| SD_BUS_SLOT_SET_DESTROY_CALLBACK(3) | sd_bus_slot_set_destroy_callback | SD_BUS_SLOT_SET_DESTROY_CALLBACK(3) |
.SH "NAME" 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
.SH "SYNOPSIS"
#include <systemd/sd-bus.h>
.HP 792u typedef void
(*sd_bus_destroy_t)(void *userdata);
.HP 888u int
sd_bus_slot_set_destroy_callback(sd_bus_slot *slot,
sd_bus_destroy_t callback);
.HP 888u int
sd_bus_slot_get_destroy_callback(sd_bus_slot *slot,
sd_bus_destroy_t *callback);
.HP 912u int
sd_bus_track_set_destroy_callback(sd_bus_track *track,
sd_bus_destroy_t callback);
.HP 912u int
sd_bus_track_get_destroy_callback(sd_bus_track *track,
sd_bus_destroy_t *callback);
.SH "DESCRIPTION"
.PP 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.
.PP sd_bus_slot_get_destroy_callback() returns the current callback
for slot in the callback parameter.
.PP 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).
.SH "RETURN VALUE"
.PP 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.
.PP 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.
.SS "Errors"
.PP Returned errors may indicate the following problems:
.PP -EINVAL
The slot or track parameter is NULL.
.RE
.SH "NOTES"
.PP Functions described here are available as a shared library, which can be
compiled against and linked to with the
libsystemd pkg-config(1) file.
.PP 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.
.PP 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.
.SH "HISTORY"
.PP 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.
.SH "SEE ALSO"
.PP systemd(1), sd-bus(3), sd_bus_slot_set_floating(3),
sd_bus_add_match(3), sd_bus_track_new(3),
sd_bus_slot_set_userdata(3), sd_bus_track_set_userdata(3)
| systemd 262.2 |