sd_bus_slot_set_destroy_callback, sd_bus_slot_get_destroy_callback, sd_bus_track_set_destroy_callback, sd_bus_track_get_destroy_callback, sd_bus_destroy_t — Define the callback function for resource cleanup
#include <systemd/sd-bus.h>
typedef int (*sd_bus_destroy_t)( | void *userdata) ; |
int sd_bus_slot_set_destroy_callback( | sd_bus_slot *slot, |
sd_bus_destroy_t callback) ; |
int sd_bus_slot_get_destroy_callback( | sd_bus_slot *slot, |
sd_bus_destroy_t *callback) ; |
int sd_bus_track_set_destroy_callback( | sd_bus_track *track, |
sd_bus_destroy_t callback) ; |
int sd_bus_track_get_destroy_callback( | sd_bus_track *track, |
sd_bus_destroy_t *callback) ; |
sd_bus_slot_set_destroy_callback()
sets callback
as the callback
function to be called right before the bus slot object slot
is deallocated. The
userdata
pointer from the slot object will be passed as the userdata
parameter. This pointer can be set by an argument to the constructor functions, see
sd_bus_add_match(3), or directly,
see sd_bus_slot_set_userdata(3).
This callback function is called even if userdata
is NULL
. Note that
this callback is invoked at a time where the bus slot object itself is already invalidated, and executing
operations or taking new references to the bus slot object is not permissible.
sd_bus_slot_get_destroy_callback()
returns the current callback
for slot
in the callback
parameter.
sd_bus_track_set_destroy_callback()
and
sd_bus_track_get_destroy_callback()
provide equivalent functionality for the
userdata
pointer associated with bus peer tracking objects. For details about bus peer
tracking objects, see
sd_bus_track_new(3).
On success, sd_bus_slot_set_destroy_callback()
and
sd_bus_track_set_destroy_callback()
return 0 or a positive integer. On failure, they
return a negative errno-style error code.
sd_bus_slot_get_destroy_callback()
and
sd_bus_track_get_destroy_callback()
return positive if the destroy callback function
is set, 0 if not. On failure, they return a negative errno-style error code.
Functions described here are available as a shared
library, which can be compiled against and linked to with the
libsystemd
pkg-config(1)
file.
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.
sd_bus_destroy_t()
,
sd_bus_slot_set_destroy_callback()
,
sd_bus_slot_get_destroy_callback()
,
sd_bus_track_set_destroy_callback()
, and
sd_bus_track_get_destroy_callback()
were added in version 239.