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< !DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!-- SPDX - License - Identifier: LGPL - 2.1+ -->
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<refentry id= "sd_event_source_unref" xmlns:xi= "http://www.w3.org/2001/XInclude" >
<refentryinfo >
<title > sd_event_source_unref</title>
<productname > systemd</productname>
</refentryinfo>
<refmeta >
<refentrytitle > sd_event_source_unref</refentrytitle>
<manvolnum > 3</manvolnum>
</refmeta>
<refnamediv >
<refname > sd_event_source_unref</refname>
tree-wide: expose "p"-suffix unref calls in public APIs to make gcc cleanup easy
GLIB has recently started to officially support the gcc cleanup
attribute in its public API, hence let's do the same for our APIs.
With this patch we'll define an xyz_unrefp() call for each public
xyz_unref() call, to make it easy to use inside a
__attribute__((cleanup())) expression. Then, all code is ported over to
make use of this.
The new calls are also documented in the man pages, with examples how to
use them (well, I only added docs where the _unref() call itself already
had docs, and the examples, only cover sd_bus_unrefp() and
sd_event_unrefp()).
This also renames sd_lldp_free() to sd_lldp_unref(), since that's how we
tend to call our destructors these days.
Note that this defines no public macro that wraps gcc's attribute and
makes it easier to use. While I think it's our duty in the library to
make our stuff easy to use, I figure it's not our duty to make gcc's own
features easy to use on its own. Most likely, client code which wants to
make use of this should define its own:
#define _cleanup_(function) __attribute__((cleanup(function)))
Or similar, to make the gcc feature easier to use.
Making this logic public has the benefit that we can remove three header
files whose only purpose was to define these functions internally.
See #2008.
2015-11-27 21:13:45 +03:00
<refname > sd_event_source_unrefp</refname>
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<refname > sd_event_source_ref</refname>
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<refname > sd_event_source_disable_unref</refname>
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<refname > sd_event_source_disable_unrefp</refname>
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<refpurpose > Increase or decrease event source reference counters</refpurpose>
</refnamediv>
<refsynopsisdiv >
<funcsynopsis >
<funcsynopsisinfo > #include < systemd/sd-event.h> </funcsynopsisinfo>
<funcprototype >
<funcdef > sd_event_source* <function > sd_event_source_unref</function> </funcdef>
<paramdef > sd_event_source *<parameter > source</parameter> </paramdef>
</funcprototype>
tree-wide: expose "p"-suffix unref calls in public APIs to make gcc cleanup easy
GLIB has recently started to officially support the gcc cleanup
attribute in its public API, hence let's do the same for our APIs.
With this patch we'll define an xyz_unrefp() call for each public
xyz_unref() call, to make it easy to use inside a
__attribute__((cleanup())) expression. Then, all code is ported over to
make use of this.
The new calls are also documented in the man pages, with examples how to
use them (well, I only added docs where the _unref() call itself already
had docs, and the examples, only cover sd_bus_unrefp() and
sd_event_unrefp()).
This also renames sd_lldp_free() to sd_lldp_unref(), since that's how we
tend to call our destructors these days.
Note that this defines no public macro that wraps gcc's attribute and
makes it easier to use. While I think it's our duty in the library to
make our stuff easy to use, I figure it's not our duty to make gcc's own
features easy to use on its own. Most likely, client code which wants to
make use of this should define its own:
#define _cleanup_(function) __attribute__((cleanup(function)))
Or similar, to make the gcc feature easier to use.
Making this logic public has the benefit that we can remove three header
files whose only purpose was to define these functions internally.
See #2008.
2015-11-27 21:13:45 +03:00
<funcprototype >
<funcdef > void <function > sd_event_source_unrefp</function> </funcdef>
<paramdef > sd_event_source **<parameter > source</parameter> </paramdef>
</funcprototype>
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<funcprototype >
<funcdef > sd_event_source* <function > sd_event_source_ref</function> </funcdef>
<paramdef > sd_event_source *<parameter > source</parameter> </paramdef>
</funcprototype>
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<funcprototype >
<funcdef > sd_event_source* <function > sd_event_source_disable_unref</function> </funcdef>
<paramdef > sd_event_source *<parameter > source</parameter> </paramdef>
</funcprototype>
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<funcprototype >
<funcdef > void <function > sd_event_source_disable_unrefp</function> </funcdef>
<paramdef > sd_event_source **<parameter > source</parameter> </paramdef>
</funcprototype>
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</funcsynopsis>
</refsynopsisdiv>
<refsect1 >
<title > Description</title>
<para > <function > sd_event_source_unref()</function> may be used to
decrement by one the reference counter of the event source object
specified as <parameter > source</parameter> . The reference counter
is initially set to one, when the event source is created with calls
such as
<citerefentry > <refentrytitle > sd_event_add_io</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry>
or
<citerefentry > <refentrytitle > sd_event_add_time</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry> . When
the reference counter reaches zero it is removed from its event loop
object and destroyed.</para>
tree-wide: expose "p"-suffix unref calls in public APIs to make gcc cleanup easy
GLIB has recently started to officially support the gcc cleanup
attribute in its public API, hence let's do the same for our APIs.
