sd_bus_slot_set_destroy_callback(3) — Linux manual page


SD_BUS...LLBACK(3)  sd_bus_slot_set_destroy_callback  SD_BUS...LLBACK(3)

NAME         top

       sd_bus_track_get_destroy_callback, sd_bus_destroy_t - Define the
       callback function for resource cleanup

SYNOPSIS         top

       #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);

DESCRIPTION         top

       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).

RETURN VALUE         top

       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

       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.

       Returned errors may indicate the following problems:

           The slot or track parameter is NULL.

NOTES         top

       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

HISTORY         top

       sd_bus_destroy_t(), sd_bus_slot_set_destroy_callback(),
       sd_bus_track_set_destroy_callback(), and
       sd_bus_track_get_destroy_callback() were added in version 239.

SEE ALSO         top

       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)

COLOPHON         top

       This page is part of the systemd (systemd system and service
       manager) project.  Information about the project can be found at
       ⟨⟩.  If you have
       a bug report for this manual page, see
       This page was obtained from the project's upstream Git repository
       ⟨⟩ on 2023-12-22.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2023-12-22.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there
       is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to

systemd 255                                           SD_BUS...LLBACK(3)

Pages that refer to this page: sd-bus(3)sd_bus_slot_set_floating(3)sd_bus_slot_set_userdata(3)systemd.directives(7)systemd.index(7)