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<?xml version='1.0'?>
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< !DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!-- SPDX - License - Identifier: LGPL - 2.1 - or - later -->
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<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>
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<para > <function > sd_bus_slot_ref()</function> increases the internal reference counter of
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<parameter > slot</parameter> by one.</para>
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<para > <function > sd_bus_slot_unref()</function> decreases the internal reference counter of
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<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
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<emphasis > that</emphasis> is <constant > NULL</constant> .</para>
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</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>