With this patch we'll define an xyz_unrefp() call for each public
xyz_unref() call, to make it easy to use inside a
__attribute__((cleanup())) expression. Then, all code is ported over to
make use of this.
The new calls are also documented in the man pages, with examples how to
use them (well, I only added docs where the _unref() call itself already
had docs, and the examples, only cover sd_bus_unrefp() and
sd_event_unrefp()).
This also renames sd_lldp_free() to sd_lldp_unref(), since that's how we
tend to call our destructors these days.
Note that this defines no public macro that wraps gcc's attribute and
makes it easier to use. While I think it's our duty in the library to
make our stuff easy to use, I figure it's not our duty to make gcc's own
features easy to use on its own. Most likely, client code which wants to
make use of this should define its own:
#define _cleanup_(function) __attribute__((cleanup(function)))
Or similar, to make the gcc feature easier to use.
Making this logic public has the benefit that we can remove three header
files whose only purpose was to define these functions internally.
See #2008.
2015-11-27 21:13:45 +03:00
<para > <function > sd_event_source_unrefp()</function> is similar to
<function > sd_event_source_unref()</function> but takes a pointer to a
pointer to an <type > sd_event_source</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> . Note that this function is defined as
inline function.</para>
2015-11-20 01:38:54 +03:00
<para > <function > sd_event_source_ref()</function> may be used
to increase by one the reference counter of the event source object
specified as <parameter > source</parameter> .</para>
tree-wide: expose "p"-suffix unref calls in public APIs to make gcc cleanup easy
GLIB has recently started to officially support the gcc cleanup
attribute in its public API, hence let's do the same for our APIs.
With this patch we'll define an xyz_unrefp() call for each public
xyz_unref() call, to make it easy to use inside a
__attribute__((cleanup())) expression. Then, all code is ported over to
make use of this.
The new calls are also documented in the man pages, with examples how to
use them (well, I only added docs where the _unref() call itself already
had docs, and the examples, only cover sd_bus_unrefp() and
sd_event_unrefp()).
This also renames sd_lldp_free() to sd_lldp_unref(), since that's how we
tend to call our destructors these days.
Note that this defines no public macro that wraps gcc's attribute and
makes it easier to use. While I think it's our duty in the library to
make our stuff easy to use, I figure it's not our duty to make gcc's own
features easy to use on its own. Most likely, client code which wants to
make use of this should define its own:
#define _cleanup_(function) __attribute__((cleanup(function)))
Or similar, to make the gcc feature easier to use.
Making this logic public has the benefit that we can remove three header
files whose only purpose was to define these functions internally.
See #2008.
2015-11-27 21:13:45 +03:00
<para > <function > sd_event_source_unref()</function> ,
<function > sd_bus_creds_unrefp()</function> and
<function > sd_bus_creds_ref()</function> execute no operation if
the passed event source object is
<constant > NULL</constant> .</para>
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<para > Note that event source objects stay alive and may be dispatched as long as they have a reference
counter greater than zero. In order to drop a reference of an event source and make sure the associated
event source handler function is not called anymore it is recommended to combine a call of
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<function > sd_event_source_unref()</function> with a prior call to
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<function > sd_event_source_set_enabled()</function> with <constant > SD_EVENT_OFF</constant> or call
<function > sd_event_source_disable_unref()</function> , see below.</para>
<para > <function > sd_event_source_disable_unref()</function> combines a call to
<function > sd_event_source_set_enabled()</function> with <constant > SD_EVENT_OFF</constant> with
<function > sd_event_source_unref()</function> . This ensures that the source is disabled before the local
reference to it is lost. The <parameter > source</parameter> parameter is allowed to be
<constant > NULL</constant> .</para>
2019-05-10 10:54:10 +03:00
<para > <function > sd_event_source_disable_unrefp()</function> is similar to
<function > sd_event_source_unrefp()</function> , but in addition disables the source first. 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> . Note that this function is defined as inline function.</para>
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</refsect1>
<refsect1 >
<title > Return Value</title>
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<para > <function > sd_event_source_unref()</function> and
<function > sd_event_source_disable_unref()</function> always return <constant > NULL</constant> .
<function > sd_event_source_ref()</function> always returns the event source object passed in.</para>
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</refsect1>
<xi:include href= "libsystemd-pkgconfig.xml" />
<refsect1 >
<title > See Also</title>
<para >
<citerefentry > <refentrytitle > sd-event</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry> ,
<citerefentry > <refentrytitle > sd_event_add_io</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry> ,
<citerefentry > <refentrytitle > sd_event_add_time</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry> ,
<citerefentry > <refentrytitle > sd_event_add_signal</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry> ,
2018-10-12 13:09:29 +03:00
<citerefentry > <refentrytitle > sd_event_add_child</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry> ,
<citerefentry > <refentrytitle > sd_event_add_inotify</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry> ,
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<citerefentry > <refentrytitle > sd_event_add_defer</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry> ,
<citerefentry > <refentrytitle > sd_event_source_set_enabled</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry>
</para>
</refsect1>
</refentry>
