SD_BUS_SLOT_REF(3)

NAME
sd_bus_slot_ref, sd_bus_slot_unref, sd_bus_slot_unrefp - Create and destroy references to a bus slot object

SYNOPSIS

#include <systemd/sd-bus.h>

sd_bus_slot *sd_bus_slot_ref(sd_bus_slot *slot);

sd_bus_slot *sd_bus_slot_unref(sd_bus_slot *slot);

void sd_bus_slot_unrefp(sd_bus_slot **slotp);

DESCRIPTION

sd_bus_slot_ref() increases the internal reference counter of slot by one.

sd_bus_slot_unref() decreases the internal reference counter of slot by one. Once the reference count has dropped to zero, slot object is destroyed and cannot be used anymore, so further calls to sd_bus_slot_ref() or sd_bus_slot_unref() are illegal.

sd_bus_slot_unrefp() is similar to sd_bus_slot_unref() but takes a pointer to a pointer to an sd_bus_slot object. This call is useful in conjunction with GCC's and LLVM's Clean-up Variable Attribute[1]. See sd_bus_new(3) for an example how to use the cleanup attribute.

sd_bus_slot_ref() and sd_bus_slot_unref() execute no operation if the passed in bus object address is NULL. sd_bus_slot_unrefp() will first dereference its argument, which must not be NULL, and will execute no operation if that is NULL.

RETURN VALUE

sd_bus_slot_ref() always returns the argument.

sd_bus_slot_unref() always returns NULL.

NOTES

Functions described here are available as a shared library, which can be compiled against and linked to with the libsystemd pkg-config(1) file.

All functions listed here are thread-agnostic and only a single thread may operate on a given object at any given time. Different threads may access the same object at different times. Multiple independent objects may be used from different threads in parallel.

The code described here uses getenv(3), which is declared to be not multi-thread-safe. This means that the code calling the functions described here must not call setenv(3) from a parallel thread. It is recommended to only do calls to setenv() from an early phase of the program when no other threads have been started.

HISTORY

sd_bus_slot_ref(), sd_bus_slot_unref(), and sd_bus_slot_unrefp() were added in version 240.

SEE ALSO

systemd(1), sd-bus(3), sd_bus_new(3), sd_bus_message_new(3), sd_bus_call_method_async(3)

NOTES

1.  Clean-up Variable Attribute
    https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html