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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!--
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SPDX-License-Identifier: LGPL-2.1+
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-->
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<refentry id= "sd_bus_new" xmlns:xi= "http://www.w3.org/2001/XInclude" >
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<refentryinfo >
<title > sd_bus_new</title>
<productname > systemd</productname>
</refentryinfo>
<refmeta >
<refentrytitle > sd_bus_new</refentrytitle>
<manvolnum > 3</manvolnum>
</refmeta>
<refnamediv >
<refname > sd_bus_new</refname>
<refname > sd_bus_ref</refname>
<refname > sd_bus_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_bus_unrefp</refname>
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<refname > sd_bus_close_unref</refname>
<refname > sd_bus_close_unrefp</refname>
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<refname > sd_bus_flush_close_unref</refname>
<refname > sd_bus_flush_close_unrefp</refname>
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<refpurpose > Create a new bus object and create or destroy references to it</refpurpose>
</refnamediv>
<refsynopsisdiv >
<funcsynopsis >
<funcsynopsisinfo > #include < systemd/sd-bus.h> </funcsynopsisinfo>
<funcprototype >
<funcdef > int <function > sd_bus_new</function> </funcdef>
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<paramdef > sd_bus **<parameter > bus</parameter> </paramdef>
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</funcprototype>
<funcprototype >
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<funcdef > sd_bus *<function > sd_bus_ref</function> </funcdef>
<paramdef > sd_bus *<parameter > bus</parameter> </paramdef>
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</funcprototype>
<funcprototype >
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<funcdef > sd_bus *<function > sd_bus_unref</function> </funcdef>
<paramdef > sd_bus *<parameter > bus</parameter> </paramdef>
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</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 >
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<funcdef > sd_bus *<function > sd_bus_close_unref</function> </funcdef>
<paramdef > sd_bus *<parameter > bus</parameter> </paramdef>
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>
2018-10-06 20:15:57 +03:00
<funcprototype >
<funcdef > sd_bus *<function > sd_bus_flush_close_unref</function> </funcdef>
<paramdef > sd_bus *<parameter > bus</parameter> </paramdef>
</funcprototype>
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<funcprototype >
<funcdef > void <function > sd_bus_unrefp</function> </funcdef>
<paramdef > sd_bus **<parameter > busp</parameter> </paramdef>
</funcprototype>
<funcprototype >
<funcdef > void <function > sd_bus_close_unrefp</function> </funcdef>
<paramdef > sd_bus **<parameter > busp</parameter> </paramdef>
</funcprototype>
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<funcprototype >
<funcdef > void <function > sd_bus_flush_close_unrefp</function> </funcdef>
<paramdef > sd_bus **<parameter > busp</parameter> </paramdef>
</funcprototype>
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</funcsynopsis>
</refsynopsisdiv>
<refsect1 >
<title > Description</title>
<para > <function > sd_bus_new()</function> creates a new bus
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object. This object is reference-counted, and will be destroyed
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when all references are gone. Initially, the caller of this
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function owns the sole reference and the bus object will not be
connected to any bus. To connect it to a bus, make sure
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to set an address with
<citerefentry > <refentrytitle > sd_bus_set_address</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry>
or a related call, and then start the connection with
<citerefentry > <refentrytitle > sd_bus_start</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry> .</para>
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<para > In most cases, it is a better idea to invoke
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<citerefentry > <refentrytitle > sd_bus_default_user</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry> ,
<citerefentry > <refentrytitle > sd_bus_default_system</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry>
or related calls instead of the more low-level
<function > sd_bus_new()</function> and
<function > sd_bus_start()</function> . The higher-level calls not
only allocate a bus object but also start the connection to a
well-known bus in a single function invocation.</para>
2014-01-04 09:08:50 +04:00
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_bus_ref()</function> increases the reference
counter of <parameter > bus</parameter> by one.</para>
2014-01-04 09:08:50 +04:00
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_bus_unref()</function> decreases the reference
counter of <parameter > bus</parameter> by one. Once the reference
count has dropped to zero, <parameter > bus</parameter> is destroyed
and cannot be used anymore, so further calls to
<function > sd_bus_ref()</function> or
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<function > sd_bus_unref()</function> are illegal.</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_bus_unrefp()</function> is similar to
<function > sd_bus_unref()</function> but takes a pointer to a
pointer to an <type > sd_bus</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. Use a declaration like the following, in order to
allocate a bus object that is freed automatically as the code
block is left:</para>
<programlisting > {
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__attribute__((cleanup(sd_bus_unrefp)) sd_bus *bus = NULL;
int r;
…
r = sd_bus_default(& bus);
if (r < 0)
fprintf(stderr, "Failed to allocate bus: %s\n", strerror(-r));
…
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
}</programlisting>
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<para > <function > sd_bus_ref()</function> and <function > sd_bus_unref()</function>
execute no operation if the passed in bus object address is
<constant > NULL</constant> . <function > sd_bus_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>
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<para > <function > sd_bus_close_unref()</function> is similar to <function > sd_bus_unref()</function> , but
first executes
<citerefentry > <refentrytitle > sd_bus_close</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry> ,
ensuring that the connection is terminated before the reference to the connection is dropped and possibly
the object freed.</para>
<para > <function > sd_bus_flush_close_unref()</function> is similar to <function > sd_bus_unref()</function> ,
but first executes
<citerefentry > <refentrytitle > sd_bus_flush</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry> as well
as <citerefentry > <refentrytitle > sd_bus_close</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry> ,
ensuring that any pending messages are synchronously flushed out before the reference to the connection
is dropped and possibly the object freed. This call is particularly useful immediately before exiting
from a program as it ensures that any pending outgoing messages are written out, and unprocessed but
queued incoming messages released before the connection is terminated and released.</para>
<para > <function > sd_bus_close_unrefp()</function> is similar to
<function > sd_bus_close_unref()</function> , but may be used in GCC's and LLVM's Clean-up Variable
Attribute, see above. Similarly, <function > sd_bus_flush_close_unrefp()</function> is similar to
<function > sd_bus_flush_close_unref()</function> .</para>
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</refsect1>
<refsect1 >
<title > Return Value</title>
<para > On success, <function > sd_bus_new()</function> returns 0 or a
positive integer. On failure, it returns a negative errno-style
error code.</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_bus_ref()</function> always returns the argument.
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</para>
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<para > <function > sd_bus_unref()</function> and <function > sd_bus_flush_close_unref()</function> always return
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<constant > NULL</constant> .</para>
</refsect1>
<refsect1 >
<title > Errors</title>
<para > Returned errors may indicate the following problems:</para>
<variablelist >
<varlistentry >
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<term > <constant > -ENOMEM</constant> </term>
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<listitem > <para > Memory allocation failed.</para> </listitem>
</varlistentry>
</variablelist>
</refsect1>
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<xi:include href= "libsystemd-pkgconfig.xml" />
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<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_default_user</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry> ,
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<citerefentry > <refentrytitle > sd_bus_default_system</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry> ,
<citerefentry > <refentrytitle > sd_bus_open_user</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry> ,
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<citerefentry > <refentrytitle > sd_bus_open_system</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry> ,
<citerefentry > <refentrytitle > sd_bus_close</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry>
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</para>
</refsect1>
</refentry>
