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<?xml version='1.0'?>
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
<refentry id="sd_bus_slot_ref" xmlns:xi="http://www.w3.org/2001/XInclude">
<refentryinfo>
<title>sd_bus_slot_ref</title>
<productname>systemd</productname>
</refentryinfo>
<refmeta>
<refentrytitle>sd_bus_slot_ref</refentrytitle>
<manvolnum>3</manvolnum>
</refmeta>
<refnamediv>
<refname>sd_bus_slot_ref</refname>
<refname>sd_bus_slot_unref</refname>
<refname>sd_bus_slot_unrefp</refname>
<refpurpose>Create and destroy references to a bus slot object</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis>
<funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo>
<funcprototype>
<funcdef>sd_bus_slot *<function>sd_bus_slot_ref</function></funcdef>
<paramdef>sd_bus_slot *<parameter>slot</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>sd_bus_slot *<function>sd_bus_slot_unref</function></funcdef>
<paramdef>sd_bus_slot *<parameter>slot</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>void <function>sd_bus_slot_unrefp</function></funcdef>
<paramdef>sd_bus_slot **<parameter>slotp</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para><function>sd_bus_slot_ref()</function> increases the internal reference counter of
<parameter>slot</parameter> by one.</para>
<para><function>sd_bus_slot_unref()</function> decreases the internal reference counter of
<parameter>slot</parameter> by one. Once the reference count has dropped to zero, slot object is
destroyed and cannot be used anymore, so further calls to <function>sd_bus_slot_ref()</function>
or <function>sd_bus_slot_unref()</function> are illegal.</para>
<para><function>sd_bus_slot_unrefp()</function> is similar to
<function>sd_bus_slot_unref()</function> but takes a pointer to a pointer to an
<type>sd_bus_slot</type> object. This call is useful in conjunction with GCC's and LLVM's <ulink
url="https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html">Clean-up Variable
Attribute</ulink>. See
<citerefentry><refentrytitle>sd_bus_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>
for an example how to use the cleanup attribute.</para>
<para><function>sd_bus_slot_ref()</function> and <function>sd_bus_slot_unref()</function>
execute no operation if the passed in bus object address is
<constant>NULL</constant>. <function>sd_bus_slot_unrefp()</function> will first dereference
its argument, which must not be <constant>NULL</constant>, and will execute no operation if
<emphasis>that</emphasis> is <constant>NULL</constant>.</para>
</refsect1>
<refsect1>
<title>Return Value</title>
<para><function>sd_bus_slot_ref()</function> always returns the argument.</para>
<para><function>sd_bus_slot_unref()</function> always returns <constant>NULL</constant>.</para>
</refsect1>
<xi:include href="libsystemd-pkgconfig.xml" />
<refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_bus_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_bus_message_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_bus_call_method_async</refentrytitle><manvolnum>3</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>
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