sd_bus_slot_set_destroy_callback - Man Page

#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​.

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​.

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​.

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)