sd_bus_slot_set_floating, sd_bus_slot_get_floating - Control whether a bus slot
object is "floating"
sd_bus_slot_set_floating() controls whether the specified bus slot object
slot shall be "floating" or not. A floating bus slot object's
lifetime is bound to the lifetime of the bus object it is associated with,
meaning that it remains allocated as long as the bus object itself and is
freed automatically when the bus object is freed. Regular (i.e. non-floating)
bus slot objects keep the bus referenced, hence the bus object remains
allocated at least as long as there remains at least one referenced bus slot
object around. The floating state hence controls the direction of referencing
between the bus object and the bus slot objects: if floating the bus pins the
bus slot, and otherwise the bus slot pins the bus objects. Use
sd_bus_slot_set_floating() to switch between both modes: if the
b parameter is zero, the slot object is considered floating, otherwise
it is made a regular (non-floating) slot object.
Bus slot objects may be allocated with calls such as
sd_bus_add_match(3). If the slot of these functions is
non-NULL the slot object will be of the regular kind (i.e.
non-floating), otherwise it will be created floating. With
sd_bus_slot_set_floating() a bus slot object allocated as regular can
be converted into a floating object and back. This is particularly useful
for creating a bus slot object, then changing parameters of it, and then
turning it into a floating object, whose lifecycle is managed by the bus
sd_bus_slot_get_floating() returns the current floating
state of the specified bus slot object. It returns negative on error, zero
if the bus slot object is a regular (non-floating) object and positive
On success, these functions return 0 or a positive integer. On failure, they
return a negative errno-style error code.
Returned errors may indicate the following problems:
The slot parameter is NULL.
The bus connection has been created in a different
The bus object the specified bus slot object is
associated with has already been freed, and hence no change in the floating
state can be made anymore.
These APIs are implemented as a shared library, which can be compiled and linked
to with the libsystemd pkg-config(1) file.