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'\" t
.TH "SD_BUS_SLOT_REF" "3" "" "systemd 255" "sd_bus_slot_ref"
.\" -----------------------------------------------------------------
.\" * Define some portability stuff
.\" -----------------------------------------------------------------
.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.\" http://bugs.debian.org/507673
.\" http://lists.gnu.org/archive/html/groff/2009-02/msg00013.html
.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.ie \n(.g .ds Aq \(aq
.el .ds Aq '
.\" -----------------------------------------------------------------
.\" * set default formatting
.\" -----------------------------------------------------------------
.\" disable hyphenation
.nh
.\" disable justification (adjust text to left margin only)
.ad l
.\" -----------------------------------------------------------------
.\" * MAIN CONTENT STARTS HERE *
.\" -----------------------------------------------------------------
.SH "NAME"
sd_bus_slot_ref, sd_bus_slot_unref, sd_bus_slot_unrefp \- Create and destroy references to a bus slot object
.SH "SYNOPSIS"
.sp
.ft B
.nf
#include <systemd/sd\-bus\&.h>
.fi
.ft
.HP \w'sd_bus_slot\ *sd_bus_slot_ref('u
.BI "sd_bus_slot *sd_bus_slot_ref(sd_bus_slot\ *" "slot" ");"
.HP \w'sd_bus_slot\ *sd_bus_slot_unref('u
.BI "sd_bus_slot *sd_bus_slot_unref(sd_bus_slot\ *" "slot" ");"
.HP \w'void\ sd_bus_slot_unrefp('u
.BI "void sd_bus_slot_unrefp(sd_bus_slot\ **" "slotp" ");"
.SH "DESCRIPTION"
.PP
\fBsd_bus_slot_ref()\fR
increases the internal reference counter of
\fIslot\fR
by one\&.
.PP
\fBsd_bus_slot_unref()\fR
decreases the internal reference counter of
\fIslot\fR
by one\&. Once the reference count has dropped to zero, slot object is destroyed and cannot be used anymore, so further calls to
\fBsd_bus_slot_ref()\fR
or
\fBsd_bus_slot_unref()\fR
are illegal\&.
.PP
\fBsd_bus_slot_unrefp()\fR
is similar to
\fBsd_bus_slot_unref()\fR
but takes a pointer to a pointer to an
\fBsd_bus_slot\fR
object\&. This call is useful in conjunction with GCC\*(Aqs and LLVM\*(Aqs
\m[blue]\fBClean\-up Variable Attribute\fR\m[]\&\s-2\u[1]\d\s+2\&. See
\fBsd_bus_new\fR(3)
for an example how to use the cleanup attribute\&.
.PP
\fBsd_bus_slot_ref()\fR
and
\fBsd_bus_slot_unref()\fR
execute no operation if the passed in bus object address is
\fBNULL\fR\&.
\fBsd_bus_slot_unrefp()\fR
will first dereference its argument, which must not be
\fBNULL\fR, and will execute no operation if
\fIthat\fR
is
\fBNULL\fR\&.
.SH "RETURN VALUE"
.PP
\fBsd_bus_slot_ref()\fR
always returns the argument\&.
.PP
\fBsd_bus_slot_unref()\fR
always returns
\fBNULL\fR\&.
.SH "NOTES"
.PP
Functions described here are available as a shared library, which can be compiled against and linked to with the
\fBlibsystemd\fR\ \&\fBpkg-config\fR(1)
file\&.
.PP
The code described here uses
\fBgetenv\fR(3), which is declared to be not multi\-thread\-safe\&. This means that the code calling the functions described here must not call
\fBsetenv\fR(3)
from a parallel thread\&. It is recommended to only do calls to
\fBsetenv()\fR
from an early phase of the program when no other threads have been started\&.
.SH "HISTORY"
.PP
\fBsd_bus_slot_ref()\fR,
\fBsd_bus_slot_unref()\fR, and
\fBsd_bus_slot_unrefp()\fR
were added in version 240\&.
.SH "SEE ALSO"
.PP
\fBsystemd\fR(1),
\fBsd-bus\fR(3),
\fBsd_bus_new\fR(3),
\fBsd_bus_message_new\fR(3),
\fBsd_bus_call_method_async\fR(3)
.SH "NOTES"
.IP " 1." 4
Clean-up Variable Attribute
.RS 4
\%https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html
.RE
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