_ref()
</function> and
<function>sd_bus_slot_unref()
</function>
66 execute no operation if the passed in bus object address is
67 <constant>NULL
</constant>.
<function>sd_bus_slot_unrefp()
</function> will first dereference
68 its argument, which must not be
<constant>NULL
</constant>, and will execute no operation if
69 <emphasis>that
</emphasis> is
<constant>NULL
</constant>.
</para>
73 <title>Return Value
</title>
75 <para><function>sd_bus_slot_ref()
</function> always returns the argument.
</para>
77 <para><function>sd_bus_slot_unref()
</function> always returns
<constant>NULL
</constant>.
</para>
80 <xi:include href=
"libsystemd-pkgconfig.xml" />
83 <title>See Also
</title>
86 <citerefentry><refentrytitle>systemd
</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
87 <citerefentry><refentrytitle>sd-bus
</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
88 <citerefentry><refentrytitle>sd_bus_new
</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
89 <citerefentry><refentrytitle>sd_bus_message_new
</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
90 <citerefentry><refentrytitle>sd_bus_call_method_async
</refentrytitle><manvolnum>3</manvolnum></citerefentry>